Effects of MgO Expansive Agents on Properties and Microstructure of  Mortar under Matched Curing Condition

doi:10.16552/j.cnki.issn1001-1625.2025.0068

Abstract

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

CLC Number:

TU528

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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Effects of MgO Expansive Agents on Properties and Microstructure of Mortar under Matched Curing Condition

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