Date of Award

Fall 2001

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering - (M.S.)

Department

Civil and Environmental Engineering

First Advisor

Methi Wecharatana

Second Advisor

C.T. Thomas Hsu

Third Advisor

M. Ala Saadeghvaziri

Abstract

Many recent innovations in advanced concrete materials technology have made it possible to produce concrete with exceptional performance characteristics. High performance concrete (HPQ is defined as concrete that meets special performance and uniformity requirements that cannot always be achieved routinely by using conventional materials and normal mixing, placing, and curing practices. The importance of HPC to structural engineering is unquestionable. However, HPC is a relatively new material. Some results of research on conventional concrete are not entirely applicable. In this experiment, the main mechanical properties of HPC including compressive strength, modulus of elasticity, and Poisson's ratio were investigated and compared to those of normal strength concrete (NSQ. The stress-strain behavior under uniaxial and cyclic compression as well as cracking characteristics of HPC were also observed in this research and compared to the existing results from the former researchers.

According to the test results of HPC in this experiment, compressive strength was the one that was most spectacularly improved. The modulus of elasticity was also increased, which could be observed from the steeper slope of the ascending part of the stress-strain curve. Poisson's ratio of HPC was found to be lower than that of NSC, which means HPC experiences less lateral deformation than NSC when it is subjected to the same level of loading. It can be seen in the studies of stress-strain behavior for both types of concrete that HPC has a lower ductility ratio than that of NSC. For this reason, it can be concluded that HPC has less capability to sustain large inelastic deformation without substantial reduction in strength. This capability can be improved by using steel reinforcements, mostly in the form of lateral confinements such as in columns. When the results of stress-strain curves were compared to the existing models, it was found that the existing models could be applied to the experimental data. Cracking in HPC was observed to be more localized; the number and length of continuous crack patterns developed at failure are smaller than those of NSC. For this reason, the failure mode of HPC cylinders is typical of that of nearly homogeneous material. Finally, HPC showed less amount of hysteresis under cyclic loading. It can be concluded that HPC has less capability to dissipate energy under loading than that of NSC. HPC also showed less stiffness degradation under unloading and reloading cycles than that of NSC, especially in the post-peak regime.

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