Description:TITLE OFTHE INVENTION:
Optimized Strength of Lime-Pozzolana Concrete Through Curing Methods.

DESCRIPTION:

TECHNICAL FIELD
the development of lime pozzolana concrete (LPC) as a sustainable alternative to traditional cement, focusing on reducing CO₂ emissions through alkali activation. It investigates the material science behind the pozzolanic reaction between hydraulic lime, fly ash, and sodium silicate gel, which forms C-S-H/C-A-S-H gels to enhance concrete strength. The study evaluates key mechanical properties—compressive, tensile, and flexural strength—under different curing methods (normal water vs. wet hessian) while adhering to standardized IS codes (e.g., IS 516:2021) for mix design and performance analysis. By leveraging industrial byproducts like fly ash and innovative chemical activators, the research demonstrates a practical approach to developing eco-friendly, high-performance concrete for construction applications. The findings highlight LPC's potential in sustainable structural engineering and waste utilization.

DEFINITION
Lime Pozzolana Concrete (LPC) is an eco-friendly alternative to conventional cement-based concrete, composed primarily of hydraulic lime (as the binder) and pozzolanic materials (such as fly ash, volcanic ash, or calcined clay). The mixture undergoes a pozzolanic reaction—where silica and alumina from the pozzolan react with calcium hydroxide from lime in the presence of water—to form calcium silicate hydrate (C-S-H) and calcium aluminate silicate hydrate (C-A-S-H) gels. These gels provide binding properties, enhancing the concrete's strength, durability, and impermeability.
LPC is distinguished by its:
1. Low Carbon Footprint: Reduces CO₂ emissions by replacing energy-intensive Portland cement.
2. Sustainable Composition: Utilizes industrial byproducts (e.g., fly ash) or natural pozzolans.
3. Moderate Strength Development: Achieves structural-grade performance, especially when activated by alkali solutions like sodium silicate.
4. Historical and Modern Applications: Used in heritage restoration and modern sustainable construction.
LPC is particularly valued for its environmental benefits, chemical resistance, and suitability for repair mortars, masonry, and non-load-bearing structures.

BACKGROUND AND PRIOR ART OF THE INVENTION:
IN202241065829A
A key component of the steel industry's sustainability is effective waste management. Due to the rapid increase in construction prices and the depletion of natural resources, the use of waste materials in the construction industry is becoming more and more crucial. Waste management in this context refers to minimizing waste and repurposing waste materials whenever possible. Reduction, recycling, and reuse of trash are recognized as crucial components of sustainable resource management in solid waste management methods. Cinder is a by-product created in furnaces during the process of separating molten steel from impurities. This study recommends replacing Natural River sand entirely with M-sand and replacing coarse aggregate with Cinder in various proportions. This research is being conducted to better understand the effects of Cinder on concrete in terms of compressive, split tensile, and flexural strength, as well as microstructural analysis SEM and XRD for the selected optimum mix. The curing times for the proportions are 7 and 28 days, respectively.

CN104863351A
The invention discloses a cinder concrete composite insulation non-dismantling fire-resistant mold plate and a construction method thereof. The cinder concrete composite insulation non-dismantling fire-resistant mold plate comprises a thermal insulation layer (1), an internal bonding fine furnace slag mortar layer (2) bonded on the inner side of the thermal insulation layer (1), an external bonding fine furnace slag mortar layer (3) bonded on the outer side of the thermal insulation layer (1), and a coarse cinder concrete reinforcing layer (4) bonded on the external bonding fine furnace slag mortar layer (3), wherein alkali-proof mesh fabric (5) is arranged between the external bonding fine furnace slag mortar layer (3) and the coarse cinder concrete reinforcing layer (4); mesh fabric is arranged in both the internal bonding fine furnace slag mortar layer (2) and the external bonding fine furnace slag mortar layer (3). The cinder concrete composite insulation non-dismantling fire-resistant mold plate can be formed integrally with a building, and is low in flaking off possibility, high in safety factor, energy-saving, environment-friendly, light, high in strength, heat-insulating, heat-proof, fire-resistant, safe and stable in quality, convenient in construction, and as long as the building in service life. The construction method has the advantages that the operating efficiency is high; manpower and material resources can be saved greatly; the construction cost is low.

