Comparison of compressive strength of aerated concrete and ordinary concrete, under high temperature based on XRD and SEM test, for use in offshore structures

In recent decades, the use of aerated concrete in offshore structures has been considered by researchers due to its superior properties of mechanical properties and thermal resistance compared to ordinary concrete. In this laboratory research, a mixing plan was made of ordinary concrete with a cement grade of 450 kg/m3. A mixing design was also made of fermented concrete based on composite kiln slag to compare and evaluate the compressive strength of concrete under ambient temperature and temperature of 500 °C, at a 90-day curing age. Following X-ray diffraction (XRD) spectroscopy and scanning electron microscopy (SEM) images at 90 days of processing age at ambient temperature and 500 °C to evaluate the microstructure and verification of compressive strength test results on samples Concrete was done. The results show that the compressive strength at ambient temperature is 62.43 MPa for ordinary concrete and 68.03 MPa for mild concrete, which have a difference of about 9%. By applying heat to concrete samples, the rate of compressive strength drop in conventional concrete was 37.7% and in quilted concrete was 16.4%. The results of XRD and SEM tests were coordinated with each other and overlapped with the results of compressive strength test at ambient temperature and high temperature.