Investigation on the effect of Zycotherm on fracture behavior of asphalt mixtures in the presence of moisture and deicers

Road pavements are one of the most important assets of any country, and tremendous amounts of budgets are allocated for their maintenance every year. Unexpected distresses in asphalt pavement cause many financial losses. Winter maintenance of roads and infrastructures and the study of the effects of anti-icers and deicers on the asphalt pavements have always been of interest to researchers, departments, and agencies in the field of roads and transportation. As a contribution to this task, the present study was conducted to evaluate the effect of Zycotherm on the fracture behavior of asphalt mixtures in the presence of moisture and deicers. In order to achieve the research objectives, PG58-22 bitumen and siliceous materials were used to prepare the asphalt mixture and also Zycotherm was used to modify the asphalt binder. Data were collected by testing on laboratory samples. The asphalt mixture samples were conditioned in the presence of distilled water and solutions of brine, calcium magnesium acetate, and potassium acetate in their normal concentration for 96 hours at 60°C. Then, the fracture toughness of the specimens at low temperatures (K1c) and the critical strain energy release rate (Jc) at intermediate temperatures were measured by performing a semi-circular bending test (SCB). The results showed that simulation of low-temperature environmental conditions in the vicinity of distilled water and all deicers reduces the fracture toughness of asphalt mixtures compared to the dry sample. Brine solution has the most negative effect among all the deicers and reduces the K1c parameter by approximately 30%. On the other hand, Zycotherm maintains the fracture toughness of the asphalt mixture at low temperatures in the vicinity of distilled water and deicers at an almost constant level and recovers about 70% of the lost fracture strength of the sample conditioned in the brine solution. The effect of Zycotherm at intermediate temperature is different and causes the softening of bitumen and the reduction of the critical fracture force and the reduction of the critical strain energy release rate. This reduction is 34% and 32% for the dry sample and the specimen in the presence of brine solution, and 23% and 12% for the samples in the presence of calcium magnesium acetate and potassium acetate, respectively, compared to the sample made of neat bitumen. Also, samples in the vicinity of distilled water and potassium acetate solution showed no significant change in their critical strain energy release rate compared to samples in dry conditions. Visual inspection also revealed that calcium magnesium acetate causes additional stress and cracking in the samples. In a general summary and based on the obtained results, Zycotherm has a positive effect on the fracture toughness of the asphalt mixture at low temperatures but reduces the Jc parameter at intermediate temperatures. All specimens have the minimum critical strain energy release rate recommended by ASTM D-8044 at intermediate temperatures. Potassium acetate has no effect on the fracture toughness of asphalt mixtures at low and medium temperatures and can be an appropriate alternative in comparison with other deicers in winter road maintenance.