Old cement pavement directly overlaid with an asphalt layer produces many reflection cracks. Using microcrack homogenization technology to treat old cement pavement can effectively reduce the occurrence of reflection cracks. Micro-crack homogenization is relatively mature at the technical level; however, there is relatively little research on its mechanism. To evaluate the microcrack effect of old cement pavement, we conducted core sampling on a project road section after the appearance of microcracks. The core samples were sliced by X-ray tomography (X-ray CT). The mesostructure of the core samples was obtained. The core sample was further divided into microscopic cracks and macroscopic cracks according to the length and width of the crack. The development characteristics of cracks were subdivided into type I-III microcracks and type I-IV cracks. The core-drilling sample was divided into 5652 CT images. The statistical results showed that there were 3582 type-I microcracks, 3197 type-II microcracks, and 1835 type-III microcracks. Among the specimens, the minor proportion of microcracks was 32.87%, the most significant proportion was 100.00%, and the average ratio was 47.51%. Furthermore, the cracks development law and formation mechanism were analyzed based on CT images and cracking statistics. The results showed: (1) The microcrack homogenization process produced many microcracks in the test section and achieved a specific microcrack effect. (2) The cracks produced by the microcrack homogenization process tended to develop along the transition zone of the aggregate–cement mortar interface. The development of microcracks was mainly related to the aggregates’ shape and gradation, as well as the energy required to generate cracks. The research conclusions of this paper can be used as a theoretical basis for the optimization and improvement of the microcrack homogenization process.

Rural road construction in the loess region of Gansu Province is constrained by aggregate shortage, high material transportation costs, and the limited early performance of cement-stabilized soil. In this study, KDJ-II stabilizer and cement were used to prepare KDJ-II–cement composite-stabilized soil for potential use as a base-course material. Compared with cement-stabilized soil, the addition of 0.02% KDJ-II increased the 7-day unconfined compressive strength, splitting tensile strength, and resilient modulus by 16.7%, 17.6%, and 12.1%, respectively. Leaching-based ion concentration analysis, XRD, FTIR, and SEM were used to interpret the early strength development mechanism. The results suggest that KDJ-II influenced the leachable ion release and retention behavior of the cement-stabilized soil and helped form a sulfate-rich, alkaline, and soluble-silica-bearing reaction environment under the tested conditions. This environment may favor the development of sulfate-bearing hydration products, the activation of primary aluminosilicate minerals, and the formation of C–S–H-like gels. The coupled variations in leachable Ca²⁺, SO₄²⁻, and Na⁺, together with the increase in calcite, decrease in albite, broadening of the absorption band at approximately 1018 cm⁻¹, and the SEM-observed needle/fibrous products, flocculent gels, and reduced visible pores, collectively support the interpretation that KDJ-II promotes particle cementation, pore filling, and microstructural densification. Overall, this study indicates that, under the selected mixture proportion and curing condition, KDJ-II can improve the early strength and stiffness of cement-stabilized loess by modifying the early reaction environment and promoting the coordinated development of hydration-related products and a denser microstructure.

Fischer–Tropsch (FT) wax is widely used as an organic warm-mix asphalt (WMA) additive, lowering binder viscosity during construction while improving high-temperature deformation resistance in service; however, the comparative responses of SBS-modified asphalt to different FT wax grades remain insufficiently understood. Sasobit and three FT waxes with different carbon-chain ranges (FT 80, FT 90, FT 100) were incorporated into SBS-modified asphalt at about 7.0 wt%, and their effects on macroscopic performance, rheology, molecular packing, and diffusion were evaluated using physical-property tests, rotational viscosity, dynamic shear rheometer (DSR) testing, and molecular dynamics (MD) simulation. In the MD analysis, the wax additives were represented by linear alkane molecules with different chain lengths, and the systems were subjected to structural optimization, annealing, and NPT equilibration using the COMPASS III force field before the molecular descriptors were evaluated. The experimental results showed that all four additives produced a trade-off between increased high-temperature stiffness and reduced low-temperature ductility. Sasobit gave the strongest viscosity reduction (>70% above 165 °C), while FT 90 and FT 100 showed more stable, predictable viscosity–temperature behavior favorable for a wider construction window. DSR results showed higher complex modulus and lower phase angle for all modified binders at low frequencies, suggesting an increased elastic contribution and greater resistance to deformation under the tested rheological conditions; FT 80 produced the greatest stiffening but also the largest free volume and loosest molecular packing, whereas FT 100 increased cohesive energy density and reduced free volume, reflecting denser packing and stronger intermolecular cohesion. MD simulations revealed that FT wax enhanced short-time local molecular mobility and segment diffusion in its molten state (explaining the warm-mix viscosity reduction), whereas macroscopic stiffening and ductility loss at ambient temperatures were dictated by wax microcrystallization and physical network constraints that restricted long-range chain relaxation. By comparing three FT wax grades and Sasobit under the same experimental dosage and testing framework, this study provides a controlled assessment of the relationships among wax-grade characteristics, binder-scale rheological responses, and MD-derived molecular descriptors.

