Cement Replacement and Improved Hydration In Ultra-High Performance Concrete Using Biochar

摘要

This study demonstrates the efficacy of biochar in a dual role of internal curing agent as well as a viable candidate for cement replacement in ultra-high performance concrete (UHPC).Bio-char (BC),a product of pyrolysis of mixed wood saw dust,was prepared by pyrolytic conversion at 500 °C.Biochar produced was manually grinded into micron-sized particles.It was then pre-soaked for 24 h to achieve saturation,which was then mixed to replace 2%,5% and 8% of cement by wt.in UHPC.Isothermal calorimetry (ITC) tests showed that the presence of BC improved the hydration in BC-UHPC mix compared to reference.This is further confirmed from the bound-water measurements using thermo-gravimetric analysis (TGA),where a substantial improvement in BC-UHPC mix compared to reference was observed.Scanning electron microscope (SEM) images revealed that pores of BC serve as nucle-ation sites for hydration products.The drop in compressive strength in BC-UHPC mix were limited to 10% of the reference mix,and comparable strength was achieved at 5% replacement level.Overall,the results indicate that bio-char from wood waste can be a potential mineral admixture in UHPC,which might be effective to reduce cement demand and create novel avenue for waste valorisation.