Treatment and recycling of asbestos-cement containing waste

Our plain-English summary of Treatment and recycling of asbestos-cement containing waste, by F. Colangelo, R. Cioffi, M. Lavorgna, et al (Journal of Hazardous Materials, 2011).

The study

• Authors: F. Colangelo, R. Cioffi, M. Lavorgna, L. Verdolotti, L. De Stefano
• Journal: Journal of Hazardous Materials
• Published: 2011;195:391-7
• Cited by: 31 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The remediation of industrial buildings covered with asbestos-cement roofs is one of the most important issues in asbestos risk management. The relevant Italian Directives call for the above waste to be treated prior to disposal on landfill. Processes able to eliminate the hazard of these wastes are very attractive because the treated products can be recycled as mineral components in building materials. In this work, asbestos-cement waste is milled by means of a high energy ring mill for up to 4h. The very fine powders obtained at all milling times are characterized to check the mineralogical and morphological transformation of the asbestos phases. Specifically, after 120 min of milling, the disappearance of the chrysotile OH stretching modes at 3690 cm(-1), of the main crystalline chrysotile peaks and of the fibrous phase are detected by means of infrared spectroscopy and X-ray diffraction and scanning electron microscopy analyses, respectively. The hydraulic behavior of the milled powders in presence of lime is also tested at different times. The results of thermal analyses show that the endothermic effects associated to the neo-formed binding phases significantly increase with curing time. Furthermore, the technological efficacy of the recycling process is evaluated by preparing and testing hydraulic lime and milled powder-based mortars. The complete test set gives good results in terms of the hydration kinetics and mechanical properties of the building materials studied. In fact, values of reacted lime around 40% and values of compressive strength in the range of 2.17 and 2.29 MPa, are measured.

Copyright © 2011 Elsevier B.V. All rights reserved.

In plain English

This laboratory study tested whether grinding asbestos-cement roofing waste could destroy its asbestos so the powder could be reused in building materials. The waste came from the roof of an industrial building in the Naples area and contained about 12% chrysotile by weight. It was ground in a high-energy ring mill for 30, 120 and 240 minutes. After 120 minutes, infrared and X-ray tests no longer showed the chrysotile signals, and electron microscope images of the treated waste showed no fibres. Fibre levels in the air, monitored while the waste was handled, never exceeded the threshold limit. The milled powder was then mixed with lime and cured, and in several mixtures about 40% of the lime reacted. Mortars made with the 120-minute powder reached compressive strengths of 2.26, 2.29 and 2.17 MPa after 90 days. A reference mortar made with natural pozzolana reached 1.10 MPa. The authors concluded that the milled powders are asbestos-free and can be recycled in building materials. The study did not examine anyone's health.

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 experiment (materials study) on treating and recycling asbestos-cement waste by high-energy milling
• Who was studied: asbestos-cement waste removed from the roof of an industrial building in the industrial area of Naples, Italy; no people were studied; dates not given
• Exposure: asbestos-cement waste containing about 12% chrysotile by weight, milled in a ring mill for 30, 120 and 240 minutes
• Main results:
  • Infrared spectroscopy: the chrysotile OH signal at 3690 per centimetre disappeared after 120 minutes of milling
  • X-ray diffraction: the main crystalline chrysotile peaks practically disappeared after 120 minutes of milling
  • Scanning electron microscopy: the waste treated for 120 minutes showed no fibres
  • Air monitoring during handling and crushing of the waste: fibre concentration never exceeded the units per litre threshold limit
  • Specific surface area of the milled powders: 16.18, 23.95 and 18.92 square metres per gram after 30, 120 and 240 minutes of milling
  • Lime and milled-powder mixtures: reacted lime reached values around 40% (Table 4 shows 41.1 to 42.1% at 56 days in several systems)
  • Compressive strength after 90 days: 2.26, 2.29 and 2.17 MPa for the mortars with 50/50, 60/40 and 70/30 milled powder to lime
  • Reference mortar made with natural pozzolana: compressive strength 1.10 MPa after 90 days
• The authors' conclusion: The authors concluded that powders from high-energy milling of asbestos-cement waste are asbestos-free and can be recycled in building materials, and that two hours of milling is sufficient for total amorphization of the waste

Topics

Medical terms in this study, explained in our Lexicon: Asbestos-Cement, Chrysotile, Crystalline, Infrared Spectroscopy (IR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM).

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