硅酸盐学报

C-S-H氯离子吸附新见解：孔结构与双电层协同效应

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张勇 ¹^,² , 戴梓杭 ² , 尹键丽 ¹ , 杨政险 ²

硅酸盐学报 | 研究论文 2026,54(8): 2874-2886

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硅酸盐学报 |研究论文 2026 , 54 (8) : 2874 -2886

C-S-H氯离子吸附新见解：孔结构与双电层协同效应

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张勇¹^,², 戴梓杭², 尹键丽¹, 杨政险²

作者信息

^1．垒知控股集团股份有限公司，科之杰新材料集团有限公司，福建厦门 361100

^2．福州大学土木工程学院，福州 350108

通讯作者:

尹键丽（1982—），女，正高级工程师。

作者简介:

张勇（1985—），男，博士，副研究员。

Coupled Effects of Pore Structure and Electrical Double Layer on Chloride Uptake by Calcium Silicate Hydrate

Yong ZHANG¹^,², Zihang DAI², Jianli YIN¹, Zhengxian YANG²

Affiliations

^1.KZJ New Materials Group Co., Ltd., Lets Holdings Group Co., Ltd., Xiamen 361100, Fujian, China

^2.College of Civil Engineering, Fuzhou University, Fuzhou 350108, China

Corresponding Author:

{YIN} Jianli (1982-), female, Professor-level Senior Engineer. E-mail: 46486427@qq.com

ZHANG Yong (1985-), male, Ph.D., Associate Research Fellow. E-mail: y.zhang@fzu.edu.cn

出版时间: 2026-05-13 doi: 10.14062/j.issn.0454-5648.20250851

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摘要

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水化硅酸钙（C-S-H）对氯离子（Cl^-）的吸附性能是混凝土抗氯侵蚀耐久性的关键影响因素。既有研究多侧重孔结构或表面电荷的单一作用，对二者的协同调控机制及量化方法仍缺乏系统阐释。采用化学沉淀法制备钙硅摩尔比为0.6~1.8的系列C-S-H凝胶，利用氮气吸附表征孔隙几何特征，通过Zeta电位测试解析界面电荷特性；基于Gouy-Chapman-Stern理论，引入Poisson-Boltzmann与Nernst-Planck方程，构建孔结构-双电层协同吸附模型，并结合实验测试进行验证。结果表明，C-S-H的Cl^-吸附行为由孔隙几何限域与双电层静电作用协同主导。低钙硅比（0.6）体系孔体积较大（0.11 cm³·g^-1），但表面负电位偏高（-15~-17 mV），强静电排斥导致总吸附量偏低；高钙硅比（1.8）体系表面电位较低（-8~-10 mV），但孔隙致密化（0.04 cm³·g^-1）限制了Cl^-富集；中等钙硅比（≈1.0）体系孔体积（0.07 cm³·g^-1）与表面电荷（-13~-15 mV）实现优化匹配，协同驱动吸附量达到峰值。本工作揭示了孔结构-双电层协同调控Cl^-吸附机制，为抗氯侵蚀胶凝材料的微结构设计与耐久性提升提供了新视角。

关键词

水化硅酸钙 / 钙硅比 / 双电层 / 孔结构 / 氯离子吸附 / 协同效应

Abstract

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Introduction

The chloride (Cl^-) binding capability of calcium silicate hydrate (C-S-H) plays an important role in the chloride resistance and, consequently, the service life of concrete used in marine and deicing environments. The synergistic regulation between geometric confinement and electrostatic interactions and its dependence on the Ca/Si ratio remain insufficiently resolved although the existing studies examine either pore structure (accessibility and transport) or interfacial electrostatics (electrical double layer, EDL). This gap is addressed via establishing a coupled pore structure-EDL framework calibrated against a controlled C-S-H series at different calcium-silicon (Ca/Si) ratios, thereby transforming qualitative descriptions into the mechanism-based quantification of chloride adsorption. In this study, systematic measurements and mathematical descriptions were performed to clarify the C-S-H pore structure, surface potential distribution, and chloride binding capacity. Effects of the Ca/Si and chloride concentrations were investigated. The dynamic competition mechanism between pore-scale accommodation and EDL-mediated electrostatic partitioning was quantitatively characterized.

Methods

C-S-H gels with different targeted Ca/Si ratios (i.e., 0.6, 1.0, 1.4, and 1.8) were prepared via chemical precipitation with sodium silicate and calcium nitrate in deionized water. After homogenization, the suspensions were adjusted to pH value of ≥ 12 by using 5 mol/L NaOH solution and then transferred to a polytetrafluoroethylene (PTFE)-lined autoclave and crystallized isothermally

at (60 ± 1) ℃ for 14 d. The product was recovered by vacuum filtration using a Büchner funnel, washed for three times with deionized water, and dried in a vacuum oven at 50 ℃ for 72 h. The dried solid was then ground in a ball mill, passed through a 200-mesh sieve, and stored in a desiccator.

The total pore volume and pore-size distribution (PSD) of the C-S-H gels with varying Ca/Si ratios were determined by nitrogen sorption. The characteristic pore diameter and the gel pores below 10 nm, which were most relevant for transport and EDL overlap in C-S-H clusters, were measured. The Zeta potential (ζ) was measured in alkaline media (pH value of 12) over ionic strengths representative of pore solutions (e.g., 0.1-0.5 mol·L^-1 NaCl). The batch adsorption was conducted via equilibrating C-S-H powders in NaCl solutions at (20.0±0.1) ℃ for 14 d. Supernatants were filtered and analyzed by ion chromatography to determine equilibrium Cl^- concentrations, and adsorption capacities were calculated by mass balance and normalized to solid mass. The Gouy-Chapman-Stern (GCS) framework was implemented in cylindrical pores to couple measured ζ at different pore sizes, explicitly accounting for the Stern layer, diffuse layer, the Debye length, and the EDL overlap in nanoscale. The steady-state Poisson-Boltzmann/Nernst-Planck system was solved to obtain spatial electrostatic potentials and local Cl^- concentrations. The total adsorption was computed via integrating the EDL-related concentration profiles at different pore sizes. The model predictions were compared and validated by the experiments.

