Bond characteristics of a Self-Consolidating mix for PC bridge girders

Results from tests used to determine the material and bond characteristics of a proposed SCC mix for bridge girders in the state of Kansas are presented. Eleven full-scale, pre-tensioned SCC flexural specimens were tested to evaluate the transfer and development lengths. These specimens were single-strand specimens that included specimens designed to evaluate the so-called “top-strand” effect. These top-strand specimens, with more than twenty inches of concrete below the strand, were tested to evaluate the current AASHTO requirement of a thirty percent increase in the development length when more than the twelve inches of concrete is cast below the strand. Prior to casting the beams, the pre-stressing strand was pre-qualified using the Large Block Pullout Test procedure. Strand end-slip measurements, used to estimate the transfer lengths, indicated that the proposed SCC mix meets the ACI and AASHTO requirements. In addition, flexural tests on the same specimens, confirmed that the SCC mix also meets the current code requirements for development length. Furthermore, the test results indicated that a thirty percent increase in development length was not necessary to achieve full tensile capacity of the strand in the “top-strand” specimens.