Flexural strength recovery of heat-damaged RC beams using carbon nanotubes modified CFRP

This paper reports on the influence of using carbon nanotubes (CNTs) on flexural strength recovery of heat-damaged RC beams repaired with carbon fiber reinforced polymer (CFRP) composites. Twenty-two RC beams were prepared, heated at 500 degrees C and 600 degrees C, repaired, and then subjected to four-point loading. The nanotubes were incorporated in the composite systems by either using CNT-modified epoxy resin and/or CNT-modified sizing agent. The flexural behavior was characterized based on failure mode, crack patterns, and load-displacement response. The morphology of the fractured surfaces and interfaces were examined using a scanning electron microscope. Experimental results revealed that the addition of CNT enhances the capability of the composites to recover the flexural load capacity and stiffness of heat damaged beams. The improvement depends on the level of damage of the heated beams. SEM images showed that adding CNTs enhanced the interface adhesion between carbon fiber, epoxy, and concrete. This enhancement facilitated the load transfer thus the efficiency of the repair technique. (C) 2017 Elsevier Ltd. All rights reserved.