Effect of elevated temperatures on the flexural strength of crushed rock dust concrete

Abstract This experimental study presents the effect of partial replacement of Ordinary Portland Cement (OPC) by crushed rock dust (CRD) as filler material on the flexural strength of concrete when subjected to elevated temperatures of 200 °C, 400 °C, 600 °C and 800 °C for duration of 2 h using an electrically controlled furnace. The OPC replacement percentages are: 0% (T20), 10% (T21), 20% (T22), 30% (T23) and 40% (T24) by weight. Ultrasonic pulse velocity (UPV), Mass loss, flexural strength, and scanning electron microscope (SEM) are evaluated at the targeted elevated temperatures. At ambient temperature, up to 40% CRD, a dense microstructure with less pores is observed using SEM micrographs. Both T20 and CRD concrete beams begin to crack when temperature reached to 600 °C and pronounced surface cracks are observed at 800 °C. UPV values obtained with T20 and CRD concrete beams at elevated temperatures are in good agreement with flexural strength and mass loss values. SEM micrographs signify the use of CRD in concrete at elevated temperatures. The results of T20 and CRD concrete beams at elevated temperatures are found to be acceptable when exposed up to 400 °C.