硅酸盐学报

涂层防护对低真空暴露混凝土性能的影响规律

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程冠之 ¹^,³ , 林红威 ² , 李咏昊 ² , 庄扬波 ² , 韩松 ² , 韩冰 ² , 李大林 ¹^,³

硅酸盐学报 | 研究论文 2025,53(5): 1133-1143

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硅酸盐学报 |研究论文 2025 , 53 (5) : 1133 -1143

涂层防护对低真空暴露混凝土性能的影响规律

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程冠之¹^,³, 林红威², 李咏昊², 庄扬波², 韩松², 韩冰², 李大林¹^,³

作者信息

^1．中国铁道科学研究院集团有限公司铁道建筑研究所，北京 100081

^2．北京交通大学土木建筑工程学院，北京 100044

^3．高速铁路轨道系统全国重点实验室，北京 100081

通讯作者:

林红威（1989—），男，博士，副教授。

作者简介:

程冠之（1987—），男，博士，副研究员。

Effects of Surface Coating on Concrete Properties Under Low Vacuum Environment

Guanzhi CHENG¹^,³, Hongwei LIN², Yonghao LI², Yangbo ZHUANG², Song HAN², Bing HAN², Dalin LI¹^,³

Affiliations

^1.Railway Engineering Research Institute, China Academy of Railway Sciences Corporation Limited, Beijing 100081, China

^2.School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China

^3.State Key Laboratory for Track System of High-Speed Railway, Beijing 100081, China

Corresponding Author:

LIN Hongwei (1989-), male, Ph.D., Associate Professor. E-mail: hwlin@bjtu.edu.cn

CHENG Guanzhi (1987-), male, Ph.D., Associate Professor. E-mail: chengguanzhi@163.com

出版时间: 2025-05-20 doi: 10.14062/j.issn.0454-5648.20240606

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摘要

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低真空管道是超高速低真空磁悬浮交通系统的核心运行平台，内部环境具有极低气压、交变气流、极低湿度等环境特点。采用涂层对混凝土进行防护是保证管道内混凝土安全服役的有效措施之一。为研究低真空环境下涂层防护对混凝土质量损失、力学强度与微观结构等的影响规律，对经常压养护和真空暴露的涂层防护C50混凝土开展质量损失、力学强度和涂料附着强度测试，并通过扫描电子显微镜（SEM）和背散射电子（BSE）图像观察涂层表面以及硬化水泥浆体的微观形貌和物相。结果表明：低真空环境下氟碳涂层体系能有效抑制低真空环境下混凝土内部自由水的散失，涂层防护混凝土的质量损失率明显小于无涂层混凝土。在常压和低真空环境下，涂层均可显著提升混凝土弯拉强度，但对抗压强度表现出了一定的不利影响。无论是否采用涂层防护，早龄期低真空暴露均对混凝土抗压及弯拉强度不利。此外，有涂层硬化水泥浆体试样的孔隙率相较于无涂层试样降低了18.1%，说明涂层能够抑制低真空环境对硬化浆体内部结构的不利影响，使硬化浆体的孔隙率降低。随着混凝土龄期增长，常压及真空环境中涂层附着强度均缓慢增大。经真空暴露后，涂层附着强度略有提升。

关键词

混凝土 / 低真空环境 / 涂层防护 / 质量损失 / 强度

Abstract

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Introduction

Low-vacuum tunnels are the core infrastructure of ultra-high-speed low-vacuum magnetic levitation transportation systems. The internal environment of these tunnels is characterized by extremely low pressure, alternating airflows, and very low humidity. Based on a comprehensive review of existing research, concrete is considered a highly competitive material for low-vacuum tunnels due to its cost-effectiveness and technological maturity. However, studies have shown that under conditions of extremely low pressure and fluctuating atmospheric pressure, concrete experiences rapid moisture loss, resulting in significant changes to its pore structure and leading to the deterioration of its mechanical properties and long-term performance. Additionally, the high-velocity airflow caused by alternating pressure in low-vacuum tunnels can induce aerodynamic fatigue damage to the internal and external surfaces of the concrete, generating severe dust that poses a significant threat to the safe operation of high-speed trains. To address these challenges and ensure the reliable performance of concrete in low-vacuum environments, protective measures or the use of high air-tightness concrete is necessary. Coating materials have been identified as an effective solution to enhance the service safety of concrete in vacuum tunnels.

Methods

The cement used was P·I 42.5 Portland cement produced by Fushun Cement Co., Ltd. Fine aggregates consisted of natural river sand with a fineness modulus of 2.8. Coarse aggregates were crushed limestone with continuous gradation, sized between 5 mm and 20 mm, with a mud content of 0.4%. Water used was municipal tap water. The water-reducing agent was a non-air-entraining polycarboxylate- based superplasticizer. The coating system was a two-component fluorocarbon material jointly developed by Beijing Jiaotong University, consisting of a solvent-free epoxy penetrating primer and a fluorocarbon resin topcoat. The primary film-forming material was fluorocarbon resin, with hexamethylene diisocyanate as the hardener, and the pigment-to-binder ratio of the coating was 0.4.

