摘要
采用紫外吸收光谱分析、微电泳仪、光电子能谱分析技术研究了萘系、多羧酸系 2种类型减水剂在石膏表面的吸附特性、表面电化学性能及其对石膏浆体流动性的影响。结果表明 ,FDN、HC在石膏颗粒表面的吸附基本符合 L angm uir等温方程 ,FDN为物理吸附 ,HC为化学吸附。 FDN为平躺吸附 ,吸附量较大 ,吸附层的静电作用较强 ,空间位阻小 ,其分散作用主要取决于静电斥力 ,ζ电位主要取决于 FDN首层吸附量 ;多羧酸为梳状吸附 ,吸附量较小 ,静电效应较弱 ,但吸附层空间位阻较大。减水剂分散性取决于ζ电位静电斥力和吸附层空间位阻。由于水化产物对静电斥力的屏蔽效应 ,静电斥力分散作用的稳定性差 ,其流动度经时损失大。空间位阻的分散性受胶凝材料水化作用的影响较小 ,其稳定性优于静电斥力。
In this study, by use of UV-visible adsorption spectrophotometer, micro-electrophoresis Zeta-potential analyzer, and X-ray photo spectroscopy, the adsorption characteristics, surface electrochemical properties of two types of superplasticizer β-naphthalene sulfonic acid type (FDN in commercial name) and polycarboxylate type (HC in commercial name) and their effects on fluidity of gypsum plaster have been researched. The results show that the adsorption behavior of FDN and HC on gypsum surface approximately conforms to Langmuir′s adsorption isotherm. The adsorption of FDN belongs to physical adsorption with high amount adsorbed. Its adsorption conformation is in form of lying on the flat of gypsum surface with very weak steric hindrance, so its dispersion effect mainly depends on electrostatic repulsive force caused by ζ -potential which is determined by adsorbed amount of FDN at first adsorption layer on gypsum surface. HC molecular is chemically adsorbed on the surface of gypsum particles in comb-shaped form, which generates weak electrostatic repulsive force and strong steric hindrance that is mainly responsible for its dispersion ability. The dispersion capacity of water-reducing agents depends on electrostatic repulsive force and steric hindrance. The dispersion of electrostatic repulsive force is not stable due to the shelter effect generated by the new hydration products, so the fluidity loss with hydration time is usually very great. While the dispersion of steric hindrance is less affected by the rapid hydration of gypsum, so its stability is much better than that of electrostatic repulsive force, resulting in little flow loss of fresh gypsum plaster.
出处
《武汉理工大学学报》
CAS
CSCD
2003年第11期25-28,共4页
Journal of Wuhan University of Technology
基金
国家自然科学基金 (5 0 0 780 5 5 )
关键词
石膏
减水剂
吸附
电化学性质
空间位阻
gypsum
water-reducing agents
adsorption
electrochemical properties
steric hindrance
