In Norway spruce there's a large natural variation in durability but knowledge about what is causing this variation is missing. In this thesis the focus were put into investigating how the water uptake ability was affected by the influence of heartwood versus sapwood and wood properties such as density and annual ring width. Liquid water permeability was checked trough a modified version of EN 927-5 and samples were also investigated trough the Mycologg Method. The wide grown wood with a coating system (a priming oil and alkyd or acrylate paint) absorbed less water than the narrow grown wood in the permeability test. The Mycologg test showed a clear difference between wide and narrow grown wood. Further research is necessary to examine the impact of wood properties when it comes to water uptake.

A large portion of an airport property is occupied by runways and taxiways, which must be kept in excellent condition to ensure the safety of the airplanes, and the people on board. Any free objects on the airfield can cause damage to aircraft and are a possible danger to both the airplanes and the passengers. However, deterioration of the concrete airfield can be a major hazard and the presence of de-icing and anti-icing fluids may accelerate degradation. The focus of this project was the evaluation and assessment of aircraft de-icing and anti-icing fluids on the deterioration of airfield concrete. These fluids are used to remove and prevent snow and ice formation on aircraft by lowering the freezing temperature of water. The primary component in both fluids is ethylene glycol, while additives, which are proprietary and unknown, are mixed in to control various properties. Very little research has been done regarding the effect of the de-icer and anti-icers on the concrete deterioration. The aim of this study was to gain a better understanding of its influence on the deterioration of airfield concrete through a series of mechanical and electro-chemical tests, as well as microscopic and elemental analysis. Based on the comparative experiments and analyses performed using water, ethylene glycol, de-icer, and anti-icer, it appears that de-icing fluids do not prematurely cause concrete deterioration. In addition, experimental procedures in this study utilized the de-icing fluids as a concentrate, which are unrealistic conditions on an airfield, where dilution occurs from the addition of water and the presence of snow and ice. There was precipitate formation in all cases of cement paste exposure to de-icing fluid, however, which indicates that reactions are occurring and should be investigated further to determine the long term effects on concrete. With respect to the scope of this study, it was determined that the use of de-icers and anti-icers cause no significant detrimental effects on concrete mechanical properties and durability.

Proton Exchange Membrane (PEM) fuel cell stack requires gaskets and seals in each cell to keep the hydrogen and air/oxygen within their respective regions. The stability of the gaskets is critical to the operating life as well as the electrochemical performance of the fuel cell. Chemical degradation of five elastomeric gasket materials in a simulated and an aggressive accelerated fuel cell solution at PEM operating temperature for up to 63 weeks was investigated in this work. The five materials are Copolymeric Resin (CR), Liquid Silicone Rubber (LSR), Fluorosilicone Rubber (FSR), Ethylene Propylene Diene Monomer Rubber (EPDM), and Fluoroelastomer Copolymer (FKM). In order to assess the durability of the materials, observation of chemical degradation level, dynamic mechanical analysis, and micro-indentation test were adopted in this study. This experimental result showed that the influence of the chemical reaction could affect the material surface condition. Also, the chemical reaction could affect material¡¦s mechanical properties had been changed over the soaking time. By considering the level of chemical degradation and mechanical properties, the experimental results showed that EPDM is recommended as the best choice of sealing material for using in a PEMFC.

Titanium oxide (TiO2) films have been actively investigated as many applications because of the mechanical and chemical durability, high refractive index and high transparency. In catalytic and electrochemical applications, it has been utilized as a stable semiconductor electrode for the conversion of solar energy into chemical or electrical energy. Uniform TiO2 films were deposited on conductive glass substrate (ITO/glass) by liquid phase deposition (LPD) with the aqueous solutions of ammonium hexafluoro-titanate and boric acid. Niobium oxide powder and Hydrofluoric acid which add deionized water were used to be Niobium doping solution. Undoped LPD-TiO2 has hydroxyl related defects and Li+ ions will be trapped to degrade the electrochromic durability. For niobium doping, the electrochromic characteristics were enhanced. Niobium doping in TiO2 can reduce hydroxyl related defects. The electrochromic durability was enhanced from 5¡Ñ103 to 1¡Ñ104 times. The transparency ratio was enhanced from 61 % to 70 % at the wavelength of 550 nm. In our experiment, TiO2 films morphology and thickness was characterized by scanning electron microscopy (SEM), structure was characterized by X-ray diffraction (XRD) and surface roughness was measured by atomic force microscopy (AFM), chemical properties was characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR), optical properties was characterized by spectrophotometer (MP-100), and electrochromic characterized by cyclic voltammetry (CHI627C).

