钙硅比对水化硅酸钙结构、Zeta电势及减水剂吸附性能的影响分析

Effect of Calcium-Silicon Ratio of Calcium Silicate Hydrate on Its Structure,Zeta Potential and Adsorption Capacity of Superplasticizer

为探究水化硅酸钙(C-S-H)晶核剂对掺减水剂混凝土的影响,研究了不同钙硅比的水化硅酸钙对聚羧酸减水剂的吸附性能。通过120℃水热反应法制备水化硅酸钙,并采用XRD、SEM和29Si NMR对所制备的Ca/Si为1.0、1.3和1.6的水化硅酸钙样品进行表征;同时通过Zeta电势、总有机碳分析(TOC)和流动性分析探究了由钙硅比的变化对水化硅酸钙的Zeta电势和减水剂吸附性能以及对水泥浆体流动度的影响。试验结果表明,水化硅酸钙的链长和结晶度的优劣主要受到钙硅比的影响,钙硅比增大,链长变短,结晶度变差;水化硅酸钙的Zeta电势随着钙硅比增加而增大;C-S-H在超纯水中的电导率随钙硅比增加而变大;在不同氢氧化钙浓度的溶液中,Ca/Si为1.6的样品较1.0样品能吸附更多的减水剂;并且拥有较好的浆体流动性能。因此,高钙硅比的水化硅酸钙对聚羧酸减水剂拥有较强的吸附能力,并且对含聚羧酸减水剂的水泥浆体流动性能影响相对较小。

In order to investigate the effect of calcium silicate hydrate(C-S-H)seeding on concrete with superpalsticizer,the adsorption properties of C-S-H with different calcium-silicon ratios on polycarboxylic acid superpalsticizer were studied.Calcium silicate hydrate was prepared by hydrothermal method at 120℃,and XRD,SEM and 29Si NMR were used to characterize the prepared C-S-H samples with Ca/Si of 1.0,1.3 and 1.6.By Zeta potential,total organic carbon analysis(TOC)and fluidity analysis,the effect of Ca/Si on the Zeta potential of calcium silicate hydrate,the adsorption capacity of superpalsticizer and the fluidity of cement paste were explored.The results show that the chain length and crystallinity of calcium silicate hydrate are mainly affected by the ratio of calcium to silicon.As the calcium to silicon ratio increases,the chain length becomes shorter and the crystallinity becomes worse.The Zeta potential of calcium silicate hydrate increases with the Ca/Si increasing.In ultrapure water,the conductivity of C-S-H increases as the Ca/Si increases.In different calcium hydroxide concentrations,the sample with Ca/Si=1.6 absorbs more superplasticizer than Ca/Si=1.0,and it has better flow performance of cement paste.Therefore,the high calcium-silicon ratio of C-S-H has a stronger adsorption capacity for polycarboxylic acid superplasticizer,and has a relatively small effect on the flow property of cement paste containing polycarboxylic acid superplasticizer.