Introduction to Steel Fiber-Reinforced Rubber Concrete and High-Temperature Performance
In recent years, the need for durable concrete materials capable of withstanding extreme temperatures has become increasingly critical due to rising incidents of engineering fires, industrial accidents, and the growing demand for fire-resistant construction materials. Among the innovative solutions being explored is Steel Fiber-Reinforced Rubber Concrete. This composite material integrates steel fibers with rubber particles, offering enhanced mechanical properties such as flexibility, impact resistance, and toughness. It also provides an environmentally friendly solution by recycling waste tires into construction materials.
Steel fibers are known to improve concrete's tensile strength, ductility, and crack resistance, while rubber particles offer deformability and energy absorption properties. When combined, these components work synergistically, potentially overcoming some of the inherent weaknesses of rubber concrete (RC), such as its lower strength and weak interface transition zone (ITZ) between rubber and cement. SFRRC shows promise in high-performance applications, including in structures exposed to elevated temperatures, where traditional concrete materials may fail.
This study, conducted by Jiongfeng Liang, Kaiwei Liu, Caisen Wang, Xuegang Wang, and Jicheng Liu and published in Scientific Reports (2025), investigates the mechanical properties of SFRRC after exposure to high temperatures ranging from 20°C to 800°C. The goal is to assess how the incorporation of steel fibers and rubber particles influences the material’s ability to maintain its structural integrity and strength under extreme thermal conditions.
The Challenge of High Temperatures on Concrete
Concrete is generally resilient at ambient temperatures, but it is highly vulnerable to temperature-induced damage. Exposure to high temperatures can result in a loss of mechanical strength, cracking, and volume expansion due to the thermal degradation of its components. In severe cases, concrete can experience spalling, a phenomenon where the material explosively disintegrates, leading to structural failure. In buildings, industrial facilities, or nuclear plants, such failures can be catastrophic.
As a result, concrete that can retain its strength and resist cracking when exposed to elevated temperatures is essential. Concrete with rubber particles has shown promising thermal insulating properties, as the rubber particles provide some degree of thermal resistance. However, this material often suffers from a decline in compressive strength due to increased porosity and weaker bonding at the interface transition zone.
Steel fibers, on the other hand, enhance crack resistance by reinforcing the concrete matrix, preventing the propagation of cracks under thermal stress. Therefore, the combination of rubber particles and steel fibers in SFRRC offers a promising solution to address the vulnerabilities of concrete in fire-exposed scenarios.
Research Methodology and Experimental Setup
The study involved a comprehensive series of tests on SFRRC specimens subjected to varied temperature conditions. The researchers selected two steel fiber contents (0.6% and 1.2%) and four rubber substitution ratios (0%, 5%, 10%, and 15%). The specimens were then exposed to temperatures of 20°C, 200°C, 400°C, 600°C, and 800°C.
After each exposure, the residual mechanical properties of the SFRRC samples were evaluated using a range of tests:
• Cube compressive strength (fcu): To measure the material’s capacity to withstand compression.
• Uniaxial compressive strength (fc): To assess the strength under axial compression.
• Splitting tensile strength (fsp,t): To evaluate the material's resistance to tensile stresses.
• Flexural strength (ffl.): To determine the ability of the concrete to resist bending forces.
These tests provided insights into how the material behaves under high temperatures and helped identify the optimal mix of steel fibers and rubber particles for enhanced high-temperature performance.
Key Findings of the Study
Steel Fibers and Rubber Particles Enhance High-Temperature Performance
The results of the study showed that the incorporation of steel fibers and rubber particles into concrete significantly improved its performance after exposure to high temperatures. Some key findings include:
• Cube compressive strength improved by 0.23% to 8.48% at temperatures between 20°C and 800°C, compared to normal concrete.
• Uniaxial compressive strength increased by 1.13% to 4.16% across the tested temperature range.
• Splitting tensile strength showed a remarkable increase of 22.92% to 44.23% under elevated temperatures, indicating the material’s improved resistance to tensile stress at high temperatures.
• Flexural strength improved by 3.03% to 19.81%, highlighting the material’s superior ability to resist bending forces at elevated temperatures.
The optimal mix for high-temperature performance was found to be 1.2% steel fibers and 5% rubber particles. This combination provided the best strength enhancement, with the splitting tensile strength showing the greatest improvement, making it an ideal composition for environments exposed to thermal stresses.
Temperature Resistance and Crack Control
The steel fibers played a crucial role in controlling cracking under thermal stress, preventing the cracks from propagating and enhancing the durability of the concrete. The rubber particles, on the other hand, contributed to the material’s energy absorption capacity, which helped mitigate the thermal shock effects during temperature fluctuations. The synergy between these two components ensured that the SFRRC retained its structural integrity and mechanical strength even under extreme heat.
The study also confirmed that the rubber content could be increased up to 10% without significantly affecting the material's performance at high temperatures, making SFRRC an excellent candidate for lightweight construction applications where fire resistance is a priority.
Predictive Models for High-Temperature Behavior of SFRRC
To further the application of SFRRC, the study proposed predictive models based on the experimental results. These models aim to estimate the residual mechanical properties of SFRRC after exposure to high temperatures, providing a theoretical framework for the material's use in high-temperature environments.
The models were validated by comparing them with experimental data and previous research. The validation confirmed that the models are both accurate and reliable, offering valuable tools for engineers and construction professionals.
Applications and Future Directions
With its enhanced fire resistance and mechanical strength, SFRRC shows significant promise for high-temperature applications. This includes nuclear power plants, industrial furnaces, high-rise buildings, and fireproof infrastructures, where traditional concrete would struggle to maintain its structural integrity under extreme heat.
In addition, SFRRC’s low carbon footprint, thanks to the reuse of waste rubber, aligns well with the growing emphasis on sustainability and environmental conservation in modern construction practices. As the construction industry increasingly seeks to adopt green materials, SFRRC presents a unique opportunity to reduce waste while improving material performance.
Further research is needed to refine the predictive models, optimize the mix designs, and expand the understanding of SFRRC’s long-term behavior in fire-prone environments. Additionally, standardization of SFRRC’s properties and testing methods will be essential to facilitate its widespread adoption.
Key Takeaways:
• SFRRC improves the mechanical properties of concrete after exposure to high temperatures, with significant enhancements in compressive, tensile, and flexural strengths.
• The combination of 1.2% steel fibers and 5% rubber particles produced the best results for maintaining strength and durability under high-temperature conditions.
• Steel fibers help prevent crack propagation, while rubber particles provide energy absorption and reduce the risk of explosive spalling.
• SFRRC showed improvements in splitting tensile strength by up to 44.23%, making it ideal for applications where crack resistance is critical.
• The study proposes predictive models that accurately estimate the residual mechanical properties of SFRRC after exposure to high temperatures, providing a foundation for its future use.
• The material holds great potential for use in fire-resistant and high-temperature environments, such as nuclear plants, industrial kilns, and high-rise buildings.
• The research highlights SFRRC’s potential in sustainable construction, with waste rubber being repurposed as a recycled material for fire-resistant concrete.
