Mara- Project. Developing long-term durability of marble facades
Jouni Maidell, Project Engineer, Helsinki Public Works Department
Mara -project started during the renovation project of Finlandia Hall. The purpose of the
project is to find out the reasons and mechanisms for the deterioration and curving of the
thin marble panels. In addition to this the possibilities to extend the lifetime of marble
coated, ventilated façades are studied. The problem has been studied by field tests on the
roof of the Finlandia Hall in Helsinki, Finland and by laboratory tests carried out by several
European laboratories. The project started 4.1.1999 and will be finished by the end of
April 2001.
Materials for the study were selected to represent all the Carrara Bianco varieties.
Selection was limited to those qualities suitable for use in Finlandia Hall. Also three
different granites were involved for comparison.
Field tests
The behaviour of marble structures consisting of thin stone panels has been followed in
actual circumstances. Matters to be studied are the impact of marble panel thickness,
stone panel size and initial stone strength on the durability of marble and coating structure.
Also the curving and changes in colour have been measured. The actual weather
conditions i.e. humidity, temperature and the composition of the air by the wall are followed
very closely.
Laboratory tests
The alteration of the material properties under different thermal, climatical and chemical
stresses have been studied in the laboratory. The properties studied are microstructure;
possible decohesion of calsite grains, behaviour of the mircocracks, soundness of the
materia. Also alteration of different mechanical and physical properties have been studied.
Results
After intensive studies it seems that there are significant differences in behaviour
depending on the microstructure of marble in question. It seems very likely that those of
xenoblastic texture are more tolerate against climatical stresses than those of homoblastic
texture.
Partners
Participants of the project are Stonecon Oy, Finland, Technical Research Centre of
Finland (VTT), Helsinki University of Technology, Parma University, Cevalor in Portugal,
Internazionale Marmi e Macchine in Italy and different companies in Italy, Sweden and
Finland.
