硅酸盐学报

硫酸盐侵蚀初期泡沫轻质土力学及孔隙演化

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万勋 ¹^,² , 张振 ¹^,² , 叶观宝 ¹^,² , 赵建军 ³ , 张欢 ³^,⁴

硅酸盐学报 | 研究论文 2025,53(11): 3079-3090

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硅酸盐学报 |研究论文 2025 , 53 (11) : 3079 -3090

硫酸盐侵蚀初期泡沫轻质土力学及孔隙演化

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万勋¹^,², 张振¹^,², 叶观宝¹^,², 赵建军³, 张欢³^,⁴

作者信息

^1．同济大学土木工程学院，上海 200092

^2．同济大学岩土及地下工程教育部重点实验室，上海 200092

^3．成都理工大学地质灾害防治与地质环境保护全国重点实验室，成都 610059

^4．川设（四川）工程咨询有限公司，成都 610036

通讯作者:

张振（1984—），男，博士，研究员。

作者简介:

万勋（1997—），男，博士研究生。

Mechanical Behavior and Pore Structure Evolution of Foamed Cement Pastes in the Early Stage of Sulphate Attack

Xun WAN¹^,², Zhen ZHANG¹^,², Guanbao YE¹^,², Jianjun ZHAO³, Huan ZHANG³^,⁴

Affiliations

^1.College of Civil Engineering, Tongji University, Shanghai 200092, China

^2.Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092, China

^3.State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu 610059, China

^4.Chuanshe (Sichuan) Engineering Consulting Co., Ltd., Chengdu 610036, China

Corresponding Author:

ZHANG Zhen (1984-), male, Ph.D., Professor. E-mail: 14149@tongji.edu.cn

WAN Xun (1997-), male, Doctoral candidate. E-mail: 2210402@tongji.edu.cn

出版时间: 2025-11-20 doi: 10.14062/j.issn.0454-5648.20250144

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摘要

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泡沫轻质土由于其独特的孔隙结构，在硫酸盐侵蚀条件下其强度演化特征很可能不同于混凝土，侵蚀初期物化反应引起的孔隙结构演化及其与力学特性的关联机制尚不明确。基于单轴压缩试验和X射线计算机断层扫描技术联合核磁共振方法，研究了Na₂SO₄质量分数，龄期对侵蚀初期泡沫轻质土力学性能和孔隙特征的影响。结果表明：相比于标准试样，试样在侵蚀后力学性能衰减。然而，随着龄期增加（28~56 d），峰值强度和残余强度回升分别可达19.28%和55.56%。随Na₂SO₄质量分数增加，含水大孔（>100 µm）分布频率减小，从25.66%降至9.49%，相应峰值强度变化率回升。侵蚀初期，试样的含水孔隙度高于同期自来水浸润后的试样，且随着质量分数增加，总含水孔隙度先减小而后趋于不变。随着泡沫轻质土试样含水孔隙度减小，其峰值强度和残余强度呈指数上升。研究结果对于深入认识服役环境对泡沫轻质土早期工程性能的影响具有指导意义。

关键词

泡沫轻质土 / 硫酸盐侵蚀 / 力学特性 / 含水孔隙度 / 核磁共振 / X射线计算机断层扫描

Abstract

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Introduction

Foamed cement paste (FCP) is a type of cementitious geotechnical material with a high porosity structure, prepared by mixing cement paste with preformed foam and sometimes incorporating soil materials such as clay, silica fume, fly ash, and sand. Due to its lightweight nature, excellent self-supporting ability, easy construction, and environmental friendliness, FCP has been widely used in embankment fills, bridge abutment backfills, slope reinforcement, and retaining wall applications. However, in saline soil regions, FCP is subjected to chemical attacks, particularly sulphate attack, in addition to environmental factors such as temperature fluctuations and water infiltration. The early stage of sulphate attack plays a critical role in determining the long-term durability of FCP. Unlike conventional concrete, which may experience initial strength gain due to ettringite and gypsum formation, FCP's unique pore structure may result in different degradation patterns. At this stage, the interaction between pore water, sulphate ions, and cement hydration products can lead to either early-stage degradation or partial densification. However, the mechanisms linking early-stage mechanical behavior and pore evolution remain unclear. This study focuses on the mechanical behavior and pore structure evolution of FCP during the early stage of sulphate attack. Specimens were exposed to Na₂SO₄ solutions (0%, 0.5%, 2.5%, 5.0%) for 28 d and 56 d, representing the early-stage exposure period. A combination of uniaxial compression testing, X-ray computed tomography (X-CT), and nuclear magnetic resonance (NMR) analysis was used to evaluate the changes in strength, aquiferous pore size distribution, and aquiferous porosity. The findings provide key insights into the initial degradation mechanisms of FCP, highlighting the competing roles of skeleton softening due to water absorption and pore densification due to sulphate reaction products, which are of great significance for further understanding of the influence of service environment on the engineering performance of FCP.

