冻融循环对泡沫沥青冷再生混合料宏细观结构性能的影响

Impact of Freeze-Thaw Cycles on Macro and Micro Structure and Properties of Foamed Asphalt Cold Recycled Asphalt Mixtures

为了研究冻融循环作用对泡沫沥青冷再生混合料强度特性、疲劳性能及微观结构性能的影响情况,采用劈裂强度试验、贯入剪切试验及间接拉伸疲劳试验研究了冻融循环作用下泡沫沥青冷再生混合料强度特性和疲劳性能的衰减规律,基于X-ray CT断层无损扫描技术和VG软件的三维重构功能,分析了冻融循环作用下泡沫沥青冷再生混合料空隙级配、平均空隙直径、最可几空隙直径的变化规律,进而建立了泡沫沥青冷再生混合料宏观性能与微观空隙结构特性之间的关系。结果表明,冻融循环作用对泡沫沥青冷再生混合料贯入剪切强度、劈裂强度、疲劳寿命有显著影响,随着冻融循环次数增大,泡沫沥青冷再生混合料内部〉0.1mm^3的空隙比例增大,〈0.1mm^3空隙比例减小,平均空隙直径与最可几空隙直径随冻融循环次数增加而增大。结合不同冻融循环作用下泡沫沥青冷再生混合料的空隙结构特征,将泡沫沥青冷再生混合料内部V≤0.1mm^3空隙划分为无害孔,0.10.5mm^3空隙划分为有害孔。各应力水平下的疲劳寿命随平均空隙直径和最可几空隙直径增大而降低,二者之间负线性相关性良好。冻融循环作用使得泡沫沥青冷再生混合料中的微孔数量减少、大孔数量增多,这是冻融作用导致冷再生混合料力学强度和疲劳性能降低的主要原因之一。

In order to study the effects of freeze-thaw cycles on the strength,fatigue properties and microstructure of cold-recoverable foam mixtures,the splitting strength test,penetration shear test and indirect tensile fatigue test are used to study the effects of freeze-thaw cycles based on the X-ray CT tomographic non-destructive scanning technology and the 3D reconstruction function of VG software,the variation rules of pore gradation,average pore diameter and most probable pore diameter of foamy asphalt cold recycled mixture under the action of freeze-thaw cycles are analyzed,and then the macroscopic performance of the foam fissure recycled mixture and the relationship between microscopic pore structure are established.The results show that the freeze-thaw cycle has a significant effect on the penetration shear strength,splitting strength and fatigue life of foam asphalt cold reclaimed composites.With the increase of the number of freeze-thaw cycles,the proportion of void 〉0.1 mm^3 in the internal reclaimed foam asphalt mixture increases,and the proportion of〈0.1 mm^3 void ratio decreases,the average pore diameter and the most can be a few voids diameter increases with the number of freeze-thaw cycles increases,combined with different freeze-thaw cycles foam aggregate cold recycled aggregate voids structure characteristics,the void of V〈0.1 mm^3 in cold recycled mixture of foam asphalt is divided intoinnocuous pores,0.1〈V〈0.5 mm^3,the pores are divided into fewer pores,V〉0.5 mm^3,the pores are divided into harmful pores.The fatigue life at each stress level decreases with the increase of the average pore diameter and the most probable voids diameter.The negative linear correlation between them is good.The freeze-thaw cycles reduce the number of micro pores in the cold recycled foam aggregate,the increase of the number of macro pores is one of the main reasons for the decrease of mechanical strength and fatigue performance of cold-reclaimed mixture caused by freeze-thaw.