To Investigate Flexural and Compressive Strength of High Strength Concrete by Addition of Basalt and Steel Fibers at Elevated Temperature

Abstract

High-strength concrete is characterized by dense microstructure, lower porosity, and high durability. Still, it exhibits poor mechanical performance when subjected to elevated temperatures because of its inability to facilitate adequate water vapor dissipation, leading to cracking and spalling. Hybrid fibers were integrated into the HSC matrix to address this inherent limitation. A hybrid fiber-reinforced concrete (HFRC) comprises two or more types of fibers blended within the concrete mixture. HFRC has top-notch thermo-mechanical properties. This research aims to enhance the mechanical properties and thermal stability of HSC under thermal stress conditions. A systematic investigation assessed the mechanical properties, mass degradation, and surface cracking exposed to elevated temperatures. In this study, hybrid fibers (HF) were added to HSC specimens with varying proportions of 0.25%, 0.5%, 0.75%, and 1%, and then exposed to temperatures of 300°c, 600°c, and 800°c at a rate of 50c/min. Empirical findings revealed that hybrid fiber-reinforced concrete exhibited superior mechanical properties relative to the control specimen. This improvement can be due to the basalt fibers filler properties and the hybrid fiber ability to bridge cracks. 0.5% hybrid fiber reinforced concrete demonstrated optimal mechanical properties, whereas concrete with 0.75% hybrid fiber exhibited the least mass degradation. The toughness was increased with the increasing content of HF in concrete It was noted that too many hybrid fibers in concrete can have adverse effects, resulting in clumping. This is not only causing voids but also diminishes the amount of cement present, which in turn minimizes the strength of the concrete.