Instrumented dry-cast reinforced concrete pipe (DC-RCP) specimens in which corrosion of the reinforcing steel had initiated were selected to accelerate the corrosion. Type C and type F DC-RCP were used. An anodic current density of various magnitudes (0.5 μA/cm2, 1 μA/cm2 and 2.5 μA/cm2) was applied during the corrosion propagation stage. The specimens were placed in high humidity and selected specimens were later covered with wet sand. Selected specimens were terminated for visual examination and gravimetric analysis. Typically, the reinforcement potentials during the accelerated corrosion period were more negative for F specimens compared to C specimens. The C specimens experienced ~2× more corrosion than the F specimens. The accumulated corrosion products did not cause cracks. A method was developed that allows for modest corrosion acceleration during the corrosion propagation stage of DC-RCP. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

The corrosion propagation stage of D-CRP (types F and C) was tested under immersion in water, high humidity, and covered with wet sand. The half-cell potential, linear polarization test, and electrochemical impedance spectroscopy measurements were performed. Selected specimens were terminated after 300 days of exposure and visually inspected. Based on corrosion potential measurements obtained during the corrosion propagation observation, and calculated corrosion rate based on LPR measurements: all specimens were actively corroding. Additionally, EIS-Rc values were calculated for FS, CS and CH specimens. The Rc_EIS were generally greater than Rc_LPR values. EIS spectra for CI and FI specimens usually included mass transport limitations, as these specimens were immersed. Both type of specimens immersed in water (FI and CI), appeared to have higher corrosion rate based on LPR-Rc. However, upon autopsy it was revealed that a more modest amount of corrosion occurred on the reinforcing steel of FI and CI terminated specimens. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

Every year millions of construction workers are exposed to dust in levels that create a hazard to them (Fundukian, 2011). Their environment is contaminated by activities such as cutting, chipping, grinding and sanding building materials. The Occupational Safety and Health Administration (OSHA) refers to this general collection of building materials debris and fine particulates as nuisance dust. Some of the particles in nuisance dust possess properties that make them especially hazardous, such as their shape or specific gravity. It has been found by the Center for Disease Control (CDC) that inhalation of quantities of silica dust above the permissible exposure limit (15.0 mg/m3) causes a deterioration of the outside lining of the lung.This research seeks to limit this exposure by a pretreatment process using acid application and then absorbed moisture content that reduces airborne particulate during the removal of cement stucco surfacing materials. Successful pretreatment would allow removal of CSSM from substrates such that the release of airborne particulates does not exceed the permissible exposure limits (PEL) found in the 29 CFR-Table Z-3 for mining applications (15-mg/m3). / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2015 / FAU Electronic Theses and Dissertations Collection

Steel corrosion in reinforced concrete is a major concern to transportation agencies nationwide because of the expenses incurred for repair and ultimate shortening of bridge life. Cathodic protection (CP), as a remedy, has been applied to reinforced bridges in the US since 1974. However, application of this technique is largely empirical, lacking fundamental understanding. In order to optimize the performance of a CP system, it is important to monitor the rebar potential with respect to a reliable reference electrode. Moreover, because of potential variation in the concrete, reference cell placement is fundamental to ensure effective protection. The work plan was divided into two parts: laboratory scale experimentation and computer simulation. In the experimentation section, the response of graphite probes was compared to that of an Orion silver-silver chloride electrode. Graphite probes behaved as well as the standard electrode. Furthermore, the home-made graphite probes behaved the same as the commercial ones. This will allow much greater experimental latitude since the home-made probes are much more economical than the commercial ones. A finite difference code was developed to assess the performance of cathodic protection. The potential distribution in a two dimensional geometry of a concrete block with a sprayed zinc anode at one boundary and an iron cathode at the other side was calculated under cathodic protection. The equations were solved by means of a Gauss-Seidel iterative method with the help of an overrelaxation factor. An interval halving method was used to solve for nonlinear boundary condition at the iron. The effects of concrete pore saturation, concrete cover, and applied potential were studied to determine the degree of protection and proper placement of the reference electrode in concrete. Furthermore, a sensitivity analysis was performed versus input parameters: concrete conductivity, oxygen mass transfer coefficient, and oxygen reduction polarization parameters. The results of the simulation showed that the center of the rebar is less protected than the other locations. Therefore, the reference electrode should be located as close to the center as possible. / Graduation date: 1995