CN204590275U
The utility model discloses a kind of cinder concrete complex heat-preservation to exempt to tear fire prevention template open, it comprises insulation layer (1), be bonded in the interior bonding fine slag screed (2) of insulation layer (1) inner side, be bonded in the outer bonding fine slag screed (3) in insulation layer (1) outside, be bonded in the thick cinder concrete enhancement Layer (4) on outer bonding fine slag screed (3); Alkaline-resisting grid cloth (5) is provided with between outer bonding fine slag screed (3) and thick cinder concrete enhancement Layer (4); Grid cloth is equipped with in interior bonding fine slag screed (2) and outer bonding fine slag screed (3); The utility model can be one-body molded with building, be not easy to come off, safety factor is high, have that energy-saving and environmental protection, lightweight, high-strength, insulation, heat insulation, fire prevention, quality safety are stable, easy construction and building be with advantages such as life-spans, meet the requirement of national green building standard, application prospect is extensive.

CN1141992A
A light sound-insulation building board comprises mainly slag concrete base-material and reinforcing materials. Said slag concrete base-material mainly comprises (weigh portion) 100 of slag, 10-35 of gelatinizing material, 0.1-1 of water-proof agent, 15-35 of water, and said reinforcing materials are glass fiber and concrete bar and non-woven fabric. Advantage: light, high strength, heat-sound-insulation, fire retardant and waterproof, convenient for mounting and low cost etc.

CN207131039U
The utility model discloses heat insulating and sound insulating cinder concrete floating build floor structure, including floor layer, wall, cinder concrete layer and heat insulating and sound insulating pad, the wall is fixedly connected on floor layer close to the top of its side, the cinder concrete layer is fixedly connected on the top of floor layer, the side of the wall is fixedly connected with reinforcement, the surface of the reinforcement is fixedly connected with damping surrounding edge, the side of wall is fixedly connected with the side of damping surrounding edge, the side of cinder concrete layer is fixedly connected with the opposite side of damping surrounding edge, the side of damping surrounding edge opens up fluted, the reinforcement is fixedly connected by the groove of damping surrounding edge with damping surrounding edge.The utility model solves the problems, such as to only rely on that heat insulating and sound insulating pad and filter residue concrete layer are undesirable come the using effect that is incubated and insulated against sound by being used cooperatively between the structure such as above-mentioned, realizes that the heat insulating and sound insulating effect of floor is more preferable, and insulation noise reduction becomes apparent from.

CA2821512C
A geopolymer composite ultra high performance concrete (GUHPC), and methods of making the same, are provided herein, the GUHPC comprising: (a) a binder comprising one or more selected from the group consisting of reactive aluminosilicate and reactive alkali-earth aluminosilicate; (b) an alkali activator comprising an aqueous solution of metal hydroxide and metal silicate; and (c) one or more aggregate.

WO2021178672A2
A light weight geopolymer concrete, having a specific gravity less than 2.0, more typically between 1 and 1.3, is provided that has compressive strength comparable to or greater than ordinary Portland concrete. The light weight geopolymer concrete has low shrinkage, expansion, and cracking, and substantially no loss of compressive strength when exposed to high temperatures of 800 °C or greater, as would occur in a fire. To be useful as a load bearing member for general applications, such as residential housing, the compressive strength of the light-weight geopolymer concrete should be at least 10 MPa, preferably greater than 12 MPa, for example greater than 15 MPa. For more demanding uses, the compressive strength should be near or at the compressive strength of concrete, that is, greater than 20 MPa, preferably greater than 30 MPa, and optimally greater than 35 MPa. To be useful during and after a fire, the strength must not be reduced by more than 20%, preferably not less than 10%, optimally not reduced at all when exposed to heat up to 800 °C. Embodiments of the invention include low-density high-temperature-resistant geopolymer concrete which increases load bearing strength when exposed to temperatures above 400 °C, preferably at 800 °C. Key constituents for forming most embodiments include a geopolymer source such as fly ash, a cement-coated expanded vermiculite, a fiber such as wollastonite, and soluble silicates such as alkali silicates.

JP2018515412A
The present invention relates to (a) 20% to 70% of at least one aluminum organic acid and (b) 3% to 20% of a carboxylic acid polymer, carboxylic acid, Adjuvant for cement or refractory concrete composition comprising at least one peptizer selected from one of salts, or combinations thereof, and (c) 7% to 44% of at least one mineral oxide About. The invention further relates to the use of such adjuvants for improving the drying time of the refractory concrete composition or for improving the permeability of the refractory concrete composition. The present invention finally relates to a cement composition and a refractory concrete composition each containing such an adjuvant.

