硅酸盐学报

氧化镁对铝酸三钙水化产物和微观形貌影响

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宋强 ¹ , 杨佳辉 ¹ , 周红 ² , 胡亚茹 ¹ , 潘志刚 ³ , 陈延信 ¹ , 程福安 ¹

硅酸盐学报 | 研究论文 2025,53(11): 3158-3167

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硅酸盐学报 |研究论文 2025 , 53 (11) : 3158 -3167

氧化镁对铝酸三钙水化产物和微观形貌影响

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宋强¹, 杨佳辉¹, 周红², 胡亚茹¹, 潘志刚³, 陈延信¹, 程福安¹

作者信息

^1．西安建筑科技大学材料科学与工程学院，西安 710055

^2．陕西建材科技集团股份有限公司，西安 710018

^3．南京工业大学材料科学与工程学院，南京 210009

通讯作者:

陈延信（1974—），男，博士，教授。

作者简介:

宋强（1980—），男，博士，副教授。

Effect of MgO on Hydration Products and Micro-Morphology of C₃A

Qiang SONG¹, Jiahui YANG¹, Hong ZHOU², Yaru HU¹, Zhigang PAN³, Yanxin CHEN¹, Fuan CHENG¹

Affiliations

^1.College of Materials Science and Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China

^2.Shaanxi Building Materials Technology Group Co., Ltd., Xi'an 710018, China

^3.College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009, China

Corresponding Author:

CHEN Yanxin (1974-), male, Ph.D., Professor. E-mail: yx_ch@126.com

SONG Qiang (1980-), male, Ph.D., Associate Professor. E-mail: sqxauat@126.com

出版时间: 2025-11-20 doi: 10.14062/j.issn.0454-5648.20250390

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摘要

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水泥浆体中的镁铝水滑石（Mg-Al LDH）具有优异的阴离子结合能力，探究高镁硅酸盐水泥中Mg-Al LDH的形成路径及养护温度对含镁C₃A水化产物影响规律，对于降低高镁硅酸盐水泥中方镁石水化膨胀，改善混凝土抗离子侵蚀能力有理论价值。通过无石膏条件下C₃A-MgO复合物的水化实验，分析了20 ℃和50 ℃养护温度下水化产物组成、微观形貌及元素分布特征。结果表明：20 ℃下，水化6 h即有少量Mg-Al LDH形成；提高养护温度到50 ℃加速了方镁石Mg²⁺的释放，使LDH在7 d后成为主要水化产物，且伴随着Mg/Al比从2.77降至2.21。Mg²⁺促使C₃AH₆表面溶解并生长板状/薄片状Mg-Al LDH：20 ℃养护形成的LDH呈规则六方片状（Mg/Al比=2.77~3.16），50 ℃下LDH边缘不规则且Mg/Al比降低。20 ℃和50 ℃养护样品的水化产物中形成包含Ca-Mg-Al的新水合物，50 ℃养护的样品中，该水合物出现的时间更早，其形成依赖于C₃AH₆、Mg-Al LDH与Ca（OH）₂的共同反应。该新相具有热致可逆相变特性。能谱证实新相其表面组成接近CaMgAl（OH）₇，板层内部的Ca/Mg比存在一定的线性关系。

关键词

氧化镁 / 铝酸三钙 / 水化 / 镁铝水滑石 / 新相

Abstract

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Introduction

Magnesium oxide (MgO) content in Portland cement clinker critically influences clinkering and long-term soundness. Limited MgO(≤2%, mass fraction) optimizes mineral formation by reducing liquid-phase viscosity during sintering, but excessive MgO forms low-reactivity periclase. Delayed hydration of periclase to brucite (Mg(OH)₂) causes destructive expansion. Thermodynamically, Mg²⁺ can react with Al³⁺ from C₃A/C₄AF to form magnesium-aluminum layered double hydroxide (Mg-Al LDH), which offers superior anion binding capacity. However, kinetic competition with formation of AFt(ettringite)/AFm(monosulfate) phases in sulfate-rich systems often suppresses LDH formation. This study investigates the formation pathway of Mg-Al LDH and the role of temperature in MgO-doped C₃A hydration (without sulfate), revealing novel Ca-Mg-Al hydrates(X-phase) and microstructural evolution mechanisms.

Methods

MgO was obtained by calcining basic magnesium carbonate (900 ℃, 2 h). C₃A-MgO composites (40 g MgO to 100 g C₃A) were synthesized from CaCO₃/Al₂O₃ mixtures (Ca/Al=3∶2), sintered at 1450 ℃ for 3 h, and air-quenched. XRD-Rietveld analysis quantified phases: 69.70% cubic C₃A, 25.09% periclase, 3.58% C₁₂A₇, and 1.63% free CaO. Hydration suspensions (w/s=10∶1, under N₂ atmosphere) were cured at 20 ℃ and 50 ℃ for 1 h-120 d. Hydration was stopped with isopropanol; solids were filtered, vacuum-dried (40 ℃), and characterized. Phase evolution was analyzed via XRD (Rietveld refinement) and in-situ high-temperature XRD (25-200 ℃). Morphology and elemental distribution were examined using FIB-SEM (Helios 5 UC) and EDS (Oxford UltimMax65). Platy particles were cross-sectioned by FIB etching (500 nm-2 μm depths) for compositional profiling.

