Description:TECHNICAL FIELD
The present disclosure relates to three-dimensional printable earth materials, specifically, the present disclosure relates to three-dimensional printable geopolymer-stabilized earth material, a method of preparing geopolymer-stabilized earth material and a method of three-dimensional printing a construction element.
BACKGROUND
Earthen construction materials are regaining popularity due to their economic advantages and adaptability within a circular economy paradigm. Non-expansive clayey soils, which are generally suitable for earthen constructions, are generated as a result of construction and demolition activities, excavation, tunnelling, and desilting of reservoirs. The ongoing infrastructure and building works in major cities generate large amounts of excavated clayey soil. While using the excavated clayey soil for manufacturing building materials can mitigate greenhouse gas emissions and provide economic benefits, several challenges exist. Traditional earthen constructions are labour-intensive, slow, and suffer from concerns about durability and resilience, particularly under wet exposures and climate change impacts. Additionally, the variability in soil composition across different regions complicates the control of mechanical and durability properties, necessitating adequate stabilization to ensure long-term structural integrity.
Three-dimensional (3D) printing with stabilized earth offers significant potential in addressing these challenges by minimizing labour demands, enabling environmentally friendly construction, and providing greater design flexibility. However, 3D concrete printing, which is widely explored, relies heavily on ordinary Portland cement (OPC), which contributes significantly to global carbon dioxide emissions. Geopolymers, formed through alkali activation of calcium-alumino-silicate minerals, present a promising alternative by significantly reducing embodied carbon emissions in 3D-printed constructions.
Despite ongoing research, existing 3D-printable geopolymer formulations face several limitations. The limitations include rapid hydration leading to a short, printable window, poor selection of stabilizers resulting in low mechanical strength, and inadequate inter-layer bonding. Many geopolymer-based 3D-printed materials exhibit a rapid loss in printability due to high initial setting rates. Additionally, while several studies have examined the role of retarders in 3D-printable geopolymers, their impact on extrusion quality, buildability, and long-term mechanical performance remains insufficiently explored. Furthermore, high-strength formulations often suffer from anisotropy and moisture sensitivity, limiting their applicability in real-world construction scenarios.
Therefore, in light of the foregoing discussion, there exists a need to overcome the aforementioned drawbacks.
SUMMARY
The present disclosure provides a three-dimensional printable geopolymer-stabilized earth material, a method of preparing a three-dimensional printable geopolymer-stabilized earth material and a method for three-dimensional printing a construction element. The present disclosure provides a solution to the technical problem of how to enhance the printability, durability, and structural integrity of three-dimensional (3D) printed geopolymer-stabilized earth materials while maintaining an extended open printing time. The aim of the present disclosure is to provide a solution that overcomes at least partially the problems encountered in the prior art and provides a 3D printable geopolymer-stabilized earth material with controlled retardation, improved extrusion quality, enhanced inter-layer bonding, and superior long-term mechanical performance. The disclosed method ensures optimal thixotropic behaviour, reduced shrinkage, and lower embodied carbon, making it a viable and sustainable alternative for large-scale 3D-printed constructions.
One or more objectives of the present disclosure is achieved by the solutions provided in the enclosed independent claims. Advantageous implementations of the present disclosure are further defined in the dependent claims.
In one aspect, the present disclosure provides a three-dimensional printable geopolymer-stabilized earth material comprising:
a geopolymer binder comprising ground granulated blast furnace slag and fly ash;
fine aggregates comprising crushed rock sand and excavated soil containing kaolinite-rich non-expansive clay;
an alkaline activator; and
a controlled retarding agent comprising sucrose dispersed in the alkaline activator,
wherein the three-dimensional printable geopolymer-stabilized earth material maintains at least 90% flow retention for a minimum of 130 minutes after mixing and achieves a shape retention factor of at least 90% when extruded.
Advantageously, the three-dimensional printable geopolymer-stabilized earth material provides enhanced printability, extrusion quality, and long-term structural integrity. The geopolymer binder, consisting of ground granulated blast furnace slag (GGBS) and fly ash (FA), provides superior mechanical strength, environmental sustainability, and reduced carbon footprint compared to portland cement-based binders. The inclusion of fine aggregates such as crushed rock sand and excavated soil containing kaolinite-rich non-expansive clay significantly enhances thixotropic (i.e., property of a material to become less viscous or more fluid when agitated and to return to its original state when the agitation stops) performance, allowing for better shape stability and inter-layer adhesion during printing. The alkaline activator, specifically an 8 mol/L sodium hydroxide solution, ensures efficient geopolymerization, leading to rapid strength gain and long-term durability. The incorporation of sucrose as a controlled retarding agent, which is dispersed in the alkaline activator, modulates the hydration kinetics of the geopolymer system. The controlled retardation prevents premature setting, thereby extending the open printing time (OPT) to at least 130 minutes while maintaining 90% flow retention. The improved flow retention prevents segregation and nozzle clogging, ensuring smooth and continuous extrusion.
Additionally, the three-dimensional printable geopolymer-stabilized earth material demonstrates a shape retention factor of at least 90%, meaning that the extruded layers maintain their designed geometry without excessive deformation, even at significant build heights. The significant building heights are helpful in large-scale construction applications where precision and consistency in layer stacking directly impact the structural integrity of the printed elements. Furthermore, the combination of kaolinite-rich clay and sucrose leads to reduced shrinkage (up to 13%) and lower water absorption, improving the dimensional stability and moisture resistance of the printed structures.
In another aspect, the present disclosure provides a method of preparing a three-dimensional printable geopolymer-stabilized earth material, comprising
collecting excavated soil content containing non-expansive clay construction and demolition (C&D) waste;
drying the excavated soil and sand to constant mass;
sieving the dried soil to remove particles larger than 4.75 mm;
combining the sieved soil with sand and geopolymer binder to attain a clay-to-binder ratio of 0.225 by mass and aggregate-to-binder ratio of 2:1 by mass;
dissolving a retarding agent in an alkaline activator to form a retarding activator solution;
mixing the geopolymer binder and the retarding activator solution in a solution-to-binder ratio to form the three-dimensional printable geopolymer-stabilized earth material,
wherein the three-dimensional printable geopolymer-stabilized earth material maintains at least 90% flow retention for a minimum of 130 minutes after mixing and achieves a shape retention factor of at least 90% when extruded.
The method achieves all the advantages and technical effects of the three-dimensional printable geopolymer-stabilized earth material of the present disclosure.
In yet another aspect, the present disclosure provides a method of three-dimensional printing of a construction element, comprising:
preparing a 3D printable geopolymer-stabilized earth material comprising geopolymer binder, excavated soil, an alkaline agent, and a retarding admixture;
extruding the 3D printable geopolymer-stabilized earth material through a nozzle at a controlled flow rate;
depositing the 3D printable geopolymer-stabilized earth material in sequential layers with a layer height of 15–18 mm;
maintaining an open printing time of at least 130 minutes; and
building a structure to a height of at least 1.05 meters with a shape retention factor of 90% or more.
Advantageously, by utilizing a 3D printable geopolymer-stabilized earth material, the method ensures sustainable construction practices by incorporating excavated soil and industrial by-products like ground granulated blast furnace slag and fly ash. The sustainable construction reduces the carbon footprint and resource consumption compared to conventional cement-based 3D printing materials. Further, the method uses the controlled extrusion process, where the 3D printable geopolymer-stabilized earth material is deposited through a nozzle at a regulated flow rate, ensuring consistent layer formation with minimal deformation. The precisely maintained layer height of 15–18 mm contributes to better shape stability and inter-layer bonding, thereby improving the overall strength and durability of the printed structure. Additionally, by maintaining the open printing time (OPT) of at least 130 minutes, the method allows for continuous large-scale printing without premature setting, ensuring better workability and reduced material wastage. The ability to build a structure up to 1.05 meters while achieving a shape retention factor of 90% or more is a good advancement, which ensures that the extruded layers retain their designed geometry, preventing slumping or excessive deformation, which is often a challenge in traditional 3D printable materials. The method also leverages accelerated hydration after 30–35 hours, leading to a rapid gain in compressive strength and enhancing the load-bearing capacity of the printed element. Accelerated hydration is particularly beneficial in construction applications requiring early structural stability, reducing the overall construction time. Furthermore, the combination of geopolymer chemistry and controlled retardation using sucrose results in better thixotropic performance, reducing shrinkage and moisture sensitivity. The thixotropic performance ensures that the printed material exhibits high-quality extrusion (without visible discontinuities and cracks) and adequate buildability for stacking up. Better extrudate quality also improves durability and resilience to environmental exposure, making it an ideal solution for sustainable, high-performance 3D-printed construction applications.
It is to be appreciated that all the implementation forms can be combined. All steps that are performed by the various entities described in the present application as well as the functionalities described to be performed by the various entities are intended to mean that the respective entity is adapted to or configured to perform the respective steps and functionalities. It will be appreciated that features of the present disclosure are susceptible to being combined in various combinations without departing from the scope of the present disclosure as defined by the appended claims.
Additional aspects, advantages, features, and objects of the present disclosure would be made apparent from the drawings and the detailed description of the illustrative implementations are construed in conjunction with the appended claims that follow.
BRIEF DESCRIPTION OF THE DRAWINGS
The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the present disclosure is not limited to specific methods and instrumentalities disclosed herein. Moreover, those skilled in the art will understand that the drawings are not to scale. Wherever possible, like elements have been indicated by identical numbers.
Embodiments of the present disclosure will now be described, by way of example only, with reference to the following diagrams wherein:
FIG. 1 is a flowchart illustrating a method of preparing a three-dimensional printable geopolymer-stabilized earth material, in accordance with an embodiment of the present disclosure;
FIG. 2 is a flowchart illustrating a method of 3D printing a construction element, in accordance with an embodiment of the present disclosure;
FIG. 3A depicts an exemplary diagram of a hollow cuboid 3D-printed structure that is prepared using the 3D printable geopolymer-stabilized earth material, in accordance with an embodiment of the present disclosure;
FIG. 3B is a diagram illustrating an L-shaped modular cavity wall system with the enhanced dimensional characteristics, in accordance with an embodiment of the present disclosure;
FIGs. 4A and 4B are graphical representations illustrating the average width and Shape retention factor (SRF) for different compositions under varying testing conditions, in accordance with an embodiment of the present disclosure;
FIG. 5 is a graphical representation illustrating hydration kinetics and cumulative heat evolution of different compositions over 96 hours, in accordance with an embodiment of the present disclosure;
FIG. 6 is a graphical representation illustrating flow retention characteristics of different compositions of geopolymer mixes over an extended duration, in accordance with an embodiment of the present disclosure;
FIG. 7 is a graphical representation illustrating flow retention characteristics of stabilized earth compositions during the critical initial 200-minute period, in accordance with an embodiment of the present disclosure;
FIGs. 8A and 8B are graphical representations illustrating the rheological properties of the different compositions, in accordance with an embodiment of the present disclosure;
FIG. 9A and 9B are graphical representations illustrating the mechanical properties of the material, in accordance with an embodiment of the present disclosure;
FIG. 10 is a graphical representation illustrating the relationship between pore volume distribution and 28-day shrinkage characteristics for mix composition, in accordance with an embodiment of present disclosure;
FIG. 11 is a graphical representation illustrating the sorptivity of mould-cast and 3D-printed samples of similar sizes in three directions, in accordance with an embodiment of the present disclosure;
FIG. 12A is a graphical representation illustrating viscosity recovery characteristics during three-interval thixotropy testing, in accordance with an embodiment of the present disclosure;
FIG. 12B is a graphical representation illustrating the recovery of viscosity, suggesting thixotropy, at different time intervals from the start of the printing window, in accordance with an embodiment of the present disclosure;
FIG. 13A is a graphical representation illustrating wet compressive strength of mould cast and 3D printed samples in L1, L2, and L3 directions at 1-day, in accordance with an embodiment of the present disclosure;
FIG. 13B is a graphical representation illustrating wet compressive strength of mould cast and 3D printed samples in L1, L2, and L3 directions at 3-day, in accordance with an embodiment of the present disclosure;
FIG. 13C is a graphical representation illustrating wet compressive strength of mould cast and 3D printed samples in L1, L2, and L3 directions at 7-day, in accordance with an embodiment of the present disclosure;
FIG. 13D is a graphical representation illustrating the wet compressive strength of mould cast and 3D printed samples in L1, L2, and L3 directions at 28-day, in accordance with an embodiment of the present disclosure;
FIG. 13E is a graphical representation illustrating wet compressive strength of mould cast and 3D printed samples in L1, L2, and L3 directions at 365-day, in accordance with an embodiment of the present disclosure;
FIG. 13F is a graphical representation illustrating a ratio of wet-to-dry compressive strength at 28-day age, in accordance with an embodiment of the present disclosure;
FIG. 14A is a graphical representation illustrating inter-layer bond strength of the different 3D printed mixes in L1 and L2 directions at 28-day age, in accordance with an embodiment of the present disclosure;
FIG. 14B is a graphical representation illustrating total shrinkage behaviour of different geopolymer mixtures over a 60-day period, in accordance with an embodiment of the present disclosure; and
FIG. 14C is a graphical representation illustrating the relationship between inter-layer bond strength and shrinkage at 28-day age for different 3D printable geopolymer-stabilized earth material, in accordance with an embodiment of the present disclosure.
