Effect of recycled glass fines on mechanical and durability properties of concrete foam in comparison with traditional cementitious fines

Abstract

This paper shows the potential benefits of using recycled glass fines as a sustainable and low-cost alternative compared to fly ash, silica fume and fine sand in concrete foam. One of the main concerns of using recycled glass in concrete is durability and particularly alkali-silica reaction (ASR). SEM-EDS analysis of the mortar with glass showed the formation of ASR gel with a higher silicon to calcium ratio around the glass particles which justified the large ASR expansion. On the other hand, microtomography analysis showed that the porous structure of concrete foam can accommodate the expansion of ASR gel inside the pores with considerably less expansion and no cracking. The majority of the pores filled with ASR gel are at the outer edge of the sample which was in contact with the alkaline solution. The smaller pores are more likely to be filled with ASR gel compared to the larger pores. Replacement of 10 wt% of Portland cement with milled glass resulted in higher strength compared to the other cementitious materials because of better compaction within the binder and pore strengthening effect due to rearrangement of pore sizes, as well as reduction of the unit weight. Recycled glass slightly decreased water absorption but substantially reduced the drying shrinkage of concrete foam.