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Research project VLA11-4.1 Geological and structural characteristics of the Diestiaan iron sandstone with the aim of its use in the restoration of historic buildings.

Book - Report

There are numerous NO-ZW-oriented hills in the Hageland that contain petrified iron sandstone banks. This iron sandstone belongs to the formation of Diest and is characterized by a great diversity of composition, quality and durability. The Diestian iron sandstone was used in numerous monumental buildings in the Hageland, which led to a typical building style in the late Middle Ages: the Demergothic style. To this day, the quality and durability aspects of Diestiaan iron sandstone are still being considered.
usually approached on the basis of a visual assessment of the conservation status on the one hand and individual material-technical preliminary examinations, often carried out in the context of the possibility of a conservation treatment on the other hand, possibly supplemented with an earlier
limited and non-systematic evaluation of the petrographic characteristics. Technical quality criteria based on physical and mechanical characteristics, and their relation to the mineralogical characteristics, necessary as an indication of the aspect of usefulness as a building block in function of the application (parement, plinth, drip grid, capstone, ...) are as yet non-existent.
More and more, monuments built in Diestiaan iron sandstone are confronted with a significant loss of surface material on the one hand and the technical difficulty to realize a preservation treatment in case of strong silting on the other hand, from which follows the need for replacement. Moreover, with regard to the "replacement" aspect, this heritage is confronted with the problem of limited available reserves, which often requires the use of alternative types of iron sandstone, the nature and aesthetics of which differ from those of the authentic building block.
This report describes the results of a study carried out into the geological and material-technical characteristics of Diestiaan iron sandstone in order to evaluate its use in the restoration of historic buildings. This study was carried out by the Royal Institute for Cultural Heritage (KIK), with the Scientific and Technical Centre for the Construction Industry (WTCB) as subcontractor, on behalf of the Flemish Government, Department of Environment, Nature and Energy, Department of Land and Soil Protection, Subsoil, Natural Resources (ALBON). Based on the study of the Flemish Institute for Technological Research (VITO) and the Belgian Geological Service (BGD) on the natural occurrence of Diestiaan iron sandstone (Dreesen et al. 20101 ), the archival research of the Agency for Immovable Heritage and consultations with
The Agency for Nature and Forests and the Agency for Roads and Traffic were selected by the applicant to carry out core drilling at 5 typing locations prior to current research. The core drill rigs at Herent, Pellenberg, Rotselaar and Wezemaal (see below) were lifted in the spring of 2011, while for Diest this took place during the execution of current research, more specifically in the autumn of 2012. The drill cores lifted from the first four sites had previously been described by the BGD in terms of "suitability or quality class" ranging from class I (solid iron sandstone) to III (low-cohesive iron-containing sand or clay). The drill cores
of the 5 selected sites were made available by the client for the study.
The aim of this study is to characterise the Diestiaan iron sandstone from the 5 sites in order to evaluate its suitability as a building block.
In addition, the assignment included the formulation of a hypothesis on the geological occurrence of layers of structurally suitable iron sandstone in the hills of the Hageland. The geological study of the Diestiaan iron sandstone cores therefore had to gain insight into the occurrence of iron sandstone banks and to map in detail the material-technical characteristics of the iron sandstone. The correlation between the various results should also provide a clear picture of the occurrence of iron sandstone banks, so that it is possible to gain insight into their possible application in the restoration of historic buildings at other locations where Diestiaan iron sandstone is found.
The research was followed up and adjusted by a steering and sounding board group consisting of experts from the Flemish government (LNE Department - ALBON Department, Mobility and Public Works Department (MOW) - Geotechnical Department, Agency for Nature and Forests (ANB), Agency for Roads and Traffic (AWV) and Agency for Immovable Heritage), The Belgian Geological Service (BGD), the Regional Landscape of Northern Hageland, the Scientific and Technical Centre for Construction (WTCB), the University of Ghent (UGent), the Catholic University of Leuven (KULeuven), the Flemish Institute for Technological Research (VITO) and the KIK were represented.
Number of pages: 426
Publication year:2013