硅酸盐学报

热湿环境下CO₂-SO₂耦合侵蚀水泥基材料的中性化机理及预测模型

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牛荻涛 ¹^,² , 曹志远 ¹ , 吕瑶 ¹

硅酸盐学报 | 研究论文 2024,52(2): 545-554

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硅酸盐学报 |研究论文 2024 , 52 (2) : 545 -554

热湿环境下CO₂-SO₂耦合侵蚀水泥基材料的中性化机理及预测模型

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牛荻涛¹^,², 曹志远¹, 吕瑶¹

作者信息

^1．西安建筑科技大学土木工程学院，西安 710055

^2．省部共建绿色建筑国家重点实验室/西安建筑科技大学，西安 710055

作者简介:

牛荻涛（1963—），男，博士，教授。

Neutralization Mechanism and Prediction Model of CO₂-SO₂ Coupled Erosion of Cement-Based Materials in Hot and Wet Environment

Ditao NIU¹^,², Zhiyuan CAO¹, Yao LV¹

Affiliations

^1.School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China

^2.State Key Laboratory of Green Building in Western China, Xi'an University of Architecture and Technology, Xi'an 710055, China

NIU Ditao (1963-), male, Ph.D., Professor. E-mail: niuditao@163.com

出版时间: 2024-02-20 doi: 10.14062/j.issn.0454-5648.20230527

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摘要

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为探究工业环境中水泥基材料耐久性损伤机理，开展了热湿环境CO₂-SO₂耦合侵蚀下净浆、砂浆和混凝土的中性化试验，并采用核磁共振和电化学阻抗谱等测试方法分析了水泥基材料的孔结构及孔溶液变化，建立了水泥基材料的中性化深度预测模型。结果表明：腐蚀循环前期（0~2次），反应以碳化为主。中期（2~7次），由于CaCO₃填充试样的孔隙，使得碳化反应速率减缓。同时SO₂与混凝土水化产物发生反应，水化硅酸钙（C-S-H）凝胶脱钙，同时生含结晶水的膨胀产物CaSO₃和CaSO₄，导致有害孔逐渐增加，试样表层产生膨胀裂缝。后期（7~14次），SO₂持续腐蚀C-S-H凝胶等水化产物，混凝土孔隙率增大，碳化反应速度加快。

关键词

工业环境 / 水泥基材料 / 中性化机理 / 中性化深度 / 预测模型

Abstract

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Introduction

Although different experiments on the co-corrosion of concrete vulcanization and carbonation are performed, the data are scattered and are not systematic. There are little reports on the mechanism of the performance degradation of cement-based materials due to the coupled effects of high temperature, high humidity, SO₂ and CO₂. It is thus of a great theoretical and practical significance to scientifically evaluate the durability of industrial building concrete structures and investigate the durability damage mechanism and performance degradation of industrial building concrete structures.

In this paper, the neutralization process of cement-based materials under the coupling action of high temperature, high humidity, SO₂ and CO₂ was investigated with the three levels of cement paste, mortar and concrete. The appearance, neutralization depth, and quality change rules of cement-based materials with different water-cement ratios were analyzed. The porosity and pore solution of cement-based materials were determined by nuclear magnetic resonance (NMR) and electrochemical impedance (EIS). In addition, the neutralization mechanism of cement-based materials was discussed, and a prediction model for the neutralization depth of cement-based materials was also established.

Methods

The cement used was P.O 42.5. The fine aggregate was a natural river sand with a fineness modulus of 2.34, and the coarse aggregate was a granite crushed stone with a continuous gradation of 5-25 mm. Three types of samples were cement paste, mortar, and concrete. In the test, a prism-shaped sample of 100 mm×100 mm×400 mm was used to test the neutralization depth of the sample, and a cubic sample of 100 mm×100 mm×100 mm was used for quality and microscopic tests, with 3 samples in each group. The tests began after 28 d of standard curing of the samples.

A concentration ratio of CO₂ and SO₂ in the workshop was approximately 20∶1, and the temperature and humidity were at 50 ℃ and 70%, respectively. The rapid carbonation test method based on the Chinese National Standard GB/T50082—2009 was used. The ambient temperature of the vulcanization test box was 50 ℃, the relative humidity was 70%, and the SO₂ concentration was 0.9% (the maximum concentration of SO₂ in this test box was 0.9% due to the limit of the SO₂ sensor). For the carbonization box, the ambient temperature was 50 ℃, the relative humidity was 70%, and the CO₂ concentration was 20%. The samples were covered with epoxy, leaving only two sides. The sample was placed on a bracket in the vulcanization box, and the distance between each sample was not less than 50 mm. The sample was vulcanized for 1 d and carbonized for 1 d as one cycle. The samples were tested when the cycles reached 0, 2, 4, 7 and 14. The appearance, quality and neutralization depth of cement-based materials were examined. The pore characteristics and pore solution changes in the samples before and after corrosion cycles were analyzed by NMR and EIS.