Results and discussion

The C-S-H specimens with varying Ca/Si ratios normally exhibit unimodal gel-type porosity with dominant mesopores of 3-5 nm, accompanied by a tail extending into larger sizes. Increasing Ca/Si leads to densification, and the cumulative volume of gel pores below 10 nm decreases from approximately 0.11 cm³·g^-1 to 0.04 cm³·g^-1 when Ca/Si increases from 0.6 to 1.8. The zeta potential becomes less negative with increasing Ca/Si ratio, changing from -17 mV (at Ca/Si ratio of 0.6) to -10 mV (at Ca/Si ratio of 1.8) in the case of 0.1 mol·L^-1 NaCl. As electrolyte concentration increases from 0.1 mol·L^-1 to 0.5 mol·L^-1, and |ζ|decreases due to the classical EDL compression. The Debye lengths in the 0.3-1.0 nm imply a substantial EDL overlap within the characteristic gel pores (3-5 nm), eliminating the notion of an electroneutral pore core and promoting field-driven partitioning.

The role of Ca/Si ratio in chloride binding behavior reveals a composition-dependent balance. At a low Ca/Si ratio (i.e., 0.6), the large pore volume favors chloride accommodation, while the highly negative surface potential causes a great electrostatic exclusion of Cl^- near the C-S-H walls. Within confined gel pores, overlapping EDLs shift Cl^- towards the pore center and reduce near-surface concentrations, limiting net chloride uptake despite abundant void space. At an intermediate Ca/Si ratio (i.e., 1.0), the pore volume remains high, while |ζ| is moderated, yielding the most favorable balance between geometric access and electrostatic capture. The modeled profiles and measurements both indicate the maximum adsorption capacity at this intermediate Ca/Si composition, consistent with a synergy between transport accommodation and weakened repulsion. At a high Ca/Si ratio (i.e., 1.8), weaker repulsion can, in principle, increase the interfacial adsorption efficiency per unit area, but the gel densification causes a sharp loss of accessible pore volume (i.e., 0.04 cm³·g^-1), becoming a dominant limiting factor for the reduced overall Cl^- uptake.

A model-experiment agreement is established, demonstrating the non-linear Freundlich-like increase of chloride adsorption with solution concentration. The measured ζ and PSD provide a physically interpretable parameter set for quantitative prediction of Cl^- binding capacity of C-S-H. The densification (at a high Ca/Si ratio) or electrostatic exclusion (a low Ca/Si ratio) can dominate Cl^- adsorption, depending on the composition-controlled balance of the effects. The results identify an intermediate composition window that maximizes Cl^- binding via leveraging moderate surface charge and mesoporous access.

Conclusions

Chloride uptake by C-S-H could be controlled by a dual mechanism, i.e., with gel pore geometry dictating accommodation and transport, while EDL electrostatics governing near-surface adsorption. A low Ca/Si ratio (i.e., 0.6) provided large gel pore volumes but suffered great electrostatic exclusion. A high Ca/Si ratio (i.e., 1.8) weakened a repulsion but substantially densified the gel, resulting in a limited adsorption. An intermediate Ca/Si ratio (i.e., ≈1.0) achieved the optimum synergy between pore accessibility and moderated EDL effects, resulting in a peak Cl^- adsorption. The pore structure-EDL coupling framework proposed in this work could quantitatively link pore sizes and surface potential distribution to chloride adsorption capacity and provide actionable targets for binder design to enhance chloride resistance in service. Cementitious binders that preserved a mesopore network enriched in 3-5 nm pores and moderated surface charge exhibited a superior chloride binding capacity.

Key words

calcium silicate hydrate / calcium-silicon ratio / electrical double layer / pore structure / chloride adsorption / coupled effect

引用本文

张勇, 戴梓杭, 尹键丽, 杨政险. C-S-H氯离子吸附新见解：孔结构与双电层协同效应. 硅酸盐学报, 2026 , 54 (8) : 2874 -2886 . DOI: 10.14062/j.issn.0454-5648.20250851

Yong ZHANG, Zihang DAI, Jianli YIN, Zhengxian YANG. Coupled Effects of Pore Structure and Electrical Double Layer on Chloride Uptake by Calcium Silicate Hydrate[J]. Journal of the Chinese Ceramic Society, 2026 , 54 (8) : 2874 -2886 . DOI: 10.14062/j.issn.0454-5648.20250851

基金

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国家自然科学基金(52478241)
福建省自然科学基金(2024J01264)
中国博士后科学基金(2024M751270)

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2026年第54卷第8期

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文章信息

doi: 10.14062/j.issn.0454-5648.20250851

接收时间：2025-11-17
首发时间：2026-10-22
出版时间：2026-05-13

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收稿日期：2025-11-17
修回日期：2025-12-11

基金

国家自然科学基金(52478241)

福建省自然科学基金(2024J01264)

中国博士后科学基金(2024M751270)

作者信息

^1．垒知控股集团股份有限公司，科之杰新材料集团有限公司，福建厦门 361100

^2．福州大学土木工程学院，福州 350108

通讯作者:

尹键丽（1982—），女，正高级工程师。

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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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