Experimental round robin test on FRP-concrete bonding.

When dealing with the strengthening of RC structures by means of FRP(Fiber Reinforced Polymer) sheets or plates, the bond between FRP and concrete is very important: the debonding is a very brittle failure mechanism and must be avoided. In the literature, different experimental set-ups can be found when dealing with FRP-concrete bond tests. It has been observed that different test methodologies may give different values of the debonding force. For this reason, the experimental data obtained from different test campaigns are typically very scattered. For this reason, the characteristic values related with given (low) levels of probability are much lower than the mean values. In the present paper, an extensive experimental campaign on FRP-concrete debonding is described: it has been carried out by five different Italian Laboratories (University of Bologna, “Federico II” University of Naples, University of Sannio, Politecnico of Milan and University of Calabria). The tests were devoted to the definition of a standard test procedure for the bond strength evaluation. According to the Round Robin procedure, a number of concrete prisms strengthened with CFRP plates and sheets have been prepared by the University of Bologna and supplied to the other Universities. The sets of homogeneous specimens have then been subjected to bond tests by the various partners according to different experimental procedures and using different test set-ups. From the analysis of the results, the effect of various parameters characterizing the test procedure has been studied, and some indications concerning the statistical dispersion related to each experimental procedure have been obtained. This study is part of the activities done for the definition of a standard FRP-concrete bond test to be used to evaluate the maximum transmissible force by an FRP anchorage, to be included in the new version of the Italian code for design of strengthening interventions with FRP