Properties of pavement quality concrete and dry lean concrete with copper slag as fine aggregate

Abstract

The work reported in this paper is based on a laboratory study carried out to investigate the feasibility of using copper slag, a by-product of copper refineries, as a partial replacement of sand in the preparation of pavement quality concrete (PQC) and dry lean concrete (DLC) mixes. A control mix for PQC was prepared with 400 kg/m3 of ordinary Portland cement (OPC) and water–cement (w–c) ratio of 0.40. Other concrete mixtures were then prepared by substituting 20%, 40%, 60%, 80% and 100% copper slag in control mix. Workability and bleeding of green concrete, compressive strength, flexural strength at 7 and 28 days, drying shrinkage and abrasion resistance were measured for all the concrete mixtures. DLC mixtures were designed with 150 kg/m3 of OPC and different blends of stone dust with 20%, 40%, 60% and 80% copper slag as fine aggregate. DLC mixes were then prepared with different water contents with a view to find out the optimum water content for achieving maximum density, and corresponding compressive strength at 7 and 28 days for each blend of stone dust and copper slag. The laboratory test results showed that the compressive strength of PQC 7 and 28 days was not affected by inclusion of any content of copper slag as fine aggregate in the concrete mixture. Small gradual increase in flexural strength at 28 days was observed with an increase in copper slag content. Drying shrinkage of PQC decreased with the increase in slag and the decrease in stone dust content. Abrasion resistance of concrete mixes containing slag was observed to be less as compared with that of non-slag concrete. Compressive strength of DLC decreased with the increase in copper slag content beyond 40%. Keeping in view the strength and other important requirement of PQC such as cohesiveness, segregation, finishing, texturing, shrinkage and abrasion resistance, it was concluded that a blend of stone dust with copper slag content up to 40% could be used as fine aggregate for PQC as well as DLC.