The Rheological, Mechanical, and Durability Behavior of Self-Compacted Concrete (SCC) Mixed with Hybrid Fibers after Exposure to High Temperatures and Cycles of Freezing and Thawing

This study presents the influence of hybrid fibers basalt (BF), steel (SF), and polypropylene (PP) on the rheological, mechanical properties, and durability behavior of self-compacted concrete (SCC). Seven SCC mixes with varying fiber levels (0%, 0.05%, 0.1%, and 0.15%) and combination were cast. Mechanical properties such as compressive strength, splitting tensile strength, and flexural strength were investigated after exposure to high temperatures (400 °C, and 600 °C) and 200 freeze-thaw (F/T) cycles. The rheological properties of fresh self-compacting concrete (SCC) were investigated using slump flow and V-funnel flow. Results showed a significant decrease in rheological properties of SCC with increase in fibers volume. The specimens' compressive strength was shown to increase as the volume ratio of the fibers increased to 0.15%. The optimal fiber mixture for SCC compressive strength was (BF-SF-PPF), which is approximately 18.5% more than the control specimen. The SCC groups, which included fibers exposed to high temperatures and 200 freeze-thaw cycles, had mechanical properties that were higher to those of the control group. The ability of concrete to absorb water was improved by the addition of fibers to SCC. The ultrasonic pulse velocity UPV is improved more when specimens reinforced with double hybrid fibers (basalt and steel) are used than when specimens reinforced with triple hybrid fibers.