Multiscale Ab-Initio Modeling and Experiment of Nano-CaCO3 and Fiber Synergy on Toughening Low-Carbon Geopolymer Composites

Abstract

Although the geopolymer is generally regarded as a solution to low-carbon building materials, the intrinsic high brittleness greatly limits its further engineering practices. Here, we performed multi-scale ab-initio modeling and experiment on synergistic effect on toughening mechanisms of nano- calcium carbonate (NCC) and polyethylene fiber (PEF) on geopolymer mortar. Results showed that NC significantly improved the binding between geopolymer gels (C-S-H and N/C-A-S-H) and PEFs through the calcium (Ca)-triggered electrostatic attractions. The hydrogen bonds were rarely formed between PEFs and geopolymer gels, benefiting the toughening effect through PEF pull-out. This insightful mechanism was well presented in the combined use of 12 mm + 6 mm PEF + 1% NCC, where the highest synergistic effect on bending toughness, crack number, PEF dispersion was realized. The relationship of toughness-crack amount and toughness-crack fractal dimension tracked good natural log and exponential function, respectively. The above mechanism were further confirmed by the microstructural analyses.

Keywords: nano-calcium carbonate, polyethylene fiber, synergistic toughening effect, geopolymer, ab-initio modeling