碎片测试和纳米波罗力学反转了水泥水化是收缩性的经典范式
Raúl E Marrero Rosa1, Tapiwanashe Bhibho1, Ahmet A Dőnmez2
1Civil and Environmental Engineering Department, Northwestern University, Evanston, IL 60208.
概括
在高性能混凝土中,水化水泥会导致膨胀,而不是收缩. 这挑战了传统观点,并表明当前的ASTM化学收缩测试对现代混凝土具有误导性.
科学领域:
- 材料科学 材料科学 材料科学
- 土木工程 土木工程是指土木工程.
- 化学工程是化学工程的重要组成部分.
背景情况:
- 从历史上看,水化水泥,特别是酸水合物 (C-S-H) 形成,根据纳米尺度的观测被认为是收缩性的.
- 这种合同的观点影响了混凝土的性能模型,特别是在具有低水-水泥比率的高性能混凝土 (HPC) 中.
研究的目的:
- 为了研究在高性能混凝土中水泥水化过程中的宏观体积变化.
- 重新评估化学收缩现象及其在现代混凝土配方中的测量.
主要方法:
- 利用激光显微镜-拓来测量薄 (0.5毫米) 高性能混凝土碎片的长度变化.
- 在浸水条件下进行实验,以评估持续的孔和,并与密封条件相比,诱导自我干燥.
主要成果:
- 与纳米尺度的观测和传统假设相反,宏观水泥糊由于不断增长的C-S-H粒子而呈现膨胀.
- 在连续再和下薄的HPC标本显示扩张,取消了自干燥效应.
- 密封的标本显示收缩,证实了自我干燥在防止毛孔再和时的作用.
结论:
- 宏观水泥水化导致膨胀,这是以前在标准测试中被忽视的现象.
- 目前美国测试和材料学会 (ASTM) C1608化学收缩测试对现代HPC具有误导性,因为它们无法解释快速的孔和水合膨胀.
- 对标准化测试方法的修订是必要的,以准确地描述现代混凝土的行为.
相关概念视频
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01:18Porosity in Cement Paste
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01:23Pore Size Distribution
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01:20Microcracking in Concrete
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01:27Shrinkage in Concrete
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01:29Strength and Heat of Hydration
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