Experimental Study of Compressive Strength And Flexural Strength of Standard Concrete by Using Metakaolin as Mineral Admixture

This experimental study investigates the influence of metakaolin as a mineral admixture on the compressive strength and flexural strength of standard concrete (M-25). Metakaolin, a highly reactive pozzolanic material, was introduced as a partial replacement for cement by weight. Metakaolin is a valuable addition to many concrete mixes. It can improve the strength, durability, and resistance of concrete, making it a more versatile and sustainable material. Here are some of the key properties of metakaolin:


Introduction
Concrete is one of the most widely used construction material worldwide due to its versatility, affordability and durability ( Ref 6).However, the production of conventional concrete contributes significantly to CO2 emissions, posing environmental concerns ( Ref 7).Additionally, the depletion of natural resources like sand and gravel necessitates the exploration of sustainable alternatives.Enhancing the mechanical properties of concrete, such as compressive strength and flexural strength, has been a focal point of research to meet the increasing demands of the construction industry ( Ref 9).One promising approach to improve these properties is the incorporation of mineral admixtures into the concrete mix.Metakaolin, a highly reactive pozzolanic mineral obtained by calcining kaolin clay, is a popular choice as a mineral admixture in concrete.It exhibits several advantageous properties, including: • Improved strength: Metakaolin reacts with calcium hydroxide in concrete to form additional C-S-H gel, leading to enhanced compressive and flexural strength.• Increased durability: Metakaolin refines the concrete microstructure, densifying the matrix and enhancing resistance to water penetration, chloride ingress, and chemical attack.• Reduced CO2 emissions: Replacing a portion of cement with metakaolin reduces the overall clinker content, thereby lowering the CO2 footprint of the concrete.• Sustainable alternative: Metakaolin utilizes industrial waste (kaolin clay) and reduces reliance on natural resources like sand and gravel.When used in appropriate proportions by weight of cement, metakaolin can significantly enhance the performance of standard concrete.This study aims to investigate the effects of metakaolin on the compressive strength and flexural strength of standard concrete mix.The addition of metakaolin as a mineral admixture introduces several potential benefits.Metakaolin is known to enhance the pozzolanic reaction in concrete, leading to increased density and reduced porosity (Ref 12).This, in turn, can improve the mechanical properties, making the concrete more durable and resistant to cracking.Moreover, metakaolin can contribute to sustainability in construction by reducing the demand for cement, a material associated with significant carbon emissions ( Ref 14).In this experimental study, preparation of M-25 grade of concrete with varying percentages of metakaolin as a replacement for cement by weight.Compressive strength and flexural strength test will be conducted to assess the concrete's ability to withstand axial loads.These tests will be essential in understanding how metakaolin affects the mechanical performance of the concrete.The study's findings will contribute valuable knowledge towards the development of sustainable concrete with improved mechanical properties and reduced environmental impact.It will provide insights into the optimal replacement levels of cement with metakaolin for achieving desired performance characteristics, potentially paving the way for a more sustainable and ecofriendly construction industry.Coarse Aggregates -Angular shape machine crushed stone was used as aggregates for two different fractions i.e. 20 mm and 10 mm whose specific gravity is 2.85 and 2.82 respectively.Water -Potable tape water free from chemical substances and suspended particles was used for mixing of concrete and curing of concrete mix.Metakaolin -Metakaolin is a pozzolanic material that is formed by the calcination of kaolin clay, typically at temperatures between 600 and 850 degrees Celsius.Specific gravity of metakaolin is 2.6.for casting.Molds fill with concrete mix with metakaolin in varying proportion and compact it thoroughly by using a vibrating table to remove air voids.Placed the cube and beam molds in the curing chamber for 24 hours to cure the specimens and followed the curing procedures.After 7 and 28 days curing duration demolded cube molds carefully and test under compressive testing machine and after 28 days curing duration demolded beam molds carefully and test under flexural testing machine with center point loading method.From the above result it is observed that the metakaolin with 20% is mixed with concrete gives high strength after 28 days as compared to normal concrete

