TRM Versus FRP as Strengthening Material for Improving Impact Resistance of RC Slabs

Abstract

This study experimentally investigates the effectiveness of textile reinforced mortar (TRM) in controlling the local damage in reinforced concrete (RC) slabs subjected to impact loads. The results are then compared with that of conventional FRP strengthening of RC slabs. The impact tests were conducted using the strike of hemispherical nosed steel projectile on TRM- and FRP-strengthened RC slabs. The unstrengthened specimens considered as control were 600 mm square, 90 mm thick RC slabs. The slabs were reinforced with 8 mm diameter steel rebars at 100 mm c/c spacing both-ways. The slabs were strengthened by externally bonding single layer of Carbon FRP (CFRP) and two layers of TRM on the rear face of the slabs. In TRM strengthening, the textile contained equal quantity of high strength carbon fiber roved in two orthogonal directions. They were simply placed on the top of each other and bonded on a secondary polypropylene line. A commercial polymer modified cement mix was used as mortar in TRM strengthening. The velocity of 40 mm diameter steel projectile was varied within sub-ordinance range and the projectile was made to strike normal to the slab using a gas gun. Based on the experimental testing conducted in this study, it was observed that CFRP and TRM strengthening of RC slabs are effective in reducing the local damage in RC slabs from front and rear faces for the same impact velocity. Both TRM and CFRP strengthening cause increase in the ballistic limit velocity and the perforation energy of RC slabs. Moreover, the CFRP sheet and TRM layer considerably reduce the generation of secondary projectiles which are in the form of flying debris in un-strengthened RC slabs. Overall, among the two strengthening methods studied, the TRM strengthening of RC slabs is found to be either equally good or better than the CFRP strengthening in resisting impact loads.