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Minerals 2018, 8(4), 169; https://doi.org/10.3390/min8040169

Carbonation-Induced Mineralogical Changes in Coal Mining Waste Blended Cement Pastes and Their Influence on Mechanical and Microporosity Properties

1
Eduardo Torroja Institute for Construction Sciences (IETcc-CSIC), 28033 Madrid, Spain
2
Department of Geology and Geochemistry, Universidad Autónoma de Madrid, CSIC-UAM Associated Unit (Unidad Asociada CSIC-UAM), 28049 Madrid, Spain
3
Architectural Technology Department, Universitat Politècnica de Catalunya—Barcelona TECH, 08028 Barcelona, Spain
4
Institute for the Structure of Matter (IEM-CSIC), 28006 Madrid, Spain
*
Author to whom correspondence should be addressed.
Received: 12 February 2018 / Revised: 16 April 2018 / Accepted: 17 April 2018 / Published: 20 April 2018
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Abstract

The worldwide pursuit of new eco-efficient pozzolans is ongoing. Kaolinite-based waste is an eco-friendly source of recycled metakaolinite, a highly pozzolanic product. In this study, a blended cement paste containing 20% activated coal waste (ACW) was exposed to a 100% CO2 atmosphere at 65% RH for 7 days. The variations in its phase composition and strength were studied and compared to an OPC control. Both pastes were cured for 28 days prior to the carbonation test. Reaction kinetics were assessed using XRD, SEM/EDX, TG/DTG, FT-IR, Micro-Raman spectroscopy, pore solution pH and the cumulative carbonated fraction. The blended cement carbonated 68% faster than the control. While portlandite carbonation was the main reaction in both cements, decalcification was also observed (more intensely in the 20% ACW paste) in other hydraulic calcium phases (C-S-H gel, monocarboaluminate (C4AcH12), ettringite and tetracalcium aluminate (C4AH13). The end product of this reaction was calcium carbonate, mainly in the form of calcite, although traces of aragonite and amorphous carbonate were also detected. Compressive strength values rose with accelerated carbonation time and pore size reduction in both cement pastes. View Full-Text
Keywords: coal mining waste; blended cements; accelerated carbonation; mineralogy; properties coal mining waste; blended cements; accelerated carbonation; mineralogy; properties
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Frías, M.; de la Villa, R.V.; García, R.; Rodríguez, O.; Fernández-Carrasco, L.; Martínez-Ramírez, S. Carbonation-Induced Mineralogical Changes in Coal Mining Waste Blended Cement Pastes and Their Influence on Mechanical and Microporosity Properties. Minerals 2018, 8, 169.

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