混凝土干燥收缩开裂机理分析

Analysis of Drying Shrinkage Cracking Mechanism of Concrete

固态和液态物质从广义上来讲都是凝聚态结构,硬化水泥浆和混凝土也不例外。水化产物结构形成过程中,基本粒子在排列或结构时必然要经过离浆这一过程,而离浆的结果就是凝聚体结构上的收缩。失水后的凝聚体中形成气固界面,在表面张力和毛细作用的共同作用下,不仅收缩的幅度增加,而且使水化产物无法填充到凝聚体收缩后形成的空间,最终宏观裂缝产生。以减水剂掺合料为代表的用于混凝土高性能化的材料增加了表面失水和泌水,是导致现代混凝土更易开裂最主要的原因。降低收缩开裂,必须从防止混凝土内部水分的散失和降低表面水分的散失两个方面着手。

In a broad sense,both solid and liquid materials are condensed structure,and hardened cement slurry and concrete are no exception.In the process of hydration product structure formation,the basic particles in the arrangement or structure must go through the process of desizing,and the result of desizing is the shrinkage of condensed structure.Under the combined action of surface tension and capillary action,not only the shrinkage amplitude increases,but also the hydration products can not fill the space formed by the shrinkage of the condensate,resulting in macro cracks.Superplasticizer admixtures,as the representative of high performance materials for concrete,increase the surface water loss and bleeding,which is the main reason for modern concrete to crack more easily.In order to reduce the shrinkage cracking,it is necessary to prevent the internal moisture loss and reduce the surface moisture loss.