The influence of the fireclay waste on the microstructure and the physico-mechanical properties of autoclaved aerated concrete

Abstract

Autoclaved aerated concrete is a building material with good thermal insulation properties, which it receives through the pore structure. The production of autoclaved aerated concrete consists of two phases. In the first stage, a porous structure is formed by the reaction of calcium hydroxide and aluminum powder to form hydrogen. In the second stage, the lime and siliceous components react under hydrothermal conditions to form crystalline calcium hydrosilicates which form a binder component in the material. In this paper, the degree of crystallization of calcium hydrosilicates is studied depending on the quantity and fineness of the admixture of the fireclay waste. The effect of three different sizes of the specific surface of the fireclay waste on the microstructure and physico-mechanical properties of the autoclaved aerated concrete was monitored. At the same time, the influence of sand substitute for waste was monitored. The amount of the substitute was 10%, 30% and 50%. Finally, the influence of the fireclay waste admixture on the autoclaved aerated concrete porous structure was assessed. The microstructure was analyzed by X-ray diffraction. Based on the achieved values, it can be said that the admixutre of fireclay waste has a positive effect on the crystallisation of calcium hydosilicate phases. Fireclay waste substitution is possible up to 50%. With a higher amount of substitution, the increasing pressure of autoclaved aerated concrete compression is monitored.