121 / 2022-04-27 07:26:26

Use of luminescent-glass aggregates and CO2 curing treatment for the production of decorative concrete products

Recycled glass; CO2 curing treatment; Alkali-silica reaction; Glow light; Decorative concrete

This project was first aimed to utilize the transparent characteristic of recycled glass (RG) and glow light ability of luminescent powder (LP) to trap light on the daytime and emit back during the nigh time. As shown in Fig. 1, transparent adhesive was successfully used to adhere the LP on the RG for the preparation of luminescent-glass (LG). The different particle sizes (2.36~5mm and 5~10mm) of LG was then used as 100% aggregates in the production of white cement based architectural luminescent-glass mortar, and the glow light performance and mechanical properties of the mortar were assessed accordingly. The results show that the produced luminescent-glass mortar can attain ~30 MPa compressive strength and ~7 MPa flexural strength, meeting most of the building construction and paving application. Moreover, the luminescent-glass mortar can maintain its yellowish-green light (glow) for about 8 h, and the larger particle size of LG is found to perform better glow light than that of smaller size of LG. This is mainly due to the fact that larger LG had more even deposition of LP across the glass surface and able to accumulate more lights in one place.



However, the major concern of incorporating RG in concrete is known to be the risk of alkali-silica reaction (ASR). This is because the amorphous SiO₂ of glass aggregate is very reactive and prone for the precipitation of ASR gels formation in the alkaline environment of concrete. Moreover, due to the crushing process of glass from discarded soda-lime bottles, the ASR is more easily initiated at the residual internal cracks (>2.5 μm) in the glass. For this reason, this project was further investigated the influence of CO₂ curing treatment on the ASR mitigation for mortar containing 100% of RG. Compared with standard curing (0.04% CO₂, 95% relative humidity, RH), a short period (3 h) of CO₂ curing (20% CO₂ and 65% RH) could fully suppress the 14-day ASR expansion according to ASTM C1260 results (see Fig. 2). With the reduction of calcium hydroxide in the cement matrix upon CO₂ curing treatment, silica could dissolve from the RG surface and induced ASR at the RG-cement interface with less expansive expansion compared to that of gels formed at the internal cracks of RG. Furthermore, the pressure from the surface ASR gel and strength enhancement due to CaCO₃ precipitation lead to higher cracking resistance in RG and matrix.