Mechanical, thermal and durability investigation of compressed earth bricks stabilized with wood biomass ash

Abstract

There is a growing interest in raw earth as an eco-material of building for its local character and the low energy consumption that characterizes its overall life cycle. This work evaluates the effect of the recovery of two biomass ashes (WBAa, WBAb), resulting from domestic wood heating on the mechanical, thermal and durability properties of compressed earth bricks (BWBAa, BWBAb). These specimens were obtained in a partial substitution of a silty-clay soil by WBA, in various proportions (0, 5, 10, 15 and 20 wt%). The specimens manufactured were compacted with a compaction stress of 10 MPa, exposed to the open air and kept in the laboratory at a 20 ± 2 °C temperature, then allowed to harden for 7 and 28 days. The mechanical level strength increases with wood ash content and with curing time. BWBAb has the best flexural and compressive levels strength caused by formation of compounds with binding properties, but BWBAa shows good thermal insulation. Capillary water absorption test was performed to prevent the durability of the elaborated specimens under water action. These bricks showed different behaviors in contact with water based on the different microstructure present in the two ashes. The experimental study conducted highlighted the benefits of the high periclase (MgO) content on the mechanical properties and durability of compressed earthen bricks.