Microscopic Study of Ice Propagation in Concrete

This paper introduces a new procedure to examine ice formation and propagation in concrete. The technique, using the concept of directional solidification, allows the controlled cooling and warming of relatively large specimens and also permits continuous monitoring of the solid/liquid interface. An experimental program was initiated to study ice formation in the following materials: ionic solutions, normal and lightweight aggregate, cement paste, and concrete. The study reveals that, generally, ice does not completely fill up the pores in cement paste and supercooled water always exists due to the alkalinity of cement paste. The velocity of ice propagation differs in various components of concrete, and ice propagation in aggregate particles is faster than that in the matrix. Sequential images of ice formation in air-entrained voids give insight into the freezing mechanism of concrete.