粗集料三维棱角对沥青混合料体积指标及性能的影响

Influence of 3D Angularity of Coarse Aggregate on Volume Indicator and Performance of Asphalt Mixture

为了研究粗集料三维棱角对沥青混合料体积指标和力学性能的影响,采用高精度蓝光扫描仪获取了粗集料的三维点云图像,通过Khachiyan算法和拟合函数得到了粗集料三维点云图像的最小体积包围椭球和最佳拟合椭球。基于粗集料表面三维点云数据和最佳拟合椭球,构建了粗集料三维棱角指标。通过洛杉矶磨耗仪分别磨耗0次、300次、600次和900次的方法,制备了具有不同棱角性的粗集料,并使用此粗集料制备了沥青混合料AC-13。通过马歇尔试验、车辙试验、低温小梁弯曲试验、浸水马歇尔试验和冻融劈裂试验对比研究了粗集料三维棱角对AC-13体积指标和力学性能的影响。结果表明:(1)随着粗集料复合棱角指标的增大,沥青混合料AC-13的最佳油石比逐渐增加,二者呈现显著的线性正相关性;(2)随着粗集料复合棱角指标的增大,沥青混合料AC-13的毛体积密度和沥青饱和度都逐渐减小,空隙率和矿料间隙率都逐渐增大;(3)随着粗集料复合棱角指标的增大,沥青混合料AC-13的动稳定度逐渐增加,二者呈现显著的线性正相关性;(4)随着粗集料复合棱角指标的增大,沥青混合料AC-13的破坏应变先减小后增大,二者呈较强的二次相关性;(5)随着粗集料复合棱角的增加,沥青混合料AC-13的浸水稳定性呈下降趋势,冻融稳定性先减小后增大。

To study the influence of 3 D angularity of coarse aggregate on the volume indicators and mechanical performance of asphalt mixture, the 3 D point cloud images of coarse aggregates are obtained by high precision blue ray scanner. The minimum volume enclosing ellipsoid and the optimal fitting ellipsoid of coarse aggregates are obtained by the Khachiyan algorithm and the fitting function. The 3 D angularity indicators of coarse aggregates are constructed based on the 3 D point cloud data of coarse aggregate surface and the optimal fitting ellipsoid. The coarse aggregates with different angularities are prepared by using Los Angeles attrition machine for abrasion of 0, 300, 600 and 900 times respectively, and asphalt mixture AC-13 is prepared with these coarse aggregates. The influences of 3 D angularity of coarse aggregate on the volume indicators and mechanical performance of asphalt mixture AC-13 are comparatively investigated by Marshall test, rutting test, low-temperature beam bending test, immersion Marshall test and freeze-thaw splitting test. The result shows that(1) with the increase of composite angularity indicator of coarse aggregate, the optimum asphalt-aggregate ratio of asphalt mixture AC-13 increases gradually, showing a significant linear positive correlation;(2) with the increase of composite angularity indicator of coarse aggregate, both the bulk density and the asphalt saturation of AC-13 decrease gradually, while both the air voids and the mineral aggregate porosity increase gradually;(3) with the increase of composite angularity indicator of coarse aggregate, the dynamic stability of AC-13 increases, showing a significant linear positive correlation;(4) with the increase of composite angularity indicator of coarse aggregate, the failure strain of AC-13 first decreases and then increases, showing a strong quadratic correlation;(5) with the increase of the coarse aggregate angularity, the water immersion stability of AC-13 decreases and its freeze-thaw stability first decreases and then increases.