硅酸盐学报

基于电导率滴定的水泥基材料中硫酸根离子含量测试

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张云升 ¹ , 刘诚 ¹ , 王大富 ² , 李悦 ³ , 孙宇东 ²

硅酸盐学报 | 混凝土耐久性机理表征与预测方法专题—研究论文 2026,54(2): 527-541

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硅酸盐学报 |混凝土耐久性机理表征与预测方法专题—研究论文 2026 , 54 (2) : 527 -541

基于电导率滴定的水泥基材料中硫酸根离子含量测试

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张云升¹, 刘诚¹, 王大富², 李悦³, 孙宇东²

作者信息

^1．东南大学材料科学与工程学院，南京 211189

^2．云南大学建筑与规划学院，昆明 650091

^3．兰州理工大学土木工程学院，兰州 730050

作者简介:

张云升（1973—），男，博士，教授。

Test of SO₄^2- in Cement-Based Materials Based on Conductivity Titration

Yunsheng ZHANG¹, Cheng LIU¹, Dafu WANG², Yue LI³, Yudong SUN²

Affiliations

^1.School of Materials Science and Engineering, Southeast University, Nanjing 211189, China

^2.School of Architecture and Planning, Yunnan University, Kunming 650091, China

^3.School of Civil Engineering, Lanzhou University of Technology, Lanzhou 730050, China

ZHANG Yunsheng (1973-), male, Ph.D., Professor. E-mail: zhangyunsheng2011@163.com

出版时间: 2026-02-20 doi: 10.14062/j.issn.0454-5648.20250433

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摘要

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准确获取水泥基材料中SO₄^2-含量是揭示腐蚀机理、建立腐蚀模型、提出耐久设计方法和运维措施等工作的前提条件。本研究从电导率滴定原理、设备、步骤、模型、参数及干扰离子的去除等方面进行了探讨。并与传统的重量法和乙二胺四乙酸（EDTA）滴定法进行了对比。结果表明：通过自行研发的电导率滴定仪能准确测试硫酸盐腐蚀的水泥基材料中自由和总SO₄^2-，滴定剂选用Ba（NO₃）₂，其最小分辨率0.1 mmol/L、标准差0.41，回收率103%；SO₄^2-电导率滴定曲线可划分为：未饱和段、结晶成核段、晶体生长段、准反应结束段、反应结束段和无限滴定段；通过建立的SO₄^2-电导率滴定模型可获得滴定剂浓度和待测液体积的最佳范围，以及HCl、NaOH和NaCl对滴定剂浓度和待测液体积的最佳范围的影响；可采用CO₂和HCl方式去除自由SO₄^2-测试时OH^-和Ca²⁺等干扰性离子的影响；在酸溶SO₄^2-测试时，采用HCl作为溶解液，并可采用Ag₂O、CO₂和HCl方式去除大量的H⁺、Cl^-和Ca²⁺等干扰性离子的影响；最终获得了高效、准确和经济的测试水泥基材料中SO₄^2-含量的方法。

关键词

硫酸根离子测试 / 电导率滴定 / 硫酸盐腐蚀 / 耐久性 / 水泥基材料

Abstract

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Introduction

It is essential for understanding sulfate-induced deterioration mechanisms to quantify sulfate ions (SO₄^2-) in cement-based materials accurately. Reliable sulfate measurements are also required for developing corrosion prediction models and for supporting durability-oriented design and maintenance strategies. Conventional analytical methods, including gravimetric analysis and ethylenediaminetetraacetic acid (EDTA) titration, have limitations in highly alkaline and turbid cement extracts that contain multiple interfering ions such as Ca²⁺, Mg²⁺, OH^-, Na⁺, and Cl^-. These characteristics complicate endpoint identification and reduce measurement precision. The difficulty becomes more pronounced when sulfate concentrations are low, which is typical in the early and intermediate stages of sulfate ingress. Therefore, a rapid, accurate and interference-resistant technique is required. This study was to establish conductivity titration as a reliable method for quantifying sulfate in cement-based materials.

Methods

The conductivity titration system used was constructed with a DJS series conductivity electrode, a DS18B20 temperature compensation module, an automated peristaltic pump and a microcontroller unit. Barium nitrate (Ba(NO₃)₂) was selected as a titrant. Standard sulfate solutions were first tested to establish the characteristic stages of the titration process. The titration curve of SO₄^2- conductivity could be divided into unsaturated section, crystallization nucleation section, crystal growth section, quasi-reaction end section, reaction end section and infinite titration section. The endpoint was identified by a slope transition between the crystal growth and completion stages.

Optimal operational parameters were identified through repeated tests. These included the appropriate titrant concentration, droplet rate, sample volume and working temperature. Interference-removal procedures were then developed to address the complex ionic environment of cement-based systems. Carbon dioxide (CO₂) was used to eliminate OH^- and Ca²⁺ during free sulfate measurements. A treatment involving silver oxide(Ag₂O), carbon dioxide (CO₂) and hydrochloric acid (HCl) was applied to eliminate H⁺, Ca²⁺ and Cl^- during total sulfate analysis. The accuracy, resolution, and repeatability of conductivity titration were validated using standard SO₄^2- solutions and compared with gravimetric and EDTA titration methods.

