hrvatski

Microstructure of cement paste incorporating low grade calcined clay

Considering the availability of resources, clays represent the most promising environmental alternative for replacing cement in large quantities worldwide. While kaolinite is the most reactive clay mineral for use in cements, natural clays are often composed of a mixture of different and less reactive minerals. Understanding the microstructural development of cement blends containing locally available low-grade kaolinite clay is critical to the potential use of this material on industrial scale. This study analyses and compares the hydration of cement mixtures containing fly ash, calcined clay, and limestone during prolonged curing (365 days). A systematic experimental study was conducted at the paste level to determine the evolution of hydration products in systems with high volume cement replacement. Microstructural analysis including thermogravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) was used to analyze the difference in phase assemblage. The changes in the reaction phases, particularly the AFm phases (hemicarboaluminate and monocarboaluminate), were then related to the compressive strength and durability of the mortar.

Limestone calcined clay, SCM, hydration, cement paste, compressive strength

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