缓凝剂对水泥浆中自由水状态演变的影响

Effects of retarder on the evolution process of water in the cement paste

摘要:

利用低场核磁共振技术研究了HN-1型缓凝剂对水泥浆体中可蒸发水的横向弛豫时间(T_2)及其状态演变过程的影响。结果表明：HN-1型缓凝剂的加入降低了水泥浆体早期的水化速率，延长了水泥的水化诱导期。硬化浆体的孔结构伴随着浆体中可蒸发水的存在状态的演变而变化。低场核磁共振技术可以在不破坏样品结构的前提下而检测到样品中孔结构的变化。研究发现硬化浆体内可挥发水的弛豫时间随养护时间的延长趋向于短弛豫时间，并且其迁移速率随水灰比和缓凝剂加量的增加而减小，毛细水逐渐向凝胶水和物理结合水转化，主峰平均弛豫时间降低，表明了浆体内孔结构的细化。利用X衍射进一步研究了缓凝剂对水泥浆水化产物的影响，发现缓凝剂的加入只是改变了水化过程，并未影响水泥浆的最终水化程度。

Abstract:

Low-field NMR was used to study the effects of retarder HN-1 on the transverse relaxation time (T_2) and the states evolution of water in the cement paste. Analyses the results can be seen that the retarder HN-1 reduces the early hydration rate and extend the induction period of cement hydrated. The changes in the pore structure of hydrating cement paste are accompanied by changes of the states of water in cement paste such. Low-field NMR techniques can be used to observe these changes in the case without destroying the structure of the samples. It can be found from the changes of the relaxation time of water in the hardened paste that the relaxation time of volatile water in hardened paste tends to be shorter while curing time increases, and the migrated rate slows down with the increase of water-cement ratio and the amount of retarder, Capillary water gradually transforms into gel water and physically bound water. The decrease of the average relaxation time of main peak indicates the refining of pore structure in hardened paste. ?The study of X diffraction showed the addition of retarder only changed the process of hydration, but had no effect on the final hydration degree of cement paste.