FRP Strengthening of Beams Made with Recycled Concrete Aggregate

摘要

Synopsis: Coarse recycled concrete aggregate (RCA) has been studied as a replacement for natural aggregate (NA) in concrete for decades. RCA is still predominantly used in non-structural applications such as filler, road sub-base, drainage material, and low quality concrete. However, there is increased interest in using RCA in new structural concrete due to restrictions on landfilling of construction and demolition (C&D) waste and on the scarcity of natural aggregates, especially in urban megacities. The compressive strength of concrete with coarse RCA is typically 15-30% less than that with NA. This feasibility study was conducted to evaluate the effect of FRP strengthening on RCA beams as compared with NA beams also strengthened with FRP. Four RCA and four NA beams were strengthened in flexure and in shear using hand laid-up carbon-epoxy FRP materials. A combination of longitudinal strips on the beam soffit and intermittent closed hoop wraps along the length were used. The FRP-strengthened beams were designed to yield and then fail in compression with the FRP still attached. The results of the testing are described. The ability of FRP strengthening to, (1) change the failure mode of RCA beams, and, (2) to improve the reliability of RCA concrete beams constructed or repaired with FRP materials is discussed. It was found, surprisingly, that the FRP-strengthening was effective in increasing the capacity of the RCA beams. This is attributed to a different failure mechanism of the RCA beams from that of the NA beams tested.