Mechanical properties and microstructure of UHPC with recycled glasses after exposure to elevated temperatures

Abstract

The purpose of this paper is to study the influence of particle size and colour of recycled glass (RG) as aggregate on the mechanical properties and microstructure of ultra-high-performance concrete with recycled glass (GUHPC) after high temperature. Various constituent materials were prepared in which quartz powder was completely replaced with recycled glass (RG) with three different particle sizes and colours in nine different mixture proportions. The explosive spalling and performance of the residual compressive strength and flexural strength of the GUHPC after the exposure to elevated temperatures were evaluated. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric and differential scanning calorimetry (TG–DSC) were conducted to reveal the fundamental reasons for the changes in the explosive spalling and high-temperature mechanical behaviour of the GUHPC. The results indicate that the particle size of the RG played a significant role in the high-temperature performance of GUHPC, whereas the colour did not. With increasing RG particle diameter, explosive spalling was more likely to occur even when steel fibres were added to the GUHPC. Further, a gradual reduction in the strength of the GUHPC after the exposure to different temperatures (except 800 °C) was observed. The GUHPC containing 0.08 mm RG particles exhibited the best performance after being exposed to various high temperatures; in particular, for 200 °C. The SEM analysis revealed that the microscopic interfaces between glass particles and cement matrix became less evident with decreasing glass particle size. To express the effect of RG on the GUHPC after an exposure to elevated temperatures mathematically, equations for the relation between the residual strength retention, RG particle size, and temperature are proposed.