INFLUENCE OF THE PROPERTIES OF POROUS-MED IA ON THE FROST-RESISTANCE OF CALCAREOUS ROCK

The frost susceptibility is a limiting factor for calcarous materials used as aggregates (pavements, concrete) or as rockfill. Its evaluatio n is made difficult by-the complexity of the porous medium for these m aterials that are very often out of the range of present standard test s. The analysis of water freezing mechanisms at the pore scale and the determination of the resulting stresses has. been coupled with labora tory experiments (freezing conditions have been simulated in a thermal ly controlled room, and the damage has been monitored by ultrasonic wa ve damping measurements). A physical model is proposed for the freezin g behaviour of calcarous rocks that depends on the geometry of the por ous constituents. The comparison of this model with test results eithe r normalized or recommended for aggregates and rockfill shows that the latter are too severe for calcarous materials. Test procedures should be modified to better represent the conditions of saturation and temp erature prevailing in structures that includes this type of material a nd to take into account the complexity of the calcarous porous medium.