Papers by Keyword: Durability

Abstract: Now abnormal wear between brake shoe and brake drum is found easily with the bad running conditions for motorcycle. Soft tissue like ferrite and graphite in the brake drum are penetrated by the shoe fiber and falls from the surface and pushed to the inner side which causes abnormal wear. Thus material, metallographic and hardness are improved to enhance durability of the brake drum.

Abstract: The test make steel cylinder concrete, PVC protection tube cylinder concrete , spray coatings Outside the cylinder concrete and no protective measures on ordinary cylinder concrete in three different strength grade:C25, C35 and C50 , putting in the freeze-thaw cycle in three kinds of environment of 5% sulfate solution, 5% sulfate + 3% chlorine salt solution and distilled water,Analysis of the Research of Ring pressure of the Pile foundation on the influence of the durability of concrete by measuring the concrete of Pile foundation corrosion mass loss before and after freezing and thawing.Experiments show that:the concrete with protective measures almost has no mass losses with the level of pile foundation concrete in the same corrosive environment,that, s to say ,the durability is good.While the unprotected concrete has mass losses after the freeze-thaw action hitches in three kinds of solution,And the largest mass loss is in the mixed solution,the durability is the worst.

Abstract: Due to its outstanding performance and merits, Self-Consolidating Concrete (SCC) has attracted a wide attention from scientists, researchers and engineers all over the world. At present, many research activities have been conducted in developing and evaluating SCC and its related technologies. However, existing performance evaluation methods of are mostly limited in the field of material, while structure performance evaluation methods of SCC are rarely reported. As we all known, the lifetime of the SCC structure is mainly subject to its material, structural and durability performances as a whole. Undoubtedly, it is crucial for us to study and develop a sound structural and durability performance evaluation method to complement the existing material performance evaluation methods. As such, the structural and durability performance evaluation method of SCC was studied in this paper.

Abstract: Direct Methanol Fuel Cells (DMFC) are an attractive power source for applications in the low kW-range like pallet trucks or uninterruptable power supplies. A significant problem during the past years, however, was the limited durability of DMFC systems. While single cells could be operated for thousands of hours, DMFC systems degraded significantly often within less than 1,000 hours.In an evolution of six generations of DMFC systems in the kW power range over the past decade, we identified the main reasons for degradation. Causes for fast degradation had to be removed first in order to identify what leads to slower degradation over several hundreds or thousands of hours. Interactions of cells and system components also had to be considered.As a result, the operating conditions of all cells must be carefully controlled by suitable operating algorithms and reproducible manufacturing technologies, in order to avoid high potentials on the anode, which would lead to ruthenium corrosion and subsequent poisoning of the cathode catalyst. All components of the stack and the peripheral system must be corrosion-proof and free from contaminants that might leach into the membranes. Finally, a DMFC system for a pallet truck was operated in a realistic load cycle for 20,000 hours.

Abstract: The carbonation of Portland-cement-based materials involves the reaction between atmospheric CO₂ and calcium ions in the pore solution. The formation of calcium carbonate is responsible for a decrease in the pH of the pore solution from 12.5 to 9, thus leading to the depassivation of steel reinforcements and their possible corrosion, and can also lead to efflorescence (white crystals formed on the surface). In metakaolin-based geopolymer activated by sodium silicate, in which calcium is almost non-existent, the presence of CO₂ will lead to the formation of sodium carbonates. Since geopolymer can be carbonated, the risk of corrosion or efflorescence needs to be assessed. A pH study of the geopolymer pore solution showed a very fast decrease compared to OPC, with almost total carbonation after only 14 days. In natural atmospheric CO₂ conditions, it was found that the formation of sodium carbonate did not lead to a decrease of the pH to below a value around 9, thus limiting the risk of corrosion by depassivation of reinforcement, but the large amount of carbonate suggested a significant risk of efflorescence. A study of accelerated carbonation performed under an atmosphere of 50% CO₂ highlighted the formation of sodium bicarbonate resulting in a lower pH of the pore solution and a much larger amount of product formed. Finally the study of efflorescence carried out by semi-immersion tests in natural or accelerated conditions confirmed the different nature of the crystals formed (sodium carbonate or bicarbonate) but showed no significant impact on the amount of carbonated products. This study thus demonstrates that the accelerated carbonation test had very limited usefulness, given the rapidity of the natural reaction. Furthermore, it was found that this test did not reproduce reality as it led to different reaction products.

