Mechanical behavior of geopolymer concrete subjected to high strain rate compressive loadings

The effect of strain rate on the compressive behaviours of geopolymer concrete and mortar is reported. Split Hopkinson pressure bar was adopted for the high strain rate testings. The dynamic increase factors for compressive strength (DIFfc\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{DIF}}_{{f_{\text{c}} }}$$\end{document}) and critical strain (DIFεc\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{DIF}}_{{\varepsilon_{\text{c}} }}$$\end{document}) were measured and compared with Concrete Comite Euro-international du Beton (CEB) recommendations. The results show that alkaline activators have significant influence on the quasi-static compressive strength of geopolymer concrete. With high strain rate loading, the DIFfc\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{DIF}}_{{f_{\text{c}} }}$$\end{document} of geopolymer concrete and mortar mixes increase with respect to increasing strain rates and in agreement with CEB recommendations. In addition, the coarse aggregates in geopolymer concrete mixes play important role in the increase of compressive strength. However, CEB recommendations underestimate the DIFεc\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{DIF}}_{{\varepsilon_{\text{c}} }}$$\end{document} of critical strain for geopolymer concrete in the high strain rate loading. It is found that for the quasi-static loading and low strain rate loading, cracks propagate along interface transition zone (ITZ) and matrix of geopolymer concrete specimens whereas cracks occur at both the aggregates and ITZ under high strain rate loading.