A feasibility evaluation of utilizing high-strength concrete in design and construction of highway structures
The objective of this investigation was to evaluate the feasibility of using high-strength concrete in the design and construction of highway bridge structures. A literature search was conducted; a survey of five regional fabrication plants was performed; mix designs were studied in the laboratory and in the field; and three series of tests consisting of a total of nine full-scale specimens were conducted The first series included 3 pile specimens tested in flexure. Each of the pile specimens had a 24-in. (610-mm) square cross section with a 12-in. diameter void running its full length. All the pile specimens were 24 ft (7.31 m) long. The pile specimen concrete, at the time of testing, had an average compressive strength of 8,067 psi (55 MPa) The second series consisted of three full-size bulb-tee specimens. Flexural tests of two bulb-tee specimens are reported. The third specimen is being used for determination of long term behavior Three shear tests are also reported. These shear tests were performed using the ends of the two flexural test specimens. Since the shear specimens were taken from the flexural specimens, they had the same cross-sectional configuration and concrete strength as the flexural specimens The fabrication and driving of a single 130 ft (39.6 m) pile specimen is reported. The pile specimen had the same cross-sectional configuration as the pile specimens tested in the laboratory. The concrete of the pile specimen had an average 28-day compressive strength of 10,453 psi (72 MPa) Based on this investigation, the following conclusions are made: (1) High-strength concrete with strengths of 10,000 psi (69 MPa) can be produced using regionally available materials, however, quality control measures presently in use must be upgraded. (2) AASHTO Standard Specifications for Highway Bridges conservatively predicted the behavior of the pile and girder specimens in the area of flexural strength, cracking moment, inclined cracking, shear strength, strand transfer length, effective width of top flange, estimation of prestress losses, modulus of elasticity, and modulus of rupture. (3) Girder camber/deflection measurements were consistent with values calculated using conventional methods. (4) High-strength concrete can be used effectively in long piles. The higher tensile strength and higher precompression is particularly valuable in soft driving conditions where tensile driving stresses are high. (5) Steam curing of high-strength concrete may reduce strength development at later ages. (Abstract shortened by UMI.)