Dynamic tensile properties of geopolymer concrete and fibre reinforced geopolymer concrete

Abstract

Geopolymer concrete (GPC) has attracted much attention over the past decades because it utilizes industry wastes and has outstanding mechanical properties. To improve its ductility and energy absorption capabilities, various types of fibres have been incorporated into GPC. This paper carries out an experimental study to quantify the dynamic tensile properties of GPC and fibre reinforced GPC (FR-GRC) with hooked-end steel fibre and polypropylene (PP) fibre. Both quasi-static and dynamic split-tensile tests are performed on plain GPC and FR-GPC covering strain rates of 10-5s−1 to 16 s−1. The addition of 0.5% volume content of steel and PP fibres is found to effectively improve the ductility of GPC at both static and dynamic states. Under quasi-static loading, the crack opening displacements reach about 0.15 mm for GPC, 9 mm for SGPC and 8 mm for PPGPC upon failure, and when subjected to impact loading, the crack-opening rate of GPC is higher than that of FR-GPC. Fibre stretching process after concrete crack till pull-out/fracture is observed which considerably contributes to the reduction of crack expansion and the enhancement of energy dissipation capacity of GPC, with enhancements reaching up to 33% for PPGPC and 94% for SGPC. The split-tensile properties of both plain GPC and FR-GPC are found to be sensitive to strain rate, while geopolymer with PP fibre shows a similar behaviour as plain geopolymer, and GPC with steel fibres appears to be less sensitive to strain rate effect. Empirical relations are proposed to correlate the dynamic increase factor (DIF) of tensile strength for GPC and FR-GPC with strain rate. Comparison between plain GPC and FR-GPC shows that fibres can absorb additional energy to improve the impact resistance and deformation capacities.