RECYCLED COARSE AGGREGATE (RCA) FOR ROLLER COMPACTED CONCRETE PAVEMENTS

Abstract

Roller-compacted concrete (RCC) is a zero slump concrete, consists of ingredient same as of conventional concrete like dense-graded aggregates, Portland cement and water. The RCC is placed with bituminous paver and compacted with vibratory roller. It achieved a high density which subsequently results in a high-strength and durable concrete pavement. The topic of this research is the replacement of natural aggregates by recycled coarse aggregates (RCA) in the composition of the RCC. Since the quality of RCC degraded by partial replacement of natural aggregate with RCA due to its poor quality. Hence a study has been conducted to enhance the strength characteristics of RCC using low cost mineral admixtures like fly ash and wollastonite. The RCC Mix design was produced using soil compaction method. Mix were prepared using cementitious materials of 12%, 14% and 16% and optimum water content was found out for each mix by plotting graph between density and water content. Optimum water content of 7% was obtained for 14% cementitious content and it gave a compressive strength of 31 MPa, which is quite sufficient for RCCP, hence adopted as control mix. To study the effect of partial replacement of cement with Fly ash and Wollastonite on RCC, concrete was produced with the replacement of cement with fly ash and wollastonite at the level of 0%, 10%, 15%, 20%, 25% and 30% by mass of total cementitious materials. Concrete cube, prism specimens were prepared by vibration until complete compaction obtained. The compressive and flcxural tests were carried out to find out mechanical properties of RCC without and without using mineral adniixtiire. On the basis of results it was observed that cement can be replaced by fly ash and wollastonite by 1 5% anti 20% respectively in order to improve the mechanical strength. Now the natural coarse aggregate was rcplaccd with RCA at the level of 0%, 30%, 50% and 70% and it was observed that 3 days. 7 days and 28 days compressive and flexural strength parameters dccrcscs hy increasing RCi\ rcpiacc.iner:t. To improve the strength of RCC with RCA, mineral admixture i.e. fly and wollastonile were used. i\ significant improvcmcnt of 6-I 0/ was observed in the RCC coiiprcssi\'c an:i flcxural strength by using these mineral admixture with RCA w.r.t. using RCA only.