Tobacco waste ash: a promising supplementary cementitious material

According to the European Cement Association, CEMBUREAU, in 2015, the global cement production was 4.6 billion tons. Traditional cement production emits approximately 1 ton of CO2 per ton of cement, which represents almost 80% of the total CO2 emissions of concrete and approximately 6% of the world’s emissions. Among supplementary cementitious materials, the use of agro-waste ash emerges due to its reduced CO2 emissions, chloride diffusion, and materials cost, in addition to its greater compressive strength. In Colombia, the disposal of agro-wastes, such as tobacco waste, is an environmental and economic concern. In this study, ash obtained from tobacco waste (TWA) was studied as a sustainable partial replacement for cement in hydraulic concrete. The TWA was reduced to a particle size of less than 75 μm and was characterized by X-ray florescence. A central composite design was used to study the influence of the ash replacement percentage of cement and the water/binder (w/b) ratio on the compressive strength at 28 days. The results show that it is possible to replace 10% of the cement with TWA using a 0.5 w/b ratio and obtain a 51% higher compressive strength than the control mixture at 28 days. Moreover, the experimental results demonstrated an improvement of 86% in the 7-day compressive strength when TWA was used.