关于水泥系统的化学和自生收缩的审查
Hassan Ghanem1, Rawan Ramadan1, Jamal Khatib1,2
1Faculty of Engineering, Beirut Arab University, Beirut 11-5020, Lebanon.
Materials (Basel, Switzerland)
|January 23, 2024
概括
化学收缩 (CS) 和自身收缩 (AGS) 是水泥材料早期破裂的关键因素. 本综述涵盖了它们的测量,建模以及水结合剂比率,水泥成分和补充水泥材料的影响.
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.
- 建筑材料 建筑材料
背景情况:
- 化学收缩 (CS) 和自身收缩 (AGS) 是影响水泥材料早期破裂的内在特性.
- CS驱动自干燥,AGS和干燥收缩,CS和AGS在初始设置时是相同的,但后来分歧.
- 了解这些收缩现象对于预测和减轻混凝土结构中裂纹至关重要.
研究的目的:
- 在水泥系统中提供化学收缩 (CS) 和自身收缩 (AGS) 的全面审查.
- 检查CS和AGS的测量技术,建模方法和预测方法.
- 突出水与粘合物比率,水泥成分,补充水泥材料 (SCM) 的影响,并引入对生物纤维的新型研究.
主要方法:
- 文献综述涵盖了170多个参考文献,其中35个是在2020年之后发表的.
- 对CS,AGS之间的关系和影响因素,如w/b比率和水化程度等实验数据的分析.
- 包括作者最近进行的关于生物纤维对水泥复合材料中CS影响的研究.
主要成果:
- CS取决于水与粘合剂的比率 (w/b) 并与水合度成比例;较低的w/b比率导致更高的CS和AGS.
- 水泥成分和SCM显著影响CS和AGS.
- 飞灰 (FA) 的添加减少了CS和AGS,而废渣的加入没有.
结论:
- 该审查综合了关于CS和AGS的当前知识,强调它们在水泥水化和材料性能方面的关键作用.
- 澄清了各种成分,包括SCM如FA和渣,对收缩的影响.
- 确定了关于生物纤维对CS影响的研究缺口,并提出了新的发现来解决这一问题.
相关概念视频
01:27Shrinkage in Concrete
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Shrinkage in concrete is primarily due to water loss from evaporation, hydration of cement, or carbonation, leading to a reduction in volume. The volumetric contraction results in volumetric strain in concrete. However, in practice, shrinkage is measured as linear strain, which is one-third of the volumetric strain.
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01:21Drying Shrinkage
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When hardened concrete is exposed to air with a relative humidity of less than 100 percent, it begins to lose the free water within its capillaries. As this water evaporates, the water initially adsorbed onto the calcium silicate hydrates migrates towards these now empty spaces and eventually evaporates as well. Over time, as more water leaves, the volume of the concrete decreases, a phenomenon known as drying shrinkage.
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01:24Carbonation Shrinkage
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Atmospheric CO2 penetrates the concrete's pores and, in the presence of moisture, forms carbonic acid, which then reacts with calcium hydroxide in the hydrated cement, forming calcium carbonate. This process reduces the concrete's volume and is termed carbonation shrinkage.
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01:24Hydration of Cement
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Hydration of cement is a chemical reaction between cement particles and water. This process occurs primarily through two mechanisms: through-solution and topochemical. In the through-solution process, anhydrous compounds dissolve into their constituents, hydrates form in the solution, and then precipitate from the supersaturated solution. The topochemical process involves solid-state reactions at the cement particle surface. The through-solution process dominates the topochemical process at the...
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01:26Alkali Aggregate Reaction in Concrete
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The alkali-aggregate reaction in concrete involves natural siliceous minerals in aggregates reacting with alkaline hydroxides derived from cement alkalis. This reaction forms an alkali-silica gel that absorbs water, swells, and increases in volume, which is confined by the surrounding cement paste, creating internal pressures that crack and disrupt the concrete. The extent of expansion and damage can be partly attributed to the alkali-silica reaction's osmotic hydraulic pressure and the...
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01:17Soundness of Cement
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