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The influence of sulfate availability on rheology of fresh cement paste
Applied Rheology ( IF 1.8 ) Pub Date : 2020-09-08 , DOI: 10.1515/arh-2020-0106
Willy Mbasha 1 , Rainer Haldenwang 1 , Irina Masalova 1
Affiliation  

Abstract Natural gypsum can degenerate into hemihydrate during cement clinker grinding which changes the physical and chemical properties of cement hydration, affecting therefore the fresh and hardened properties of cement based materials. Cement systems containing a constant total amount of calcium sulfate (4%) with relative proportions of hemihydrate and natural gypsum were considered. Rheological measurements were executed on an Anton Paar MCR51 rheometer to evaluate the flow properties of cement pastes. Results show that, the yield stress and the plastic viscosity of cement pastes were affected when the degeneration of natural gypsum exceeded 50%. Above this concentration, the yield stress remarkably increased and a variation in plastic viscosity of about 50% was observed. Using TG-DSC techniques, it was shown that, the amount of formed ettringite could not explain these rheological changes. However, centrifugational packing and SEM-SE measurements confirmed that, more than the amount of ettringite precipitated, ettringite morphology plays a major role in controlling the yield stress and plastic viscosity of fresh cement pastes.

中文翻译:

硫酸盐有效性对新拌水泥浆流变学的影响

摘要 天然石膏在水泥熟料粉磨过程中会变质为半水合物,改变水泥水化的理化性质,从而影响水泥基材料的新鲜和硬化性能。考虑了含有恒定总量硫酸钙 (4%) 和相对比例的半水合物和天然石膏的水泥系统。在安东帕 MCR51 流变仪上进行流变测量,以评估水泥浆的流动特性。结果表明,当天然石膏的变性超过50%时,水泥浆体的屈服应力和塑性粘度受到影响。高于此浓度,屈服应力显着增加,并且观察到塑性粘度变化约 50%。使用 TG-DSC 技术表明,形成的钙矾石的量不能解释这些流变学变化。然而,离心堆积和 SEM-SE 测量证实,除了钙矾石的沉淀量外,钙矾石形态在控制新鲜水泥浆体的屈服应力和塑性粘度方面起着主要作用。
更新日期:2020-09-08
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