Hybrid effect of polyethylene fibre and nano-calcium carbonate on the flowability and strength of a geopolymer composite

Using geopolymer composites to reduce the use of Portland cement can decrease carbon dioxide emissions. The focus of this study was on improving the strength of a geopolymer composite by assessing the positive hybrid effect of nano-calcium carbonate (NCC) and polyethylene fibres (PFs) of different lengths (6 mm and 12 mm). Fresh and hardened properties, including flowability and strength, were investigated to evaluate the hybrid effect. Generally, the hybrid effects from the PFs of different lengths and NCC were negative for flowability, but the hybrid effects were positive on strength. The combination of 12 mm PF + 6 mm PF + 1% NCC was found to have the highest hybrid effect on bending strength, resulting from the good fibre–matrix bond. The bending strength of the PF-reinforced geopolymer composite was assessed based on a new regression coefficient (A), which takes into account the hybrid effect, the fibre–matrix bond strength and fibre dispersion. The new model for the bending strength of PF-reinforced geopolymer composites introduced in this paper is simpler and more effective than previous models provided in the literature.