硅酸盐学报

活性氧化镁对碱激发矿渣水泥的水化和微观结构演变的影响

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徐艳娟 ¹^,³^,⁴ , 李水生 ² , 张健 ¹^,³^,⁴ , Talha Ghafoor MUHAMMAD ¹^,³^,⁴ , 胡翔 ¹^,²^,³ , 史才军 ¹^,³^,⁴

硅酸盐学报 | 研究论文 2025,53(11): 3136-3157

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硅酸盐学报 |研究论文 2025 , 53 (11) : 3136 -3157

活性氧化镁对碱激发矿渣水泥的水化和微观结构演变的影响

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徐艳娟¹^,³^,⁴, 李水生², 张健¹^,³^,⁴, Talha Ghafoor MUHAMMAD¹^,³^,⁴, 胡翔¹^,²^,³, 史才军¹^,³^,⁴

作者信息

^1．湖南大学，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．中国建筑第五工程局有限公司，长沙 410004

^3．湖南大学，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

^4．湖南大学，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。

作者简介:

徐艳娟（1999—），女，硕士研究生。

Effect of Active Magnesium Oxide on Hydration and Microstructure Development of Alkali-Activated Slag Cement

Yanjuan XU¹^,³^,⁴, Shuisheng LI², Jian ZHANG¹^,³^,⁴, Talha Ghafoor MUHAMMAD¹^,³^,⁴, Xiang HU¹^,²^,³, Caijun SHI¹^,³^,⁴

Affiliations

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

^2.China Construction Fifth Engineering Division Co., Ltd., Changsha 410004, China

^3.International Innovation and Cooperation Center for Green & Advanced Civil Engineering Materials of Hunan Province, Hunan University, Changsha 410082, China

^4.Key Laboratory of Building Safety & Energy Conservation, Ministry of Education, Changsha 410082, China

Corresponding Author:

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

XU Yanjuan (1999-), female, Master candidate. E-mail: 2547836088@qq.com

出版时间: 2025-11-20 doi: 10.14062/j.issn.0454-5648.20250139

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摘要

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碱激发矿渣（AAS）材料因凝结硬化速度快、体积收缩大及易开裂等固有缺陷，严重制约了其工程应用。采用活性氧化镁（MgO）作为改性剂，系统研究了其对AAS的水化、硬化过程及微观结构的调控机制。结果表明：MgO通过吸收体系自由水显著降低新拌浆体流动度。其初始水化产物Mg（OH）₂在高碱度环境下溶解度极低，可在矿渣颗粒表面形成钝化膜，有效延缓矿渣溶解，从而延长凝结时间。随着水化反应进行，体系pH值降低促使Mg（OH）₂溶解度升高，解离产生的Mg²⁺和OH^-呈现协同效应：一方面通过提高液相碱度加速矿渣溶解；另一方面与溶出的［SiO₄］^4-和［Al（OH）₄］^-反应，生成二次水化产物M-S-H凝胶和镁铝水滑石（Ht），显著提升早期抗压强度。其中，当高活性MgO掺量为8%时，8 h强度增幅最大，达38.82%。然而，过量Mg²⁺会与Ca²⁺竞争消耗［SiO₄］^4-和［Al（OH）₄］^-，不仅抑制C-（A）-S-H凝胶的结晶生长，还降低其铝含量，导致凝胶结构疏松化，致使后期强度发展受限。基于Krstulovic-Dabic水化动力学模型分析发现，MgO掺入使晶体成核与生长（NG）阶段反应速率提升，但扩散控制（D）阶段反应速率因产物层覆盖效应而降低。值得注意的是，尽管反应动力学参数发生变化，体系总水化热仍随MgO活性及掺量呈正相关，这与含镁产物（Mg（OH）₂、Ht、M-S-H凝胶等）的持续生成密切相关。本研究为优化AAS的凝结时间，平衡早期强度与长期强度发展提供了理论依据。

关键词

碱激发矿渣 / 活性氧化镁 / 水化动力学 / 微观结构 / 力学性能

Abstract

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Introduction

Alkali-activated slag (AAS) is a cementitious material prepared by using blast furnace slag as the precursor, triggered by alkaline activators to undergo dissolution, polycondensation, and solidification reactions. Compared to traditional cement-based materials, inherent defects of AAS, such as rapid setting and hardening, significant volumetric shrinkage, and susceptibility to cracking, severely limit its engineering applications. The hydration of magnesium oxide (MgO) generates magnesium hydroxide, with a solid-phase volume expansion of approximately 118%, which effectively compensates for the volumetric shrinkage caused by AAS hydration. However, existing studies are predominantly confined to single-dimensional analyses, such as the impact of MgO reactivity and content, fixed activator parameters, or specific curing ages on isolated performance, lacking systematic investigation into the coupling effects of multiple factors, microstructural evolution, and macro-performance development. This paper systematically investigates the regulatory mechanisms of MgO as a modifier on the hydration kinetics, hardening behavior, and microstructure evolution of AAS.

Methods

The precursor used in this experiment was slag with a specific surface area of 426 m²/kg. The alkaline activator was liquid sodium silicate which adjusted to a modulus of 1.5 using sodium hydroxide and deionized water. The sand employed was ISO standard sand. The additives included high-reactivity HR-MgO (reactivity time: ~20 s) and medium-reactivity MR-MgO (reactivity time: 70~90 s). The experimental parameters were set as follows: alkali content (Na₂O as a mass percentage of slag) = 6%, modulus (Ms = SiO₂/Na₂O molar ratio) = 1.5, water-to-solid ratio (including water in the activator and mixing water) = 0.4, and MgO dosage (as a mass percentage of slag) = 0%, 4%, 8%, and 12%. The specimens were molded at room temperature, demolded after resting for 6 h, and then cured under sealed conditions at a temperature of (20 ± 2) ℃ and relative humidity ≥ 95% until the specified curing age. The flowability, setting time, hydration heat, compressive strength, TG, XRD, FTIR, and SEM tests were conducted.

