Green utilization of biomass by-product poplar leaf ash: A novel eco-friendly cementitious material for cement mortar replacement

[Display omitted] •The calcination method was used to treat poplar leaf biomass ash.•The chemical composition and particle size distribution were changed by the treatment.•650 °C is the best calcination temperature for poplar leaf biomass ash.•The replacement of cement by poplar leaf biomass ash has good economic and environmental benefits. The use of biomass for power generation is increasing. However, solving the solid biomass waste generated during the combustion process is a challenge. In order to reduce costs and the use of forestry waste, the replacement of cement in cement mortars with the same quality of poplar leaf ash was studied. The present study documents the potential of biomass ash obtained from calcined leaf ash as a supplementary cementitious. By thermogravimetric tests, 20 °C, 310 °C, 470 °C, and 650 °C were selected as the calcination temperatures. The effects of biomass ash on uniaxial compressive strength, crack extension, acoustic emission, and the microstructure of specimens at different curing ages of 7 d and 28 d were investigated. The results show that the strength of specimens mixed with 20 wt% poplar leaf ash is about 60% of cement mortar. The porosity of cement mortar specimens with biomass ash is higher than that of cement mortar. The hydration products of C-S-H and AFt are slightly less than cement mortar. To achieve the same flowability, the water-binder ratio is higher when mixed with biomass ash. As a result, the biomass ash specimens have higher porosity and lower strength. The strength of 310 °C and 470 °C is approximately 8.41% and 4.70% lower than that of 650 °C. The optimum calcination temperature for the pozzolanic activity of poplar leaf biomass ash is 650 ℃. This promotes the efficient use of biomass solid waste and the construction industry is green development.