Behaviour of cement mortars containing an industrial waste from aluminium refining: Stability in Ca(OH)2 solutions

Abstract

[EN] The physical and chemical interaction between a solid industrial waste from aluminium refining and saturated Ca(OH)2 solution, as well as the effects of substituting siliceous sand for the waste on the physical and mechanical properties of mortars were studied. The waste is a solid that contains reactive alumina capable of combining with the calcium hydroxide. These reactions result in stable and insoluble compounds. This alumina, together with the halite (also present in the waste composition), chemically react with a saturated solution of Ca(OH)2, giving as a main reaction product the so-called Friedel's salt (Ca4Al2Cl2O6 · 10H2O). Strätlingite and Si-hydrogarnets were among other products detected. The waste has a high specific surface area. The cement/waste mixtures therefore require a higher quantity of mixing water than cement/sand mixtures. The result is a decrease of the mechanical strengths and an increase of the total porosity. However, a decrease of the average size of the pores occurs, which can have a positive effect on the durability of the final material.