Concrete breakout capacity of cast-in-place concrete anchors in early-age concrete

Abstract

This paper examines whether current concrete breakout strength models based on concrete compressive strength and embedment depth for mature concrete can also be applied to early-age concrete. Precast concrete elements are often stripped at strengths lower than the minimum required 2500 psi, thus calling into question the applicability of ACI equations for early-age concrete. The authors investigate whether the breakout capacity is properly modeled at early age using the compressive strength or whether it is necessary to include an early-age correction factor. They conduct 78 pullout tests on headed stud assemblies in concrete as young as 12 hours and they examine the gain in tensile and compressive strength of early-age concrete. The study validates the use of inserts in concrete strengths as low as 1000 psi. The tensile strength of early-age concrete was found to rise faster than the compressive strength and the pullout strength of the inserts was found to exceed the theoretical capacity predicted by ACI 318-08 appendix D.