在我国地下水和盐碱地等自然环境中普遍含有硫酸盐成分。当硫酸盐渗透进入混凝土材料，会导致混凝土结构产生劣化和使用寿命的缩短。在地铁建设运行中，混凝土也同样面临这样的挑战。此外，地铁交通供电系统采用直流供电方式且地铁轨道与大地之间并非完全绝缘。伴随运营时间的增加，部分电流会通过轨枕和轨道组成的混凝土道床结构进行传导。与此同时，地下水位的波动等多重因素相互作用，进一步加剧了混凝土结构的侵蚀，从而对地铁线路的安全性和稳定性构成了潜在威胁。

本文以西安某地铁工程为研究背景，探究不同浓度硫酸盐作用、水溶液环境硫酸盐与杂散电流耦合作用、土壤环境硫酸盐与杂散电流耦合作用及硫酸盐与干湿循环耦合作用下普通混凝土和粉煤灰-矿粉双掺混凝土受硫酸盐侵蚀的影响机理。

试验分析了四种不同外界环境中两种混凝土试件的宏观力学性能-表观形态、质量、抗压强度和劈裂抗拉强度随侵蚀龄期变化的规律并应用SEM试验对混凝土侵蚀产物进行定性和定量分析。基于熵权法建立全面反映混凝土力学性能的综合评价指标，并采用算法优化后的XGBoost模型进行预测。主要研究内容及结果如下：

（1）硫酸盐单独作用下混凝土受硫酸盐侵蚀较慢。硫酸盐与杂散电流耦合作用下混凝土受侵蚀程度明显加速。180d硫酸盐单独作用下两种混凝土抗压强度均高于初始强度，而在5%硫酸钠溶液与20V直流电耦合作用下普通混凝土、粉煤灰-矿粉双掺混凝土强度分别下降19.61%、6.16%。同时，在混凝土外观、质量和劈裂抗拉强度上也得到了体现。

（2）硫酸盐单独作用、硫酸盐与杂散电流耦合与硫酸盐与干湿循环耦合作用下，混凝土受硫酸盐侵蚀规律相似。按侵蚀破坏程度从高到低依次为：水溶液环境硫酸盐与杂散电流耦合＞土壤环境硫酸盐与杂散电流耦合＞硫酸盐与干湿循环耦合＞硫酸盐单独作用。

（3）混凝土受硫酸盐作用的腐蚀产物主要为钙矾石和石膏。掺入粉煤灰、矿粉使得混凝土结构更为致密，减缓了混凝土内部石膏的生成速率，提高了混凝土结构的稳定性。5%浓度硫酸盐与40V直流电耦合作用下，180d时粉煤灰-矿粉双掺混凝土比普通混凝土抗压强度高16.23%。

（4）在试验基础上，通过熵权法构建综合评价指标。同时，对XGBoost机器学习模型进行超参数优化。DBO-XGBoost为最佳预测模型，决定系数为0.982，能够较好的预测混凝土试件的力学性能。硫酸盐与杂散电流耦合作用下粉煤灰-矿粉双掺混凝土是普通混凝土寿命的1.33~2.17倍。

Sulfate is widely present in natural environments such as groundwater and saline-alkali soils in China. When sulfate penetrates concrete structures, it induces material deterioration and reduces service life. These challenges are particularly prominent in subway construction and operation. Furthermore, the DC power supply system of subway trains and incomplete insulation between tracks and ground result in stray current leakage through concrete ballast beds composed of sleepers and rails over prolonged operation. Concurrently, fluctuating groundwater levels and multi-factor interactions exacerbate concrete erosion, posing significant risks to the safety and durability of subway infrastructure.

Using the Xi'an subway project as a case study, this study investigated the degradation mechanisms of sulfate attack on ordinary concrete and fly ash-slag composite concrete under varying sulfate concentrations, coupled sulfate-stray current interactions in aqueous and soil environments, and combined sulfate-dry-wet cycles.

Macroscopic mechanical properties of both concrete types were analyzed through compressive strength, splitting tensile strength, mass variation, and surface morphology evolution. Erosion products were characterized via scanning electron microscopy (SEM). A comprehensive evaluation index integrating mechanical properties was established using the entropy weight method, with predictive modeling conducted through an optimized XGBoost algorithm. Key findings include:

(1) Concrete was slowly eroded by sulfate under sulfate action alone. Under the coupled effect of sulfate and stray current, the erosion rate was significantly accelerated. After 180 days of sulfate exposure, the compressive strength of both concrete types exceeded their initial values. However, under the coupled action of 5% sodium sulfate solution and 20 V direct current, the strength of ordinary concrete and fly ash-slag composite concrete decreased by 19.61% and 6.16%, respectively. Additionally, changes in appearance, mass loss, and splitting tensile strength were observed.

