Missana Tiziana, Almendros-Ginestà Oscar, Colmenero Francisco, Fernández Ana María, García-Gutiérrez Miguel
CIEMAT, Nuclear Fission Department, Spain.
Heliyon. 2024 Aug 13;10(16):e36117. doi: 10.1016/j.heliyon.2024.e36117. eCollection 2024 Aug 30.
Ettringite is an important mineral that contributes to the overall performance of cementitious materials. Knowledge of the surface charge behaviour of a solid is necessary for a mechanistic description of surface processes such as adsorption or particle-particle interactions. The objective of this study was to develop a model capable of reproducing ettringite surface charge as a function of calcium, sulphate, and pH. Ettringite was synthesised and characterised using different analytical, microscopic, and spectroscopic techniques with the help of density functional theory. Electrophoretic mobility was measured using laser Doppler electrophoresis in alkaline waters representative of the cementitious environment. The behaviour of the ettringite surface charge was shown to be quite complex as sulphate and calcium acted in a competitive manner on the overall charge. The ζ-potential increases when the calcium content increases, whereas it decreases when sulphate increases. This is due to the possible adsorption of these ions at the surface, and the extent of the effect depends on the relative concentrations of Ca and SO . An electrostatic double layer model (DLM) was used to calculate the surface potential, considering the adsorption of both calcium and sulphate, as possible ions determining the potential (IDP), and formation of different complexes with ettringite surface functional groups (SOH). The variations of the ζ-potential could be satisfactorily predicted under the different chemical conditions of interest in a cementitious environment.
钙矾石是一种对胶凝材料整体性能有重要贡献的矿物。了解固体的表面电荷行为对于诸如吸附或颗粒间相互作用等表面过程的机理描述是必要的。本研究的目的是建立一个能够将钙矾石表面电荷再现为钙、硫酸根和pH值函数的模型。借助密度泛函理论，使用不同的分析、显微镜和光谱技术对钙矾石进行了合成和表征。在代表胶凝环境的碱性水中，使用激光多普勒电泳测量电泳迁移率。结果表明，由于硫酸根和钙对总电荷的竞争作用，钙矾石表面电荷的行为相当复杂。当钙含量增加时，ζ电位升高，而当硫酸根增加时，ζ电位降低。这是由于这些离子可能在表面吸附，且影响程度取决于Ca和SO₄²⁻的相对浓度。考虑到钙和硫酸根作为可能决定电位的离子（IDP）的吸附以及与钙矾石表面官能团（SOH）形成不同络合物，使用静电双层模型（DLM）来计算表面电位。在胶凝环境中不同的化学条件下，ζ电位的变化能够得到令人满意的预测。