Results and discussion

The optimized conductivity titration system achieves a minimum SO₄^2- resolution of 0.1 mmol/L, indicating sufficient sensitivity for detecting sulfate ingress in cement-based materials. Clear and reproducible inflection points appear on conductivity-volume curves even at low concentrations, ensuring accurate endpoint identification. For a solution containing 0.01 mol/L SO₄^2-, a titrant concentration of at least 0.033 mol/L Ba(NO₃)₂ produces a slope change greater than 60°, confirming a distinct crystallization transition. The results of repeatability tests verify the stability of the method, and 20 consecutive titrations yield an average titrant consumption of approximately 5 mL with a standard deviation of 0.41.

Interference removal proves an essential for maintaining measurement accuracy. CO₂ and HCl can be used to remove some interfering ions such as OH^- and Ca²⁺ in the test of free sulfate ions. In the acid-soluble sulfate test, HCl is used as a dissolution solution. Ag₂O, CO₂ and HCl can be used to remove a large number of interfering ions such as H⁺, Cl^- and Ca²⁺, and improve the stability of the titration curves. The results of comparative experiments show that conductivity titration provides more reliable results than gravimetric analysis and EDTA titration when samples are turbid, contain multivalent cations or exhibit a unstable color, or when SO₄^2- concentrations vary in a wide range. The gravimetric analysis produces large errors at SO₄^2- contents of below 0.5%, and the EDTA titration is strongly affected by Ca²⁺, Mg²⁺ and turbidity. In contrast, the conductivity titration accurately reflects changes in ionic composition regardless of solution appearance.

The results of tests on sulfate-exposed cement paste confirm that the method can resolve SO₄^2- profiles and diffusion gradients within the material. This ability demonstrates its potential for evaluating the progression of sulfate attack and for supporting durability assessment and corrosion monitoring.

Conclusions

The conductivity titration could provide an accurate and stable quantification of both free and total SO₄^2- in cement-based materials. The optimized titration parameters produced clear and reproducible inflection points on conductivity-volume curves, enabling reliable endpoint identification even at low sulfate concentrations. The pretreatment procedures designed for alkaline and ion-rich cement extracts effectively eliminated OH^-, Ca²⁺, H⁺ and Cl^-, ensuring a high measurement precision. The results of comparative tests showed that conductivity titration exhibited significantly better adaptability than gravimetric analysis and EDTA titration, especially for turbid or multi-ion systems. Application of the method to sulfate-exposed cement paste confirmed its capability to resolve sulfate profiles and identify diffusion gradients. This study demonstrated that conductivity titration could be an effective analytical tool for sulfate determination in cementitious materials and offer a promising potential for improving durability evaluation and corrosion monitoring in concrete structures.

Key words

sulfate ion test / conductivity titration / sulfate corrosion / durability / cement-based materials

引用本文

张云升, 刘诚, 王大富, 李悦, 孙宇东. 基于电导率滴定的水泥基材料中硫酸根离子含量测试. 硅酸盐学报, 2026 , 54 (2) : 527 -541 . DOI: 10.14062/j.issn.0454-5648.20250433

Yunsheng ZHANG, Cheng LIU, Dafu WANG, Yue LI, Yudong SUN. Test of SO₄^2- in Cement-Based Materials Based on Conductivity Titration[J]. Journal of the Chinese Ceramic Society, 2026 , 54 (2) : 527 -541 . DOI: 10.14062/j.issn.0454-5648.20250433

基金

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国家自然科学基金项目(2023YFB3711400; 52408299)

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2026年第54卷第2期

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文章信息

doi: 10.14062/j.issn.0454-5648.20250433

接收时间：2025-06-04
首发时间：2026-10-27
出版时间：2026-02-20

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收稿日期：2025-06-04
修回日期：2025-06-21

基金

国家自然科学基金项目(2023YFB3711400; 52408299)

作者信息

^1．东南大学材料科学与工程学院，南京 211189

^2．云南大学建筑与规划学院，昆明 650091

^3．兰州理工大学土木工程学院，兰州 730050

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2种不同金属材料的力学参数

科 Family	属数 Number of genus	种数 Number of species	占总种数比例 Percentage of total species (%)	属 Genus	种数 Number of species	占总种数比例 Percentage of total species (%)
鹅膏菌科Amanitaceae	2	11	5.26	鹅膏菌属 Amanita	10	4.78
小菇科 Mycenaceae	2	12	5.74	丝盖伞属 Inocybe	5	2.39
多孔菌科 Polyporaceae	8	14	6.70	蜡蘑属 Laccaria	5	2.39
红菇科 Russulaceae	3	23	11.00	小皮伞属 Marasmius	6	2.87
				小菇属 Mycena	11	5.26
				光柄菇属 Pluteus	5	2.39
				红菇属 Russula	17	8.13
				栓菌属 Trametes	5	2.39

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