Incorporation of biochar in cementitious materials: A roadmap of biochar selection

Abstract Increasing cement production in construction sector and waste generation in industrial sectors are of the major sources of CO2 emission. For decades, it has been the concern of environmentalists to convince constructors and researchers to find sustainable solutions targeting aforementioned problems. The attempts focused on identification of wastes to be successfully complied with construction materials. Biochar has recently received attention due to several environmental and technological advantages, shortly include carbon sequestration, low thermal conductivity, chemical stability and low flammability. For this reason, biochar is recognized as an efficient candidate for cement or lightweight aggregates replacement in building materials. Biochar addition could result in a reduction of capillary absorption in mortar paste. Besides, its addition accelerates cement hydration and restricts shrinkage cracking in cement mortar. The present review categorizes all the biochar critical features affecting the performance of cementitious materials. The effect of biochar addition as filler and cement replacement on the workability, hydration, mechanical and transfer properties of cement paste/composites is reviewed in this paper. From the data collection, an optimum biochar content around 2% is shown to contribute to the improvement of mechanical properties. The gaps in the literature are identified and the future research plans are proposed.