Semester

Spring

Date of Graduation

2003

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

P. V. Vijay

Committee Co-Chair

Hota GangaRao.

Abstract

This research focuses on the durability of carbon FRP (CFRP) wraps bonded to concrete beams under accelerated and natural aging. Variation in mechanical properties of CFRP wrapped concrete beams due to aging through water immersion, salt and alkaline solution immersion at elevated and freeze-thaw temperature variation are studied. Different parameters evaluated during beam bending tests are: maximum load (moment), deflections, crack width, and deformability factor. Accelerated aging was carried out on 5"x8"x60" wrapped beams under: (1) water immersion at room, 110°F and 140°F temperatures; (2) alkaline and salt solution at room temperature; (3) alkaline and salt solution at freeze-thaw temperature. In addition, 5"x6"x96" and 6"x15"x120" beams wrapped with CFRP fabrics were aged naturally to correlate the results of accelerated and natural aging.;Aging of CFRP wrapped concrete beams in water at elevated temperatures, average experimental load (moment) to theoretical load (moment) capacity of the wrapped concrete beams after 3, 6 and 9 months varied between 1.026 and 1.178. Results of experimental/theoretical load (moment) ratios indicated a trend of reduction in load (moment) capacity with increasing temperatures. Deflection limits of aged beams (l/360, l/240 and l/180) under different conditioning schemes were compared. Crack width limit (0.016in) under different conditioning schemes was also compared. Loads at limiting crack width showed reductions with increasing temperature and aging duration. CFRP strips were extracted from the wrapped beams subjected to bending tests after aging. All extracted CFRP strip specimens were tested in tension. Strength reduction in strips was a maximum of 12.9% under 140°F water aging and stiffness reduction in strips was a maximum of 7.48%.;Accelerated and natural aging results were compared on the basis of stress-temperature-time superposition principles. Based on the correlation of natural aging to accelerated aging, 12.9% strength reduction in carbon wraps bonded to concrete beams is equivalent to about 82 years.

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