Crack length measurement is an important part of asphalt pavement detection. However, some crack measurement techniques cannot satisfy the needs of accuracy and efficiency. This study discusses application of deep convolutional neural networks (DCNN) in automatic recognition of pavement crack length in batches. Original red, green and blue images were transformed to grey-scale images to calculate their threshold and pre-extract cracks’ properties by k-means clustering analysis. Then the pre-extracted crack images were used as both training and testing samples. The process of accomplishing DCNN to recognise the crack length included the structure designing, training, and testing of the networks. The output results of well-trained DCNN were compared with those of the actual measurement to verify the accuracy of the networks. The result indicates that the training strategy including two processes overcomes the lack of crack labelled images and improves the accuracy of the network, combining with quadrature encoding and stochastic gradient descent. Recognition accuracy of DCNN is 94.36%, maximum length error is 1 cm and mean squared error is 0.2377. The error rates of length ranges 6–7 cm and 7–8 cm are bigger than other ranges Therefore, the networks can be adopted to measure the crack length accurately, but more 6–8 cm crack images should be used to improve the accuracy of the networks in future.

As a long-life road surfacing material, epoxy asphalt has many benefits such as high strength, excellent bonding properties, high temperature stability, and high resistance to low temperature cracking. With the increasing use of epoxy asphalt in orthotropic steel bridge deck pavements, there has been an urgent need for a fast, easy, and reliable maintenance method. Microwave heating provides a promising method for epoxy asphalt curing. This study explored the possibility of using microwave heating for epoxy asphalt curing and investigated the effects of microwave heating on chemical and physical properties of epoxy asphalt. An epoxy asphalt suitable for microwave heating was prepared, tested for its tensile properties, and characterized using thermal analysis, infrared analysis, and microscopy tests. The results showed that the epoxy asphalt cured by microwave heating had a better ductility than that cured by conventional heating. The fluorescence and scanning electronic microscopy (SEM) observati...

Microwave heating technology has been adopted in asphalt pavement maintenance to reduce the total cost resulting from the energy consumption. In this paper, laboratory preparation and microwave heating tests of carbonyl iron powders (CIPs)/asphalt binder were carried out. The modeling procedure, microwave heating efficiency and the properties of the CIPs/asphalt binder - such as penetration, softening point and ductility - were studied. The results show that microwave heating efficiency of CIPs/asphalt binder is enormously higher than that of ordinary asphalt binder. Adding a certain amount of CIPs can improve the asphalt binder's resistance to deformation at high temperature. All of these can put forward a theoretical basis to design asphalt mixtures suitable for use in snow and ice removal by microwave pavement maintenance vehicles.

An experimental investigation was carried out to study the influence of graft treatment for Kevlar stitch threads on the interlaminar properties of stitched unidirectional laminates. The surfaces of Kevlar stitch threads were immersed in a solution of Dimethyl sulfoxide mixed with NaH for some time, and then alkoxysilane was grafted onto the surface of modified Kevlar threads. The corresponding physical and chemical changes in the surface of Kevlar threads were carefully evaluated using XPS, SEM, water absorption, and tensile measurement. Results show that the treated Kevlar threads have much rougher surface morphologies, its tensile strength is slightly improved, and their wettability are greatly improved. The stitched carbon /epoxy composite using surface-treated Kevlar threads has excellent hydrothermal property. The resins can better wet the surface treatment of Kevlar stitch threads, and the sizes of rich resin can be reduced. The moisture uptake of stitched composites decreases by 53.3% and its residue ratio of interlaminar shear strength in a wet state improves by 13.1%.