concrete under different accelerated test conditions Mario Berra*, Giorgia Faggiani*, Teresa Mangialardi**, Antonio Evangelista Paolini** 5th International Conference on Dam Engineering Lisbona, 14-16 Febbraio 2007 * CESI RICERCA ** UNIVERSITA’ DI ROMA LA SAPIENZA The leaching behaviour of laboratory cement mortar and concrete was investigated using two different leach tests, an ultra-accelerated test with concentrated ammonium nitrate solution (590 g/l NH4NO3) and a long- term test with deionised water at a constant pH of 3.5. An application of the ultra-accelerated leach test to the case study of an Italian concrete dam was also attempted. Mortar and concrete specimens were characterised for their density, total porosity, compressive strength, and portlandite content. It was found that, irrespective of the type of material and leach test investigated, there exists a linear relationship between the leached shell depth and the square root of leach time. Very similar relationships are obtained when mortar and concrete samples characterised by the same composition with regard to cement paste are subjected to the same leaching test. The ammonium nitrate leach test proves to be a rapid and reliable method for leaching studies on cement-based materials. A simple leaching model based on the use of an empirical parametric equation is able to correlate the changes in the leached shell depth with leach time, as a function of the chemical composition of the material and the environmental leaching conditions. Keywords: mortar, concrete, dam, leaching, ammonium nitrate leach test, deionised water leach test