Bowing of marble slabs: Evolution and correlation with mechanical decay

The bowing phenomenon is frequently a problem for newly constructed buildings, where marble slabs used in façades are usually very thin and have a high slenderness ratio. This kind of rock weathering can mainly be attributed to the intrinsic properties of the slab (petrography, dimensions), the anchorage techniques and the climatic conditions. Previous studies investigated marble with an equigranular-polygonal microstructure (granoblastic) and show they have a higher tendency to bow than those composed of anhedral (irregular) grains surrounded by subgrains (interlobate textures). The aim of this research was to study the correlation between the decrease in mechanical properties and the bowing in three types of marble with different textures and petrographic characteristics. This has been achieved through measurements of the bowing and the flexural strength, the water absorption and the ultrasonic pulse velocity at different stages of artificial ageing. As far as the granoblastic marble, with the progress of the artificial weathering, the tendency curve of bowing shows a sharp initial rise which subsequently proceeds more slowly. At the same time all the three types of marble (including xenoblastic marble, not subjected to bowing) showed a loss in mechanical resistance. Moreover, the flexural strength values matched well with the results of the non-destructive tests.