(2) Concrete subjected to sulfate attack exhibits similar degradation patterns under sulfate acting alone, under the coupling of sulfate and stray current, and under the coupling of sulfate and wet-dry cycles. Ranked by the degree of deterioration from highest to lowest, the conditions are as follows: Sulfate with stray current in aqueous solution environment > Sulfate with stray current in soil environment > Sulfate with wet-dry cycles coupling > Sulfate acting alone.

(3) Ettringite and gypsum were identified as the primary corrosion products. The incorporation of fly ash and slag produced a denser concrete microstructure, which delayed gypsum formation and enhanced structural stability. Under 5% sulfate and 40 V DC coupling, fly ash-slag composite concrete exhibited a 16.23% higher compressive strength than ordinary concrete at 180 days.

(4) An entropy weight method was employed to establish a comprehensive evaluation index. The hyperparameters of the XGBoost model were optimized, with the DBO-XGBoost variant achieving the best predictive performance (determination coefficient = 0.982). Under sulfate-stray current coupling, the service life of fly ash-slag composite concrete reached 1.33~2.17 times that of ordinary concrete.

[1]交通运输部. 2025年1月城市轨道交通运营数据速报[R]. 2025.

[2]Tang S W, Yao Y, Andrade C, et al. Recent durability studies on concrete structure[J]. Cement and Concrete Research, 2015, 78: 143-154.

[3]Hossain M M, Karim M R, Hasan M, et al. Durability of mortar and concrete made up of pozzolans as a partial replacement of cement: A review[J]. Construction and Building Materials, 2016, 116: 128-140.

[4]Wang J, Gangarao H, Liang R F, et al. Durability and prediction models of fiber-reinforced polymer composites under various environmental conditions: A critical review[J]. Journal of Reinforced Plastics and Composites, 2016, 35(3): 179-211.

[5]Li C, Wu M, Chen Q, et al. Chemical and mineralogical alterations of concrete subjected to chemical attacks in complex underground tunnel environments during 20–36 years[J]. Cement and Concrete Composites, 2018, 86: 139-159.

[6]李华, 孙伟, 左晓宝. 矿物掺合料改善水泥基材料抗硫酸盐侵蚀性能的微观分析[J].硅酸盐学报, 2012, 40(08): 1119-1126.

[7]贺传卿, 李永贵, 王怀义, 等. 硫酸盐对水泥混凝土的侵蚀及其防治措施[J]. 混凝土, 2003(3): 56-57.

[8]GB/T 1402-2010, 轨道交通牵引供电系统电压[S]. 北京: 中国标准出版社, 2011.

[9]Aydin Zaboli, Behrooz Vahidi, Sasan Yousefi. Evaluation and control of Stray Current in DC-Electrified Railway Systems[J]. IEEE Transaction on Vehicular Technology. 2017, 66(2), 974-980.

[10]Thomas J. Barlo, Alan D. Zdunek. Stray Current Corrosion in Electrified Rail Systems-Final Report [R]. Northwestern University, McCormick School of Engineering and Applied Science, 1995.5.

[11]胡建侠, 刘瑞龙. 西安地铁杂散电流对地下管道的影响[J]. 材料保护, 2023, 56(08): 191-194+200.

[12]Chengyao L, Chunxiang Q, Huaicheng C, et al. Prediction of Compressive Strength of Concrete in Wet-Dry Environment by BP Artificial Neural Networks[J]. Advances in Materials Science and Engineering, 2018, 20181-11.

[13]马旭, 王新祥, 李建新. 水泥基材料抗外部硫酸盐侵蚀研究评述[J]. 广东建材, 2019, 35(06): 80-84.

[14]王承涛. 多因素影响下地铁杂散电流腐蚀行为及预测模型研究[D]. 中国矿业大学,2020.

[15]吴飞, 刘肖, 孔锴等. 杂散电流对地铁周边的危害及防治[J]. 建筑技术, 2021, 52 (08): 966-968.