In the accompanying drawings, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non-underlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing.
DETAILED DESCRIPTION OF EMBODIMENTS
The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognize that other embodiments for carrying out or practicing the present disclosure are also possible.
FIG.1 is a flowchart illustrating a method of preparing a three-dimensional printable geopolymer-stabilized earth material, in accordance with an embodiment of the present disclosure. With reference to FIG. 1, there is shown a flowchart illustrating the method 100 for preparing a three dimensional (3D) printable geopolymer-stabilized earth material. The method 100 includes steps 102 to 112. There is provided the method 100 for preparing the 3D geopolymer-stabilized earth material.
At step 102, the method 100 includes collecting excavated soil content containing non-expansive clay construction and demolition (C&D) waste. The excavated soil content refers to the soil obtained from a depth greater than 2 meters below the topsoil, ensuring exclusion from organic matter contamination and consistent material properties. Moreover, the extensive testing of the collected excavated soil content confirms that the excavated soil contains no heavy metals, ensuring the safety of the 3D printable geopolymer-stabilized earth material and validating the environmental compliance used in such construction applications. In an implementation, the excavated soil content has a clay content of 40–45% by weight and a plasticity index of 16%. The collection of the excavated soil content includes identifying suitable construction or demolition sites where lateritic soil is present, as the lateritic soil contains approximately 42.50% clay content, which provides a better texture and viscous properties to the cementitious mixture. The natural viscosity-modifying properties of the clay content enable a 75% reduction in chemical additives compared to the conventional 3D-printing mixtures. Moreover, the excavated soil content contains alumina, silica, and ferric oxides, which provide viscosity and structural stability to the 3D printable geopolymer-stabilized earth material and make the 3D printable geopolymer-stabilized earth material well-suited as a partial replacement for fine aggregates of sand in cement-based construction materials.
Additionally, the excavated soil content is configured to exhibit medium plasticity characteristics typical of loamy clay and is free from heavy metals. In an implementation, the collected excavated soil content samples are properly stored in covered areas to prevent contamination and reduce moisture absorption. 3D printable geopolymer-stabilized earth material with excavated soil content is then tested for shrinkage properties, as unstabilized clay grains are susceptible to volume changes that can affect the dimensional stability of the final 3D-printed structure. The liquid limit and plastic limit of the soil are also characterized because they influence the rheological properties of 3D printing. Moreover, the selection of the excavated soil content at step 102 directly impacts the final compressive strength, moisture sensitivity, and inter-layer bonding capabilities in the printed structure that ensures optimal performance in the 3D-printing process while contributing to reduced environmental impact through decreased consumption of Ordinary Portland Cement (OPC) and natural sand.
At step 104, the method 100 includes drying the excavated soil and sand to constant mass. Initially, the excavated soil and sand are spread in thin layers, for example in some examples not exceeding 50mm in thickness, on ventilated drying trays or clean, non-absorbent surfaces. To maintain consistency, the maximum batch size per drying cycle is controlled. In some implementations, the drying conditions require maintaining a temperature of 105 ± 5°C in a ventilated oven, with relative humidity kept below 30% to enhance moisture evaporation. Continuous air circulation ensures the removal of evaporated moisture, and the material undergoes a minimum drying period of 24 hours. Further, mass measurement is conducted at various intervals, including an initial measurement of the wet material, intermediate measurements at 4-hour intervals, and final measurements at 1-hour intervals.
After drying, the material is stored in sealed containers to prevent reabsorption of atmospheric moisture and is allowed to equilibrate to ambient temperature before further processing. The drying process plays a fundamental role in mix design accuracy by enabling precise water content calculations, ensuring a consistent solution-to-binder ratio, and allowing accurate proportioning of components. The drying process also influences material properties such as workability, rheological behaviour critical for 3D printing, strength development, and shape retention of printed elements. From a quality control perspective, it establishes a baseline for consistent batch production, ensures reproducibility, and facilitates effective quality control measures.
At step 106, the method 100 includes sieving the dried soil (or the dried excavated soil) sieving the dried soil to remove particles larger than 4.75 mm. The dried excavated soil is sieved through a 4.75 mm sieve, which removes larger particles and isolates finer particles below 75 µm. The sieving process provides a finely graded material rich in silt and clay particles, essential for obtaining the intended viscosity and flow properties in the cementitious mixture. Thereby, the fine fraction of the excavated soil content enhances the buildability and workability of the 3D-printable mixture, which is essential for maintaining stable, smooth extrusion in 3D-printing applications.
At step 108, the method 100 includes combining the sieved soil with sand and geopolymer binder to attain a clay-to-binder ratio of 0.225 by mass and an aggregate-to-binder ratio of 2:1 by mass. In an implementation, the geopolymer binder comprises 50–75% ground granulated blast furnace slag (GGBS) and 25–50% fly ash (FA) by weight. In some examples, the geopolymer binder comprises 75% by weight of the geopolymer binder and the FA constituting the remaining 25% by weight. The GGBS contains approximately 38.60% calcium oxide, 16.60% aluminium oxide, and 34.80% silica, with additional minor components. The fly ash component is classified as class F type, containing approximately 60.30% silica, 25.40% aluminium oxide, and 3.23% calcium oxide, with other minor constituents.
The clay-to-binder ratio is calculated based on the clay content in the soil multiplied by the soil mass and divided by the total binder mass. For example, for a standard mixture based on 100g of binder, approximately 53.57g of excavated soil is required with 42% clay content to achieve the target 22.5g of clay. The aggregate-to-binder ratio is achieved by maintaining total aggregate mass at twice the total binder mass, with the aggregate portion comprising 75% manufactured sand (M-sand) and 25% soil. In the standard mixture example, this translates to 200g total aggregate, distributed as 150g M-sand and 50g soil. The combining process is executed under controlled environmental conditions, with material and ambient temperatures maintained in the range from 27 degrees Celsius to 30 degrees Celsius and relative humidity ranging from 65 per cent to 70 per cent. The combining process begins with a pre-mixing stage involving moisture content verification and precise material weighing with ±0.1g accuracy. The dry mixing sequence initiates with GGBS and FA blending for 3 minutes, followed by the gradual addition of sieved soil and the subsequent introduction of M-sand. The entire combining process is conducted at a low-speed ranging from 140 to 145 rpm for 3 minutes to ensure thorough material integration while preventing excessive heat generation.
At step 110, the method 100 includes dissolving a retarding agent in an alkaline activator to form a retarding activator solution. The retarding agent refers to a chemical additive that slows down the reaction rate of a binder system, preventing premature setting. In the embodiment of the present disclosure, sucrose is used as a retarding agent to delay the hydration of the geopolymer binder. In an implementation, the retarding agent is added in amounts of 0.50%, 1.50%, and 1% by weight of the geopolymer binder. For example, when the retarding agent is 0.50% sucrose, the material experiences moderate retardation, extending the open printing time while maintaining relatively fast strength development.
At 1% sucrose, the geopolymer mix achieves an optimal open printing time (~130 minutes) with high shape retention (≥90%), allowing for smooth extrusion and stable layer stacking in 3D printing. The 1 % sucrose dosage provides better thixotropic behaviour, reduced shrinkage, and improved inter-layer bonding. At 1.50% sucrose, the setting time is significantly prolonged, allowing an extended open printing window (~170 minutes). However, excessive retardation at 1.50% sucrose dosage may lead to delayed strength development, requiring longer curing times before the structure achieves full load-bearing capacity. By adjusting the retarding agent within this 0.50%–1.50% range, the formulation can be fine-tuned for different 3D printing conditions, ensuring optimal printability, durability, and structural integrity while preventing premature setting or excessive flow loss. The 3D printable geopolymer-stabilized earth material the material achieves 13% lower shrinkage (better dimensional stability) compared to geopolymer-earth without sucrose and 42% lower shrinkage compared to geopolymer-sand mortar.
In an implementation, the material reduces capillary water absorption by 18 – 32% and detrimental pore volume (corresponding to pore size in the range of 10 nm–100 nm) by 35% compared to geopolymer-stabilized materials without sucrose. The 35% decrease in detrimental pore volume (10–100 nm) results in a denser microstructure, reducing permeability and increasing mechanical strength. The improved pore refinement minimizes shrinkage cracks and enhances the structural integrity of the printed material, making it more suitable for high-performance and climate-resilient construction applications. In an implementation, the material achieves an inter-layer bond strength at least 28% higher than geopolymer-stabilized materials without sucrose. The 28% increase in inter-layer bond strength enhances the cohesion between printed layers, reducing the risk of delamination or weak joints in 3D-printed structures. This results in higher structural integrity and load-bearing capacity, making the material more suitable for large-scale and durable construction applications. The improved bonding also minimizes anisotropic mechanical behaviour, ensuring uniform strength distribution across the printed component. The alkaline activator refers to a high-pH solution used to initiate the geopolymerization process by dissolving alumino-silicate precursors. In accordance with an embodiment, the alkaline activator comprises an 8 mol/L (M) sodium hydroxide solution. The sodium hydroxide solution acts as a high-pH activator that dissolves the alumino-silicate components present in the GGBS and fly ash (FA). The dissolution process releases reactive silicon and aluminium species, which later form a strong geopolymer matrix upon condensation and polymerization. The concentration of 8 mol/L NaOH is optimized to achieve sufficient activation without excessive heat generation or rapid setting, ensuring a controlled reaction suitable for 3D printing applications. When sodium silicate is added alongside NaOH solution, it provides an additional source of reactive silica, which enhances the formation of calcium-alumino-silicate-hydrate and sodium-alumino-silicate-hydrate gels. The gels contribute to higher early-age strength, improved setting control, and reduced permeability in the printed structure. The combined effect of NaOH and sodium silicate leads to better printability, increased mechanical strength, and long-term durability of the 3D-printed geopolymer material.
The retarding activator solution refers to a specially formulated aqueous solution consisting of a retarding agent (for example, sucrose) uniformly dispersed in an alkaline activator (for example, sodium hydroxide solution). The retarding activator solution controls the hydration kinetics of the geopolymer binder by delaying premature setting, thereby extending the open printing time. Additionally, the retarding activator solution enhances the workability and extrusion stability of the 3D printable geopolymer-stabilized earth material by maintaining optimal viscosity and ensuring consistent flow retention throughout the printing process. By regulating geopolymerization, the retarding activator solution prevents rapid stiffening, allowing for smooth extrusion, precise layer stacking, and improved inter-layer bonding. The improved inter-layer bonding ensures uniformity and structural integrity in 3D-printed geopolymer stabilized earth material, contributing to their durability and performance.
At step 112, the method 100 includes mixing the geopolymer binder and the activator solution in a solution-to-binder ratio to form the 3D printable geopolymer-stabilized earth material. In an example, the sodium hydroxide pellets are weighed and dissolved in deionized water. The solution, the sodium hydroxide pellets, and the deionized water are stirred continuously at a controlled temperature (e.g., room temperature or slightly elevated up to 50°C) to ensure complete dissolution.
The solution is then allowed to cool for 16–18 hours to stabilize its composition. The retarding agent, sucrose (0.5%–1.5% by weight of the geopolymer binder), is gradually added to the prepared alkaline activator solution. The mixture is stirred continuously using a mechanical stirrer at 300–600 rpm to promote even dispersion. Proper care is taken to ensure that the sucrose does not precipitate or crystallize within the solution, which may lead to inconsistent retardation effects. The viscosity and pH of the retarding activator solution are monitored to maintain optimal activation conditions. If required, the solution is filtered to remove undissolved particles or impurities that might affect geopolymerization. The final homogeneous retarding activator solution is stored in a sealed container to prevent moisture loss or carbonation before use. The prepared retarding activator solution is gradually introduced into the geopolymer binder and fine aggregates during the mixing process. The mixing speed and duration are controlled to achieve a uniform and printable consistency while ensuring adequate flow retention. Controlling the speed and duration ensures that the hydration reaction proceeds at a controlled rate, allowing a printing window of at least 130 minutes for large-scale 3D printing applications. In an implementation, the solution-to-binder ratio is in the range of 0.67–0.75 to ensure optimal flowability and buildability. A ratio within the range allows for efficient geopolymerization, ensuring proper dissolution of the binder components (GGBS and FA) without excessive dilution, which could weaken the mechanical properties of the printed structure. Additionally, controlling the s/b ratio in this range minimizes shrinkage and drying-induced cracks, leading to improved dimensional stability. The enhanced flowability also reduces nozzle clogging, facilitating continuous printing with uniform layer deposition, which is essential for achieving high shape retention and precision in large-scale 3D construction applications.
