Performance of granulated foam glass concrete

This research investigated the feasibility of using granulated foam glass (GFG), as natural aggregate substitute by volume, in concrete production. The GFG aggregates used in this study were produced from mixed colour glass bottles waste. The effect of various proportions of coarse GFG (30%, 40%, 50%, 60% and 100%) and fine GFG (5%, 10% and 15%) on fresh, mechanical properties, carbonation and alkali-silica reaction (ASR) have been established and its suitability for use in a range of practical applications is assessed. A series of concrete mixes were proportioned with water-to-cement ratios (w/c) of 0.40, 0.55, 0.62 and 0.76. The GFG aggregates are characterised as of a high content of silicon oxide, porous texture, around 40% low relative density and 2-4 times higher water absorption compared to natural aggregate (NA). Overall, GFG characterisation test results have demonstrated their potential for use as lightweight aggregates in concrete production. Results of compressive strength testing showed that up to 30% coarse or 5% fine GFG had generally negligible effect on the cube and cylinder strength of concrete. Moreover, within 3-days 30% coarse GFG concrete specimens achieved on average 70% of their 28-day compressive strength. This increased to a range of 73-87% at 7-days, regardless of GFG content and comparable to corresponding NA concrete mixes. Up to 50% of NA replaced by the GFG has shown insignificant effect on the carbonation rate as compared to the control NA concretes. Results of accelerated ASR testing indicate expansions of both control NA and up to 50% GFG mixes, but values were found to be within the acceptable limit set by ASTM C1260. A microstructural investigation of the cement paste containing fine GFG using Scanning Electronic Microscope (SEM) images has shown a minor ASR gel and reaction products were dissipated through the pore system of the GFG. The formation of gel in the pores has contributed to minimize the expansions exhibited and thus, evacuate/relax the internal stresses. On the whole, potential extent to which coarse/fine GFG content can be used, as natural aggregate substitute (by volume), has been identified.