Compression behavior of CFRP-confined recycled aggregate concrete under combined effects of sulfate corrosion and freeze-thaw cycles

This study investigates the performance of recycled aggregate concrete (RAC) confined with carbon fiber reinforced polymer (CFRP) under the combined effect of sulfate corrosion and freeze-thaw cycles (FTCs), two major factors contributing to the durability deterioration of buildings and bridges. A multiscale analysis was performed to understand the damage mechanisms of RAC under the sulfate corrosion and FTCs effect. Compressive tests were conducted to evaluate the compressive mechanical properties, mechanical behavior and failure modes of CFRP-reinforced RAC. CFRP can significantly improve compressive strength from one layer to three layers with an increase of about 34 %, confirming the effectiveness of CFRP reinforcement. The FTCs from 50 to 150 times reduced residual compressive bearing strength by 7.6 %, while sulfate erosion had little effect on it with only a 3.4 % increase from 5d to 25d. As the RCA substitution increased from 0 % to 50 % and then to 100 %, the compressive strength decreased by 8.7 % and 15.6 %, respectively. These results demonstrate its potential for use in structural applications while maintaining acceptable performance levels. Additionally, developed models were proposed to predict failure strength, strain, and stress-strain response by incorporating a damage index and the effects of CFRP reinforcement. The results highlight the effectiveness of CFRP reinforcement in improving the mechanical properties and durability of RAC under severe environmental conditions. Furthermore, the proposed models provide an accurate prediction of the mechanical behavior of pre-damaged RAC reinforced with CFRP.