Effects of Elevated Temperatures on Microwave Incinerated Rice Husk Ash blended Concrete

Concrete subjected to rapid heating at high temperatures causes spalling of
concrete. Spalling occurs when the tensile stress due to the pore pressure exceeds the
tensile strength of concrete. Agricultural waste such as rice husk ash (RHA) is disposed
through open burning. This contributes to elevating air pollution problems and causes
respiratory diseases. This research studies the possibility of using RHA as a partial
replacement for cement in concrete subjected to elevated temperatures, hence
simultaneously providing a solution for spalling and air pollution problems. The objective
of this study is to evaluate MIRRA as a supplementary cementitious material with
reference to strength of hardened concretes and identify the optimal level of replacement
of cement to improve concretes resistance to elevated temperatures. Tests were conducted
on normal and RRA blended concrete. This included tests on compressive strength, fire
resistance, Ultrasonic-Pulse Velocity and Scanning Electro-optic Microscope. Results
show that MIRRA at 800°C with 5% partial replacement of OPC is the optimum mix
proportion that maximizes concretes resistance to elevated temperatures.