Assessment of strength development in Bayer-process residues

Abstract

The strength which develops naturally in dried-out lumps of Bayer-process residue (red mud) is investigated for possible use in building material. The ease with which this strength can be reproduced, and its resistance to wet and dry conditions, are assessed in practical-sized building blocks. The evidence suggests that with careful preparation the binding can be exploited to make blocks suitable for the construction of single-floor buildings. The origin of this strength is also investigated by using electron micrography, X-ray diffraction and thermogravimetric analysis (TGA) of selected red mud aggregates. The strength is attributed to the presence of significant quantities of aluminous goethite in the mud. This poorly crystalline material (amorphous to X-rays) is believed to act as a binder by coating the very fine particles present in mud, imparting strength when it dries by providing a rigid bridge between particles.