Scientific Aspects of Kaolinite Based Coal Mining Wastes in Pozzolan/Ca(OH)₂ System

Abstract

The transformation process of the natural kaolinite into metakaolinite for its use as a cement addition was very much known long time ago. However, environmental policies prioritize the waste recycling as raw material by its environmental benefits. This article reports, for the first time, the scientific aspects related to the recycling of three Spanish coal mining wastes of different nature and origin, as an alternative source to obtain future pozzolans based on metakaolinite. The effect of activation conditions on the mineralogy, as well as the formation and evolution of hydrated phases formed during the pozzolanic reaction, was analyzed using different instrumental techniques such as X‐ray fluorescence, X‐ray diffraction, thermogravimetric analysis, infrared spectroscopy, and scanning electron microscopy. The results showed that all activated coal mining wastes exhibited high pozzolanic activity. The identification and evolution of hydrated phases with the hydration time in activated kaolin/Ca(OH)2 system were directly related to the origin and nature of the starting coal mining waste and not to the activation temperature itself. Finally, the coal mining wastes are suitable for being used as future pozzolans.

Effect of metakaolin addition and seawater mixing on the properties and hydration of concrete

“…Previous study showed the formation of hemicarboaluminate and monocarboaluminate in paste containing 30 wt.% MK and 15 wt.% limestone, while significant amount of limestone remained in the paste (Antoni et al, 2012). Other studies indicated the formation of monocarboaluminate in pastes containing MK and lime (Frias and Cabrera, 2001;Zibara et al, 2008;Aggelakopoulou et al, 2011;Frias et al, 2012;Gameiro et al, 2012;Tironi et al, 2013). In this study, the formation of hemicarboaluminate and monocarboaluminate is thermodynamically feasible through the carbonation of specimen by CO 2 in the atmosphere (Duan et al, 2012).…”

Paper sludge, an environmentally sound alternative source of MK-based cementitious materials. A review

“…The social and economic impact of metakaolinite production has prompted the publication of many studies on alternative sources of this pozzolan [7][8][9]. Paper manufacture, like any other industry, generates huge volumes of different types of waste, classified in the European List of Waste (ELW).…”

Characterization of Moroccan coal waste: valorization in the elaboration of the Portland clinker

“…Some of these studies are interested in their use in the field of civil engineering. Frias et al [2] [3] are interested on pozzolan properties of coal waste. They study the activation of kaolinite, contained in coal mining waste, to metakaolinite which can be an alternative source to obtain pozzolans .…”