Valorization of biomass ash fines as a cementitious addition: Effects on the microstructural, mechanical, and thermal properties of mortars

This study explores the potential of fine biomass ash as a partial cement additive in mortars, with the objective of developing sustainable building materials that exhibit a low carbon footprint. The impact of Portland cement (CEM II 52.5N) substitution rates ranging from 5 to 30% on the microstructural, mechanical, and thermal properties of mortars was assessed through a series of studies. The results demonstrate a gradual increase in porosity (from 16.9% to 38.6%) and water absorption (from 4.4% to 20.2%) with the substitution rate, indicating a more open and less dense structure. Consequently, mechanical compressive and flexural strengths undergo a decline, particularly at levels of substitution exceeding 15%. However, significant enhancements have been witnessed regarding thermal and environmental performance. Thermal conductivity was found to decrease from 2.11 to 1.12 W/m·K. Furthermore, analysis of the carbon incorporated indicated a reduction of nearly 28% in CO 2 emissions at 30% substitution. This study provides substantial evidence that validates the hypothesis concerning the potential of biomass ash as an eco-efficient cement additive. It has been demonstrated that this additive can reduce the environmental impact of cementitious materials. Subsequent research will concentrate on the comparison of bottom ash and fly ash from biomass, in addition to the enhancement of the pozzolanic reactivity of ash through mechanical or chemical activation. This approach provides a foundation for the development of sustainable cementitious materials that incorporate recovered by-products from the wood energy sector.