Abstract: In this paper,a new type of amphoteric polymer retarder SN-3 is synthesized by solution polymerization,and infrared spectroscopy and elemental analysis is used to characterize the chemical structure of retarder SN-3. In addition,we further research the application performance of retarder SN-3,including the thickening time and the sensitivity to adding amounts and temperature. The results show that the cement paste with retarder SN-3 meets the requirements of the construction on site. Low-field nuclear magnetic resonance(NMR) test technology was used to study the influences of retarder SN-3 on the transverse relaxation time T₂ distribution of cement paste in a hydration process, under the same water to cement ratio,temperature and hydration time to test the transverse relaxation time of the pure cement paste C and the cement paste CHN mixed with polymer SN-3. The migration rate and peak shape index are two parameters employed to characterize the change trend of the T₂ distribution curve of cement paste. A further study about the retarding mechanism of the retarder SN-3 is obtained by low-field NMR analysis,XRD and SEM. The experimental results show that the retarder makes the bound level of water that fills in the flocculation structure decrease; the existence time of physically bound water increase,polymer SN-3 mainly by precipitation and complexation come to retarding effect.

Key words: retarder, the transverse relaxation time, retarding mechanism

摘要： 首先合成了一种新型两性聚合物缓凝剂SN-3，然后采用红外光谱和元素分析等测试手段对其进行结构表征。其次，对其应用性能作了进一步研究，主要包括稠化时间、加量和温度敏感性等，实验结果表明应用性能满足现场施工要求。利用低场核磁共振测试技术重点研究了缓凝剂SN-3对油井水泥浆水化过程中横向弛豫时间T₂分布的影响，在相同的水灰比、温度和水化时间下，对纯水泥浆C和掺有缓凝剂SN-3的水泥浆CHN的横向弛豫时间进行测试和分析，借助迁移速率和峰形指数两个参数表征水泥浆T₂分布曲线的变化过程。最后，结合X衍射和扫描电镜（SEM）进一步探讨缓凝剂SN-3的缓凝作用原理。实验结果表明，缓凝剂使水泥浆中填充于絮凝结构之间的水的受缚程度减小，存在时间变长，转化为化学结合水所经历时间变长；缓凝剂SN-3主要通过沉淀和络合作用达到缓凝效果的。

关键词: 缓凝剂, 横向弛豫时间, 缓凝机理