Results and discussion

During hydration, MgO consumes partial free water, significantly reducing the fluidity of AAS mortar, with the fluidity loss intensifying as MgO reactivity and dosage increase. Concurrently, MgO incorporation prolongs the setting time of AAS paste, particularly with HR-MgO exhibiting stronger retardation effects. This phenomenon primarily arises from the formation of a passivation layer—composed of Mg(OH)₂ and M-S-H gel generated via MgO hydration—on slag particle surfaces, which inhibits further slag dissolution and thus delays setting. Moderate MgO content enhances the early hydration exothermic rate of AAS, shortening the duration of the induction period, with MR-MgO exhibiting superior enhancement effects compared to HR-MgO. While MgO minimally impacts the peak exothermic rate during the acceleration stage, it significantly increases cumulative heat release over 72 h. For instance, the HR-12 group achieved 178.84 kJ/kg, representing a 13.8% improvement over the control group. This indicates that MgO synergistically promotes hydration by accelerating slag dissolution and ion exchange processes, though excessive dosage diminishes early activation efficiency. MgO incorporation improves the early compressive strength of AAS. The HR-8 group attained a maximum 8 h compressive strength of 51.76 MPa, representing a 38.82% increase compared to the control group. However, strength growth in MgO-doped samples lags behind the control group at later ages, with 28 d compressive strength decreasing as MgO reactivity and dosage increase. MgO incorporation reduces the geometric crystal growth index (n) during the nucleation and growth (NG) stage, shifting hydration from homogeneous to heterogeneous nucleation. This accelerates crystal nucleation/growth rates, enabling earlier transition to the phase boundary reaction (I) stage. During Stage I, the synergistic interaction between MgO's secondary reactions and slag particle phase boundary reaction dominates hydration kinetics, causing actual exothermic curves to deviate upward from fitted curves and resulting in reduced curve fitting accuracy. As hydration progresses, the hydration product layer gradually covers slag particles, inhibiting ion diffusion and thereby reducing reaction rates during the diffusion-controlled (D) stage. Additionally, MgO alters AAS hydration product composition: M-S-H gel (with lower hydration heat than C-A-S-H gel) further decreases the D-stage reaction rate constant, impacting long-term hydration.

Conclusions

MgO markedly reduces the fluidity of fresh paste through free water absorption. During the initial hydration phase, the low solubility of Mg (OH)₂ under high alkalinity enables the formation of a passivation layer on slag particles, effectively delaying slag dissolution and prolonging setting time. As hydration progresses, pH reduction enhances Mg(OH)₂ solubility, releasing Mg²⁺ and OH^- ions that exhibit synergistic effects: 1) Elevated alkalinity accelerates slag dissolution; 2) Mg²⁺ reacts with dissolved [SiO₄]^4- and [Al(OH)₄]^- to generate secondary hydration products (M-S-H gel and hydrotalcite, Ht), substantially improving early compressive strength (8 h strength increased by up to 38.82% with MgO content of 8%). However, excessive Mg²⁺ competitively consumes [SiO₄]^4- and [Al(OH)₄]^- with Ca²⁺, suppressing the crystallinity of C-(A)-S-H gels and reducing their aluminum substitution, ultimately leading to structural loosening and compromised long-term strength development (28 d strength reduction up to 15.99%). Krstulovic-Dabic hydration kinetic modeling demonstrates that MgO incorporation enhances the nucleation and crystal growth (NG) rate but hinders the diffusion-controlled (D) stage by forming a shielding product layer. Notably, the total hydration heat exhibits positive correlation with MgO reactivity and dosage, attributed to continuous formation of magnesium-bearing phases (Mg (OH)₂, Ht, M-S-H). This work provides theoretical insights for optimizing AAS formulations to balance setting regulation, early strength enhancement, and long-term strength sustainability.

Key words

alkali-activated slag / active magnesium oxide / hydration process / microstructure / mechanical property

引用本文

徐艳娟, 李水生, 张健, Talha Ghafoor MUHAMMAD, 胡翔, 史才军. 活性氧化镁对碱激发矿渣水泥的水化和微观结构演变的影响. 硅酸盐学报, 2025 , 53 (11) : 3136 -3157 . DOI: 10.14062/j.issn.0454-5648.20250139

Yanjuan XU, Shuisheng LI, Jian ZHANG, Talha Ghafoor MUHAMMAD, Xiang HU, Caijun SHI. Effect of Active Magnesium Oxide on Hydration and Microstructure Development of Alkali-Activated Slag Cement[J]. Journal of the Chinese Ceramic Society, 2025 , 53 (11) : 3136 -3157 . DOI: 10.14062/j.issn.0454-5648.20250139

基金

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国家自然科学基金(52278257)
中国建筑土木工程材料重点实验室开放基金(CECEC-PT-002)

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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.0454-5648.20250139

接收时间：2025-03-04
首发时间：2026-10-21
出版时间：2025-11-20

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出版历史

收稿日期：2025-03-04
修回日期：2025-03-18

基金

国家自然科学基金(52278257)

中国建筑土木工程材料重点实验室开放基金(CECEC-PT-002)

作者信息

^1．湖南大学，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．中国建筑第五工程局有限公司，长沙 410004

^3．湖南大学，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

^4．湖南大学，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。

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https://castjournals.cast.org.cn/joweb/gsyxb/CN/10.14062/j.issn.0454-5648.20250139

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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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