Cement pastes modified with recycled glass and supplementary cementitious materials: Properties at the ambient and high temperatures

Recycling of glass has attracted great attention in the construction industry since it can be partly utilized as aggregate or pozzolan in cement and concrete. However, high-temperature performance of cement concrete containing waste glass is one of the major concerns for use in building applications. This paper studies the mechanical and high-temperature properties of cement pastes modified with glass particles (GPs) compared with those made by other supplementary cementitious materials (SCMs). The replacement ratio of GPs or SCMs was kept at 30% by weight throughout the experiment. SCMs used in the study were ground granulated blast-furnace slag (GGBS), pulverized fly ash (PFA) and metakaolin (MK). To examine the size effect of GPs, three levels of size grading were adopted. Experimental results indicate that the use of GPs or SCMs slightly reduces the densities of the pastes, but increases their water absorption capability. Thirty percent of MK and GGBS in the pastes has a negligible impact on compressive strength. As for GPs, a decrease in compressive strength was noticed regardless of glass size used. It should be noted that the influence of GPs on strength is mainly governed by packing instead of pozzolanic effect. Similar to other SCMs, GPs can improve the residual compressive strength of pastes after exposure to a temperature of 300 °C, but significantly decrease when the temperature increases to 600 °C or 900 °C due to the decomposition of hydration products and the annealing effect of GPs.