Assessment of the mineral phase and properties of clay-Ca bentonite lightweight aggregates

Abstract

This study deals with improving the properties of lightweight aggregate by the addition of Ca-bentonite mineral to expandable clays. The addition of bentonite can result in advanced lightweight aggregate materials which meet international standards. Besides bentonite material, twelve different clays (from Egyptian and Hungarian mines) were studied by X-ray fluorescence (XRF), X-ray powder diffraction (XRD, Rietveld method), and a heating microscope (HM). Aggregates were produced and their physical and mechanical properties were measured. The structure and the chemical composition of the clay-Ca bentonite aggregates were studied by scanning electron microscope (SEM) and with energy dispersive spectroscopy (EDAX). The results showed that the addition of 10 wt% bentonite can reduce the bulk density by up to 20%, can increase the compressive strength by up to 180%, and can increase the height of expansion by up to 68% in some samples. It was found that the high kaolinite content of the clay samples was not beneficial for expanding and decreasing the bulk density of aggregates. According to the Rietveld method from XRD and a statistical correlation model shown, the amorphous contents have a reciprocal relationship with the bulk density and a direct relationship with the height expansion. Bentonite, as a natural additive, to some clays, was suitable for producing lightweight aggregates with far better properties, as well as a more economical means of production.