煤矸石粉/聚酯纤维沥青混合料低温抗裂性研究

Study on Low Temperature Crack Resistance of Coal Gangue Powder/Polyester Fiber Asphalt Mixture

为了研究煤矸石粉、聚酯纤维和反射裂缝对沥青混合料低温抗裂性能的影响,通过三点弯曲加载试验,选用五种煤矸石粉替代率(0%(质量分数,下同)、25%、50%、75%、100%)和六种聚酯纤维掺量(0%、0.3%、0.35%、0.4%、0.45%、0.5%),对试件底部中心无预切口和预切口偏移中心0 mm、10 mm、20 mm(模拟反射裂缝)的沥青混合料半圆形试件的低温抗裂性能进行研究;采用扫描电镜对煤矸石粉、聚酯纤维对沥青混合料低温抗裂性能的改善机理进行微观分析。通过试验得出:对于无预切口的SCB试件,聚酯纤维的最佳掺量为0.4%,煤矸石粉的最佳替代率为50%;对于有预切口的SCB试件,聚酯纤维的最佳掺量取值范围为0.38%~0.42%;随着预切口偏移距离的增大,沥青混合料所能承受的极限荷载逐渐减小,试件更容易破坏。微观机理分析得出:煤矸石粉的掺入,使填料级配得到了进一步细化,更有利于提高沥青混合料的抗裂性能;同时,聚酯纤维在沥青混合料内部能够充分形成均匀相互搭接的网格结构,沥青混合料的低温抗裂性能也最好。因此,掺加煤矸石粉和聚酯纤维能够减小反射裂缝对沥青混合料低温抗裂性能的危害。

In order to study the effect of coal gangue powder,polyester fiber and reflective crack on the low temperature crack resistance of asphalt mixture,the low temperature crack resistance of asphalt mixture was studied by three-point bending loading test.In the test,asphalt mixture specimens were processed into semi-circular disc with no pre-cut and pre-notch(simulated reflection cracks)offset center 0 mm,10 mm,20 mm on the bottom.Five replacement rates of coal gangue powder were selected as 0%,25%,50%,75%,100%,and six kinds of polyester fiber content were chosen as 0%,0.3%,0.35%,0.4%,0.45%,0.5%.The improvement mechanism of coal gangue powder and polyester fiber on low tempe-rature crack resistance of asphalt mixture was analyzed by SEM.Through experiments,the optimum amount of polyester fiber is 0.4%for SCB specimens with no pre-cut,and the optimum replacement rate of coal gangue powder is 50%;for SCB specimens with pre-cut,the optimum do-sage of polyester fibers ranges from 0.38%to 0.42%.With the increase of the offset distance of the pre-cut,the ultimate load of the asphalt mixture gradually decreases,and the semi-circular disc is more likely to be destroyed.The microscopic mechanism analysis shows that the incorporation of coal gangue powder makes the filler grading further refined,which is more conducive to improving the crack resistance of the asphalt mixture.At the same time,the polyester fiber can fully form a grid that evenly overlaps each other in the asphalt mixture and asphalt mixture has the best low temperature crack resistance.Therefore,the addition of coal gangue powder and polyester fiber can reduce the damage of reflective cracks to the low temperature crack resistance of asphalt mixture.