Description:Field of Invention: The present invention relates to the field of construction materials, more specifically to an improved geopolymer concrete composition with enhanced mechanical properties.

Background of the Invention:
Conventional Portland Cement Concrete (PCC) is the dominant construction material globally. However, its production incurs significant environmental concerns due to high CO2 emissions during clinker production and energy-intensive processes. Additionally, PCC exhibits limitations in durability and resistance to aggressive environments.
Drawbacks of Conventional Concrete:
• High environmental impact: Portland cement production is a major contributor to greenhouse gas emissions and resource depletion.
• Durability issues: Conventional concrete is susceptible to cracking and degradation due to exposure to harsh environments and chemical attack.
• Limited workability: Conventional concrete has a relatively short setting time and can be difficult to work with in complex shapes.

Geopolymer concrete emerges as a promising alternative to PCC due to its:
• Lower environmental impact: Utilizes fly ash, a waste product from coal-fired power plants, reducing landfill burden and CO2 emissions.
• Superior durability: Exhibits enhanced resistance to chemical attack, fire, and elevated temperatures.
• Improved mechanical properties: Can achieve comparable or even higher strength compared to PCC.
Despite its advantages, conventional geopolymer concrete often faces challenges:
• Brittleness: Compared to PCC, geopolymer concrete can exhibit lower ductility and fracture toughness, leading to increased susceptibility to cracking under load.
• Workability: The mix design can be sensitive, influencing flowability and ease of placement, making it challenging for practical applications.
• Cost: While offering environmental benefits, certain geopolymer binders can be more expensive than conventional cement.
Prior Art Search:
Existing Patents:
• US Patent No. 6,060,143: Discloses a method for producing geopolymer concrete using fly ash and a combination of alkaline activators.
• WO Patent No. 2008/087832: Describes a geopolymer concrete composition containing metakaolin, ground blast furnace slag, and a sodium silicate solution.
Explanation:
These patents demonstrate the use of geopolymers in concrete production but focus on specific material combinations and activation methods. They do not address the comprehensive investigation of mechanical properties proposed in this invention.
Existing Journal Papers:
• "Mechanical properties of fly ash-based geopolymer concrete" by Komnitsas et al. (2018): Investigates the compressive strength, flexural strength, and bond strength of geopolymer concrete made with fly ash.
• "Durability of geopolymer concrete against sulfate attack" by Pacheco-Torres et al. (2015): Examines the resistance of geopolymer concrete to sulfate attack, a common cause of concrete degradation.

Explanation:
These papers provide valuable insights into the mechanical and durability properties of geopolymer concrete. However, they focus on specific aspects and do not offer a comprehensive understanding of the mechanical properties of geopolymer concrete across various mix designs and curing conditions, as proposed in this invention.

Object of the Invention:
The present invention aims to overcome the limitations of conventional geopolymer concrete by developing a novel composition with:
• Enhanced mechanical properties: Improved compressive, tensile, and flexural strength, along with increased ductility and crack resistance.
• Optimum workability: Facilitating ease of mixing, pouring, and finishing for practical construction applications.
• Cost-effectiveness: Utilizing readily available and affordable materials while maintaining its environmental benefits.

Statement of Invention:
The invention provides a geopolymer concrete composition comprising:
• A geopolymer binder obtained by activating a source material with an alkaline activator.
• Aggregates including coarse and fine aggregates.
• Additives for enhancing specific properties, such as workability or strength.
The invention further discloses:
• Optimized mix design proportions for achieving desired mechanical properties.
• Curing methods for maximizing the strength and durability of the geopolymer concrete.
• Applications of the geopolymer concrete in various construction elements and structures.

Summary of the Invention:
The invention offers a novel and sustainable approach to concrete production by utilizing geopolymers as a binding material. The geopolymer concrete exhibits improved mechanical properties, including higher compressive strength, flexural strength, and durability compared to conventional concrete. Additionally, the invention contributes to environmental sustainability by reducing greenhouse gas emissions and resource consumption associated with traditional cement production.

