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As a result of the advantages of the steel fiber reinforced concrete pavement structure, which includes high strength, high stiffness, and high stability, a large number of steel fiber concrete pavements will be used for highway construction in China. As a result, numerous cracks develop, which significantly reduces the life of the road; therefore, the study of the jointing problem is vital. As concrete research on the influence of the load transfer capacity and service life of prefabricated steel fiber reinforced concrete joints on the structural design and use function of the whole and pavement panels, the paper proposes two joint forms, tongue-and-groove and overlap. Using experiments and software, the stress and reflection of prefabricated road panels of the two joint forms are analyzed for different axial loads. The analysis reveals that the maximum tensile stress, shear stress, and deflection of the precast panels of both joint forms increase linearly as the axle load of the vehicle increases, while the service life decreases relatively. The load transfer capacity is independent of the axle load magnitude, and the load transfer capacity difference between the two types of joints is minimal and excellent. [ABSTRACT FROM AUTHOR]

Coal gangue is a byproduct of coal mining and processing, and according to incomplete statistics, China has amassed a substantial coal gangue stockpile exceeding 2600 large mountains, which poses a serious threat to the ecological environment. Utilizing gangue as a coarse aggregate to produce gangue concrete (GC) presents a promising avenue for addressing the disposal of coal gangue; however, gangue concrete presents several challenges that need to be tackled, such as low strength and poor resistance to repeated loads. In this study, polypropylene fibers (PPFs) were incorporated into gangue concrete to enhance its utilization rate. Uniaxial compressive and repeated loading experiments were then conducted to investigate the uniaxial strength and fatigue properties of polypropylene fiber-reinforced gangue concrete (PGC) with varying gangue substitution rates (20%, 40%, and 60%) and different polypropylene fiber admixtures (0, 0.1%, 0.2%, and 0.3%). The findings indicate that incorporating gangue at a substitution rate of 40% could notably enhance the uniaxial compressive strength of PGC, resulting in a maximum increase of 19.4%. In the repeated loading experiments, the ductility of PGC was enhanced with the incorporation of PPFs, resulting in a reduction of 33.76% in the damage factor and 19.42% in residual strain for PGC-40-0.2 compared to PGC-40-0. A PPF content of 0.2% was found to be optimal for enhancing the fatigue performance of PGC. Scanning electron microscope (SEM) testing proved the improvement effect of polypropylene fiber on gangue concrete from a microscopic perspective. This study provides crucial experimental data and a theoretical foundation for the utilization of gangue concrete in complex stress environments. [ABSTRACT FROM AUTHOR]

ABSTRACT Fatigue performance of reinforced concrete (RC) components strengthened with fibre reinforced polymer (FRP) is largely improved. However, temperature changes of service environment have a great effect on the fatigue behaviour of RC components strengthened with FRP. Concerning about temperature variations in subtropical areas such as South China, this paper analyses the fatigue behaviour of RC beams strengthened with carbon fibre laminate (CFL) from experimental studies and theoretical analysis under four different temperatures (5 °C, 20 °C, 50 °C, 80 °C) and five different stress levels (0.60, 0.66, 0.72, 0.78, 0.84). The paper discusses temperature fatigue behaviour of RC beams strengthened with CFL under cyclic bending loads in different service environments, and proposes a calculation formula of fatigue lives of RC beams strengthened with CFL under environmental temperatures and external forces coupling. Experimental results show that the formula not only effectively predicts the fatigue lives of the RC beams strengthened with CFL under environmental temperatures and bending loads coupling but also estimates the fatigue limits. [ABSTRACT FROM AUTHOR]

[Display omitted] • Investigated the effect of high geothermal environments on the stress–strain relationship of steel fiber concrete. • Developed a uniaxial compression principal structure model considering heat damage temperature, fiber admixture and age. • Analyzed the effect of high geothermal environment on concrete hydration behavior using the P-K hydration kinetic model. The unique challenges presented by high geothermal environments in tunnel construction are becoming increasingly evident, particularly in the context of the high geothermal conditions in western China. In this paper, the uniaxial compressive properties, and stress–strain relations of steel fiber-reinforced concrete (SFRC) in high geothermal environment are studied. The effects of the volume fraction of steel fiber (0.5%/1.0%/1.5%/2.0%) and the heat damage temperature (40 °C/60 °C) on the peak stress, peak strain, and the stress–strain curve of SFRC under uniaxial compression are analyzed. The results show that the fracture and spalling of concrete around the main crack increase due to the heat damage after uniaxial compression test. Compared to 20 °C, the peak stress, bending strength, and limit flexural toughness of SFRC significantly decrease (45.9%, 29.5%, and 72.1%, respectively) after 60 days of exposure to a high geothermal environment of 60 °C. Moreover, while the addition of steel fiber can enhance the peak strain and limit flexural toughness of concrete, the decline in peak stress and bending strength of SFRC becomes more pronounced as the duration of heat damage increases. Based on the P-K hydration kinetics model, the ettringite content in cement without an accelerator is determined to decrease by 66.35% after 28 days of hydration at 60 °C, indicating in the change of the concrete's material properties. [ABSTRACT FROM AUTHOR]

