"The study focuses on the effects of common contaminants existing during construction on the bond between concrete and reinforcing bars (rebar) in reinforced concrete. Currently, specifications require any material that adheres to the surface of rebar be cleaned off before placing the concrete and forming the bond. Previous research has helped reveal the contribution of rust and rebar surface conditions to the bond strength but has not focused on construction contaminants. Quantifying reductions in bond strength due to form oils, bond breakers, and concrete splatter will help engineers determine when cleaning rebar is necessary and what kind of safety concerns are present under reduced bond strengths.
The following tests were run on a series of pullout specimens with varying sizes of rebar and concrete strengths. Three types of contaminants, form oil, bond breaker, and concrete splatter, were tested and compared with the control specimens. Ultimate bond strengths and slips were measured for each specimen. A statistical analysis was performed to determine which contaminants have adverse affects on bond strength under service conditions.
The results of the pullout tests reveal that the bond strength is affected by contaminants to a considerable degree. Nearly all of the specimens failed in a pullout failure mode. Prior to this research, a series of beam tests were performed to study the effects of the same contaminants on bond strength. The failure mode of the beam tests was predominantly bond splitting. Ultimate bond strengths were recorded for both of the bond tests and compared with a Dunnett's t-Test. With a 95% confidence level, eleven of the twenty contaminated pullout tests showed significant differences. Using the same statistical methods, the beam tests only exhibited significant differences in three of the twenty-four tests. The failure modes were the most significant factors when determining how the oils and concrete splatter affect the ultimate bond strength"--Abstract, page iii.
Richardson, David Newton
Dharani, Lokeswarappa R.
Civil, Architectural and Environmental Engineering
M.S. in Civil Engineering
University of Missouri--Rolla
xiii, 126 pages
© 2003 Matthew Kenneth Swenty, All rights reserved.
Thesis - Restricted Access
Concrete construction -- Joints -- Defects
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Electronic access to the full-text of this document is restricted to Missouri S&T users. Otherwise, request this publication directly from Missouri S&T Library or contact your local library.http://laurel.lso.missouri.edu/record=b5072335~S5
Swenty, Matthew K., "Contamination effects on the bond strength of reinforcing bars under pullout tests" (2003). Masters Theses. 2385.
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