Effects of organic additives on calcium hydroxide crystallisation during lime slaking

Pesce, Cecilia, Pesce, Giovanni, Molinari, Marco and Richardson, Alan (2020) Effects of organic additives on calcium hydroxide crystallisation during lime slaking. Cement and Concrete Research. ISSN 0008-8846 (In Press)

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Abstract

Organic compounds, often used in cement as admixtures, may affect the crystallisation and carbonation kinetics of Ca(OH)2, an important phase of hydrated cement. Here, we investigated changes in Ca(OH)2 morphology in the presence of 3 organic compounds, commonly encountered in cementitious materials: sucrose, pectin and calcium lignosulfonate. The additives were introduced either before or after lime slaking to determine the influence of temperature. Ca(OH)2 crystals and supernatant solutions were characterised at time of slaking and after 6 months of ageing using scanning electron microscopy, X-ray diffraction and optical emission spectroscopy.Our results indicate that the morphology of Ca(OH)2 crystals is modified by the characteristics of the organic molecules which promote formation of Ca(OH)2 with habits that can result in faster carbonation, an effect that is detrimental to cement used in reinforced concrete. These effects are enhanced when the additives are introduced before slaking, likely as a result of thermal degradation.

Item Type: Article
Uncontrolled Keywords: Lime, sucrose, Calcium lignosulphonate, Portlandite, crystal morphology
Subjects: H700 Production and Manufacturing Engineering
K100 Architecture
K200 Building
K900 Others in Architecture, Building and Planning
Department: Faculties > Engineering and Environment > Architecture and Built Environment
Depositing User: Rachel Branson
Date Deposited: 05 Oct 2020 10:58
Last Modified: 12 Oct 2020 14:29
URI: http://nrl.northumbria.ac.uk/id/eprint/44400

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