蔗渣纤维表面改性及其沥青混合料路用性能

Surface modification of bagasse fibers and road performances of asphalt mixture

为了提升蔗渣纤维沥青混合料的路用性能,分别采用一步改性法(碱、硅烷、乙酸酐)和二步改性法(碱与硅烷、碱与乙酸酐)对蔗渣纤维进行表面化学处理,并依据规范测试纤维的基本技术性能。分别以红外光谱、扫描电镜及热重法研究其改性前、后结构变化和热降解特性,并以SMA-13沥青混合料为例,分析表面改性对蔗渣纤维沥青混合料路用性能的改善效果。结果表明:与未改性的蔗渣纤维相比较,改性后纤维的吸油率倍数可提高10.9%以上;碱、硅烷、乙酸酐都能降低纤维表面分子的极性,且二步法中碱与硅烷的改性方案能够最有效地去除纤维中的无定形成分,提高了纤维表面的疏水性和界面相容性;改性后纤维的热解温度升高,热解速率变小;改性后蔗渣纤维沥青混合料的动稳定度、低温弯曲破坏应变、浸水马歇尔试验残留稳定度和冻融劈裂抗拉强度比指标最大可分别提高15.0%、12.6%、7.5%和7.0%。整体而言,在5种改性方案中,碱与硅烷改性方案呈现出最优的改性效果。

In order to improve the road performance of bagasse fiber asphalt mixture,one-step modification method(alkali,silane,acetic anhydride)and two-step modification method(alkali plus silane,alkali plus acetic anhydride)were used to treat the surface of bagasse fiber,and the basic properties of the fibers were tested according to the specifications. Following that, the structural changes of bagasse fibers before andafter modification were studied by infrared spectroscopy and scanning electron microscopy. In addition, thethermal degradation properties were investigated by the thermogravimetric analyzer. And SMA-13 asphaltmixture with bagasse fiber was designed and its road performances were evaluated according to thespecifications. The results showed that the oil absorption rates of modified fibers increased by over 10.9%compared to original fiber. Alkali, silane, and acetic anhydride could reduce the polarity of fiber surfacemolecules. Furthermore, the alkali and silane in two-step modification method could remove mosteffectively amorphous components in bagasse fiber, improving the hydrophobicity of the fiber surface andthe interfacial compatibility between fiber and asphalt components. For modified bagasse fibers, thepyrolysis temperature rose up, while the pyrolysis rate slowed down. The dynamic stability, lowtemperature flexural strains, residual stability indexes in immersing Marshall tests and splitting strengthratio indexes in freeze-thaw tests for asphalt mixtures with the modified bagasse fibers could be increasedby a maximum of 15.0%, 12.6%, 7.5% and 7.0%, respectively. Overall, among the five modificationmethods, the alkali plus silane in two-step modification showed the best modification effect.