Improving construction sustainability by using glassy secondary materials as aggregate in concrete

This thesis reports experimental work, carried out as a PhD study, investigating the possible re-use of glassy secondary materials as aggregate in concrete. A study of the relevant literature suggested that slag from the Imperial Smelting Furnace method of zinc production (ISF slag) and Cathode Ray Tube (CRT) glass from end of life computer monitors and television screens would be promising materials to test. The main issues identified as being of most concern relating to the use of these materials were the potential for alkali-silica reaction (ASR) due to the glassy nature of the aggregate materials, in-service leaching of heavy metal ions, namely lead, zinc and barium from the aggregates and the possibility of a delay in set caused by the addition of these materials to concrete or mortar mixes. A comprehensive study has been completed that has included characterisation of the secondary aggregate materials, their incorporation into concrete mixes and their effect on ASR, leaching and retardation of concrete set. Methods have been identified to minimise these potential problems where they have been shown to be an issue. These include the recommendation of various additions, depending upon the specific problem being overcome, ranging from cement replacement materials, such as pulverised fuel ash (PFA) and ground, granulated blastfurnace slag (GGBS) to chemical additions such as barium and calcium chlorides. Overall, it has been shown that the ISF slag and CRT glass could prove to be useful secondary materials for use in the construction industry and it is hoped that their specification and use will be forthcoming as a result of this study.