Effect of fly ash on compressive strength of concrete containing recycled coarse aggregate

Abstract

The recycling technology must be adopted in concrete construction work in Indonesia. The using of recycling coarse aggregate in construction work included an effort in recycling technology. It would reduce the usage of natural coarse aggregate and would reduce the material cost. In this research the natural coarse aggregate is replaced with recycled coarse aggregate. Fly ash needed as material addition to improve concrete quality. The purpose of this research is to know the effect of the using percentage of recycling coarse aggregate, the percentage of fly ash and water-cement ratio to the compressive strength of concrete. The method used was an experimental laboratory. Concrete specimens are cylinder 15 cm in diameter and 30 cm in height. Water-cement ratios of concrete mixtures 0.4, 0.45 and 0.5. The specimens are cast using natural coarse aggregate and replacing coarse aggregate with 20%, 40%, and 60% recycled coarse aggregate. Concrete specimens are tested after curing at 28 days. Compressive strength results are then used for multiple linear regression by using SPSS version 22 software to get an empirical formula between the compressive strength and percentage of recycled coarse aggregate, the percentage of fly ash and water-cement ratios. Results analysis shows that recycled coarse aggregate can be used until 30 % with fly ash addition 10 %. Reducing in the usage of natural aggregate and cement is suitable with the effort of the environmental conservation.