Developing eco-friendly foam concrete with waste clay bricks and recycled polypropylene fibre

Incorporating recycled materials into concrete paves the way for sustainable construction while reducing landfill waste. The application of foam concrete in construction has demonstrated its potential to improve thermal insulation capacity and lower the dead load on structures, thereby enhancing sustainability. However, it has high embodied carbon and low thermal insulation when used for structural applications. Therefore, this study used waste clay bricks and recycled polypropylene fibres from face mask waste to develop an eco-friendly geopolymer foam concrete to improve the thermal and sustainability performance. Initially, the foam content of the geopolymer foam concrete mix was optimised based on the flowability, wet density and stability using different foam contents of 5 %, 10 % and 15 % by weight. Additionally, the effect of varying fibre dosages (0.5 %, 1 % and 1.5 % by volume) on the mechanical properties (compressive and flexural strength), mix homogeneity and thermal insulation characteristics were evaluated. The results showed that increased foam content resulted in a highly flowable mix, whereas reduced mix stability was attributed to a higher air content and the faster collapse of the air bubbles. However, adding fibres up to 1 % dosage improved the fresh properties and enhanced the stability of the mix. Furthermore, this also increases the flexural capacity by approximately 84 % when a 1.5 % fibre dosage is added. Based on the fresh properties and foam stability observations, a 10 % foam content was deemed optimal and adopted to develop fibre-reinforced geopolymer foam concrete. Furthermore, the compressive strength reduction for this foam content with the addition of fibre is insignificant (i.e. ≤ 10 %). Nevertheless, the fibre-reinforced geopolymer foam concrete exhibited low thermal conductivity (i.e. ranging from 0.245 to 0.331 W/mK) and diffusivity. This indicates that recycled fibres from face mask waste and waste clay bricks can be used to enhance the sustainability of foam concrete.