[16]向开创中国地铁历史的一代人致敬——纪念中国第一条地铁通车50周年[J]. 都市快轨交通, 2019, 32(05): 10.

[17]吴嘉贤, 刘修岩. 空间经济视角下地铁建设与城市空间结构演化[J].现代经济探讨,2023(11):85-100.

[18]李高年. 杂散电流与硫酸盐耦合作用下水泥基材料的劣化机理[D]. 大连理工大学, 2021.

[19]王金川, 陈登. 水灰比和硫酸钠浓度对水泥基材料劣化过程的影响[J]. 混凝土与水泥制品, 2021, (07): 21-25.

[20]唐志, 杜镔, 王圳等. 硫酸盐溶液对掺石灰石粉砂浆抗硫酸盐侵蚀性能的影响[J]. 公路交通科技, 2023, 40(08): 51-56+62.

[21]Xiong C, Jiang L, Xu Y, et al. Deterioration of pastes exposed to leaching, external sulfate attack and the dual actions[J]. Construction and Building Materials, 2016, 11652-62.

[22]Santhanam M, Cohen M D, Olek J. Modeling the effects of solution temperature and concentration during sulfate arrack on cement mortars[J]. Cement and Concrete Research, 2002, 32(4): 585-592.

[23]郭玉柱, 王起才, 李盛等. 10℃下不同水灰比水泥基材料抗硫酸盐侵蚀性能试验研究[J]. 硅酸盐通报, 2017, 36(10): 3475-3480.

[24]Bonakdar A, Mobasher B, Chawla N. Diffusivity and micro-hardness of blended cement materials exposed to external sulfate attack[J]. Cement and Concrete Composites, 2012, 34(1): 76-85.

[25]王复生, 孙瑞莲, 朱元娜. 大掺量矿渣水泥抗硫酸盐侵蚀性能测试方法研究[J]. 建筑材料学报, 2009, 12(04): 466-469.

[26]罗遥凌, 殷吉强, 王冲等. 电场作用下水泥基材料的MgSO4侵蚀[J]. 湖南大学学报(自然科学版), 2017, 44(06): 69-74.

[27]乔宏霞, 何海杰, 何忠茂等. 抗硫酸盐水泥混凝土的合理试件尺寸选取[J]. 中国建材科技, 2012, 21(01): 59-62+67.

[28]Aiwen X, Ji L, Jiangtao X, et al. Sulfate resistance of Portland-Limestone cement mortars cured at 20℃and 60℃[J]. Journal of Sustainable Cement-Based Materials, 2022, 11(6): 370-377.

[29]Aköz F, Türker F, Koral S, et al. Effects of raised temperature of sulfate solutions on the sulfate resistance of mortars with and without silica fume[J]. Cement and Concrete Research,1999, 29(4): 537-544.

[30]李贵强, 芦令超, 王守德等.阿利特-硫铝酸钡钙水泥抗硫酸盐侵蚀性能的研究[J]. 硅酸盐通报, 2009, 28(05): 1038-1041+1045.

[31]Hucheng C, Songhui L, Liya Z, et al. Enhancing sulfate resistance of sulfate-aluminate cement grouting material through acrylamide in-situ polymerization modification[J]. Construction and Building Materials, 2023, 408.

[32]Junliang Z, Kangning S, Zhongkun W, et al. Effect of Nano-SiO2/Steel fiber on the mechanical properties and sulfate resistance of High-Volume fly ash cement materials[J]. Construction and Building Materials, 2023, 409.

[33]Yu Z, Ben L, Ying Y, et al. Sulfate resistance and degradation mechanism of basalt fiber modified graphite tailings cement-based materials[J]. Journal of Materials Research and Technology, 2023, 268757-8775.

[34]Huang Q, Zhu X, Zhao L, et al. Effect of nanosilica on sulfate resistance of cement mortar under partial immersion[J]. Construction and Building Materials, 2020, 2311171 80-117180.

[35]Guanglin D, Jun Y, Zhijun Y. Effects of coal gangue on the sulfate attack resistance of cement-based materials[J]. Ceramics-silikaty, 2021, 65(2): 148-157.

[36]许自强. 地铁运营中的电蚀及其对策[J]. 地下工程与隧道, 1988(01): 3-8.

[37]胡斌. 地铁迷流及上海地铁的迷流防护措施[J]. 电世界, 1994, 35(03): 2-4.

