Drying shrinkage studies of wood sand concrete - Effect of different wood treatments

This work falls under the context of the valorization of local materials and the re-use of industrial wastes. Its main objective is to solve problems posed by the adding of wood shavings to the sand concrete, particularly its dimensional variations. Indeed, it consists to study the drying shrinkage of this material and to try reducing it by the treatment of the wood shavings before their use. Different treatments were tested: a cement surface coating, lime surface coating, cement-lime coating and oil impregnation. An experimental program was conducted in order to measure the shrinkage changes of several wood sand concrete samples by considering five different contents of wood shavings. The results demonstrated that the sand concrete is characterized by an important shrinkage compared to ordinary concrete. With the addition of wood shavings, the shrinkage is higher. Its evolution according to time was confronted with a concrete ACI-model. Then, a proposed model, inspired from ACI-model, has been established in order to adapt the model to wood sand concrete. Regarding the wood treatment, it has been shown the efficacy of all the used treatments on the improvement of the dimensional behavior. Considerable reductions have been recorded: the higher the quantity of wood is, the clearer the improvement is. In addition, the oil treatment was more effective than the surface coating by mineral binders. Concerning the coating, the lime treatment was more effective than the cement treatment. Moreover, the kinetic of the shrinkage evolution appears very fast at the first 2 weeks of drying, and then quickly tends to a slight stabilization. Finally, the effect of treatments on the shrinkage was compared to their effect on other properties such as lightness, mechanical strength and thermal insulation. (C) 2012 Elsevier Ltd. All rights reserved.