Full-depth reclamation with Portland cement (FDR-PC) represents an innovative cold recycling technology for pavements, holding significant promise due to its capacity to reuse deteriorated pavement base layers. This paper investigates the key factors influencing the strength properties of FDR-PC. The results indicate that, compared to the static compaction method, the vibratory compaction method yields cold-recycled mixtures with higher maximum dry density and unconfined compressive strength (UCS). Increasing the cement content and base-to-surface ratio, extending the curing time, and raising the curing temperature all contribute to enhancing UCS. Furthermore, increasing the base-to-surface ratio and cement content enhances both indirect tensile strength and flexural strength. An approximate linear correlation exists between indirect tensile strength and UCS, as well as between flexural strength and UCS. The strength characteristics of FDR-PC were comprehensively characterized in this study, providing effective verification of its applicability.

Improving the high-temperature stability and water damage resistance of asphalt pavements has always been a priority. This study proposed a composite high modulus modifier with rock asphalt and nanopolymer as main materials (HRMA) to prepare the high modulus asphalt mixture for their excellent rutting resistance. Moreover, its modification effect and modification mechanism were studied. The effect of HRMA content on the rheological performance of asphalt was investigated using Brookfield rotational viscosity, dynamic shear rheometers (DSR), and bending beam rheometers (BBR). Their modification mechanisms were revealed by Fourier Transformation Infrared Spectroscopy (FTIR). Besides, the properties of the mixtures were studied in various laboratory tests and compared with the 90# asphalt mixture and SBS asphalt mixture. Some of these included the rutting test, the bending test, the Marshall immersion test, and the freeze-thaw indirect tension test. The results indicated that with the increase of HRMA content, the deformation resistance of the asphalt mixture under high-temperature conditions was significantly improved, and the temperature sensitivity was changed. However, the crack resistance of its asphalt mixtures under low temperature was reduced due to the lower ductility of HRMA-modified asphalt. The recommended HRMA content was 21.8% of the asphalt, combining performance and construction cost.

Direct coal liquefaction residue (DCLR), a byproduct of the coal-to-oil process, poses a significant challenge for resource recycling and high-value utilization. Research has found that DCLR performs well in high temperature performance, but its shortcomings in low temperature performance remain a key issue limiting its widespread application. This research employs a composite modification approach, using DCLR as the primary material and incorporating SBS, rubber powder, aromatics oil, plasticizers, and stabilizers to prepare DCLR high-viscosity modified bitumen. The optimal formula was determined as 6% Styrene-Butadiene Styrene block copolymer (SBS) + 5% DCLR + 3% Dibutyl phthalate (DBP) + 10% rubber powder + 4% aromatics oil + 0.15% stabilizer. Performance tests showed that the rutting factor of the DCLR high-viscosity asphalt was 59.8% higher than that of the LT high-viscosity asphalt, and the G*/sinδ value after Rolling Thin Film Oven Test (RTFOT) aging had the smallest increase, confirming its excellent high-temperature rut resistance and resistance to short-term aging. The zero-shear viscosity (ZSV) values obtained by fitting the Carreau model indicated that within the temperature range of 46°C–64°C, the ZSV values of the DCLR modified asphalt were 1-2 orders of magnitude higher than those of the control samples, and the asphalt still maintained stable viscoelasticity at high temperatures (64°C), demonstrating its outstanding interfacial bonding performance. The bending beam rheometer (BBR) test results showed that the creep stiffness modulus of the three asphalts decreased while the creep rate increased, and the creep stiffness and creep rate had an approximate exponential relationship with temperature. Under the same temperature conditions, the stiffness modulus and creep rate of the DCLR high-viscosity asphalt were not significantly different from those of the Lutai (LT) high-viscosity asphalt, indicating its relatively good low-temperature crack resistance. Fluorescence microscopy results revealed that the DCLR system formed a stable three dimensional colloidal skeleton structure between the modifier molecules and the asphaltenes, which is the fundamental reason for its superior performance and low-temperature properties compared to the LT high-viscosity asphalt.

