硅酸盐学报

低压环境对引气混凝土气孔结构及抗冻耐久性影响

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李雪峰 ¹^,² , 张佳晖 ³

硅酸盐学报 | 研究论文 2025,53(5): 1088-1097

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硅酸盐学报 |研究论文 2025 , 53 (5) : 1088 -1097

低压环境对引气混凝土气孔结构及抗冻耐久性影响

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李雪峰¹^,², 张佳晖³

作者信息

^1．交通运输部公路科学研究院，北京 100088

^2．桥梁结构安全技术国家工程实验室，北京 100088

^3．哈尔滨工业大学经济与管理学院，哈尔滨 150006

作者简介:

李雪峰（1983—），男，博士，副研究员。

Influence of Low Atmospheric Pressure on Air Void Structure and Frost Resistance Durability of Air-entrained Concrete

Xuefeng LI¹^,², Jiahui ZHANG³

Affiliations

^1.Research Institute of Highway Ministry of Transport, Beijing 100088, China

^2.National Engineering Laboratory for Bridge Structure Safety Technology, Beijing 100088, China

^3.School of Management Harbin Institute of Technology, Harbin Institute of Technology, Harbin 150006, China

LI Xuefeng (1983-), male, Ph.D., Associate Professor. E-mail: lxfsure@163.com

出版时间: 2025-05-20 doi: 10.14062/j.issn.0454-5648.20240469

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摘要

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为明晰低压环境对引气混凝土中各直径气孔分布的影响规律，并进一步探明其对引气混凝土气孔结构及抗冻耐久性能的劣化效应。对不同气压环境下引气混凝土的含气量、气孔结构参数及抗冻耐久性指数进行测试，研究分析低压环境对引气混凝土气孔结构及抗冻耐久性能的影响。结果表明：低压环境导致引气混凝土硬化后含气量损失更为明显，且含气量设计水平越高，损失值越大，低压下引气混凝土硬化后含气量平均及最大损失值较常压分别增加约0.5%和0.7%；与同含气量水平常压引气混凝土相比，气压降低导致引气混凝土中“微孔”数量占比及含气量占比均明显降低，其中尤以对直径不大于100 μm的“微孔”影响最为显著，并最终导致低压引气混凝土气孔结构发生劣化，抗冻耐久性能下降；引气混凝土中“微孔”含气量与“截留气孔”含气量占比变化对其气孔间距系数影响最为显著；气孔间距系数随“微孔”含气量特别是A_{（0, 100]}与A（_{100, 200]}占比的增大而减小，随“截留气孔”含气量占比的增加而增大；增大引气混凝土含气量可有效提高其中“微孔”含气量占比，进而有效提升引气混凝土的抗冻耐久性能；在高原严酷冻融环境地区，建议新拌混凝土含气量设计水平最大可较平原常压环境提高约2.0%。

关键词

引气混凝土 / 抗冻耐久性 / 低压环境

Abstract

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Introduction

Due to the distinctive climatic characteristics of the Qinghai-Tibet Plateau, such as an extremely frigid climate and significant diurnal temperature fluctuations, concrete structures in this region necessitate substantial freeze-thaw durability. Presently, one of the most efficacious approaches to enhance the freeze-thaw durability of concrete involves incorporating tiny air bubbles into the mixture through the use of air-entraining agents (AEAs). Nevertheless, researchers have discovered that the low atmospheric pressure (LAP) prevalent on the plateau may result in inadequate air content within air-entrained concrete (AEC). Only a limited number of research findings have confirmed that LAP deteriorates the air-void structure of AEC, with relatively few studies investigating its impact on freeze-thaw durability of AEC. Furthermore, there is limited research on the impact of LAP on the distribution of air-void diameters in AEC. Therefore, the air content, air-void structure parameters and freeze-thaw durability of the AEC prepared under normal atmospheric pressure (NAP) and LAP were examined in this study. The primary focus is to investigate the impact of LAP on the distribution of air-voids with varying diameters, thus to further explore how these influences degrade both the air-voids structure parameters and freeze-thaw resistance durability of AEC.

Methods

Ordinary Portland cement was used in the experiment. The coarse aggregate was crushed stone and the fine aggregate was river sand. In the experiment, two types of AEAs and a high-efficiency superplasticizer were used to produce the AEC. The experiments were conducted in laboratories located in Lhasa, China (atmospheric pressure values of 64 kPa) and Beijing, China (101 kPa). Three air content design levels (D) were used in this study, namely, 3%, 5%, and 7%. Air content tests, air-void analyzing tests and freeze-thaw durability tests were conducted.

