Fracture properties and microstructure formation of hardened alkali-activated slag/fly ash pastes

Fracture properties and microstructure formation of hardened alkali-activated slag/fly ash pastes

Zhang, Shizhe (TU Delft Materials and Environment)
Li, Z. (TU Delft Materials and Environment)
Ghiassi, B. (TU Delft Materials and Environment; University of Nottingham)
Yin, Suhong (South China University of Technology)
Ye, G. (TU Delft Materials and Environment; South China University of Technology)

2021

This study presents a comprehensive experimental investigation on the fracture properties of hardened alkali-activated slag/fly ash (AASF) pastes in relation to the microstructure formation and reaction product composition. The main reaction product in AASF is C-(N-)A-S-H gel along with minor hydrotalcite phase, with the polymerization of C-(N-)A-S-H gel substantially governed by its Ca/Si ratio. Strong positive correlations are identified between the Ca/Si ratios of C-(N-)A-S-H gel and the fracture properties K_Ic (J_tip), whereas, the compressive strength of AASF pastes is primarily determined by its capillary porosity (>0.01 μm). The disagreements between the Ca/Si ratios and corresponding intrinsic mechanical properties of C-(N-)A-S-H gel as proof by contradiction indicate that the fracture properties K_Ic (J_tip) of AASF pastes could be dominated by a cohesion/adhesion-based mechanism. These findings provide promising guidance for fine-tuning the fracture properties of AASF and also advise on the tailoring strategies for high-performance composite such as strain-hardening geopolymer composite.

Alkali-activation
Ca/Si
Fly ash
Fracture toughness
Microstructure
Slag

http://resolver.tudelft.nl/uuid:39de093f-6b95-40d0-9835-67bf49fcf72a

https://doi.org/10.1016/j.cemconres.2021.106447

0008-8846

Cement and Concrete Research, 144

Institutional Repository

journal article

© 2021 Shizhe Zhang, Z. Li, B. Ghiassi, Suhong Yin, G. Ye