Environmental concerns have brought about a push to replace non-biodegradable products that are made from non-renewable resources. Investigations regarding use of wood fibers and other biomass as a raw material for biodegradable foams and sponges are an example of such a replacement. Foams made at least partially of biomass can be created using cellulose from wood fibers once the cellulose is converted into a fluid form. Polyurethane foams can be made from polyols containing as much as 50% biomass by combined dissolution of wood and starch. Sponges can be made completely from cellulose regenerated from a viscose rayon solution, and the effect of using wood fibers as reinforcement material within the cellulose matrix of such sponges was studied. The effect of fiber content and fiber length on absorbance, swelling, density, air to cellulose ratios, bound water, and tensile was determined.

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.

This thesis investigated corrosion of a reinforcing steel bar embedded in concrete and the effect of corrosion coupling on the bar/concrete interface induced by the variation of corrosion potentials with concrete depth. Two separate numerical models were used to simulate the corrosion process which included: a two-dimensional finite element model for mass transport of oxygen and chloride to the bar/concrete interface; and, a one-dimensional model for the corrosion current flow through the electrolyte induced by corrosion potential differences on the bar/concrete interface. A novel approach to corrosion modeling in reinforced concrete that had not been identified in the literature was used. This new approach, incorporated: variable solution conductivity developed from concentrations within the pore solution; anodic and cathodic areas modified to maximize corrosion current through the electrolyte; and, kinetics of corrosion set by the pore solution chemistry. Various reinforcing configurations and moisture conditions were evaluated within the simulation to obtain insight into the effect these variables have on corrosion potentials measured on the concrete surface and the corresponding corrosion currents generated on the bar/concrete interface. Variables related to bar diameter, concrete cover, and bar spacing where all shown to affect corrosion potentials and current densities on the bar/concrete interface and the concrete surface where field measurements are obtained. Moisture conditions were found to have the largest impact on corrosion potentials and current density’s on the bar/concrete interface. When relative humidity’s of 90% or higher were used, simulated corrosion potentials on the concrete surface under high chloride conditions were found to reach values identified in ASTM C876 and Alberta Transportations Deck Testing Guidelines that indicate active corrosion. However, when moisture conditions were reduced to below 90% relative humidity, simulated corrosion potentials on the concrete surface for high chloride concentrations did not achieve values that indicate a high probability of corrosion. This result suggests a secondary mechanism must be present on the bar/concrete interface that changes the chemical composition within the pore solution to shift the kinetics of corrosion to an environment that will produce the negative corrosion potentials recognized as indicating a high probability of corrosion. Therefore, a new mechanism is proposed that outlines the process necessary for the pore solution on the bar/concrete interface to transition the kinetics of corrosion to an actively corroding state at low relative humidity. This mechanism requires local acidification of the pore solution along portions of the bar where anodic processes are increased due to the presence of chloride and reduced oxygen availability. Reaching this environment requires free OH- to be consumed without replenishment from the surrounding environment by either diffusion from high pH areas or dissolution of the hardened portions of the pore structure. The proposed mechanism begins with corrosion by-products formed when Fe2+ reacts with free OH-, precipitates from the pore solution onto the pore structure as Fe(OH)2. Once precipitated, the contact area between pore solution and hardened portions of the pore structure are reduced which restricts the dissolution process for restoring OH- removed from the electrolyte. Additionally, precipitation of Fe(OH)2 reduces the flow of OH- from the surrounding high pH zones as the pore structure is restricted. Both mechanisms result in a pH gradient being formed with acidified zones created on the bar/concrete interface in the anodic regions. These acidified zones cause the kinetics of corrosion to transition from a passivated state, towards an environment similar to carbonation.

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.

Magister Artium (Sport, Recreation and Exercise Science) - MA(SRES) / Physical inactivity is increasing among adolescents worldwide and may be contributing to the increasing prevalence of overweight and obesity. South African adolescents are physically inactive and obesity has become an alarming trend. Physical activity behaviours have multiple levels of influence that include predisposing factors, reinforcing factors and enabling factors. This study aimed to identify the predisposing, reinforcing, and enabling factors of physical activity and which ones were the strongest predictors of physical activity participation among adolescents in the Western Cape. The study sample was conveniently selected from two schools in the Metropole South Education District. Using the children’s physical activity questionnaire and the children’s physical activity correlates questionnaire, a sample of 348 participants completed the questionnaires. Demographic variables were analysed using descriptive statistics which included means and standard deviations. Pearson correlation and regression analysis were performed to determine the relationship between the variables and to determine the strongest predictors of physical activity overall. Parental influence (r=0.236, p<0.01), peer influence (r = 0.012, p<0.05), perceived physical activity self-efficacy (r=0.212, p<0.05) and perceived physical activity competence (r = 0.192, p < 0.05) were all strong predictors of PA. However, parental influence was the strongest predictor overall (r=0.236, p<0.01). Adolescents are more likely to participate in physical activity if their parents encourage, support and participate in physical activity with them.

