Date of Award

Spring 2002

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Civil Engineering - (Ph.D.)

Department

Civil and Environmental Engineering

First Advisor

C.T. Thomas Hsu

Second Advisor

Perumalsamy Balaguru

Third Advisor

John R. Schuring

Fourth Advisor

Jay N. Meegoda

Fifth Advisor

Pedro Munoz

Abstract

High performance concrete (HPQ has recently become a widely used concrete construction material for modem buildings, bridges, and pavements, etc. To produce such a better quality of concrete, chemical and mineral admixtures such as fly ash, slag cement, and silica fume, ground granulated blast furnace slag, as well as air-entraining agents are commonly used in the field construction. It has been found that high perforinance concrete can improve the workability, ultimate strength and durability of the concrete. However, the enhancement of ductility in concrete, and concrete structures as a whole is still inconclusive and needs more research. The ductility can be found from the behavior of stress-strain curve, therefore, a well-defined stress-strain curve can be used to understand its ductility and other mechanical behavior. In this research, a series of compression tests are conducted.

Silica fume has been used to get high performance silica fume high strength concrete. The shape of the ascending part of the stress-strain curve for high performance silica fume high strength concrete behaves a more linear and steeper curve. The slope of the descending part also exhibits a steeper curve for the high strength concrete as compared to that of the normal concrete. Fly ash also has been used to improve concrete characteristics. The use of fly ash in concrete increases the ductility of concrete by 9.8%, but the improvement is not significant and thus more research work is needed in this field. Steel fibers and confinements increase the ductility of high performance concrete, thus concrete does not fall even after reaching high strain value.

This research presents a complete stress-strain behavior and its empirical equation of high performance concrete under compression. Once the ultimate strength and concrete strain are known, only one or two parameters are needed to study the ascending and descending behavior of concrete. The proposed empirical equations also study the effects of steel fibers and/or steel hoops, and can be found useful in designing modem high performance concrete structures. The comparison between the experimental and analytical results shows a good agreement.

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