Role of recycled brick powder and alkaline solution on the properties of eco-friendly alkali-activated foam concrete

To cater for the need of the low-carbon era, this study proposed a solution by using recycled brick powder (RBP) and ground granulated blast furnace slag (GGBS) together with alkaline solution in the preparation of ecofriendly alkali-activated foam concrete. Effects of RBP replacement and alkaline solution on the work performance, hardened properties and microstructure of foam concrete were explored. Inclusion of RBP delayed the initial setting time, but high alkaline solution changed initial setting time and fluidity loss greatly. High RBP replacement combined with high alkaline solution were conducive to gain closed porosity, thereby impeding thermal conductivity. Though the presence of RBP was destructive to strength development, the increment of activator modulus or Na2O concentration could compensate its drawback. Microstructure results shown that the incorporation of RBP coarsened pore size and increased irregular shape pore, and this degradation was aggregated with high alkali solution. However, more GGBS and RBP activated by high alkaline solution participated in the geopolymerisation reaction to generate more hydration products, thus helped in forming closed pores and dense matrix. Overall, incorporating RBP in the blended system together with proper alkaline solution performed better in enhancing thermal insulation with comparable strength, thereby boosting RBP recycling rate and applying into dwelling structure.