Material Characterization of Geopolymer Mortar for its beneficial Use in Composite Construction

This paper investigates material properties of metakaolin/slag-based geopolymer mortar (GPM), relevant for composite action with conventional Portland cement-based concrete (PCC). GPM formulations with different workability (soft and stiff-plastic consistencies) were developed and characterized with regard to their compressive and tensile strength development over time, their shrinkage behaviour during hardening under different ambient conditions, as well as their thermal expansion. With the experimental data obtained, a coefficient of thermal expansion and equations for predicting the strength development were calculated. The GPMs exhibited significant autogenous shrinkage and drying shrinkage. Additionally, high very early shrinkage, tested by a new image correlation method, occurred immediately after setting under dry conditions. Thereby, the observed extent of early shrinkage strongly depended on the specimens’ thicknesses. Furthermore, the basic characteristics of autogenous and drying shrinkage of GPM were enlightened and compared to PCC.