KR100908498B1
A cement-free alkali-activated brick is provided to show excellent strength and chemical resistance as well as freezing and thawing resistance while securing low the heat of hydration. A cement-free alkali-activated brick(100) is composed of: a cement-free alkali-activated binder including a raw material containing blast furnace slag and an alkali inorganic material containing sodium-based ingredients; fine aggregate containing sand or silicon dioxide powder; and water. The alkali inorganic material is selected among sodium silicate, powdered sodium hydroxide, a sodium silicate aqueous solution and a sodium hydroxide aqueous solution. A weight ratio of the sodium-based ingredients to raw material is 0.038~0.088, herein the weight of the sodium-based ingredients is converted to Na2O.

CN101337802A
The invention belongs to the technical field of a constructional material, in particular to slag powder dry mortar which is mixed in large quantity with desulfuration plaster as an excitant. The slag powder dry mortar consists of cement, powdered slag, desulfuration plaster, lime, sodium sulfate, cellulose ether, emulsion powder and sand. By using the slag powder dry mortar, the solid waste, namely desulfuration plaster, is used efficiently as a resource. In addition, under the circumstance of not reducing the properties of mortar, the problem that the early strength of mortar is low because of large quantity of slag powder mixed. The slag powder dry mortar is applicable for plastering and masonry of ordinary buildings, and can meet the waterproof requirement.

CN104254504B
The invention discloses a kind of method for being used to prepare the geo-polymer splicing adhesive composition for cementitious product, the cementitious product is such as concrete, pre-cast building element and panel, mortar, for the patching material of road repair and other patching materials.The geo-polymer cementitious composition of some embodiments is made by mixing the aluminosilicate mineral material through thermal activation, calcium sulphoaluminate cement, calcium sulfate and the Synergistic mixtures of chemical activating agent and water.

CN104245621B
The invention discloses a kind of method for being used to prepare the geo-polymer splicing adhesive composition for cementitious product, the cementitious product is such as concrete, pre-cast building element and panel, mortar and patching material.The geo-polymer cementitious composition of some embodiments is made by the Synergistic mixtures of aluminosilicate mineral material, aluminous cement, calcium sulfate and chemical activating agent of the mixing through thermal activation and water.

JP2005097091A
To obtain an ecocement composition exhibiting high initial strengths and particularly high strengths in the releasing from a mold.

SOLUTION: This cement composition contains ecocement and lithium sulfate. The ecocement in the cement composition is the one prepared by using ≥500 kg ash produced in the incineration of municipal refuse to 1,000 kg cement in terms of dry base. The ecocement in the cement composition is regular ecocement containing ≤0.1 wt.% chloride ion per the cement. The ecocement in the cement composition is rapid hardening ecocement containing 0.5-1.5 wt.% chloride ion per cement. The cement composition contains 0.01-5 wt.% lithium sulfate per the cement. The cement composition contains 0.1-5 wt.% water reducing agent. A method for producing a cement hardened body is carried out by pouring the cement composition in a molding flask, and after steam aging at 50-90°C, taking out the hardened body composed of the cement composition from the molding flask.

CN209211761U
The utility model discloses a kind of spliced cinder concrete wallboards, include wallboard body, are equipped with groove along the middle part on four side of wallboard body, the two sides of wallboard body are equipped with the lug boss that area is less than wallboard body area, and the side of lug boss is equipped with link slot.The utility model has bonding strength high, and junction is not easy to crack, safety and beautiful, the wallboard production feature low with installation difficulty.

AU2021312020A1
Method for manufacturing a concrete from activated slag, comprising at least the steps consisting of: a) arranging a premixture P of water and granulates, the temperature of the premixture P being at least equal to 10°C, b) arranging an activation system A comprising at least a co-binder, a chelating agent, an alkali metal carbonate and a carbonated material different from the alkali metal carbonate, c) incorporating the activation system A and a slag S by mixing them into the premixture P, the activation system A and slag S being introduced successively and/or simultaneously, d) continuing the mixing until a fresh concrete is obtained, and e) allowing the fresh concrete to cure.

