BOND BEHAVIOUR OF GFRP BARS EMBEDDED IN ALKALI ACTIVATED CEMENT CONCRETE

摘要

Steel reinforced ordinary Portland cement (OPC) concrete is a successful construction material due to its affordability, strength, and ease of construction. However, its success comes at a great risk to the environment because of the large carbon dioxide emissions associated with the cement production. Moreover, the steel bars, especially when the concrete is exposed to aggressive environments, are susceptible to corrosion. This high environmental footprint of reinforced concrete and its durability issues have inspired scientists and engineers to look for alternatives solutions. Glass fibre reinforced polymer (GFRP) bars, a corrosion resistant substitute to steel bars, and alkali activated cement (AAC) concrete, an environmentally friendly alternative to OPC concrete, stand out as ideal replacement materials. Different aspects of their individual properties have already been studied and their great potential has been reported. However, not much has been done on their bond properties. This research investigated the bond property between sand coated GFRP bars and fly ash based AAC concrete. The experimental program included pullout, beam-end, and beam splice tests. Bond stress-slip curves, factors affecting bond behaviour and tensile and bond stress distributions along the bar were studied.The results showed the comparable bond performance of AAC and OPC concretes with GFRP bars. A similar bond stress-slip behaviour was obtained for both AAC and OPC concretes in the sense that they display similar stages consisting of initial stiffening, nonlinear behaviour before peak stress, and softening when pullout failure takes place. The tensile and bond stress distributions along the embedment length were found to be nonlinear and the nonlinearity changes with the load. The experimental results were used to generate a constitutive bond stress-slip law. A good agreement was obtained between the numerical bond stress-slip curves and the experimental ones. Using the parameters of the bond stress-slip curve, finite element models were developed for the beam-end and beam splice specimens. The models were used to investigate the tensile and bond stress distributions along the bar and study the influence of parameters such as concrete cover, bar diameter, compressive strength, lead length and embedment length on the bond behaviour.