Results and Discussion

At 20 ℃, C₃AH₆ forms rapidly, constituting 50% of solids within 1 h, and C₃A is fully consumed by 3 d. Mg-Al LDH emerges after 6 h, grows gradually to 45% and with approximately 7% periclase residue at 56 d. XRD analysis reveals a novel X-phase at 28 d, characterized by distinct diffraction peaks at 6.70° and 13.38° 2θ. In contrast, at 50 ℃, accelerated dissolution of periclase enables complete hydrolysis of MgO by 28 d. Mg-Al LDH dominates the system after 7 d, reaching 54% at 56 d and replacing C₃AH₆ as the primary phase. The X-phase forms within just 1 h and consistently increases with prolonged curing.

The morphology and composition of Mg-Al LDH exhibit significant temperature dependence. At 20 ℃, LDH crystallizes as well-defined hexagonal sheet with Mg/Al ratios ranging from 2.77 to 3.16 (EDS data). SEM images and EDS confirmed C₃AH₆ dissolution is driven by Mg²⁺, and Al³⁺ originated from C₃AH₆ supports Al³⁺ for LDH growth. At 50 ℃, however, LDH shows irregularly shaped flake with a lower, more homogeneous Mg/Al ratio (2.21 ± 0.11). This decrease of Mg/Al ratio suggests enhanced Al³⁺ availability from C₃AH₆ at elevated temperatures.

The formation pathway of the X-phase involves a three-component reaction: C₃AH₆+Mg₄Al₂(OH)₁₄·3H₂O+CH→X. X-phase early appearance at 50 ℃ (1 h vs. 28 d at 20℃) confirms temperature-dependent kinetics. In situ high-temperature XRD indicates its structural reversibility: heating above 50 ℃ induces peak shifts (e.g., new peaks at 8.82° and 10.64° 2θ), yet cooling restores the original pattern, confirming thermally reversible structure. EDS of X-phase surface identifies composition of CaMgAl(OH)₇. FIB-EDS cross-sectional profiling exposes a linear Ca/Mg ratio within X-phase inner lamellae (slope = -0.46), implying continuous Mg²⁺ substitution for Ca²⁺ during maturation. Under curing at 50 ℃ for 120 d, platy X-phase particles evolve into stacked lamellar up to 20 μm width and 2 μm thickness. These particles encapsulate residual C₃AH₆, demonstrating the role of C₃AH₆ as reactants.

Conclusions

Elevating curing temperature from 20 ℃ to 50 ℃ accelerates periclase dissolution, enabling Mg-Al LDH to dominate C₃A hydration after 7 d and reducing its Mg/Al ratio from 2.77 to 2.21. Mg²⁺ etches C₃AH₆ surfaces, facilitating LDH growth by the release of Al³⁺. A novel Ca-Mg-Al hydrate (X-phase) forms through reactions of C₃AH₆, Mg-Al LDH, and Ca(OH)₂, exhibiting thermally reversible phase transitions and a composition of this phase surface near CaMgAl(OH)₇. Internal Ca/Mg ratio within X-phase lamellar particles suggests ion exchange during maturation.

Key words

magnesium oxide / tricalcium aluminate / hydration / Mg-Al layered double hydroxide / new phase

引用本文

宋强, 杨佳辉, 周红, 胡亚茹, 潘志刚, 陈延信, 程福安. 氧化镁对铝酸三钙水化产物和微观形貌影响. 硅酸盐学报, 2025 , 53 (11) : 3158 -3167 . DOI: 10.14062/j.issn.0454-5648.20250390

Qiang SONG, Jiahui YANG, Hong ZHOU, Yaru HU, Zhigang PAN, Yanxin CHEN, Fuan CHENG. Effect of MgO on Hydration Products and Micro-Morphology of C₃A[J]. Journal of the Chinese Ceramic Society, 2025 , 53 (11) : 3158 -3167 . DOI: 10.14062/j.issn.0454-5648.20250390

基金

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陕西省科学技术研究计划(2024GX-YBXM-401; 2024GX-YBXM-370)
榆林市科技计划项目(CXY-2020-057)

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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.0454-5648.20250390

接收时间：2025-05-16
首发时间：2026-10-21
出版时间：2025-11-20

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收稿日期：2025-05-16
修回日期：2025-06-20

基金

陕西省科学技术研究计划(2024GX-YBXM-401; 2024GX-YBXM-370)

榆林市科技计划项目(CXY-2020-057)

作者信息

^1．西安建筑科技大学材料科学与工程学院，西安 710055

^2．陕西建材科技集团股份有限公司，西安 710018

^3．南京工业大学材料科学与工程学院，南京 210009

通讯作者:

陈延信（1974—），男，博士，教授。

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https://castjournals.cast.org.cn/joweb/gsyxb/CN/10.14062/j.issn.0454-5648.20250390

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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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