Performance of full scale self consolidating concrete structural elements in shear, bond and under corrosion attack

Abstract

This research program focuses on investigating the shear resistance, bond characteristics, and corrosion performance of self-consolidating concrete (SCC) compared to those of normal concrete (NC). The shear strength, cracking behavior, and deflection characteristics were tested in full-scale beams. A total of twenty reinforced concrete beams, with no shear reinforcements, were tested under mid-span concentrated load until shear failure occurred. The experimental test parameters included concrete type/coarse aggregate content, beam depth and the longitudinal reinforcing steel ratio (ρw). The beam depth ranged from 150 to 750 mm while the shear span-to-depth ratio (a/d) was kept constant in all beams, The two longitudinal reinforcing steel ratios used were 1% and 2%. The performance of SCC/NC beams was evaluated based on the results of crack pattern, crack widths, loads at the first flexure/diagonal cracking, ultimate shear resistance, post-cracking shear resistance/ductility, load-deflection response, and failure modes. Code-based equations or procedures are used to predict the crack width, first flexural cracking moment/load, and ultimate shear resistance as well as to simulate load-deflection response. The bond strength of reinforcing bars embedded in full-scale heavy reinforcing beams (4000 mm length x 1200 mm depth x 300 mm width) made with SCC was investigated and compared with that of NC. The flowability of SCC mixture through the dense reinforcement was visually monitored from a transparent formwork. The bond stress was tested for bars located at three different heights (150 mm, 510 mm, and 870 mm from the bottom of the beam) and at different concrete ages (1, 3, 7, 14 and 28 days). The bond stress-free end slip relationship, the top bar effect, and the effect of age on bond stress were investigated in both SCC and NC beams. Bond stresses predicted based on some major Codes were compared with those obtained from experiments. The corrosion of steel reinforcement embedded in full-scale SCC beams was investigated and compared to that embedded in NC beams. The corrosion performance of 400 mm width x 363 mm depth x 2340 mm length beams containing epoxy and non-epoxy coated stirrups was monitored by partial immersion in a sodium chloride solution and an impressed current. Half-cell potential tests were implemented at 25 different locations on each beam to evaluate the probability of steel corrosion along the beam length/perimeter. At the same locations where the half-cell potential tests were implemented, the chloride ion content near the bar surface was measured to study the variation of the chloride-ion penetrability along the beam length/perimeter. The mass loss and bar diameter degradation along the length of each bar were investigated at the end of the test. Predicted rebar mass loss due to corrosion based on Faraday’s law was compared with experimental mass loss for each beam.