Breakwaters are constructed in coastal areas to protect coastal engineering structures from wave actions. Due to economic reasons, natural stones (armourstone) are very frequently used for the constructions of the breakwaters. Considering the functions of the stones at different zones of the breakwaters, various sizes with variable properties of the armourstones are used in breakwaters.Deterioration of armourstones with time in the form of abrasion and disintegration may end up with the damage of the engineering structures. Therefore, it is necessary to investigate the long-term performance and quality of the armourstones, which should be sound and durable. In this thesis, the properties of four limestones taken from two quarries with a known site performances as armourstones in Mersin and Kumkuyu harbors are studied .The site performances and durability of the limestones are compared with the field measurements and laboratory works. For this purpose, the material and mass properties of the limestones are studied. Thus, the information obtained is used to assess long-term durability of the armourstones. The long&amp / #8211 / term performaces of the Degirmen&ccedil / ayi and Tirtar upper level limestones are observed to be good whereas it is rather poor for the Tirtar middle and lower level limestones. Comparison between the predicted and observed durabilities of the armourstones indicated that CIRIA/CUR, RDId, RERS, and wet to dry strength ratio give better results based on their field performances. However, the prediction of the durability of the limestones is poor in case RDIs, average pore diameter, and saturation coefficient are used.

Anxiety disorders commonly co-occur in children and adolescents with an autism spectrum disorder (ASD). Recently, treatment of anxiety using cognitive behavioral therapy (CBT) has been modified and studied in youth with ASD, with results consistently demonstrating positive treatment outcomes. In typically developing populations, CBT gains are well maintained as long as 14-years post-treatment; however, maintenance of CBT has not yet been studied in anxious youth with ASD. Using a sample of 32 youth who previously completed one of three CBT for anxiety in ASD treatment studies, the present study re-assessed parent report of anxiety symptoms in youth, 12-26 months (M = 17.16 Months; SD = 4.32) following treatment completion. Retrospective data from the original studies' screening/baseline and post-treatment time points were used in combination with newly obtained follow-up data to determine treatment maintenance. Compared to baseline, follow-up scores on all measures of anxiety were associated with large effects for treatment. Compared to post-treatment, no significant differences in scores were observed; however, scores on the Pediatric Anxiety Rating Scale suggested a small effect for return in symptoms. While the percentage of individuals with remission of their primary anxiety diagnosis was identical at post-treatment and follow-up, significantly fewer individuals were rated as responders at follow-up as compared to post-treatment. Similar to CBT for anxiety in neurotypical youth, CBT for anxiety in youth with ASD appears to be relatively durable over a one to two year interval. Despite this, a significant portion of participants demonstrate some level of symptom regression. Future study should investigate factors associated with poor treatment maintenance, as well as modifications or additions to treatment protocols (e.g., booster sessions) that may help maintain treatment gains.

Abstract: Concrete cover cracking due to reinforcement corrosion is widely accepted as a limit-state indicator in defining the end of functional service life for existing reinforced concrete (RC) structures undergoing corrosion. Many of the currently available durability prediction models are incapable of providing realistic estimates of remaining service lives of RC structures beyond the corrosion initiation point. Therefore, the need to incorporate the length of the corrosion propagation stage in a comprehensive durability prediction approach has recently received much research attention. Previous research focus however was mostly limited to the case of uniformly corroding reinforcement with only few studies addressing the commonly encountered case of localized rebar corrosion. It was empirically shown in a previous study that localized corrosion can have a mitigating effect on time to concrete cover cracking due to the larger required depth of rebar corrosion penetration (Critical penetration or Xcrit). The present research was focused on developing a model for predicting Xcrit for various degrees of corrosion localization including new cases of highly localized corrosion. Accelerated corrosion testing of controlled anodic regions along axial rebars in sound concrete cylinders suggested that localized corrosion can increase Xcrit by up to about a factor of 10. The effect of corrosion localization on the orientation of corrosion-induced surface cracks was also addressed. Testing of freely corroding pre-cracked RC pipe specimens in a chloride-containing environment indicated that steel corrosion can be localized at intersection regions with the pre-existing cracks and uniformly distributed around the reinforcing steel perimeter. Numerical modeling was undertaken to substantiate the experimentally observed trends on a theoretical basis for various degrees of corrosion localization. A mechanical model was developed to improve understanding of the underlying mechanism responsible for corrosion-induced stresses. A thick-walled multiple-cylinder approach was employed to simulate crack initiation and propagation to account for the residual strength property of concrete after cracking by applying the principles of applied elasticity. For a given concrete cover depth, the amount of Xcrit was shown by modeling to be largely determined by the length of corroding region and the capacity of the induced cracks to accommodate produced rusts. The properties of both concrete-rebar interface and corrosion products were also found to have a significant impact on Xcrit. Based on the model and experimental trends and comparisons with literature data, an improved relationship for the estimation of Xcrit was proposed. An electrochemical model was also formulated to address the possible role of corrosion aggravation due to macrocell coupling in counteracting the mitigating effect of increased Xcrit on time to concrete cover cracking. Findings confirmed that corrosion localization can reasonably be considered a mitigating factor for extending the corrosion propagation stage, and provided more precise quantification to that effect.

