沥青含量对混合料疲劳极限特性的影响

Effect of asphalt content on fatigue limit for asphalt mixture

利用马歇尔试验确定了沥青混合料的最佳沥青含量,采用控制应变的小梁疲劳试验,研究了最佳沥青含量和富沥青含量混合料弯拉劲度模量随应变水平的变化规律,得到了应变水平与荷载作用次数模型,并分析了2种混合料在不同应变水平和轴次下的疲劳特性。分析结果表明:不同应变水平下,2种混合料弯拉劲度模量随荷载作用次数变化规律基本一致,高应变水平下弯拉劲度模量迅速衰减,低应变水平下初始阶段模量明显降低,随后趋于平缓;以弯拉劲度模量降为初始值的一半作为破坏标准,2种混合料疲劳寿命和应变的关系都呈非线性特征,且低应变水平下曲线呈现典型的渐近线趋势,表明2种沥青混合料具有类似的疲劳极限特性;富沥青含量混合料在高应变水平下对疲劳极限特性影响有限,只有当应变水平小于100με时才对疲劳寿命有明显改善;在进行永久性沥青路面沥青层设计时,不能简单通过增加沥青含量减薄沥青层厚度。

The optimum asphalt contents of asphalt mixtures were determined by using Marshell test. The fatigue performance change rules of asphalt concretes with different asphalt contents with strain levels were studied by controlled-strain beam fatigue test. The relationship model between strain level and load cycles was built. The fatigue characters of optimal asphalt content mixture and rich asphalt content mixture under different strain levels and load cycles were analyzed. The result shows that for different strain levels, the asphalt mixture flexural stiffness moduli of the two mixtures have the same rule, which reduce quickly with a sharp increase of load cycles during high strain level and tend to reduce slowly with lower strain level. The relationships of fatigue life and strain for the two mixtures are nonlinear, and low-strain curves show a typical feature of asymptote. So the two different asphalt mixtures all have the similar characteristics of fatigue limit. Rich asphalt content has little effect on the fatigue limit at high strain, and it can markedly improve the fatigue life only when strain level is lower than 100με . Thus simply increasing asphalt content can not mean to thin the thickness of asphalt course during designing perpetual asphalt pavement. 7 tabs, 2 figs, 15 refs.