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Title: Pozzolanic Reactivity and Performance of Calcined Byproduct Clays of Various Kaolinite Contents in Concrete Mixtures

Author(s): Khashayar Jafari

Publication: Web Session



Appears on pages(s):



Date: 10/17/2021

In this study, byproduct clay samples from a commercial sand and gravel pit in United States was investigated. QXRD testing showed that after calcination, the clays contained quartz in the range 29 to 60%, muscovite 10 to 13%, hematite 3 to 7.5%, and amorphous 28 to 49.5%. Additionally, surfactant-assisted sedimentation of the low kaolinite clay prior to calcination resulted in an enriched calcined clay with 2% quartz, 26% muscovite, 6% hematite, and 64% amorphous. These three clay samples were evaluated for their chemical and physical properties (per ASTM C311 and C618) and pozzolanic reactivity (per ASTM C1897, the R3 test). XRD and thermodynamic modeling were used to identify and quantify the pozzolanic reaction products. Further, the performance of these clays in a concrete mixture with w/cm=0.47 was evaluated by measuring the impact on workability, setting, compressive strength, and durability (ASR mitigation, drying shrinkage, chloride penetrability, and scaling resistance). Given that the three clays were from the same source and of similar chemistry, the results allow evaluating the impact of the kaolinite content on the reactivity and performance of such calcined clays in concrete.