CN101190834A
The invention discloses a magnesium slag aerated concrete block and a preparation method thereof, which takes the raw materials at the weight ratio of: magnesium-reduced slag of 50-87 portions, cement of 5-30 portions, gypsum of 3-10 portions, coal cinder of 5-25 portions and gas former of 0.05-0.15 portions, and then the product is obtained by adding water of 20-60 percent at the weight proportion of all the dry materials. The product is obtained according to the methods as follows: magnesium-reduced slag, coal cinder, cement, gypsum, water and gas former are mixed evenly at certain proportion and then are treated with standing and maintaining, inverting and incising, autoclaving and conserving. The invention adopts the magnesium slag generated from the magnesium-smelting process as the main raw material to produce 4MPa building aerated concrete block to be conducive to the reuse of the waste, thereby the enterprise not only is free from the expense of waste treatment, but also has new economic benefit, thus avoiding the occupation of land.

CN1264772C
The present invention relates to a light-weight aggregate and a preparation method thereof, particularly to a light-weight aggregate with a reactivity surface layer, which comprises one kind of granules of clay granules or shale rock granules or pulverized coal ash granules with the granule diameter of 5 to 25mm. The light-weight aggregate is characterized in that raw slurry is also added, and the weight of powdery materials in the raw slurry is 15 to 25% of the total weight of the light-weight aggregate. The powdery materials in the raw slurry are clay soil powder, limestone powder, fluorite powder and gypsum powder, and the components of the limestone powder, the clay soil powder, the fluorite powder and the gypsum powder of the powdery materials of the raw slurry comprise the following percentages by the total weight of the powdery materials of the raw slurry: 70 to 83%, 14 to 27%, 1% and 2%, wherein CaO content in the limestone powder is from 45% to 54%, SiO2 content in the clay soil powder is from 50% to 70%, CaF2 content in the fluorite powder is from 40% to 80%, and SO3 content in the gypsum powder is from 35% to 40%. The present invention has the characteristics of reactivity surface layer.

CN109987903A
The present invention provides a kind of blast-furnace cinder powder concrete applied on highway, blast-furnace cinder powder concrete is made of sandstone raw material, cement, admixture, water-reducing agent, and admixture is the mixture of ground granulated blast furnace slag or ground granulated blast furnace slag and flyash.Ground granulated blast furnace slag is gypsum and grinding aid to be added in blast-furnace cinder, and be made through superfine grinding technique, and the specific surface area of ground granulated blast furnace slag >=450 ㎡/kg.When admixture is the mixture of ground granulated blast furnace slag and flyash, the incorporation of flyash is the 15.0% of cement and admixture gross mass.The application of blast-furnace cinder powder concrete through the invention can effectively increase the mobility of concrete, reduce the total alkali of concrete, improve the durability of concrete, reduce the cost of concrete.

CN110078445A
The invention belongs to building material technical fields, and in particular to a kind of high-strength insulation full lightweight concrete and its preparation method and application.It by weight include following components: ordinary portland cement 10-30; II grades of flyash 4-10; 5-10 parts of graining blast-furnace cinder micro-powder, modified vitrification micro-bead 1-6, foaming agent: 0.1~2.5; thickener: 0.2~1.0; water-retaining agent 0.06-0.08, water 10-20, polypropylene fibre 0.08-0.1; haydite 20-35, pottery sand 1-26.9.The present invention carries out surface modification treatment to glass bead, and then prepare the full lightweight concrete of superior performance mainly using haydite, glass bead as coarse-fine aggregate.This product thermal insulation property is good, and intensity is higher, it is significantly improved than the full lightweight concrete strength of materials that haydite perlite is prepared, decreases drastically than the full lightweight concrete material thermal conductivity that ceramsite and ceramic sand is prepared, be applicable to be used as structural thermal insulation lightweight aggregate concrete material.

WO2015018952A1
The invention relates to a method for producing cinder concrete, for the valorisation of industrial waste, the slag in this case originating in the electric arc furnace steel industry, by means of the encapsulation thereof in a ceramic matrix of a composite material such as concrete, using it as a hydraulic binder. The method consists in substituting part of the cement, which is applied as a binder, with stainless steel slag, given the cementing characteristics thereof, in a quantity of up to a total of 25% of the cement. Said slags are highly abrasive, which provides the resulting concrete with a high resistance to wear. This characteristic means that the concrete obtained by means of said method is optimum for producing structures such as accropodes, tetrapods and/or caissons for marine filling, arranged as ripraps for shelter from the sea.

