Bond Characteristics of Self-consolidating Concrete for Prestressed Bridge Girders

Abstract

This paper presents the results of an extensive experimental program conducted to determine the material and bond characteristics of a proposed self-consolidating concrete (SCC) mixture for bridge girders. Fifteen full-scale, pretensioned SCC specimens were tested to evaluate the transfer and development lengths of their strand. These specimens included both single-strand and multiple-strand beams, as well as specimens designed to evaluate the socalled top-strand effect. The top-strand-effect specimens, each with more than 20 in. (500 mm) of concrete below the strand, were tested to evaluate the current American Association of State Highway and Transportation Officials' (AASHTO) requirement. AASHTO requires a 30% increase in the strand development length when there is more than 12 in. (300 mm) of concrete below the strand. Before placing SCC in the beams, the prestressing strand was pre-qualified using the large block pullout test. Strand end-slip measurements, which were used to estimate transfer lengths, indicated that the proposed SCC allows strand to meet the American Concrete Institute and AASHTO transfer-length requirements. In addition, flexural tests on the same specimens confirmed that the SCC also meets the current code requirements for development length. Furthermore, the test results indicated that a 30% increase in development length was not necessary to achieve the full tensile capacity of the strand in the top-strand-effect specimens.