预测大质量混凝土结构中早期热破裂风险的多步骤程序
Barbara Klemczak1, Aneta Smolana1
1Department of Structural Engineering, Silesian University of Technology, 44-100 Gliwice, Poland.
Materials (Basel, Switzerland)
|August 10, 2024
概括
大型混凝土结构中早期的热裂变是一个重大问题. 本研究提出了一种实际的三步方法来评估裂纹风险,在必要时平衡简化分析与先进的数值建模.
科学领域:
- 土木工程 土木工程是指土木工程.
- 材料科学 材料科学 材料科学
- 结构工程 结构工程
背景情况:
- 大型混凝土结构中早期的裂是影响耐用性和完整性的关键问题.
- 主要原因是水泥水化导致温度升高不均,导致热应力.
- 由于材料和技术变量,评估热裂变风险是复杂的.
研究的目的:
- 提出一种实用的三步方法,用于评估大质量混凝土结构中早期热裂解风险.
- 提供一个框架,平衡简化评估与先进的数值建模.
- 为了应对定义大规模结构的挑战和水化热效应的复杂性.
主要方法:
- 一个三步评估方法:1. 大型结构的简化分类. 2. 2. 2. 这是一个很棒的节目. 使用分析技术估计硬化温度和热应力. 3. 3. 3. 3. 这是一件很棒的事情. 对于具有已识别风险的结构,进行数值建模 (有限元分析).
- 该方法考虑了影响温度和应力的材料特性和技术因素.
- 一个例子应用涉及一个巨大的混凝土墙在基础上的程序说明程序.
主要成果:
- 拟议的方法提供了一个结构化的方法来评估热裂解风险.
- 它允许使用更简单的方法进行初始选,然后再采取复杂的数值分析.
- 该程序被证明对现实世界的应用具有实用性.
结论:
- 三步方法为评估大混凝土中早期热裂解提供了一个务实的解决方案.
- 它通过为高风险结构保留先进的数值建模来优化资源配置.
- 这种方法通过主动管理热应力风险,提高了质量混凝土结构的可靠性和耐用性.
相关概念视频
01:22Mass Concreting
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Mass concreting refers to the process of placing large volumes of concrete, such as in gravity dams. The heat generated during the cement hydration process and differential cooling rates within the concrete mass can lead to a temperature gradient, which can result in thermal cracks in the concrete mass.
To reduce the risk of such cracking, the concrete mix may incorporate low-heat cement and pozzolans to reduce the temperature rise. Pre-cooled angular aggregates and water-reducing admixtures...
To reduce the risk of such cracking, the concrete mix may incorporate low-heat cement and pozzolans to reduce the temperature rise. Pre-cooled angular aggregates and water-reducing admixtures...
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01:20Microcracking in Concrete
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Microcracking in concrete refers to the tiny cracks that can form within the material even before any external load is applied. These microcracks typically occur at the interface between the coarse aggregate and the hydrated cement paste, often as a result of differential volume changes prompted by variations in stress-strain behavior, as well as thermal and moisture movement. Initially, these microcracks remain stable and do not grow substantially until the concrete is stressed to about 30...
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01:28Types of Non-structural Cracks in Concrete
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Non-structural cracks are primarily of three types: plastic, early-age thermal, and drying shrinkage cracks. Plastic cracks are further classified into plastic shrinkage cracks and plastic settlement cracks.
Plastic shrinkage cracks typically form within hours after the concrete is poured. The concrete's surface dries faster than the bottom, creating tensile stress that the still-plastic concrete cannot withstand, leading to diagonal or randomly patterned cracks on the concrete surface.
Plastic shrinkage cracks typically form within hours after the concrete is poured. The concrete's surface dries faster than the bottom, creating tensile stress that the still-plastic concrete cannot withstand, leading to diagonal or randomly patterned cracks on the concrete surface.
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01:27Frost Action on Concrete
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Concrete structures in cold climates, such as those along roadsides, can retain moisture. This moisture makes them susceptible to frost-related damage when temperatures fall below freezing. Adding moisture worsens the damage during temperature fluctuations, leading to repeated freezing and thawing. De-icing salts, spread over these structures to melt ice, add to the freeze-thaw cycle, and draw even more moisture into the concrete.
This freeze-thaw cycle primarily causes surface scaling, where...
This freeze-thaw cycle primarily causes surface scaling, where...
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01:14Design Example: Managing Concrete Workability
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This example deals with managing the workability of concrete for a raft foundation project under hot weather conditions. Workability is crucial for ensuring the concrete is easy to place, compact, and finish. In this scenario, a slump test — a common method to measure the workability of fresh concrete — initially indicated low workability. This was attributed to the rapid water loss from the concrete mix, exacerbated by the high temperatures causing the course aggregates to heat up.
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01:20Hot Weather Concreting
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Concreting at elevated temperatures accelerates the hydration process, leading to quicker setting but potentially reducing the long-term strength of the concrete structure. Additionally, low air humidity fosters rapid moisture loss from the concrete, resulting in reduced workability, pronounced plastic shrinkage, and a higher likelihood of crazing.
Mitigating the heat increase in concrete can be economically achieved by shading aggregate stockpiles to prevent heating from solar radiation,...
Mitigating the heat increase in concrete can be economically achieved by shading aggregate stockpiles to prevent heating from solar radiation,...
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