The mechanical properties of polyurethane grouting materials were significantly improved when cement, sodium meta-silicate, red mud, slag, and fly ash were added. However, the grouting mechanisms of polyurethane composite materials are not clear. The grouting mechanisms of polyurethane composite materials in asphalt pavement subsidence were investigated. The results of computed tomography analysis show that polyurethane foam is filled with geopolymer hydration products. The results from ground penetrating radar after grouting show that mapping has no significant fluctuation or dislocation effect, which indicates that the grouting effect is strong. The high-density electrometer can also test the pavement subsidence place and distribution. The grouting mechanisms indicate that polyurethane foam acts as the consolidation structure, and the geopolymer filled with the foam pores of polyurethane and geopolymer forms a stable consolidated body. The seriflux includes under-layer seriflux (red mud, slag, water, and polyurethane composite materials) and upper-layer seriflux (polyurethane seriflux), and there exists a weak phase separation phenomenon, in which the separation phase is mainly polyurethane with little red mud-based geopolymer.

High-content waste-rubber-modified asphalt (HRMA) has high viscosity and poor storage stability. HRMA not only improves the properties of road asphalt, but also reduces the environmental pollution caused by waste tires. Enhancing the molecular interaction of waste rubber and asphalt is key to making full use of HRMA. In this paper, aromatic oil was used as the activator for waste rubber. The molecular interaction mechanism between aromatic oil and HRMA was investigated. The radial distribution function, diffusion coefficient, free volume, solubility parameter, and shear viscosity were calculated through molecular simulations. Storage stability, micromorphology, and adhesive force were measured via experiments. The adhesive force of HRMA−1 (4.9 nN) was lower than that of RMA (6.2 nN) and HRMA−2 (5.8 nN). The results show that aromatic oil can promote the dispersion of waste rubber, making the storage of asphalt systems stable. There exists a strong electrostatic force between rubber and asphaltenes and an intermolecular force between rubber and aromatic oil or aromatics, which makes the aromatic oil and aromatics of parcel rubber molecules and waste rubber highly soluble in asphalt. Molecular simulations confirmed the molecular interaction between rubber and aromatic oil, and aromatic oil was shown to reduce the viscosity of HRMA.

The morphology of coarse aggregate has a significant impact on the road performance of asphalt mixtures and aggregate characterization studies, but many studies were based on the two-dimensional morphology of coarse aggregate, which failed to consider morphological characteristics in a holistic manner. In order to quantitatively analyze the shape, angularity, and texture characteristics of roadway coarse aggregates, a rapid and accurate multiparameter characterization method of coarse aggregate 3D morphology is explored in this article. A 3D laser scanner is used to obtain the 3D point cloud data of pebble, granite, and basalt, and the solid models of the three coarse aggregates are reconstructed. In addition, the fitted ellipsoidal algorithm and Laplace smoothing algorithm are proposed for the characterization analysis of the overall shape, angularity, and surface roughness of coarse aggregate, and the variation rules of multicharacteristic parameters of coarse aggregate are summarized. The results of the study show that the ratio of the three axes of the fitted ellipsoid can be used to classify the shape of coarse aggregate into four types, among which the cubic shape accounts for the majority of the coarse aggregate. By analyzing the fitted ellipsoidal value and the change rate of angularity of coarse aggregate, it is concluded that the larger the values of both, the more angular the aggregate is. Moreover, the study finds that the fitted ellipsoidal value can characterize not only the shape of coarse aggregate, but also its angularity to some extent. Compared with the spherical value, the fitted ellipsoidal value has better variability and is more “sensitive” to the overall data. The change in surface area can well characterize the texture of coarse aggregate. When the particle size is small, the larger the surface area change rate of the coarse aggregates, the better the roughness of the aggregates, among which the surface area change rate of basalt is the largest. The influence of aggregate morphology was not adequately considered in previous studies of asphalt-aggregate adhesion, and this study provides parameter help for subsequent quantitative analysis of the relationship between asphalt-aggregate adhesion and coarse aggregate morphology.

Since FTIR is a sensitive micro-region measurement method, research on the impact of the heterogeneity of both aggregates and asphalt mortar is meaningful and comprehensive for accurate measurement with FTIR spectroscopy. In this paper, the impact of the heterogeneity of aggregates coated with asphalt mortar on their FTIR spectra and spectral reproducibility was creatively studied. The comparative analysis of the respective absorption peaks indicated that the characteristic absorption peaks of the aggregate coated with asphalt mortar were the superposition of the respective absorption peaks of its components. And research on the spectra of the coated aggregates obtained from the same batch of asphalt mixture fabricated at the same time showed that significantly different peak intensities could be affected by minor variations in their components due to the heterogeneity. Furthermore, statistical analysis suggested that the original spectral reproducibility of the coated aggregates was greatly affected by their heterogeneity, with a high coefficient of variation values. In conclusion, the heterogeneity of the coated aggregates could affect peak intensities and spectral reproducibility in micro-regions.