Effective Utilization of Fly Ash and Waste Gravel in Green Concrete by Replacing Natural Sand and Crushed Coarse Aggregate

The present study was carried out to find out the effect on properties of concrete wherein crushed coarse aggregate (CCA) was replaced by waste gravel (WG) and fine aggregate by fly ash. The whole study was divided into two phases. In the first phase, CCA was replaced by WG in the proportions namely 30%, 50%, 80% and 100% by weight of CCA keeping fine aggregate (natural sand) common in all the mixes. In the second phase fly ash was used to partially replace natural sand in that proportion of CCA and WG which had highest compressive strength. Fly ash was used to replace natural sand in proportions of 30%, 50% and 80% by weight of natural sand. Concrete M15 and M20 grades were prepared. A total of 336 specimens were cast and tested after 7 and 28 days of curing. The study concluded that compressive strength, split tensile strength and flexural strength of concrete improved by using WG proportion up to 80% and then decreased when 100% WG were used. The highest strengths were obtained for 50% replacement of CCA by WG. The study also concluded that compressive strength, split tensile strength and flexure strength of concrete improved for all the percentage replacements of natural sand with fly ash. Finally, it could be concluded and recommended that WG and fly ash could be effectively utilized as coarse & fine aggregate in all green concrete applications like precast kerbstones and concrete hollow/solid blocks and other products. (C) 2017 Elsevier Ltd. All rights reserved.