Bond Strength of Glass FRP Bars in Concrete Subjected to Freeze-Thaw Cycles and Sustained Loads

Abstract

In reinforced concrete structures, temperature-induced stresses can be a major concern in regions of drastic temperature changes. FRP reinforced concrete elements are specially susceptible to more damage due to temperature changes because of the mismatching thermal properties between FRP bars and concrete. Furthermore, sustained loads may also damage the bond between FRP bars and concrete and can lead to an unexpected increase of the required anchoring length. Therefore, this research program is designed to investigate experimentally the durability of FRP bond to concrete elements subjected to the effects of freeze-thaw cycles and sustained loads. A FRP-reinforced concrete specimen was developed to apply axial-tension sustained loads to GFRP bars eccentrically located within the concrete environment. Test specimens were subjected simultaneously to the dual effects of 250 freeze-thaw cycles along with sustained load. A total of six test specimens were constructed and tested. The test parameters included bar diameter and concrete cover. After conditioning, each test specimen was sectioned to two replicates (halves) for pull-out test. Another series of twelve unconditioned standard pull-out specimens were constructed and tested as control. Test results are presents in terms of bond-slip relationships and ultimate pull-out strength. Test results showed that freeze-thaw cycles along with sustained load resulted in increase in the bond strength of GFRP bars to con-crete.