Abstract
The need to extend the applicability of the AASHTO LRFD Bridge Design Specifications to high-strength concrete is being addressed by a series of projects being sponsored by the National Cooperative Highway Research Program (NCHRP). Among these projects, NCHRP Project 12-64 is being carried out at North Carolina State University (NCSU) to expand the use of the design specifications to 18,000 psi (124 MPa) for reinforced and prestressed concrete members in flexure and compression. As a part of this project, specimens were tested to determine the material properties of three high-strength concrete mixtures having target compressive strengths of 10,000, 14,000, and 18,000 psi (69, 97, and 124 MPa). The effects of various curing methods were also studied. This study covers the compressive strength, elastic modulus, Poisson?s ratio, and modulus of rupture of high-strength concrete. The study showed that extended curing beyond 7 days resulted in little or no increase in compressive strength. For predicting the elastic modulus of high-strength concrete, the ACI 318-02 or AASHTO-LRFD equation over-estimates the actual modulus while the ACI 363R-92 equation adequately predicts the measured value. The modulus of rupture equation in ACI 318-02 or AASHTO-LRFD gives a good approximation of the modulus of rupture of high-strength concrete when 1-day heat curing and 7-day moist curing are used. The equation from ACI 363R-92 gives a good estimate of modulus of rupture values for continually moist-cured specimens. The Poisson?s ratio of high-strength concrete is generally within the range of that reported for normal-strength concrete.
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