Evaluation of mechanical properties of high strength concrete for prestressed concrete bridge design

Abstract

High strength concrete (HSC) are widely used in prestressed concrete bridges in Texas. However, current design provisions for prestressed concrete bridge structures such as the AASHTO LRFD Specifications (2000) were developed based on material properties of NSC. The objective of this study is to evaluate the applicability of design provisions in the AASHTO LRFD Specifications to HSC and provide statistical parameters of mechanical properties that can be used for future development of probability-based design provisions for HSC. HSC samples were collected from selected precasters considered to be representatives of the precasters in Texas that produce prestressed bridge members. Several collections were made at each precaster to evaluate the effect of design requirements and variability in production of concrete. Concrete specimens were made in the field and then transported to the laboratory for curing and testing. Material testing was performed to determine the compressive strength, splitting tensile strength, modulus of elasticity, and flexural strength (modulus of rupture) at 7, 28, and 56 days. Creep and shrinkage were also monitored. Statistical analyses were conducted to determine the probability distribution, bias factors, and coefficients of variation for compressive strength, splitting tensile strength, modulus of elasticity, and modulus of rupture. Prediction equations for all mechanical properties are evaluated in the context of prestressed concrete design. Recommendations for potential modifications of the AASHTO LRFD Specifications for HSC prestressed members are given.