A new method of controlling shrinkage cracking in repaired concrete structures using an interface layer of carbon fiber reinforced cement mortar

Bonding an overlay of new concrete onto the damaged concrete is a usual repair method. Because of the different shrinkage rate of the new and old concrete, restrained shrinkage cracks will appear in the new concrete. The cracks will reduce durability and strength of the repaired structure. A new repair method using an interface layer of carbon fiber reinforced cement mortar between new and old concrete was developed in this paper. The new method was found to be very effective in reducing shrinkage cracking of repaired beams and slabs. Comparing with normal repaired beams, the maximum observed width of the resulting cracks was decreased by up to 43%, the cumulative width was decreased by up to 78%, the cumulative length was decreased by up to 73%, and the total area of the cracks was decreased by up to 81%.