Recycling waste tires for the production of concrete materials with good toughness is a green and economical solution, but the severe deterioration of rubber under high temperatures limits its application in engineering practice. Therefore, to examine the impact of elevated temperature on the fracture characteristics of rubber concrete (RC), three-point bending fracture tests were conducted on RC with five rubber replacement rates and five treatment temperatures. The purpose was to correlate the fracture parameters of RC with the rubber replacement rate and the temperature. Then, by employing the digital image correlation (DIC) technology and microscopic testing methods, the crack evolution trend and the potential mechanism were analyzed in detail. The results indicate that rubber particles can effectively improve the toughness, deformation capacity, and fracture energy of concrete, but have a significant weakening effect on the load and fracture performance. When the treatment temperature is below 400 ℃, rubber particles mainly affect the initiation and propagation of cracks by alleviating the stress concentration phenomenon at the crack tip and improving the crack propagation path. Rubber particles may initiate cracks earlier, but significantly delay their propagation process. When the treatment temperature is above 400 ℃, rubber particles tend to exert a weakening effect on the fracture performance. As the temperature rises, the microstructure of rubber particles gradually changes from a relatively uniform state in close contact with the cement matrix to a fragmented state filled with pores separated from the matrix. This process will lead to severe deterioration of concrete performance. It is anticipated that the findings of this study will provide a theoretical basis for predicting the performance of RC in high-temperature environments.

Carbon fiber reinforced polymer (CFRP) has emerged as an effective material for strengthening reinforced concrete (RC) structures due to its high tensile strength, corrosion resistance, and ease of installation. However, in square or rectangular RC columns, stress concentrations at corners hinder the development of uniform confinement, thereby reducing strengthening efficiency. This study presents a comprehensive experimental and theoretical investigation into the performance of CFRP-confined RC square columns with varying anchor configurations. Six full-scale column specimens were tested under monotonic axial compression, each externally wrapped with one layer of CFRP sheet and installed with zero to four CFRP anchors. All columns were chamfered with a 30 mm radius to mitigate corner stress concentrations. The experimental results demonstrated that CFRP anchors significantly enhanced load-bearing capacity and ductility, improved lateral confinement, and modified the failure mechanisms. The specimen with three anchors exhibited optimal performance, with a 51.5 % increase in peak load (from 879.9 kN to 1333.2 kN) and a 29.9 % improvement in ductility index compared to the unconfined control. The failure mode transitioned from brittle global instability to ductile localized damage, accompanied by more uniform hoop strain distribution. However, excessive anchoring introduced stress interference and local cracking, leading to performance degradation. To characterize the mechanical response, a modified stress–strain model was developed, incorporating a reduction factor to account for confinement weakening caused by anchor installation. The model exhibited strong agreement with experimental data (R² > 87 %) in predicting both peak and ultimate stresses. This study provides valuable insights into the mechanical enhancement mechanisms of CFRP anchoring systems and offers a rational design basis for strengthening non-circular RC columns in structural rehabilitation.

This study introduces a novel approach that integrates Acoustic Emission monitoring with fractal analysis to assess and predict damage progression in FRP-strengthened reinforced concrete beams subjected to corrosion-induced deterioration. By combining AE signals with fractal measures, specifically the correlation dimension, the research provides an effective tool for tracking internal damage evolution and offering early-warning indicators for structural health. The developed damage model identifies three distinct stages of damage: initial damage, damage evolution, and sustained growth. The study reveals that corrosion accelerates both the accumulation and rate of damage, with AE ring counts significantly increasing in moderately to severely corroded beams, indicating heightened crack activity and reduced structural capacity. The correlation dimension shows a strong relationship with the degree of damage, with higher values corresponding to more disordered internal damage. The correlation dimension evolves from an initial increase to a decrease as damage progresses, marking the transition from early to advanced degradation. These findings highlight that corrosion not only accelerates damage but also lowers the detection threshold for significant structural damage.