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.

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

The compression of typical glass fibre woven fabrics, namely plain, twill, satin, and noncrimped stitch-bonded fabric, was studied experimentally by performing a series of mechanical tests on dry and resin impregnated assemblies of fabrics. This was followed by microstructural studies of corresponding laminates cured under different degrees of compression. The experiments included investigations on the effects of applied pressure, speed of compression, fabric orientation, number of plies and different resin systems on fibre volume fraction,Vf, of the compressed assembly. It was found that the compression of dry fabrics followed a power-law relationship between pressure and Vf where the power law index, b, was determined to be approximately equal to 10.3, 9.8 and 9.1 for assemblies consisting of plain, twill and 5 harness satin weaves, respectively. A mathematical analysis was performed for the viscoelastic compression of resin impregnated assemblies of fabrics and a model was developed incorporating the deformation of the fibre network and resin flow through the reinforcement. A methodology was devised for the geometrical representation of plain weaves in the microstructural analysis of cured laminates. The microstructural studies then provided data for the area and geometrical parameters of the yam cross-section; the mean amplitude, wavelength and phase angle of the yarn waveform and the distance between plies at different compression pressures. Cross-sections of laminates with each of the considered fabrics were compared in terms of fibre area fractions, porosity and void content, for the different compression pressures. The aim for the microstructural analysis was to elucidate the mechanism of compression and to follow the development of fibre and pore structure under different degrees of compression. It was concluded that the compression of resin impregnated woven fabrics could be considered as a combination of four modes of deformation; (a) the elimination of a resin rich interlayer between adjacent layers of fabric; (b) the nesting of layers of fabric by slipping while under compression; (c) the deformation of the yam waveform which results in the reduction of thickness of individual plies and (d) the compression and deformation of the cross-sections of individual yarns.

An attempt was made in this study to eliminate the body rocking behavior of a twenty-three-year-old totally blind male, individual, presently classified as moderately retarded. Consequences were placed upon, rocking behavior in seven experimental phases, employing time-out from a positively reinforcing stimulus as a punisher. More specifically, apparatus were designed in such a manner that rocking would result in elimination of the auditory and visual portion of a television, and in a later phase, the auditory portion of a transistor radio.

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

Reinforcing steel in concrete has been used for many years in roads, bridges and other structures to give strength and durability; concrete has only good compressive strength and reinforcing steel gives the tensile strength to the concrete to sustain both the compressive and tensile load, making concrete structures to be used in the common as well as critical areas. Reinforcing steel that was used in structures predominantly is mild steel, which is considerably cheaper than stainless steel, and more susceptible to corrosion leading to the damage of the structures and less longevity. To solve the problem with the use of mild steel in critical areas, such as bridges; stainless steel is used; which has iron as the main constituents along with the chromium as the major alloying element and various grades are manufactured varying the compositions of steel. To reduce the cost of the stainless steel, some compositions like chromium, molybdenum, nickel are varied; especially the nickel is being replaced by manganese, the cost of which is significantly less than that of nickel. The alternative grades of the reinforcing steel that were used for testing the corrosion resistance are mild steel (400), weldable mild steel (400 W) and four stainless steel 316LN, UNS 24100 (Enduramet 32), 2304, LDX 2101; among them 316LN and UNS 24100 are the austenitic steels (Valbruna) and 2304 and LDX 2101 are duplex steels (Outokumpu). The austenitic steels have no ferritic phase which is making austenitic steel more corrosion resistance than the duplex steels which have almost equal parts of the ferritic and austenitic phases. Concrete that is used commonly as the shield for the reinforcing steel providing the environment to passivate the reinforcement. Concrete has the pH of ~13.5 which is the equivalent to the pH of the pore solution. Its strength and curing time varies due to the water cement ratio and composition and also the environment in which it is placed. Good quality concrete has less permeability and fewer cracks thereby limiting the ingress of the de-icing slats to the reinforcing steel and delaying the onset of corrosion. Corrosion of the reinforcing steels was tested in concrete using both an accelerated exposure test and ASTM A 955M standard for cracked prisms to measure the corrosion rate and open circuit potential, which are quantitative measurement for corrosion. It is hoped that the results will provide a guide for the future use of the alternative grades of the reinforcing steel to be used in the concrete. Reinforcing mild steels were compared to determine if there is any advantage in using the more carefully controlled 400W welding grade, rather than the 400 grade. The service life of structures with the 400 grade of steel is well established and so the data from the 400 grade also provided a relative measure of corrosion resistance for the alternative grades of the stainless steel. Microcell corrosion of the reinforcing steel was monitored by the use of the linear polarization and the corrosion potential. The data for show that there is no significant corrosion on any of the stainless steels after 15 months of measurement, whereas both the mild steels embedded in the concrete corroded fully as confirmed by visual observation of the beams after autopsying The autopsied samples were then analysed for chloride content in the concrete adjacent to the reinforcing bars. This was accomplished by titration. The chloride content on the beams with 400 and 400W grades was found to be higher than the beams with the stainless steels, where the percentage of chloride remained almost the same. Macrocell corrosion tests were performed on the ASTM A 955M cracked prisms and showed changes in corrosion current density in agreement with the accelerated corrosion current density of the stainless steels. The only difference was observed in the corrosion potentials of the 400 and 400W steels, which were more negative in the cracked prisms than in the beams. In summary, all the stainless steels showed evident corrosion resistance both in accelerated and ASTM A 955M prisms tests and no sign of corrosion was found in the stainless steels after 400 days in beams and 200 days in prisms. The regular and weldable steels corroded in both tests in agreement with the data present in research.