Performance Evolution of Recycled Aggregate Concrete under the Coupled Effect of Freeze-Thaw Cycles and Sulfate Attack  
[PERSON]  
1 School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049, China; [EMAIL_ADDRESS] (PJ. ); [EMAIL_ADDRESS] (J.-z. ); [EMAIL_ADDRESS] (D.Z.) [PERSON]  
2 Failure Mechanics & Engineering Dissert Prevention and Mitigation Key Laboratory of Sichuan Province, College of Architecture & Environment, Sichuan University, Chengdu 610065, China; [EMAIL_ADDRESS] 2  
[PERSON]  
1 School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049, China; [EMAIL_ADDRESS] (PJ. ); [EMAIL_ADDRESS] (J.-z. ); [EMAIL_ADDRESS] (D.Z.) [PERSON]  
1 School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049, China; [EMAIL_ADDRESS] (PJ. ); [EMAIL_ADDRESS] (D.Z.) [PERSON]  
3 School of Architecture and Civil Engineering, Chengdu University, Chengdu 610106, China; [EMAIL_ADDRESS] 34 School of Engineering, University of Liverpool, Liverpool L69 3 GQ, UK 4  
[PERSON]  
2 Failure Mechanics & Engineering Dissert Prevention and Mitigation Key Laboratory of Sichuan Province, College of Architecture & Environment, Sichuan University, Chengdu 610065, China; [EMAIL_ADDRESS] 2  
[PERSON]  
2 Failure Mechanics & Engineering Dissert Prevention and Mitigation Key Laboratory of Sichuan Province, College of Architecture & Environment, Sichuan University, Chengdu 610065, China; [EMAIL_ADDRESS] 2  
Footnote 2: email: {liu_jangfeng_dongwei  
that of the ordinary concrete. [PERSON] et al. [10] investigated the efficiency of the superplasticizer on the mechanical properties of RAC and confirmed the efficiency of polycarboxylic superplasticizer to enhance the mechanical properties of RAC to a satisfactory level. By improving the properties of mortar and interfacial transition zones (ITZs), the mechanical properties of RAC could be significantly improved. Nevertheless, inferior properties of RCA, such as high porosity, high water absorption, low density and low strength, still exist. [PERSON] et al. [11] found that the mechanical performance of RAC could be predicted by considering only water absorption capacity to quantify the \"quality\" of recycled coarse aggregate. [PERSON] et al. [12] studied the permeability of RAC, and they further indicated the significant reduction of RAC permeability by adding 10% silica fume to the concrete mixture. On the other hand, fluid ingress is a primary factor that influences the freeze-thaw damage in concrete and is still one of the most important durability problems for concrete [13]. When the degree of saturation of water exceeds 86-88%, the freeze-thaw damage is inevitable, with or without air entrainment, even by exposure to a few freeze-thaw cycles [14]. The high porosity of recycled coarse aggregate results in high water absorption and less resistance to chemical attacks in comparison to ordinary concrete. [PERSON] and [PERSON] [15] studied the effect of parent concrete quality on the properties of RAC and recorded an increase of chloride-ion penetration in the presence of recycled coarse aggregate compared to ordinary concrete. This phenomenon was also confirmed through the evaluation of the sulfate resistance of concrete with recycled coarse aggregate and natural aggregate [16]. Indeed, much research has been conducted on the durability of RAC under the freeze-thaw cycle or sulfate attack [17; 18; 19]. Comparatively, limited studies were carried out on the combined effects of chemical attacks (chloride corrosion, sulfate attack) and freeze-thaw damage [20; 21; 22; 23]. For instance, [PERSON] et al. [24] studied the damage development in concrete exposed to deicing salt and reported that ice formation was the main reason causing damage for mortar exposed to low concentration MgCl\({}_{2}\) solutions (<10% by weight), while the deterioration was most likely due to chemical attacks at higher concentrations (\(\geq\)10% by weight). The area of saline-alkali land in China ranks third in the world.