Development of a technology to control thermal cracking in concrete by means of a smart material

开发利用智能材料控制混凝土热裂的技术

基本信息

批准号：
15206061
负责人：
MIHASHI Hirozo
金额：
$ 27.79万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15206061/
关键词：
microcapsule hydration-rate thermal cracking smart material retardation effect 水和反応遅延剤水和熱

项目摘要

Hydration heat of cement in massive concrete causes significant thermal stress leading to cracking at early ages. In order to avoid such a stress, a smart material for controlling the hydration heat is developed in this study. As the first step, the influence of curing temperature history on mechanical properties of concrete is quantitatively discussed as a function of equivalent age. It was confirmed that high temperature curing of concrete at the early ages prevents the increase of strength in the matured condition. On the basis of these results, the melting temperature of paraffin microcapsule was chosen to be less than 60 degree C. Smart materials developed in this study are composed of paraffin microcapsule containing very fine particles of a hydration-retarder agent. Hence the rising rate of temperature of concrete and thermal stress are controlled under the specified value. Performance and applicability for practical purpose of the developed smart materials are verified by a ser … More ies of experimental studies. Conclusively the following results are obtained :1. Timing and technique of mixing the microcapsules with fresh concrete was one of the most difficult subjects in this study. While microcapsule are easily damaged during concrete mixing, adding the microcapsules to fresh concrete in agitator at the construction site just before placing the concrete is most acceptable for the practical purpose.2. Amount of microcapsules necessary for controlling the hydration rate of concrete is strongly dependent on the type of used fine aggregates. Therefore it is essential to examine the necessary amount of the microcapsules in advance.3. Reduction of hydration heating rate does reduce the thermal stress in concrete, though the maximum temperature is the same as that of plain concrete in case of a very thick and massive concrete. For the practical application, the necessary amount of microcapsule needs to be determined by analyzing the thermal diffusion process in the thickness of the member given in the design documents since the maximum temperature is much lower than that of the adiabatic condition as obtained in the experimental study especially when the hydration heating rate is reduced. Less

大量混凝土水泥的水合热引起明显的热应力，导致早期开裂。为了避免这种压力，在本研究中开发了用于控制水合热的智能材料。作为第一步，固化温度历史对混凝土机械性能的影响是根据同等年龄的函数进行定量讨论的。已经证实，早期混凝土的高温固化可防止在成熟条件下的强度增加。基于这些结果，选择了石蜡微胶囊的熔化温度小于60摄氏度。在这项研究中开发的智能材料由石蜡微胶囊组成，其中包含水合粘液器剂的非常细的颗粒。因此，在指定值下控制了混凝土和热应力温度的升高。通过更多的实验研究验证了开发智能材料的实际目的的性能和适用性。最终获得以下结果：1。将微胶囊与新鲜混凝土混合的时间和技术是本研究中最困难的主题之一。虽然在混凝土混合过程中很容易损坏微胶囊，但在放置混凝土之前，将微胶囊添加到施工现场的搅拌器中的新鲜混凝土中，这是最可接受的。2。控制混凝土的水合速率所需的微胶囊量很大程度上取决于使用的细骨料的类型。因此，必须提前检查必要数量的微胶囊3。水合加热速率的降低确实会降低混凝土中的热应力，尽管在非常厚的混凝土的情况下，最高温度与普通混凝土的最高温度相同。对于实际应用，需要通过分析设计文档中给出的构件厚度的热差过程来确定必要的微胶囊，因为最高温度远低于实验研究中获得的绝热条件的温度，尤其是当水合加热率降低时。较少的