An Extended Special Issue on Advances in High-Performance Fiber-Reinforced Concrete

Adding fiber to cement concrete can improve the shortcomings of concrete, such as low tensile properties and low ductility, and improve its resistance to permeability and impact. With the advancement of science and technology, cement-based structural engineering materials with clear performance indicators, namely high-performance fiber-reinforced concrete (HPFRC), have been developed. The role of fibers in HPFRC depends on the properties of the fibers themselves, and on the mixing state of the fibers in the matrix. There are many types of fibers used in HPFRC. According to the material, it can be divided into metal fibers (such as carbon steel, stainless steel, metal glass, etc.), inorganic fibers (such as natural mineral, artificial mineral, carbon, etc.), and organic fibers (such as synthetic, plant, etc.). According to the elastic modulus, it can be divided into high elastic modulus fibers (such as steel, glass, carbon, and basalt) and low elastic modulus fibers (such as organic fibers). The stiffness of high elastic modulus fibers is greater than that of concrete. Once micro-cracks occur in the matrix, the fibers begin to bear force, which can share the stress on the concrete and increase the strength of the material. The stiffness of low elastic modulus fibers is less than that of concrete. They generally bear force only after the concrete cracks, thus are mainly used to improve the ductility of the material.

This Extended Special Issue aimed to collect and showcase all breakthrough research into HPFRC, including innovative concepts to improve its mechanical properties, the development of new fiber technologies to improve its performance, its engineering applications, reductions of the negative impact of fibers on certain concrete properties, the influence of fiber mixing on its performance, theoretical research on the mechanisms of fiber mixing, the role of inorganic fibers and organic fibers, its mix design, bonding performance, thermal performance and fire resistance, and the durability of HPFRC wait, etc.

A total of seven papers in various fields of HPFRC research are presented in this Extended Special Issue. Jiang et al. [1] investigated the structural response of reactive powder concrete-filled steel tube (RPC-FST) columns under blast loading. For the numerical simulation of RPC, the modified Holmquist–Johnson–Cook (HJC) model and the modified Karagozian and Case (K&C) model were used. In addition, the dynamic response of an RPC-FST column under an explosion load was analyzed, based on the arbitrary Lagrange–Euler (ALE) method. Their experimental results verified the feasibility of the proposed model. The analysis results also showed that the modified HJC model and the modified K&C model can be used to simulate the dynamic response of RPC-FST columns under explosion loads. Geng et al. [2] applied self-compacting steel fiber reinforced concrete (SFRC) to tetrahedron-like pervious frames for river revetment. An experimental study was conducted on the workability and mechanical properties of the SFRC with a volume fraction of steel fiber changed from 0.4% to 1.2%, and the reasonable volume fraction for making pervious frames was determined to be 0.8%. Ding et al. [3] reported the flexural behavior of high-ductility fiber-reinforced concrete (HDC). A four-point bending test was conducted on 40 mm × 40 mm × 160 mm specimens to analyze the flexural strength, deformation, and toughness of HDC. Their experimental results showed that the ultimate flexural strength of HDC with 2% polyvinyl alcohol fiber added was approximately 15.32 MPa, an increase of up to 221%. In addition, its deformation and flexural toughness ratios were 23 times and 1.43 times higher than those of the fiber-free specimens, respectively. Hung et al. [4] investigated the effects of added waste polyethylene and ground granulated blast furnace slag (GGBFS) on the engineering properties of cement mortar. Under the condition of a fixed water-binder ratio of 0.5, different amounts of PE (sand volume ratio of 0%, 1%, 2%, 3%, and 4%) and GGBFS (0%, 10%, and 20% substituted cement) were used to prepare specimens. The results showed that when the amount of waste PE was within 2% and the replacement of cement by GGBFS was 10%, the goal of waste recycling was most effectively achieved while maintaining the mechanical properties of the mortar. Ning et al. [5] explored the effects of different fibers on the spalling resistance and mechanical properties of self-compacting concrete (SCC) after high temperatures. Experimental variables included fiber type (steel fibers (SF) and polypropylene fibers (PF)), content (two PF contents, three SF contents, and one hybrid fiber), and target temperature (200 °C to 1000 °C). The obtained results indicated that PF can effectively prevent explosive spalling in SCC. Furthermore, a sharp decrease in compressive strength was observed when the target temperature exceeded 400 °C. This result confirmed that incorporating fibers is an effective method to improve the resistance to explosion spalling and residual mechanical properties during a fire. Xie et al. [6] analyzed the impact of using basalt and bamboo fibers as modifiers on the properties of asphalt mastic. The effects of these two fibers on rutting resistance, fatigue resistance, elastic recovery, and low-temperature cracking performance were tested using frequency scanning, linear amplitude scanning, multiple stress creep and recovery, elastic recovery, and bending beam rheometer experiments. Their results showed that adding fibers to asphalt mastics can effectively increase their stiffness. In addition, the incorporation of fibers significantly enhanced the high-temperature rutting resistance of asphalt mastics. However, adding fiber did not show any significant benefit in terms of fatigue resistance. It is worth noting that adding basalt fiber to asphalt mastics did not improve its resistance to low-temperature cracking. Overall, bamboo fiber performed better than basalt fiber in improving the properties of modified asphalt mastics. Tang et al. [7] proposed the axial stress–strain behavior of steel fiber-reinforced steel slag micro-powder ultra-high-performance concrete (UHPC). Nine groups of specimens with coarse aggregate and steel fiber content were prepared and subjected to axial compression and elastic modulus tests. Their test results showed that, compared to non-steel fiber specimens, the peak strains of the experimental groups incorporating 1%, 1.5%, and 2% steel fibers increased by approximately 20.3%, 25.3%, and 26.2%, respectively. In addition, based on the stress–strain curve obtained from the experiment and through curve fitting, the constitutive equation suitable for steel fiber-reinforced steel slag powder UHPC was further derived.

Although submissions for this Special Issue have closed, a Second Edition of this Special Issue is open. More in-depth research in the field of HPFRC continues to address the challenges we face today, such as reducing the negative impact of fiber on certain concrete properties, the impact of fiber mixing on HPFRC performance, theoretical research on the mechanism of fiber mixing, and the development direction of fiber concrete technology.