This paper presents the results of an experimental study on the comparative response of polypropylene (PP) fiber-incorporated reinforced concrete (RC) beams under fire conditions. Five fullscale RC beam specimens, made with different batch mixtures comprising normal plain concrete (NPC) and fiber-reinforced concrete (FRC), were tested to assess their spalling performance and structural behavior under fire conditions. The main variables in the experiments were the amount and length of PP fibers. Deflections, temperatures, and spalling in the beams were monitored during fire exposure. FRC beams’ flexural failure occurs after 151 minutes at heating temperatures beyond 850°C, when deflections exceed span/20. When the concrete contains PP fibers (that is, FRC beams), the gamut of fire-induced spalling in RC beams gets reduced, increasing the fire resistance from 147 to 171 minutes (approximately 17%). Furthermore, test results show that adding 2 to 3 kg/m3 of PP fibers effectively releases the pore pressure through tensile cracking and reduces the amount of spalling in the FRC beams.

Structural lightweight-aggregate concrete (LWAC) has gained a broad range of applications in the construction industry owing to its reduced dead load and enhanced fire resistance. In this study, the potential of using lightweight expanded clay aggregates as a partial replacement for fine and coarse natural aggregates was experimentally and numerically examined. Testing was performed on cylindrical specimens made of normalweight and lightweight concrete incorporating microsilica as a partial replacement for cement to determine the associated stress-strain behavior. Subsequently, three-point bending testing was conducted on reinforced concrete beams to evaluate their structural behavior. Four levels of temperature were considered: 25°C (ambient temperature), and 250, 500, and 750°C (elevated temperatures). The finite element method through Abaqus software was deployed to numerically investigate the behavior at elevated temperatures through a comprehensive parametric study. The experimental and numerical results indicate that under high-temperature exposure, LWAC outperforms its normal counterpart in terms of strength, stiffness, and Young’s modulus. It is also noticeable that LWAC beams retained their load-bearing capacity better than normal weight aggregate concrete (NWAC) after reaching the peak load.

The possibility of incorporating scrap tire residue into concrete has already been consolidated in previous studies, but there is a knowledge gap about how concrete made with recycled tire materials behaves when exposed to high temperatures. This study aims to investigate the performance of precast concrete panels made with scrap tire residues when exposed to fire when using recycled steel fiber and recycled rubber aggregates separately. The experimental design consisted of fire resistance tests. Real-scale panels were exposed to the standard fire curve based on ISO 834, measuring the temperatures on the panel surfaces. The recycled steel fiber-reinforced concrete and those containing 5% recycled rubber aggregate presented similar behavior when compared to the conventional concrete on thermal insulation, integrity, and structural stability. The concrete made with 10% recycled rubber aggregate registered the occurrence of explosive spalling and worse thermal insulation and integrity.

Steel fiber-reinforced concrete (SFRC) can be an ideal substitute for conventional steel reinforcement in railway tunnel lining construction due to its high strength and good fire resistance. On the other hand, it is still not clear whether discontinuous steel fibers can pick up and transfer stray current and lead to similar corrosive attack as that occurs in conventional steel reinforcement. These were evaluated through voltammetry tests and electrochemical impedance spectroscopy (EIS) before and after simulated railway stray direct current (DC) and alternating current (AC) interferences. In addition to instrumental methods in electrochemistry, numerical modeling based on the boundary element method (BEM) modeling indicates that discrete steel fibers can pick up and transfer stray currents. This was validated by the electrochemical investigations conducted using both aqueous and solid (mortar) electrolytes. It can be concluded that steel fibers have high corrosion resistance to stray AC and DC interferences even with the presence of a small amount of NaCl in the electrolyte.

Sacrificial concrete is a cement-based material used for fire protection purposes. It is commonly used as a protective layer in nuclear reactor core containment structures in nuclear power plants. Its purpose is to act as a protection material only. Sacrificial concrete is particularly effective in protecting nuclear reactor core containment because it possesses high temperature stability and high melt capability that can reduce or help avoid the deterioration due to ultra-high temperature exposure from nuclear reactor core accidents or meltdowns. Sacrificial concrete is used in European pressurized reactors (EPRs), as an example, to contain molten core melts by melting a sacrificial concrete layer within the containment, which helps to cool the molten core and assists in avoiding a hot melt on the load-bearing containment structure. The study of performance of sacrificial concrete in ultra-high temperature exposures is in its early stages. To investigate the behavior and properties of sacrificial concrete at the ultra-high temperature of 5430°F (3000°C), numerical modeling simulating the same environment of a nuclear accident is established. Results indicate that the water-cementitious materials ratio (w/cm) and mineral admixtures have a significant impact on compressive strength, water loss, and water content of sacrificial concrete. Mixture proportions presented in this paper possess outstanding spalling resistance and melting behavior. Even at ultra-high temperatures, the sacrificial concrete possesses good melting behavior, and the melt depth of sacrificial concrete increases proportionally with time, which can effectively reduce the detriment of a nuclear accident.