Slurry Infiltrated Fibrous Concrete (SIFCON) is a subtype of fiber-reinforced concrete. In the manufacturing of SIFCON, the fibers are first placed into the molds and then infiltrated with cement slurry that normally has a low water-to-cement ratio. This manufacturing technique is distinct from the normal production of fiber reinforced concrete. The fiber content can be significantly increased by preplacing the fibers in SIFCON. Due to the high strength cement-based matrix and high fiber content, the energy absorption and postcracking strength ability, or toughness of SIFCON can be significantly greater compared to that of traditional steel-fiber reinforced concrete. The high fiber content contributes to the relatively expensive cost of SIFCON [1–5].
It has been established that incorporating steel fibers into concrete can increase the material's resistance to cracking. Due to their ability to increase the service life of refractory concrete, steel fibers have been increasingly used over the last thirty years to enhance its performance in a number of applications. Fibers are widely utilized to increase the ductility of concrete. It has been demonstrated that steel fibers improve the resistance of refractory concrete to spalling [6]. By delaying concrete spalling, it is understood that steel fibers might improve the fire effectiveness of SlFCON elements. Therefore, contributing indirectly to concrete confinement under compressive stress [7]. Consequently, it is recommended to undertake an experiment to examine SIFCON's performance in elevated temperatures.
A large number of accidental fires have been reported globally in recent years due to the increased application of new concrete trends in the structure of load-bearing elements for towering buildings made up of columns and beams [8]. These structures' fire safety designs have become essential. This is due to the fact that these components' fire resistance for a reasonable amount of time is the last line of defense in case all other attempts to extinguish the fire are unsuccessful [9, 10]. In addition, it is essential to design buildings with the lowest potential danger to both humans and property [11, 12]. The two environmental factors that have the biggest impact on the quality of concrete are the rate of burning and the highest temperature that can be reached. The most damaging causes of heating are the C-S-H phase dehydration, the pore pressure within the cement paste, and the thermal incompatibility of the aggregates and cement paste. [13, 14]. High-performance concrete and ultra-high-performance concrete have numerous benefits, nevertheless, these composites are practically brittle while having extremely high compression strength values. The enough fiber inclusion improves the deformation ability and tensile strength, leading to increased ductility [15, 16]. SIFCON that will be utilized in strengthening operations and military construction could be subjected to elevated temperatures due to causes including fires and explosives. Exposure to high temperatures represents one of the greatest influential physical degradation factors on the durability of cement-based materials [17].
Due to a growing vehicle industry and a decline in the quantity and capacity of landfill space, it is becoming increasingly difficult to dispose of waste tires. Currently, 75 to 80 percent of tire debris is buried in landfills. The majority of landfill operations do not allow the disposal of whole tires due to the size of the flames and their propensity to ascend to the surface with time. Investigations have revealed that used rubber tires contain materials that are harmful and do not disintegrate in the environment. Tires can be utilized as aggregates in concrete based on these issues. Aggregate and cement are the two primary materials needed in the construction of buildings using concrete. Despite the fact that 60% of it is considered illegally dumped. The ideal method for getting rid of old tires is to recycle the rubber by mixing it with concrete. The mechanical characteristics of recycled rubber concrete with various substitution forms and volume contents were studied. The primary objective of studies related to waste rubber has been the substitution of fine aggregate in concrete with shredded rubber. Different levels of crumb rubber replacement in concrete produced varying effects, and researchers concluded that 10% crumb rubber replacement is the best [18].
Olivares and Barluenga [19] examined the burning behavior of high-strength concrete containing waste tires. A little amount of waste rubber aggregate in the concrete mixture reduces the risk of sudden fracturing in high-strength concrete at higher temperatures because water vapor dissipates through the pathways left behind by the combustion of polymeric particles. Furthermore, raising the tire aggregate percentage decreased the temperature and depth of penetration in concrete, and the use of rubber particles in concrete up to 3 percent had little impact on the compressive strength despite lowering the stiffness. In their investigation, Marques et al. heated the hardened specimens to 400, 600, and 800 C while replacing 5, 10, and 15% of the normal sand in the concrete mixture with waste chopped aggregate. They discovered that the tensile strength, compressive strength, and elastic modulus all declined as the waste aggregate substitute level and temperature increased [20]. Guo et al. [21] evaluated the elastic modulus, compressive strength, stress-strain curve, and toughness at four distinct temperatures in order to evaluate the impact of high temperatures on the compressive strength of concrete containing steel fibers and chopped rubber. After being subjected to elevated temperatures, both tensile strength and compressive strength decreased, with the decrease being more pronounced at larger chopped rubber percentages [21]. Aslani and Klein [22] carried out research on fiber-reinforced self-compacting concrete SCC with lightweight aggregate and crumb rubber and observed that, under elevated temperatures, the tensile strength of concrete reinforced with steel fibers decreased less than that of concrete containing PP fibers. In addition, after being exposed to 600°C, the elastic modulus of the specimens decreased by an average of 50%. Bengar and Shahmansouri [23] studied the compressive behavior of rubberized concretes that were enclosed in steel tubes, where rubber replaced fine particles to varying degrees (0, 7.5, and 15%). After heat loading at 200, 400, 600, and 800 C. Thirty specimens underwent mechanical testing. Experimental research was done on the post-fire physico-mechanical characteristics, including compressive strength, failure mode, elastic moduli, stiffness, compressive stress-strain relationship, and peak strain. The experimental results show that a temperature rise of up to 400°C has no discernible impact on the compressive strength of rubberized steel tube-confined concrete STCC, but a temperature increase of up to 800°C causes a discernible drop in the compression of the specimens. Moreover, raising the exposure temperature and waste rubber substitution content causes an increase in the steel tube-confined rubberized concrete's peak strain.