Methods

FCP specimens were prepared using P.C42.5 composite Portland cement, anionic foaming agent LG-2258, and tap water. The water-to-cement ratio (m_w/m_c) was set at 0.45, and the foam volume ratio (V_f/V_w) was controlled at 3.5 to achieve a final wet density of approximately 0.9 g/cm³. The specimens were cast in cubic molds (70.7 mm × 70.7 mm × 70.7 mm), demolded after 24 h, and cured under standard conditions [(20 ± 2) ℃, RH > 95%)] for 28 d. To eliminate the influence of initial moisture content on sulphate attack, all specimens were oven-dried at 60 ℃ to a constant weight before sulphate attacking. A multi-field coupling test device was used to control sulphate attack conditions, maintaining a constant temperature of 20 ℃ and an osmotic pressure of 10 kPa. The specimens were exposed in Na₂SO₄ solutions (0%, 0.5%, 2.5%, 5.0%) for 28 d and 56 d, simulating the early stage of sulphate attack. After attacking, NMR and X-CT analyses were conducted to assess aquiferous pore structure and aquiferous porosity, followed by uniaxial compression testing at a loading rate of 2 mm/min. Each experiment was repeated at least three times to ensure accuracy and repeatability.

Results and discussion

Uniaxial compression test results showed that, during the early stage of sulphate attack, FCP specimens initially experienced strength reduction compared to the standard condition. However, partial strength recovery was observed after 56 d, particularly at 2.5% Na₂SO₄ concentration, where the peak strength increased by 19.28% and the residual strength increased by 55.56%. This indicates a transition from initial degradation to partial densification, likely due to the formation of sulphate reaction products. Unlike traditional concrete, which often exhibits a continuous strength increase in the early sulphate attack phase, FCP's unique pore structure resulted in a more complex response. At low sulphate concentrations (0.5%), sulphate attack increased porosity, accelerating early-stage degradation. However, at higher sulphate concentrations (2.5% and 5.0%), reaction products partially filled existing pores, leading to strength recovery. X-CT and NMR analyses revealed that sulphate attack significantly altered the aquiferous pore structure of FCP in the early stage: 1) Macropore frequency (>100 µm) decreased as sulphate concentration increased, indicating pore filling by reaction products. 2) Small pore frequency (1-10 µm) increased, particularly at 2.5% and 5.0% Na₂SO₄, due to the formation of ettringite and gypsum. 3) Total aquiferous porosity of sulphate-attacked specimens was higher than that of water-immersed specimens, suggesting that sulphate ions modified water retention behavior. A strong exponential correlation was observed between aquiferous porosity and mechanical strength. As aquiferous porosity decreased, both peak and residual strength increased, confirming that sulphate-induced microstructural changes significantly influence mechanical performance.

Conclusions

The main conclusion of this work are summarized as following: 1) Sulphate attack in the early stage first weakens FCP, then triggers partial strength recovery. Peak and residual strength initially declined, but after 56 d, peak strength increased by 19.28% and residual strength by 55.56%, particularly at 2.5% Na₂SO₄ concentration. 2) FCP's early-stage sulphate attack behavior differs from traditional concrete. At low sulphate concentrations (0.5%), sulphate attack increased aquiferous porosity, accelerating early-stage degradation. However, at higher concentrations (2.5% and 5.0%), sulphate reaction products partially filled pores, leading to strength recovery. 3) Sulphate attack altered FCP's aquiferous pore structure in the early stage. Macropores (>100 µm) decreased, while small pores (1-10 µm) increased, indicating that sulphate products influenced pore connectivity and densification. 4) A strong exponential relationship was identified between aquiferous porosity and strength. As aquiferous porosity decreased, both peak and residual strength increased, demonstrating that sulphate-induced pore transformations impact mechanical stability. These findings highlight the critical role of the early attack stage in determining the long-term durability of FCP, offering new insights for optimizing its application in sulphate-rich environments.

Key words

foamed cement paste / sulphate attack / mechanical property / aquiferous porosity / nuclear magnetic resonance / X-ray computed tomography

引用本文

万勋, 张振, 叶观宝, 赵建军, 张欢. 硫酸盐侵蚀初期泡沫轻质土力学及孔隙演化. 硅酸盐学报, 2025 , 53 (11) : 3079 -3090 . DOI: 10.14062/j.issn.0454-5648.20250144

Xun WAN, Zhen ZHANG, Guanbao YE, Jianjun ZHAO, Huan ZHANG. Mechanical Behavior and Pore Structure Evolution of Foamed Cement Pastes in the Early Stage of Sulphate Attack[J]. Journal of the Chinese Ceramic Society, 2025 , 53 (11) : 3079 -3090 . DOI: 10.14062/j.issn.0454-5648.20250144

基金

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国家自然科学基金面上项目(42377165)
上海市自然基金面上项目(22ZR1466600)

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2025年第53卷第11期

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doi: 10.14062/j.issn.0454-5648.20250144

接收时间：2025-03-05
首发时间：2026-10-21
出版时间：2025-11-20

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出版历史

收稿日期：2025-03-05
修回日期：2025-03-19

基金

国家自然科学基金面上项目(42377165)

上海市自然基金面上项目(22ZR1466600)

作者信息

^1．同济大学土木工程学院，上海 200092

^2．同济大学岩土及地下工程教育部重点实验室，上海 200092

^3．成都理工大学地质灾害防治与地质环境保护全国重点实验室，成都 610059

^4．川设（四川）工程咨询有限公司，成都 610036

通讯作者:

张振（1984—），男，博士，研究员。

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https://castjournals.cast.org.cn/joweb/gsyxb/CN/10.14062/j.issn.0454-5648.20250144

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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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