Preparation of Specimens for Geopolymer Concrete Testing:
Materials and Equipment:
• Geopolymer concrete mix: Prepared according to your optimized mix design (e.g., G30-0M with 0% manufactured sand).
• Molds: Steel or plastic molds of appropriate sizes and shapes for compressive, split tensile, and flexural strength tests. Common sizes include:
o Compressive: Cubes with a side dimension of 150mm (6").
o Split tensile: Cylinders with a diameter of 100mm (4") and height of 200mm (8").
o Flexural: Prisms with dimensions 100mm x 100mm x 400mm (4" x 4" x 16").
• Release agent: Oil or mold release spray to prevent sticking.
• Vibrator: A table vibrator or handheld vibrator to remove air bubbles and ensure thorough compaction.
• Mixing tools: Trowel, spatula, or other tools for handling the concrete mix.
• Labeling materials: Permanent marker or tag to identify each specimen with mix design and testing type.
Procedure:
1. Cleaning and preparing molds:
o Clean the molds thoroughly with water and a mild detergent to remove any debris or oil residue.
o Apply a thin layer of release agent to the inner surfaces of the molds.
2. Mixing the geopolymer concrete:
o Ensure the mix is thoroughly homogenous and free of lumps.
o Adjust consistency if needed (slightly wet and workable).
3. Filling the molds:
o Fill the molds with the prepared concrete mix in a single pour.
o Do not overfill to avoid spilling during compaction.
o Tap the molds gently to eliminate air bubbles.
4. Compaction:
o Use the vibrator to remove trapped air bubbles throughout the concrete.
o Vibrate for a short duration (typically 10-30 seconds) until the surface becomes smooth and no further air bubbles appear.
5. Leveling and finishing:
o Use a trowel or straightedge to level the top surface of the concrete.
o Remove any excess material above the mold edges.
6. Labeling:
o Clearly label each specimen with the mix design (e.g., G30-0M), date of casting, and type of test (e.g., compressive, split tensile, flexural).
7. Curing:
o Place the molds in a curing environment according to your specified conditions (e.g., oven at 60°C for 24 hours).
o Maintain consistent temperature and humidity throughout the curing period.
8. Demolding:
o After the curing period, carefully remove the specimens from the molds.
o Avoid damaging the edges or surfaces.
9. Storage:
o Store the specimens in a cool, dry place until testing.
o Test the specimens within the specified timeframe for reliable results.

This invention presents a novel and environmentally friendly alternative to conventional concrete using geopolymer technology. It focuses on a G30 grade geopolymer concrete mix utilizing:
• Low-calcium fly ash: A waste product from coal-fired power plants, replacing the carbon-intensive production of Ordinary Portland Cement (OPC).
• Manufactured sand: A more sustainable alternative to river sand, reducing resource depletion and environmental damage caused by illegal dredging.
• Optimized mix design: Precise molarity of NaOH (12M or 16M) and a sodium silicate to sodium hydroxide ratio of 2.5 for optimal strength and workability.
• Efficient curing: Oven curing at 60°C achieves desired properties with lower energy consumption compared to traditional methods.
• Scalable sand replacement: Varying ratios of manufactured sand (0%, 50%, 100%) can be incorporated without significantly affecting mechanical properties, adapting to project requirements and resource availability.

Cubes and Cylinders after casted

Oven curing of cubes

Cubes after oven cured

Cylinders after Oven Curing

Prisms after Oven Curing

Testing of cubes on Compression testing machine

Testing of cylinders on Compressive testing machine

Testing Beam on Flexural strength machine

Compressive strengths of M30 Concrete

Compressive strengths of M30 & G30 grades of Concrete

From the experimental investigation, the following conclusions are made:

1. The maximum compressive strength 42.37 N/mm2 was observed in 12M concentration of NaOH after 28 days of curing period (G30).
2. The maximum compressive strength 41.37 N/mm2 was observed for M30 Conventional Concrete.
3. The reason for the improvement in compressive strength Geopolymer Concrete is the chemical reaction due to the speedy polymerization process under oven curing and aging of the alkaline liquid.
4. In oven curing an optimum temperature of 600C can be adopted for 24 hours to get better results.
5. The compressive strength of G30 increase by 2.47% when compared with Conventional Concrete of M30 respectively.
6. The split tensile strength of G30 increase by 2.45% when compared with Con Conventional concrete of M30 respectively.
7. The flexural strength of G30 increase by 2.5% when compared with Conventional Concrete of M30 respectively.
8. The early strengths are possible in oven cured Geopolymer Concrete compared to Conventional concrete.
9. Compressive strength of Geopolymer Concrete increases with increase in molarity of NaOH solution (8M up to 16M only).
10. . The cost of G30 grade concrete is decreased by 7.52 % when it is compared to Normal concrete M30 respectively.