The steps 102 to 112 are only illustrative, and other alternatives can also be provided where one or more steps are added, one or more steps are removed, or one or more steps are provided in a different sequence without departing from the scope of the claims herein.
FIG. 2 depicts a flowchart illustrating a method of 3D printing a construction element in accordance with an embodiment of the present disclosure. FIG. 2 is described in conjunction with elements from FIG. 1. With reference to FIG. 2, there is shown the flowchart of the method 200. The method 200 includes steps 202 to 210. There is provided the method 200 for 3D printing the construction element.
At step 202, the method 200 includes preparing a 3D printable geopolymer-stabilized earth material comprising geopolymer binder, excavated soil, an alkaline agent, and a retarding admixture. The process begins with the selection and pre-treatment of excavated soil, ensuring it is free from large aggregates, organic impurities, and excess moisture. The excavated soil is then dried to a controlled moisture level and sieved to achieve a uniform particle size distribution, enhancing its compatibility with the geopolymer binder. Next, the geopolymer binder is prepared by blending suitable aluminosilicate precursors, such as metakaolin or fly ash, with an alkaline agent, typically a sodium hydroxide or sodium silicate solution, to initiate the geopolymerization reaction. The prepared dry components are then gradually mixed with the alkaline solution under controlled conditions to ensure uniform dispersion and activation of the geopolymer network. To regulate the setting time and maintain printability, a retarding admixture, such as a sucrose-based retarding activator, is incorporated into the mix. The admixture delays premature hydration, ensuring an extended open time for extrusion and layer-by-layer deposition. The mixture is then subjected to rheological optimization, where its viscosity, flow behaviour, and workability are adjusted to meet the requirements of 3D printing.
At step 204, the method 200 includes the extrusion process utilizing a three-axis gantry printer equipped with a stainless-steel hopper and screw extruder system. The material is extruded through a circular nozzle with diameter options of 20 mm or 40 mm, with the 40 mm configuration demonstrating superior shape retention characteristics of 90-97% compared to 58-62% for the 20 mm configuration. The extrusion is performed at a controlled flow rate, maintaining an average printing speed of 45 mm/s. The process implements precise control of the stand-off distance, maintained at 16 mm, which is critical for achieving optimal layer adhesion and structural integrity. The extrusion parameters are calibrated to achieve a consistent material output that maintains thixotropic properties, evidenced by complete recovery of viscosity within 40-60 seconds after deposition.
At step 206, the method 200 involves the systematic deposition of the material in sequential layers, with each layer maintaining a controlled height of 15-18 mm. The layer height is precisely regulated through the coordination of extrusion rate, printing speed, and stand-off distance. The deposition process includes the implementation of a layer-time gap matching the material's structural build-up characteristics, allowing adequate strength development between successive layers while maintaining sufficient interlayer adhesion. The process demonstrates capability in achieving layer width consistency within 90-97% of designed dimensions, particularly when utilizing the 40 mm nozzle configuration.
At step 208, the method 200 maintains an open printing time of at least 130 minutes, enabled by the synergistic action of the retarding admixture and clay content. The material maintains flow retention of 99-100% during this period, with static yield stress evolving from initial values of 5-8 kPa to levels supporting stable layer stacking. The extended printing window is achieved while maintaining complete thixotropic recovery and an adequate structural build-up rate of 5.52 Pa/min, enabling continuous printing operations without material property degradation.
At step 210, the method 200 culminates in the construction of structures reaching heights of at least 1.05 meters while maintaining shape retention factors exceeding 90%. This achievement is facilitated by the material's optimized rheological properties, including plastic viscosity maintained between 3.24-3.54 Pa-s throughout the printing duration. The building process demonstrates consistent layer quality and dimensional stability, with shape retention factors of 90-97% maintained throughout the vertical construction. The process enables the creation of complex geometries, including hollow sections and internal bracing patterns, while maintaining structural integrity and dimensional accuracy. The constructed elements exhibit comprehensive performance characteristics, including wet compressive strength of 30-35 MPa, inter-layer bond strength of 3.27-4.01 MPa, and dimensional stability evidenced by shrinkage reduction of 13-23% compared to conventional mixtures.
Experimentally, it has been observed that geopolymer mixtures without sucrose modification (GP-0S-25E) demonstrate significant challenges in printing quality and structural integrity. The printed structures exhibit frequent layer discontinuities and inconsistent material deposition. The defects manifest as visible gaps and irregularities throughout the vertical build, limiting the achievable height and compromising structural stability. The surface characteristics show non-uniform texture and poor layer cohesion, indicating inadequate control over material flow properties during extrusion.
Upon incorporation of 1% sucrose modification (GP-1S-25E), remarkable improvements in printing quality are observed. The printed structures demonstrate exceptional layer regularity with consistent height and width measurements throughout the vertical build. Layer adhesion shows significant enhancement, with no visible tearing or discontinuities. The surface finish exhibits uniform characteristics, reflecting optimized thixotropic behaviour. The improved material properties enable sustained buildability, resulting in structures achieving substantial heights without compromising geometric accuracy.
Further investigations with increased sucrose content (GP-1.5S-25E) reveal certain limitations in structural performance. While the mixture achieves a significant vertical build height of 0.65 meters, noticeable deformations emerge in the upper layers. The observed behaviour suggests that excessive retardation effects at higher sucrose concentrations may impact structural stability. Lower sections maintain acceptable layer consistency, but progressive deterioration in layer quality with increasing height indicates an upper threshold for optimal sucrose content.
Implementation of the optimized mixture (GP-1S-25E) in complex geometric configurations demonstrates remarkable versatility. The L-shaped modular cavity wall system, achieving dimensions of 1.40 meters in perpendicular directions with 0.65-meters height, displays precise dimensional control and consistent material performance. The structure exhibits uniform layer deposition across directional changes, maintaining geometric accuracy throughout. Integration of perpendicular wall sections and cavity spaces demonstrates the successful translation of laboratory-optimized properties to practical construction scale.
The steps 202 to 210 are only illustrative, and other alternatives can also be provided where one or more steps are added, one or more steps are removed, or one or more steps are provided in a different sequence without departing from the scope of the claims herein.
FIG. 3A depicts an exemplary diagram of a hollow cuboid 3D-printed structure that is prepared using the 3D printable geopolymer-stabilized earth material, in accordance with an embodiment of the present disclosure. FIG. 3A is described in conjunction with elements from FIGs. 1 and 2. With reference to FIG. 3A, there is shown diagram 300 that includes a hollow cuboid 3D-printed structure that is layered in nature, whereas a section 302A represents an individual layer of the hollow cuboid 3D-printed structure.
The hollow cuboid 3D-printed structure is developed for buildability investigations of the 3D printable geopolymer-stabilized earth material. The models are specifically designed to assess both vertical build capability and complex geometric printability under varying structural configurations and loading conditions. The hollow cuboid 3D-printed structure 302 has a hollow cuboidal test section having a square footprint of 350 mm × 350 mm. The section incorporates internal cross-bracing elements arranged in an X-pattern configuration, with bracing angles optimized at 45 degrees relative to the outer walls. The bracing elements are designed with a thickness corresponding to two parallel printed filaments, ensuring adequate structural integrity while maintaining efficient material usage. The internal bracing intersects at the geometric centre of the cube, creating four equal triangular sections within the hollow core, each measuring approximately 175 mm along its base. The configuration enables assessment of the material's performance in creating both straight wall sections and angled internal supports in a single continuous printing operation while maintaining shape retention factors exceeding 90%.
FIG. 3B is a diagram illustrating an L-shaped modular cavity wall system with the enhanced dimensional characteristics, in accordance with an embodiment of the present disclosure. FIG. 3B is explained in conjunction with elements from FIGs. 1 to 3A. With reference to FIG. 3B, there is shown a L-shaped modular cavity wall system 300B is designed with enhanced dimensional characteristics to optimize structural performance and constructability. The primary wall segments 302B measure 1.15 meters in length, featuring a 60 mm thickness achieved through three parallel printed filaments, while a layer height of 15–18 mm ensures stability and continuous edge filaments enhance the surface finish. The overall height of 1.15 meters is built through 67 sequential layers, maintaining consistency within ±1 mm through progressive vertical alignment monitoring. The cavity thickness is measured at 0.25 meters centre-to-centre, with an internal clearance of 190 mm, support bridging elements placed at 300 mm vertical intervals, and integrated service channels of 50 mm diameter. An internal truss system reinforces the structure, consisting of primary diagonal members at 45-degree angles, secondary bracing at 30-degree angles, and node reinforcement zones at intersections. The total outer flange length of 1.40 meters includes end returns of 125 mm for added stability, corner reinforcement zones, and modular connection interfaces. The cavity wall system integrates a critical internal truss network with primary load-bearing members of 40 mm thickness, secondary stabilizing members of 20 mm thickness, and node reinforcement zones of 60 mm diameter. Precisely dimensioned cavity spaces accommodate vertical service conduits up to 75 mm diameter, horizontal service runs at 300 mm intervals, designated zones for insulative material insertion, and maintenance access ports at specified locations. Print path optimization features continuous extrusion sequences up to 2.5 meters, optimized corner turning radii of 25 mm, a layer-to-layer overlap of 2 mm, and start-stop transition zones aligned with structural nodes. Strategic reinforcement zones are incorporated at corners, truss intersection nodes, service penetration collars, and modular connection interfaces. The production system utilizes a three-axis gantry printer with advanced specifications. The material feed system includes a stainless-steel hopper with a 60-litre capacity, vibratory assistance operating at 50 Hz, and temperature control maintained at 27±3°C. The extrusion mechanism features a variable-speed screw extruder with a torque capacity of 150 N⋅m and a speed range of 5–120 rpm, supported by a direct drive coupling. The nozzle configuration consists of a primary 50 mm diameter nozzle for bulk deposition and a secondary 20 mm diameter nozzle for detailed features, both made of hardened steel with a quick-change coupling system. Process control ensures precise deposition, with a rate of 45 mm/s within a ±2 mm/s tolerance, a stand-off distance of 16 mm actively monitored, layer height control with ±0.5 mm accuracy, and position accuracy maintained at ±0.1 mm in all axes.
FIGs. 4A and 4B are graphical representations illustrating the average width and Shape retention factor (SRF) for different compositions under varying testing conditions, in accordance with an embodiment of the present disclosure. FIGs. 4A and 4B are described in conjunction with elements from FIGs. 1 to 3B. With reference to FIG. 4A, there is shown a graphical representation 400A, representing the relation between average width and Shape Retention Factor (SRF) for different compositions. The graphical representation 400A includes an X-axis 402A that illustrates the different compositions (or the composition) labelled as GP-0S-25E, GP-0.5S-25E, GP-1S-25E, GP-1.5S-25E, GP-0S-0E, and GP-1S-0E. Throughout the present disclosure, GP-0S-25E. GP-0.5S-25E represents geopolymer-stabilized soil with 0.5% sucrose by weight of geopolymer binder and where the soil is used to replace 25% of manufactured sand (M-sand). GP-1S-25E represents geopolymer-stabilized soil with 1% sucrose by weight of geopolymer binder where the soil is used to replace 25% of M-sand. GP-1.5S-25E represents geopolymer-stabilized soil with 1.5% sucrose by weight of geopolymer binder where the soil is used to replace 25% of M-sand. GP-0S-0E represents a geopolymer-M-sand mix with no soil or sucrose. GP-1S-0E represents geopolymer-M-sand mix with 1% sucrose by weight of geopolymer binder and no soil. Y-axis 404A on the left side represents the average width of extruded layers measured in millimeters (mm), and the right side of the Y-axis 406A represents the Shape Retention Factor (SRF) expressed as a percentage (%).
Specifically, the graphical representation 400A illustrates the relationship between average layer width and SRF for different compositions extruded through a 20mm diameter nozzle. The graphical representation 400A includes a first bar 408A depicting GP-0S-25E, a second bar 410A depicting GP-0.5S-25E, a third bar 412A depicting GP-1S-25E, a fourth bar 414A depicting GP-1.5S-25E, a fifth bar 416A depicting GP-0S-0E, and a sixth bar 418A depicting GP-1S-0E. The bars represent the average layer width measurements for each composition, with error bars indicating measurement uncertainty. The measurements show consistent values around 30-35mm across all soil-containing compositions (GP-0S-25E through GP-1.5S-25E), with a slight increase to approximately 38mm for sand-only compositions (GP-0S-0E and GP-1S-0E). The SRF, indicated by cross markers indicated by a dashed region 424A, demonstrates values between 58-62% across all different compositions. The consistency in SRF values, particularly within the dashed region 424A, indicates stable shape retention characteristics regardless of sucrose content in the different compositions. Notably, the addition of sucrose in varying concentrations (0.5%, 1.0%, and 1.5%) does not significantly impact the layer width or SRF when using the 20mm nozzle. The geopolymer-sand mixtures without soil (GP-0S-0E and GP-1S-0E) exhibit slightly higher average layer widths, approaching 38mm, with marginally lower SRF values.
