直投式高黏改性沥青混合料路用性能试验

Experimental on Pavement Performance of High Viscosity Asphalt Mixture Modified Using Direct Casting

高黏改性沥青是决定排水沥青路面使用性能的关键因素之一。为了评价改性剂类型、掺量及生产工艺的影响,分别采用车辙、半圆弯曲、浸水马歇尔、冻融劈裂和浸水肯塔堡飞散试验对高黏改性沥青混合料的高温稳定性、低温抗裂性和水稳定性进行测试,通过微观形貌特征对改性剂在沥青中的工作机理进行分析。研究结果表明:不同因素对沥青混合料空隙率的影响很小。在相同的掺量和生产工艺下,与常规的泰孚派克(Tafpack super,TPS)高黏改性沥青混合料相比,热塑性树脂(thermoplastic resin,TPR)高黏改性沥青混合料具有更优的低温抗裂性、相当的水稳定性和略差的高温稳定性,但是两者的路用性能在统计学意义上无显著差异。TPR改性剂掺量的提高可以明显提升混合料的各项路用性能;当以70#普通沥青和苯乙烯-丁二烯-苯乙烯(styrenic block copolymers,SBS)改性沥青作为基质沥青时,TPR改性剂掺量分别达到13%和9%,其混合料路用性能即可满足排水沥青混合料的技术要求。总体上看,改性剂掺量和生产工艺对各项路用性能均有显著影响,其中改性剂掺量的影响大于生产工艺。从微观形貌角度证实采用直投法时沥青中存在颗粒结团,部分改性剂颗粒与沥青的不完全混融导致直投法的改性效率低于剪切法,因此采用直投法时应适当增加改性剂掺量。研究结果可为排水沥青路面的材料设计提供有益的参考。

The high viscosity modified asphalt binder is one of the critical factors to determine the performance of the porous asphalt pavement.The wheel tracking test,semi-circular bending test,immersion Marshall test,freeze-thaw splitting test,and immersion Cantabro test were conducted to evaluate the effects of modifier types,dosage and production process on the high-temperature stability,low-temperature cracking resistance,and moisture stability of the high viscosity modified asphalt mixtures.The working mechanism of modifier in the asphalt binder was analyzed by the characteristics of micro morphology.The study results show that different factors have little effects on the air void of the asphalt mixture.Under the same dosage and production process,the asphalt mixture modified by the TPR(thermoplastics resin)shows the better low-temperature cracking resistance,similar moisture resistance,and slightly worse high-temperature rutting resistance compared to the one modified by the conventional TPS(tafpack super).However,there is no statistically significant difference in pavement performance between them.The increase in the TPR modifier dosage improves all pavement performance of mixtures significantly.When the TPR modifier dosage reaches 13%and 9%corresponding to 70#asphalt binder and SBS modified asphalt binder used as the base binder,the pavement performance can satisfy the requirements of porous asphalt mixtures.Generally,both modifier dosage and production process have significant effects on all pavement performance.The effect of the former is greater than the latter.From the perspective of micro morphology,it is confirmed that there is particle agglomeration in the asphalt binder for the direct casting method.The incomplete mixing of some modifier particles and binder causes the lower modification efficiency of the direct casting method than that of the shear method.Therefore,the modifier dosage should be appropriately increased when the direct casting method was used.The study findings can provide a beneficial reference for the material design of the porous asphalt pavement.