The full-depth reclamation with Portland cement (FDR-PC) technology embodies an environmentally friendly approach to solving the damage to old asphalt pavement. Fatigue failure emerges as the predominant mode of degradation for FDR-PC pavement. The fatigue characteristics of the full-depth reclamation with Portland cement cold recycled mixtures were evaluated through four-point bending tests. Three contents (4%, 5%, 6%) of cement and three base-to-surface ratios (10:0, 8:2, 6:4) were utilized. The fatigue equations were derived for the mixtures using a two-parameter Weibull distribution. The results indicate that all correlation coefficients of the Weibull distribution model surpass 0.88, effectively projecting the lifespan of FDR-PC. With increases in cement contents and base-to-surface ratios, the fatigue life of the mixture extends, though with an augmentation of stress sensitivity. Comparative analysis with the fatigue equation model parameters of the current Chinese specifications for the design of highway asphalt pavement reveals that mixtures with a 4% cement content and combinations of a 5% cement content with a low base-to-surface ratio meet the requirements for inorganic-binder-stabilized soil. Additionally, mixtures with a 5% cement content and a high base-to-surface ratio, along with those with a 6% cement content, fulfill the specifications for inorganic-binder-stabilized granular materials.

Geosynthetic interlayer systems are effective techniques to control reflective cracking and have better waterproof performance in damaged asphalt pavements. The interlayer bonding performance is critical to its function. This research investigated the interfacial adhesive property and road performance of asphalt overlay with geotextile interlayer. First, shear damage energy characteristics of geotextile interlayer have been investigated by varying tack coat types (SBS-modified asphalt, virgin asphalt, and emulsified asphalt), application rates (0.3kg/m²1.2kg/m²), spraying times (12), upper mixture paving temperature (140°C180°C), service temperature (5°C45°C), and soaking time (0h96h). In addition, bending fatigue tests, rutting tests, and semicircular bending tests were carried out to evaluate the comprehensive road performance of the asphalt overlay. The results showed that the interface adhesive property of asphalt overlay with geotextile interlayer using SBS-modified asphalt is best when the application rate is 0.8kg/m². The higher paving temperature is beneficial for the geotextile interlayer adhesion performance when the SBS-modified asphalt is sprayed at one time, while the paving temperature has almost no effect when the SBS-modified asphalt is sprayed at two times. The geotextile interlayer adhesion performance is less affected by temperature and more affected by water immersion. Compared with the common asphalt overlay types, the asphalt overlay with geotextile interlayer using SBS-modified asphalt shows better overall performance.

In order to solve the problem of high-value utilization of coal-to-oil residual direct coal liquefaction residual asphalt, it is compounded with SBS and aromatic oil to modify the matrix asphalt, and 9 compounding schemes are designed using orthogonal experimental methods. Dynamic frequency sweep tests using DSR and a simplified Carreau equation model fitted to the complex viscosity to obtain its zero shear viscosity; the creep recovery rate, irrecoverable creep flexibility and irrecoverable creep flexibility difference of each modified asphalt were determined by MSCR at different temperatures and stress levels, and the high temperature rheological properties of 9 composite modified asphalts were evaluated by grey correlation analysis of zero shear viscosity and high temperature rheological parameters. Bending beam rheological experiments were carried out on the aged composite modified asphalt to analyse its low temperature rheological properties based on the viscoelastic parameters and linear fitting of the Burgers model. The results show that: The high temperature deformation resistance of DCLR composite modified asphalt are better than the matrix asphalt, the most influential modifier is SBS, and the higher the dose, the stronger the high temperature deformation resistance. The unrecoverable creep flexibility J_nr3.2 at 70 °C can better respond to the high temperature performance of asphalt, the ratio of 9% DCLR + 4% SBS + 2% aromatic oil DCLR composite modified asphalt with the best high temperature performance. Burgers model can better reflect the creep process of asphalt, DCLR composite modified asphalt has some defects in low temperature performance, the higher the dose of DCLR, the poorer the low temperature performance of the composite modified asphalt. The low temperature sensitivity of DCLR composite modified asphalt has been reduced, low temperature crack resistance has been slightly enhanced.