Flexural Strength of Crushed Rock Dust Concrete at Elevated Temperatures

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 hours using an electrically controlled furnace. The OPC replacement percentages are: 0% (C40), 10% (C41), 20% (C42), 30% (C43) and 40% (C44) 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. No visible cracks are observed on the beams specimens of C40 and CRD concrete beams, when exposed up to 400 oC. Both C40 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 C40 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 C40 and CRD concrete beams at elevated temperatures are found to be acceptable when exposed up to 400 °C.