Conclussions
The experimental study investigated the compressive strength and flexural strength properties of M-25 grade of concrete by using metakaolin as a mineral admixture by weight of PPC 33 grade cement.The study was conducted by casting specimens with 0%, 10%, 20% and 30% replacement levels of metakaolin.
The methodology involved the collection of materials, casting of specimens, and testing and analysis of the properties of the concrete as per IS 10262:2019.Based on above study the outcomes are as follows: • The 7 and 28 days compressive strength of various mixes is shown in Graph 2, and the results are indicated in Table 8, that the compressive strength of metakaolin with 20% in concrete mix is high as compared to other percentages.• The 28 days flexural strength of various mixes is shown in Graph 3, and the results are indicated in Table 8, that the flexural strength of metakaolin with 20% in concrete mix is high as compared to other percentages.• The study concluded that the use of 20% of metakaolin as a partial replacement of PPC in concrete can increase its compressive strength by 5.34% and flexural strength by 1.02% as compared to conventional concrete.• Graph 4 and Graph 5 shows the 28 days compressive strength and flexural strength of different percentages of metakaolin with corresponding three values of every percent of metakaolin.Graph 4. 28 Days Compressive Strength Analysis Graph 5. 28 Days Flexural Strength Analysis In summary, the experimental study showed that the use of metakaolin as a mineral admixture in M-25 grade of concrete can improve its compressive strength, flexural strength and durability.The study also highlighted the importance of testing and analyzing the properties of concrete to determine the effects of mineral admixtures on its strength properties.

Research Gap
While the given research topic investigates the influence of metakaolin on the mechanical properties of concrete, there are potential research gaps that could be explored further: • Life Cycle Assessment (LCA): Conduct an LCA to compare the environmental footprint of metakaolin concrete with conventional concrete, considering factors like embodied energy, greenhouse gas emissions, and resource consumption.• Waste utilization: Explore the potential of using industrial waste products like rice husk ash or ground granulated blast furnace slag as partial replacements for metakaolin, promoting sustainable construction practices.

• Additional Points:
The study could benefit from a more detailed literature review to identify existing research gaps and avoid redundancy.o Consider incorporating numerical modeling techniques like finite element analysis (FEA) to validate the experimental findings and predict the behavior of metakaolin concrete under different loading conditions.o Emphasize the practical implications of the research findings and provide recommendations for the potential implementation of metakaolin concrete in construction projects.By addressing these research gaps, the study can contribute valuable insights into the effectiveness of metakaolin as a mineral admixture and promote its wider adoption in the construction industry for sustainable and high-performance concrete applications.

Acknowledgement
The satisfaction and euphoria of the successful completion of any task would be incomplete without the mention of the people who made it possible whose constant guidance and encouragement crowned our effort with success.It gives me enormous pleasure to express my most profound sense of gratitude and sincere thanks to my highly respected guide, PROF.ANUBHAV RAI, Head, Department of Civil Engineering, Gyan Ganga Institute of Technology and Science for their valuable guidance, supervision, and encouragement throughout my work, which made this task pleasant.

Figure 1
Figure 1.Metakaolin Powder Volume of Cement = Cement Content /(Specific Gravity of Cement x 1000) = 0.135m 3 Volume of water = Water Content /Specific gravity of water x 1000 = 0.178 m 3 Volume of Mineral Admixture = Mass of admixture/Specific Gravity X 1000 = 0.000 m 3 Volume of all in one Aggregate = Cl 1-Cl 2-Cl 3-Cl 4-Cl 5 = 0.677 m 3 Mass of 20 mm aggregate=Cl 6 x Ratio of blending proportion x ratio of Coarse aggregate x Specific Gravity x 1000 = 637.15kg Mass of 10 mm aggregate = Cl 6 x Ratio of blending proportion x ratio of Coarse aggregate x Specific Gravity x 1000 = 515.82kg Mass of Sand =Cl 6 x ratio of Fine aggregate x Specific Gravity x Blending x 1000 = 707.27kg

Table 6 -Grading of Fine AggregateTable 7 -Test Results for Fine Aggregate • Mix Proportions o Target Mean Strength of Mix Proportion
S.

. Homogeneous and cohesive concrete mix. 2. Achieved specified strength in 07 & 28 days. S.No. Ingredients Quatity of Material per m 3 in SSD Condition in kg Ratio Material Required for mix per bag of cement in kg 1.
3. The mix proportion for M-25 concrete mix with 20% replacement of PPC by metakaolin is 1:2.16:3.52 4. The mix proportion for M-25 concrete mix with 30% replacement of PPC by metakaolin is 1:2.42:3.933.Specimen PreparationCube molds of size 150mmx150mmx150mm and beam molds size 150mmx150mmx700mm are prepared