FDN在石膏颗粒表面的吸附特性及其对流动度影响(英文)

Adsorption Characteristics of FDN on Gypsum Surface and Its Effect on the Fluidity of Gypsum Plaster

FDN是胶凝材料最常用的减水剂,其分散作用是通过吸附实现的。采用紫外吸收光谱分析仪、微电泳仪、光电子能谱分析技术等,研究了FDN在石膏表面的吸附特性、电化学性质及其对流动性的影响。石膏对FDN的吸附为物理吸附,其吸附热为14.71kJ/mol,吸附层厚度12nm(120A);FDN为平躺吸附,吸附层的空间位阻小,其分散作用主要取决于静电斥力,ζ电位与FDN单分子层吸附量相关;由于水化产物对静电斥力的屏蔽效应和脱附,静电斥力分散作用的稳定性差,流动度经时损失较大。

FDN is a type of β-naphthalene sulfonic acid-based superplasticizer usually used in binding materials, and itsdispersion effect is realized through its adsorption. By using UV adsorption spectrophotometer, micro-electrophoresis, and x-rayphoto spectroscopy technology, the adsorption characteristics, surface electrochemical properties of FDN on gypsum and theireffects on fluidity of gypsum plaster were researched. The results show that the adsorption of FDN is physical adsorption, itsadsorption heat being 14.71 kJ/mol and the thickness of adsorption layer 12 um(120A). Steric hindrance of FDN asorptionlayer is very weak, so its dispersion effect depends mainly on electrostatic repulsive force caused by Zeta potential which wasclosely related with the adsorption amount of monomolecular layer. Electrostatic repulsive force effect is not stable because ofthe shelter effect of new hydration products and edsorption of water-reducing agent, leading to rapid fluidity loss of fresh gyp-sum plaster.