MgO膨胀剂对超高性能混凝土(UHPC)工作性的影响及其机理研究

摘要/Abstract

摘要： 超高性能混凝土(UHPC)因卓越的耐久性能和力学性能而在工程领域具有广阔的应用前景。然而,UHPC收缩性较大,限制了其进一步推广和发展。氧化镁(MgO)膨胀剂具有膨胀稳定、活性可控的特点,并且与UHPC相适应,因此被视为有良好应用前景的UHPC膨胀剂。本研究旨在探讨不同活性和掺量的MgO膨胀剂对UHPC工作性的影响,并通过XRD和SEM等手段进一步解释不同活性MgO膨胀剂对UHPC工作性的影响机理。研究结果表明,在掺入MgO膨胀剂的UHPC中,在低速剪切下观察到剪切稠化现象,而在高速剪切下观察到剪切稀化现象。与水泥颗粒相比,MgO膨胀剂颗粒对水具有更强的吸附能力。因此,MgO膨胀剂的活性越高,UHPC的流动性降低越显著,且UHPC的动态屈服应力增加,这在实际工程中需要更多的泵送能量。

关键词: 超高性能混凝土, 氧化镁膨胀剂, 流动度, 流变性能, 屈服应力, 工作性

Abstract: Ultra-high performance concrete (UHPC) has wide application prospect in engineering field because of its excellent performance. However, due to large shrinkage, the further promotion and development of UHPC were limited. Magnesium oxide (MgO) expansion agent has the characteristics of stable expansion, controllable activity, and is suitable for UHPC, so it is regarded as a UHPC expansion agent with great potential. The purpose of this study was to investigate the effects of different activity and dosages of MgO expansion agent on the performance of UHPC, and to further explain the mechanism of different activity of MgO expansion agent on the performance of UHPC by means of XRD and SEM. The results show that in UHPC mixed with MgO expansion agent, shear thickening is observed at low speed, while shear thinning is observed at high speed. Compared with cement particles, MgO expansion agent particles have stronger adsorption capacity to water. Therefore, the higher the activity of MgO expansion agent is, the more significant the decrease in the fluidity of UHPC is. And the dynamic yield stress of UHPC increases, which requires more pumping energy in practical engineering.

Key words: ultra-high performance concrete, MgO expansion agent, fluidity, rheological property, yield stress, workability

中图分类号:

TU528.55

李建华, 周锴, 邓强, 赵中军, 张伟, 唐国旺, 邹杰, 李婷饴, 袁荟凯. MgO膨胀剂对超高性能混凝土(UHPC)工作性的影响及其机理研究[J]. 硅酸盐通报, 2024, 43(8): 2817-2826.

LI Jianhua, ZHOU Kai, DENG Qiang, ZHAO Zhongjun, ZHANG Wei, TANG Guowang, ZOU Jie, LI Tingyi, YUAN Huikai. Effect of MgO Expansion Agent on Performance of Ultra-High Performance Concrete (UHPC) and Its Mechanism[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2024, 43(8): 2817-2826.

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