Retrofitting Heat-Damaged concrete beams using different profiles of side NSM CFRP strips

This paper investigates the efficiency of using the side near-surface mounted (SNSM) carbon fiber reinforced polymer (CFRP) strips with different profiles to regain the structural performance of heat-damaged reinforced concrete beams. These (150 x 250 x 1400 mm(3)) were prepared using ordinary-strength concrete, cured for 28 days in moist burlap and heat-damaged at temperatures (400-500 degrees C) for three hours before repairing using SNSM CFRP strips of straight, parabolic, and trapezoidal profiles. The mechanical response of control and repaired beams was evaluated under a four-point loading test setup. Furthermore, cracking and failure modes were monitored and characterized during the loading process. The results show that exposing reinforced concrete beams (to the above-elevated temperatures) creates intense cracking on their surface and degrades their mechanical performance. The proposed repairing schemes using trapezoidal and parabolic profiles help avert/reduce the tendency of concrete cover separation. Hence, the overall mechanical performance of heat-damaged beams is noticeably improved. The efficiency of the parabolic profile of SNSM CFRP strips is enhanced with further heat damage. Analytical predictions of ultimate load capacity based on direct measurements of strains in SNSM CFRP strips yield fairly close results to those obtained experimentally.