Rheological and physico-mechanical investigations on the destabilization of unfired clay bricks with almond husk additive by salt

Abstract

In the aim of enhancing unfired clay bricks’ strength, waste materials incorporation gains huge interest among researchers. In this context, various methodologies are extensively used. However, the salt concentration’s effect is poorly known. In this paper, we study, through rheological and physicomechanical investigations the influence of different salt concentrations on unfired clay bricks incorporating 0%, 2%, 5%, 10%, and 20% almond husk powder by weight. We report comprehensive measurements, under dynamic conditions, of the viscoelastic behavior of aqueous solutions at high colloidal clay minerals concentrations, allowing us to derive the storage modulus which expresses the elasticity potential of the material. The same materials are used to manufacture corresponding bricks. Their strengths and water absorptions are determined and reported. In all studied suspensions, the oscillatory test showed a plateau-like with solid-like characteristic. It was indicated that the storage modulus highly depends on the amount of the additive in the clay. It increases with the incorporation of almond husk powder, and it decreases with higher salt concentration. This is explained by interparticle phenomena involving cation exchange, and hydrophilic and hydrophobic effects. Compared to old works that used the raw soil without any kind of treatment, the utilization of washed clay enabled the production of stronger bricks by up to 10,85 %. The gain, when using washed clay and incorporating 2 wt% almond husk, reached 18.88% compared to the brick with pure raw clay. The corresponding brick recorded 23.17 MPa in strength which conformed to ASTM C62 – severe weathering grade. A decrease in strength with the incorporation of almond husk is reported due to the constitution of flocculating particles that generated a porous network. To improve unfired clay bricks’ strength quality, this research comes with the recommendation of washing the soil used in unfired bricks down to reach a specific value of conductivity which can be determined facilely by rheological measurements (13 µS/cm in the case of this article)..