Influence of forest biomass bottom ashes on the fresh, water and mechanical behaviour of cement-based mortars

Abstract Renewable energies’ production is increasing globally over the years. Biomass is considered a renewable source of energy that can be produced by organic matter. The biomass energy production, although generating low CO2 emissions, creates wastes during the production process, namely ashes. The increase of renewable energies’ production and the consequent biomass energy production is also responsible for a higher production of these ashes. Most of these ashes are sent to landfills. This should be avoided since it is responsible for several soil, air and human environmental impacts. The fine ashes particles can lead to respiratory human health problems, as well as contaminate the soils, ground water and the air. Therefore, it is necessary to find new applications for these ashes in order to reduce their deposition in landfills. In this research, an eco-solution is presented to reduce the cement content of the mortars and, at the same time, the biomass deposited in landfill by their incorporation in renders, replacing cement at 5%, 10% and 15%, by volume. The use of biomass ashes in cement-based mortars was investigated through their fresh, water and mechanical behaviour. It was possible to conclude that cement can be replaced up to 15% by a forest biomass ash waste in render applications, without compromising the global behaviour. The incorporation of the waste led to similar fresh and water behaviour to that of a reference mortar, better deformability and slightly lower mechanical strengths, which did not affect the scope of the mortars application, according to EN 998-1.