Long-term durability prediction models for GFRP bars in concrete environment

Abstract

This article presents a durability study of glass fiber reinforced polymer (GFRP) bars within concrete environment and provides recommendations for effective accelerated ageing methods, data reduction and validation, and formulation of master curves for long-term predictions. Concrete beams reinforced with GFRP bars were immersed in tap water inside temperature-controlled tanks. Sustained load was applied to beam samples, and elevated temperatures were used to accelerate the ageing of GFRP bars. After exposure, GFRP bars were tested for residual tensile strength, which was considered as a measure of the durability performance of the specimens. Scanning electron microscopy (SEM) images were used to evaluate the microstructural changes of conditioned specimens. Short-term (up to 270 days) results showed that compared to alkalinity and low sustained load, moisture and elevated temperature played much more important roles in accelerating environmental attack to GFRP bars. Based on the short-term test results, the dominant degradation mechanism for GFRP bars in concrete was found as the deterioration of fiber/matrix interface. A degradation model based on Arrhenius concept and prediction procedures are given, and correlations with other studies and field data are provided. The tensile strength retentions for GFRP bars in saturated concrete subjected to sustained load were predicted. It was found that degradation rates decreased rapidly, but tensile strength retentions at different exposure temperatures converge to a constant value with the increase of exposure time. Beyond fiber-matrix debonding, there is a possibility that other degradation mechanisms such as fiber corrosion may start to dominate the deterioration process of GFRP bars with time.

Comparative Study of the Durability Behaviors of Epoxy- and Polyurethane-Based CFRP Plates Subjected to the Combined Effects of Sustained Bending and Water/Seawater Immersion

“…A fundamental assumption was proposed that the single dominant degradation mechanism (debonding at the fiber-matrix interface [39]) does not change regardless of the immersion time and temperature even under various sustained bending strains, but the degradation rate increases with the immersion temperatures. The degradation rate is expressed as follows [40]   …”

New strategy for anchorage reliability assessment of GFRP bars to concrete using hybrid artificial neural network with genetic algorithm

“…The weights therein are used to measure the contribution that the preceding neuron set to the current one. Biases are added to the sums calculated at each neuron (except input neuron) during the feed-forward process [48,49]. The working principle of a single neuron unit processor is depicted as shown in Fig.…”

Degradation of basalt fiber–reinforced polymer bars in seawater and sea sand concrete environment

“…6 The traditional FRP bars generally refer to glass, aramid, and carbon FRP bars. The glass fiberreinforced polymer (GFRP) bars are more widely used due to their low cost, 7 whereas the use of carbon fiberreinforced polymer (CFRP) bars is limited because of its continuous high cost. 8 Lately, basalt fiber-reinforced polymer (BFRP) bars are being the subject of interest and have an increasing attention for possible replacement of GFRP bars.…”