Residual stress-strain relationship for the biochar-based mortar after exposure to elevated temperature

The effects of elevated temperature on the compressive strength and stress-strain behaviour of biochar-based mortar were investigated in this research. A total of 39 cylindrical (100 × 200 mm) specimens were prepared with four mortar mixtures by replacing 0%, 5%, 10 % and 20 % of cement weight with biochar. The specimens were cured for 28 days and exposed to elevated temperatures of 200 °C, 450 °C and 700 °C before testing. Results show that increasing replacement rate of biochar reduces the compressive strength at room temperature as well as residual strength after being exposed to elevated temperature. The 5% weight of cement replaced by biochar performed better than other specimen at elevated temperature as it retains about 88 %, 76 % and 38 % of compressive strength, respectively after being exposed to 200 °C, 450 °C and 700 °C. The study also established the relationship among biochar mix ratio, elevated temperature, elastic modulus and peak compressive strength. Finally, a new stress-strain model was developed and validated to predict the axial behaviour of biochar-based mortar with varying biochar mix ratio and elevated temperature. This model can be used to predict the post fire mechanical behaviour of biochar-based mortar.