Splitting of Roofing Slates: Analysis of the Process Based on SEM, TMA, TG/DSC, and XRD
Publication: Journal of Materials in Civil Engineering
Volume 29, Issue 9
Abstract
Manufacturers reported a loss in fissility in blocks of roofing slates because of air exposure prior to splitting. Samples of three varieties of commercial Spanish roofing slate were subjected to freezing, water saturation, and exposure to air at different temperatures, simulating the conditions that blocks of slate may be subjected to during quarrying. Split samples, thin polished sections, and dust samples were obtained from these blocks and studied via scanning electron microscopy (SEM), thermomechanical analysis (TMA), X-ray diffraction (XRD), and thermogravimetry/differential scanning calorimetry (TG/DSC) under a heating ramp and/or constant temperature conditions. Backscattered electron images show that split surfaces avoided porphyritic quartz elements and propagated primarily in the rock matrix, along the contact zones between phyllosilicate crystallites, but not in their interlayer spaces. The Si-OH groups located on the phyllosilicate surfaces were involved in these processes. Their condensation, which facilitated dewatering from the rock at room temperature, simultaneously led to a shrinkage of the slate perpendicular to schistosity () and a loss in fissility.
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Acknowledgments
This study was supported by Project LE289A11-2, funded by the Junta de Castilla y León. The authors are also very grateful to the manager and technical staff of the Cupa Group and Pizarras Campo S.A., for authorizing this study. The authors likewise acknowledge the contributions of doctors José R. García, Begoña Fernández, Serguei Khainakov and Santiago García-Granda (University of Oviedo, Spain) and Dr. Sara Alcalde (University of León, Spain).
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Information & Authors
Information
Published In
Journal of Materials in Civil Engineering
Volume 29 • Issue 9 • September 2017
Copyright
©2017 American Society of Civil Engineers.
History
Received: Aug 4, 2016
Accepted: Jan 10, 2017
Published ahead of print: Apr 14, 2017
Published online: Apr 15, 2017
Published in print: Sep 1, 2017
Discussion open until: Sep 15, 2017
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