Some considerations on the warping of marble façades: the example of Alvar Aalto’s Finland Hall in Helsinki

A scanning electron microscope study was performed on samples cored from the white-marble panels of Finland Hall’s façade which revealed considerable warping only a few years after the building’s completion. The analysis shows that granular decohesion is the most important sign of damage at the microstructural level. The presence of calcium sulphate is clearly recognisable on the façade’s surface, though it appears that chemical attack has failed to penetrate inside the material and, presumably, cannot thus be considered the only cause of decay. Following up on the results of other experimental observations that correlate warping with the degradation of bending strength, flexural tests were performed on four different qualities of white-marble, conditioned by thermal cycles in order to reproduce the damage process. The tests evidence that the four material types present very different resistance to thermal aggression: some varieties hold up very poorly, while others instead remain reliable in the long term.