THE EFFECT OF REPEATED TEMPERATURE VARIATIONS AND FREEZE THAW PHENOMENON ON SOME DURABILITY ASPECTS OF CONCRETE.

The degradation of reinforced concrete structures is the result of numerous attacks due to the environment in which they live, which threatens the durability of this concrete. Among the parameters that affect the durability of concrete is the change in outdoor temperature, between day and night, summer and winter. This paper reflects the experimental work carried in order to better understand the effect of temperature variations on some durability aspects of an ordinary concrete frequently used in Morocco for bridges. To do this, samples of concrete were made, according to an ordinary formulation, to realize in the laboratory a program of tests which allowed us to determine the values of some durability parameters such as the porosity to water, the gas permeability, the electrical resistance and the chloride ion diffusion coefficient. The simulation of this variation in the laboratory is accelerated thanks to a temperature-controlled chamber according to 6 hours long cycle which is repeated and which varies in the range -5 to 40 ? C reflecting the Moroccan climate. Although 300 temperature variation cycles have relatively little effect on standard concrete, results show that the shrinkage has begun only after 50 cycles along with a significant loss of mass. Also, its permeability has increased due to the repetitive temperature variations.