硅酸盐学报

二氧化碳养护硅酸钙矿物的强度和微观结构

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肖智强 ¹^,²^,³ , 张健 ¹^,²^,³ , 胡翔 ¹^,²^,³ , 史才军 ¹^,²^,³

硅酸盐学报 | 研究论文 2025,53(2): 380-395

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硅酸盐学报 |研究论文 2025 , 53 (2) : 380 -395

二氧化碳养护硅酸钙矿物的强度和微观结构

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肖智强¹^,²^,³, 张健¹^,²^,³, 胡翔¹^,²^,³, 史才军¹^,²^,³

作者信息

^1．湖南大学土木工程学院，绿色先进土木工程材料及应用技术湖南省重点实验室，长沙 410082

^2．湖南省绿色与先进土木工程材料国际创新合作中心，长沙 410082

^3．建筑安全与节能教育部重点实验室，长沙 410082

通讯作者:

史才军（1963—），男，博士，教授。

张健（1991—），男，博士，助理研究员。

作者简介:

肖智强（1999—），男，硕士研究生。

Compressive Strength and Microstructure of CO₂ Cured Calcium Silicate Minerals

Zhiqiang XIAO¹^,²^,³, Jian ZHANG¹^,²^,³, Xiang HU¹^,²^,³, Caijun SHI¹^,²^,³

Affiliations

^1.Key Laboratory for Green & Advanced Civil Engineering Materials and Application Technology of Hunan Province, College of Civil Engineering, Hunan University, Changsha 410082, China

^2.International Science Innovation Collaboration Base for Green & Advanced Civil Engineering Materials of Hunan Province, Changsha 410082, China

^3.Key Laboratory of Building Safety and Energy Efficiency of the Ministry of Education, Changsha 410082, China

Corresponding Author:

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

ZHANG Jian (1991-), male, Ph.D., Research assistant. zhangjianzyf@hnu.edu.cn

XIAO Zhiqiang (1999-), male, Master candidate. E-mail: hudaxzq@hnu.edu.cn

出版时间: 2025-02-20 doi: 10.14062/j.issn.0454-5648.20240141

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摘要

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硅酸钙矿物的碳化是CO₂养护水泥混凝土材料及低钙胶凝材料的理论基础，其碳化程度和碳化产物是影响碳化基体强度和微观结构的关键因素。本工作研究了CO₂养护波特兰水泥、β-C₂S、γ-C₂S、C₃S₂和CS的强度和微观结构，并分析了CO₂养护硅酸钙矿物结构和性能与碳化过程的对应关系。结果表明，经过压制成型（25 MPa压力）和3 d CO₂养护［99.9% CO₂，0.3 MPa，（20±2）℃，相对湿度RH（60±5）%］，β-C₂S和γ-C₂S砂浆试样抗压强度达到50 MPa，其次为水泥和C₃S₂，而碳化CS试样强度仅为11.6 MPa。γ-C₂S、C₃S₂和CS的碳化程度高达60%，β-C₂S为50.3%，水泥碳化程度仅29.7%。γ-C₂S、C₃S₂和CS碳化形成的硅胶聚合度较高，且与碳酸钙存在明显分界；而碳化水泥颗粒外层硅胶与碳酸钙相互交织。CO₂养护硅酸钙矿物的抗压强度与CO₂吸收量和孔隙率呈线性关系。随着Ca/Si摩尔比的升高，CS、C₃S₂和γ-C₂S矿物的CO₂吸收量增加、孔隙率降低，抗压强度升高。水泥与β-C₂S由于水化和碳化的共同作用，基体孔隙率较低，抗压强度较高。此外，方解石晶粒尺寸，无定形碳酸钙含量以及碳酸钙与硅胶的界面性能等也会影响碳化硅酸钙矿物的抗压强度和微观结构演变。

关键词

二氧化碳养护 / 硅酸钙矿物 / 碳化产物 / 微观结构 / 抗压强度

Abstract

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Introduction

CO₂ curing technology has been extensively studied due to its dual benefits of carbon sequestration and enhancement in the properties of cementitious materials. During CO₂ curing, the carbonatable binders react with CO₂ and form carbonation products, such as calcium carbonate and silica gel, leading to matrix densification and rapid strength development. The development of this technology enables the use of low lime calcium silicate minerals, such as wollastonite (CS), rankinite (C₃S₂) and γ-dicalcium silicate (γ-C₂S) with very low hydration reactivity to produce low CO₂ footprint binders through CO₂ curing. The carbonation activity, carbonation products and mechanical properties of the carbonated matrix of calcium silicate minerals have been widely studied. However, the relationship between the mechanical properties and microstructure of carbonated calcium silicate minerals remains unclear, which potentially limits the application of CO₂ cured cement and concrete as well as low-calcium cementitious materials. In this work, the microstructure and mechanical properties of CO₂ cured Portland cement, β-C₂S, γ-C₂S, C₃S₂ and CS were investigated, and the correspondence between the structure and properties of CO₂ cured calcium silicate minerals and the carbonation process was analyzed.

Methods

The raw materials used in this study include Portland cement (PC, PI 42.5), β-dicalcium silicate (β-C₂S), γ-dicalcium silicate (γ-C₂S), rankinite (C₃S₂) and wollastonite (CS). Pastes were prepared with a water-to-binder ratio of 0.18 for microstructural and phase analysis, while mortars were prepared with a constant water-to-binder ratio of 0.25 and sand-to-binder ratio of 2 for mechanical and porosity analysis. Specimens were prepared by compaction molding, with a pressure of approximately 10 MPa for pastes and 25 MPa for mortars. After molding and pre-conditioning, the compact specimens were placed in a pressure chamber. The curing chamber was vacuumed to a pressure of around -0.1 MPa, and maintained for 3 min. After that, CO₂ gas, with a purity of 99%, was injected and maintained at 0.2 MPa at (20 ± 2) ℃ and RH of (60% ±5%) for 3 d.

