【作者】 曹志宇；

【导师】 张长清；

【作者基本信息】 华中科技大学 ， 结构工程， 2011， 硕士

【摘要】 在工程建设中,自密实混凝土(SCC)的应用变得越来越广泛,它具有无振捣、噪音低、浇筑速度快、施工工期短等特点。增稠剂是自密实混凝土的重要组成部分之一,它可以起到减少泌水、提高黏聚性的作用。尽管有不同种类的增稠剂应用于混凝土工程,但增稠剂对水泥性质影响却缺乏系统研究,本文以增稠剂聚丙烯酰胺(PAM)为研究对象,研究了PAM对水泥的标准稠度用水量、凝结时间、电阻率、微观结构、黏度、收缩和强度等性质的影响。研究表明,掺入PAM时,水泥的标准稠度用水量随其掺量的增加而增大,水泥浆体的凝结时间也明显延长。当PAM掺量在0.1‰以下时,水泥浆体黏度显著增大,PAM掺量为0.1‰-0.8‰时,黏度的增长速度变缓。表明PAM水解形成的含羧基共聚物与金属离子形成含离子键的化合物,从而引起PAM分子间的交联。PAM对水泥浆体的早期电阻率值影响不大,而后期电阻率值则随着PAM掺量的增加而增大,同时PAM的掺入也提高了电阻率在水化后期的增长速度。掺入PAM的水泥浆中气孔孔隙率有所增大,同时水化产物钙矾石(AFt)的针状结构更细更密,浆体局部结构也更加密实,减小了浆体中水化产物间连通孔所占空间及其在全部孔隙中的比例。在PAM掺量不大于0.5‰时,可以减小收缩率;在PAM的掺量不大于0.8‰的情况下,试件强度未出现明显下降。更多还原

【Abstract】 The application of self-compacting concrete (SCC) is becoming increasingly widespread?in construction. SCC’s properties include no vibration, low noise, casting speed, short construction period and so on. Viscosity modified agent is an important part of self-compacting concrete, and it can decrease the risk of bleeding and improve the role of cohesiveness. Although all kinds of thickening agent have been used in concrete works, the influence of the properties of cement is lack of systematic research. As a representative of the thickening agent, the influence of polyacrylamide (PAM) on the cement paste including the water consumption for normal consistency of cement, setting time, resistivity, microstructure, viscosity, shrinkage and strength properties has been studied in the paper.Studies have shown that the water consumption for normal consistency of cement increased with the increase of the content of PAM, and the setting time of cement paste was significantly prolonged. The viscosity of cement paste significantly increased when the PAM content is below 0.1‰, and the viscosity of the growth rate slowed while PAM dosage is between 0.1‰to 0.8‰. It indicated that the compounds containing ionic bonds, which are formed by the carboxyl-containing copolymer of hydrolyzed PAM and metal ions, caused the cross-linking of PAM molecules. PAM had little effect on the early resistivity of the cement paste, but the late electrical-resistivity increased with the increase of PAM content, so did the rate of the change of electrical-resistivity. The incorporation of PAM increased the closed pore in the cement paste, refined and compacted the needle structure of hydration products ettringite (AFt), local structure of paste was denser and more compact, and thus the space and ratio of inter-connected pores reduced. It could reduce the shrinkage rate when PAM content is not more than 0.5‰; in the cases of PAM content is not more than 0.8‰, the strength of specimen didn’t appear to decrease significantly.更多还原