Development of performance control methods for concrete admixture of using the microcapsule

近年来发展了高强混凝土和高流动性混凝土。在这种混凝土中，自生收缩是不可忽略的，并且使用减缩剂来防止由于收缩而产生的裂缝。但是，由于大部分有效成分在收缩开始之前的早期被水泥水化产物吸收，因此需要使用一定量的该剂。本研究应用微胶囊技术，并采用表面包覆技术对减缩剂进行表面包覆，以控制减缩剂的化学作用过程。在表面涂层中，混合了三种不同类型的粉碎成碎片的微纤维。其中一种纤维在碱性水中熔化，而其他纤维是水溶性的。实验结果表明，通过改变涂层厚度和超细纤维的种类可以控制化学反应速率。它也被实验证明，自发收缩应变的情况下，早强波特兰水泥减少采用所提出的微胶囊。

Recently high-strength concrete and highly-flowable concrete have been developed. In such concrete, autogeneous shrinkage is not negligible and shrinkage-reduction agents are employed for preventing cracks due to the shrinkage. However, a certain amount of the agent needs to be used since a large part of effective components are absorbed by cement hydration products at an early age before the shrinkage starts. In this study, micro capsule technology was applied and surface coating techniques on the shrinkage-reduction agents were employed for controlling the chemical action process of the agents. In the surface coating layer, three different kinds of micro fibers crashed into pieces were mixed. One of the fiber was melt in alkaline water and the others were water-soluble. Experimental results showed that the chemical reaction rate of agents can be controlled by changing the coating thickness together with the type of micro fibers. It was also experimentally proved that autogeneous shrinkage strain in case of early-strength Portland cement was reduced by employing the proposed micro capsule.