Deformation velocity survey in mortar and cement paste specimens subjected to external aggressive attacks

The durability of concrete depends not only on the composition of the material and its resulting porosity, but also on the environmental conditions. Contact between concrete or cement mortars with water and soils containing sulphates, of a natural, biological origin or deriving from pollution, can activate chemical reactions in the cement paste inducing an expansion and degradation of the concrete. To evaluate the behaviour of the cementitious material subjected to various external aggressive attacks, prismatic samples of cement paste and mortar samples produced with the same binder (Portland cement) were immersed in demineralised water and in various solutions containing 5% and 10% sodium sulphates. Their expansion was monitored over time by a direct length measurement. This paper shows the results achieved in a rather long laboratory investigation and a first hypothesis has been formulated on the possible expansion rate in the first 56 test days and in the following 850 days