Probabilistic evaluation of the durability of ready mix mortars on the maintenance of historic masonry

One of the main causes of deterioration of masonry surfaces in aggressive environment is the salt decay; the phenomenon is emphasized by the presence of the mortar joint, faster vehicle of the salts. In case of surface damages re-pointing mortar mix is frequently used and the durability of the intervention depends on the quality of the new mortar. To investigate the durability of different mix mortars for the maintenance of historic masonry, according to RILEM Recommendations MS-A1 crystallization tests were carried out on masonry specimens built with the same type of bricks and different types of mortar mix. The parameter assumed as significant measure of material deterioration process is the loss of surface materials. The measure has been made with a laser profilometer over time. The great randomness connected with the environment critical attacks, suggests studying the deterioration under a probabilistic point of view, Following this way, the deterioration process of the masonry samples was approached as a stochastic process of the random variables  (where  is the loss of surface material at each laboratory test cycle). The modelling adopted is the fragility curves modelling developed by the authors to analyze this kind of problems.