Mechanical Properties of Concrete with Different Carya Cathayensis Peel Biochar Additions

Producing biochar by consuming biomass is an effective way to reduce the environmental impact from biomass waste. This study investigates the influence of biochar made of carya cathayensis peel biomass waste, which is a specific biomass in Zhejiang province, China, on concrete basic mechanical properties. The biochar was added into concrete mixtures in three different patterns, including: (1) additional filler at the ratio of 1%, 2%, 3%, 4% and 5% by cement weight, (2) partial-cement replacement of 1%, 2%, 3%, 4% and 5% by cement weight, and (3) partial sand replacement of 5%, 10%, 15%, 20%, and 25% by sand volume. The strength, porosity and microstructures of the biochar concrete were experimentally investigated and compared with the plain concrete. The highest strength increase appears in concrete with a biochar addition of 5 % sand-replacement volume, and the compressive strength and splitting strength increase by 16.7% and 27.4%, respectively. The ITZ between the biochar particles and the cementitious matrix were tighter and glossier than the ones between the sand and cementitious matrix. The findings suggest that biochar made from carya cathayensis peel can be applied as a sustainable admixture into concrete to improve the basic mechanical properties when used as a partial sand substitute. The optimized addition method suggested is that of replacing 5% to 10% of sand by volume. This study offers an interdisciplinary attempt at valorizing biomass waste in producing green building and construction materials.