基质沥青重复加热后老化规律的试验研究

Experimental Study on Aging Rule of Base Asphalt after Repeated Heating

沥青重复加热致使老化会影响沥青路面热再生混合料性能及施工养护质量或科研实验结果的可靠性及稳定性,因此对基质沥青重复加热老化后的指标变化规律进行分析从而在沥青路面热再生及施工养护前或科研实验前掌握沥青的老化程度很有必要且很有意义。通过对重复加热后的基质沥青进行针入度(25℃)、延度(15℃)、软化点、旋转黏度、四组分的试验,探讨沥青重复热氧化后的老化机理及规律。试验结果表明:沥青的针入度和残留针入度比随着老化深入逐渐减小,沥青逐渐变硬变稠,流动度降低;延度的衰减速度相对较快,沥青的变形能力逐渐减弱且衰减速率加快,延展性能变差,针入度和延度分别降为原样的49.4%和46.4%;软化点逐渐增大,产生相同变形所需要的温度逐渐增大,增强沥青的高温稳定性,但同时对低温抗裂性逐渐不利。沥青的旋转黏度随着重复热氧化作用较为显著的增大,较原样增长了44.3%,老化指数也随之增大。饱和分和芳香分含量逐渐减少,饱和分含量由原样的30.36%减少到27.64%,芳香分含量由原样的35.82%减少到33.43%,胶质和沥青质含量逐渐增加,热氧化过程中芳香分和饱和分不断聚合转化成胶质,并进一步转化为沥青质,最后沥青质含量由原来的7.59%增大到12.11%。以上指标的变化使沥青逐渐变硬变脆,黏弹性减弱,变形能力变差,对沥青路用性能产生不利的影响。

Asphalt aging caused by repeated heating will affect the performance of hot recycled mixture construction and maintenance quality of asphalt pavement or the reliability and stability of scientific research and experimental results.Therefore,it is necessary and meaningful to analyze the change rule of base asphalt after repeated heating and aging so as to master the aging state of asphalt before hot recycling of asphalt pavement construction and maintenance or before scientific research test.By implementing the tests of penetration(25℃),ductility(15℃),softening point,rotary viscosity and four components for the base asphalt after the repeated heating,the aging mechanism and rule of the asphalt after repeated thermal oxidation are discussed.The results show that the penetration ratio and residual penetration ratio of asphalt decrease with the deepening of aging,the asphalt gradually hardens and thickens,and the fluidity decreases.The attenuation rate of ductility is relatively fast,and the deformation ability of asphalt is gradually weakened and the attenuation rate is accelerated.The ductility performance becomes worse.The penetration and ductility are reduced to 49.4%and 46.4%of the original sample respectively.The softening point increases gradually.The temperature required to produce the same deformation gradually increases,which can enhance the high-temperature stability of the asphalt mixture.But it is gradually unfavorable to the low-temperature crack resistance.The rotary viscosity of asphalt increases significantly with the repeated thermal oxidation,which increase to 44.3%of the original sample.The aging index also increases.The saturated and aromatic fractions in asphalt gradually reduce.The content of saturation fraction decreases from 30.36%to 27.64%.The content of aromatic fraction decreases from 35.82%to 33.43%.The contents of colloid and asphaltene gradually increase.The saturated and aromatic fractions are continuously polymerized into colloid in the thermal oxidation process,and further are converted into asphaltene.Finally,the content of asphaltene increases from 7.59%to 12.11%.The change of the above indexes makes the asphalt gradually harden and brittle,the viscoelasticity weaken and the deformation ability worse,which has a negative effect on the pavement performance of asphalt.