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

Abstract

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/m 3 , a coarse aggregate fraction of 985 kg/m 3 , 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.

Designing Efficient Flash-Calcined Sediment-Based Ecobinders

“…It was concluded that flash-calcined clays improve workability, porosity, and creeping. Similar conclusions were stated by Sullivan et al [ 36 ], showing that MK contributes to prolonging the service life of infrastructures. Danilevich et al [ 37 ] activated thermally aluminum hydroxide in gibbsite using a reactor called TSEFLAR.…”

Modification of Kaolin with Carbon Quantum Dots as Composite for Methylene Blue Removal: Literature Review and Experiment

“…Previous studies have shown that increased SiO2 contents are expected when kaolin transforms into MK through heat treatment. The SiO2 contents can vary from 50 to 60%, sometimes reaching 74.3% (Fadzil et al, 2017;Pillay et al, 2020;Rashad, 2013;Sullivan et al, 2018). The remainder consists of kaolinite and a small amount of muscovite.…”

Use of a Piezoelectric Bender Element for the Determination of Initial and Final Setting Times of Metakaolin Geopolymer Pastes, with Applications to Laterite Soils

“…As such, metakaolin, which is basically made from kaolin (a type of clay) treated using a high calcination temperature [ 18 , 19 ], is considered to be one of the possible replacement materials. In spite of the calcination process necessary in metakaolin production, Sullivan et al [ 20 ], who reviewed the study by Selmani et al [ 21 ], stated that the manufacture of metakaolin involved much lower calcining temperatures and emitted less carbon dioxide than Portland cement. Therefore, metakaolin is gaining popularity in various construction applications, as mentioned in other studies [ 22 , 23 ].…”