In recent years, it has been discovered that some structural elements of the I-10 and I-35 corridor passing through San Antonio, Texas (San Antonio Y) are suffering from premature concrete deterioration related to alkali-silica reaction (ASR) and/or delayed ettringite formation (DEF). While there is considerable evidence of materials related distress, the degree of damage to structural capacity has not been quantified. In a comprehensive search of literature, very little research has been identified that quantifies the amount of structural damage caused by ASR and/or DEF on the load carrying capacity of structural piers. Due to the fact that this integral stretch of interstate highway sees a large volume of traffic, it is desirable to determine a method of assessing the degree of structural damage, and the necessity of taking remedial actions. The purpose of this thesis is to develop an assessment methodology which can be used by The Texas Department of Transportation (TxDOT) to evaluate the current and future integrity of structural elements in the San Antonio Y. The key steps included in the methodology are conducting a literature review on the effects of ASR and/or DEF on the structural properties of reinforced concrete, evaluating in-situ engineering properties of existing concrete, investigating the basis for the original design, and performing an experimental investigation to determine the effect of cracking on the load carrying capacity of typical SAY piers. This thesis presents the findings from this research. / text

Premature concrete deterioration due to alkali-silica reaction (ASR) and delayed ettringite formation (DEF) is a significant problem all over the world. In cases where these mechanisms were not initially prevented, mitigation is critical to halt expansion and cracking. The main objectives of the research presented herein were to study the effect of ambient relative humidity (RH) on rates of concrete expansion, to determine RH thresholds below which expansion due to ASR and/or DEF may be suppressed, and to evaluate coatings intended to lower the internal RH of concrete and thus minimize future potential for damage. Results from testing showed that the RH threshold for ASR was below 82%, the RH threshold for DEF was below 92%, and the RH threshold for combined ASR and DEF could be about 83% for the materials tested. Furthermore, it was shown that some coatings are effective in reducing ASR- and DEF-related expansion by lowering the internal RH of concrete. / text

The durability of Reinforced Concrete (RC) structures in the Marine environment is causing serious concern in the structural infrastructure. Reinforced concrete structures, exposed to aggressive environments, are expected to last with little or no maintenance for long periods of time. However, one of the most serious environmental exposures that causes degradation is Chloride Diffusion, due to shrinkage, atmospheric corrosion, and tide-induced wet and dry conditions at the air-water interfaces of coastal structures. Therefore, chloride diffusivity, which correlates with the electrical resistivity, has a significant impact on the durability of concrete. Concrete chloride diffusivity has been experimented by multiple agencies and researchers on sound concrete, but there is a considerable need for investigation of the durability of cracked concrete in the marine environment. The two test methods carried out are presented: Standardized American Society for Testing and Materials (ASTM) C1202 for Rapid Chloride Permeability (RCP) and ASTM D257 for Surface Resistivity (SR), and Nordtest (NT) Build 492 for Rapid Chloride Migration (RCM) and Bulk Resistivity (BR) for both sound (uncracked) and cracked (micro and macro) concrete. The limitations of the ASTM method, due to measurements before the steady-state migration is reached, does not account for leakage in cracked concrete, and the heating of the specimen due to higher current that increase the conductivity are indicated. The Rapid Chloride Migration test provides for the non-steady state of diffusion. Again, Bulk Resistivity, in contradistinction to Surface Resistivity is more accurate for cracked concrete. The correlation betweeen RCM-BR are plotted. Chloride Permeability/Migration is an important parameter that governs the Durability of Concrete. The principal contribution is the highlighting of the inadequacy of the current widely used standard ASTM C1202 for diffusivity testing, and the need for revision with further investigation. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

Cantilevered reinforced concrete columns with a lap splice of the longitudinal reinforcement near the base can induce high moment demands on the splice region when lateral loads are present on the structure. Code design specifications typically require a conservative splice length to account for these high moment demands and their consequences of bond failure. The required splice length is calculated as a function of required development length, which is a function of the bond between the reinforcement and the surrounding concrete, and a factor depending on the section detailing. However, the effects of concrete deterioration due to alkali silica reaction (ASR) and/or delayed ettringite formation (DEF) may weaken the bond of the splice region enough to overcome the conservative splice length, potentially resulting in brittle failure of the column during lateral loading. This thesis presents the following results obtained from an experimental and analytical program. * Fabrication of large-scale specimens of typical column splice regions with concrete that is susceptible to ASR/DEF deterioration * Measurement of the large-scale specimen deterioration due to ASR/DEF accelerated deterioration * Analytical model of the column splice region based on flexure theory as a function of the development length of the reinforcement and a factor to account for deterioration of the bond due to ASR/DEF * Experimental behavior of two large-scale specimens that are not influenced by premature concrete deterioration due to ASR/DEF (control specimens). This experimental data is also used to calibrate the analytical model. The conclusions of the research are that the analytical model correlates well with the experimental behavior of the large-scale control specimens not influenced by ASR/DEF. The lap splice region behaved as expected and an over-strength in the splice region is evident. To account for ASR/DEF damage, the analytical model proposes a reduction factor to decrease the bond strength of the splice region to predict ultimate performance of the region with different levels of premature concrete deterioration.

