Abstract: In order to evaluate the effect of the external admixture on the water stability of the asphalt mixture, the cement, hydrated lime, rubber powder and high molecular polymer were incorporated into the AC-13 and AC-16 asphalt mixture, then the water stability performance were evaluated by the splitting strength under freeze-thaw cycles. Firstly, the optimum modification content of cement and hydrated lime was determined by high temperature stability, low temperature crack resistance and water stability test method. Secondly, the optimal blending amount of high molecular and rubber powder polymer was obtained by three major indicators of asphalt test methods, elastic recovery test and beam bending test. Finally, the two types of asphalt mixture containing the best blend of external admixtures were subjected to a splitting test under freeze-thaw conditions. The results show that the optimum modified contents of cement, hydrated lime, rubber powder and high molecular polymer are 3%, 2%, 20% and 0.3%, respectively. The four external admixtures can effectively improve the splitting strength of the asphalt mixture, among which the splitting strength with rubber powder increases the most. The gradation composition of asphalt mixture has a great influence on the splitting strength. Under the same conditions, the splitting strength of AC-13 is better than that of AC-16. With the increase of the number of freeze-thaw cycles, the splitting strength ratio of asphalt mixture shows a downward trend, and the rate of decline of rubber asphalt is relatively slow, and the anti-cracking effect is the best.

Key words: asphalt pavement, freeze-thaw cycles, external admixture, optimum dosage, splitting strength