STRATEGIES FOR OPTIMIZING THE BIOCHAR CONTENT OF WOOD CHIPS, PEANUT SHELLS, AND RICE HUSKS IN CEMENTITIOUS MATERIALS

The characteristic GHG emissions from cement production, primarily due to decarbonation and fossil fuel consumption, are deeply concerning. Reducing the clinker content in cement is the fastest way to lower the carbon footprint, particularly through the addition of biochar. This promising approach is the subject of several studies. However, numerous factors come into play, ranging from the type of biomass used to the curing of the material. This is, in fact, the source of the diversity in results and the resulting contradictions. The common thread among these studies remains the negative impact of high biochar content. This review article aims to demonstrate the importance of certain pyrolysis parameters on the properties of biochars, but above all to highlight the levers that could enable an increase in biochar content in cementitious materials while preserving mechanical and durability properties. In the literature, the beneficial effect of biochars on mechanical properties, dry shrinkage, crack resistance, reduced water absorption, etc., is only significant when the biochar content is less than or equal to 1%. The porous nature of biochar, which is both beneficial and detrimental, limits the amount of biochar that can be added to or substituted for cement. However, alternatives such as pretreatment and accelerated carbonation hardening allow for additions of up to 5% or even 10%. This review summarizes the individual factors (biochar fineness, pretreatment, accelerated carbonation, etc.) that facilitate biochar incorporation. Unlike existing studies that treat these factors separately, we recommend a standardized protocol that combines them to achieve a high biochar content without compromising strength and durability.