ORCID Identifier(s)

0000-0002-7697-6216

Graduation Semester and Year

2019

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Civil Engineering

Department

Civil Engineering

First Advisor

Ali Abolmaali

Abstract

Among different components of US highways and roads, concrete pipes are one of the most important parts of these infrastructures. Currently, most of the concrete pipes that are produced in the United States are made from steel reinforced concrete composite, and this system is prone to deterioration and steel corrosion during the service life of these pipelines. In this study, a newly developed composite at the Center for Structural Engineering Research/Simulation and Pipeline Inspection was studied for service life assessment with accelerated aging methods. This composite doesn’t contain any steel reinforcement, and it is reinforced by Polypropylene fibers. At the first phase of this study, synthetic fiber reinforced concrete cylinders were tested to determine the effects of low pH and high temperatures on this material. The results showed that specimens immersed in pH2.5 solutions lost their compressive strength approximately twice of those that were soaked in pH4.2 baths. Immersion duration had a major deteriorating effect on the specimens, and they showed more than 30% compressive strength loss after four months of immersion. At the second phase of this research, actual reinforced concrete pipes with 0.54% fiber volume fractions were immersed in low pH solutions and elevated temperatures. The D-load test results showed that specimens that were immersed in pH2 solutions lost their ultimate D-load capacity by 20% after one year, and pH4 specimens showed 18% load decrease at the same time. The shapes of the curves in these two environments were different. pH2 specimens’ results converged to a steady state load decrease value after five months, and the pattern continued for two other immersion periods. For pH4, the results were still decreasing after each immersion period and based on the trend of the results; it can be anticipated that the curve of this set of tests is going to converge approximately to the same value after a longer immersion period. Furthermore, by using SEM and EDX analysis, the chemical composition of specimens that were extracted from these pipes was analyzed. The results showed that at early stages of the immersion tests, the surface of the pipes in pH4 solution did not absorb a significant amount of sulfur, and it shows that these specimens have not deteriorated significantly. With longer immersion duration, the amount of sulfur element on the surface of the specimens increased gradually, and for pH2, the surface was mostly saturated after 5 months of immersion. For pH4, this value was constantly increasing and similar to the mechanical tests, pH4 results were converging to the same value of pH2 results. For 100-year service life assessment of SYNFRCPs, a curve fitting approach was adopted and based on the curve fitting results it was concluded that these pipes would not lose more than 22.5% of their strength in these corrosive environments after 100 years, which is less than 33% service life criteria. This was determined based on the assumption that pH4 curve will ultimately converge to the steady state part of pH2 results. More than 100 years service life indicates that SYNFRCPs can be used in the U.S. infrastructure systems.

Keywords

Synthetic fibers, Fiber-reinforced concrete, Service life, SEM analysis, EDX analysis, Concrete pipes

Disciplines

Civil and Environmental Engineering | Civil Engineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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