chapter  4
16 Pages

Scaling, absorption and dilation of cement mortars exposed to freezing and thawing in NaCI solution

Abstract Frost damage of concrete i s normally much more severe when freezing takes place in the presence of dilute salt solutions . In this case, damage is almos t alway s o f type surface spallin g or scaling, while the interior of the concrete remains unharmed. Thi s effect o f salts has been known for a very long time, for example in connection with the use of deicing salts or exposure to sea water . I t is also known that more concentrated salt solutions cause less frost damage than do weak solutions. Th e mechanism behind this phenomenon i s not very wel l understood . Thi s study was , therefore , starte d in order t o giv e some experimental inpu t to th e formulatio n o f a destruction theory . Three type s o f test wer e performed wit h NaCl-solution s of four differen t strength s (0%, 2.5% , 5%, 10%) ; (i) a salt scaling test in which scaling, as wel l a s water uptake, was monitored; (ii) an absorption test at constant room temperature; (iii ) a dilation tes t during one-cycle freezing. Nine different cement mortars were tested; 3 water/cement ratios (0.4 , 0.6, 0.7) and three ai r contents (natura l air, and two different contents of entrained air). Th e main results are presented togethe r with some comments. Keywords: Frost resistance, sal t scaling, water absorption.