Post-heating evaluation of fibre reinforced concrete with LC3 binder as replacement to OPC

Abstract

Limestone calcined clay cement (LC3) is an emerging cement that uses reduced clinker content in production, leading to a sustainable future by reducing CO2 emissions. Compared to OPC, LC3 has performed well under normal conditions. But the residual strength of LC3 binder concrete can differ from that of OPC-based concrete at high temperatures. This experimental study highlights the effect of elevated temperature, various cooling conditions and inclusion of fibres (PPF, SF, HF) on the physical properties such as colour change, crack width, mass loss and residual compressive strength of concrete monitored using both NDT techniques and destructive testing. NDT comprised rebound hammer and UPV test carried before and after cooling heated samples. After compression testing, X-ray diffraction was used to determine the samples' microstructure and phase shift (XRD). Test results show that the compressive strength and mass loss increased significantly after exposure to 200 °C due to further hydration of un-hydrated clinkers. The performance decreased sharply after 600 °C exposure due to the decomposition of hydration products. Steel fibre had a beneficial effect, but PP fibre, due to balling, reduced concrete compressive strength. At all exposure temperatures, water quenching significantly decreases compressive strength. This reduction can be attributed to micro-crack formation caused by high thermal stress.