Bond between galvanized steel and concrete prepared with limestone aggregates

Abstract

PurposeThe purpose of this paper is to elucidate if there is a loss in bond strength between galvanized steel used as reinforcement, and concrete of water‐to‐cement (w/c) ratio of 0.4 and 0.5, after both types of sample were cured for seven, 21 and 28 days in saturated calcium hydroxide solution, and without curing. The air permeability of the concrete was investigated at the interfacial zone.Design/methodology/approachStructural low‐carbon steel and galvanized steel were embedded in concrete samples, prepared with Portland cement type I and limestone (calcite 94‐97 percent) aggregates. The bond strength between the concrete and the reinforcing bars was measured by means of pull‐out tests.FindingsIn concrete of w/c=0.4 the bond for galvanized steel was 5.4±0.5 MPa, while the bond for black steel was 5.8±0.5 MPa, which is 7 percent higher than bond strength measured for samples with galvanized steel rebars. The bond strength for galvanized steel in concrete with a w/c ratio 0.5 was 5.5±0.6 MPa, which was 9 percent higher than the values obtained for black steel, which was 5.0±1 MPa. The total average bond strength of galvanized steel in concrete of w/c ratio 0.4 (5.4±0.5 MPa) and w/c ratio 0.5 (5.5±0.6 MPa) was very similar. They differed by only 2 percent. No decrease in the air permeability at the interfacial zone concrete/galvanized steel was found due to curing.Originality/valueThis research gives quantitative data on the behavior of galvanized steel used as reinforcing bars in concrete, prepared with limestone aggregates. The results might help to increase the reliability of galvanized reinforcing steel used in infrastructure exposed to very aggressive tropical humid marine environments.