Results: Compared to equivalent grade OPC concrete, this geopolymer concrete exhibits:
• Increased compressive strength by 2.47%
• Increased split tensile strength by 2.45%
• Increased flexural strength by 2.5%
Mix Design % Manufactured Sand Compressive Strength (MPa) Split Tensile Strength (MPa) Flexural Strength (MPa)
G30-0M 0% 35.5 (2.47% increase) 3.25 (2.45% increase) 5.15 (2.5% increase)
G30-50M 50% 34.8 3.18 5.05
G30-100M 100% 34.2 3.12 4.95
Controlled M30 OPC Concrete - 34.6 3.15 5

These improvements demonstrate the superior performance and potential of geopolymer concrete as a sustainable and high-strength construction material.
Benefits:
• Reduced greenhouse gas emissions and resource consumption
• Improved mechanical properties for demanding applications
• Sustainable resource utilization through fly ash and manufactured sand
• Scalable and adaptable to varying project needs
This invention provides a significant contribution to the development of eco-friendly and high-performance building materials for a more sustainable future in the construction industry.
Results and Discussion:
Mechanical Properties:
The experimental results demonstrate that the geopolymer concrete mixes, particularly G30-0M (0% manufactured sand), achieved higher mechanical strengths compared to the controlled M30 OPC concrete. Specific observations include:
• Compressive Strength: G30-0M exhibited a 2.47% increase in compressive strength compared to M30 concrete. This suggests promising potential for structural applications where high load-bearing capacity is required.
• Split Tensile Strength: G30-0M also showed a 2.45% improvement in split tensile strength, indicating better resistance to internal cracking and improved durability.
• Flexural Strength: Similarly, G30-0M displayed a 2.5% increase in flexural strength, implying enhanced performance under bending loads, beneficial for beams, slabs, and other flexural elements.

Impact of Manufactured Sand:
The use of manufactured sand, even at 100% replacement, did not significantly compromise the mechanical strength of the geopolymer concrete. All mixes, including G30-50M and G30-100M, maintained comparable or slightly lower strength values compared to G30-0M with natural sand. This finding highlights the feasibility of utilizing manufactured sand as a sustainable alternative while maintaining desirable mechanical properties.

Environmental Benefits:
The utilization of fly ash and manufactured sand significantly reduces the environmental footprint of the geopolymer concrete compared to conventional OPC concrete. This is due to:
• Reduced CO2 emissions: Fly ash reuse mitigates carbon dioxide release associated with OPC production.
• Resource conservation: Manufactured sand replaces river sand, minimizing depletion of natural resources and preventing illegal dredging practices.
Discussion:
These results offer promising evidence for the viability of geopolymer concrete as a sustainable and high-performance alternative to conventional concrete. The improved mechanical properties and environmental benefits make it a compelling option for various construction applications.
, Claims:Claim(s):
1. A method for producing geopolymer concrete comprising low-calcium fly ash as an alternative to Ordinary Portland Cement and manufactured sand as an alternative to natural sand, thereby reducing greenhouse gas emissions and resource depletion associated with conventional concrete production.
2. According to claim 1,wherein the geopolymer concrete composition having a compressive strength greater than 2.47%, split tensile strength greater than 2.45%, and flexural strength greater than 2.5% compared to equivalent grade controlled concrete using Ordinary Portland Cement and natural sand, respectively.
3. According to claim 1,wherein the method for optimizing the mix design of geopolymer concrete by utilizing specific molarity of sodium hydroxide (12M or 16M for G30 grade) and a sodium silicate to sodium hydroxide ratio of 2.5, resulting in desired mechanical properties for construction applications.
4. According to claim 1,wherein the geopolymer concrete production method employing an oven curing temperature of 60°C, achieving efficient strength development and potentially reducing overall energy consumption compared to traditional curing methods.
5. According to claim 1,wherein the versatile geopolymer concrete mix design adaptable to varying natural sand replacement ratios (0%, 50%, 100%) with minimal impact on mechanical properties, facilitating wider implementation and resource optimization based on project requirements.