Bond performance of strand and wire in early age concrete

Many failures have occurred in the live and dead end anchors of post-tensioned (PT) suspended slabs during the post-tensioning process, prompting a closer study of the behaviour of anchorage zone concrete. In suspended slabs, the post-tensioning loads are transferred to concrete mass via an anchorage assembly that consists in a strand and anchor component. As a part of wider study to establish the failure mechanism of anchorage zone concrete, pullout tests are carried out to investigate the bond behaviour of the strand and wire in early age concrete. Direct type pullout specimens were tested at 3, 4, 7, 14 and 21 days after pouring the concrete. The aim of the experiments was to evaluate the bond performance of strand and wire in high early strength concrete. Selected experimental results and a finite element model representing the pullout tests are presented in this paper. The model is validated based on the load-displacement results. Relevant parameters are discussed