Impacts of Conifer Leaves and Pine Ashes on Concrete Thermal Properties

Abstract

Global energy consumption has substantially increased. Although the thermal properties of conventional concrete have been comprehensively researched thus far, considerable research is left to address the impacts of agricultural waste ashes on the thermal characteristics of ternary binders. Conifer leaves and pines are inexhaustible resources, and the effects of their ashes on concrete properties, especially the thermal conductivity, are seldom investigated. In this study, 153 concrete samples containing 5, 10, 15, and 20% replacement levels of conifer leave and pine ashes were cast, and water absorption, compressive strength, and thermal conductivity of specimens were monitored. In addition, a thermal performance test of concrete exposed to a heating source was carried out to evaluate the impacts of conifer ashes on concrete thermal conductivity. The results revealed that regarding compressive strength, the optimum replacement levels for pine and leaves ashes are 15% and 10%, respectively. Compared to reference samples, replacing 20% pine and leaves ashes resulted in an 11.9% and 9.3% reduction in water absorption, respectively. The application of conifer ashes considerably reduced concrete thermal conductivity, which is essential for erecting low-energy buildings. Conifer ashes were found to considerably drop the thermal conductivity of the specimens (1.565 W/m/K) to a lower amount. Concrete specimens containing 20% pine and leaves ashes reduced thermal conductivity by 24.7% and 26%, respectively. Thus, the application of conifer ash enhanced the concrete thermal performance, leading to a lower energy consumption overall in concrete buildings.