Feasibility study of using poplar wastes as sand in cement mortars

Abstract

An experimental investigation was undertaken to evaluate the potential use of poplar by-products in cement mortars. Two by-products from poplar processing were studied: sawdust (from sawing wood) and milled fibres (from wood waste obtained during cutting). Poplar fibres and sawdust were incorporated into mortars as sand volume substitution with rates ranging from 0 to 100%. Before introduction into the mortar, poplar aggregates were characterized (morphology and water absorption). It appeared that these wood aggregates absorb very quickly a large amount of water (up to 200%). The introduction of these poplar by-products has significant effects on the composite properties in both fresh and hardened states. It was noted that the workability of the mixtures with the poplar wood varies with the substitution rate. The inhibition of cement setting with poplar sawdust is characterized by maturity tests and affects the mechanical properties of mortars. In addition, increasing the poplar aggregates content causes a continuous increase of the material porosity, which leads to a decrease in density. Besides, it appears that the incorporation of poplar aggregates into mortars also decrease their thermal conductivities, which would help to reduce building heat losses. A significant decrease in the mechanical properties of poplar-based mortars was also noted, related to the rate of fibres or sawdust introduced into mixtures. The hydration disturbances, the high internal porosity of the wood particles and their low density can explain these lower mechanical strengths. However, despite these disturbances, the valorisation of poplar wood by-products remains possible in cementitious materials for the manufacture of concrete masonry blocks.