机场道面高频振捣密实混凝土弯曲疲劳性能演化特征

为了验证高频振捣滑模摊铺工艺的可靠性及其对含大粒径骨料(最大粒径为40 mm)干硬性混凝土疲劳演化特征的影响, 分别采用小型机具施工工艺(低频振捣)和滑模施工工艺(高频振捣)在郑州新郑机场摊铺40 cm厚混凝土道面板; 对现场切割试件与室内相同配比成型的试件(尺寸均为150 mm×150 mm×550 mm)进行了弯拉强度与疲劳试验, 测量了跨中梁底应变和竖向位移; 根据可靠度理论分析了不同工艺成型混凝土小梁的弯曲疲劳寿命概率分布特征, 建立了弯曲疲劳方程, 进一步分析了试件的弹性模量衰减特征和梁底残余拉伸应变演变规律。研究结果表明: 高频振捣工艺能使混凝土更加致密, 试件平均疲劳寿命较低频振动成型试件长约27%;双对数疲劳方程能够很好地表征含大粒径骨料道面混凝土的疲劳行为; 高应力水平下高频振捣成型混凝土疲劳寿命比室内成型混凝土长4%, 低应力水平下高频振捣成型混凝土疲劳寿命比室内成型混凝土长18%以上; 混凝土抗弯拉弹性模量随加载循环比的增加基本呈线性衰减特征, 试件临近破坏时的抗弯拉弹性模量为初始模量的50%~80%;在重复荷载作用下, 梁底轴向残余应变随加载次数的增加而增大; 提出的4种典型演化形态可表征不同应力水平下混凝土残余应变的复杂增长趋势; 骨料粒径增大是导致试件疲劳性能演变规律离散性的主要原因, 疲劳荷载作用下的累积损伤和骨料依次失效过程是混凝土残余应变演化曲线出现明显台阶特征的主要原因。研究结果为进一步通过足尺环道加速加载试验建立室内试验与现场足尺道面板性能关联方程奠定了基础。 

Evolution characteristics of flexural fatigue performance of dense concrete consolidated with high frequency vibration applied in airport pavement

To verify the reliability of slip-form paving technology with high frequency vibration and its influence on the evolution characteristic of flexural fatigue of dry concrete containing large diameter aggregates(maximum to 40 mm), two 40 cm-thick concrete pavement slabs were constructed adopting the small machine construction process(low frequency vibration) and slip-form construction technology(high frequency vibration), respectively, at Xinzheng Airport, Zhengzhou. The flexural tensile strength and fatigue tests were conducted on the specimens(both dimensions are 150 mm×150 mm×550 mm) cut on the field and prepared in the laboratory with the same mixture proportion. The strains and vertical deflections at the mid span bottom of beam were measured. The flexural fatigue life probability distribution characteristics of concrete beams consolidated with different methods were analyzed according to the reliability theory, and the flexural fatigue equations were established. The deteriorations of flexural moduli of specimens and the evolutions of residual strains at the mid span bottom of beam were analyzed as well. Research result shows that the high frequency vibration technology consolidates the concrete denser, and the average fatigue life of specimens is about 27% longer than that consolidated with low frequency vibration. The double logarithmic fatigue equation can well characterize the fatigue behavior of pavement concrete containing large-diameter aggregates. The fatigue life of concrete consolidated with high frequency vibration is 4% longer than that consolidated with low frequency vibration at high stress level, while the fatigue life of concrete consolidated with high frequency vibration is 18% longer than that consolidated with low frequency vibration at low stress level. The flexural tensile modulus of concrete deteriorates linearly with the increase of loading cycle ratio. The flexural tensile moduli of specimens at the failure point are 50%-80% of the initial moduli. The axial residual strain at the bottom of beam increases with the accumulation of loading cycles. The four proposed typical evolutionary morphologies can characterize the complex growth trends of concrete residual strains at different stress levels. The increase of aggregate size mainly leads to the dispersion of the evolution rule of specimen's fatigue performance. The cumulative damage and gradually failure of aggregates under the fatigue load are responsible for the typical step characteristics in the concrete residual strain evolution curves. The research results provide a foundation for the establishment of relation function between the laboratory test and the full scale concrete pavement slab on the field, through the full scale ring track acceleration loading test.