Methodology to evaluate variations in concrete color caused by white cement substitutions and forming materials
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ORIGINAL ARTICLE
Methodology to evaluate variations in concrete color caused by white cement substitutions and forming materials Wael A. Megid . Kamal H. Khayat
Received: 7 December 2019 / Accepted: 30 September 2020 Ó RILEM 2020
Abstract An experimental program was conducted to develop a methodology to quantify the gradation of the concrete color. The proposed methodology was used to evaluate the effect of the supplementary cementitious materials and the limestone filler used as partial substitution of white cement in architectural precast concrete. The effect of the formwork materials on concrete color was also investigated. Conventional concrete mixtures were prepared using different binder types, including gray-high early strength cement, white cement, limestone filler, blast-furnace slag, and metakaolin, to evaluate the compressive strength development that are suitable for the precast architectural applications. The corresponded paste mixtures were prepared to evaluate the variations in concrete color with the time under the air-curing conditions. The proposed methodology was found to provide precise classification for color gradation of concrete. The ternary powder blend of 50% high early W. A. Megid (&) Universite´ de Sherbrooke, Sherbrooke, QC, Canada e-mail: [email protected] W. A. Megid Menoufia University, Shebeen Elkom, MNF, Egypt K. H. Khayat Missouri University of Science and Technology, Rolla, MO, USA e-mail: [email protected]
strength cement, 25% white cement, and 25% high Blaine limestone filler, by mass, was found to be optimal to achieve reasonable white tint in compensation with the need to retain high early strength. A superworkable concrete and two self-consolidating concrete mixtures were cast in a special Z-shaped mold built up using PVC, steel, plywood, and polyester filter liner. The color of concrete surfaces cast in the plywood and polyester filter lined formwork materials were found darker than that of the concrete cast in the PVC and steel formworks. Keywords Architectural concrete Color Limestone filler Metakaolin Slag Strength Surface quality
1 Introduction Ensuring uniform surface quality and appearance including color is vital in architectural concrete [1]. The proper selection of color for architectural precast concrete is essential to achieve a successful aesthetic appearance. Reference color plates and samples development are used at the precast concrete plant for color selection [2]. The color of smooth concrete finish surface is primarily influenced by the characteristics of the binder system. The inherent color of the binder system varies from grey to white, depending on the chemical composition of the cement and
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supplementary cementitious materials (SCMs) or fillers in use. The use of finely ground cement can result in lighter color than coarsely ground cement [2]. The color of grey cement concrete is more sensitive to the changes in water content, curing regime, temperatures, h
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