[38]Katarina V, Stjepan L, Marijana S. Corrosion and stray currents at urban track infrastructure[J]. Journal of the Croatian Association of Civil Engineers, 2020, 72(07): 593-606.

[39]Aghajani A, Urgen M, Bertolini L. Effects of DC Stray Current on Concrete Permeability[J]. Journal of Materials in Civil Engineering, 2015, 28(4): 04015177- 04015177.

[40]Susanto A, Koleva D A, Breugel K V. DC current-induced curing and ageing phenomena in cement-based materials[J]. 2014, 76(16): 5129.

[41]李金玉, 曹建国, 林莉等. 水工混凝土耐久性研究的新进展[J]. 水力发电, 2001 (04): 44-47+67.

[42]黄文新, 殷素红, 李铁锋等. 杂散电流对广州地铁混凝土溶蚀性能影响的加速试验研究[J]. 混凝土, 2008(08): 17-20+33.

[43]赵翊彤. 杂散电流对矿渣/水泥基复合材料的溶蚀作用[D]. 大连理工大学, 2021.

[44]黄谦, 王冲, 杨长辉等. 电场与硫酸盐侵蚀共同作用下混凝土的劣化及其机理[J]. 硅酸盐学报, 2016, 44(02): 239-245.

[45]Fang L, Yuanrui Z, Baomin W, et al. The Effect of Stray Current on Calcium Leaching of Cement-Based Materials[J]. Materials, 2022, 15(6): 2279-2279.

[46]Gaonian L, Baomin W, K. D P. Effect of Stray Current on Cement-Based Materials under Sulfate Attack[J]. Journal of Materials in Civil Engineering, 2022, 34(2):

[47]周莹.不同环境中电场对水泥基材料硫酸盐侵蚀的影响及机理[D].重庆大学,2017.

[48]王冲, 周莹, 黄谦. 土壤环境中电场与硫酸盐对水泥基材料性能的影响及机理[J]. 硅酸盐通报, 2017, 36(09): 3057-3063.

[49]王冲, 于超, 罗遥凌等. 不同侵蚀条件下水泥基材料碳硫硅钙石生成速度比较[J]. 同济大学学报(自然科学版), 2015, 43(05): 748-753.

[50]LuZ, DitaoN, BoW, et al. Migration and Reaction of Sulfate Ions in Concrete under Stray Current[J]. Department of Civil Engineering, Xi’an University of Architecture and Technology, Xi’an, Shaanxi Province, China;State Key Laboratory of Green Building in Western China, Department of Civil Engineering, Xi’an University of Architecture and Technology, Xi’an, Shaanxi Province, China, 2021, 49(6):

[51]黄谦. 电场与硫酸盐共存环境中水泥基材料的劣化及其机理研究[D]. 重庆大学, 2017.

[52]Baomin W, Gaonian L, K. D P .A study of variables that affect the process of sulfate attack of cement‐based materials subjected to stray current[J]. Structural Concrete, 2021,

23(2): 706-721.

[53]Chen L, Jiaqi L, Qiang R, et al. Degradation mechanism of blended cement pastes in sulfate-bearing environments under applied electric fields: Sulfate attack vs. decalcification[J]. Composites Part B, 2022,246.

[54]刘超, 蔡建赟, 朱超, 等. 硫酸盐干湿循环作用下煤矸石喷射混凝土劣化机理[J]. 硅酸盐通报, 2024, 43(10): 3686-3693.

[55]郑涛, 祝鹏程, 普如敏, 等.干湿循环硫酸盐侵蚀粉煤灰混凝土耐久性分析及抗蚀等级预测[J]. 隧道建设(中英文), 2024, 44(S1): 179-186.

[56]徐国会. 硫酸盐干湿循环作用下废水混凝土寿命预测模型[J]. 公路交通科技, 2024,

41(06): 36-45.

[57]Dong W, Wang J. Degradation mechanism and strength prediction of aeolian sand concrete under sulphate dry-wet cycles[J]. Construction and Building Materials, 2024, 450138617-138617.

[58]Wang H, Pang J .Mechanical Properties and Microstructure of Rubber Concrete under Coupling Action of Sulfate Attack and Dry–Wet Cycle[J]. Sustainability, 2023, 15(12):

[59]李福海, 黄绍宁, 肖赛, 等. 高温-干湿循环作用下混凝土分区抗硫酸盐侵蚀性能研究[J]. 西南交通大学学报, 1-10.