M.Ing. / Design parameters for ferritic type stainless steel structural members do not exist and is needed. This study attempts to find design parameters for ferritic type stainless steel compression elements. The ferritic type stainless steel under consideration in this study is Type 3CR12 corrosion resisting steel, which is a modified Type 409 stainless steel. The purpose of this study was to determine the limiting web width-to-thickness and flange width-to-thickness ratios for the prevention of local buckling in axially loaded hotrolled Type 3CR12 corrosion resisting steel columns. Experimental data was obtained in an ongoing study on the limiting width-to-thickness ratios for elements in compression. No conclusion on this aspect can be reached at this stage of the investigation

Reinforced concrete poles are commonly used as street lighting and electrical transmission poles. Typical concrete lighting poles experience very little load due to torsion. The governing design loads are typically bending moments as a result of wind on the arms, fixtures, and the pole itself. The Canadian pole standard, CSA A14-07 relates the helical reinforcing to the torsion capacity of concrete poles. This issue and the spacing of the helical reinforcing elements are investigated. Based on the ultimate transverse loading classification system in the Canadian standard, the code provides a table with empirically derived minimum helical reinforcing amounts that vary depending on: 1) the pole class and 2) distance from the tip of the pole. Research into the minimum helical reinforcing requirements in the Canadian code has determined that the values were chosen empirically based on manufacturer’s testing. The CSA standard recommends two methods for the placement of the helical reinforcing: either all the required helical reinforcing is wound in one direction or an overlapping system is used where half of the required reinforcing is wound in each direction. From a production standpoint, the process of placing and tying this helical steel is time consuming and an improved method of reinforcement is desirable. Whether the double helix method of placement produces stronger poles in torsion than the single helix method is unknown. The objectives of the research are to analyze the Canadian code (CSA A14-07) requirements for minimum helical reinforcement and determine if the Canadian requirements are adequate. The helical reinforcement spacing requirements and the effect of spacing and direction of the helical reinforcing on the torsional capacity of a pole is also analyzed. Double helix and single helix reinforcement methods are compared to determine if there is a difference between the two methods of reinforcement. The Canadian pole standard (CSA A14-07) is analyzed and compared to the American and German standards. It was determined that the complex Canadian code provides more conservative spacing requirements than the American and German codes however the spacing requirements are based on empirical results alone. The rationale behind the Canadian code requirements is unknown. A testing program was developed to analyze the spacing requirements in the CSA A14-07 code. Fourteen specimens were produced with different helical reinforcing amounts: no reinforcement, single and double helical spaced CSA A14-07 designed reinforcement, and single helical specimens with twice the designed spacing values. Two specimens were produced based on the single helical reinforcement spacing. One specimen was produced with helical reinforcement wound in the clockwise direction and another with helical reinforcement in the counter clockwise direction. All specimens were tested under a counter clockwise torsional load. The clockwise specimens demonstrated the response of prestressed concrete poles with effective helical reinforcement whereas the counter clockwise reinforced specimens represented theoretically ineffective reinforcement. Two tip sizes were produced and tested: 165 mm and 210 mm. A sudden, brittle failure was noted for all specimens tested. The helical reinforcement provided no post-cracking ductility. It was determined that the spacing and direction of the helical reinforcement had little effect on the torsional capacity of the pole. Variable and scattered test results were observed. Predictions of the cracking torque based on the ACI 318-05, CSA A23.3-04 and Eurocode 2 all proved to be unconservative. Strut and tie modelling of the prestressing transfer zone suggested that the spacing of the helical steel be 40 mm for the 165 mm specimens and 53 mm for the 210 mm specimens. Based on the results of the strut and tie modelling, it is likely that the variability and scatter in the test results is due to pre-cracking of the specimens. All the 165 mm specimens and the large spaced 210 mm specimens were inadequately reinforced in the transfer zone. The degree of pre-cracking in the specimen likely causes the torsional capacity of the pole to vary. The strut and tie model results suggest that the requirements of the Canadian code can be simplified and rationalized. Similar to the American spacing requirements of 25 mm in the prestressing transfer zone, a spacing of 30 mm to 50 mm is recommended dependent on the pole tip size. Proper concrete mixes, adequate concrete strengths, prestressing levels, and wall thickness should be emphasized in the torsional CSA A14-07 design requirements since all have a large impact on the torsional capacity of prestressed concrete poles. Recommendations and future work are suggested to conclusively determine if direction and spacing have an effect on torsional capacity or to determine the factors causing the scatter in the results. The performance of prestressed concrete poles reinforced using the suggestions presented should also be further investigated. Improving the ability to predict the cracking torque based on the codes or reducing the scatter in the test results should also be studied.