CN109020351A
The invention discloses a kind of concrete formulation and its manufacturing methods, its raw material is as follows by weight: 10-18 parts of cement, it is 5-10 parts husky, 10-12 parts of quartz sand, 10-15 parts of rubble, 8-12 parts of cinder, 10-15 parts of binder, 10-15 parts of concrete waste residue, 2-6 parts of concrete additive, 2-6 parts of pulverized limestone, 1-6 parts of talcum powder, 20-25 parts of water, a kind of cement, it is husky, quartz sand, rubble, cinder, concrete waste residue, pulverized limestone, talcum powder, which is successively added in mixing plant, to be pre-mixed, with cement, it is husky, quartz sand, rubble, cinder, binder, concrete waste residue, concrete additive, pulverized limestone, talcum powder is raw material, the specific gravity of strict control each component, change traditional concrete formulation, cinder is the waste after coal use, it is mixed Solidifying soil waste materials are discarded construction wall rubbish, and cost of material is saved in recycling and reusing, and a large amount of cinder and concrete construction garbage reclamation utilize, more protect environment, avoid the waste of material.

CN101186473A
The invention provides a concrete, which comprises cement, sand, water, ceramic aggregate and wastes incineration ash. The invention further provides a preparation method of the concrete, which comprises the following steps: the solid wastes generated by garbage power plants are treated through magnetic separation, screening and disinfection and then are made into the wastes incineration ash; the industrial ceramic wastes generated by industries are treated through crushing and screening and then made into the ceramic aggregate; the predetermined compound of cement, sand, water, ceramic aggregate and wastes incineration ash are stirred and made into the concrete. The invention also provides a processing method of wastes incineration ash. Furthermore, the invention fully uses a plurality of solid wastes and can high effectively and environmentally treat wastes incineration ash and ceramic aggregate, thus reducing land occupancy and environmental pollution.

Detailed description

This experimental study titled *"A Comparative Assessment of Mechanical Properties of Lime Pozzolana Concrete Activated by Sodium Silicate Gel"* addresses the environmental challenges of cement production by developing Lime Pozzolana Concrete (LPC) as a sustainable alternative, focusing on the role of sodium silicate gel as a chemical activator to enhance the pozzolanic reaction, comparing strength development under normal water curing versus wet hessian curing, and optimizing mix designs with hydraulic lime (20–35%), fly ash, and sodium silicate (7.5–52.5%). The research utilized high-purity hydraulic lime (92% CaO), Class F fly ash, and locally sourced aggregates, following a base mix ratio of 1:1:2 (LP20) as per IS 5817:1992, with variations in lime and sodium silicate to create seven mixes, tested for compressive, split tensile, and flexural strength at intervals up to 180 days. Key findings revealed that the SLP20NM5 mix (25% lime + 37.5% sodium silicate) achieved the highest compressive strength (2.86× LP20NM0 at 28 days), with normal water curing outperforming wet hessian curing by 12–42%, while sodium silicate accelerated the formation of C-S-H/C-A-S-H gels, reducing porosity and improving density, ultimately cutting CO₂ emissions by ~50% compared to conventional concrete. Technical innovations included demonstrating sodium silicate's effectiveness in overcoming lime's slow strength gain, confirming denser matrices through SEM analysis, and ensuring compliance with IS 456:2000 for structural-grade concrete. The study recommends LPC for moderate-strength structures, heritage restoration, and non-load-bearing elements, suggesting future research on local pozzolans and alternative activators. The conclusions validate LPC as a viable, low-carbon material, offering a blueprint for sustainable construction aligned with UN SDGs, bridging traditional lime technology with modern alkali-activation methods, and providing scalable solutions for emerging economies.

To further clarify the advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS
The objects and features of the present invention, which are believed to be novel, are set forth with particularity in the appended claims. The presentinvention, both as to its organization and manner of operation, together with further objects and advantages, may best be understood by reference to the following description, taken in connection with the accompanying drawings, in which:

1. Figures Depicting Compressive Strength
Figure 1: Mean compressive strength vs. Mix ID under wet hessian curing.
Displays the compressive strength variations for different mix designs (SLP20WM1 to SLP20WM7) at intervals of 7, 28, 56, 91, and 180 days.
- Highlights the superior performance of mixes with optimal hydraulic lime and sodium silicate gel content.

- Figure 2: Mean compressive strength vs. Mix ID under normal water curing.
- Shows similar trends as Figure 1 but emphasizes the enhanced strength achieved through normal water curing compared to wet hessian curing.