The carbonation degree of calcium carbonate minerals was determined by a thermal gravimetric analyzer. The phase composition of CO₂ cured calcium silicate minerals was analyzed by XRD analysis, and FTIR spectra were obtained with a Thermo-Scientific IS10 FTIR instrument. Moreover, the microstructure and morphology of paste specimens were examined using Phenom LE SEM. The compressive strength of cylindrical mortar specimens (Φ = 25 mm and h = 25 mm) was tested after CO₂ curing. Meanwhile, the pore structure was tested by a MAG-MED proton nuclear magnetic resonance spectroscopy.

Results and discussion

The carbonation degree of γ-C₂S, C₃S₂ and CS exceeded 60%, followed by 50.3% for β-C₂S, while that of PC was only 29.7%. The lowest carbonation degree of PC was because cement particles release more Ca ions than other minerals during early CO₂ curing, rapidly forming a carbonate shell that blocks further carbonation inside the compacts. The carbonation products of calcium silicate minerals were mainly calcium carbonate and silica gel. Calcite was the main crystalline calcium carbonate, along with minor amounts of aragonite and vaterite. The silica gel phases in CO₂ cured γ-C₂S, C₃S₂ and CS showed higher polymerization degree and exhibited a clear demarcation from calcium carbonate, while the silica gel phases in the outer layer of CO₂ cured PC particles were intermixed with calcium carbonate. This was related to the high hydration reactivity of PC, which could react with water and form a certain amount of hydration products (i.e. C-S-H and portlandite) in the pores. The carbonation of porous C-S-H results in the intermixing of calcium carbonate with silica gel. Additionally, the synergy of cement hydration and carbonation also facilitates the leaching of Ca²⁺, thus leading to an evaluated content of amorphous phases in CO₂ cured PC.

After 3 days of CO₂ curing, the compressive strength of β-C₂S and γ-C₂S mortars exceeded 50 MPa, followed by PC and C₃S₂, while the strength of CO₂ cured CS was only 11.6 MPa. The compressive strength of CO₂ cured calcium silicate minerals showed a linear relationship with CO₂ uptake and porosity, increasing with a decrease in porosity and an increase in CO₂ uptake. With the increase of Ca/Si, the CO₂ uptake of CS, C₃S₂ and γ-C₂S increased, the porosity decreased, and thus the compressive strength increased. However, PC and β-C₂S were subjected to both hydration and carbonation, which promote the formation of amorphous phases, leading to lower porosity and higher compressive strength. Moreover, the crystal size of calcite, the content of amorphous calcium carbonate and the interfacial properties of calcium carbonate and silica gel can also impact the compressive strength and microstructure evolution.

Conclusions

The carbonation products of calcium silicate minerals were mainly calcium carbonate and silica gel. The carbonation degree of non-hydraulic γ-C₂S, C₃S₂ and CS was relatively higher, followed by β-C₂S, while PC demonstrated the lowest carbonation degree. The silica gel phases in CO₂ cured γ-C₂S, C₃S₂ and CS showed higher polymerization degree and exhibited a clear demarcation from calcium carbonate, while the silica gel phases in the outer layer of CO₂ cured Portland cement particles were intermixed with calcium carbonate. The compressive strength of CO₂ cured calcium silicate minerals showed a linear relationship with CO₂ uptake and porosity. With the increase of Ca/Si ratio, the CO₂ uptake of CS, C₃S₂ and γ-C₂S increased, the porosity decreased, and thus the compressive strength increased. Portland cement and β-C₂S were subjected to both hydration and carbonation, leading to lower porosity and higher compressive strength. The smaller size of calcite crystals and the higher content of amorphous calcium carbonate also contribute to an increased mechanical property of CO₂ cured Portland cement.

Key words

carbon dioxide curing / calcium silicate minerals / carbonation products / microstructure / compressive strength

引用本文

肖智强, 张健, 胡翔, 史才军. 二氧化碳养护硅酸钙矿物的强度和微观结构. 硅酸盐学报, 2025 , 53 (2) : 380 -395 . DOI: 10.14062/j.issn.0454-5648.20240141

Zhiqiang XIAO, Jian ZHANG, Xiang HU, Caijun SHI. Compressive Strength and Microstructure of CO₂ Cured Calcium Silicate Minerals[J]. Journal of the Chinese Ceramic Society, 2025 , 53 (2) : 380 -395 . DOI: 10.14062/j.issn.0454-5648.20240141

基金

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国家自然科学基金(52078204)

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2025年第53卷第2期

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文章信息

doi: 10.14062/j.issn.0454-5648.20240141

接收时间：2024-02-23
首发时间：2026-10-22
出版时间：2025-02-20

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收稿日期：2024-02-23
修回日期：2024-03-20

基金

国家自然科学基金(52078204)

作者信息

^1．湖南大学土木工程学院，绿色先进土木工程材料及应用技术湖南省重点实验室，长沙 410082

^2．湖南省绿色与先进土木工程材料国际创新合作中心，长沙 410082

^3．建筑安全与节能教育部重点实验室，长沙 410082

通讯作者:

史才军（1963—），男，博士，教授。

张健（1991—），男，博士，助理研究员。

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https://castjournals.cast.org.cn/joweb/gsyxb/CN/10.14062/j.issn.0454-5648.20240141

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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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