FREEZE-THAW DURABILITY OF CONCRETE - ICE FORMATION PROCESS IN PORES

Freeze-thaw durability of concrete is of great importance to hydraulic structures in cold areas. Study of ice formation process in concrete pores is necessary to evaluate the damages in concrete caused by freez ing. In this paper, freezing of pore solution in concrete exposed to a freeze-thaw cycle is studied by following the change of concrete elec trical conductivity with freezing temperatures. Concretes were subject ed to freeze-thaw cycles with temperature varying between -0 degrees C and -20 degrees C. In the freezing process, the changing rate of conc rete electrical conductivity obviously decreases at about -10 degrees C, indicating that more pore solution in concrete freezes above -10 de grees C than below -10 degrees C. According to Powers' static hydrauli c pressure hypothesis, it is thought that frost damage mainly occurs b etween 0 degrees C and -100 degrees C. To ordinary concrete, frost dam ages below -10 degrees C are negligible. (C) 1998 Elsevier Science Ltd .