CARDIFRCR.Properties and Application to Retrofitting

This paper will describe first the important steps necessary for the manufacture of the high performance fibre reinforced cementitious composite developed at Cardiff University. These steps have been patented (GB 0109686.6) and the class of materials so produced registered under the trademark ® CARDIFRC . It will then describe a new technique of retrofitting damaged and/or understrength RC ® beams. In this technique thin pre-cast strips of CARDIFRC are adhesively bonded to the tension face and, if necessary, other faces of the beams. This technique ensures that the ultimate failure of the retrofitted beams will occur in the gradual flexural mode. It therefore overcomes some of the problems encountered with the existing techniques, based on externally bonded steel plates and FRP laminates, which arise primarily due to the mismatch of their tensile strength and stiffness with that of concrete. The paper will then outline two analytical/computational models for predicting the ultimate moment capacity and the complete load-deflection behaviour of retrofitted RC beams. The first model takes a classical approach involving the tensile contribution from the reinforcing steel and the compressive contribution from concrete, but it also includes the complete tensile contribution of concrete and of the ® retrofit CARDIFRC strips. The second computational model takes a purely fracture mechanics approach and follows the initiation and growth of the dominant flexural crack that eventually leads to the failure of the retrofitted beams. Both computational models predict ultimate moment capacity and load-deflection behaviour that are in excellent agreement with test results. Keyword: RC beams, retrofitting, high performance FRC, adhesive bonding, computational modelling, ultimate moment capacity.