Recycling the product of thermal transformation of cement-asbestos for the preparation of calcium sulfoaluminate clinker

Our plain-English summary of Recycling the product of thermal transformation of cement-asbestos for the preparation of calcium sulfoaluminate clinker, by A. Viani, A.F. Gualtieri (Journal of Hazardous Materials, 2013).

The study

• Authors: A. Viani, A.F. Gualtieri
• Journal: Journal of Hazardous Materials
• Published: 2013;260:813-8
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

According to recent resolutions of the European Parliament (2012/2065(INI)), the need for environmentally friendly alternative solutions to landfill disposal of hazardous wastes, such as asbestos-containing materials, prompts their recycling as secondary raw materials (end of waste concept). In this respect, for the first time, we report the recycling of the high temperature product of cement-asbestos, in the formulation of calcium sulfoaluminate cement clinkers (novel cementitious binders designed to reduce CO₂ emissions), as a continuation of a previous work on their systematic characterization. Up to 29 wt% of the secondary raw material was successfully introduced into the raw mix. Different clinker samples were obtained at 1250 °C and 1300 °C, reproducing the phase composition of industrial analogues. As an alternative source of Ca and Si, this secondary raw material allows for a reduction of the CO₂ emissions in cement production, mitigating the ecological impact of cement manufacturing, and reducing the need for natural resources.

Copyright © 2013 Elsevier B.V. All rights reserved.

In plain English

This laboratory study, from the University of Modena and Reggio Emilia in Italy, tested whether cement-asbestos that had already been heat-treated (an 'inertization product') could serve as a raw ingredient for calcium sulfoaluminate cement clinker. Two heat-treated samples, called CAT1 and CAT2, made up 29 and 22 percent by weight of two raw mixes. The mixes were fired at 1250 °C, and one mix was also fired at 1300 °C. The authors measured the minerals formed using X-ray diffraction and electron microscopy. The main cement mineral, ye'elimite, made up 41.6, 62.5 and 65.4 percent by weight of the three clinkers. The authors described the 62.5 percent value as nearly equal to commercial cements. Periclase stayed below 2 percent. The authors calculated that the calcium from CAT1 and CAT2 equalled about 25.5 and 20.3 percent by weight of calcite (limestone). They said testing how the cements perform was beyond the scope of the work. The authors stated that using the already-inertized material eliminates health risks during cement manufacturing.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: laboratory materials experiment: preparation of cement clinkers and analysis of their mineral composition by X-ray powder diffraction and scanning electron microscopy
• Who was studied: two samples (CAT1 and CAT2) of the heat-treated product of cement-asbestos, previously characterized by the authors, used in two raw mixes; three clinker samples were produced (samples 1 and 2 at 1250 °C, sample 3 from Mix2 at 1300 °C)
• Exposure: not a human exposure study; the material studied was the high-temperature transformation product of cement-asbestos (asbestos fiber types not specified in the main text), mixed with reagent-grade calcite, gypsum and gibbsite
• Main results:
  • Mix1 contained 29 wt% CAT1 and Mix2 contained 22 wt% CAT2
  • Ye'elimite made up 41.6 wt% of clinker sample 1, 62.5 wt% of sample 2 and 65.4 wt% of sample 3
  • The authors described the 62.5 wt% ye'elimite in sample 2 as nearly equal to the commercial CSA cements they used for comparison
  • Periclase was below 2 wt% in all clinkers; magnesium-bearing phases were present because of the magnesium in the cement-asbestos product
  • Free lime was 9.2 wt% in sample 1 and 3.9 wt% in sample 2, and it disappeared in sample 3, which was fired at the higher temperature
  • The amorphous (non-crystalline) fraction was 11 wt% in sample 1, 7.2 wt% in sample 2 and 12 wt% in sample 3
  • The calcium supplied by CAT1 in Mix1 and by CAT2 in Mix2 equalled about 25.5 wt% and 20.3 wt% of calcite, respectively
• The authors' conclusion: The authors concluded that typical CSA clinker compositions were reproduced, and they stated that health risks during cement manufacturing are eliminated by using the already-inertized cement-asbestos in the raw mixes
• Limitations the authors state:
  • The performance (hydraulic behaviour) of the clinkers was not investigated
  • The amorphous fraction probably differs in composition from that of common CSA clinkers, so no definitive conclusion on hydraulic behaviour could be drawn

Topics

Medical terms in this study, explained in our Lexicon: Asbestos-Containing Material (ACM).

Related studies

• In vitro biodurability of the product of thermal transformation of cement-asbestos — A.F. Gualtieri, A. Viani, et al. (2012)
• Recycling of the product of thermal inertization of cement-asbestos for various industrial applications — A.F. Gualtieri, C. Giacobbe, et al. (2011)
• The transformation sequence of cement-asbestos slates up to 1200 degrees C and safe recycling of the reaction product in stoneware tile mixtures — A.F. Gualtieri, C. Cavenati, et al. (2008)
• In situ ESEM study of the thermal decomposition of chrysotile asbestos in view of safe recycling of the transformation product — A.F. Gualtieri, M.L. Gualtieri, et al. (2008)
• Crystal chemistry of the high temperature product of transformation of cement-asbestos — A. Viani, A.F. Gualtieri, et al. (2013)
• The thermal transformation of Man Made Vitreous Fibers (MMVF) and safe recycling as secondary raw materials (SRM) — A.F. Gualtieri, E. Foresti, et al. (2009)

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