Effects of crushed glass cullet sizes, casting methods and pozzolanic materials on ASR of concrete blocks

The aim of this study is to investigate the influence of using different particle sizes of recycled glass, casting methods and pozzolanic materials in reducing the expansion due to alkali-silica reaction (ASR) of concrete blocks prepared with the use of crushed glass as fine aggregate. In this work, 25 × 25 × 285 mm mortar bar specimens were prepared using conventional wet-mixed and dry-mixed methods. Except for the control mortar bar, all the specimens were prepared by completely replacing river sand with different particle sizes of recycled glass. In addition, the influence of fly ash (PFA) and metakaolin (MK) content on the reduction of ASR expansion was also investigated. The flexural strength of the mortar bar specimens before and after they had been exposed to 1N NaOH solution was determined to complement the results of ASR expansion test. SEM was performed to examine the microstructure as well as nature of the cement binder-glass interfacial zone. The results reveal that ASR expansion reduced with reducing particle size of glass used. For the same given mix proportion, the dry-mixed method resulted in 44% less expansion when compared with the wet-mixed method. Both PFA and MK were demonstrated to be able to significantly reduce ASR expansion of the concrete glass blocks.

Research highlights► Provide a more effective solution of reducing the risk of expansion due to alkali-silica reaction (ASR) in cement mortar made with recycled glass. ► This work has demonstrated that by using smaller glass (<600 μm), dry-mixed casting method and pozzolans (PFA or MK) to be able to significantly reduce ASR expansion of the concrete glass blocks. ► A thorough understanding on the ASR performance of mortar bars made with different particle sizes of recycled glass culltes, different casting methods and different dosage of pozzolans used is provided.