Lightweight Aggregate Processed from Waste Materials

Abstract

In order to decrease the deadweight of structures and/or increase thermal and acoustic insulation properties, the most widely used material for the preparation of concrete is lightweight aggregate processed either from naturally occurring lightweight materials or waste materials. The present paper presents a methodology for the production of light-waste aggregate (LWA). Waste glass, silica sludge, clay, and polishing residue were studied as potential raw materials. There are two different mechanisms active in the process of LWA production; one is combustion of organic residue in clay matrix, resulting in porous structure, the other one is a foaming process, applicable to glassy matrix where a selected foaming agent degasses at elevated temperature, and the resulting gasses remain trapped in the glassy structure. In the presented case, paper mud served as poreforming agent whereas MnO2 and SiC were added as foaming agents. The emphasis of this study was placed on finding suitable additives for lowering the softening temperature and thus facilitating the foaming process. It was found that the addition of polishing residue from the polishing process of granite–like stone lowered the softening point of the clay and silica sludge. Depending on mixture composition and regime of firing, lightweight aggregates with densities between 0.5 and 2.0 g/cm3 were obtained and analyzed.