Mechanical and durability properties of biochar concrete

Abstract

Cement production, which now accounts for over 7% of global CO2 emissions, could be a major roadblock to the Paris Agreement's goal of net-zero emissions by 2050. Greenhouse gas emissions during cement production arise from the processing of clinker where a large amount of fossil fuel is burnt for energy generation, and the remaining part comes from the energy it takes to get to the necessary high temperatures. Partial replacement of cement by residuals from agricultural industries is one of the key strategies to mitigate CO2 emissions and help promote sustainability. The objective of the present research work is to investigate biochar, prepared by pyrolyzing rice husk (RH) at 550 °C, as an alternate supplementary cementitious material (SCM). The physical and chemical properties of biochar were characterized using elemental analysis, scanning electron microscopy, thermogravimetric, and energy-dispersive X-ray spectroscopy. Compressive strength, flexural strength, water loss, permeability, and resistance to sulfate attack tests were used to investigate the mechanical and durability features of concrete containing varied concentrations of biochar. Chapelle test was conducted to determine the pozzolanic activity of the biochar. The results indicate that concrete containing 4% biochar improved compressive strength by 2.32%, flexural strength by 23.52%, and durability by 17.3% because the finer biochar particles have a packing effect resulting in the formation of a dense matrix.