Adsorption characteristics of water-reducing agents on gypsum surface and its effect on the rheology of gypsum plaster
Adsorption characteristics of water-reducing agents on gypsum surface and its effect on the rheology of gypsum plaster
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DOI：
10.1016/j.cemconres.2004.04.016
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发表时间：
2005-03-01
影响因子：
11.4
通讯作者：
Wan, TZ
中科院分区：
文献类型：
--
作者：
Peng, JH;Qu, JD;Wan, TZ
采用紫外-可见吸收分光光度计、Zeta电位分析仪和X射线光电子能谱仪研究了β-萘磺酸型（BNS）和聚羧酸型（PC）两种高效减水剂的吸附特性、表面电化学性质及其对石膏流动性的影响。结果表明，BNS和PC在石膏表面的吸附近似符合Langmuir吸附等温式。BNS的吸附属于物理吸附，吸附热为14.71 kJ/mol，吸附层厚度为120埃; PC的吸附属于化学吸附，吸附热为20.85 kJ/mol，吸附层厚度为120埃。BNS的吸附构象位于石膏表面的平面上，产生弱的空间位阻，抑制了石膏颗粒的团聚。其分散效果主要取决于Zeta电位产生的静电斥力，而Zeta电位的大小取决于BNS在石膏表面第一吸附层的吸附量。PC的吸附构象呈梳状，吸附层侧链产生较强的空间位阻，其分散能力主要来自空间位阻和静电斥力的综合作用。空间位阻分散受石膏快速水化的影响较小，其稳定性远优于静电斥力分散，使新拌石膏流动损失小。(c)2004 Elsevier Ltd.保留所有权利。
In this study, by using UV-visible adsorption spectrophotometer, Zeta potential analyzer and X-ray photo spectroscopy, the adsorption characteristics and surface electrochemical properties of two types of superplasticizer-beta-naphthalene sulfonic acid type (BNS) and polycarboxylate type (PC) and their effects on the fluidity of gypsum plaster were studied. The results show that the adsorption of BNS and PC on gypsum surface approximately conforms to Langmuir's adsorption isotherm. The adsorption of BNS belongs to physical adsorption, its adsorption heat being 14.71 kJ/mol and the thickness of adsorption layer 120 angstrom; while the adsorption of PC belongs to chemical adsorption, with an adsorption heat of 20.85 kJ/mol and a thickness of adsorption layer of 120 angstrom. The adsorption conformation of BNS is lying on the flat of gypsum surface, generating weak steric hindrance to inhibit agglomerate of gypsum particles. Its dispersion effect mainly depends on electrostatic repulsive force caused by zeta-potential, which is determined by the adsorbed amount of BNS at the first adsorption layer on gypsum surface. The adsorption conformation of PC is comb-shaped, generating strong steric hindrance by side chains of adsorption layer, thus, its dispersion ability mainly comes from a combination effect of steric hindrance and electrostatic repulsive force. The dispersion by steric hindrance is less affected by the rapid hydration of gypsum, thus, its stability is much better than that of electrostatic repulsive force, resulting in little flow loss of fresh gypsum plaster. (c) 2004 Elsevier Ltd. All rights reserved.