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

Journal article (2021)

Authors

Shizhe Zhang Materials and Environment - CEG
Z. Li Materials and Environment - CEG
B. Ghiassi University of Nottingham, Materials and Environment - CEG
Suhong Yin South China University of Technology
G. (Guang) Ye South China University of Technology, Materials and Environment - CEG
Research Group
Materials and Environment (CEG) (TU Delft)
Copyright: © 2021 Shizhe Zhang, Z. Li, B. Ghiassi, Suhong Yin, G. Ye
DOI: https://doi.org/10.1016/j.cemconres.2021.106447
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Published Date

2021

Language

English

Faculty

Civil Engineering & Geosciences

Department

Materials- Mechanics- Management & Design

Research Group

Materials and Environment

Abstract

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 KIc (Jtip), 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 KIc (Jtip) 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.