With reference to FIG. 4B, there is a shown a graphical representation 400B representing the relation between average width and Shape Retention Factor (SRF) for different compositions extruded through a 40mm diameter nozzle. The graphical representation 400B includes an X-axis 402B that illustrates the different compositions, as explained in FIG. 4A. The graphical representation 400B includes a Y-axis 404B on the left side, representing the average width of the extruded layer. On the right side, the Y-axis 406B represents the Shape Retention Factor (SRF) expressed as a percentage (%).
The graphical representation 400B includes a first bar 408B depicting GP-0S-25E, a second bar 410B depicting GP-0.5S-25E, a third bar 412B depicting GP-1S-25E, a fourth bar 414B depicting GP-1.5S-25E, a fifth bar 416B depicting GP-0S-0E, and a sixth bar 418B depicting GP-1S-0E. The bars demonstrate average layer width measurements for each composition. For earth-containing mixtures (i.e., GP-0S-25E, GP-0.5S-25E, GP-1S-25E and GP-1.5S-25E), the average layer width ranges from 40-45mm, as indicated by the height of bars(i.e., the first bar 408B, the second bar 410B, the third bar 412B, and the fourth bar 414B). A notable increase in layer width is observed for geopolymer-sand mixtures (GP-0S-0E and GP-1S-0E), shown by the fifth bar 416B and the sixth bar 418B, reaching approximately 55-60mm. Each bar includes error bars indicating a measurement precision of ±1mm.
Shape retention factors, represented by circular markers 420B plotted against the y-axis 406B, show significantly improved values compared to 20mm nozzle extrusion. The earth-containing mixtures demonstrate SRF values between 90-97%, indicating excellent dimensional stability. In contrast, geopolymer-sand mixtures exhibit lower SRF values of 67-70%, as shown by the markers at the end of the composition range. The data supports the superiority of earth-containing mixtures in maintaining dimensional accuracy during extrusion through larger-diameter nozzles.
Thus, the graphical representation 400A and the graphical representation 400B represent a comparative analysis between normal testing conditions shown in the graphical representation 400A and specific testing conditions shown in the graphical representation 400B, revealing the consistency and reliability of the different compositions labelled as GP-0S-25E, GP-0.5S-25E, GP-1S-25E, GP-1.5S-25E, GP-0S-0E, and GP-1S-0E. GP-0S-25E
FIG. 5 is a graphical representation illustrating hydration kinetics and cumulative heat evolution of different compositions over 96 hours, in accordance with an embodiment of the present disclosure. FIG. 5 is described in conjunction with elements from FIGs.1 to 4B. With reference to FIG 5, there is shown a graphical representation 500 representing hydration kinetics and cumulative heat evolution of different compositions. The x-axis represents the duration of hydration in hours, with two different time scales a primary x-axis 502 having 0-48 hours time scale for detailed early-age behaviour and a secondary x-axis 504 for 0-96 hours for long-term development. The graphical representation 500 includes a primary y-axis 506 representing heat evolution in milli watts per grams (mW/g) of GGBS and FA, ranging from 0 to 4 units. The graphical representation 500 further includes a secondary y-axis 508 showing cumulative heat evolution in joules per gram (J/gram) of GGBS and FA, ranging from 0 to 240 units.
The graphical representation 500 includes a plurality of solid line curves 510 representing heat evolution rates for different mixtures. A “Peak 1” 512 appears within the first hour, indicating the initial dissolution of slag particles. A “Peak 2” 514 appears at different times depending on mixture composition. For GP-0S-25E, “Peak 2” occurs at approximately 2.5 hours, while the addition of sucrose in GP-0.5S-25E, GP-1S-25E, and GP-1.5S-25E delays the “Peak 2” by 2.8 hours, 6.8 hours, and 10.8 hours respectively, demonstrating effective retardation.
Further, the graphical representation 500 includes a plurality of dashed curves 516 representing cumulative heat evolution. The earth-containing mixtures with sucrose (GP-0.5S-25E, GP-1S-25E, GP-1.5S-25E) show higher cumulative heat values (i.e., ranging from 180 joules per gram to 200 joules per gram) compared to GP-0S-25E (i.e., 150 joules per gram). The geopolymer-sand mixtures (GP-0S-0E and GP-1S-0E) demonstrate lower cumulative heat evolution (i.e., 140 Joules per gram), indicating reduced hydration product formation. An acceleration period occurs after the initial retardation, particularly evident in sucrose-containing mixtures. This acceleration corresponds to enhanced hydration product formation, contributing to improved mechanical properties. The rate of heat evolution during this period varies from 1.5-2.0 milliwatts per gram for sucrose-containing mixtures compared to 1.0 milliwatts per gram for control mixtures.
FIG. 6 is a graphical representation illustrating flow retention characteristics of different compositions of geopolymer mixes over an extended duration, in accordance with an embodiment of the present disclosure. FIG 6 is described in conjunction with elements from FIGs 1 to 5. With reference to FIG. 6, there is shown a graphical representation 600 representing flow retention characteristics of different compositions of geopolymer mixes. The graphical representation 600 includes a curve 602 depicting the behaviour of GP-1S-0E, a curve 604 depicting the behaviour of GP-1.5S-25E, a curve 606 depicting the behaviour of GP-1S-0E, a curve 608 depicting the behaviour of GP-1S-0E, a curve 606 depicting behaviour of GP-1S-25E, a curve 608 depicting behaviour of GP-0.5S-25E, a curve 610 depicting behaviour of GP-0S-25E, a curve 612 depicting behaviour of GP-0S-0E. A start point 616 and an endpoint 618 mark the start and end of the extrusion window, respectively, with the endpoint 618 occurring at approximately 500 minutes for GP-1S-0E.
Similarly, start point 620 and endpoint 622 depict the start and end of the extrusion window, respectively, for GP-0S-0E. Multiple performance curves demonstrate distinct behaviours. For example, the curve 610 exhibits rapid flow retention loss, dropping below 90% within 50 minutes. GP-0.5S-25E maintains flow retention above 95% for approximately 85 minutes, while GP-1S-25E sustains acceptable flow characteristics for 140 minutes. Further, GP-1.5S-25E demonstrates the longest retention period of 170 minutes. The baseline mixture GP-0S-0E shows the most rapid decline, reaching 65% flow retention within 30 minutes.
FIG. 7 is a graphical representation illustrating flow retention characteristics of stabilized earth compositions during the critical initial 200-minute period, in accordance with an embodiment of the present disclosure. FIG 7 is described in conjunction with elements from FIGs. 1 to 6. With reference to FIG. 7, there is shown a graphical representation 700 depicting retention characteristics of stabilized earth compositions during the critical initial 200-minute period. The graphical representation 700 maintains similar axes to FIG. 6 but focuses on the stabilized earth compositions. The graphical representation 700 includes a curve 702 depicting the behaviour of GP-1.5S-25E, a curve 704 depicting the behaviour of GP-1S-25E, a curve 706 depicting the behaviour of GP-0.5S-25E and a curve 708 depicting the behaviour of GP-0S-25E.
The graphical representation 700 depicts indicate extrusion windows for each composition. For example, a start point 710 indicates the start of printing, and the start point 710 is the same for all the compositions. Each composition has a different endpoint (represents the point when extrusion ends). GP-1.5S-25E demonstrates superior performance, maintaining flow retention above 98% throughout the monitored period. An endpoint 712 for GP-1.5S-25E depicts an extended duration of high flow retention directly correlated with improved printability and construction capabilities. An endpoint 714 for GP-1S-25E, an endpoint 716 for GP-0.5S-25E and an endpoint 718 for GP-0S-25E are decreasing in pattern, suggesting the flow retention of different compositions depends on the content of the sucrose content. Advantageously, the graphical representation 700 demonstrates several critical technical achievements: firstly, the ability to maintain flow retention above 90% for extended periods through sucrose addition; secondly, the clear correlation between sucrose content and retention duration; and thirdly, the distinct behaviour patterns between soil-containing and non-soil containing mixtures. The discussed characteristics provide fundamental support for the material's capability to achieve extended printing windows while maintaining proper rheological properties.
FIGs. 8A and 8B are graphical representations that illustrating the rheological properties of the different compositions, in accordance with an embodiment of the present disclosure. FIG. 8A is described in conjunction with elements from FIGs. 1 to 7B. With reference to FIG. 8A, there is shown a graphical representation 800A that illustrates the dynamic yield stress over time, providing information regarding resistance of 3D printable geopolymer-stabilized earth material to deformation before flow begins. The duration from the first extrusion is measured in minutes in the abscissa axis. The dynamic yield stress is measured in pascals in the ordinate axis. The graphical representation 800A includes a curve 802A depicting the behaviour of GP-1S-0E, a curve 804A depicting the behaviour of GP-1.5S-25E, a curve 806A depicting behaviour of GP-0.5S-25E, a curve 808A depicting the behaviour of GP-1S-25E, a curve 810A depicting the behaviour of GP-0S-25E.
The materials incorporating sucrose additives (GP-0.5S-25E, GP-1.5S-25E, GP-1S-0E) exhibit relatively stable yield stress, demonstrating good thixotropic behaviour and shape retention, essential for layer-by-layer deposition without excessive deformation. However, a sharp increase in yield stress for GP-0.5S-25E after 50 minutes indicates accelerated stiffening, possibly due to hydration reactions or drying, which can reduce workability over time. Additionally, GP-0S-0E exhibits lower initial yield stress, implying reduced structuration and viscosity, likely due to the absence of stabilizing agents such as sucrose or extrusion modifications.
FIG. 8B is described in conjunction with elements from FIGs. 1 to 8A. With reference to FIG. 8B, there is shown a graphical representation 800B illustrating the resistance of material to flow under applied stress. The different compositions are expressed in arbitrary units in the abscissa axis. The plastic viscosity is measured in Pascal second in the ordinate axis. The graphical representation 800B includes a plurality of bars depicting various changes in plastic viscosity for different intervals of time (10 minutes, 27 minutes, 44 minutes, and 61 minutes) for GP-0S-25E, GP-0.5S-25E, GP-1S-25E, GP-1.5S-25E, GP-0S-0E and GP-0S-0E.
The graphical representation includes a section 802B depicting a detailed view of viscosity changes over time (10 minutes, 27 minutes, 44 minutes, and 61 minutes) for GP-0S-25E, GP-0.5S-25E, and GP-1.5S-25E. The results indicate that viscosity increases over time for most samples, reflecting gradual structuration as the geopolymer reaction progresses, leading to a more rigid structure. Maintaining an optimal viscosity range is essential for long-duration 3D printing, as excessive thickening can cause premature stiffening and print failures.
FIG. 9A and 9B are graphical representations illustrating the mechanical properties of the material, in accordance with the embodiment of the present disclosure. FIG. 9A is described in conjunction with elements from FIGs. 1 to 8B. With the reference to FIG. 9A, there is shown the graphical representation 900A depicting the evolution of static yield stress over time for various mixtures. Time from the addition of retarding activator solution is expressed in minutes in the abscissa axis. The static yield stress is measured in kilo Pascal in an ordinate axis. The graphical representation 900A includes a curve 902A representing GP-0S-0E, a curve 904A representing GP-1S-0E, a curve 906A representing GP-0S-25E, a curve 908A representing GP-0.5S-25E, a curve 910A representing GP-1S-25E, and a curve 912A representing GP-1.5S-25E. The graphical representation 900A includes a printing window 914A and a region 916A, indicating an inadequate stress yield.
The baseline mixture GP-0S-25E demonstrates rapid initial development of static yield stress, reaching approximately 22 kPa within the first 20 minutes. This is followed by a sharp decline and subsequent increase, indicating rapid structural development that may limit practical printing time. GP-0.5S-25E exhibits a more gradual increase in static yield stress, reaching 34 kPa around 100 minutes. GP-1S-25E demonstrates controlled development, achieving 39 kPa at approximately 200 minutes. GP-1.5S-25E shows the most gradual increase, maintaining workable yield stress values for an extended period. The geopolymer-sand mixtures GP-0S-0E and GP-1S-0E exhibit notably different behaviour, with GP-1S-0E showing delayed stress development starting around 400 minutes. The rate of static yield stress development while maintaining adequate structural strength for layer stacking. The earth-containing mixtures show superior performance in terms of controlled strength development compared to sand-only mixtures, indicating synergistic effects between sucrose and clay content in regulating structural development.
