Use of biomass bottom ash as granular substitute in mortar

Abstract

An experimental investigation was undertaken on the effect of biomass bottom ash (BBA) as a sand substitution in a mortar design. The objective is to characterise the physico-chemical properties of BBA and to establish a reusable proportion in cementitious composites. The aim is to provide a new way to treat these industrial waste and to reduce the consumption of non-renewable natural aggregates. First, biomass bottom ash from fluidized bed boiler are characterised by physico-chemical and mineralogical analysis. Then, they are compared to the properties of boiler sand use in the combustion process. Finally, boiler sand was substituted by BBA into mortar with a rate of 0–100% of the sand volume. The results show that incorporation of BBA does not significantly influence the hydration kinetics of the cementitious matrix. However, an enhancement of the amount of heat hydration was observed. Furthermore, the BBA substitution leads to decrease the mortar workability. In the hardened state, BBA incorporation shows an increase of mechanical properties. This finding was confirmed by a decrease of the mortar porosity. The results of this study show that there is no contraindication to the use of BBA as an aggregate for the formulation of cementitious materials.