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

CI 318-08 appendix D, "Anchoring to Concrete," requires a minimum concrete strength of 2500 psi (17 MPa). Precast concrete elements are often stripped at strengths lower than 2500 psi, raising a concern as to whether the ACI equations are applicable for early-age concrete. This paper provides theoretical and experimental validation of the use of inserts in concrete strengths as low as 1000 psi (7 MPa). Theoretical validation is made by examining the gain in tensile and compressive strength of early-age concrete. Experimental validation comprised 78 pullout tests on headed stud assemblies in concrete with an age as young as 12 hours. The work concluded the following: The tensile strength of early-age concrete rises faster than the compressive strength. The pullout strength of the inserts exceed the theoretical capacity predicted by ACI 318-08 appendix D and the PCI Design Handbook: Precast and Prestressed Concrete.