难以确定热激活低等级粘土的波佐兰活动
Kateřina Šádková1, Vojtěch Pommer1, Martin Keppert1
1Department of Materials Engineering and Chemistry, Faculty of Civil Engineering, Czech Technical University in Prague, Thákurova 7, 166 29 Prague, Czech Republic.
Materials (Basel, Switzerland)
|October 26, 2024
概括
确定热激活粘土 (TAC) 的波佐兰活性对于它们作为补充水泥材料 (SCM) 的使用至关重要. 与石灰和机械强度测试的异热热量计是评估TAC的理想方法,与石灰和度测试不同.
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.
- 地质化学 地质化学
背景情况:
- 热激活粘土 (TACs) 正在作为补充性水泥材料 (SCMs) 进行探索.
- 精确的波佐兰活动评估对于优化TAC至关重要,但由于粘土的独特性质,传统方法可能不可靠.
- 现有的方法常常对 TAC 进行误导或产生误导性的结果.
研究的目的:
- 评估各种直接和间接方法的适用性,以确定TAC的波佐兰活动.
- 确定评估 TAC 的最可靠方法,考虑到它们与传统 SCM 相比的独特特性.
- 为了比较在不同温度下激活的不同粘土的性能.
主要方法:
- 使用了四种直接和四种间接的pozzolanic活动评估方法.
- 在不同温度下烧焦了三种不同类型的粘土.
- 方法包括使用石灰的异热热量计,机械强度开发和Frattini方法.
主要成果:
- 与机械强度发展相结合的异热热量计被证明是评估TAC的最合适方法.
- 研究人员发现,石灰和度测试在评估 TAC 时是不适用的.
- 通过关注热处理后的活动变化而不是直接与和曲线进行比较,Frattini方法的实用性得到了增强.
结论:
- 建议将异热热度测量和机械强度测试结合起来,以可靠地评估TAC的波佐兰活动.
- 石灰和度测试不适用于TAC.
- 修改Frattini方法的应用可以为热处理对粘土pozzolanicity的影响提供宝贵的见解.
相关概念视频
01:21Pozzolans
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Pozzolans are siliceous or aluminous materials blended with Portland cement. They interact with the calcium hydroxide produced during the hydration of Portland cement and contribute to improved strength and durability of concrete. The pozzolanic activity, a measure of a pozzolan's effectiveness, is typically assessed using the strength activity index, as defined in ASTM C 618-93, which calculates the ratio of the compressive strength of cement mixtures with and without pozzolan.
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01:29Strength and Heat of Hydration
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The hydration of cement is an exothermic reaction in which heat is generated as cement hydrates. This heat of hydration is critical to cement's strength development. The rate at which this heat is generated affects the temperature rise, with a majority of the heat being released early in the hydration process, half within the first three days, and about 75% within the first week.
The heat of hydration for each cement compound is significant; for instance, tricalcium aluminate (C3A) and...
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01:17Soundness of Cement
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The soundness of cement refers to the ability of cement paste to retain its volume after setting. Unsound cement can lead to expansion and structural damage due to the presence of free lime, magnesia, and calcium sulfate. Free lime hydrates very slowly, expanding and causing unsoundness, which is difficult to detect because it intercrystallizes with other compounds. Magnesia also reacts with water, forming crystals that can disrupt the cement's structure. Calcium sulfate can create...
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01:18Porosity in Cement Paste
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The porosity of concrete is a measure of the void spaces within its structure. These spaces impact its strength and durability significantly. When water and cement interact, a chemical reaction called hydration creates a semi-solid paste. This paste includes combined water, making up approximately 23% of the cement's dry mass, and gel water, which fills minuscule voids known as gel pores, accounting for about 28% of the cement gel volume.
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01:10Thermodynamics: Chemical Potential and Activity
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The effective concentration of a species in a solution can be expressed precisely in terms of its activity. Activity considers the effect of electrolytes present in the vicinity of the species of interest and depends on the ionic strength of the solution. The activity of a species is expressed as the product of molar concentration and the activity coefficient of the species.
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01:20Porosity and Absorption of Aggregate
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265