In winter, de-icing salt is spread on the roads using gritting vehicles to fight icy conditions. To this end, the salt must be pourable. After longer periods of storage, the pourability of salt decreases more or less significantly, depending on its origin and type of storage. No methods for determination of the pourability of de-icing agents have been specified to date, neither in the Technical Delivery Terms for Grits for the Winter Road Clearing and Gritting Service (TL-Streu), nor in the currently elaborated standard DIN EN 16811-1. During the course of the studies, several methods for determination of the pourability specified in the literature were compared to each other; the flow method acc. to Alfred SONNTAG was chosen for daily routine application. This method was used to examine 46 de-icing salt samples from different storage facilities and different manufacturers, and the results were compared to further physical parameters, such as grain size distribution, moisture content, bulk density, tapped density, specific surface area, pH value and content of anticaking agents. It was revealed, however, that there are still further influencing factors, in particular those relating to the caking of the salts. The flow method can no longer be applied for already solidified salt. To this end, the uniaxial compression test can be used. These two methods were used to examine salt that had been stored in a climate-controlled chamber for four weeks with simulation of the seasonal weather of a typical year. For further development of a method for early identification of the tendency of salts to caking, it is suggested to clarify issues regarding determination of the content of the anticaking agent ferrocyanide, to examine the influence of the surface quality on the pourability and to further develop the suggested needle insertion method for determination of the solidification of bulk salt. (Author/publisher)
Abstract