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Traditional mortars with burned alum shale as artificial pozzolan



Title: Traditional mortars with burned alum shale as artificial pozzolan
Author(s): S. Johansson, J.E. Lindqvist
Paper category : conference
Book title: 2nd Conference on Historic Mortars - HMC 2010 and RILEM TC 203-RHM final workshop
Editor(s): J. Válek, C. Groot and J.J. Hughes
Print-ISBN: None
e-ISBN: 978-2-35158-112-4
Publisher: RILEM Publications SARL
Publication year: 2010
Pages: 239 - 246
Total Pages: 8
Nb references: 13
Language: English


Abstract: From the mid-18th century extensive research in Sweden and in present day Finland was focused on the development of mortars with hydraulic and pozzolanic properties. The results were mainly published by the Royal Swedish Academy of Science. The aim was to replace the imported Italian pozzolan and Dutch trass with a pozzolan produced in Sweden. Several products based on burned alum shale were developed. Cambrian alum shales with a high content of bitumen were fired without additional fuel in order to produce pozzolanic shale ash. The bituminous alum shale was used directly as fuel in the lime burning process from the late 18th century. The alum shale mortars have a red-brown colour due to the high content of iron oxides. The mortars are hard, strong and generally have good durability both as masonry mortars and renders. Microscopic analysis shows that often only a skeleton remains of the shale particles and that a large part of the particles has been consumed by the pozzolanic reaction. The field of application was initially mainly structures in contact with water, such as locks in canals and harbours, but building construction was also an early application.


Online publication: 2010-10-25
Publication type : full_text
Public price (Euros): 0.00