Novel Mechanism of Sulfate Erosion Mitigation in Cement Mortar Using CF-Based Densifier: Microstructural and Durability Perspectives

Jianye Liu¹Peishan Huang¹Hehao Gan¹Xin Wang^2*Zhuo Liu²

• ¹Shanghai Transportation Construction General Contracting Co., Shanghai, China
• ²Kunming University of Science and Technology, Kunming, China

Cementitious materials are widely used in marine and alkaline environments, where sulfate erosion resistance significantly influences structural durability and safety. To address this challenge, this study systematically evaluated the effectiveness of CF-S2 densifier in enhancing sulfate erosion resistance of cement mortar. The performance of CF-based densifier mortars with varying dosages was assessed by compressive strength, mercury intrusion porosimetry (MIP), SO₄²⁻ concentration distribution, and dry-wet cyclic sulfate erosion tests. The results indicated that the CF-based densifier optimized the pore size distribution by reducing the proportion of harmful pores (≥100 nm), especially macropores (>1000 nm). Meanwhile, it increased the proportion of transition pores (10-100 nm) and improved pore tortuosity, effectively hindering aggressive ion penetration. After 60 wet-dry cycles, compared to ordinary Portland cement (OPC) mortar, the compressive strength and corrosion resistance coefficient of mortar containing 0.1% CF-S2 increased by 36.4% and 41.5%, respectively, along with significantly reduced surface erosion damage. Moreover, SO₄²⁻ concentration distribution tests showed consistently lower SO₄²⁻ concentrations at all measured depths in densifier mortar, confirming improved sulfate resistance. This study demonstrates that CF-based densifier significantly enhances the mechanical properties and sulfate erosion resistance of cement mortar, providing an effective strategy for improving durability of cement-based materials and offering broad prospects for engineering applications.Keywords：Cementitious materials; Sulfate attack; Dry-wet cycles; Sulfate ion distribution; Pore structureConcrete has become the most widely utilized construction material globally, owing to its abundant raw materials, mature preparation technologies, and versatile engineering applicability (Tan et al., 2022;Zheng et al., 2023;Zhao et al., 2024). However, ordinary concrete exhibits poor resistance to sulfate attack in aggressive environments such as oceans and saline soils, resulting in structural degradation and considerable durability loss (Neville, 2004;Pang et al., 2024). Given the widespread presence of sulfate-rich environments worldwide, sulfate attack significantly increases maintenance expenditures and severely compromises structural safety and reliability. Such deterioration often results in the premature failure of concrete structures, causing substantial economic