THERMAL PROTECTION OF CONCRETE DAMS SUBJECTED TO FREEZE-THAW CYCLES

Concrete dams located in northern regions are subjected to severe cycl ic seasonal temperature variations, which may contribute significantly to the deterioration of the exposed faces and the long-term degradati on of strength and stiffness properties. This paper presents a compara tive study of thermal protection methods that might be used to improve the durability of concrete dams subjected to freeze-thaw cycles. Firs t, the thermal, structural, and physical processes that affect the dam 's resistance to freeze-thaw cycles are discussed. The thermal durabil ity of existing northern concrete dams is then reviewed. Three thermal protection schemes are presented: (i) insulation membranes applied di rectly to the concrete facings, (ii) insulation membranes with air spa ces for drainage or visual inspection, and (iii) insulation made of gr anular material. Two-dimensional thermomechanical finite element analy ses of a typical gravity dam located in Quebec are then carried out to assess the performance of thermal protection systems using different configurations of insulating materials and exposure conditions, and to develop appropriate design criteria.