FIG. 9B is described in conjunction with elements from FIGs. 1 to 9A. With the reference to FIG. 9B, there is shown the graphical representation 900B depicting the relationship between initial yield stress and structural build-up rate for different compositions. The graphical representation 900B includes the plurality of bars, i.e., a first bar 902B representing GP-0S-0E, a second bar 904B representing GP-1S-0E, a third bar 906B representing GP-0S-25E, a fourth bar 908B representing GP-0.5S-25E, a fifth bar 910B representing GP-1S-25E, and a sixth bar 912B representing GP-1.5S-25E.
The plurality of the bars illustrates the initial yield stress values for various geopolymer compositions, revealing a systematic increase with the addition of sucrose and earth content. Among the tested formulations, the geopolymer-sand mixture GP-0S-0E exhibits the lowest initial yield stress, while earth-containing mixtures demonstrate progressively higher values, indicating improved structural integrity. The incorporation of sucrose in GP-0.5S-25E through GP-1.5S-25E results in initial yield stress values ranging from 1.5 to 2.0 kPa, which enhances early-stage mechanical stability without compromising workability. Furthermore, the structural build-up rate, represented by circular markers, exhibits an inverse relationship with sucrose content in earth-containing mixtures. The GP-0S-25E formulation shows the highest build-up rate at approximately 7.61 Pa/min, while the addition of sucrose progressively reduces this rate to 7.15 pascals per minute, 5.52 pascal per minute, and 2.76 pascals per minute for sucrose concentrations of 0.5%, 1.0%, and 1.5%, respectively. The controlled decrease in structural build-up rate extends the printing window while ensuring gradual strength development, which is critical for achieving smooth and defect-free layer stacking. The graphical representation 900B effectively highlights the dual benefits of sucrose addition, namely maintaining sufficient initial yield stress for layer stability while delaying structural stiffening to facilitate prolonged print durations. The combined properties make sucrose-modified formulations particularly suitable for large-scale additive manufacturing applications, where extended workability is essential for maintaining precision and structural reliability.
FIG. 10 is a graphical representation illustrating the relationship between pore volume distribution and 28-day shrinkage characteristics for mix composition, in accordance with an embodiment of the present disclosure. FIG. 10 is explained in conjunction with elements from FIGs. 1 to 9B. With reference to FIG. 10, there is shown a graphical representation 1000 relationship between pore volume distribution and 28-day shrinkage characteristics. X-axis illustrates the different compositions (or the composition) labelled as GP-0S-0E, GP-1S-0E, GP-0S-25E, GP-0.5S-25E, GP-1S-25E, and GP-1.5S-25E. The Y-axis on the left side represents the pore volume expressed in cubic centimetres per gram (X 10^ (-3)), and the right side of the Y-axis represents the 28-day shrinkage (micro-strain).
The graphical representation 1000 includes a bar 1002 depicting composition GP-0S-0E with pore size less than 10 nanometer , a bar 1004 depicting composition GP-0S-0E with pore more size between 10 to 100 nanometer, a bar 1006 depicting composition GP-1S-0E with pore size less than 10 nanometer , a bar 1008 depicting composition GP-1S-0E with pore more size between 10 to 100 nanometer, a bar 1010 depicting composition GP-0S-25E with pore size less than 10 nanometer, a bar 1012 depicting composition GP-0S-25E with pore more size between 10 to 100 nanometer, a bar 1014 depicting composition GP-0.5S-25E with pore size less than 10 nanometer , a bar 1016 depicting composition GP-0.5S-25E with pore more size between 10 to 100 nanometer, a bar 1018 depicting composition GP-1S-25E with pore size less than 10 nanometer , a bar 1020 depicting composition GP-1S-25E with pore more size between 10 to 100 nanometer, a bar 1022 depicting composition GP-1.5S-25E with pore size less than 10 nanometer , and a bar 1024 depicting composition GP-1.5S-25E with pore more size between 10 to 100 nanometer.
The pore volume distribution of the baseline mixture GP-0S-0E reveals a small fraction of less than 10 nm pores and a dominant volume of 10-100 nm pores, approximately 135×10⁻³ cc/g, indicating a relatively coarse internal structure. The incorporation of sucrose in GP-1S-0E results in a higher proportion of less than 10 nm pores and a reduction in 10-100 nm pores, demonstrating effective pore refinement. In earth-containing mixtures, GP-0S-25E presents a moderate distribution of both pore size ranges, serving as a baseline for further modifications. The addition of sucrose at varying concentrations in GP-0.5S-25E through GP-1.5S-25E leads to systematic changes, with GP-0.5S-25E exhibiting an increase in less than 10 nm pores and a reduction in pores with size ranging from 10-100 nm. The GP-1S-25E formulation demonstrates optimal refinement, while GP-1.5S-25E maintains similar improvements. Notably, sucrose-modified earth mixtures show a 35% reduction in detrimental pore volume compared to GP-0S-25E, alongside a 45% increase in beneficial pores with size of less than 10 nm, directly correlating with reduced shrinkage values, as indicated by circular markers. The progressive enhancement in dimensional stability with increasing sucrose content highlights the synergistic effect of sucrose and earth content, leading to superior pore refinement compared to sand-only mixtures, reduced total porosity in critical size ranges, and an improved relationship between pore structure and shrinkage behaviour. The optimal balance of properties is achieved at 1.0-1.5% sucrose content, ensuring enhanced durability and structural integrity in geopolymer formulations.
FIG. 11 is a graphical representation illustrating the sorptivity of mould-cast and 3D-printed samples of similar sizes in three directions, in accordance with an embodiment of the present disclosure. FIG. 11 is explained in conjunction with elements from FIGs. 1 to 10. With reference to FIG. 11, there is shown a graphical representation 1100 illustrating water absorption characteristics of the mould-cast and 3D printed samples of similar sizes in three directions. X-axis illustrates the different compositions (or the composition) labelled as GP-0S-0E, GP-1S-0E, GP-0S-25E, GP-0.5S-25E, GP-1S-25E, and GP-1.5S-25E. The Y-axis represents sorptivity expressed in millimetres per square root minutes.
The graphical representation 1100 includes a first cluster 1102 representing GP-0S-0E, a second cluster 1104 representing GP-1S-0E, a third cluster 1106 representing GP-0S-25E, a fourth cluster 1108 representing GP-0.5S-25E, a fifth cluster 1110 representing GP-1S-25E, and a sixth cluster 1112B representing GP-1.5S-25E. Each cluster (i.e. the first cluster 1102, second cluster 1104, third cluster 1106, fourth cluster 1108, the fifth cluster 1110 and the sixth cluster 1112) the sorptivity of mould-cast cubes and sorptivity of 3D-printed cubes in L1, L2 and L3 directions respectively.
The baseline mixture GP-0S-0E exhibits significantly higher sorptivity in the L2-direction, reaching approximately 0.77 mm per √min, marking a 156% increase (p < 0.05) compared to mould-cast samples. The “p” refers to the probability value. The addition of sucrose in GP-1S-0E effectively reduces sorptivity, with the most notable decrease observed in the L3 direction, where a 60% reduction (p < 0.05) is recorded. In earth-containing mixtures, GP-0S-25E maintains relatively uniform sorptivity across directions, ranging from 0.35 to 0.50 mm/√min. A progressive reduction is seen with increasing sucrose content, as GP-0.5S-25E lowers sorptivity to 0.28–0.36 mm/√min, while GP-1S-25E achieves a 34% reduction (p < 0.05) compared to GP-0S-25E. The most substantial improvement is observed in GP-1.5S-25E, showing a 44% reduction (p < 0.05). Further, there is direction-dependent sorptivity reduction, with decreases of 15–25% in the L1 direction, 30–40% in the L2 direction, and 35–45% in the L3-direction. All reported reductions are statistically significant, with p-values below 0.05, and error bars confirm measurement precision. The consistent trends across multiple samples indicate that optimal sucrose content lies between 1.0% and 1.5%, providing reduced directional variation in earth-containing mixtures and significantly enhancing water penetration resistance.
FIG. 12A is a graphical representation illustrating viscosity recovery characteristics during three-interval thixotropy testing, in accordance with an embodiment of the present disclosure. FIG. 12A is explained in conjunction with elements from FIGs. 1 to 11. With reference to FIG. 12A, there is shown a graphical representation 1200A representing viscosity evolution during three-interval thixotropy testing (3iTT). The step time is measured in seconds (s) on the abscissa axis. The viscosity is measured in millipascal-seconds (mPa-s) on an ordinate axis. The graphical representation 1200A includes a first curve 1202A representing GP-0S-0E, a second curve 1204A representing GP-1S-0E, a third curve 1206A representing GP-0S-25E, a fourth curve 1208A representing GP-0.5S-25E; a fifth curve 1210A representing GP-1S-25E, and a sixth curve 1212A representing GP-1.5S-25E.
Further, the graphical representation 1200A includes a first-time interval 1214A representing the 3D printable geopolymer-stabilized earth material in the hopper during floc formation, a second time interval 1216A representing the 3D printable geopolymer-stabilized earth material in the extruder during floc breakage, and a third time interval 1218A representing the 3D printable geopolymer-stabilized earth material deposited on the print bed during floc regrowth. The first-time interval 1214A, the second-time interval 1216A, and the third-time interval 1218A in the graphical representation 1200A represent distinct phases of the behaviour of the 3D printable geopolymer-stabilized earth material during the 3D printing process. The first-time interval 1214A (occurring from 0 to 90 seconds) demonstrates the viscosity evolution of the geopolymer-stabilized earth material within the hopper. During the first time interval 1214A, the 3D printable geopolymer-stabilized earth material undergoes floc formation, characterized by clay particle agglomeration, resulting in viscosity increase from initial values of 1000-2000 mPa-s to stabilized values of 7000-8000 mPa-s for earth-containing mixtures (i.e., GP-0S-25E, GP-0.5S-25E, GP-1S-25E and GP-1.5S-25E). Subsequently, the second time interval 1216A (occurring from 90 to 180 seconds) represents the behaviour of the 3D printable geopolymer-stabilized earth material during extrusion, where applied shear forces cause systematic breakdown of the formed floc structures. The second time interval 1216A exhibits consistent viscosity reduction to 500-1000 mPa-s across all mixture compositions, indicating uniform response to applied shear force. The third time interval 1218A (occurring from 180 to 270 seconds), captures the response of the 3D printable geopolymer-stabilized earth material after deposition on the printing bed. During the third time interval 1218A, the geopolymer-stabilized earth material demonstrates structural rebuilding through floc reformation, with earth-containing mixtures achieving complete viscosity recovery to their original values of 7000-8000 mPa-s, while non-earth mixtures show partial recovery to 5000-6000 mPa-s.
The graphical representation 1200A further includes a first complete recovery indicator 1220A indicating complete recovery of GP-0.5S-25E, a second complete recovery indicator 1222A, indicating complete recovery of GP-1.5S-25E, a third complete recovery indicator 1224A indicating complete recovery of GP-0S-25E, and an incomplete recovery indicator 1226A indicating incomplete recovery of GP-0S-0E. The complete recovery indicators and incomplete recovery indicator 1226 in the graphical representation 1200A demonstrate the ability of the 3D printable geopolymer-stabilized earth material to rebuild the internal structure after experiencing shear forces. The complete recovery refers to the capability of the geopolymer-stabilized earth material to return to the original viscosity values during the third time interval 1218A, indicating full restoration of floc structures after extrusion. In contrast, incomplete recovery represents the inability of the 3D printable geopolymer-stabilized earth material to achieve the initial viscosity values, instead reaching only partial restoration of viscosity values during the third time interval 1218A.
The first complete recovery indicator 1220A indicates the behaviour of fourth curve 1208A during the three-interval thixotropy testing. During the first time interval 1214A (i.e. from 0 to 90 seconds), the fourth curve 1208A exhibits a viscosity increase from approximately 1600 mPa-s to 5500 mPa-s through floc formation. Following the systematic breakdown of the floc structure in the second time interval 1216A (i.e. from 90 to 180 seconds) where the viscosity reduces to approximately in the range between 500-1000 mPa-s, the mixture achieves complete structural rebuilding in the third time interval 1218A (i.e. from 180 to 270 seconds), returning to the original viscosity value approximately ranging from 7000-8000 mPa-s.
The second complete recovery indicator 1222A illustrates the response of the sixth curve 1212 throughout three-interval thixotropy testing. The sixth curve 1212A representing GP-1.5S-25E demonstrates similar floc formation characteristics as compared to the fourth curve 1208A during the first time interval 1214A, with viscosity approximately ranging from 1300 mPa-s to 6000 mPa-s. After experiencing viscosity reduction approximately ranging from 500-1000 mPa-s in the second time interval 1216A due to applied shear forces, the sixth curve 1212A exhibits complete recovery through floc reformation in the third time interval 1218A, returning to viscosity values of approximately 6000 mPa-s.
