基于图像处理的沥青表面自由能测试

Test of surface free energy of asphalt with image processing

为了合理地评价沥青粘附性,基于表面物理化学理论,分析了由液固界面接触角确定表面自由能的测试原理,提出了基于数字图像处理的沥青表面自由能测试方法,并确定了图像处理的有效算法.由此提取的液滴边界清晰、定位准确.同时,提出了采用椭圆曲线对液滴边界进行拟合的方法.试验结果表明,椭圆曲线与液滴边界像素点非常吻合,很好地表征了液滴边界的几何形状;据此,由椭圆曲线在接触点处的斜率即可求出接触角.然后,选取了6种沥青和3种已知液体,进行了接触角的大量实际测试.研究结果表明,测得的数据变异性小,精度高,接触角与表面自由能之间具有很好的线性相关性,由此得到的沥青表面自由能可以准确地反映沥青与集料之间的粘附性.因此,采用数字图像处理技术测试沥青表面自由能是一种快速、准确、可靠且方便的评价沥青粘附性的方法,可应用于工程实践.

In order to evaluate the asphalt adhesion in a reasonable way,the test principle of surface free energy determined by the contact angle of interface between liquid and solid was analyzed in accordance with the theory of surface physical chemistry.The test method of surface free energy of asphalt based on the digital image processing was put forward,and the efficient algorithms were determined to detect the droplet edge clearly and accurately.Meanwhile,the method was put forward to fit the droplet edge with an elliptic curve.The experiments show that the elliptic curve is extremely fitted with the droplet edge pixels to represent the geometry of droplet edge well.Hereby,the contact angles can be calculated from the gradients of contact points on the elliptic curve.Then six kinds of asphalt and three kinds of known liquid were selected to make many practical tests of contact angles.The results show that the tested data are small in variability and high in accuracy.There are very good linear correlations between the contact angles and the surface free energy.The obtained surface free energy can accurately reflect the adhesion between asphalt and aggregate.Therefore,the test of surface free energy of asphalt with the technology of digital image processing is a rapid,accurate,reliable and convenient method to evaluate the asphalt adhesion,and the method can be applied in the engineering practice.