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        Preparation and polymeric encapsulation of powder mineral pellets for self-healing cement based materials

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        Author
        Alghamri, Rami
        Kanellopoulos, Antonios
        Litina, Chrysoula
        Al-Tabbaa, Abir
        Attention
        2299/20543
        Abstract
        Using mineral additives and admixtures as self-healing agents in cement-based composites has been extensively researched. However, if the minerals are added directly to the cementitious matrix without any protection, they could immediately react, leading to a decrease in self-healing efficiency with further associated side-effects on the mechanical properties of cementitious composites. Thus, this paper describes the development of coated pellets as a self-healing system in cement based materials. Pan pelletisation was utilised for producing pellets from three different powder minerals as potential healing agents: reactive magnesium oxide (MgO), silica fume and bentonite. Of these materials, two types of developed prototype pellets in addition to another two commercial types of MgO pellets with different pellet sizes were then encapsulated in a polyvinyl alcohol (PVA) based film coating. The PVA coating was evaluated for the apparent solubility in water and in alkaline solution, swelling property, water permeability, dynamic mechanical properties, and shell thickness on pellets. Although PVA coating exhibited a decrease in its mechanical properties in water or in the simulated concrete environment, it retained integrity and stability in both environments. The PVA shell thickness varied from 10 to 50 µm. As the coated pellets partially replaced the natural sand in mortar mixtures, they were characterised in comparison with sand for the particle size distribution, density, porosity, crushing strength and particle shape. Experimental results indicated that the different types of pellets showed higher porosity and lower crushing strength compared to sand. In mortar mixtures, the pellets showed excellent compatibility with minimal influence on the fresh mixture properties and the compressive strength of the hardened specimens. This was accompanied by good distribution inside the concrete matrix. Further investigations on the self-healing performance of these pellets are under way.
        Publication date
        2018-10-20
        Published in
        Construction and Building Materials
        Published version
        https://doi.org/10.1016/j.conbuildmat.2018.07.128
        License
        http://creativecommons.org/licenses/by-nc-nd/4.0/
        Other links
        http://hdl.handle.net/2299/20543
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