Anchorage resistance of CFRP strips externally bonded to various cementitious substrates

This paper presents a study on the anchorage capacity of Carbon Fiber Reinforced Polymer (CFRP) strips bonded to a cementitious substrate used for concrete surface reprofiling. The structural strengthening of a large-scale prestressed concrete girder in the framework of a bridge retrofitting project by means of prestressed CFRP strips required the levelling of an initial negative camber of about 2–4 cm. Both midspan and girder end situations were investigated with lap-shear and prestress force-releasing tests. Four different solutions regarding the levelling material, i.e. three mortars applied by hand as well as dry shotcrete, were tested. The results in terms of strain, slip and total anchorage resistance are presented and compared. In the end, dry shotcrete is recommended for the girder application. In addition to a very convincing bond behavior, the application is, despite the necessity of involving a specialized company from the field, clearly less time-consuming and easier. The retained solution represents an interesting approach for future applications in bridge retrofitting when an even surface is necessary for bonding CFRP strips.