Effect of Biomass Waste Materials as Unconventional Aggregates in Multifunctional Mortars for Indoor Application

In order to decrease energy consumption in buildings, a new way to recycle materials coming from biomasses waste in mortars was studied. For this purpose, mortars with water/cement equal to 0.5 by weight and aggregate/cement equal to 3.5 by volume were considered. Cement was replaced by hydraulic lime and sand was substituted with two different types of spruce sawdust shavings (as it is and roasted), biomass bottom ash and biomass fly ash. The results show that mortar prepared with cement has obviously a better mechanical strength and 60% lower capillary water absorption. All unconventional aggregates increase the total porosity of lime mortars. Moreover, biomass fly ash and both spruce sawdust shavings based mortars can be classified as lightweight mortar. Regardless of porosity and lightness, biomass bottom ash improves up to 150% the mechanical performance of lime-based mortars. Concerning durability, bio-based lime mortars show in general nearly twice higher capillary water absorption with respect to the sand lime mortars whit the exception of spruce sawdust shavings and biomass bottom ash. Mortars can be classified as permeable to water vapour. As it is and roasted spruce sawdust shavings are able to increase three and two times the capacity of the mortar to be a hygroscopic buffer in terms of MBV values.