Temperature-Induced Aggregation in Portlandite Suspensions.,Langmuir

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Temperature-Induced Aggregation in Portlandite Suspensions.
Langmuir ( IF 3.7 ) Pub Date : 2020-08-17 , DOI: 10.1021/acs.langmuir.0c01798
Sharu Bhagavathi Kandy _{1,

2} , Iman Mehdipour _{1,

2} , Narayanan Neithalath ₃ , Mathieu Bauchy _{2,

4} , Edward Garboczi ₅ , Samanvaya Srivastava _{2,

6} , Torben Gaedt ₇ , Gaurav Sant _{1,

2,

8,

9}

Affiliation

Laboratory for the Chemistry of Construction Materials (LC2), Department of Civil and Environmental Engineering, University of California, Los Angeles, California 90095, United States.
Institute for Carbon Management (ICM), University of California, Los Angeles, California 90095, United States.
School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, Arizona 86587, United States.
Laboratory for the Physics of AmoRphous and Inorganic Solids (PARISlab), Department of Civil and Environmental Engineering, University of California, Los Angeles, California 90095, United States.
Applied Chemicals and Materials Division, Material Measurement Laboratory, National Institute of Standards and Technology, Boulder, Colorado 80305, United States.
Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, California 90095, United States.
Department of Chemistry, Technische Universität München, Lehrstuhl für Bauchemie, Lichtenbergstrasse 4, 85747 Garching , Germany.
Department of Materials Science and Engineering, University of California, Los Angeles, California 90095, United States.
California Nanosystems Institute (CNSI), University of California, Los Angeles, California 90095, United States.

Temperature is well known to affect the aggregation behavior of colloidal suspensions. This paper elucidates the temperature dependence of the rheology of portlandite (calcium hydroxide: Ca(OH)₂) suspensions that feature a high ionic strength and a pH close to the particle’s isoelectric point. In contrast to the viscosity of the suspending medium (saturated solution of Ca(OH)₂ in water), the viscosity of Ca(OH)₂ suspensions is found to increase with elevating temperature. This behavior is shown to arise from the temperature-induced aggregation of polydisperse Ca(OH)₂ particulates because of the diminution of electrostatic repulsive forces with increasing temperature. The temperature dependence of the suspension viscosity is further shown to diminish with increasing particle volume fraction as a result of volumetric crowding and the formation of denser fractal structures in the suspension. Significantly, the temperature-dependent rheological response of suspensions is shown to be strongly affected by the suspending medium’s properties, including ionic strength and ion valence, which affect aggregation kinetics. These outcomes provide new insights into aggregation processes that affect the temperature-dependent rheology of portlandite-based and similar suspensions that feature strong charge screening behavior.

中文翻译：

硅酸盐悬浮液中的温度诱导聚集。

众所周知，温度会影响胶体悬浮液的聚集行为。本文阐明了具有高离子强度和接近颗粒等电点的pH值的波特兰（氢氧化钙：Ca（OH）₂）悬浮液的流变学对温度的依赖性。与悬浮介质（Ca（OH）₂在水中的饱和溶液）的粘度相反，发现Ca（OH）₂悬浮液的粘度随温度升高而增加。表现出这种行为是由于温度引起的多分散Ca（OH）₂聚集由于静电排斥力随温度的升高而减小。由于体积拥挤和在悬浮液中形成更致密的分形结构，悬浮液粘度的温度依赖性随颗粒体积分数的增加而减小。值得注意的是，悬浮液的温度依赖性流变响应显示出受悬浮介质特性（包括影响聚集动力学的离子强度和离子价）的强烈影响。这些结果提供了对聚集过程的新见解，这些聚集过程会影响基于波特兰石的悬浮液以及类似的悬浮液的温度依赖性流变，而悬浮液具有很强的电荷筛选行为。

更新日期：2020-09-15

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