Safety concerns and a lack of test data on bond capacity of deformed reinforcing bars embedded in high-strength concrete (HSC) have been reasons that the American Concrete Institute (ACI) 318 building code has imposed an arbitrary limitation of 69 MPa (10,000 psi) in the calculation of tension development and splice lengths. This limitation was first introduced in the 1989 revision of the ACI 318 building code. In an attempt to evaluate the impact of this limitation and develop provisions for its removal, a two-phase investigation was carried out at the University of Nebraska-Lincoln. During both phases of the investigation, 70 beam splices were tested. The parameters studied included diameter, length, and deformation type of the reinforcing bars; amount of transverse reinforcement over the splice length; casting position; and concrete compressive strength. Results of the investigation are used to discuss the differences that exist between normal concrete and HSC, develop hypotheses to explain these observed differences, and suggest alternatives for removal of the current concrete compressive strength limitations existing in the ACI 318 building code for calculating tension development and splice lengths.
