Mechanical Performance and Microstructure Evolution of High-Ferrite Portland Cement Concrete Under the Coupled Abrasion and Freeze–Thaw Cycling Conditions

This study investigates the performance and microstructure evolution of high-ferrite Portland cement (HFC) concrete under the coupled action of abrasion and freeze-thaw cycles (CAA-FTC). The 3D surface morphology of deteriorated concrete was studied; abrasion depth and volume loss evolution data were collected, while analyzing the abrasion depth fractal dimension. The characteristics of hydration products were determined using mercury intrusion porosimetry and ²⁹Si nuclear magnetic resonance method. The ITZ's micromechanical properties and thickness were investigated via nanoindentation and SEM-EDS. The results show that under the CAA-FTC conditions, concrete deterioration is significantly exacerbated, leading to increased abrasion depth and volume loss compared to single-factor abrasion. A significant inverse relationship between the abrasion depth fractal dimension and abrasion resistance was revealed. Under CAA-FTC conditions, CG1 and CD1 exhibit increased total porosity with enlarged large pore proportions and reduced medium pores, whereas HFC1 outperforms HFC2-based concrete, showing 8.2-26.4% higher abrasion resistance and 6.5-12.0% greater nanoindentation elastic modulus in the ITZ. Regarding the deterioration factors' influence weight, abrasion time exhibits a deterioration weight 4.8 times to 10.0 times greater than freeze-thaw cycling, making the former a dominant factor and the latter a secondary contributor. Mechanistically, freeze-thaw cycles reduce the average molecular chain length of C-S-H gel, increase harmful pores and total porosity, and degrade the ITZ's microstructure, while abrasion causes surface-to-core physical damage and freeze-thaw cycling induces core-to-surface expansive damage. This interaction results in surface scaling, mortar spalling, and structural loosening, significantly reducing physical and mechanical properties of the concrete under study.