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  • Author: Niraj Kumar Singh x
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Abstract

Fibre reinforced concrete (FRC) presently utilized as a part of special structures subjected to dynamic loads for example airport pavements, expressways overlays, bridge decks and machine foundations. In most cases, FRC contains just a single kind of fibre. The utilization of at least two kinds of fibres in an appropriate mix can possibly improve the mechanical properties of concrete and result in performance synergy. The audit demonstrates that the blend of fibre allows a more powerful control of the dynamic crack development. This review analyses the components for synergistic impacts that gives direction on the fiber and matrix choice.

Abstract

This Expansive soils are very problematic as they are prone to substantial settlements, heave, and possess low bearing capacity. These soils cover more than 20% of the land cover of India and cause obstructions in the development of road networks, railways, and various other construction activities. They make soil stabilization essential. An investigation was carried out to determine the effect of various proportions of randomly-oriented polyester fibers on the shear strength of expansive soil. The unconfined compressive strength of reinforced soil was determined by incorporating four fiber contents, i.e., 0.25%, 0.50%, 0.75%, and 1%, with varying aspect ratios. The effect of various aspect ratios of 20, 40, and 60 were studied in the present work. The stress-strain relationship for different aspect ratios and fiber contents is also presented in the study. The optimum quantity of fibers was found to be 0.75% of the total weight of the soil. A maximum enhancement in the strength of the soil was achieved with fibers with an aspect ratio of 40. The effect of the aspect ratio is significant with a fiber content of 0.50 to 0.75%. The peak strength of untreated soil is found at strain levels of 6-8%, whereas it increases to 10-12% in reinforced soil. A statistical analysis was also performed to develop a regression equation to predict the improvement in the strength of the medium plastic expansive soil used in the study.

Abstract

The present study was undertaken to assess the degree of oxidative stress and toxic effects induced by chromium on hepatic tissue in male Wistar rats exposed to a realistic dosage of Cr(VI) (20 mg/kg/b.w./day) through drinking water, based on the levels of these metals found in the environment, for a duration of 15, 30 and 60 days. The protective effect of melatonin (10 mg/kg) was also studied by simultaneous administration with the metal. Levels of enzymatic and non-enzymatic antioxidants as well as lipid peroxidation were assessed. There was a significant decrease in enzymatic as well as non-enzymatic antioxidants and an increase in the lipid peroxidation level, which were prevented and maintained at near-normal levels by the administration of melatonin in all treatment periods. Metal accumulation was maximal at 15 days, with gradual decreases till 60 days. Histopathological observations also demonstrated the fact that Cr (VI) exposure leads to cytological lesions in the hepatic tissue promoting cellular necrotic/apoptotic changes, while melatonin was able to counteract insults induced by Cr (VI) at all treatment periods. It also prevented alterations in insulin and glucose levels. Overall, the present study suggests a duration-dependent effect of Cr on hepatic oxidative stress and cytotoxicity and shows the potent activity of melatonin in preventing the negative effects of Cr (VI).