American Journal of Environmental Sciences 8 (2): 158-161, 2012 ISSN 1553-345X © 2012 Science Publications Corresponding Author: Bellopede Rossana, Department of Environment, Land and Infrastructures Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24-10129 Torino, Italy 158 The Effect of Water on The Strength of Building Stones Bellopede Rossana and Marini Paola Department of Environment, Land and Infrastructures Engineering, Faculty of Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24-10129 Torino, Italy Abstract: Problem statement: Water is one of the main causes of stone decay and the presence of water alone inside a stone could cause a decrease in its mechanical strength. In order to study the effect of water on the mechanical strength of stones, three Italian stones, which have historically been used for balconies, have been studied: Pietra di Luserna, Pietra Verde Argento and Pietra di Courtil. Approach: A comparison had been made between the effect of artificial ageing, by means of freeze and thaw cycles (where the increase in pores produced by iced water mechanically weakens the stone) and the effect of saturation on sound specimens subjected to flexural strength tests. Results: The results had shown that the three stones were very resistant to freeze and thaw cycles, but their mechanical strength decreases in wet condition. Conclusion/Recommendations: On the basis of the obtained results, it can be stated that mechanical strength values in wet conditions can be considered, in the planning of structural stonework for exterior use. As demonstration the case of a Pietra di Luserna balcony, where fault is occurred, a is reported. Key words: Influence of water, mechanical resistance, saturation INTRODUCTION It is known, in the scientific stone community, that water has a negative influence on materials in use (Fort, 2006; Chen et al., 2004; Winkler, 1994; Hudec, 1998): its effects can be seen not only on durability but also on the safe dimensioning of structures. In the last few years, there have been many cases of faults in stone modillions or stone balcony slabs (Fig. 1-3). These faults have mainly occurred in historical buildings and the involved stones have been used for centuries, normally with very good performances and resistance to decay. A database has been set up pertaining to 62 cases of stone balconies faults in Piedmont (Perino, 2008). This database reports the kind of stone and its conditions, the dimensional characteristics and the structure of the balcony. Almost all the standardized ageing methods used to simulate weathering on natural stones involve water, which, together with other factors, indirectly induces weathering: thermal shock (EN 14066: specimens cooling in water), freeze and thaw (EN 12371: iced water in stone pores), salt crystallization (EN12370: water carrying salt into the pores), resistance to thermal and moisture cycling (prEN 16306: the bottom of the specimen is set on a wet surface). However, the loss in mechanical strength for all these standardised ageing methodologies is evaluated using dried specimens subjected to the weathering cycles and comparing them with dried specimen in natural conditions. Fig. 1: The remains of a balcony in Pietra di Courtil Fig. 2: The broken balcony slab of Fig. 1