The utilization of industrial and agricultural waste produced by industrial processes has been the focus of waste reduction research for economical, environmental, and technical reasons. Sugar-cane bagasse is a fibrous waste-product of the sugar refining industry, along with ethanol vapor. This waste product (Sugar-cane Bagasse ash) is already causing serious environmental pollution, which calls for urgent ways of handling the waste. Bagasse ash mainly contains aluminum ion and silica. In this paper, Bagasse ash has been chemically and physically characterized, and partially replaced in the ratio of 0%, 5%, 15% and 25% by weight of cement in concrete. Fresh concrete tests like compaction factor test and slump cone test were undertaken was well as hardened concrete tests like compressive strength, split tensile strength, flexural strength and modulus of elasticity at the age of seven and 28 days was obtained. The result shows that the strength of concrete increased as percentage of bagasse ash replacement increased.
The use of an insulating skirt to attenuate galvanic action between mechanically-coupled 6061-T6 aluminum (Al) and electrically conductive carbon fiber reinforced (CFR) polymer-matrix composites (PMCs) was assessed, analyzed and modeled. The galvaniccorrosion current as a function of time between the 6061-T6 Al and CFR PMCs for a range of insulative skirt lengths, l s , and sodium chloride (NaCl) salt loadings, m , in a humidity chamber at 30 • C and 90% relative humidity (RH) were monitored. Polarization experiments were conducted on 6061-T6 Al and conductive CFR PMC electrodes to study the mechanisms governing galvanic corrosion in solutions ranging from 0 ppm chloride (Cl − ) to 20,000 ppm Cl − concentrations. Based on the electrochemical characteristics of Al and the CFR PMC and the ohmic loss within the galvanic couple, a model was developed that related the galvanic corrosion rate (i Galv ) to the value of l s /m , which is the ratio of the insulating skirt length to salt loading. Experimental data from the polarization experiments as well as data from monitoring the galvanic couples in the humidity-chamber galvanic experiments were used to generate plots of log l s /m vs log i Galv , which can be used in design to determine proper skirt length for various environments (based on salt-loading levels) to limit the galvanic corrosion rate to a specified value. Today, many structures, machines and components are comprised of a material system rather than a single type of material.1 Polymers and composites are also being used with greater frequency. For example, only 3 kilograms of polymers were used in automobiles in the 1980s: 2 whereas, today, more than 100 kilograms of polymers are used in a typical automobile.3 Polymer-matrix composites (PMCs) are also being used with greater frequency in commercial, defense, aerospace, automotive and civil-infrastructure industries. 4,5 The advantages of PMCs, especially lightweight carbon-fiber reinforced (CFR) PMCs, are their higher specific strength and stiffness over those of conventional metal alloys. 1,6,7 Some specific examples of CFR PMC products are aircraft fittings and bicycle frames. [8][9][10] As PMCs are being incorporated into material systems to reduce weight and improve performance, they are often put in intimate contact with metal alloys such as aluminum (Al), 1,11 which can induce crevice and galvanic corrosion at the aluminum interface. 1,12,13 If the PMC is insulative such as glass-fiber reinforced (GFR), only crevice corrosion can be induced at the aluminum interface. If the PMC is conductive such as CFR, then galvanic action will also be induced at the aluminum interface.14-20 Figure 1 shows corrosion of a CFR PMC/6061-T6 Al couple exposed outdoors at Marine Corps Base Hawaii (MCBH) (a severe marine test site) for 12 months. Notice that galvanic corrosion also extends beyond the CFR perimeter under the salt and corrosionproduct deposits.Carbon fibers are electrically conductive, relatively inert, and have more noble corrosion potentials compared to ...
Introduction:Dental caries is one of the most prevalent infectious diseases affecting the human dentition. Fluorides are effective anti-carious agents and have been widely used for caries prevention in the form of systemic and topical fluorides. Neutral sodium fluoride (NaF) is commonly used as a topical fluoride agent. A special category of topical fluorides are organic fluorides in the form of amine fluorides (AmF). Researchers have reported that AmF is superior to inorganic fluorides in improving the caries resistance of enamel due to the significant anti-enzyme effect of the organic fragment.Aim:The aim of the present study was to compare the enamel surface micro hardness after topical application of NaF and AmF solutions.Materials and Methods:Twenty fresh samples of sound human enamel were treated with demineralizing solution for 72 h and divided into Group A (treated with NaF) and Group B (treated with AmF) solutions for 3 min twice daily for 7 days. In between treatment, the samples were stored in artificial saliva. The enamel surface hardness was measured with Vickers hardness test at baseline, post-demineralization and post-treatment with two different fluoride solutions (NaF and AmF) and a comparative analysis was made.Results:The increase in mean micro hardness of human enamel after treatment with AmF application was found to be statistically significant (P < 0.01) when compared to the mean micro hardness after treatment with NaF.Conclusion:Fluoride enhances the remineralization process by accelerating the growth of enamel crystals that have been demineralized. It can be concluded from the present study that AmF compounds result in a marked increase in enamel micro hardness when compared to NaF.
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