Derkani Maryam H, Bartlett Nathan J, Koma Gaone, Carter Laura A, Geddes Daniel A, Provis John L, Walkley Brant
Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, UK; Department of Chemical and Biological Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, UK; Hazelwood Chemical Synthesis, The Lubrizol Corporation, The Knowle, Nether Lane, Hazelwood, Derbyshire DE56 4AN, UK.
Hazelwood Chemical Synthesis, The Lubrizol Corporation, The Knowle, Nether Lane, Hazelwood, Derbyshire DE56 4AN, UK.
J Colloid Interface Sci. 2022 Dec 15;628(Pt B):745-757. doi: 10.1016/j.jcis.2022.07.166. Epub 2022 Jul 29.
The influence of different alkali and alkaline earth cations (Na, K, Ca, and Mg), and of solution pH, on surface interactions of metakaolin particles with a sodium naphthalene sulfonate formaldehyde polymer (SNSFP) (a commercial superplasticizer for concretes) was investigated in aqueous systems relevant to alkali-activated and blended Portland cements. This study used zeta potential measurements, adsorption experiments, and both in situ and ex situ Fourier transform infrared spectroscopy measurements of the suspensions to gain a fundamental understanding of colloidal interactions and physicochemical mechanisms governing dispersion in this system. SNSFP was most effective in dispersing metakaolin suspensions in Ca-modified aqueous NaOH systems (CaCl-NaOH) at dosages of 5 wt.%. Additionally, Ca was the most effective alkaline earth cation mediator in providing a dispersion effect in metakaolin dispersed in aqueous NaOH and SNSFP mixtures, while Mg was the most effective in aqueous KOH and SNSFP mixtures. The colloidal dispersion remained stable in the highly alkaline environment, and therefore SNSFP could be utilized to improve dispersion of metakaolin-based alkali-activated systems. The suggested mechanism for colloidal stability and fluidity of metakaolin-based cements (e.g. Portland cement blends and alkali-activated cements) is explained by changes in the distribution and structure of the electric double-layer, as well as structural forces, due to alteration in surface charge density and hydrated shell, facilitating competitive adsorption of the polymer.
在与碱激发水泥和波特兰混合水泥相关的水体系中，研究了不同碱金属和碱土金属阳离子（Na、K、Ca和Mg）以及溶液pH值对偏高岭土颗粒与萘磺酸钠甲醛聚合物（SNSFP，一种混凝土用商业高效减水剂）表面相互作用的影响。本研究采用zeta电位测量、吸附实验以及悬浮液的原位和非原位傅里叶变换红外光谱测量，以深入了解该体系中胶体相互作用和控制分散的物理化学机制。在Ca改性的NaOH水溶液体系（CaCl-NaOH）中，当SNSFP用量为5 wt.%时，其对偏高岭土悬浮液的分散效果最为显著。此外，在分散于NaOH水溶液和SNSFP混合物中的偏高岭土中，Ca是提供分散效果最有效的碱土金属阳离子介质，而在KOH水溶液和SNSFP混合物中，Mg最为有效。胶体分散在高碱性环境中保持稳定，因此SNSFP可用于改善偏高岭土基碱激发体系的分散性。偏高岭土基水泥（如波特兰水泥混合物和碱激发水泥）胶体稳定性和流动性的建议机制，是通过双电层分布和结构的变化以及结构力来解释的，这是由于表面电荷密度和水化层的改变，促进了聚合物的竞争吸附。
