Effects of bar-placement conditions on steel-concrete bond

Abstract

Vertical sections exhibit a variety of factors that affect the bond between the embedded steel bars and the concrete, like casting position, concrete characteristics, and compaction procedure. The results obtained in this project indicate that bond strength decreases if the concrete depth below the horizontal bar increases, primarily because of the water-stop effect underneath the bar, and of the settlement of fresh concrete. This effect increases for larger values of water content and water-cement ratio (w/c), which normally cause an increase in slump, and a decrease in stability of concrete (resistance to bleeding, settlement, and segregation). However, very good bond properties were achieved by using self-compacting concrete (SCC) tested versus standard concrete mixes, is a demonstration that in the case of SCC higher slump values do not mean lower bond properties.