Experimental investigations on the flexural behavior of compression-cast seawater sea-sand concrete beams reinforced with CFRP bars

To address the corrosion problems, environmental concerns, and achieve green and sustainable civil engineering practices, this study designed several compression-cast seawater sea-sand concrete (SSC) beams reinforced with corrosion-resistant carbon fiber-reinforced polymer (CFRP) bars (i.e., FRP-SSC beams) and their flexural behavior was experimentally investigated through four-point bending tests. Twelve FRP-SSC beams were designed, including three normal-cast and nine compression-cast ones. The critical parameters included the concrete casting forms, water-to-cement (w/c) ratios, and reinforcement ratios of CFRP bars (rho f). Effects of the concrete casting methods, w/c ratios, and rho f on the flexural responses of FRP-SSC beams were comprehensively studied. In addition, the flexural theorems were used to derive the prediction models of the equivalent stress block parameters (i.e., epsilon cm, alpha 1, and beta 1) and flexural strength (Mu) of compression-cast FRP-SSC beams. Moreover, based on the experimental results, effectiveness and accuracy of the proposed flexural strength design models were verified by using the existing design specifications. Finally, the results indicate that, (1) compression-cast FRP-SSC beams with the larger rho f (1.78 %) exhibited bending failure featured by compression concrete crushing, whereas that with the smaller rho f (0.75 %) shown splitting failure; (2) The cracking moments of compression-cast FRP-SSC beams increased significantly owing to the higher compressive strength and elastic modulus of compression-cast concrete (CCC); (3) Because of the pronounced brittleness of CCC, the improvement of the ultimate flexural capacity of compression-cast FRP-SSC beams was limited; (4) Under the same moment level, the maximum crack widths of compression-cast FRP-SSC beams were smaller than their normal-cast counterparts; and (5) the proposed flexural strength design models could yield more accurate, safer, and conservative predictions of flexural strength for both normal- and compression-cast FRP-SSC beams.