International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 06 Issue: 01 | Jan 2019 www.irjet.net p-ISSN: 2395-0072 © 2019, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 804 A Combined use of Fly ash and Metakaolin as Supplementary Materials for Cement in Cement Concrete Vijay Singh Rawat 1 , R. Divahar 2 , Chimdi Gadafa 3 , Bhupender Singh Rawat 4 1,2,3 School of Civil Engineering & Architecture, Adama Science and Technology University, Adama. 4 Department of Civil Engineering, Aryabhatta College of Engineering and Research Center, Ajmer, Rajasthan, India. -------------------------------------------------------------------------***------------------------------------------------------------------------- ABSTRACT - Rapid infrastructure development worldwide augments the demand for concrete. Nowadays concrete is a basic component of the construction industry. Like concrete, consumption of cement also plays a vital role to meet the requirement of the construction industry. Due to excessive demand of cement-concrete and at same time scarcity of these important components of the construction industry, it is essential to find out alternative supplements of cement and concrete. In this regard, we have focused on partial alternative material of cement-concrete. Fly ash and Metakaolin were tested for their performance in the cement-concrete as a supplementary material. Concrete having 35 MPa Compressive strength was targeted in the experimental investigation. Mechanical properties like compressive strength, flexural strength, and split tensile strength have been taken into consideration for comparison of conventional concrete with modified concrete. The modified concrete was evaluated by using NDT like Rebound hammer test and USPV Test. Furthermore, a relation was developed between compressive strength and NDT for the aforementioned supplementary materials. Experimental results revealed that the compressive strength of modified concrete is better than conventional concrete. Among the various combinations tested, an admixture of Fly ash at 10% and Metakaolin at 30% was found to provide higher compressive strength. Key Words- Concrete, Metakaoline, Fly ash, NDT, Rebound hammer test, USPV test, Compressive strength, Flexural strength, Split tensile strength. 1. Introduction In the past few decades, demand for concrete is rapidly increasing at a faster pace in construction works such as construction of buildings, dams, highways, railway bridges, airports etc. Concrete is stone-like material obtained artificially by hardening of the mixture of cement, inert-aggregate materials (fine & course) and water in predetermined proportions [1]. When these ingredients are mixed they form a plastic mass which can be poured in suitable molds (forms) and set-on standing into a hard solid mass, as a result of exothermic chemical reaction between cement and water. All these ingredients are naturally available but the constant use of these natural additives has led to exhausting of the natural sources and results into global warming [8]. Therefore, the use of alternative and partial materials for concrete is becoming essential. The recycling of waste materials can be the possible solution to this challenge. As we know concrete is weak in tension but very strong in compression, therefore, the concrete specialists are trying to improve the compressive strength of concrete by using recycled materials and other naturally available minerals as a material. In this regard, various materials like blast furnace slag, Metakaolin, silica fume, fly ash, plastic aggregate, crushed clay bricks etc. have been demonstrated to be used as partial replacement of cement and aggregates, [9, 12]. The consistency of concrete decreases an increase in Metakaolin content without a change in compaction of concrete. Tensile and flexural strength have had lower impact compared to compressive strength. Furthermore, it has been observed that the modulus of elasticity of modified concrete slightly increased. It was also noticed that drying shrinkage and creep of concrete are reduced significantly [6, 21]. Various studies have shown non-destructive evaluation of concrete using Metakaolin as supplementary material. The mechanical properties of modified concrete were compared using NDT and destructive test. Metakaolin was used at 5%, 10%, 15% and 20%, and it was found that for 5% and 10% the compressive strength increased by 7% and 16.75% respectively and for 15% and 20% the compressive strength of modified concrete was 11.42% and 6%, respectively. Therefore, 10% Metakaolin was found to be effective in increasing the compressive strength. It was also observed that the fresh properties of concrete like workability increases with an increase in percentage of Metakaolin [1, 10, 15, 18]. Fly ash has also been demonstrated as a potential alternative for cement concrete. Recent researches on Fly ash have concluded the following important points- (1) it requires slightly more water than conventional concrete. (2) The compressive strength of modified concrete slightly decrease at 7-28 days but after 3 months it will be equal to or greater than