硫酸盐影响聚羧酸减水剂分散性的作用机理

Effect of Sulfates on Dispersity of Polycarboxylate Superplasticizer and Its Mechanism

系统研究了硫酸盐对聚羧酸减水剂吸附-分散性能的影响及其作用机理.通过净浆流动度试验及Marsh时间试验研究了硫酸盐种类及掺量对聚羧酸减水剂分散性能的影响,并通过zeta电位、平衡吸附量及絮凝结构形貌等微观测试手段对硫酸盐影响聚羧酸减水剂分散性的作用机理进行分析.结果表明:随着硫酸根溶出率及溶出速率的增加,硫酸根离子与聚羧酸减水剂间的竞争吸附作用增强;硫酸根离子破坏浆液双电层,促使zeta电位绝对值下降,从而削弱水泥颗粒表面的静电斥力作用,导致水泥浆体絮凝结构数量及强度增大,相同剪切速率对浆体中的絮凝结构破坏程度下降,浆体分散性及流变性下降.

In order to investigate the effect of sulfates on the dispersibility of polycarboxylate superplasticizer and its mechanism,different kinds of sulfates with various contents were added into cement paste mixed with polycarboxylate superplasticizer.By fluidity test and Marsh time test,the effect of sulfates on the flowability of cement paste was studied.Furthermore,the rheological properties of cement paste were investigated through the rheometer,the zeta potential of cement paste was investigated through the zeta potential measurement analyzer,the competitive adsorption between sulfates and polycarboxylate superplasticizer was investigated through ultraviolet spectrophotometry,and the flocculent structure of cement paste was observed through optical microscope,respectively.The results indicate that alkali sulfates （Na2SO4 and K2SO4） have great influence on the dispersibility and retentivity of polycarboxylate superplasticizer; with the increase of dissolution of alkali ions,the competitive adsorption of sulfate ions enhances.Meanwhile,the absolute value of zeta potential decreases due to the destroyed double electrode layer.In this way,the electrostatic repulsion of cement particles is weakened and the flocculation structure becomes stronger.At a certain shearing rate,less degree of flocculation structure is damaged,leading to the decrease of rheological properties in cement paste.