Effectiveness of Various Methods of Jacketing for RC Beams

Abstract

Strengthening of Reinforced Concrete (RC) beams is required due to design errors, deficient concrete production, bad execution processes, damage due to earthquake, accidents such as collisions, fire, explosions and situations involving changes in the functionality of the structure etc. Jacketing has been considered as one of the important methods for strengthening and repairing of RC beams. Jacketing of RC beams is done by enlarging the existing cross section with a new layer of concrete that is reinforced with both longitudinal and transverse reinforcement. In the present investigation, 10 beams of size 150 mm x 300 mm x 2100 mm are cast. 4 RC beams are prepared with smooth surface; on the other hand, 4 RC beams are prepared with chipped surface. Remaining two RC beams are considered as control beams. Eight RC beams have been jacketed using additional reinforcement for 60 mm thickness all-round. Four different methods have been employed for jacketing of RC beams. These methods include use of dowel connectors and micro-concrete, bonding agent and micro-concrete, combined use of dowel connectors, bonding agent and micro-concrete and use of only micro-concrete without dowel connectors and bonding agent, respectively. After 28 days of curing period and completion of jacketing process, these RC beams are tested under two point loading system. Measurements taken during testing were central displacement, failure load, and failure mode & crack patterns. Effectiveness of each type of jacketing methodology on smooth surface was compared with chipped surface for the RC beams. As an outcome of investigation, for smooth surface RC beam, superior performance was observed for the beam jacketed using combined dowel connectors and bonding agent with micro-concrete. For chipped surface RC beams, superior performance was observed for the beam jacketed using only micro-concrete and without use of dowel connectors and bonding agent.