The Effect of Additives on the Low Temperature Ice-Melting Capacity of NaCl

Abstract

Winter maintenance of high-traffic volume roads requires chemicals for the strategy of obtaining sufficient friction. Challenges often arise in very cold temperatures because the effect is reduced. To improve the low temperature ice-melting capacity of road salt, additives are sometimes used. There is a lack of knowledge as to how these additives affect low temperature ice-melting capacity. The tests often use SHPR H-205.1 and H-205.2; however, recent research has shown that the SHRP tests produce inaccurate results. This paper uses calorimetry to study the effect of additives on the low temperature ice-melting capacity of sodium chloride (NaCl). Magnesium chloride (MgCl2), calcium chloride (CaCl2), potassium formate (KFo), calcium magnesium acetate (CMA), and sugar (sucrose) were added to NaCl at −18°C. The chemicals were also tested individually. The measurements were done in a recently improved custom-made calorimeter, described in the paper. The results showed that solid chemicals had a far higher melting capacity than solutions. In a solid state NaCl had the highest ice-melting capacity, however, the results differed for solutions, where brine had the lowest. CaCl2had the highest ice-melting capacity of the solutions, melting 285% more than NaCl at −18.6°C. This was followed by MgCl2, KFo, mix NaCl/CaCl2, mix NaCl/CMA, CMA, and mix NaCl/MgCl2. The improvements using chlorides (MgCl2and CaCl2) depended on the amount of additive. KFo had a destructive influence on melting capacity when mixed with NaCl, whereas mixing CMA with NaCl produced a higher melting capacity than the two components individually. Sugar froze at −18°C.