高吸水树脂对混凝土收缩开裂的改善作用及其机理

Mechanism and effect of SAP for reducing shrinkage and cracking of concrete

高吸水树脂(SAP)是能够吸收高倍率水溶液并在干燥环境中释放水分的高分子功能材料。文中通过混凝土早期开裂、限制收缩及非限制收缩的试验,研究了SAP对混凝土收缩开裂性能的改善作用,并与预浸轻集料的作用进行了对比较。试验结果表明,SAP可以使混凝土的开裂及收缩减小30%-50%,比采用预浸轻集料的内养护措施效果更佳,在易于发生收缩开裂和(或)不易养护的结构中有重要的推广应用价值。SAP改善混凝土的早期开裂及收缩性能的机理在于,SAP颗粒对水的吸收-解吸、部分吸收水与高分子链的氢键键合及SAP粒子表面成膜等作用延缓了水分的散失、改变了混凝土内部湿度状态及分布。

SAPs have the ability to absorb a significant amount of liquid many times their own weight from the surroundings and retain the liquid within their structure without dissolving and desorb it when in the dry environment. The improvement of concrete shrinkage and ear-age cracking by using SAP was studied by experimental investigation such as plastic cracking tests and shrinkage tests,and its effect was compared with that of using pre-soaked ceramsite and perlite. The results show that SAP can effectively improve the cracking and shrinkage of concrete with achieving a 30%-50% decrease. The mechanism of the water absorption-desorption process of SAP particles,some water being bonded on macromolecule by hydrogen bond and filmforming on SAP particles retarded the water losing and changed the moisture distribution in concrete,and thus reducing the cracking and shrinkage of concrete.