New procedure for evaluating bond strength of concrete reinforcement

Abstract

The bond strength between concrete and reinforcement is critical to the performance of reinforced concrete structures, including continuously reinforced concrete pavements (CRCP). Unfortunately, a widely accepted test is not available for this critical property. Commonly used procedures apply the load to the reinforcing unit and the load is transferred from the unit to the concrete. Poisson's effects are induced in the reinforcement and a reduction in cross section results. The ensuing failure is not generally representative of the stress transfer mode between concrete and reinforcement in most structures. The proposed procedure obviates the Poisson's effects by applying the load directly to the concrete. Load is transferred to the steel in the vicinity of a preformed crack. Applicability of the procedure is demonstrated using a particular type of flat CRCP reinforcement; however, the procedure has been used on conventional steel and glass-fiber reinforced plastic reinforcement with equal success. The loading rate and instrumentation regime are adaptable to the needs of the researcher. Reinforced portland cement concrete specimens of various strengths were tested to evaluate the procedure and the reinforcement itself. The K-value was found to be satisfactory and comparable to conventional steel rebars. Also the mobilization of yield resistance ratios for the flat units were comparable to conventional steel reinforcing units.