Semester

Summer

Date of Graduation

2006

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

Indrajit Ray

Committee Co-Chair

Julio F Davalos

Abstract

The cracking problem has been one of the major concerns for any concrete bridge deck, especially for cast-in-place concrete decks. The cracking can accelerate deterioration of the structure, thereby increasing maintenance costs and potentially shortening the system service-life. In order to achieve low permeability and reasonable strength, HPC deck mixture designs usually include a higher cementitious material content, which means more shrinkage, and therefore, makes the bridge deck more susceptible to cracking. Thus, further and better understanding of shrinkage and cracking properties of HPC designated for bridge decks is necessary. As part of a comprehensive project, this dissertation is focused on the restrained shrinkage and cracking study of HPC for bridge decks.;A total of 24 HPC mixtures were developed, and tested. The relationships among compressive strength, modulus of elasticity, and direct tensile strength were established. Free shrinkage and restrained shrinkage tests were conducted for selected HPC mixtures. The AASHTO ring specimen test was adopted for the restrained shrinkage study. Based on the results, the relationship among basic material parameters (such as 28-day compressive strength, modulus of elasticity, and 90-day free shrinkage) versus cracking onset days was established. The concept of cracking index was proposed as a convenient way to evaluate the cracking properties of different HPC mixtures. This new concept was validated with actual field data for bridges in WV. A threshold cracking onset day was proposed as the criterion for any acceptable HPC mix designs.;A fracture mechanics method by a combined experimental and FE modeling approach was developed for predicting cracking for the AASHTO ring test. The predicted cracking onset day was in good agreement with the experimental results, and the AASHTO ring test was validated as an effective method for cracking evaluation of HPC mixtures. Finally, comprehensive fracture mechanics tests were conducted for selected HPC mixtures, and a data set for fracture mechanics properties was established as a referance for future studies.

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