In order to reduce the discharge of chlorides in connection with winter road management, calcium chloride has been suggested as an alternative to sodium chloride (NaCl). It is hoped that a smaller quantity of calcium chloride (CaCl2) will be needed for the same de-icing to be achieved as by using NaCl. In Sweden, calcium chloride has previously had some limited use, mainly for prewetting NaCl, but it is not used at all at present for de-icing. The main reason for this is the negative effect on concrete which some investigations have shown. As part of the evaluation of CaCl2, above all in the form of solution, a study of the literature has been carried out by commission of the Swedish Road Administration. The areas investigated are snow and ice melting properties, corrosion, effect on concrete, environmental impact and economy. Investigations show that CaCl2 produces a more rapid effect and is effective at lower temperatures than NaCl. The cause of the faster effect is that CaCl2 absorbs moisture and thus goes into solution more rapidly, and that heat is evolved during the process of solution. This advantage is however lost when a solution is used. As regards its effect on the frost resistance of concrete, no major difference has been found compared with NaCl. Over the past few years, concrete quality has appreciably improved, and the frost resistance of modern concrete in the presence of salt is very good. In contrast to NaCl, however, there are some investigations which suggest that CaCl2 also has a chemical effect on concrete. However, there is no indication in the literature as to how serious this problem is. Factors which play a part are temperature, concentration and presumably grade of concrete also. (A)
Samenvatting