TESTING THE STRENGTH AND DURABILITY OF STEEL FIBER CONCRETE AT HIGH HEAT (KEY IJP************948)

• Mehwish Javid,Er. Rekha Devi

Abstract

Concrete, being the most often used construction material globally, is extensively used. However, it has a vulnerability in stress because of its intrinsically fragile characteristics. In order to deal with this issue, the integration of SF into concrete has emerged as a feasible technique to improve its ability to deform without breaking. Investigating the effect of heat on concrete with SF reinforcing is of great interest due to the widespread use of concrete and its exposure to high heat caused by fire accidents and other reasons. Despite the existence of several investigate on this topic, there has been little focus on examining the impact of the aspect ratio of SF in concrete. So the primary objective of this investigate is to examine the effectiveness of integrating SF with varying aspect ratios into the concrete using experimental techniques. The goal is to assess the improvement in performance of concrete components when exposed to both low and high heat. The experimental review was done in numerous phases. In the first phase, various tests were performed at room heat, including assessments of workability, strength in compression, and split strength in tensile. The objective was to examine the reaction of concrete and identify the most effective amount of fibres for aspect ratios of 65 and 55, ranging from 0% to 1.50% with increments of 0.25%. The next phase included assessing the mechanical characteristics of the samples using the established optimal fibre doses. This assessment was carried out at high heat of 125C, 250C, and 375C. The conducted mechanical tests included strength in compression, split strength in tensile, and flexural strength evaluations. The findings demonstrated that the addition of SF with different concentrations and aspect ratios had a considerable consequence on the mechanical characteristics of concrete. The concrete's workability was shown to diminish as the aspect ratio of the fibres increased. The 65 and 55 aspect ratio mixes had a maximum drop of 39% and 36%, respectively, associated to the control mix. Nevertheless, the adding of SF caused in a notable enhancement in the strength in compression, ranging from about 13% to 38%, as well as an improvement in the split strength in tensile, ranging from 7% to 65%, under normal heat conditions. The findings indicate that the ideal fibre volume percentages for generating the greatest improvements in compressive and split strength in tensile are 0.75% for an aspect ratio of 65 and 0.50% for an aspect ratio of 55. Upon subjecting the samples to increased heat for a duration of 3 hours, ranging from 125C to 375C, a decrease in weight was noted. The weight loss may be due to the volatilisation of water content from the concrete at elevated heat. Additionally, the samples subjected to a heat of 375C exhibited minor fractures on their surface as a result of water loss and the development of tensions at elevated heat. The strength in compression of the FRC exhibited an upward trend as heat climbed, although at a reduced pace. Nevertheless, the split strength in tensile and flexural strength shown an initial rise until reaching 250C, after which they declined at elevated heat. In addition, a mathematical model was created to forecast the remaining strength of steel FRC for any combination of ingredients at higher heat. The model included variables such as heat, fibre volume, and fibre content. The correlation between these characteristics and the remaining strength was compared to the empirical findings. The review demonstrated that the created mathematical model accurately predicted the residual strength of steel FRC at high heat, as it closely matched the experimental results.