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 waste materials coming from biomasses by-product in mortars was studied. In this way a better management of biomass waste, reducing materials in landfill, can also be reached. To this aim, mortars with water/cement equal to 0.5 by weight and aggregate/cement equal to 3.5 by volume were considered. Then, 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 better mechanical compressive strength and 60% lower capillary water absorption. All unconventional aggregates increase the total porosity of lime mortars from 41%, in the case of biomass bottom ash, to 52% in the case of spruce sawdust shavings and fly ash. Moreover, biomass fly ash and both spruce sawdust shavings, decrease density of mortars to permit the classification as lightweight mortar (with ρ less than 1300 kg/m3). Regardless porosity and lightness, biomass bottom ash improves up to 150% the mechanical performance of lime-based mortars. As regards durability, in general bio-based lime mortars show nearly twice higher capillary water absorption with respect to sand lime mortars. Roasted spruce sawdust shavings and biomass bottom ash decreases the capillary water absorption of lime mortars of about 5% and 50%, respectively regardless of porosity and lightness. All mortars can be classified as permeable to water vapour, since the vapour transmission resistance factors are very close or less than 15. Moreover, spruce sawdust shavings as it is and roasted are able to increase three and two times the capacity of mortar to be a hygroscopic buffer in terms of MBV values. All biomass waste unconventional aggregates improve the depollution capacity in terms of percentage of adsorbed Volatile Organic Compound as Methyl Ethyl Keton (MEK) inside a sealed box of lime-based mortars. In particular, both biomass ashes (bottom and fly) show the best performances with a reduction of MEK concentration 75% higher than reference lime mortars adsorbing up to 95% of MEK after two hours test.