The prestressed concrete containment vessels (PCCVs) will be exposed to the temperature action followed by the internal pressure increasing after a loss of coolant accident (LOCA) with safety system failure. The damage evolution of the PCCV under the effect of thermal-pressure coupling deserves in-depth study. Moreover, different containment external temperatures are seldom considered in previous studies whereas they may further pose a great challenge for the design and safety of containments. Just as important, an attempt is first made in this paper to involve steel fiber in the construction of the containment to observe the performance of the containment with steel fiber strengthening under the effect of thermal-pressure coupling. Therefore, the influence of the possible outside temperature (i.e. −30 °C, −15 °C, 0 °C, 15 °C, and 30 °C) determined from the 5 existing or planned nuclear power plant sites in China on the distribution of temperature field of containment is researched firstly. Then, the damage indices corresponding to the containment are defined to represent the actual damage performance and failure mechanism of the structure. Finally, the comparative damage performance and failure mechanism between conventional and steel fiber reinforced concrete (SFRC) containments taking into account the effect of coupling temperature and internal pressure is detailedly discussed. The results show that the SFRC is more expeditious in restraining radial and vertical displacement of containment under lower external temperatures for subsequent internal pressure. Under the ultimate internal pressure, the SFRC containment has a reduction rate of 5.37% for radial displacement and 35.52% for vertical displacement at an external temperature of −30 °C, while 2.23% and 15.33% at an external temperature of 30 °C, respectively. Furthermore, SFRC containment has better performance under the effect of coupling of temperature and internal pressure compared to conventional containment. For example, at an internal pressure of 1.2 MPa, the damage reduction rate for concrete is 94.18% at an external temperature of −30 °C and 81.37% at 30 °C; for the steel liner, the damage reduction rate is 50.22% at an external temperature of −30 °C and 87.83% at 30 °C. For the containment prestressing tendons, the damage reduction rate is around 60% under ultimate internal pressure. The study can provide important guidance for siting and design of nuclear containments and alternative retrofitting measures for nuclear containments. • The distribution of the containment temperature field under the LOCA is obtained. • New damage assessment parameters for containment are proposed. • Different external temperatures that affect the containment's performance is studied. • The reinforcement effect of steel fibers on the performance of the containment is evaluated. [ABSTRACT FROM AUTHOR]

A soil reinforcement system using the combination of glass-fiber-reinforced polymer (GFRP) pipe and pressure grouting has been developed by a Korean company. The system is being adopted as slope stabilization measures in Hong Kong. Individual GFRP pipes were designed and installed as soil nails with the exception that two-stage pressure grouting was applied instead of gravity grouting. A full-scale field evaluation on constructability and in situ performance of the system was performed in Hong Kong. The performance of the constructed nails was evaluated by pullout tests. The construction procedure, site adaptations of the Korean product made in Hong Kong, field test procedure, and performance of the constructed soil nails are reported in this paper. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to investigate the composite effect of steel fiber and steel rebar on the mechanical behavior of full-scale steel fiber reinforced concrete (SFRC) precast tunnel segments fabricated for a subway tunnel in China. A new biaxial loading method was adopted to simulate the loading state of the tunnel segment. The experiment included an initial SFRC tunnel segment proposed for the project, and two other SFRC tunnel segments were employed for comparison. By comparing the test results, the static characteristics of the three segments, including the internal strain, deflection, neutral axis position and crack patterns were determined. The experimental results indicate that the combined used of steel fiber and steel rebar shows an enhanced effect by delaying the initial impact of cracking and increasing the limit of proportionality of the segments. Longitudinal rebar in the tensile region were more helpful in decreasing tension strain and deflection in the mid-span section than the steel fibers. However, steel fibers performed better in improving the cracking load, cracking resistance and toughness. Furthermore, the initial SFRC tunnel segment proposed for the project exhibited a significant reduction in crack width and satisfied the design criteria for load carrying ability and crack width. The combination of steel fiber and steel rebar indicates an optimal choice of reinforcement for a tunnel segment. [ABSTRACT FROM AUTHOR]

In this study, to reduce the consumption of natural sand and improve the utilization rate of desert sand in western China, while preparing 14 groups of samples, desert sand is used to replace natural sand by the ratio of 20%, 40%, and 60%, and steel fiber is mixed with volume fraction 0.5%, 1.0%, 1.5%, and 2.0%. The mechanical properties of the specimens, including compressive strength, splitting tensile strength, and axial compressive strength were tested. Besides, the microstructures of the samples were analyzed by SEM, XRD, and acoustic emission detection technologies to identify the damage process. The results show that the desert sand can refine the microstructure and fill the pores, and it has good comprehensive properties at a 40% substitution rate. The compression properties of specimens are not apparently improved, but the tensile strength and deformation properties are significantly improved. The steel fiber with 1.5 vol% content behaves better, and the 28d compressive strength of the optimized group reaches 58.7 MPa. As a result, the polynomial fitting degree of total AE hits and stress level receives a more incredible goodness (R2) value than 0.96. The strength characteristics of steel fiber-desert sand concrete (SFDSC) can meet the demands of C40 concrete, and this research can provide a reference for engineers using desert sand in their designs. [ABSTRACT FROM AUTHOR]

Research on three-dimensional, randomly distributed BFRC in China is analyzed and summarized in relative depth in this study. The results indicate that the effect of the fiber component and alkali corrosion temperature on the alkali resistance of BF is significant; the BF has little effect on the compressive strength of the concrete; the tensile and flexural strengths of the composites significantly increase compared with plain concrete, and the fiber content has a significant effect on the strength. In light of some problems in the current research, six possible research topics are suggested: (1) investigating the alkali resistance of the BF under dynamic temperatures, lower alkali concentrations, and longer alkali corrosion times; (2) improving the alkali resistance of the BF by increasing its hydrophobicity; (3) determining the optimal fiber distribution orientation of the BF with various characteristic parameters; (4) establishing the calculation formulas for the critical content and critical aspect ratio of various types of BF; (5) determining the optimal mixture ratio of two or more fibers in the FRC while studying the complementary mechanisms between each other; and (6) improving the dispersion of the BF and the BF/matrix interfacial properties. [ABSTRACT FROM AUTHOR]