Effect of the incorporation of NaOH-treated wood aggregates on thermal and mechanical properties of plaster mortar

Presently, the recycling potential of wood aggregates (WA) is limited. However, their utilization appears to be a viable alternative for building insulation. Recycled wood aggregates in composite materials are usually used in cement as a matrix. The present research focuses on the possibilities of their recycling in the plaster matrix. Wood aggregates/plaster (WAP) composites are prepared with varying WA densities (0; 5; 10; 15; 20 by volume). Four sodium hydroxide (NaOH) solution concentrations (1, 2, 6, and 10%) are used to treat WA at 80 °C for 2 h. Thermal and mechanical properties of newly treated bio-aggregates composites were investigated. Results show that the use of untreated WA makes the composite lightweight and enhances the thermal insulating performances of plaster paste but negatively affects its mechanical strengths. An optimal chemical surface modification of WA improves the flexural and compressive strengths and decreases the water uptake of resulting composites. The adequate treatment process (2% NaOH concentration at 80 °C during 2 h) of wood aggregates was proven when comparing treated and untreated fibers’ morphology as well as their crystallinity index. Experimental results confirm the possibility to reuse the wood aggregates in new mortars for insulating and building applications.