Low and high temperature performance of near surface mounted FRP strengthened concrete slabs

Abstract

Near surface mounted (NSM) FRP reinforcement has recently emerged as a promising alternative technology for strengthening concrete structures in both flexure and shear, as opposed to externally bonded FRP strengthening systems. Available research to date has focused primarily on overall member behaviour and/or the various parameters that affect the bond performance of either rectangular NSM strips or round NSM bars. No research has apparently focused on the effect of low or high temperature exposure on NSM FRP performance. It has been suggested by numerous researchers that NSM FRP reinforcement may outperform externally bonded FRP strengthening systems at elevated temperatures, but this assertion has yet to be supported by test results. An extensive review of NSM FRP technology is presented. The results of an experimental program conducted on twenty-three (23) concrete NSM FRP strengthened slab strips are presented to investigate their high (up to 200˚C) and low (-26˚C) temperature flexural performance. The effect of using one of two different adhesive systems (epoxy and cement-based) and two different NSM groove widths (6.4 mm and 3.2 mm) is also studied. An innovative photo imaging instrumentation technique is validated against traditional instrumentation techniques for the first time in NSM flexural testing. A numerical layer model is presented and compared against test results. It is demonstrated that low temperature exposure has no measurable negative effects on the flexural performance of the slab strips tested. From high temperature exposures, it is shown that the cementitious adhesive outperforms the epoxy adhesive system, allowing the strengthening system to remain structurally effective for more than 5 hours at 100°C under sustained loads.