This research focuses on the characterization of damage accumulation in concrete specimens. Specifically, a nonlinear vibration technique is used to characterize the damage introduced by ongoing alkali-silica reactions (ASR). The nonlinear resonance testing consists of an analysis of the frequency response of concrete specimens subjected to impact loading. ASR introduces a third gel like phase, which can be expansive in the presence of moisture. The result of ASR is the formation of microcracks and debonding between aggregate and cement phases. Collectively, these changes act to increase the specimens' nonlinearity. As a result, it is found that the concrete samples exhibit nonlinear behavior; mainly a decrease in resonance frequency with an increasing level of excitation strain. The relationship between the amplitude of the response and the amount of frequency shift is used as a parameter to describe the nonlinearity of the specimen. The specimens used in this research are of varying reactivity with respect to ASR, which is induced in accordance with ASTM C 1293. The level of nonlinearity is used as a measure of damage caused by the progress of ASR throughout the one year test duration. These nonlinear resonance results are compared to the traditional measures of expansion described in the standard. The robustness and repeatability of the proposed technique is also investigated by repeated testing of samples assumed to be at a specific damage state. Finally, a petrographic staining technique is used to complement nonlinearity measurements and to further gain understanding of ASR. The results of this study show that the proposed nonlinear resonance methods are very sensitive to microstructural changes and have great potential for quantitative damage assessment in concrete.

De nos jours, le béton est le matériau de construction le plus utilisé dans le monde en raison de ses performances mécaniques, sa facilité de mise en oeuvre, son coût compétitif et sa « recyclabilité ». Toutefois, compte tenu de son caractère fragile en terme mécanique et de sa faible résistance à la traction, il est souvent renforcé par des armatures métalliques qui lui confèrent une bonne ténacité et une meilleure aptitude à supporter les efforts de traction. Ce composite béton-armature ne peut cependant assurer efficacement son rôle que si les deux composants sont étroitement liés l’un à l’autre. C’est donc dans la qualité de l’adhérence que réside l’efficacité du transfert des efforts entre les deux matériaux. Or, dès la mise en place des ouvrages en béton armé et pendant toute la durée de leur exploitation, différentes actions et agents agresseurs peuvent modifier la qualité de cette adhérence. Il peut s’agir de phénomènes naturels comme le gel/dégel et l’action du dioxyde de carbone atmosphérique, ou des sollicitations accidentelles comme l’incendie ou encore l’action de certains agents spécifiques comme les chlorures et les sulfates. Notre objectif dans cette thèse est de qualifier les modifications d’adhérence qui résultent de quatre types de sollicitations couramment rencontrées dans la vie des ouvrages en béton armé: l’effet des températures élevées, l’effet de la carbonatation, l’effet des cycles gel/dégel, l’effet de la corrosion. Nous évaluons la qualité de l’adhérence par la mesure de la résistance à l’arrachement et par l’analyse du comportement résiduel sous sollicitation mécanique. La technique d’émission acoustique est utilisée pour localiser en temps réel, l’endommagement du matériau sous sollicitation. Les applications de notre étude concernent non seulement les armatures et inserts classiques du béton armé mais aussi les nombreux dispositifs constructifs des structures mixtes acier – béton qui utilisent les liaisons par goujons pour relier les deux matériaux. / Nowadays, concrete is the most used construction material in the world because of its mechanical performances, its ability to be molded or cast, its competitive cost and its recyclability. However, concrete has a low ductility and a relatively low tensile strength compared to other construction materials. Therefore, concrete is often reinforced by steel rebars to improve the ductility and tensile strength. Nevertheless, to make reinforced concrete being highly efficient material, the two components need to be correctly bonded each to other. The bond quality the efficiency of the force transfer between rebar and concrete surrounding ensures. In fact, since the casting of concrete and during the service life of reinforced concrete structure, various actions such corrosion action, freeze/thaw attack and chemical attack etc. may affect the bond quality. The objective of this PhD research work is to qualify the changes of adhesion property causing by four types of action which frequently takes place in the service life of reinforced concrete structures: the effect of high temperatures, the effect of carbonation, the effect of cycles freeze/thaw, the effect of corrosion. The concrete-rebar bond quality is evaluated by doing pull-out tests under static mechanical action and measuring the bond strength and analyzing residual behaviour. Moreover, the acoustic emission technique is used to locate the cracks and evaluate the cracking evolution in real time. The founding of this study can be also extended to apply to other concrete-steel structures like composite structures in which headed studs are used to connect steel profiles to concrete.