冻融循环条件下外掺剂对沥青混合料水稳定性的影响

为评价外掺剂对沥青混合料水稳定性的影响状况,采用水泥、消石灰、橡胶粉和高分子聚合物对AC-13和AC-16沥青混合料进行掺配,然后在冻融循环条件下通过劈裂强度评价其水稳定性能.首先通过高温稳定性、低温抗裂性及水稳性试验方法,确定了水泥和消石灰的最佳改性含量;其次通过沥青三大指标测试方法、弹性恢复试验及小梁弯曲试验分别获取了高分子和橡胶粉聚合物的最佳掺量;最后对含有最佳掺量外掺剂的两级配类型沥青混合料进行冻融条件下的劈裂试验.结果表明:水泥、消石灰、橡胶粉和高分子聚合物的最佳改性含量依次为3%、2%、20%和0.3%;四种外掺剂均能有效提高沥青混合料的劈裂强度,其中含橡胶粉的劈裂强度提高幅度最大,沥青混合料自身级配组成对其劈裂强度影响较大,同条件下AC-13的劈裂强度高于AC-16;随冻融循环次数的增大,沥青混合料的劈裂强度比均呈现下降趋势,且橡胶沥青的下降速率相对缓慢,抗劈裂效果最好.

Effect of external admixture on water stability of asphalt mixture under freeze-thaw cycle conditions

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.