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该研究开发了一种简易的可用来评价不同沥青流变特性的试验方法。该方法将标准针入度试验的针头改为球状压头并以此来测定沥青的基本特性,并采用Lee和Radok推荐的刚性压头在半无限粘弹性介质中的边界值问题的求解方法来预估沥青的蠕变柔量。试验中采用了两种基质沥青以及两种改性剂。采用有限元的方法来研究沥青试模尺寸对不同沥青蠕变柔量的影响。在测定沥青蠕变柔量时采用的假设是粘弹性半无限介质,然而实际的试验是在有限尺寸的试样上进行的,该文采用两种方法来计算试样尺寸效应:1)采用3种不同尺寸试样来进行试验,再通过数学外推法预估沥青实际的蠕变柔量;2)运用有限元建模的方法模拟不同尺寸沥青试样在改进针入度试验中的粘弹性力学响应,并以此来修正尺寸效应。采用上述两种方法对改进针入度试验中测得的沥青蠕变柔量进行尺寸效应修正,将其与动态剪切流变仪DSR上测得的沥青蠕变柔量进行对比。结果表明:经过尺寸效应修正后的沥青蠕变柔量与DSR所测结果具有很好的相关性。此外,通过改进针入度试验还可获取沥青在20℃及30℃时的流变主曲线。改进针入度试验的局限性在于不能在高于40℃温度下进行试验。
The study developed a simple test method that can be used to evaluate the rheological properties of different bitumen. In this method, the needle of the standard penetration test is changed into a spherical indenter to measure the basic properties of the asphalt. The method of solving the boundary value problem of semi-infinite viscoelastic media by Lee and Radok is proposed Predict asphalt creep compliance. Two kinds of matrix asphalt and two modifiers were used in the experiment. Finite element method was used to study the influence of test specimen size on creep compliance of different asphalt. The assumptions used in the determination of creep compliance of bitumen are viscoelastic semi-infinite media. However, the actual experiment is carried out on a sample of finite size. Two methods are used to calculate the sample size effect: 1) Different sizes of specimens to test, and then through mathematical extrapolation to predict the actual creep compliance of asphalt; 2) the use of finite element modeling method to simulate the different sizes of asphalt samples in the penetration test to improve the viscoelasticity Mechanical response, and thus to amend the size effect. The above two methods were used to modify the creep compliance of asphalt measured in the improved penetration test, and compared with the creep compliance of asphalt measured by dynamic shear rheometer DSR. The results show that there is a good correlation between the creep compliance and the DSR after the size effect is corrected. In addition, the main rheological curves of asphalt at 20 ℃ and 30 ℃ can also be obtained by improving the penetration test. The limitation of improved penetration tests is that they can not be tested at temperatures above 40 ° C.