Results and discussion

Compared to the AEC-N (AEC prepared under NAP), the LAP resulted in a significant increase in the loss of air content of fresh concrete (A_f), with a greater magnitude observed as D increased. The average and maximum losses in air content of hardened concrete (A_h) for AEC-L (AEC prepared under LAP) were approximately 0.5% and 0.7% higher than those for AEC-N, respectively. Furthermore, due to decreased atmospheric pressure, microvoids within AEC experienced a more substantial decrease with increasing D. Notably, air-voids ranging from 0-100 μm exhibited the most pronounced influence. However, increasing D still effectively enhanced the proportion of microvoids within AEC. The proportion of A₁₀₀₀ (the air content in voids with diameters no greater than 1000 μm, the same below) in A_h showed an overall increasing trend followed by a subsequent decreasing trend as A_h increased, both under LAP and NAP conditions. However, when comparing AEC-N to AEC-L with similar D, the former demonstrated significantly higher proportions of A₁₀₀₀. With similar A_h, the reduction in atmospheric pressure led to a significant decrease in the proportion of microvoids (especially A_(0,100]), a pronounced increase in the proportion of trapped air-voids proportion (A_(1000,4000]), and small changes in the proportion of mesovoids (A_(300,500]) and macrovoids (A_(300,500]) within the AEC. The variation in the proportion of microvoids and trapped air-voids significantly influenced the spacing factor (). Specifically, an increase in the air content of microvoids (particularly A_(0,100]), leads to a decreased in the of concrete. Conversely, an increase in the air contentof trapped air-voids resulted in an increase in the . However, the proportion of air content in the mesovoids and macrovoids was most weakly correlated with the .

Concrete subjected to a plateau environment may experience more severe freeze-thaw conditions. when the water-cement ratio was 0.44, the required A₁₀₀₀ under LAP and NAP was about 3.90% and 2.92%, respectively, for achieving a frost resistance durability factor (F_D) of 100%.

The analysis presented in this study demonstrates that the maximum allowable F_D in concrete under LAP is around 3.93%, whereas under NAP it is 4.73%. Clearly, despite the deterioration of air void structures caused by LAP, as long as the air content introduced by AEAs in AEC reaches a certain threshold level, the frost resistance durability requirements can still be met. It is suggested that while meeting the mechanical performance requirements of AEC design, there should be an increase in the maximum air content level of fresh concrete by approximately 2.0% compared to plain areas. This adjustment aims to ensure that the frost resistance performance of concrete meets the design requirements.

Conclusions

The LAP caused a more pronounced loss in the air content of hardened AEC-L, and the loss increased as the D increased. The average and maximum loss was about 0.5% and 0.7% higher than those under AEC-N, respectively. Compared to the AEC-N with the same D, a decrease in atmospheric pressure resulted in a reduction in the air content of the microvoids within the AEC-L. This effect was particularly pronounced for air-voids with diameters not exceeding 100 μm, and consequently leading to the deterioration of the air-void structures and a reduction in frost resistance performance of the AEC-L. The variation in the proportion of air content in microvoids and trapped air-voids has a significant impact on the of the AEC. The decreases with an increase in the proportion of air content of microvoids, particularly A_(0,100] and A_(100,200], while it increased with an increase in the proportion of air content of trapped air-voids. The increase in the D of the concrete effectively enhanced the air content proportion of microvoids, thereby enhancing the frost resistance durability of concrete. It is recommended that when designing AEC for plateau areas with severe freeze-thaw environments, the D of fresh concrete should be increased by a maximum of approximately 2.0% compared to plain areas.

Key words

air-entrained concrete / frost resistance durability / low atmospheric pressure

引用本文

李雪峰, 张佳晖. 低压环境对引气混凝土气孔结构及抗冻耐久性影响. 硅酸盐学报, 2025 , 53 (5) : 1088 -1097 . DOI: 10.14062/j.issn.0454-5648.20240469

Xuefeng LI, Jiahui ZHANG. Influence of Low Atmospheric Pressure on Air Void Structure and Frost Resistance Durability of Air-entrained Concrete[J]. Journal of the Chinese Ceramic Society, 2025 , 53 (5) : 1088 -1097 . DOI: 10.14062/j.issn.0454-5648.20240469

基金

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新疆自治区科技重大专项(2020A03003-4)
中央科研院所基本科研业务费项目(2018-9026)

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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.0454-5648.20240469

接收时间：2024-07-17
首发时间：2026-10-22
出版时间：2025-05-20

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收稿日期：2024-07-17
修回日期：2024-10-06

基金

新疆自治区科技重大专项(2020A03003-4)

中央科研院所基本科研业务费项目(2018-9026)

作者信息

^1．交通运输部公路科学研究院，北京 100088

^2．桥梁结构安全技术国家工程实验室，北京 100088

^3．哈尔滨工业大学经济与管理学院，哈尔滨 150006

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https://castjournals.cast.org.cn/joweb/gsyxb/CN/10.14062/j.issn.0454-5648.20240469

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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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