Experimental Research On The Influence Of Interface Materials And Roughness On Shear Behavior Of RC Beams Strengthened With High Performance Ferrocement Laminate

It is required to strengthen and repair structures in use which are not serviceable or safe because of various factors. A new kind of strengthening method with high performance ferrocement laminate(HPFL) has a lot of superior advantages and the people in structural strengthening domain pay great attention to it and are interested in it more and more.The HPFL strengthening method regularly adopts U-type layer to strengthen RC beams, and the layer tends to debond because of the adhesive strength not enough. Considering that interfacial adhesion is the key of layer working together with RC beams, interface materials and concrete surface roughness were investigated firstly, then the shear behaviour of RC beams strengthened with HPFL was experimentally researched, the main contents of the study are:It was studied one the interfacial adhesive tensile strength and the adhesive shearing strength between the cement-based mortar and the concrete substrate, as well as the exploration of the microstructures of the interfacial zones between the new mortars and the old mortars. The results show that the interfacial agents are good for the interfacial adhesive strength. The pure cement pastes cannot be used as interfacial agents. The mixture of silica fume, expansion agents, and superplasticizer increases the adhesive tensile strength and controls the dry shrinkage obviously. The adhesive tensile strength can be raised up to 60% by using superfine Portland cement instead of ordinary Portland cement.How to measure the roughness of concrete surface? We invented sand-filling method, compared with the sand-pouring method which we were usually used, this method operates simply and measures fast, It's can be used to measure the roughness of large area of concrete in horizontal plane and vertical plane, It's also can be applied to the actual engineering effectively. Based on the sand-filling method, we divided the roughness of concrete surface into three grades.In the study, the shear behavior of 12RC beams strengthened with U-type HPF layer and 1 RC beam was researched. The failure mode and the effect of the roughness of old concrete surface to load bearing capacity was researched. According to the strut-tie model and experiment results, a calculating formula of load bearing capacity considering the the roughness factor ? was put forward.