How shearing affects air dissolution in fresh cement pastes under pressure

IF 3.9 3区工程技术 Q2 CONSTRUCTION & BUILDING TECHNOLOGY Materials and Structures Pub Date : 2025-02-08 DOI:10.1617/s11527-025-02593-1

Daniel Galvez-Moreno, Dimitri Feys, Kyle Riding

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Abstract

The air-void system of concrete is of paramount importance to ensure freeze–thaw durability. Pumping induces detrimental changes in the air-void system of concrete by dissolving the air bubbles in the surrounding water when pressure increases due to the pump action. This research work investigates the influence of shear rate and air-void size distribution on air dissolution with time of cement pastes under pressure. Steady-state shear rheology at different shear rates was applied on samples of different air-void size distributions but similar air contents. Due to the low capillary number of the mixtures, the application of pressure caused a decrease in viscosity. With increased applied shear rate and increased fineness of the air-void size distribution, the decrease in viscosity was more abrupt, indicating that the air dissolved almost immediately. Coarser air-void size distributions and lower shear rates caused a more gradual decrease in viscosity and thus a slower air dissolution. All experimental air dissolution times were lower than the calculated time needed for dissolution by pure diffusion. These results on the combined effect of pressure, duration, shear rate and air-void size distribution create the basis for a deeper understanding of the behavior of the air-void system of concrete during pumping.

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在压力下，剪切如何影响新鲜水泥浆中的空气溶解

混凝土的气孔系统对保证混凝土的冻融耐久性至关重要。由于泵的作用，当压力增加时，泵送通过溶解周围水中的气泡，引起混凝土空隙系统的有害变化。研究了受压水泥浆体剪切速率和气孔尺寸分布对空气溶解随时间的影响。对不同孔隙尺寸分布但空气含量相似的试样进行了不同剪切速率下的稳态剪切流变学研究。由于混合物的毛细数较低，施加压力导致粘度降低。随着施加剪切速率的增加和空隙尺寸分布细度的增加，粘度的下降更为突然，表明空气几乎是立即溶解的。较粗的气孔尺寸分布和较低的剪切速率导致粘度的逐渐下降，从而导致较慢的空气溶解。所有实验空气溶解时间均低于纯扩散溶解所需的计算时间。这些关于压力、持续时间、剪切速率和气孔尺寸分布的综合影响的结果为更深入地理解泵送过程中混凝土气孔系统的行为奠定了基础。

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来源期刊

Materials and Structures 工程技术-材料科学：综合

CiteScore

6.40

自引率

7.90%

发文量

222

审稿时长

5.9 months

期刊介绍： Materials and Structures, the flagship publication of the International Union of Laboratories and Experts in Construction Materials, Systems and Structures (RILEM), provides a unique international and interdisciplinary forum for new research findings on the performance of construction materials. A leader in cutting-edge research, the journal is dedicated to the publication of high quality papers examining the fundamental properties of building materials, their characterization and processing techniques, modeling, standardization of test methods, and the application of research results in building and civil engineering. Materials and Structures also publishes comprehensive reports prepared by the RILEM’s technical committees.