[60]何文正. 硫酸盐腐蚀作用下山岭隧道衬砌结构劣化及承载力演变研究[D]. 重庆交通大学, 2022.

[61]覃珊珊. 硫酸盐侵蚀混凝土劣化模型及耐久性失效研究[D]. 哈尔滨工业大学, 2022.

[62]杨建宇. 沿海变电站环境下混凝土结构耐久性的理论和试验研究[D].湖南大学, 2020.

[63]Baomin W, Gaonian L, K. D P. A study of variables that affect the process of sulfate attack of cement‐based materials subjected to stray current[J]. Structural Concrete, 2021, 23(2): 706-721.

[64]Lin J, Zhao Y, Liang Z, et al. Mechanical and damage characteristics study of concrete under repeated sulfate erosion[J]. Alexandria Engineering Journal, 2024, 109831-840.

[65]Jagadisha M H, Prashant S, Pandit P, et al. Sulfate resistance of alkali-activated flyash-slag-lime concrete: comparative study of drying-wetting cycles and conventional exposure[J]. Materials Research Express, 2024, 11(10): 105301-105301.

[66]Mousavinezhad S, Toledo K W, Newtson M C, et al. Rapid Assessment of Sulfate Resistance in Mortar and Concrete[J]. Materials, 2024, 17(19): 4678-4678.

[67]Chu H, Wang T, Guo M, et al. Effect of stray current on stability of bound chlorides in chloride and sulfate coexistence environment[J]. Construction and Building Materials, 2019, 194247-256.

[68]Chu H, Wang T, Guo M, et al. Effect of stray current on stability of bound chlorides in chloride and sulfate coexistence environment[J]. Construction and Building Materials, 2019, 194247-256.

[69]赵鸽. 电场作用下混凝土内氯离子扩散系数的时变规律[D]. 河南工业大学, 2023.

[70]张铖. 应力与碳化耦合作用下混凝土劣化过程及碳化深度预测模型研究[D]. 中国建筑材料科学研究总院, 2022.

[71]田源. 荷载与服役环境共同作用下混凝土中氯离子输运及寿命预测研究[D]. 哈尔滨工程大学, 2022.

[72]陈颖, 刘鹏, 尹健等. 硫酸盐和碳化耦合作用下混凝土劣化机理与耐久性评估研究进展[J]. 新型建筑材料, 2023, 50(05): 1-7.

[73]王宝民, 李高年, 韩俊南等. 杂散电流与环境耦合对水泥基材料耐久性影响研究进展[J]. 混凝土, 2019,(01): 8-12.

[74]Kaihua L, Zihang D, Rongbin Z, et al. Prediction of the sulfate resistance for recycled aggregate concrete based on ensemble learning algorithms[J]. Construction and Building Materials, 2022, 317.

[75]Yuan X, Qiang S, Tuo L, et al. Effect of water content and sodium sulfate concentration on the resistivity of red clay[J]. Studia Geophysica et Geodaetica, 2024, 68(1-2): 78-98.

[76]Olivier L, André A, Frédéric L, et al. Contribution to the Taking into Account of Environmental Factors of Vulnerability of Reinforced Concrete Buildings in the City of Douala-Cameroon[J]. International Journal of Sciences: Basic and Applied Research (IJSBAR), 2023, 68(1): 113-138.

[77]Paswan K R, Gogineni A, Sharma S, et al. Predicting split tensile strength in Portland and geopolymer concretes using machine learning algorithms: a comparative study[J]. Journal of Building Pathology and Rehabilitation, 2024, 9(2): 129-129.

[78]Zhang M, Gu Z, Zhao Y, et al. Compressive strength prediction of cement base under sulfate attack by machine learning approach[J]. Case Studies in Construction Materials, 2024, 21e03652-e03652.

[79]Geng Y S, Mei L, Cheng Y B, et al. Revolutionizing 3D concrete printing: Leveraging RF model for precise printability and rheological prediction[J]. Journal of Building Engineering, 2024, 88109127-.

[80]Hematibahar M, Kharun M, Beskopylny N A, et al. Analysis of Models to Predict Mechanical Properties of High-Performance and Ultra-High-Performance Concrete Using Machine Learning[J]. Journal of Composites Science, 2024, 8(8): 287-287.

[81]Kaihua L, Zihang D, Rongbin Z, et al. Prediction of the sulfate resistance for recycled aggregate concrete based on ensemble learning algorithms[J]. Construction and Building Materials, 2022, 317.