The penetration of chloride ions plays a crucial role in reinforcement corrosion and affects the durability and service life of marine structures. The problem is even more acute once cracking occurs in a concrete member. The presence of cracks is shown to have a significant impact on chloride penetration into concrete. It has been recognized, for concrete cracked in flexure, the chloride diffusion coefficient in the tension zone is higher than that in the compression zone. Even a single crack in the tensile zone could contribute to a higher diffusion coefficient compared to that of uncracked members. In this study, the influence of flexural cracks on chloride ion penetration into reinforced concrete beams has been investigated experimentally and a two-dimensional theoretical model is developed. The experimental study investigated the influence of multiple flexural cracks on the chloride diffusivity of reinforced concrete beams and on the corrosion rate of reinforcing bars. The size of the reinforced concrete beams tested is 200 x 250 x 2200 mm with 20mm concrete cover. The beams were pre-cracked using a compression testing machine and the crack widths induced were maintained between 0.1 mm to 0.2 mm. The chloride profile was determined after 1 month, 1 year and 2 years of immersion in 3.0% NaCl solution. The measured chloride profiles of the beams with multiple cracks are compared to those obtained from the uncracked (control) beam. An observation was also made on the effect of cracks on the corrosion development of steel bar after two years of immersion in salt solution. Chloride concentration varied linearly with the depth of crack (at crack planes). A twodimensional model using finite element analysis is developed to evaluate the chloride penetration into cracked concrete. This model was used to verify the chloride penetration data which is obtained from the experimental results. The prediction of chloride ingress, using the two dimensional model agrees well with the short-term and long-term chloride profiles.

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains ix, 56 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 51-52).

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 122-129). Also available via the Internet.

No description available.

Thesis (Ph.D.)--Aberdeen University, 1994. / Title from web page (viewed on Mar. 22, 2010). Includes bibliographical references.

The composite FRP rebars research at Oregon State University was initiated in 1993 principally to develop a non-metallic hollow reinforcement. It was recognized that the tensile properties of such reinforcement are unquestionably superior to steel, but its performance in concrete could be problematic. The bond between FRP rebars and concrete was identified as a critical area of concern. The purpose of this study is (i) to analyze a variety of FRP and steel reinforcing units; (ii) to advance the knowledge of bond mechanism, failure modes, and parameters influencing the bond strength; (iii) to compare composite rebars to conventional steel and to assess their applicability as reinforcing members. Commercially available FRP rebars were investigated. Particular emphasis was given to a hollow glass FRP rod designed at Oregon State University. Several parameters were investigated, including: failure mode, concrete compressive strength, rebar diameter and circumference/cross section ratio, embedment length, concrete cover, and microstructure of the composite rebars. It was recognized that the ASTM C234-90 pull-out standard is test of concrete strength. Therefore a modified pull-out test was developed for evaluating the bond strength behavior. A newly developed European bond test procedure was compared with locally modified version of the pull-out method. The new procedure was used for the first time in the United States. The study demonstrated a phenomenon, not reported in the published research at this time, defined as a size effect. The size effects result in lower bond strength with increasing area of the interface between FRP bars and concrete. The next phase of the research was dedicated to the hollow glass FRP rebar. The goal was to compare its bond properties to conventional steel and solid FRP bars. The study led to two new phenomena not described in the literature previously. Results showed that the concrete compressive strength does not significantly affect the bond strength. This observation was in contradiction with the bond strength theory which considers the concrete strength as major variable. The second observation revealed significant difference in bond performance between bars with different microstructures. It is recommended that microstructure of the FRP bars be considered as a variable when investigating bond strength. / Graduation date: 1998

Rational decisions about cost-effecctive bridge designs, optimum inspection strategies and repair are hampered by the absence of comprehensive data on the mechanical performance of deteriorated concrete elements. One of the most important causes of concrete deterioration is corrosion of the steel reinforcement. In general corrosion of reinforcement is believed to affect the structural performance of concrete elements in two ways. First, by increasing the stress concentration on the rebar cross section, due to corrosion-induced reduction in the rebar cross-sectional area, which may lead to premature failure if the stresses in the rebar exceeds its yield strength. Second, by weakening the transmission of stresses in the composite resulting from the loss of bond strength between concrete and the steel reinforcement and the growth of cracks due to the formation of corrosion products at concrete/reinforcement interface. As part of a 'Brite Euram' Project, sponsored by the E.E.C., the author has developed procedures for assessing the influence of reinforcement corrosion on the structural performance of reinforced concrete flexural members. The experimental work was carried out on reinforced concrete beams which were subjected to accelerated reinforcement corrosion and then tested in flexure. Corrosion was induced in reinforcement by means of two external power supplies. The results obtained from the experiments show that reinforcement corrosion reduced the stiffness and the load carrying capacity of concrete beams significantly. Structural analysis and reliability analysis techniques were applied to the results of the study, and simple models for predicting the flexural load capacity of corroded beams were produced. The effect of reinforcement corrosion on the bond strength at the steel/concrete interface was also investigated. The results of the study provide evidence to indicate a trend of increased bond strength associated with small degrees of corrosion in reinforcement (≤0.4% reduction in rebar diameter).

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 797-811). Available also in a digital version from Dissertation Abstracts.

Thesis (M.S.)--West Virginia University, 2003 / Title from document title page. Document formatted into pages; contains xiii, 186 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 147-155).

Thesis (Ph. D.)--University of Washington, 1981. / Vita. Includes bibliographical references.