The use of prestressed near surface mounted fibre reinforced polymers (NSM-FRP) has beenlong acknowledged to be a suitable approach to strengthen and retrofit existing reinforcedconcrete structures. The application of a certain amount of prestress to the FRP prior to itsinstallation provides a number of benefits, mainly related to crack width and deflectionrequisites at serviceability limit state conditions. After transferring the prestress to a structuralelement, some of the existing cracks can be closed, decreasing the vulnerability of the elementto corrosion and, a certain amount of deflection can be recovered due to the introduced negativecurvature. However, these benefits can only be assured if the prestress is properly preservedover time. In this context, three series of reinforced concrete beams, in a total of 10 beams, werestrengthened with a prestressed carbon FRP laminate (CFRP) and monitored for about 40 days.The data obtained from these tests is in this paper presented and analysed. The observed lossesof strain in the CFRP laminate were found to be mainly located in the extremities of the bondedlength, while in the central zone most of the initial strain was well-preserved over time.Additionally, the highest CFRP strain losses were observed in the first 6 to 12 days afterprestress transfer, suggesting that the benefits of prestressed NSM-FRP will not be considerablylost over time.
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