Results and discussion

Based on the analysis of cement slurry, mortar, and concrete samples, the neutral depth of cement pure pulp is the largest, and the neutral depth after 14 cycles is approximately 35 mm. The neutral depth of the mortar sample after 14 cycles is approximately 13 mm. The overall neutralization depth of the concrete is the smallest, and the difference is not large. The neutral depths after 14 cycles are 6.42, 6.95 mm and 8.19 mm, respectively. The depth of the neutral depth of the ingredients on the cement base is obvious. The aggregate can reduce gas transmission in the sample. The maximum neutral depth of mortar and concrete is decreased by 59.85% and 77.52%, respectively, compared with cement paste.

The pore rate for paste is increased by approximately 3%. For mortar, the pores increase slowly. After 7 cycles, the pore rate is increased rapidly by approximately 8%. For concrete, the pores decrease first and then increase slowly by approximately 1%. For different materials under the common action of carbonization and vulcanization, the pore rate of cement base materials is generally increased.

The initial proportion of harmful pores in concrete is larger than that in paste and mortar. However, the increase in harmful pores in mortar and cement paste is significantly larger than that in concrete as corrosion cycle increases. The harmful pores of concrete increase slowly, and the harmful pores decrease significantly after the 14th cycle. Concrete harmful pores are increased by approximately 0.4%. The harmful pores of the mortar are increased by approximately 0.8%. The harmful pores of the cement paste are increased by approximately 0.6%.

Conclusions

In the early stage of the corrosion cycle, the concentration of CO₂ was relatively high, and the reaction was mainly carbonization. In the middle of the corrosion cycle, CaCO₃ filled in the pores of the sample so that the reaction slowed down and the mass increased slowly. SO₂ could react with calcium-containing substances, resulting in expansion cracks. SO₂ could also lead to decalcification of CSH, further increasing the porosity and accelerating the transmission of gas inside the sample. In the later stage, the carbonization reaction speed accelerated, and the sample mass began to increase again. The neutralization depth of different samples changed approximately in the same manner, i.e., firstly increasing rapidly and then increasing slowly as the number of corrosion cycle increases. The porosity changes in the sample at all levels were similar, and the less harmful pores gradually increased and decreased after 14 cycles. For harmful holes and more harmful holes, the cement paste and mortar samples increased gradually, while the concrete samples firstly increased and then decreased after 14 cycles.

Key words

industrial environment / cement-based materials / neutralization mechanism / neutralization depth / prediction model

引用本文

牛荻涛, 曹志远, 吕瑶. 热湿环境下CO₂-SO₂耦合侵蚀水泥基材料的中性化机理及预测模型. 硅酸盐学报, 2024 , 52 (2) : 545 -554 . DOI: 10.14062/j.issn.0454-5648.20230527

Ditao NIU, Zhiyuan CAO, Yao LV. Neutralization Mechanism and Prediction Model of CO₂-SO₂ Coupled Erosion of Cement-Based Materials in Hot and Wet Environment[J]. Journal of the Chinese Ceramic Society, 2024 , 52 (2) : 545 -554 . DOI: 10.14062/j.issn.0454-5648.20230527

基金

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国家自然科学基金(52078413; 51808437)
教育部“创新团队发展计划”(IRT_17R84)

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2024年第52卷第2期

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文章信息

doi: 10.14062/j.issn.0454-5648.20230527

接收时间：2023-07-24
首发时间：2026-10-22
出版时间：2024-02-20

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出版历史

收稿日期：2023-07-24
修回日期：2023-08-26

基金

国家自然科学基金(52078413; 51808437)

教育部“创新团队发展计划”(IRT_17R84)

作者信息

^1．西安建筑科技大学土木工程学院，西安 710055

^2．省部共建绿色建筑国家重点实验室/西安建筑科技大学，西安 710055

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https://castjournals.cast.org.cn/joweb/gsyxb/CN/10.14062/j.issn.0454-5648.20230527

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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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