匹配养护下氧化镁膨胀剂对砂浆性能和微观结构的影响

doi:10.16552/j.cnki.issn1001-1625.2025.0068

摘要/Abstract

摘要： 为研究氧化镁膨胀剂(MEA)在封闭且变温的服役环境中对钢混结构核心混凝土的影响,通过设立匹配养护机制,探讨了不同活性MEA对砂浆宏观性能和微观结构的影响。研究结果表明,掺入MEA会导致砂浆的扩展度和力学性能下降。其中,高活性MEA对砂浆扩展度的负面影响最为明显,而低活性MEA对砂浆力学性能的负面影响最为显著。同时,中高活性MEA在水化初期和中期能够生成大量的氢氧化镁(Mg(OH)₂)晶体,这些晶体通过原位生长或迁移至水泥水化产物表面,有效减小了累计孔体积,优化了孔隙结构并提高了结构密实度,从而使MEA表现出良好的补偿收缩行为。相比之下,低活性MEA的反应较慢且反应程度较低,生成的Mg(OH)₂晶体数量有限,对砂浆体积收缩的补偿效果较弱。

关键词: 氧化镁膨胀剂, 扩展度, 力学性能, 体积稳定性, 微观结构

Abstract: To investigate the effects of MgO expansive agents (MEA) on core concrete of steel-concrete structures in closed and variable-temperature service environment, this study examined the influences of different active MEA on the macroscopic properties and microstructure of mortar under matched curing condition. The results indicate that the incorporation of MEA reduces both the slump flow and mechanical properties of mortar. In specific, high-activity MEA exhibit the greatest negative impact on the slump flow of mortar, while low-activity MEA notably affect the mechanical properties of mortar. Moreover, medium-activity MEA and high-activity MEA can generate a large quantity of Mg(OH)₂ crystals during the early and middle stages of hydration. These crystals exhibit effective shrinkage compensation by growing in situ or migrating to the surface of the cement hydration products, thereby reducing the cumulative pore volume, optimizing the pore structure, and enhancing the structural compactness. In contrast, the reaction rate and degree of low-activity MEA are slower than those of high-activity MEA. As a result, fewer Mg(OH)₂ crystals are generated, leading to a weaker compensation for the volume shrinkage of the mortar.

Key words: MgO expansive agent, slump flow, mechanical property, volume stability, microstructure

中图分类号:

TU528

白敏, 龙勇, 黄旺明, 胡雄伟, 郭蒙. 匹配养护下氧化镁膨胀剂对砂浆性能和微观结构的影响[J]. 硅酸盐通报, 2025, 44(8): 2781-2789.

BAI Min, LONG Yong, HUANG Wangming, HU Xiongwei, GUO Meng. Effects of MgO Expansive Agents on Properties and Microstructure of Mortar under Matched Curing Condition[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2025, 44(8): 2781-2789.

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