Breakout Capacity of Headed Anchors with Delayed Installation

Abstract

The objective of this research was to evaluate the impact on concrete breakout capacity of anchors in tension due to delay in the nstallation using the puddle-in technique. The puddle-in technique is the process of installing an insert (anchor) into fresh concrete once the surface has been finished. The installation was delayed by up to 160 minutes. Another installation method, pre-installation, is the attachment of the insert to the formwork or reinforcement before the concrete has been poured. The results discussed were obtained from research conducted at Curtin University of Technology, Perth as an undergraduate research project. Twenty four anchors were tested in tension. The principal test variables were anchor installation delay (and hence, loss of slump of the concrete) and concrete compressive strength at the time of anchor tension testing. The anchor type and edge distances were kept constant. The anchors all failed due to concrete cone breakout failure mode. Several statistical analyses were conducted on the data; it was found that the imposed anchor installation delay did not affect anchor concrete breakout capacity, even when installation was delayed significantly resulting in zero slump concrete. However this conclusion is valid only when the anchors were tested with concrete compressive strengths around 15 MPa. The anchors tested at lower concrete compressive strength did exhibit a decrease in capacity when anchor installation was delayed.