Characterizing the bond strength of geopolymers at ambient and elevated temperatures

This paper presents characterization of bond strength of geopolymers at ambient and elevated temperatures. The bond strength of 18 different formulations of metakaolin (MK)/fly ash (FA) based geopolymers is evaluated through double shear tests in 20-300 °C temperature range. The test parameters include fly ash content, SiO₂/K₂O ratio, solid-to-liquid ratio and Si/Al ratio. In addition the effect of additives, namely short carbon fibers, basalt fibers and styrene-acrylate emulsion in MK/FA precursor, on bond strength is studied. Data from the tests show that geopolymers exhibit slightly lower bond strength than that of epoxy resin at room temperature, however geopolymers retain much higher bond strength in 100-300 °C range. Addition of small quantity of short carbon fibers in MK/FA precursor does not significantly influence bond strength of geopolymers at ambient temperature, but greatly improve bond strength retention in 100-300 °C through crack control mechanism.