Abstract: The development of advanced materials is increasingly leading to integration of functions into materials and components. This drive in technological innovation is strongly felt in many traditional fields, like textiles or ceramics. Over the last twenty years, the so-called "traditional" ceramics industry for tile production has undergone a profound technological reorganization, both in production technologies and automation of the different production phases, but new products and possible new applications are still needed, thereby opening up new markets. In this paper a critical review of the industrial and scientific effort to obtain antibacterial and self-cleaning coating for ceramic tiles is reported. The main patents and scientific papers in the field are reported as well as some final results obtained by the authors on the evaluation of the durability of photocatalytic coating deposited on industrial ceramic tiles.

Abstract: In the present paper the durability of fly ash geopolymer mortars compared to that of cement mortars is investigated. Geopolymers can improve the ecological image of building materials, especially when their production is based on industrial by-products such as fly ash. Three series of fly ash based geopolymer mortars were prepared using calcareous sand to fly ash ratio (S/FA) varying from 0.5 to 2. In addition, cement mortar specimens were prepared using cement CEM I 42.5 N and CEM II 32.5 N. Durability of geopolymer and cement mortars was evaluated by means of compressive strength development, acid resistance, chloride diffusion and sulfate resistance. It was found that fly ash can be effectively used to produce geopolymer mortars with calcareous sand. Geopolymers exhibit competitive compressive strength compared to that of cement mortars. Geopolymer mortars develop their maximum compressive strength a few days after their casting. Geopolymer and cement mortars exhibit satisfactory resistance to sulphate attack. Cement mortars, generally, show better behaviour (compared to geopolymers) in chloride diffusion. Finally, geopolymers indicate improved performance against acid attack, compared to that of cement mortars.

Abstract: The surfaces of building materials are constantly exposed to the actions of environmental factors, pollutants of inorganic and organic origin as well as to microorganisms, which significantly contribute to corrosion phenomena.The application of coatings decreases the negative action of the pollutants minimizing their direct contact with the substrate. Different types of coatings with additional functions have been developed. A specific problem of these applications is the lack of compatibility of the photocatalysts with the surface of the building materials and the detachment of potentially toxic TiO₂ nanoparticles. In the present study, this problem was solved by the proper immobilization of TiO₂ nanoparticles onto the photocatalyst support, layered double hydroxides (LDHs). The newly formed coating possesses acceptable porosity for a porous building material (porosity within the range of 30-46 %) and satisfied photocatalytic activity, as well as mineralogical compatibility with the substrates (mortars, renders, bricks). Additionally, a positive effect considering the self-cleaning phenomenon was attained.

Abstract: The growing focus on issues related to the control of CO₂ emissions, energy conservation and waste recycling pushes the construction industry to tackle the challenge of sustainable development. The production of ordinary Portland cement (OPC), main product of the sector, is one of the most polluting in terms of CO₂ emissions, thus finding alternative binder is becoming an urgent matter. Geopolymers are largely investigated for this purpose, but studies concerning the durability of reinforced conglomerates prepared with alkali activated binders are only few. The present work aims at investigating the durability performances of steel reinforced geopolymer mortar samples based on carbon fly ash in comparison with OPC mortar. The effect of different Na₂O/SiO₂ molar ratios in the geopolymer mixes is evaluated in terms of mechanical and microstructural properties as well as corrosion resistance in a chloride rich environment. The obtained results show that under the same severe environmental conditions more limited chloride amounts penetrate in reinforced fly-ash geopolymers where a better corrosion behaviour is also detected up to a week of exposure for samples with a nominal Na₂O/SiO₂ molar ratio equal to 0.12 and 0.14. Instead, the corrosion resistance is quite similar to that of reinforced OPC mortar when a period of three months is considered.

Abstract: The results of accelerated testing machine and mechanism parts metallurgical equipment such as bodies of rotation on the wear resistance and contact strength developed installation, showing promising applications for the production of mill rolls all weld metal.