Environmental Factors affecting corrosion of steel inserts in ancient mansory

. Steel inserts are often present in ancient masonry in order to improve the structural behaviour of buildings or to prevent the propagation of cracks. The corrosion of inserts embedded in the materials of the masonry and consequently expansive phenomena may be harmful for the durability of the whole structure. This paper shows the results of a study on the corrosion behaviour of steel inserts in contact with mortar and/or bricks to simulate masonry structures. The effects of temperature and moisture on corrosion rate of steel and resistivity of both aerial and hydraulic mortars and brick specimens exposed in a climatic chamber to cycles of temperature (5-20-40°C) and relative humidity (65-80-95% and at saturation) are discussed. The results show that corrosion rate is negligible in specimens exposed to 65-80% RH (even at 40°C), whereas it reaches high values in wet environments or in the presence of water suction (in particular, in gypsum mortars). A correlation between electrical resistivity of embedding materials and corrosion rate of steel has been observed. In order to extend the results obtained on small-scale specimens at case studies that should consider the effect of the real hygrothermal conditions on corrosion of steel inserts in ancient masonry, numerical simulations have been also performed. The validation of these data by means of a bi-dimensional HMT model is now in progress.