Development of a Method for CO2 Solidification of Glass and Concrete Waste Composites

Abstract

Composite materials heve been prepared using a CO 2 solidification process from milling dust of autoclaved lightweight concrete (ALC; as matrix material), reinforced by addition of crushed glass (bottle) waste. The effect of varying glass collet size (0.08-5 mm) and glass volume (10-30%) on the fracture properties in the glass/ALC composite was examined by four point bending tests. For the glass/ALC composite cured under atmospheric conditions, we show, by conducting CO 2 solidification experiments at different CO 2 gas pressures (atmospheric, and 4-10 MPa), that the rate of reaction at the sample surface is faster under pressure, than under atmospheric conditions. At 4-10 MPa experimental conditions, a solidified 'reaction rim' is formed away from the sample surface characterized by the deposition of calcite, and a long internal fracture is created inside the sample, which reduces bending strength, although these characteristic features are not evident in samples cured at atmospheric conditions. Creation of the 'reaction rim' impedes further diffusion of CO 2 into the sample. Our results indicated that the CO 2 solidification of glass/ALC composite materials is best advanced under atmospheric conditions. The result also indicated that for <0.5 mm cullet size, the bending strength is enhanced, without being detrimental to fracture characteristics. However, increasing size of the crushed glass cullet (0.5 mm-5 mm) reduced the strength of the solidified composite. The interface between the ALC powder matrix and glass cutlet was weak, and a fraction glass cullets 0.08-0.5 mm size may be incorporated in the waste concrete matrix by as much as 30 vol%.