The electrochemical oxygen reduction reaction (ORR) steps on a noble metal catalyst in an acidic aqueous electrolyte depend on the nature of the catalytic surface with which the O₂ molecule interacts. It has been assumed that the O₂ molecules interact directly with a bare noble-metal surface. By studying the nature of chemisorbed species on the surface of a metal catalyst as a function of the voltage on the anodic and cathodic sweeps, it is shown here that the O₂ reacts with a surface covered with oxide species extracted from the aqueous electrolyte and not from the O₂ molecules; the ORR is more active when the surface species are OH rather than O. Moreover, the strength of the chemical bond of the adsorbed species was shown to depend on the relative strengths of the metal-metal versus metal-oxide bonds. The Pt-Pt bonds are stronger than the Pd-Pd bonds, and the relative Pd-O bonds are stronger than the relative Pt-O bonds. As a result, the chemisorbed O species is stable to lower anodic potentials on Pd. CO oxidation to CO₂ occurs at a higher potential on Pd than on Pt, which is why Pd (not Pt) is tolerant to methanol. Experiments with alloys show the following: (1) methanol tolerance decreases with the increase of Pt in the Pd-Pt alloys with Pd₃Pt/C showing an initial tolerance that decreases with cycling; (2) OH is formed on Pt₃Co/C and core-shell Pt-Cu/C, which results in a higher activity and durability for the ORR on these catalysts; (3) a 300°C anneal is needed to stabilize the Pd₃Au/C catalyst that forms an O adsorbate; and (4) OH is formed on Pd₃Co/C and Pd₃CoNi/C. These studies provide a perspective on possible pathways of the ORR on oxide-coated noble-metal alloy catalysts. / text

The effect of the sulfates and alkalis on the durability of Portland cement systems was investigated through a series of cube and prism mixes. Durability was assessed using expansion of mortar prisms and the compressive strength of mortar cubes. The study covered a large range of both alkali and sulfate contents using 5 different Portland cements. The alkali contents ranged from 0.27 to 3.8%, the sulfate content (as SO3) ranged from 2.54 to 5%. Doping was done using Terra Alba gypsum and potassium hydroxide. In addition to physical measurements, SEM, XRD, chemical analysis and heat of hydration calorimetry were used for further analysis. Mixing, curing and testing were done at room temperature. The results show that sulfate contents up to the levels used in this study, at low alkali contents and ambient temperature curing, did not adversely affect durability of Portland cement mortars up to 360 days. A correlation was established between expansion and ettringite formation. Increasing the alkali content always resulted in loss of compressive strength, and in some cases, excessive expansion. Excessive expansion was only experienced at the 3.8% level. Alkali levels of up to 2% and sulfate levels of 5% did not result in excessive expansion at room temperature-cure up to the ages reported here. The effect of alkali depended on thecement mineralogical composition, especially C3S content. The addition of alkalis seems to impact the nature of the microstructure and the nature of other hydration products. The addition of sulfates seems to counteract the effect of alkalis, especially on the loss of compressive strength. However, these sulfates may result in other problems as they may be available at any time to form ettringite which may, under certain conditions, result in excessive expansion. It was concluded that sulfate levels on the order of 3-3.6%, did not pose any major durability drawbacks under normal curing temperatures and low alkali contents (<1%). Alkali levels above 1% will adversely affect the durability of Portland cement systems.

Manufactured fine aggregates are a product created when rocks are crushed using a mechanical crusher. With the depletion of sources of natural sands, the usage of manufactured fine aggregates has increased. Manufactured fine aggregates have properties that differ from natural sands; for this reason, the plastic and hardened properties of concrete produced using manufactured fine aggregates differ from the properties of concrete made with natural sands. The main concrete properties affected by the usage of manufactured fine aggregates are skid resistance, workability, and finishability. The aim of this research project was to investigate how manufactured fine aggregates could be used in concrete pavements without causing workability or skid related issues. To improve the workability of concrete made with manufactured fine aggregates, the use of the optimized mixture proportioning method developed by the International Center for Aggregate Research (ICAR) was investigated. Results obtained from this testing were used to make recommendations on how the ICAR method for pavement concrete could be improved The goal of this research was to also develop laboratory tests that could reasonably predict skid performance of concrete pavements made with different types of sand. For this purpose concrete slabs made with different sands were evaluated for friction and texture using a circular texture meter (CTM), a dynamic friction tester (DFT), and a polisher. To ensure that the values obtained at the laboratory related to field performance, test sections constructed with 100% limestone sand and blended sands were evaluated. Laboratory and field test results for skid were used to identify aggregate tests that best correlates with concrete performance. Results show that the micro-Deval test for fine aggregates could be used to predict the polish resistance of concrete laboratory specimen. Results from field testing has shown that if limestone fine aggregates are not blended with siliceous sands, PCC pavements made with limestone sands on truck lanes could experience a large drop in skid resistance within a year of service. Results obtained from laboratory testing showed that blending a small quantity of siliceous sand with limestone sands considerably increased the skid resistance of concrete specimens. / text