Mechano-chemical activation of kaolins – Effect of mineral composition and triethanolamine on activation effectiveness and hydration
Tafadzwa Ronald Muzenda, Fabien Georget, Thomas Matschei
Abstract
The main technology currently in use for the activation of raw clays for use as SCMs is calcination (thermal activation). However, recent research is proving the viability of using mechano-chemical activation (MCA). In this paper, we study the effect that associated minerals in kaolins have on the effectiveness of MCA in the presence of triethanolamine (TEA), and the reactivity of MCA and calcined clays in ‘activated clay’ limestone cement at 50 wt% clinker substitution (ACLC-50). Results show that MCA efficiency is affected by the physical properties and kaolinite crystallinity of the raw clays. Calorimetry measurements showed faster early reactivity, which correlate to an increase in specific surface area (SSA). The intrinsic reactivity of MCA clays and TEA led to increased amounts of carboaluminate phases, low portlandite content and an increase in the clinker degree of hydration. Compressive strength comparable to calcined clays can be achieved at all ages for a kaolinite amorphization degree (KAD) of 74 %, while a KAD of 58 % gives 90 % at 28 d and equal strength at 90 d. This study not only shows that MCA clays can be successfully used in ACLC, but that MCA may be a better activation technique for raw clays with well-ordered kaolinite.