Cost-effective bridge girder strengthening using vacuum-assisted resin transfer molding (VARTM)

Abstract

The objective of this paper is to present the results of a demonstration project to apply externally bonded CFRP fabrics to retrofit a simple span prestressed concrete girder with improved repair and hardening techniques. The technique, Vacuum Assisted Resin Transfer Molding (VARTM), newly introduced to civil infrastructure was implemented in the field within two days without any traffic interruption. As an alternative to traditional hand lay up, VARTM has several processing advantages, like saving the processing time, uniform resin application, intimate contact between each layer of CFRP and concrete substrate ensuring good consolidation to remove void or dry spot, higher fiber volume fraction (about 70%) and greater wettability of the fiber, etc. The performance of the strengthened structures depends on the above potential factors to obtain high structural performance. VARTM uses single-sided molding technology to infuse resin over fabrics wrapping large structures such as bridge girders and saving tooling and processing time. Recently, the VARTM technique has been implemented in strengthening of an I-565 highway bridge girder in Huntsville, Alabama. Laboratory investigation included the construction of small concrete prisms to study the bonding behavior of Carbon Fiber Reinforced Polymer (CFRP) and strengthened concrete beams using VARTM to simulate the performance with and without strengthening. To the end, the process of field demonstration of this newly introduced technique to civil infrastructure has been presented.