The effects of various levels of compressive stress fields on the deterioration rate and microcracking of plain concrete subjected to freezing and thawing.

Abstract

The results of this investigation indicate: 1. The deterioration rate in the lateral direction of the uniaxially prestressed members subjected to the deep-seated type of freeze-thaw damage increased as the level of the compressive stress field increased. 2. Under all levels of uniaxial compression, cracks formed parallel to the direction of the applied stress field and in any plane parallel to this direction when the members were subjected to freeze-thaw damage. 3. The cracks are assumed to start at the boundary of a capillary within the aggregate and propagate through the aggregate to the aggegate- mortar interface. 4. Due to previous investigations, bond and mortar cracks are assumed to exist in the concrete. These cracks increase for increasing stress levels. 5. For the prestressed direction of any uniaxially prestressed member, there was a certain prestress level for which the change in length due to internal freeze-thaw damage equaled the change in length due to the applied prestressing force plus any longitudinal creep effects. This resulted in a total zero change in length. This zero change in length condition is called the "stress equilibrum condition" and the level of prestress which causes this condition is called the "prestress stability level." However, this condition can only last a short while before equilibrium is destroyed, since freeze-thaw daamage and and creep are continuously changing.