2. Figures Depicting Split Tensile Strength
- Figure 3: Split tensile strength vs. Mix ID under wet hessian curing.
- Illustrates the split tensile strength variations for mixes (SLP20WM1 to SLP20WM7) at various curing intervals.
- Demonstrates the impact of sodium silicate gel on improving tensile properties.

Figure 4: Split tensile strength vs. Mix ID under normal water curing.
- Highlights the superior tensile strength achieved through normal water curing, with optimal mix designs outperforming conventional lime-pozzolana concrete.

3. Figures Depicting Flexural Strength
- Additional figures Figure 5&6 likely depict flexural strength trends for different mix designs under both curing methods.

Purpose of Drawings
The figures provide visual evidence of the mechanical performance improvements in lime pozzolana concrete due to sodium silicate gel activation and different curing methods. They support the study's conclusions by showing comparative data across various mix designs and testing intervals.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
To promote an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings, and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof. Reference throughout this specification to "an aspect", "another aspect," or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase "in an embodiment", "in another embodiment" and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.

Materials used for making
The materials used in the development of lime pozzolana concrete activated by sodium silicate gel were carefully selected to ensure optimal performance and sustainability. Hydraulic lime with 92% purity and a specific gravity of 2.2 was sourced from Sri Sai Venkata Teja Chemicals, Piduguralla, conforming to IS 712:1984 and IS 6932:1973 standards. Fly ash, obtained from VTPS-Ibrahimpatnam with a specific gravity of 2.89, served as a pozzolanic material that reacts with lime to form calcium silicate hydrates, enhancing strength and durability. Sodium silicate gel, procured from Lakshmi Chemicals, Vijayawada, acted as a chemical activator to accelerate the reaction between lime and fly ash, improving hardening and mechanical properties.

Locally available fine aggregate, consisting of river sand conforming to Zone II specifications, had a specific gravity of 2.68, fineness modulus of 3.3, moisture content of 7.8%, and water absorption of 8%. The coarse aggregate comprised crushed stone with 60% of 20 mm-sized particles and 40% of 10 mm-sized particles, having a specific gravity of 2.78, fineness modulus of 7, moisture content of 2%, and water absorption of 2.6%. Finally, water meeting IS 456:2000 standards was used for hydration and strength development in concrete mixes. These materials were combined in varying proportions to create structural-grade lime pozzolana concrete optimized for sustainability and mechanical performance.

Methodology Used

The methodology for developing lime pozzolana concrete (LPC) activated by sodium silicate gel involved a systematic approach to mix design, specimen preparation, curing, and testing. The mix proportion of 1:1:2 (lime: pozzolana: aggregate) was selected based on IS 5817:1992 recommendations. Extensive trial mixes were conducted to determine optimal material proportions for structural-grade concrete. Hydraulic lime content was varied in 5% increments up to 35%, while sodium silicate gel was adjusted in 7.5% increments up to 52.5%, with the remaining portion consisting of fly ash. Workability was assessed using compaction factor and slump cone tests as per IS standards, ensuring a compaction factor of 0.85 ± 0.01.

Concrete specimens were cast in steel molds with dimensions of 150 mm × 150 mm × 150 mm (cubes), 150 mm diameter × 300 mm height (cylinders), and 500 mm × 100 mm × 100 mm (beams). Three specimens were cast per set, with six samples for each mix, following IS 516:2021 guidelines. After demolding, the specimens underwent two curing methods: wet hessian curing and normal water curing. Wet hessian curing ensured continuous moisture supply, which is essential for proper hydration and carbonation, while normal water curing was particularly effective for fly ash-based concrete, enhancing strength at later ages.

Mechanical properties such as compressive strength, split tensile strength, and flexural strength were evaluated at intervals of 7, 28, 56, 91, and 180 days. Mix notations were assigned based on the composition and curing method. For example, LP20WM0 and LP20NM0 referred to mixes with 20% hydraulic lime and no sodium silicate gel under wet hessian and normal water curing, respectively. Variations incorporating sodium silicate gel in increments up to 52.5% were designated as SLP20WM1 to SLP20WM7 for wet hessian curing and SLP20NM1 to SLP20NM7 for normal water curing.

The tests revealed that the inclusion of sodium silicate gel significantly enhanced the reaction between lime and fly ash, forming calcium silicate hydrate (C-S-H) and calcium aluminate silicate hydrate (C-A-S-H) gels, which contributed to improved strength development and a denser microstructure with reduced porosity. The highest compressive strength was observed in mixes containing 20%-25% hydraulic lime and 30%-37.5% sodium silicate gel under normal water curing conditions. This methodology demonstrated the feasibility of producing sustainable lime pozzolana concrete with superior mechanical properties compared to traditional cement-based concrete.

