Traditional concrete, while a versatile and ubiquitous construction material, comes with a hefty environmental price tag. Cement is a crucial component of concrete which accounts for an astonishing 8% of worldwide carbon dioxide emissions. Biochar-based concrete is an emerging technology that promises to revolutionize the construction industry with its sustainable and resilient approach. This research examines the application of treated rice husk ash (RHA) in mortar and its impact on mechanical properties. It delves into the potential of RHA as an eco-friendly and sustainable material, responding to increasing concerns about waste management and the demand for innovative construction approaches. The experimental methodology involves various percentages of replacement of cement with RHA, viz. 5 and 10% with w/c ratio 0.4–0.5 at different temperatures varying from room temperature (RT) and in the variation of 50 ℃, i.e., 100–300 ℃, respectively, to determine the optimal blend for achieving desired compressive strength in the mortar samples. Initial findings indicate that treatment of RHA enhances the pozzolanic reactivity and overall strength of the biochar concrete, leading to improved compressive strength. Moreover, the addition of treated RHA shows encouraging outcomes in terms of improving mortar sustainability.