Grinding Test on Tremolite with Fibrous and Prismatic Habit

Oliviero Baietto,Mariangela Diano,Paola Marini,Giovanna Zanetti

doi:10.3390/fib7060052

Oliviero Baietto, Mariangela Diano + Show 2 more

Open Access

https://doi.org/10.3390/fib7060052

Copy DOI

Journal: Fibers	Publication Date: Jun 1, 2019
Citations: 3	License type: CC BY 4.0

Affiliation: Polytechnic University of Turin

Abstract

The main objective of this work is the evaluation of the morphology change in tremolite particles before and after a grinding process. The crushing action simulates anthropic alteration of the rock, such as excavation in rocks containing tremolite during a tunneling operation. The crystallization habit of these amphibolic minerals can exert hazardous effects on humans. The investigated amphibolic minerals are four tremolite samples, from the Piedmont and Aosta Valley regions, with different crystallization habits. The habits can be described as asbestiform (fibrous) for longer and thinner fibers and non-asbestiform (prismatic) for prismatic fragments, also known as “cleavage” fragments. In order to identify the morphological variation before and after the grinding, both a phase contrast optical microscope (PCOM) and a scanning electron microscope (SEM) were used. The identification procedure for fibrous and prismatic elements is related to a dimensional parameter (length–diameter ratio) defined by the Health and Safety Executive. The results highlight how mineral comminution leads to a rise of prismatic fragments and, therefore, to a potentially safer situation for worker and inhabitants.

Highlights

The object of this study is tremolite, a hydrated calcium magnesium silicate (Ca2 Mg5 Si8 O22 (OH)2 ), belonging to the tremolite-ferro-actinolite series [1,2], with an amphibolic structure characterized by long and parallel double chains of silica tetrahedral (SiO4 ) with a strip of cations located between the double chains [2,3,4,5,6].Tremolite and actinolite can crystallize with two different crystalline habits and it is common to find them in fibrous habit, known as asbestiform, or in prismatic habit, non-asbestiform
The aim of this study was the evaluation and analysis of tremolite behavior submitted to anthropic mechanical actions, which subsequently contribute to the release of fibers into the environment
It is important to underline that tremolite in nature can be present in two crystalline habits: asbestiform or non-asbestiform

Summary

Introduction

Tremolite and actinolite can crystallize with two different crystalline habits and it is common to find them in fibrous habit, known as asbestiform, or in prismatic habit, non-asbestiform. This distinction can be described as [7]: . “Asbestiform habit” is associated with a crystalline structure characterized by thin crystals similar to the morphology of organic fibers (hair; the resemblance is not in the width, 10−6 m for asbestos fibers vs 10−5 m for hair) or as a crystalline aggregation consisting of parallel fibers (bundles with indented extremities). The fibers are thin, long, and similar to needle-shaped elements with a unidirectional growth [8].

Objectives

Methods

Results

Discussion

Conclusion