The third complete recovery indicator 1224A represents the behaviour of the third curve 1206A during the three-interval thixotropy testing. The third curve 1206A represents GP-0S-25E and undergoes clay particle agglomeration in the first-time interval 1214A, achieving viscosity increase from approximately 2200 mPa-s to 8200 mPa-s. Following the systematic breakdown of floc structures of GP-0S-25E in the second time interval 1216A approximately ranging from 500-1000 mPa-s, GP-0S-25E demonstrates complete structural rebuilding in the third time interval 1218A, recovering to the original viscosity of approximately ranging from 8000-9000 mPa-s.
The incomplete recovery indicator 1226A characterizes the behaviour of the first curve 1202A, representing GP-0S-0E. During the first time interval 1214A, the first curve 1202A shows viscosity development approximately ranging from 1000 mPa-s to 8000 mPa-s. After experiencing viscosity reduction in the second time interval 1216A approximately ranging from 500-1000 mPa-s, the first curve 1202A exhibits only partial recovery in the third time interval 1218A, achieving viscosity values approximately in the range between 2000-6000 mPa-s, demonstrating inferior structural rebuilding compared to the earth-containing mixtures.
FIG. 12B is a graphical representation illustrating the recovery of viscosity, suggesting thixotropy, at different time intervals from the start of the printing window, in accordance with an embodiment of the present disclosure. FIG. 12B is explained in conjunction with elements from FIG. 1 to 12A. With reference to FIG. 12B, there is shown a graphical representation 1200B representing recovery of viscosity, suggesting thixotropy, at different time intervals from the start of the printing window. The abscissa axis represents the several 3D printable geopolymer-stabilized earth materials. The recovery of viscosity is a dimensionless quantity and is indicated by (RV) with a value of 1.0 indicating complete recovery on the ordinate axis. The recovery of viscosity is the process by which a material regains its viscosity after a period of shear stress or agitation. The recovery of viscosity is a ratio between viscosity of a material after a certain process (like shearing or heating) and the original viscosity of the material before the certain process. The graphical representation 1200B includes a first cluster 1202B representing GP-0S-25E, a second cluster 1204B representing GP-0.5S-25E, a third cluster 1206B representing GP-1S-25E, a fourth cluster 1208B representing GP-1.5S-25E, a bar 1210B representing GP-0S-0E, and a fifth cluster 1212B representing GP-1S-0E. Each cluster (i.e. the first cluster 1202B, second cluster 1204B, third cluster 1206B, fourth cluster 1208B, and the fifth cluster 1212B) includes four plots representing recovery of viscosity with reference to a time interval. The four plots have different time intervals of 10 minutes, 25 minutes, 40 minutes, and 55 minutes as shown in each cluster from left to right in the FIG. 12B.
The first cluster 1202B exhibits recovery of viscosity measurements at four different time intervals (i.e. 10, 25, 40, and 55 minutes). The values of recovery of viscosity consistently approach towards 1.0 across all time intervals, demonstrating suitable thixotropic behaviour and structural rebuilding capabilities in first cluster 1202B representing GP-0S-25E. The thixotropic behaviour and structural rebuilding capabilities indicate stable performance throughout the printing window without performance degradation. The earth content in the GP-0S-25E enables rapid floc reformation after shearing, demonstrated by consistent recovery at time intervals of 10 minutes and sustained performance up to 55 minutes, indicating stable clay particle network formation without retardation effects. The second cluster 1204B exhibits highly consistent recovery patterns across all time intervals. The recovery of viscosity values maintains proximity to 1.0, indicating robust thixotropic characteristics and sustained structural reformation capabilities. The 0.5% sucrose addition improves the floc stability while maintaining rapid recovery characteristics, evidenced by improved initial recovery at 10 minutes compared to GP-0S-25E, with sustained performance through 55 minutes due to controlled retardation of geopolymer reaction.
The third cluster 1206B exhibits uniform recovery of viscosity values near 1.0 across all time intervals. The 1% sucrose content in the GP-1S-25E achieves suitable balance between floc formation and geopolymer reaction kinetics, enabling consistent structural rebuilding within time interval of 10 minutes while maintaining stability through extended printing windows up to 55 minutes without variation in recovery behaviour. The fourth cluster 1208B shows recovery of viscosity values consistently approaching 1.0 across all time intervals. The increased sucrose content maintains controlled geopolymer reaction rates without compromising clay-floc formation, evidenced by consistent recovery behaviour across all time intervals. GP-1.5S-25E retains the structural rebuilding capability even at 55 minutes, indicating effective retardation without sacrificing thixotropic performance. The bar 1210B exhibits a significantly lower recovery of viscosity value of approximately 0.74, indicating a 26% loss in structural rebuilding capability. The absence of clay particles in GP-0S-0E results in the inability to form stable floc networks, leading to permanent structural breakdown after shearing despite geopolymer network formation.
The fifth cluster 1212B shows a declining recovery of viscosity values from 1.15 at 10 minutes to 0.85 at 55 minutes. The initial higher recovery of viscosity indicates temporary structural formation through geopolymer networks, but the absence of clay particles in GP-1S-0E leads to progressive network breakdown, resulting in 15% viscosity loss by 55 minutes despite sucrose-induced retardation, demonstrating the vital role of clay-sucrose synergy in maintaining structural stability.
FIG. 13A is a graphical representation illustrating wet compressive strength of mould cast and 3D printed samples in L1, L2, and L3 directions at 1-day, in accordance with an embodiment of the present disclosure. FIG. 13A is explained in conjunction with elements from FIGs. 1 to 12B. With reference to FIG. 13A, there is shown a graphical representation 1300A representing wet compressive strength of mould cast and 3D printed samples in L1, L2, and L3 directions at 1-day. The graphical representation 1300A includes a first cluster 1302A representing GP-0S-0E, a second cluster 1304A representing GP-1S-0E, a third cluster 1306A representing GP-0S-25E, a fourth cluster 1308A representing GP-0.5S-25E, a fifth cluster 1310A representing GP-1S-25E, and a sixth cluster 1312A representing GP-1.5S-25E. Each cluster (i.e. the first cluster 1302A, second cluster 1304A, third cluster 1306A, fourth cluster 1308A, fifth cluster 1310A and the sixth cluster 1312A) includes four plots representing mould cast, loaded along a first direction 1318A (L1-direction), a second direction 1316A (L2-direction), and a third direction 1314A (L3-direction) as shown in each cluster from left to right in FIG. 13A. The first direction 1318A, second direction 1316A, and third direction 1314A in the graphical representation 1300A represents distinct loading configurations for compressive strength testing. Mould cast samples are conventionally prepared specimens serving as reference measurements. The first direction 1318A represents loading parallel to the printing direction, the second direction 1316A indicates loading directly on the printed layers, and the third direction 1314A demonstrates loading perpendicular to the printing direction, enabling comprehensive assessment of material anisotropy. The direction of nozzle movement 1320A demonstrates the relationship between printing orientation and loading directions. The abscissa axis represents the several 3D printable geopolymer-stabilized earth materials. The ordinate axis represents the 1-day compressive strength measured in megapascal (MPa).
The first cluster 1302A exhibits compressive strengths of approximately ranging between 7 to 10 MPa across all testing directions (i.e. the first direction 1318A, second direction 1316A, and the third direction 1314A) at 1-day age. The mould cast sample shows marginally higher strength compared to printed specimens loaded along the first direction 1318A, second direction 1316A, and the third direction 1314A. The printed samples demonstrate consistent performance across the first direction 1318A, second direction 1316A, and the third direction 1314A, indicating uniform structural development without directional bias in the absence of earth content. The second cluster 1304A, corresponding to GP-1S-0E, shows increased strength values reaching approximately in the range between 14 to 19 MPa. The mould cast samples achieve higher strength compared to printed specimens, with the first direction 1318A showing superior performance among second direction 1316A, and the third direction 1314A. The sucrose addition enhances early-age strength development through controlled geopolymer reaction kinetics, resulting in 40-90% strength improvement compared to GP-0S-0E.
The third cluster 1306A, representing, demonstrates compressive strength values approximately ranging between 9 to 14 MPa. The earth content influences strength development in GP-0S-25E, with mould-cast samples showing higher compressive strength values than printed specimens. The presence of clay particles contributes to structured network formation, though without sucrose modification, the strength development in GP-0S-25E remains moderate. The fourth cluster 1308A exhibits compressive strength values approximately ranging from 10 to18 MPa. The synergistic effect of earth content and sucrose in GP-0.5S-25E enables enhanced strength development, particularly evident in mould cast samples. The printed specimens maintain consistent strength across directions, indicating uniform structural development through controlled clay-geopolymer interaction.
The fifth cluster 1310A shows compressive strength development approximately ranging between 11to 14 MPa. The 1% sucrose content in GP-1S-25E enables balanced reaction kinetics and clay network formation, resulting in uniform strength distribution across all testing directions. The reduced variation between mould cast and printed specimens indicates improved material homogeneity. The sixth cluster 1312A demonstrates compressive strength values approximately ranging between 9 to 18 MPa. The higher sucrose content modifies early-age reaction kinetics, resulting in varied strength development across different loading directions. The mould cast samples exhibit notably higher strength compared to printed specimens, indicating the influence of printing process on structural development at increased sucrose concentrations.
FIG. 13B is a graphical representation illustrating wet compressive strength of mould cast and 3D printed samples in L1, L2, and L3 directions at 3-day, in accordance with an embodiment of the present disclosure. FIG. 13B is explained in conjunction with elements from FIGs. 1 to 13A. With reference to FIG. 13B, there is shown a graphical representation 1300B representing wet compressive strength of mould cast and 3D printed samples in L1, L2, and L3 directions at 3-day. The graphical representation 1300B includes a first cluster 1302B representing GP-0S-0E, a second cluster 1304B representing GP-1S-0E, a third cluster 1306B representing GP-0S-25E, a fourth cluster 1308B representing GP-0.5S-25E, a fifth cluster 1310B representing GP-1S-25E, and a sixth cluster 1312B representing GP-1.5S-25E. Each cluster (i.e. the first cluster 1302B, second cluster 1304B, third cluster 1306B, fourth cluster 1308B, fifth cluster 1310B and the sixth cluster 1312B) includes four plots representing mould cast, loaded along a first direction 1318A, a second direction 1316A, and a third direction 1314A as shown in each cluster from left to right in FIG. 13B. The first direction 1318A, second direction 1316A, and third direction 1314A in the graphical representation 1300B represent distinct loading configurations for compressive strength testing. The graphical representation 1300B further includes a reference line at approximately between 14 to18 MPa, indicating a minimum strength threshold, demonstrating that all sucrose-modified mixtures achieve significantly higher strength values across all testing directions at 3-day age. The direction of nozzle movement 1320A demonstrates the relationship between printing orientation and loading directions. The abscissa axis represents several 3D printable geopolymer-stabilized earth materials. The ordinate axis represents the 3-day compressive strength measured in megapascal (MPa).
The first cluster 1302B demonstrates uniform strength distribution, approximately ranging from 14 to 18 MPa across all testing directions, with mould-cast samples showing marginally higher values. The absence of earth content in GP-0S-0E results in relatively isotropic behaviour but limited strength development at early age. The second cluster 1304B exhibits significantly enhanced strength development, reaching approximately ranging from 25-30 MPa across different testing directions. The first direction 1318A shows highest strength (approximately 29 MPa), followed by the second direction 1316A (approximately 27 MPa) and the third direction 1314A (approximately 24 MPa). The addition of sucrose in GP-1S-0Eenables rapid early-age strength development through controlled geopolymer reaction kinetics.
The third cluster 1306B shows strength values approximately ranging between 12-22 MPa, with notable variation in different testing directions. Mould-cast specimens achieve approximately 22 MPa, while printed samples in different testing directions show reduced strength in all testing directions, indicating the influence of printing process on structural development in earth-containing mixtures without sucrose modification. The fourth cluster 1308B demonstrates uniform strength distribution of approximately around 22-25 MPa across all testing directions. The combination of earth content and 0.5% sucrose in GP-0.5S-25E enables balanced strength development, reducing directional variation compared to GP-0S-25E. The fifth cluster 1310B exhibits consistent strength values, approximately ranging from 20-24 MPa across different testing directions. The 1% sucrose content in GP-1S-25E achieves balance between earth content and geopolymer reaction, resulting in minimal directional strength variation and improved performance. The sixth cluster 1312B shows strength values approximately between 23-26 MPa with reduced variation in different testing directions. The increased sucrose content in GP-1.5S-25E maintains consistent strength development across different loading orientations while enabling higher early-age strength compared to lower sucrose dosages.
