缓释技术在混凝土中的应用研究进展

Research Progress of Controlled-release Technology in the Field of Concrete

近年来,随着我国基础设施建设的迅速发展,混凝土作为现代土木工程设施建设中最重要的工程材料之一,市场对其工作性、耐久性、施工性等综合性能的要求越来越高。目前混凝土在实际应用当中存在着一些问题,如混凝土因开裂而导致的钢筋锈蚀、结构强度和承载力下降等耐久性问题,混凝土坍落度损失问题,水泥水化过快等问题。因此,研究人员致力于研发具有缓释效果的混凝土外加剂以解决上述各类问题。缓释技术的出现引起人们的极大关注,在20世纪50年代首先应用于农业方面,随后应用于医学药物研发方面,并逐渐应用于化肥、农药、化工等领域。在混凝土领域,缓释技术目前已在水泥基材料的内养护、裂缝自修复、膨胀历程控制、阻锈与水化历程调控等方面被广泛应用。在混凝土领域已取得成功应用的缓释材料包括高吸水树脂(SAP)、微胶囊、缓释型聚羧酸减水剂等。SAP通过复杂的分子结构在水泥拌和过程中吸收大量水分,在后期硬化干燥过程中,及时缓慢释放出水分子,从而达到抑制水泥基材料变形开裂的效果。微胶囊将修复剂以复合材料的形式存储起来,使其在裂缝等外力作用下释放出来,发挥抑制裂纹的扩展并修复裂纹的作用。在混凝土坍落度研究领域,采用碱缓释的技术方案实现了分散剂分子在水泥环境中的持续释放,使得混凝土的流动度可以长时间保持稳定。本文根据缓释技术的类型和特点,分别从物理型缓释和化学型缓释两个方面介绍了缓释技术在混凝土领域中的应用及其进展,主要讨论了混凝土缓释技术在水泥基材料的内养护、裂缝自修复、阻锈与坍落度保持等性能调控中的应用,希望能为研发性能更优良的用于混凝土领域的缓释材料提供参考。

In recent years,with the rapid development of infrastructure in our country,concrete is one of the most important engineering materials in the construction of modern civil engineering facilities,the market has increasingly higher requirements on its workability,durability,constructability.At present,there are some problems in the practical application of concrete,such as,durability problems caused by cracking of concrete included the corrosion of steel bars and decrease in structural strength and bearing capacity,the slump loss problems of concretes,and excessive cement hydration.Therefore,researchers are committed to researching concrete admixtures with control-release effects to solve various problems.The emergence of control-release technology hasattracted great attention.It was first applied to agriculture in the 1950 s,then applied to the research of medical drugs,and the gradually applied to the fields of fertilizers,pesticides and chemical industries.In the field of concrete,controlrelease technology has been applied in the performance control of cement-based materials such as internal curing,crack self-repairing,expansion process control,rust inhibition and hydration process control.Controlled-release materials that have been successfully applied in the field of concrete include SAP,microcapsules,and controlled-release polycarboxylate superplasticizer,etc.SAP absorbs a large amount of water during the cement mixing process through its complex molecular structure,and slowly releases water in time during the later hardening and drying process,so as to achieve the effect of inhibiting the deformation and cracking of cement-based materials.The microcapsule stores the repair agent in the form of composite material,so that it can be released under the external forces such as cracks,so as to inhibit the expansion of cracks and repair the cracks.In the research field of concrete slump,the continuous release of dispersant molecules in cement environment is realized by the technology of alkali-responsive slow-release,so that the fluidity of concrete can be kept stable for a long time.According to the types and characteristics of controlled-release technology,the applications and progress of controlled-release technology in concretes are respectively reviewed from physical and chemical controlled-release technology in this paper.The applications of concrete controlled-release technology in the performance control of cement-based materials such as internal curing,crack self-repairing,rust resistance,and slump retention are introduced.This article is expected to provide a reference for the research of controlled-release material with better performance in the field of concrete.