MgO膨胀剂对超高性能混凝土收缩性能的影响

摘要/Abstract

摘要： 为明确MgO膨胀剂(MEA)对超高性能混凝土(UHPC)收缩性能及抗压强度的影响,本文通过抗压强度和自收缩试验来评估不同活性、不同掺量MEA对UHPC的作用效果,并对其作用机理进行分析。结果表明,不同活性的MEA均能有效抑制UHPC的收缩,其中高活性的MEA水化速率相对较大,对UHPC早期的自收缩抑制效果明显。然而,MEA与水泥之间“争水效应”的存在,使得掺加高活性MEA的UHPC的抗压强度较同龄期掺加低活性MEA的UHPC的抗压强度低6%左右。MEA的掺量是影响其减缩效果的重要因素,当MEA掺量超过6%(质量分数)时,受UHPC基体自由水含量的限制导致其膨胀性能不能充分激发,难以进一步提升MEA的膨胀性能。综合考虑MEA对UHPC的收缩性能与力学性能的影响,本文建议选用活性值为220 s、掺量为6%的低活性MEA。

关键词: 氧化镁膨胀剂, 超高性能混凝土, 自收缩, 抗压强度, 水化程度, 膨胀性能

Abstract: To identify the influence of MgO expensive agent (MEA) on the shrinkage performance and compressive strength of ultra-high performance concrete (UHPC), this paper aims to evaluate the effect of MEA with different activity and dosages on the compressive strength and autogenous shrinkage of UHPC and analyze the mechanism. The results show that MEA with different activities effectively inhibits the shrinkage of UHPC. The high activity MEA has a relatively high hydration rate and shows a significant inhibition effect on the early autogenous shrinkage for UHPC. However, the compressive strength of UHPC containing high activity MEA is about 6% lower than that of UHPC with low activity MEA due to the existence of the water contention effect between MEA and cement. The content of MEA is an important factor affecting the shrinkage reduction effect. When the content of MEA exceeds 6% (mass fraction), the expansion performance of UHPC cannot be fully stimulated due to the limitation of the free water content in the UHPC matrix, and it is difficult to further improve the expansion performance of MEA considering the influence of MEA on the shrinkage performance and mechanical properties of UHPC, a low-activity MEA with a reactivity value of 220 s and a dosage of 6% is suggested in this study.

Key words: magnesium oxide expansive agent, ultra-high performance concrete, autogenous shrinkage, compressive strength, hydration degree, expansion performance

中图分类号:

TU528

杨东洋, 曹鸿猷, 黄京龙. MgO膨胀剂对超高性能混凝土收缩性能的影响[J]. 硅酸盐通报, 2022, 41(10): 3420-3427.

YANG Dongyang, CAO Hongyou, HUANG Jinglong. Effect of MgO Expansive Agent on Shrinkage Performance of Ultra-High Performance Concrete[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2022, 41(10): 3420-3427.

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