Based on the theory of elastic layered system, this paper establishes a three-dimensional finite element model of cement concrete overlay structure on old cement concrete pavement with the Abaqus program, and analyzes the influence of modulus change of old cement concrete pavement, modulus change of composite foundation and various overlay thickness on the load stress at the most unfavorable position of different overlay bottom. The analysis results show that before microcracking the old cement concrete pavement, it is necessary to treat the diseases such as voids at the bottom of the old cement concrete slab to ensure the stability of the strength of the old cement concrete slab after microcracking. The strength of the old cement concrete slab after microcracking is not as high as possible, and the strength of the old cement concrete slab is the best at 4000 Mpa. The process of road reconstruction should be timely, the foundation should be reinforced, and its strength should be kept at 180 MPa; the recommended thickness of cement concrete overlay is 18 cm.

In northwestern China, loess is abundant whereas suitable aggregates for rural pavement bases are scarce, yet the transfer from laboratory stiffness of stabilized loess to field support and cement concrete slab response remains unclear. This study aims to establish an E_i–E_t–pavement-response framework for cement–curing agent composite-stabilized loess and loess–sand mixtures. Compaction, unconfined compressive strength and uniaxial compression modulus tests were conducted; E_t was calculated using a specification-based method, checked by falling weight deflectometer (FWD) back-calculation, and introduced into a three-dimensional finite element model. Composite stabilization markedly improved base stiffness because cementation, curing agent-assisted bonding, gradation optimization and skeleton–filling effects produced a denser load-bearing structure. After 90 days, the compressive modulus increased from 225 MPa for 6% cement-treated loess to 570 MPa for the 45% loess–sand mixture. The calculated E_t agreed well with FWD back-calculated field values (R² = 0.91). Increasing E_t from 98.8 to 155.7 MPa reduced slab-bottom stress from 1.7449 to 1.1095 MPa and vertical displacement from 1.7102 to 0.2654 mm. Field engineers can use E_t to select local loess-based base materials and coordinate base and slab thickness, provided that compaction quality, water stability and long-term durability are verified.

The remediation of saline-alkali land is jointly influenced by stratigraphic structures, engineering interventions, and temperature fluctuations. In this study, apparent electrical conductivity (ECa) dynamics were monitored across pre-, mid-, and post-remediation stages in the Jingtai Irrigation District, Gansu Province, using the GEM-2 multi-frequency electromagnetic induction technique with temperature calibration. Results showed that spring leaching driven by irrigation and drainage significantly reduced soil ECa, with reduction proportions exceeding 70% across frequencies. During the growing season, a pattern of near-surface salt accumulation coupled with deeper desalination emerged; subsurface drainage effectively suppressed capillary salt return, achieving 84.1% lower-depth desalination despite an increase in near-surface responses across 63.3% of the area. One year post-remediation, substantial apparent desalination was achieved, with the 5325 Hz frequency response (representing deeper cumulative induction) exhibiting the highest reduction in intensity (net ECa decrease of 29.7 mS/m; 81.6% high-efficiency area). Crucially, the subsurface pipe drainage system substantially outperformed non-drained treatments across all monitored frequencies. Annually, the 5325 Hz band (associated with deeper cumulative responses) showed maximum drainage benefit yielding a mean ECa decrease of 33.09 mS/m and an 84.9% high-efficiency proportion, compared to 27.94 mS/m and 75.8% in non-drained sections. A paired t-test indicated that this difference is statistically significant (t = 4.1231, p = 4.16 × 10⁻⁵). This network also enhanced leaching represented by higher-to-intermediate frequency responses, yielding average ECa drops of 24.34 mS/m at 63,025 Hz and 21.68 mS/m at 18,325 Hz (versus 19.44 mS/m and 17.94 mS/m without drainage, respectively). These findings indicate that subsurface drainage systems successfully reshape local water-salt dynamics, providing robust data support for precise salinization regulation.