FIG. 13C is a graphical representation illustrating wet compressive strength of mould cast and 3D printed samples in L1, L2, and L3 directions at 7-day, in accordance with an embodiment of the present disclosure. FIG. 13C is explained in conjunction with elements from FIGs. 1 to 13B. With reference to FIG. 13C, there is shown a graphical representation 1300C representing wet compressive strength of mould cast and 3D printed samples in L1, L2, and L3 directions at 7-day. The graphical representation 1300C includes a first cluster 1302C representing GP-0S-0E, a second cluster 1304C representing GP-1S-0E, a third cluster 1306C representing GP-0S-25E, a fourth cluster 1308C representing GP-0.5S-25E, a fifth cluster 1310C representing GP-1S-25E, and a sixth cluster 1312C representing GP-1.5S-25E. Each cluster (i.e. the first cluster 1302C, second cluster 1304C, third cluster 1306C, fourth cluster 1308C, fifth cluster 1310C and the sixth cluster 1312C) includes four plots representing mould cast, loaded along a first direction 1318A, a second direction 1316A, and a third direction 1314A as shown in each cluster from left to right in FIG. 13C. The first direction 1318A, second direction 1316A, and third direction 1314A in the graphical representation 1300C represents distinct loading configurations for compressive strength testing. The graphical representation 1300C further includes a reference line at approximately between 20 to24 MPa indicating a minimum strength threshold, demonstrating that all sucrose-modified mixtures achieve significantly higher strength values across all testing directions at 7-day age.
The first cluster 1302C demonstrates strength values approximately ranging between 25-28 MPa across different testing directions. Mould cast specimens achieve approximately 27 MPa, with printed samples showing similar performance in different testing directions, indicating uniform strength development without directional bias at 7-day age. The second cluster 1304C exhibits the highest strength development, approximately ranging between 34-38 MPa across different testing directions. The second direction1316A achieves maximum strength (approximately 38 MPa), followed by the first direction 1318A (approximately 36 MPa) and the third direction 1314A (approximately 33 MPa). The sucrose modification enables enhanced strength development through controlled reaction kinetics and improved structural formation.
The third cluster 1306C shows varying strength development approximately between 19-27 MPa. Mould cast specimens achieve approximately 27 MPa, while printed samples demonstrate notable directional variation, with the second direction 1316A showing lowest strength (approximately 19 MPa), indicating influence of earth content on directional strength development. The fourth cluster 1308C demonstrates strength values approximately between 20-30 MPa across different testing directions. The mould cast specimens achieve approximately 30 MPa, while printed samples show improved directional uniformity compared to GP-0S-25E, indicating beneficial effects of sucrose modification on strength development in earth-containing mixtures. The fifth cluster 1310C exhibits consistent strength development approximately between 28-32 MPa. The 1% sucrose content achieves balance between earth content and geopolymer reaction, resulting in uniform strength distribution across different loading directions and improved overall performance. The sixth cluster 1312C shows strength values approximately between 26-32 MPa with moderate directional variation. The increased sucrose content maintains high strength development while demonstrating slightly increased directional variation compared to GP-1S-25E, particularly in the second direction 1316A.
FIG. 13D is a graphical representation illustrating the wet compressive strength of mould cast and 3D printed samples in L1, L2, and L3 directions at 28-day, in accordance with an embodiment of the present disclosure. FIG. 13D is explained in conjunction with elements from FIGs. 1 to 13C. With reference to FIG. 13D, there is shown a graphical representation 1300D representing wet compressive strength of mould cast and 3D printed samples in L1, L2, and L3 directions at 28-day. The graphical representation 1300D includes a first cluster 1302D representing GP-0S-0E, a second cluster 1304D representing GP-1S-0E, a third cluster 1306D representing GP-0S-25E, a fourth cluster 1308D representing GP-0.5S-25E, a fifth cluster 1310D representing GP-1S-25E, and a sixth cluster 1312D representing GP-1.5S-25E. Each cluster (i.e. the first cluster 1302D, second cluster 1304D, third cluster 1306D, fourth cluster 1308D, fifth cluster 1310D and the sixth cluster 1312D) includes four plots representing mould cast, loaded along a first direction 1318A, a second direction 1316A, and a third direction 1314A as shown in each cluster from left to right in FIG. 13D. The first direction 1318A, second direction 1316A, and third direction 1314A in the graphical representation 1300D represents distinct loading configurations for compressive strength testing. The graphical representation 1300D further includes a reference line at approximately between 25 to30 MPa indicating a minimum strength threshold, demonstrating that all sucrose-modified mixtures achieve significantly higher strength values across all testing directions at 28-day age.
The first cluster 1302D demonstrates strength values approximately between 23-28 MPa across different testing directions. Mould cast specimens achieve approximately 28 MPa, while printed samples show reduced strength in second direction 1316A (approximately 23 MPa), indicating directional dependency in long-term strength development without sucrose modification.
The second cluster 1304D exhibits substantially enhanced strength development, approximately ranging between 32-58 MPa across different testing directions. Mould cast specimens achieve highest strength (approximately 58 MPa), while printed samples show directional variation with the second direction 1316A achieving approximately 45 MPa, the first direction 1318A achieving approximately 38 MPa, and the third direction 1314A achieving approximately 32 MPa. The sucrose modification enables significant long-term strength enhancement through controlled geopolymer reaction. The third cluster 1306D shows uniform strength distribution approximately ranging between 27-28 MPa across different testing directions. The earth content contributes to consistent strength development, though values remain lower than sucrose-modified mixtures. The minimal directional variation indicates clay particle network formation.
The fourth cluster 1308D demonstrates strength values approximately ranging between 28-38 MPa. Mould cast specimens achieve approximately 38 MPa, while printed samples show improved directional uniformity compared to GP-1S-0E. The combination of earth content and 0.5% sucrose enables balanced strength development across loading directions. The fifth cluster 1310D exhibits strength development approximately ranging between 30-45 MPa. Mould cast specimens achieve maximum strength (approximately 45 MPa), while printed samples demonstrate consistent performance across all testing directions (approximately ranging between 30-35 MPa). The 1% sucrose content achieves optimal balance between strength enhancement and directional uniformity. The sixth cluster 1312D shows strength values approximately ranging between 30-42 MPa with moderate directional variation. The increased sucrose content maintains high strength development while demonstrating similar performance to GP-1S-25E, indicating no additional benefit from higher sucrose dosage at 28-day age.
FIG. 13E is a graphical representation illustrating wet compressive strength of mould cast and 3D printed samples in L1, L2, and L3 directions at 365-day, in accordance with an embodiment of the present disclosure. FIG. 13E is explained in conjunction with elements from FIGs. 1 to 13D. With reference to FIG. 13E, there is shown a graphical representation 1300E representing wet compressive strength of mould cast and 3D printed samples in L1, L2, and L3 directions at 365-day. The graphical representation 1300E includes a first cluster 1302E representing GP-0S-0E, a second cluster 1304E representing GP-1S-0E, a third cluster 1306E representing GP-0S-25E, a fourth cluster 1308E representing GP-0.5S-25E, a fifth cluster 1310E representing GP-1S-25E, and a sixth cluster 1312E representing GP-1.5S-25E. Each cluster (i.e. the first cluster 1302E, second cluster 1304E, third cluster 1306E, fourth cluster 1308E, fifth cluster 1310E and the sixth cluster 1312E) includes four plots representing mould cast, loaded along a first direction 1318A, a second direction 1316A, and a third direction 1314A as shown in each cluster from left to right in FIG. 13E. The first direction 1318A, second direction 1316A, and third direction 1314A in the graphical representation 1300E represents distinct loading configurations for compressive strength testing. The graphical representation 1300E further includes a reference line at approximately between 20 to 25 MPa indicating a minimum strength threshold, demonstrating that all sucrose-modified mixtures achieve significantly higher strength values across all testing directions at 365-day age.
The first cluster 1302E demonstrates strength values approximately ranging between 22-38 MPa across different directions. Mould cast specimens achieve approximately 38 MPa, while printed samples show significant directional variation with the first direction 1318A achieving approximately 32 MPa, and reduced strength in the second direction 1316A and the third direction 1314A (approximately ranging between 22-25 MPa), indicating long-term degradation of directional properties. The second cluster 1304E exhibits highest initial strength development, with mould cast specimens reaching approximately 60 MPa. However, printed samples show substantial directional variation with the first direction 1318A achieving approximately 35 MPa, while the second direction 1316A and the third direction 1314A demonstrate reduced strength (approximately ranging between 25-26 MPa), indicating limited long-term durability despite sucrose modification.
The third cluster 1306E shows uniform but lower strength distribution approximately ranging between 23-25 MPa across all testing directions. The absence of sucrose results in strength reduction compared to 28-day values, though directional uniformity is maintained through earth content contribution. The fourth cluster 1308E demonstrates strength values approximately ranging between 20-38 MPa. Mould cast specimens maintain approximately 38 MPa, while printed samples show improved strength in the first direction 1318A (approximately 35 MPa) but reduced performance in the third direction 1314A (approximately 20 MPa), indicating partial effectiveness of low sucrose dosage in long-term strength retention.
The fifth cluster 1310E exhibits enhanced long-term performance with strength values approximately ranging between 30-47 MPa. Mould-cast specimens achieve approximately 47 MPa, while printed samples maintain consistent directional strength (approximately ranging between 30-42 MPa). The 1% sucrose content enables optimal long-term durability through sustained clay-geopolymer interaction. The sixth cluster 1312E shows strength values approximately ranging between 32-46 MPa with improved directional consistency. The increased sucrose content results in enhanced long-term strength retention across all directions, demonstrating superior durability through sustained modification of geopolymer reaction kinetics and clay network stability.
FIG. 13F is a graphical representation illustrating a ratio of wet-to-dry compressive strength at 28-day age, in accordance with an embodiment of the present disclosure. FIG. 13F is explained in conjunction with elements from FIGs. 1 to 13E. With reference to FIG. 13F, there is shown a graphical representation 1300F representing moisture sensitivity of different 3D printable geopolymer-stabilized earth materials. The graphical representation 1300F includes a first cluster 1302F representing GP-0S-0E, a second cluster 1304F representing GP-1S-0E, a third cluster 1306F representing GP-0S-25E, a fourth cluster 1308F representing GP-0.5S-25E, a fifth cluster 1310F representing GP-1S-25E, and a sixth cluster 1312F representing GP-1.5S-25E. Each cluster (i.e. the first cluster 1302F, second cluster 1304F, third cluster 1306F, fourth cluster 1308F, fifth cluster 1310F and the sixth cluster 1312F) includes four plots representing mould cast, loaded along a first direction 1318A, a second direction 1316A, and a third direction 1314A as shown in each cluster from left to right in FIG. 13F. The first direction 1318A, second direction 1316A, and third direction 1314A in the graphical representation 1300F represent distinct loading configurations for compressive strength testing. The graphical representation 1300F further includes a reference line at a value of 1.0, indicating an equal wet and dry strength performance.
The first cluster 1302F exhibits wet-to-dry strength ratios approximately ranging from 0.85 to 1.1 across different directions. The third direction 1314A shows highest ratio (1.1), while the first direction 1318A demonstrates lowest ratio (0.85), indicating directional variation in moisture sensitivity without sucrose modification. The second cluster 1304F demonstrates ratios approximately ranging between 0.95 and 1.2, with the second direction 1316A achieving highest ratio (1.2). The sucrose modification enhances moisture resistance, particularly in the L2 direction, though directional variation persists in printed samples. The third cluster 1306F shows ratios approximately ranging between 1.0-1.1 across all testing directions. The earth content contributes to uniform moisture resistance, with minimal directional variation in wet-to-dry strength relationship. The fourth cluster 1308F exhibits ratios approximately ranging between 0.85 and 1.0. The combination of earth content and 0.5% sucrose maintains consistent moisture resistance, though slightly lower than unmodified earth-containing mixture. The fifth cluster 1310F demonstrates moisture resistance with ratios approximately ranging between 1.0 and 1.15 across all testing directions. The 1% sucrose content achieves enhanced wet strength performance while maintaining directional uniformity. The geopolymer with 1% sucrose is more resistant to damage by environmental factors, evident from 20 – 60% higher compressive strength after 365 days of natural exposure (1 year) compared to the geopolymer-earth without sucrose. The sixth cluster1312F shows ratios value of approximately 1.0 across all testing directions, indicating ideal moisture resistance with minimal directional variation. The increased sucrose content enables uniform performance under both wet and dry conditions.
FIG. 14A is a graphical representation illustrating inter-layer bond strength of the different 3D printed mixes in L1 and L2 directions at 28-day age, in accordance with an embodiment of the present disclosure. FIG. 14A is explained in conjunction with elements from FIGs. 1 to 13F. With reference to FIG. 14A, there is shown a graphical representation 1400A representing the inter-layer bond strength of the different 3D printed mixes in L1 and L2 directions at 28-day age. The graphical representation 1400A includes a setup 1402A for direct measurement of the bonding strength between printed layers. The graphical representation 1400A further includes a first cluster 1404A representing GP-0S-0E, a second cluster 1406A representing GP-1S-0E, a third cluster 1408A representing GP-0S-25E, a fourth cluster 1410A representing GP-0.5S-25E, a fifth cluster 1412A representing GP-1S-25E, and a sixth cluster 1414A representing GP-1.5S-25E. Each cluster (i.e. the first cluster 1404A, second cluster 1406A, third cluster 1408A, fourth cluster 1410A, fifth cluster 1412A and the sixth cluster 1414A) includes two plots representing loading of the material along L1 and L2 direction as shown in each cluster from left to right in FIG. 14A. The L1 and L2 direction in the graphical representation 1400A represents distinct loading configurations for interlayer bond strength testing. The abscissa axis represents several 3D printable geopolymer-stabilized earth materials. The ordinate axis represents the interlayer bond strength measured in megapascal (MPa).
