Effect of wet copper tailings on the performance of high-performance concrete

Abstract

The use of copper tailings (CTs) as an ingredient of concrete towards bulk utilization of this industrial waste attracted extensive attentions. Nevertheless, CTs are stored in tailing ponds in the state of wet conditions, the use of dry CTs as described in most studies may fail to meet the practical requirements in reusing CTs since the industrial drying of CTs is unaffordable. In this regard, this paper proposed to prepare high-performance concrete (HPC) using wet CTs as the replacement of fly ash. Three addition methods of CTs as the replacement of fly ash were investigated and compared on the performance of HPC, including the addition of dry CTs, pre-wetted CTs, and dry CTs plus additional mixing water. Experimental results revealed that HPC with pre-wetted CTs not only had similar fresh properties as the blank one, but developed less autogenous shrinkage and densified pore structure. The released water by CTs worked as internal curing water, contributing to the formation of more hydration products of cement and higher internal relative humidities. The compressive strength of the HPC is obviously higher by 5.4% at 3 days, and 9.6% at 7 days and 10.3% at 28 days compared with the blank one. In addition, the proposed technology also enjoys obvious economic and environmental benefits.