To better understand the effect of coating materials on concrete performance, the coating was applied during the early hydration stage of concrete. After casting, the specimens were stored at (20 ± 2) ℃ for one day before demolding, after which the primer coat was applied. Following two days of air drying, the topcoat was applied, and the specimens were further air-dried for two days. The compressive and flexural strengths of the concrete were tested using specimens sized 300 mm × 100 mm × 100 mm and 400 mm ×100 mm × 100 mm, respectively. To evaluate the impact of surface coating on concrete mass loss, specimens of 40 mm × 40 mm × 40 mm were prepared. Adhesion strength tests were conducted to examine the effects of low-vacuum environments on the coating's adhesion. Hardened cement paste samples with the same water-to-cement ratio as C50 concrete (0.37) were also prepared, cured to the specified age, cut into cylinders with heights of 20 mm and 10 mm, and embedded in epoxy resin for analysis. Hydration was terminated by immersing these samples in isopropanol.

The surface coating's effects on C50 concrete were further analyzed using scanning electron microscopy (SEM) and backscattered electron (BSE) analysis. Atmospheric curing was conducted in a standard curing chamber at (20 ± 2) ℃ and ≥95% relative humidity. A U-shaped vacuum chamber with a pressure range of 1000-2000 Pa and a temperature consistent with the local outdoor environment (-5 ℃ to 20 ℃) provided the low-vacuum exposure environment.

Results and discussion

The application of surface coatings significantly reduced the mass loss of concrete under low-vacuum conditions. Compared to uncoated concrete, coated specimens exhibited a noticeably lower mass loss rate, demonstrating that the surface coating effectively suppressed the loss of free water within the concrete.

The surface coating markedly improved the flexural strength of concrete under both atmospheric and low-vacuum conditions. Under atmospheric curing, the flexural strength of coated specimens at 14, 28 d, and 60 d increased by 28.2%, 23.9%, and 36.2%, respectively, compared to uncoated specimens. For coated specimens exposed to a low-vacuum environment after six days of atmospheric curing, flexural strength at 14, 28 d, and 60 d increased by 33.3%, 25.0%, and 15.4%, respectively, compared to uncoated specimens under the same conditions. Furthermore, coated specimens exposed to low vacuum after 28 d of atmospheric curing showed a 47.5% increase in flexural strength compared to uncoated specimens.

In contrast, the compressive strength of coated specimens was generally lower than that of uncoated specimens under both atmospheric and low-vacuum exposure. This reduction is attributed to the adverse effects of low vacuum on the compressive strength of coated specimens. Additionally, the application of surface coatings reduces friction between the concrete specimens and the testing machine, diminishing end effects, which may also contribute to the lower compressive strength observed.

Microstructural analysis using SEM revealed similar hydration products in both coated and uncoated specimens, including ettringite and C-S-H. However, uncoated specimens exhibited more needle-like ettringite and network-like C-S-H, whereas coated specimens showed fewer needle-like structures and more plate-like C-S-H. BSE analysis indicated an 18.1% reduction in porosity for coated specimens under low-vacuum conditions compared to uncoated ones, reflecting improved internal density. Nevertheless, the unhydrated cement content in coated specimens was 7.5% higher than in uncoated specimens, suggesting partial hydration inhibition by the coating.

The adhesion strength of the coating increased with time under both atmospheric and vacuum conditions. Vacuum exposure slightly enhanced the coating's adhesion strength, indicating that low-vacuum environments promote better bonding between the coating layer and the concrete surface over time.

Conclusions

The surface coating effectively mitigated free water loss in low-vacuum environments, resulting in significantly reduced mass loss rates for coated concrete compared to uncoated specimens. Coated specimens demonstrated notable improvements in flexural strength under both atmospheric and low-vacuum conditions, although compressive strength was slightly reduced. Early-age exposure to low vacuum negatively impacted both compressive and flexural strength, regardless of coating protection. Microstructural analysis showed that the coating reduced porosity and enhanced internal density, mitigating the detrimental effects of low-vacuum environments on concrete's internal structure. Over time, the adhesion strength of the coating increased under both atmospheric and vacuum conditions, with slight improvements observed following vacuum exposure.

Key words

concrete / low vacuum environment / coating protection / mass loss / strength

引用本文

程冠之, 林红威, 李咏昊, 庄扬波, 韩松, 韩冰, 李大林. 涂层防护对低真空暴露混凝土性能的影响规律. 硅酸盐学报, 2025 , 53 (5) : 1133 -1143 . DOI: 10.14062/j.issn.0454-5648.20240606

Guanzhi CHENG, Hongwei LIN, Yonghao LI, Yangbo ZHUANG, Song HAN, Bing HAN, Dalin LI. Effects of Surface Coating on Concrete Properties Under Low Vacuum Environment[J]. Journal of the Chinese Ceramic Society, 2025 , 53 (5) : 1133 -1143 . DOI: 10.14062/j.issn.0454-5648.20240606

基金

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中国铁道科学研究院集团有限公司科研基金项目(2022YJ129)
国家自然科学基金(52108109; 52478118; 52478290)

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2025年第53卷第5期

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文章信息

doi: 10.14062/j.issn.0454-5648.20240606

接收时间：2024-09-19
首发时间：2026-10-22
出版时间：2025-05-20

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出版历史

收稿日期：2024-09-19
修回日期：2024-11-12

基金

中国铁道科学研究院集团有限公司科研基金项目(2022YJ129)

国家自然科学基金(52108109; 52478118; 52478290)

作者信息

^1．中国铁道科学研究院集团有限公司铁道建筑研究所，北京 100081

^2．北京交通大学土木建筑工程学院，北京 100044

^3．高速铁路轨道系统全国重点实验室，北京 100081

通讯作者:

林红威（1989—），男，博士，副教授。

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https://castjournals.cast.org.cn/joweb/gsyxb/CN/10.14062/j.issn.0454-5648.20240606

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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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