Experimental study on the interface properties of PVA fibers in slag/fly ash based geopolymer pastes

Bonding strength between fiber and matrix is a crucial factor which can largely determine the performance of fiber reinforced geopolymer composite. However, the available information on the fiber/matrix interface properties in s lag/fly ash based geopolymer is still quite limited, which have hindered the scientific design of related fiber reinforced composites. This study presents the bonding characteristics of PVA fiber/slag-fly ash based geopolymer matrix interface determined by single fiber pullout tests. Four SiO2/Na2O ratios (0.8, 1.0, 1.2 and 1.5) within the alkaline activator were used for mixture preparation. All specimens were tested after 28-day curing. The interface characteristics including chemical bonding energy, interfacial frictional force as well as the slip-hardening properties were determined from the fiber pullout tests. It was found that the chemical bonding energy first increased and then decreased with increment of SiO2/Na2O ratio, indicating an optimal alkaline activation condition at SiO2/Na2O ratio of 1.0-1.2. On the other hand, the interfacial frictional force and slip-hardening properties seems to be not influenced by increasing the SiO2/Na2O ratio. This research provides a fundamental understanding into the interfacial bonding properties of PVA fiber to the slag-fly ash based geopolymer matrices.