Enhancing carbon sequestration in cement mortar using high volume local rice husk biochar coupled with carbonation curing

In recent times, considerable attention has been devoted to investigating the viability of utilizing sustainable alternatives derived from agricultural waste to partially replace cement in the construction industry. The vast rice plantations in Malaysia produce a substantial amount of rice husk waste, which can be converted into biochar and incorporating it into cement concrete products. Biochar is known for its carbon sequestration potential. Thus, the study presents the investigations on high dosages of locally produced rice husk biochar (RHB) as cement replacement, specifically at 10, 20, 30 and 40 % by volume. The experiment focuses on reusage of rice husk waste and enhancing the carbon sequestration ability of cement concrete. The addition of RHB improves and facilitates carbonation process, as evidenced by the increased in the carbonation depth and degree of carbonation. There is an improved CO2 uptake with RHB-added mortar up to 46.2 % compared to the control mortar. Saturated RHB-added mortar demonstrates the highest CO2 uptake of 17.1 %, higher than unsaturated RHB-added mortar. Besides, the carbonated mortars exhibit higher strength than water-cured specimens, resolving the strength issue with higher RHB addition. Overall, the optimum RHB replacement at 20 % contributes to higher carbon uptake and an improved strength in cement mortar through carbonation curing.