The setup 1402A illustrates a configuration for measuring inter-layer bond strength in printed specimens. A test specimen 1416A comprises three printed layers, each 15 mm in thickness, creating a total height of 30 mm. The test specimen 1416A has width of 50 mm, with the loading zone width of 17.5 mm on each side. Loading is applied to the middle layer through a T-shaped fixture at a controlled rate of 0.025 mm/sec. The inter-layer zones, critical for strength assessment, are positioned between successive printed layers. The configuration enables direct measurement of bonding strength in both L1 (parallel to printing direction) and L2 (perpendicular to printing direction) orientations.
The first cluster 1404A, representing GP-0S-0E, demonstrates inter-layer bond strengths of 2.4 MPa in L1-direction and 1.7 MPa in L2-direction. The lower L2 strength indicates weak layer adhesion in the absence of earth content, resulting from limited structural bridging between successive layers during the printing process. The second cluster 1406A, corresponding to GP-1S-0E, exhibits increased bond strengths of 4.5 MPa in both L1 and L2 directions. The sucrose addition enables uniform strength development across directions through controlled geopolymer reaction kinetics, resulting in 87.5% improvement in L1 and 165% improvement in L2 directions compared to GP-0S-0E. The third cluster 1408A, representing GP-0S-25E, shows bond strengths of 4.0 MPa in L1-direction and 2.2 MPa in L2-direction. The earth content contributes to enhanced layer adhesion through clay particle networks, though directional variation persists without sucrose modification.
The fourth cluster 1410A, corresponding to GP-0.5S-25E, demonstrates bond strengths of 4.1 MPa in L1-direction and 2.5 MPa in L2-direction. The combined effect of earth content and 0.5% sucrose enables improved inter-layer bonding through controlled clay-geopolymer interaction, resulting in 14% enhancement in L2-direction strength compared to GP-0S-25E. The fifth cluster 1412A, representing GP-1S-25E, shows bond strengths of 4.0 MPa in L1-direction and 3.2 MPa in L2-direction. The 1% sucrose content achieves optimal balance between clay network formation and geopolymer reaction, reducing directional strength variation and improving L2-direction strength by 45% compared to GP-0S-25E. The sixth cluster 1414A, corresponding to GP-1.5S-25E, exhibits bond strengths of 4.3 MPa in L1-direction and 4.0 MPa in L2-direction. The increased sucrose content enables near-isotropic bonding behaviour through enhanced clay-geopolymer interaction, achieving the most uniform strength distribution across both loading directions among all earth-containing mixtures.
FIG. 14B is a graphical representation illustrating total shrinkage behavior of different geopolymer mixtures over a 60-day period, in accordance with an embodiment of the present disclosure. FIG. 14B is explained in conjunction with elements from FIGs. 1 to 14A. With reference to FIG. 14B, there is shown a graphical representation 1400B representing time-dependent shrinkage behavior of various geopolymer mixtures. The time measured in days is on the abscissa axis. The shrinkage strain is measured in micro-strain units on the ordinate axis. The graphical representation 1400B includes a first curve 1402B representing GP-0S-0E, a second curve 1404B representing GP-1S-0E, a third curve 1406B representing GP-0S-25E, a fourth curve 1408B representing GP-0.5S-25E, a fifth curve 1410B representing GP-1S-25E, and a sixth curve 1412B representing GP-1.5S-25E. The moist curing period demonstrates influence on early-age shrinkage behaviour of different 3D printable geopolymer-stabilized earth material.
The first curve 1402B exhibits the highest shrinkage, reaching approximately “-3700” micro-strain at 60 days. The first curve 1402B demonstrates rapid shrinkage development during the first 15 days followed by gradual stabilization. The absence of both sucrose and earth content in GP-0S-0E results in unrestricted shrinkage development through rapid geopolymer network formation. The second curve 1404B shows significantly reduced shrinkage, achieving approximately “-2300” micro-strain at 60 days, representing a 42% reduction compared to GP-0S-0E. The sucrose addition in GP-1S-0E controls geopolymer reaction kinetics, enabling more uniform network development and reduced shrinkage strain accumulation during the initial 20-day period.
The third curve 1406B demonstrates improved shrinkage resistance, reaching approximately “-2200” micro-strain at 60 days. The presence of clay particles in GP-0S-25E creates a structured network that restricts deformation, though without sucrose modification, rapid early-age shrinkage development persists during the first 10 days. The fourth curve 1408B exhibits controlled shrinkage development, achieving approximately “-2500” micro-strain at 60 days. The combination of earth content and 0.5% sucrose in GP-0.5S-25E enables balanced reaction kinetics and clay network formation, resulting in more gradual shrinkage development during the initial 20-day period. The fifth curve 1410B shows optimal shrinkage performance, reaching approximately “-2000” micro-strain at 60 days, representing a 13% reduction compared to GP-0S-25E. The 1% sucrose content in GP-1S-25E achieves synergistic interaction between clay particles and geopolymer reaction, enabling controlled network development and enhanced dimensional stability throughout the measurement period. The sixth curve 1412B demonstrates similar performance to GP-1S-25E, achieving shrinkage strain value of approximately “-2100” micro-strain at 60 days. The increased sucrose content in GP-1.5S-25E maintains effective shrinkage control through modified reaction kinetics and enhanced clay-geopolymer interaction, though without additional improvement over the 1% sucrose dosage.
FIG. 14C is a graphical representation illustrating the relationship between inter-layer bond strength and shrinkage at 28-day age for different 3D printable geopolymer-stabilized earth material, in accordance with an embodiment of the present disclosure. FIG. 14C is explained in conjunction with elements from FIGs. 1 to 14B. With reference to FIG. 14C, there is shown a graphical representation 1400C representing correlation between inter-layer bond strength and shrinkage behaviour. The shrinkage at 28-day age measured in micro-strain on the abscissa axis. The inter-layer bond strength measured in megapascal (MPa) on an ordinate axis. The graphical representation 1400C includes a zone1402C indicating distinct clustering of GP-S-25E mixtures, a first point 1404C representing GP-1S-0E, and a second point 1406C representing GP-0S-0E.
The zone 1402C exhibits superior performance of the different GP-S-25E mixtures. Within the zone 1402C, the different GP-S-25E mixtures exhibit shrinkage values approximately ranging between “-1500” to “-2000” micro-strain and inter-layer bond strengths approximately ranging from 2.5 to 4.7 MPa, indicating balance between dimensional stability and structural integrity of one of the mixtures from different GP-S-25E mixtures. The first point 1404C demonstrates intermediate performance with shrinkage of approximately “-2500” micro-strain and inter-layer bond strength of approximately “2.1 MPa”. The absence of earth content in GP-1S-0E results in reduced bond strength despite sucrose modification, highlighting the role of clay particles in enhancing layer adhesion. The second point 1406C exhibits the poorest performance with shrinkage reaching approximately “-3000” micro-strain and inter-layer bond strength of approximately “1.6 MPa”. The absence of both sucrose and earth content in GP-0S-0E results in high shrinkage deformation and limited layer adhesion, demonstrating the necessity of sucrose and earth content for achieving satisfactory printing performance. The graphical representation 1400C demonstrates clear improvement in both shrinkage resistance and bond strength with the incorporation of earth content and sucrose modification. The earth-containing mixtures achieve up to 50% reduction in shrinkage strain while simultaneously improving inter-layer bond strength by up to 193% compared to the baseline GP-0S-0E, evidencing the synergistic benefits of combined clay-sucrose modification in geopolymer systems.
Modifications to embodiments of the present disclosure described in the foregoing are possible without departing from the scope of the present disclosure as defined by the accompanying claims. Expressions such as “including,” “comprising,” “incorporating,” “have,” “is” used to describe, and claim the present disclosure are intended to be construed in a non-exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or to exclude the incorporation of features from other embodiments. The word “optionally” is used herein to mean “is provided in some embodiments and not provided in other embodiments.” It is appreciated that certain features of the present disclosure, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable combination or as suitable in any other described embodiment of the disclosure.
, Claims:CLAIMS
We claim:
1. A 3D printable geopolymer-stabilized earth material comprising:
a geopolymer binder comprising ground granulated blast furnace slag and fly ash;
fine aggregates comprising crushed rock sand and excavated soil containing kaolinite-rich non-expansive clay;
an alkaline activator; and
a controlled retarding agent comprising sucrose dispersed in the alkaline activator,
wherein the 3D printable geopolymer-stabilized earth material maintains at least 90% flow retention for a minimum of 130 minutes after mixing and achieves a shape retention factor of at least 90% when extruded.

2. The 3D printable geopolymer-stabilized earth material as claimed in claim 1, wherein the geopolymer binder comprises 50–75% ground granulated blast furnace slag and 25–50% fly ash by weight.

3. The 3D printable geopolymer-stabilized earth material as claimed in claim 1, wherein the excavated soil content has a clay content of 40–45% by weight and a plasticity index of 16%.

4. The 3D printable geopolymer-stabilized earth material as claimed in claim 1, wherein the alkaline activator comprises an 8 mol/L (M) sodium hydroxide solution.
5. The 3D printable geopolymer-stabilized earth material as claimed in claim 1, wherein the retarding agent is added in amounts of 0.50%, 1.50%, and 1% by weight of the geopolymer binder.

6. The 3D printable geopolymer-stabilized earth material as claimed in claim 1, wherein the material exhibits a wet compressive strength of 20 – 35 MPa after curing for 28 days.

7. The 3D printable geopolymer-stabilized earth material as claimed in claim 1, wherein the material reduces capillary water absorption by 18 – 32% and detrimental pore volume (corresponding to pore size in the range of 10 nm – 100 nm) by 35% compared to geopolymer-stabilized materials without sucrose.

8. The 3D printable geopolymer-stabilized earth material as claimed in claim 1, wherein the material achieves an inter-layer bond strength at least 28% higher than geopolymer-stabilized materials without sucrose.

9. The 3D printable geopolymer-stabilized earth material as claimed in claim 1, wherein the shape retention factor is maintained at 90–97% during 3D printing.

10. The 3D printable geopolymer-stabilized earth material as claimed in claim 1, wherein the material comprises:
50–75% by weight of the geopolymer binder;
25–50% by weight of the fine aggregates;
8–12% by weight of the alkaline activator; and
0.5–1.5% by weight of the retarding agent.

11. A method (100) of preparing a 3D printable geopolymer-stabilized earth material, comprising:
collecting excavated soil containing non-expansive clay construction and demolition (C&D) waste;
drying the excavated soil and sand to constant mass;
sieving the dried soil to remove particles larger than 4.75 mm;
combining the sieved soil with sand and geopolymer binder to attain a clay-to-binder ratio of 0.225 by mass and aggregate-to-binder ratio of 2:1 by mass;
dissolving a retarding agent in an alkaline activator to form a retarding activator solution;
mixing the geopolymer binder and the activator solution in a solution-to-binder ratio to form the 3D printable geopolymer-stabilized earth material, wherein the 3D printable geopolymer-stabilized earth material maintains at least 90% flow retention for a minimum of 130 minutes after mixing and achieves a shape retention factor of at least 90% when extruded.

12. The method (100) of preparing a 3D printable geopolymer-stabilized earth material as claimed in claim 11, wherein the solution-to-binder ratio is in the range of 0.67–0.75 to ensure optimal flowability and buildability.

13. A method (200) of 3D printing a construction element, comprising:
preparing a 3D printable geopolymer-stabilized earth material comprising geopolymer binder, excavated soil, an alkaline agent, and a retarding admixture;
extruding the 3D printable geopolymer-stabilized earth material through a nozzle at a controlled flow rate;
depositing the 3D printable geopolymer-stabilized earth material in sequential layers with a layer height of 15–18 mm; and
maintaining an open printing time of at least 130 minutes; and
building a structure to a height of at least 1.05 meters with a shape retention factor of 90% or more.

14. The method (200) of 3D printing a construction element as claimed in claim 13, wherein the extrusion is carried out using a circular nozzle with a diameter of 20–40 mm and a controlled layer height of 15–18 mm.

15. The method (200) of 3D printing a construction element as claimed in claim 13, comprises optimizing printing parameters including stand-off distance, printing speed, and layer height to achieve the shape retention factor of 90–97%.