Journal of Scientific & Industrial Research Vol. 76, October 2017, pp. 644-653 Strength, Durability, and Micro Structural Properties of Concrete Incorporating MS and GCBA as Sand Substitute M P Kadam 1 * and Y D Patil 2 *1 Civil Engineering Department, NDMVP’S College of Engineering Nashik, India 2 Applied Mechanics Department, SVNIT- Surat, India Received 17 December 2015; revised 22 October 2016; accepted 15 July 2017 In this experimental study, GCBA (Graded coal bottom ash) from Eklahare thermal power station, Nashik was used, as sand substitute with micro silica (MS) in concrete. Concrete specimens were casted by substituting GCBA with sand in different proportions (40 to 100%). for each substitution of GCBA, micro silica (MS) was added at 2 to 8% by weight of cement used in reference mix. The fresh and hardened properties of GCBA were studied along with the micro structural analysis (SEM) at 7, 28 and 56 days. It was observed that the workability of fresh concrete was considerably increased with increase in MS but was less than reference concrete. The all hardened properties of concrete such as compressive strength, flexural strength, split tensile strength, density, modulus of elasticity and permeability were observed more than reference concrete up to 90% substitution by GCBA with 8% MS whereas for 100% substitution with 8% MS was marginally reduced in strength compared with reference concrete. Keywords: GCBA (Graded Coal Bottom Ash), MS (Micro Silica), SEM, Concrete Introduction Cement concrete is one of the seemingly simple but composite and most widely used construction material in the world today. Many of its complex behaviors are yet to be identified to employ this material constructively and reasonably. It is hard to point out another material of construction which is as flexible as concrete. In today’s modern world, the construction industry is rapidly growing, which involves the use of natural resources, such as sand, to develop the infrastructure. This growth is affected by the lack of availability of good quality sand as natural resources. Disposing huge quantity of coal bottom ash generated from a large consumption of coal is one of the greatest environmental concerns in India. Coal bottom ash can be used in concrete as a sand substitute material either partially or fully 1 . In the past several decades, the utilization of such industrial waste materials for substitute of sand in the preparation of concrete has contributed to superior properties in comparison with that of conventional concrete in terms of strength, performance, and durability 2 . As sand is the main constituent in concrete that is obtained from natural resources, its use adversely affects the environment. Such huge utilization of natural sand in concrete depletes the natural resources as well as it contributes to the problem of industrial waste disposal worldwide and especially in India. Several researchers have reported the effective utilization of industrial waste in concrete as a substitute for sand that exhibited better properties than the conventional concrete 3,4 . Jaturapitakkul and Cheerarot 5 conducted detailed investigations of utilization of bottom ash in mortar and reported higher water requirement than that for cement mortar. In addition, they reported that ground bottom ash concrete with higher cement content had higher development rate of compressive strength with the concentration of the cementitious material of 260–440 kg/m 3 . The research work carried out by Syahrul et al. 6 showed that to obtain a complimentary strength, 30% is the optimal concentration of washed bottom ash as a sand substitute whereas Kasemchaisiri and Tangtermsirikul 7 showed that the optimum substitute percentage of bottom ash was 10% by weight of the total fine aggregate in self-compacting concrete. Bai et al. 8 reported that for fixed w/c ratio, slump decreased with increase in bottom ash with decrease in compressive strength. In summary, the reviews of literature discussed earlier indicate that up to 30% there can be an optimum utilization of bottom ash as —————— * Author for Correspondence E-mail: kadammadhavp@gmail.com