硅酸盐学报

早期二氧化碳养护水泥净浆的抗压强度变化和后续水化机理

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宋百姓 ¹^,³^,⁴ , 史才军 ²

硅酸盐学报 | 研究论文 2025,53(11): 3179-3189

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硅酸盐学报 |研究论文 2025 , 53 (11) : 3179 -3189

早期二氧化碳养护水泥净浆的抗压强度变化和后续水化机理

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宋百姓¹^,³^,⁴, 史才军²

作者信息

^1．南华大学土木工程学院，高性能特种混凝土湖南省重点实验室，湖南衡阳 421001，中国

^2．湖南大学土木工程学院，长沙 410082，中国

^3．新加坡国立大学土木与环境工程系，肯特岗 117576，新加坡

^4．中国核工业建设集团公司高性能混凝土重点实验室，湖南衡阳 421001，中国

通讯作者:

史才军（1963—），男，博士，教授。

作者简介:

宋百姓（1987—），男，博士，讲师。

Changes in Compressive Strength and Subsequent Hydration Mechanism of Early CO₂-Cured Cement Paste

Baixing SONG¹^,³^,⁴, Caijun SHI²

Affiliations

^1.Key Laboratory in Special High Performance Concrete of Hunan Province, College of Civil Engineering, University of South China, Hengyang 421001, Hunan, China

^2.College of Civil Engineering, Hunan University, Changsha 410082, China

^3.Department of Civil & Environmental Engineering, National University of Singapore, Kent Ridge 117576, Singapore

^4.Laboratory in High Performance Concrete of China nuclear construction, Hengyang 421001, Hunan, China

Corresponding Author:

SHI Caijun (1963-), male, Ph.D., Professor. E-mail: cshi@hnu.edu.cn

SONG Baixing (1987-), male, Ph.D., Lecturer. E-mail: songbaixing123@163.com

出版时间: 2025-11-20 doi: 10.14062/j.issn.0454-5648.20250267

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摘要

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通过测定早期二氧化碳（CO₂）养护水泥净浆孔溶液的pH值与抗压强度，结合X射线衍射、热重-微分热重、傅里叶变换红外光谱、扫描电子显微镜和压汞等技术分析CO₂养护水泥净浆的后续水化度、物相演变及微观结构，并与水养水泥净浆对比，研究了早期CO₂养护水泥净浆的后续水化特性和抗压强度演变。结果表明：在后续水养过程中，早期CO₂养护水泥净浆的主要反应包括未碳化水泥颗粒的水化及硅胶、富钙硅胶与氢氧化钙的反应；早期CO₂养护水泥净浆的后续水化度低于水养对照组，且后续水化度随水灰比的增大呈下降趋势；早期CO₂养护水泥净浆的抗压强度随后续养护龄期的延长持续增长，但其后期强度增长率随水灰比增大而减小。

关键词

二氧化碳养护 / 抗压强度 / 后续水化 / 微观结构 / 物相演变

Abstract

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Introduction

In recent years, CO₂ curing has attracted increasing attention as it not only enhances the early age strength of cement-based materials but also captures and sequesters CO₂, thus it has been regarded as a new curing method with a broad application prospective for eco-friendly construction materials. Since CO₂ curing generally lasts several hours to several days, there are considerable residual cement clinkers in the cement matrix after CO₂ curing. These un-carbonated cement clinkers will rehydrate once in contact with water. The rehydration products of cement clinkers can recover the pH value of the pore solution, reduce the porosity, and refine the pore size distribution of the cement matrix. Thus, the subsequent hydration of CO₂-cured cementitious materials largely governs the long-term performance of cement-based materials, such as compressive strength and durability. Several researchers have studied the subsequent hydration of CO₂-cured cementitious materials, but their conclusions were contradictory. Some researchers reported that the carbonation products calcite promoted the subsequent hydration of un-carbonated cement clinkers. On the contrary, some researchers reported that CO₂ curing hindered the subsequent hydration of un-carbonated cement clinkers and thus lowered the late compressive strength of cement-based materials. Thus, more studies should be conducted to reveal the subsequent hydration mechanism and strength evolution of early CO₂-cured cement-based materials. In this investigation, the subsequent hydration and compressive strength evolution characteristics of early CO₂-cured cement paste were studied by macro-physical experiments and micro-characterization techniques.

Methods

Ordinary Portland cement P·I 42.5 complying with GB8076—2008, and de-ionized water was used to prepare cement paste samples. The water-cement ratios were 0.3, 0.4, and 0.5, respectively. Two groups of cement paste cubes measuring 20 mm were cast. One group of cement paste samples was subjected to 24 h of early CO₂ curing and subsequent standard curing in saturated lime water. The other group of cement paste cubes was subjected to standard curing in saturated lime water, which served as a reference.

