Rubber concrete (RC) is a new type of concrete that is currently receiving a lot of attention, solving serious pollution problems by grinding waste tires into granules and adding them to concrete. However, rubber concrete has deficiencies in mechanics and durability, and has been reinforced by adding fibers in many studies. In this study, the mechanical and durability properties of rubber concrete with added polypropylene and basalt fibers (PBRC) were investigated in a series of experiments including apparent morphology, mass, static compressive and tensile tests, ultrasonic non-destructive testing, and scanning electron microscope (SEM) tests under coupled environments of sulfate attack and freeze–thaw. The results showed that the mass loss rate of RC and PBRC gradually increased with the number of freeze–thaw cycles, with more pits and cement paste peeling from the specimen surface. Moreover, the compressive and splitting tensile strengths of RC and PBRC groups exhibited distinct trends, with the former group showing a lower residual strength relative to the latter. The residual compressive strength of the RC group was only 69.4% after 160 freeze–thaw cycles in 5% MgSO₄ solution. However, it is worth noting that the addition of too many fibers also had a negative effect on the strength of the rubber concrete. Additionally, the scanning electron microscopy (SEM) results indicated that the fibers restricted the formation of microcracks in the microstructure and curtailed the brittleness of the concrete. This study can provide a valuable reference for the application of environmentally friendly material fibers in recycled aggregate concrete.

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.

With the continuous spread of COVID-19 (coronavirus disease 2019), a large number of medical protective suits (PS) have been used and discarded, causing great damage to the ecological environment. The main component of PS is polypropylene plastic, which will enter the oceans, rivers, and animals with groundwater and will not decompose for hundreds of years. Therefore, this global health crisis not only affects the health and economy of the world’s population now but will also continue to disrupt our daily lives after the pandemic ends. The main objective of this study is to explore an effective method to reduce the biological and environmental hazards of medical waste by combining PS with concrete. Due to the excessive size of the PS, protective suit fibers (PSF) were obtained from PS by cutting. To investigate the possibility of using PS in concrete, a series of experiments were conducted, including a physical parameter test, compression test, split tensile test, ultrasonic pulse velocity test, scanning electron microscope (SEM), and finite element simulation. The results indicated that the introduction of PSF significantly enhanced the mechanical properties of concrete, and the maximum compressive strength and splitting tensile strength increased by 7.3% and 43.6%, respectively. The ultrasonic pulse velocity and density of concrete containing PSF decreased compared with the control group. The images of SEM show that PSF binds tightly to the cement matrix and hinders the propagation of micro-cracks. The introduction of PS into the concrete material leads to the improvement of the mechanical properties of concrete and the improvement of the overall quality of the concrete, which is of great significance for reducing the damage of medical waste to the environment. The originality of this work is that polypropylene fibers acquired from PS were put into concrete for the first time for performance testing.