Properties of copper slag concrete

Abstract

This report investigated the mechanical properties of high strength concrete incorporating copper slag as fine aggregates. The rising need for alternative fine aggregates substitution of sand is essential due to its high materials cost and the emphasis on sustainable concrete. Copper slag which is a by-product of copper metal extraction process has been selected as the fine aggregate substitution in high strength concrete production.

The workability and strength properties of the concrete with sand replaced by copper slag at an incremental of 20% by weight were assessed through a series of controlled test to determine the optimum content of copper slag replacement. Slump, compression, flexural and tensile splitting tests were carried out on 6 different mix proportions. Results indicated an increase in workability as more copper slag is added, while strength and durability of the concrete showed a reverse trend. The dynamic strength of the concrete evaluated through the Split Hopkinson Pressure Bar test peaks at 20% copper slag replacement after which it reduces as more copper slag is added. This was due to the increased free water content which although makes the concrete more workable but results in porous concrete microstructure.

As such, a conclusion was made that the replacement of copper slag is beneficial up to 30% as the workability is increased significantly by 83% compared to the control mix, while keeping the compressive strength decrease to 5%. The dynamic compressive strength is also increased by 8%. This is an important in high-rise building construction where it is necessary for the concrete mix to be workable while maintaining the low water /cement ratio essential for high strength gain.