Effect of concrete mixture on shear behavior of prestressed concrete girders

A total of six shear-critical prestressed concrete (PC) I-girder were tested to investigate the effect of concrete mixture types on the shear behavior of PC girders. The concrete mixtures examined were conventional concrete (CC), high-performance concrete (HPC), and self-consolidating concrete (SCC) with normal (specified f_c^′=41.4 MPa) and high (specified f_c^′=68.9 MPa) compressive strengths. Test results showed that the HPC girders exhibited a shear behavior similar to the CC girders, irrespective of the concrete compressive strength. The SCC girder with normal-strength concrete (SCC-N) showed a higher ultimate shear strength ratio (V_ult/V_n) and higher ultimate displacement than the corresponding CC girder (CC-N). The SCC-N mixture was designed with a similar coarse aggregate amount but a reduced maximum coarse aggregate size compared with the CC-N mixture. The better performance of SCC-N may be attributed to a better filling ability of the SCC-N mixture than the CC-N mixture. The SCC girder with high-strength concrete showed a lower V_ult/V_n than the corresponding CC girder (CC-H). The lower shear strength of the SCC girder may be attributed to the lower coarse aggregate amount (19% lower) than the CC-H girder. A shear test database of PC girders was established to investigate further the effect of coarse aggregate amount on the girder shear strength. Based on the statistical analysis, the V_ult/V_n and coarse aggregate amount either showed a positive or insignificant correlation. For those groups of test data that showed positive correlation, the slopes of the linear regression of the test data showed that for a 100 kg/m³ decrease of coarse aggregate amount, the V_ult/V_n decreased in average by 18.5%.