Reaction Mechanisms for the Formation of C-S-H Gel During the Early Hydration of Cement

水泥早期水化过程中C-S-H凝胶形成的反应机理

• 批准号: 0409571
• 负责人: Hamlin Jennings
• 金额: $ 30.99万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-08-01 至 2008-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0409571&HistoricalAwards=false
• 关键词: Reaction; Mechanisms; Formation; Gel; During

Reaction Mechanisms for the Formation of C-S-H Gel During the Early Hydration of CementAbstractWhen cement and water are mixed the resulting paste typically stays fluid for several hours before it sets and hardens. This period of time, the induction period, is technically extremely important because it allows enough time for the concrete to be mixed, transported, and poured into place. The induction period ends abruptly and is followed by a period of accelerating reaction that leads to setting and hardening. The versatility and widespread use of Portland cement concrete results, to a large extent, from the ability to control these hydration processes by the use of chemical admixtures, for example to either to extend the period of workability or shorten the time to set. Despite the fundamental importance of the concrete hardening process to the construction industry, and the fact that these chemical admixtures are of significant industrial importance, the fundamental chemical mechanisms underlying the cement hydration process are not well understood. This problem has been debated in the literature for more than 100 years without resolution. In recent years, modern analytical techniques have provided new information about the reaction products formed by the hydration of cement. These new findings led to the development of a quantitative nanometer-level model of cement paste by one of the present proposers, which is receiving increasing acceptance. Also, recently under NSF support new information about the structure and solubility of the main reaction product in cement has been obtained. This knowledge has provided new insight about the mechanisms that control the rate that cement paste and concrete hardens, and the promise of a much deeper understanding of the reactions between cement and water. It also opens the door not only to controlling the rate of hydration of cement paste, but also to controlling the microstructure and thus the properties of the final concrete. This will have a significant impact on the industry that supplies chemical admixtures for concrete, and on understanding the overall effects of adding a wide variety of materials to concrete.

水泥早期水化形成C-S-H凝胶的反应机理当水泥和水混合时，生成的浆体在凝结和硬化之前通常会保持液体状态数小时。这段时间，即诱导期，在技术上是极其重要的，因为它为混凝土的搅拌、运输和浇注提供了足够的时间。诱导期突然结束，紧随其后的是导致凝固和硬化的加速反应时期。波特兰水泥混凝土的多功能性和广泛使用在很大程度上是由于能够通过使用化学外加剂来控制这些水化过程，例如延长可加工期或缩短凝结时间。尽管混凝土硬化过程对建筑业至关重要，而且这些化学外加剂具有重要的工业意义，但水泥水化过程背后的基本化学机制尚不清楚。这个问题在文献中争论了100多年，但没有得到解决。近年来，现代分析技术提供了有关水泥水化反应产物的新信息。这些新发现促使其中一位提出者开发了一种水泥浆体的纳米级定量模型，该模型正在被越来越多的人接受。此外，最近在NSF的支持下，获得了关于水泥中主要反应产物的结构和溶解度的新信息。这一知识为控制水泥浆体和混凝土硬化速度的机制提供了新的见解，并有望更深入地了解水泥和水之间的反应。它不仅为控制水泥浆体的水化速度打开了大门，也为控制最终混凝土的微观结构和性能打开了大门。这将对供应混凝土化学外加剂的行业产生重大影响，并有助于理解向混凝土中添加各种材料的整体效果。