چكيده به لاتين
One way to control freezing and reopening snow-covered roads in winter is the use of deicers. Despite the widespread use of these materials, their use weakens the mastic resistance and bitumen-aggregate adhesion, which leads to the formation and growth of moisture damage and fatigue cracks. Despite studies on the effect of deicers on the asphalt mixture properties, the mechanism of the deicers’ impacts by using thermodynamic methods, which is related to the occurrence of moisture damage and fatigue cracking, has not been considered. According to this issue, in this study, the effects of two new deicers calcium magnesium acetate (CMA) and potassium acetate (PA), along with the traditional deicer sodium chloride (NaCl) on moisture damage and fatigue cracking have been investigated by utilizing mechanical and thermodynamic methods in environmental simulation conditions, including 1, 3 and 5 freeze-thaw cycles. Therefore, indirect tensile strength tests (ITS), indirect tensile fatigue tests (ITFT), and surface free energy (SFE) were performed on 52 different compounds in dry and wet conditions. Also, to increase the resistance of asphalt mixtures, Nano hydrated lime was used as a bitumen modifier. After that, by using the obtained results, the predictive model of the tensile strength ratio (TSR) and the number of fatigue ratio (NFR) with multivariate regression (MVR), Group Method of Data Handling (GMDH) and genetic programming (GP) base on surface free energy variables and other asphalt mix properties have been provided. The results of this study show that the amount of indirect tensile strength and fatigue life of asphalt mixtures decreases with the increasing number of freeze-thaw cycles, and the effectiveness of deicers on the number of fatigue ratio (NFR) of asphalt mixtures is much higher than the tensile strength ratio (TSR). Among deicer materials, the asphalt mixtures, which are saturated in CMA, had the highest indirect tensile strength, and PA deicer resulted in the lowest fatigue life. Solutions containing deicers reduce the bitumen resistance to cracking. This causes the bitumen membrane to rupture as quickly as possible, while these materials have more negative separation energy values than water. Among the deicer materials, PA solution has the most negative separation energy, NaCl and CMA solutions have the most desirable separation energy. The use of Nano hydrated lime (NHL) as a bitumen modifier leads to an increase in the resistance of asphalt mixtures against moisture and fatigue. It has the most significant impact among the deicer materials on the adhesion of specimens under the condition of CMA. Among the various methods for providing a predictive model, the GP method has the highest determination coefficient and the lowest error. By optimizing the percentage of input values to the GP model, 1.17%, 0.87%, 1.21% and 1.34% of the Nano hydrated lime are recommended as the best optimal amount to increase the moisture resistance and fatigue life of all samples, CMA, NaCl, PA condition sample, respectively.