Experimental Study

The experimental study conducted on lime pozzolana concrete (LPC) activated by sodium silicate gel involved evaluating its mechanical properties through three key tests: compressive strength, split tensile strength, and flexural strength. Each test was performed at multiple intervals (7, 28, 56, 91, and 180 days) under two curing methods: wet hessian curing and normal water curing. Below is a detailed breakdown of the tests:

1. Compressive Strength Test
- Objective: Determine the ability of the concrete to withstand axial loads.
- Procedure: Conducted as per IS 516:2021 standards on cube specimens (150 mm × 150 mm × 150 mm).
- Results:
- The highest compressive strength was observed in mixes containing 20%-25% hydraulic lime and 30%-37.5% sodium silicate gel under normal water curing.
- Sodium silicate gel significantly enhanced the reaction between silica in fly ash and calcium in lime, forming calcium silicate hydrate (C-S-H) and calcium aluminate silicate hydrate (C-A-S-H), leading to improved strength.
- Normal water curing consistently yielded better results compared to wet hessian curing.

-

2. Split Tensile Strength Test
- Objective*: Assess the tensile capacity of the concrete when subjected to lateral forces.
- Procedure: Conducted on cylindrical specimens (150 mm diameter × 300 mm height) following IS standards.
- Results:
- Similar trends as compressive strength were observed, with mixes incorporating sodium silicate gel showing superior tensile strength.
- The highest split tensile strength was recorded for mixes with optimal proportions of hydraulic lime (20%-25%) and sodium silicate gel (30%-37.5%) under normal water curing.
- Wet hessian curing provided lower tensile strength compared to normal water curing.

3. Flexural Strength Test
- Objective: Evaluate the concrete's resistance to bending forces.
- Procedure: Performed on beam specimens (500 mm × 100 mm × 100 mm) as per IS standards.
- Results:
- Flexural strength improved due to the dense microstructure and reduced porosity achieved with sodium silicate gel activation.
- Mixes subjected to normal water curing exhibited higher flexural strength compared to those cured using wet hessian methods.

Key Observations
1. Sodium silicate gel acted as a chemical activator, enhancing hydration reactions between lime and fly ash, resulting in better mechanical properties across all tests.
2. Normal water curing consistently outperformed wet hessian curing in terms of compressive, tensile, and flexural strengths.
3. Optimal mix designs with hydraulic lime content between 20%-25% and sodium silicate gel between 30%-37.5% demonstrated superior performance.
, Claims:5. CLAIMS

1. The study demonstrates the utility of lime pozzolana concrete (LPC) activated by sodium silicate gel as an eco-friendly alternative to conventional cement-based concrete, significantly reducing CO₂ emissions associated with cement production.

2. The inclusion of sodium silicate gel as a chemical activator improves compressive, split tensile, and flexural strengths of LPC, meeting structural-grade requirements as per Indian Standards (IS codes).

3. The research identifies optimal proportions of hydraulic lime (20–25%) and sodium silicate gel (30–37.5%) for maximizing strength development, validated through 7- to 180-day curing tests.

4. Normal water curing outperforms wet hessian curing in strength development, providing practical guidance for field applications of LPC in construction.

: The use of fly ash (an industrial byproduct) and hydraulic lime promotes sustainable waste management and resource efficiency in concrete production.

1. Sodium silicate gel enhances the formation of calcium silicate hydrate (C-S-H) and calcium aluminate silicate hydrate (C-A-S-H) gels, reducing porosity and yielding a denser, more durable concrete matrix.

2. The developed LPC is suitable for heritage restoration, moderate-strength structural elements, and other construction applications requiring reduced environmental impact.

The study adheres to IS codes (e.g., IS 516:2021, IS 5817:1992), ensuring reproducibility and compliance with industry standards for concrete testing and performance.

is scalable for commercial production, offering a viable pathway for alkali-activated materials in the global construction industry.

The findings encourage further exploration of locally available pozzolanic materials and alternative chemical activators to broaden sustainable concrete solutions.

The proposed LPC system is readily applicable in construction projects seeking to reduce carbon footprints while maintaining structural integrity, aligning with global sustainability goals (e.g., UN SDGs).
Date: March, 2025