超吸水树脂(SAP)在混凝土中的应用研究
Study on the application of super absorbent resin (SAP) in concrete
1 前言
1 Preface
在混凝土技术高速发展的今天，各种改善混凝土性能的新型外加剂得到积极开发和研究。超吸水树脂(super absorbent resin，以下简称“SAP”)发明于二十世纪80年代，是一种交联高分子化合物，其分子链上含有羧基、磺酸基、羟基和酰胺基等亲水官能团，能够吸收相当于自重几十倍到几千倍的水，在接触水或水溶液后开始肿胀形成水凝胶，具有良好的保水性。SAP最早应用于卫生和保健领域，之后工程界开始考虑将其应用于混凝土并开展试验研究[1]。作为一种新型的外加剂，SAP可以用来调节混凝土凝结和硬化时的水分平衡，有望用作低水胶比混凝土的内养护剂。
With the rapid development of concrete technology, various new admixtures have been actively developed and studied to improve the performance of concrete. Super absorbent resin (super absorbent resin, hereinafter referred to as "SAP") was invented in 80s twentieth Century. It is a crosslinked polymer compound. Its molecular chain contains hydrophilic functional groups such as carboxyl, sulfonic, hydroxyl and amides, which can absorb water that is tens to thousands times as much as self weight and open in contact with water or water solution. Swelling starts to form hydrogels with good water retention. SAP was first applied to the field of health and health care. After that, the engineering community began to consider its application in concrete and carry out experimental research on [1]. As a new admixture, SAP can be used to adjust the water balance of concrete during solidification and hardening, and is expected to be used as an internal curing agent for concrete with low water binder ratio.
本文简要介绍SAP在混凝土中的内养护机理、SAP对混凝土性能的影响，并对SAP作为混凝土内养护剂的应用前景进行展望。
This paper briefly introduces the internal curing mechanism of SAP in concrete and the effect of SAP on the performance of concrete, and looks forward to the prospect of the application of SAP as a curing agent in concrete.
2 内养护与SAP内养护机理
2 maintenance and maintenance mechanism in SAP
目前混凝土的养护方法分为外部养护和内部养护两种。通常，大部分混凝土结构工程的养护都是采用外部养护方法，如直接喷洒水、覆塑料薄膜（或草袋），或者表面喷洒养护剂等。这些方法不但消耗人力与资源，而且对于低水胶比混凝土来说，外部养护用水很难进入混凝土内部，后期即使经过长时间浸水也只能浸入几毫米，无法提供内部未水化水泥颗粒继续水化所需的水分。若采取表面喷洒养护剂的方法，很容易因某些部位喷洒难度高，或因疏忽而造成“漏喷”，导致混凝土缺乏良好的养护而引起强度发展“乏力”甚至产生开裂。
At present, concrete maintenance methods are divided into two types: external maintenance and internal maintenance. Generally, the maintenance of most of the concrete structural engineering uses external maintenance methods, such as direct spray water, plastic film (or straw bag), or surface spraying curing agent. These methods not only consume manpower and resources, but also for low water cement concrete, the external maintenance water is difficult to enter the concrete inside. Even after a long period of immersion, it can only be immersed in a few millimeters, which can not provide the water content needed for the continuous hydration of the internal unhydrated cement particles. If the surface spray curing agent is used, it is very easy to spray some parts with a high degree of difficulty or because of negligence, which leads to the lack of good maintenance of concrete, which causes the strength development "fatigue" or even cracking.
为了保证能给混凝土内部的水泥水化补充水源，从根本上解决混凝土早期自收缩和开裂问题，利用SAP材料的高吸水特性为混凝土养护助力，不失为一条创新的思路。在制备混凝土时掺入一定量的SAP，混凝土加水搅拌时，SAP迅速吸水并均匀分布在混凝土中，从而在混凝土内部形成微型“蓄水库”，当混凝土内部浆体因水泥水化而出现“缺水”现象时，由于湿度梯度的作用，促使SAP释放所吸水分，使水泥浆体中的湿度得到补偿，水泥继续水化，不致产生自收缩。图1是SAP在混凝土中吸收水分变化示意图，由于SAP掺量较小，其存在本身对混凝土强度的影响较小，甚至没有影响，因而是一种理想的内养护材料[2]。
In order to ensure the hydration of concrete inside the concrete to supplement the water source, the problem of early self shrinkage and cracking of concrete is fundamentally solved. It is an innovative idea to make use of the high water absorption properties of the SAP material for the concrete maintenance. When the concrete is mixed with a certain amount of SAP, when the concrete is mixed with water, the SAP is quickly absorbed and distributed evenly in the concrete, so as to form a micro "storage reservoir" inside the concrete. When the concrete interior slurry appears "water shortage" due to the hydration of cement, the release of SAP is caused by the effect of the humidity gradient. Moisture makes the moisture in cement paste be compensated, cement continues to hydrate, and does not produce autogenous shrinkage. Figure 1 is a schematic of SAP absorption of moisture in concrete. Because of the small amount of SAP, its existence itself has little influence on the strength of concrete, or even has no effect, so it is an ideal internal curing material [2].
3 SAP对混凝土性能的影响
Effect of 3 SAP on the performance of concrete
