This study aimed to investigate the mechanical performance of early-strength carbon fiber-reinforced concrete (ECFRC) by incorporating original carbon fiber (OCF), recycled carbon fiber (RCF), and sizing-removed carbon fiber (SCF). Compressive, flexural, and splitting tensile strength were tested under three fiber-to-cement weight ratios (5‰, 10‰, and 15‰). The RCF was produced from waste bicycle parts made of carbon fiber-reinforced polymer (CFRP) through microwave-assisted pyrolysis (MAP). The sizing-removed fiber was obtained through a heat-treatment method applied to the OCF. The results of scanning electron microscopy (SEM) analysis with energy dispersive X-ray spectrometry (EDS) indicated the successful removal of sizing and impurities from the surface of the RCF and SCF. The mechanical test results showed that ECFRC with a 10‰ fiber-to-cement weight ratio of carbon fiber had the greatest improvement in its mechanical strengths. Moreover, the ECFRC with 10‰ RCF exhibited higher compressive, flexural, and splitting tensile strength than that of benchmark specimen by 14.2%, 56.5%, and 22.5%, respectively. The ECFRC specimens with a 10‰ fiber-to-cement weight ratio were used to analyze their impact resistance under various impact energies in the impact test. At 50 joules of impact energy, the impact number of the ECFRC with SCF was over 23 times that of the benchmark specimen (early-strength concrete without fiber) and was also greater than that of ECFRC with OCF and RCF.

A parabolic stress–strain constitutive model for inorganic thermal-insulating material confined by carbon fiber-reinforced polymer (CFRP) exposed to a surrounding elevated temperature was proposed in this paper. The thermal-insulating material used in this study was composed of high-early-strength cement (HESC) and perlite powder. The compression strengths of four kinds of perlite powder composition ratios of thermal-insulating materials cylindrical specimens which were confined by one, two, and three-layer CFRP composite materials were acquired. The experimental results showed that the compression strength was enhanced as the amount of perlite substitute decreased or as the number of CFRP wrapping layers increased. The Mohr–Columb failure criteria were adopted to predict the maximum compressive strength of CFRP-confined inorganic thermal-insulating material. The strain at the maximum compressive strength was found from the experimental results, and the corresponding axial strain at the maximum compressive strength in the constitutive model was determined from the regression analysis. Furthermore, the compressive strengths of the four different perlite composites of thermal-insulating materials were obtained when heating the specimens from ambient temperature to 300 °C. The compressive strength decreased with an increase in temperature, and a thermal softening parameter model was proposed; the thermal softening parameter was determined from the experimental maximum compressive strength at an elevated temperature. Combining the above two models, the constitutive model of HESC with perlite powder additive as a thermal-insulating material confined by CFRP under elevated temperature was proposed.

Although extensive studies have examined the tribocorrosion behavior of stainless steels, the performance of medium-entropy austenitic super stainless steels (MEASS) under severe combined corrosion and mechanical wear conditions has not been fully established. This study systematically compares the tribocorrosion behavior of a newly developed MEASS with conventional S31254 super austenitic stainless steel (SASS) in a 1 M H₂SO₄ solution, aiming to explore innovative material designs for enhanced performance under these demanding conditions. Electrochemical tests were conducted under both open-circuit potential (OCP) and cathodic potential, with and without sliding wear, to assess the corrosion, wear, and synergistic effects influencing the tribocorrosion performance. Worn surface morphologies and hardness were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and hardness measurements, respectively. The experimental results revealed that MEASS exhibits a superior repassivation capability compared to S31254, with a 34.3% lower total material loss after 24 h of tribocorrosion test, primarily attributed to enhanced strain hardening and improved wear resistance. These findings emphasize the strong potential of MEASS for use in corrosive environments, particularly in chemical processing industries, where high resistance to wear and corrosion is critically required.