Effect of using metakaolin as supplementary cementitious material and recycled CRT funnel glass as fine aggregate on the durability of green self-compacting concrete

This present work is a study of the durability of green self-compacting concrete (SCC) that incorporates recycled cathode ray tube glass (CRTG) and metakaolin (MK). In these SCC mixtures natural sand has been replaced with CRTG at levels of 0, 10, 20, 30, 40 and 50% by weight, and the cement has been partially replaced by MK at substitution ratios of 5, 10, and 15% by weight. The fresh properties of SCC mixtures were then evaluated by slump flow, V-funnel, L-Box tests and their resistance to segregation was measured by the sieve stability test. The strength and durability properties of hardened SCC mixtures was assessed according to the compressive strength, ultrasonic pulse velocity (UPV), porosity, ions chloride permeability, gas permeability, and Alkali-silica reaction (ASR) tests. A SEM analysis was also carried out to examine the developing microstructure of hardened SCC mixtures. This study revealed an improvement in the fresh properties of SCC mixtures with up to 50% CRTG replacement. At the hardened state, the compressive strength and UPV of the SCC mixtures (10MK + 50CRTG) improved by 16% and 3% respectively after 90 days of ageing compared to SCC control mixtures. Moreover, using MK in SCC mixtures with different amounts of CRTG resulted in the best durability, while 10% of MK enhanced the porosity, permeability of chloride and gas permeability in SCC. Results show also that, 10% and 15% of MK can be prescribed in 0.1% limit of ASR in SCC mixtures with CRTG.