Experimental study of accelerated leaching on hollow cylinders of mortar

Two mortars, differencing mainly in their initial porosity, were degraded by the use of a chemically accelerated process with ammonium nitrate solution. To specifically study the leached material, the chemical attack was undertaken on thin walled tubes. The leaching effects were evaluated by studying variations in mechanical and hydraulic properties. For both mortars tested, the kinetics of relative loss in strength, in elastic modulus and of increase in permeability were similar. For the same time of degradation, the increase in porosity and the loss in volumetric mass roughly depend on the estimated cement paste proportion of each mortar. The total process of degradation was carried out in three steps: 4, 8 and 16 days. Very sharp variations of all the studied properties were observed until 8 days of leaching followed by a plateau. These two phases are attributed to Portlandite dissolution first then to progressive C–S–H decalcification. At the end of the leaching test, a permeability increase of more than two orders of magnitude and a loss in strength and elastic modulus of more than 85% were observed for both mortars.