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Infrastructures 2018, 3(3), 17; https://doi.org/10.3390/infrastructures3030017

Sustainable Materials for Transportation Infrastructures: Comparison of Three Commercially-Available Metakaolin Products in Binary Cementitious Systems

College of Engineering, The University of Georgia, Athens, GA 30602, USA
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Received: 25 April 2018 / Revised: 9 June 2018 / Accepted: 19 June 2018 / Published: 21 June 2018
(This article belongs to the Special Issue Sustainable Transportation Infrastructures)
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Abstract

Metakaolin is the only major natural pozzolan to be specified for use as a supplementary cementitious material in the United States. As a result, the metakaolin market for concrete has grown dramatically in the past 20 years. As of now, the specifications of up to 16 state departments of transportation allow for the use of commercially-available and high-reactivity metakaolin products. However, to the best of the authors’ knowledge, no study has been performed to evaluate whether these products are comparable in their performance. Three commercially-available (U.S.) metakaolin products, each replacing 10%, 15%, and 20% of the cement content in concrete and mortar mixtures are studied. Concrete mixtures contained a cementitious content of 422 kg/m3, a coarse aggregate fraction of 985 kg/m3, and a water-to-cementitious ratio equal to 0.43. Varying levels of a superplasticizer were used to maintain a uniform workability between mixtures. Each mixture was subjected to the following tests: compression, split-cylinder tension, modulus of rupture, dynamic elastic modulus, rapid chloride-ion penetrability, alkali–silica reactivity, sulfate resistance, the coefficient of thermal expansion, and drying shrinkage. Benefits from the inclusion of metakaolin were highly product-dependent and include increases in mechanical strength. All metakaolin supplemented concrete mixtures benefitted from decreased permeability and increased resistance to chemical attacks, with the exception of the sulfate resistance of mortars including a metakaolin product with high fineness. The inclusion of any metakaolin at any replacement level increased the coefficient of thermal expansion of concrete specimens. Reasons for difference in performance between products are discussed, and predictors of quality are recommended. View Full-Text
Keywords: metakaolin; kaolin; supplementary cementitious materials; natural pozzolan; concrete; coefficient of thermal expansion; durability; slump; sulfate resistance; alkali silica reactivity metakaolin; kaolin; supplementary cementitious materials; natural pozzolan; concrete; coefficient of thermal expansion; durability; slump; sulfate resistance; alkali silica reactivity
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Sullivan, M.S.; Chorzepa, M.G.; Hamid, H.; Durham, S.A.; Kim, S.S. Sustainable Materials for Transportation Infrastructures: Comparison of Three Commercially-Available Metakaolin Products in Binary Cementitious Systems. Infrastructures 2018, 3, 17.

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