Breakout capacity of early age concrete

Breakout capacity of headed studs are currently calculated based on the equations presented in ACI 318-08 and the PCI Design Handbook 6th Ed. These equations were developed using mature concrete. This research examined breakout at early concrete age to determine if a correction factor is needed for the current equations.;Seventy-eight breakout tests were conducted in two separate series following procedures in ASTM E488. When compared to the equations presented in ACI 318-08 and the best fit presented in the research that led to the ACI equation all but one breakout exceeded the value given by the equations based on the compressive strength.;With this information it is suggested that no correction factor is needed to capture the lower bound of the breakout strength. Additionally, a sample design chart is also presented relating the ratio of necessary embedment depth at release strength to the necessary embedment depth at specified strength.