Hydrated burnt clay-lime mixes: Effects of curing time and lime addition

Effects of hydration time (up to 28 days) and lime addition (≤ 20 wt.%) on the changes of the microstructure of a kaolinitic-illitic clay heated at 600 °C were investigated using X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy. Physical properties (strength, density, water absorption) of the cured blends were measured. The relations between properties and the operating factors were formulated using response surface methodology (RSM). Flocculation-agglomeration, carbonation and hydrate (C-S-H and CAH10) formation were the main happening transformations. The pozzolanic reactions involved metakaolin and to a lesser extent illite. Based on RSM results, both factors had positive effects on strength and their interactions were synergistic. However, they manifested opposite effects and significant antagonistic interactions on density and water absorption.