After CO₂ curing, the carbonation depths of cement cubes were determined using phenolphthalein indicator, and CO₂ uptake was determined by thermal gravimetric (TG) analysis. The compressive strength of cement paste was measured at the curing ages of 2, 28 d, and 90 d, respectively. The pore solution was extracted with an expression device for pH value measurement. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were employed to characterize the phase evolution. The amounts of silicate and aluminate hydrates were assessed using thermal gravimetric and differential thermal gravimetric (TG-DTG) analysis. The microscopic characteristics and pore structure were examined by scanning electron microscopy (SEM) and mercury intrusion porometer (MIP) at the curing ages of 2, 28 d, and 90d, respectively.

Results and discussion

Similar to the cement paste subjected to standard curing, the compressive strength of early CO₂-cured cement paste continues increasing as it is cured in lime water after CO₂ curing. Nevertheless, the strength improvement of the latter is lower than the former as the subsequent hydration of the former is less significant. In addition, the strength improvement of early CO₂-cured cement pastes in the lime water decreases with the increase of water-cement ratio. After curing to 28 d in lime water, the pH value of early CO₂-cured cement pastes with water-cement ratios of 0.3, 0.4, and 0.5 recovers to 13.14, 12.41, and 12.33, respectively, which is higher than the threshold of de-passivation.

XRD patterns reveal that the diffraction intensities of tricalcium silicate and dicalcium silicate decrease continuously when the early CO₂-cured cement pastes continue curing to 28 d and 90 d in lime water. However, this decrement is less significant than that of standard-cured cement paste. It indicates that CO₂ curing inhibits the subsequent hydration of un-carbonated cement clinkers. This can be attributed to the fact that the formation of calcium carbonate coating on the surface of cement particles. The FTIR spectra reveal that carbonation products silica gel is reactive towards Ca(OH)₂, and it is completely consumed before the age of 28 d. This is responsible for the absence of Ca(OH)₂ in the XRD patterns of early CO₂-cured cement paste with water-cement ratios of 0.4 and 0.5 at 28 d and 90 d, respectively. TG-DTG results suggest that less silicate and aluminate hydrates are produced in early CO₂-cured cement matrix than in standard-cured cement matrix during subsequent lime water curing, and it decreases with the increase of water-cement ratio as denser calcium carbonate coating on the surface of un-carbonated cement particles.

SEM results show that subsequent lime water curing improves the microstructure of early CO₂-cured cement paste due to precipitation of hydration products, while the improvement is less significant than that of standard-cured cement paste. Subsequent lime water curing decreases the porosity and refines the pore size distribution of early CO₂-cured cement paste. The pore diameter of early CO₂-cured cement paste mainly distributes in the range of 10 nm to 50 nm, both at 28 d and 90 d.

Conclusions

In the course of subsequent lime water curing, the main reactions that occurred in early CO₂-cured cement paste include the hydration of un-carbonated cement particles and the interactions between silica gel, calcium-modified silica and Ca(OH)₂. The subsequent hydration degree of early CO₂-cured cement paste is lower than that of cement paste subjected to standard curing, and it decreases with the increase of water-cement ratio. The compressive strength of CO₂-cured cement pastes continually increases with the prolonging of the subsequent curing period, and the growth rate of late compressive strength decreases with the increase of water-cement ratio.

Key words

carbon dioxide curing / compressive strength / subsequent hydration / microstructure / phase evolution

引用本文

宋百姓, 史才军. 早期二氧化碳养护水泥净浆的抗压强度变化和后续水化机理. 硅酸盐学报, 2025 , 53 (11) : 3179 -3189 . DOI: 10.14062/j.issn.0454-5648.20250267

Baixing SONG, Caijun SHI. Changes in Compressive Strength and Subsequent Hydration Mechanism of Early CO₂-Cured Cement Paste[J]. Journal of the Chinese Ceramic Society, 2025 , 53 (11) : 3179 -3189 . DOI: 10.14062/j.issn.0454-5648.20250267

基金

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湖南省自然科学基金资助项目(2024JJ5333)
湖南省教育厅优秀青年项目(22B0443)

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2025年第53卷第11期

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文章信息

doi: 10.14062/j.issn.0454-5648.20250267

接收时间：2025-04-10
首发时间：2026-10-21
出版时间：2025-11-20

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收稿日期：2025-04-10
修回日期：2025-04-26

基金

湖南省自然科学基金资助项目(2024JJ5333)

湖南省教育厅优秀青年项目(22B0443)

作者信息

^1．南华大学土木工程学院，高性能特种混凝土湖南省重点实验室，湖南衡阳 421001，中国

^2．湖南大学土木工程学院，长沙 410082，中国

^3．新加坡国立大学土木与环境工程系，肯特岗 117576，新加坡

^4．中国核工业建设集团公司高性能混凝土重点实验室，湖南衡阳 421001，中国

通讯作者:

史才军（1963—），男，博士，教授。

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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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