Engineering properties of concrete made with slate waste

This paper reports on the engineering properties and microstructure of concrete incorporating slate waste aggregates generated from roofing slate production in the UK. Various concrete mixtures were designed using different sizes of slate waste as aggregate replacement. Concrete produced with limestone aggregate was used as control. The results showed that concrete produced with limestone aggregate tended to fail predominantly through the interfacial zone between the aggregate surface and the cement paste and mortar, without any observed aggregate fragmentation. In contrast, the concrete made with slate waste aggregate showed signs of failure emanating from both the interfacial zone as well as from the cracking and subsequent fragmentation of the aggregates. The findings show that the concrete made with slate waste aggregates attained compressive strength of 25–30 N/mm2, splitting strength of 2–3 N/mm2 and elastic modulus of 25–32 kN/mm2 thus indicating potential for using slate waste as a replacement for limestone aggregate in most low- to medium-strength engineering applications