Quartz bentonite sandmix in sand-lime products

Abstract

Abstract The challenge related to waste management has become a serious worldwide environmental problem. Highly sustainable solutions, which do not involve reworking the material and are based on waste utilization, are sought. Such waste as used casting compounds, which so far has been used, among others, in construction, road construction, mining and cement production. Descriptions of the use of various waste moulding compounds, such as waste quartz compounds with water glass, quartz chamotte and quartz bentonite can be found in the literature. Due to the high content of quartz and low toxicity of bentonite sandmix, an attempt was done to use them for the production of sand-lime products. The aim of this article is to determine the suitability of the waste material as a substitute for quartz sand in the production of sand-lime products. The usability of waste was determined by laboratory tests of physicochemical characteristics of the finished silicates. Sand, which is a carrier of silica, was replaced with used moulding compounds with fractions up to 0.5 mm, in the weight amounts of 5.5, 11 and 16.5%. Applying up to 11% of used casting materials as a substitute for quartz sand with a lime content of 5.5% in the raw material mixture has a clearly positive effect on compressive strength. However, the higher share of sand substitution in the mixture weakens the mechanical features of the obtained materials. The absorptivity of the finished products increases with the increase of the inserted additions’ amounts. The influence of significant amounts of casting compound additives on the microstructure of calcium-silicate products was studied as well. It was stated, that they affect the location of the tobermorite in the volume of the autoclaved material.