A two-lift gradient design for airport pavements has been proposed to mitigate the functional degradation, especially the salt-frost (S-F) damage induced by deicing slat fluids. Herein, this study focuses on elucidating the mechanism and improvement of incorporating mineral admixtures in the development of a novel S-F resistant surface concrete material, which is of great significance for delaying the functional deterioration of pavement surface in northern China. The results indicated that the filling effect and secondary hydration reaction between the fly ash (FA) and silica fume (SF) and cement hydration products results in a dense spatial network structure, effectively reducing porosity and optimizing pore structure. It was found that SF can effectively improve the frost resistance and salt corrosion resistance of cement mortar, while the influence of FA depends on its content and environmental conditions. The incorporation of FA and SF significantly enhanced the structural density of cement concrete and reduced chloride ion permeability. The improvement in impermeability is most pronounced when both FA and SF are used in combination. In addition, a fitting equation between the admixture content and chloride ion permeability has been established, demonstrating good fitting results. In non-frozen saline soil areas, a large amount of FA or SF could be incorporated; in seasonally frozen areas, the priority should be given to SF to ensure salt corrosion resistance and frost resistance. The findings of this study provide a scientific basis for sustainable airport pavement construction in northern China.

The current investigation examines the fluctuating behaviour of stiff pavement built on a two-parameter base and is influenced by aircraft loading impacts. This investigation is driven by the necessity for an accurate evaluation of pavement behaviour under elevated stress scenarios caused by aircraft, which can guide pavement design and upkeep. A stochastic numerical model, the vehicle-pavement interaction model (VPI), was created using a comprehensive 3D dynamic model of an aircraft vehicle and stationary runway roughness profiles. The rigid pavement is simulated using a computationally efficient 1D finite element mathematical model incorporating six DOF. The Pasternak model represents the soil medium, incorporating shear interaction between the spring elements. The pavement's irregularities are considered and replicated using a power spectral density (PSD) function. This assembled model was used to investigate the dynamical reaction of concrete pavement vibrations caused by the passing of an aircraft vehicle using MATLAB code. The dynamic governing differential equations of the aircraft's motion are developed and coupled with the pavement system equations. The coupled system is then solved in the time domain using the direct computational integration approach with the Newmark-Beta integration scheme, explicitly utilizing the linear average acceleration method. This approach is employed to resolve the equations that govern and assess the performance of the connected system. The current findings are being compared to existing analytical outcomes to verify the precision of the current coding. The research examined the impact of various pavement and aircraft vehicle behaviors and factors on the dynamic response of pavement, including the speed, main and auxiliary suspension components, mass and the load position of the aircraft, also the damping, random roughness, thickness, span length and elastic constant of the pavement, even, the modulus of subgrade of the foundation, the rigidity modulus of the shear layer. The findings demonstrate notable influences of aircraft speed and pavement surface roughness on various response parameters. Specifically, the results reveal that a higher subgrade modulus leads to decreased deflection, rotation, and bending moments. Conversely, longer span lengths tend to elevate response parameters while simultaneously reducing shear force. In conclusion, the results highlight the significance of critical factors, including velocity and subgrade modulus, in forecasting the performance of pavement subjected to aircraft loads. The present research is confined to the investigation of the dynamic's performance of the VPI simulation of airfield rigid pavement. The findings from this study can be expanded on by paving engineers to improve the structural effectiveness and reliability of the pavement, serving as a basis for subsequent fatigue analysis in response to diverse dynamic loads such as earthquake, temperature and vehicle load.

Expansive clay soil is known to cause damage to pavements due to its volume fluctuations with changes in moisture content, a phenomenon observed globally in many countries. Implementing suitable stabilisation treatments is crucial for improving the mechanical and hydraulic properties of the expansive clay subgrade. While cement and lime have traditionally been widely used as soil stabilisers, there is a growing emphasis on sustainable engineering due to increased awareness of global warming. Seeking alternative green and sustainable materials for soil stabilisation is demanded now, and one such alternative is using ethylene-vinyl acetate (EVA) copolymer emulsion. However, the use of EVA copolymer emulsion for stabilising expansive clay has been relatively underexplored in existing studies. This study evaluates the feasibility of utilising EVA copolymer emulsion for stabilising expansive clay subgrade through comprehensive laboratory tests to assess the mechanical (compaction, unconfined compressive strength, California bearing ratio, resilient modulus, and direct shear), hydraulic (soil-water retention curve and swellshrinkage), and micro-chemical (thermogravimetric analyses and scanning electron microscopic) performance of the soil. The experimental results indicate that the inclusion of 1 % EVA copolymer emulsion into the expansive clay provided the highest mechanical properties, resulting in an increase in the unconfined compressive strength, soaked California bearing ratio, resilient modulus, and cohesion by 8.8 %, 177.8 %, 35.8 % and 19.4 %, respectively. Swell-shrinkage behaviour was also improved with the addition of EVA copolymer, with 1 % EVA copolymer presenting the lowest swell-shrinkage index of 3.19 %/pF (14 % decrease in shrink-swell potential compared to the untreated clay).

This research explores the use of cup lump rubber (CLR), an agricultural by-product, as a component in controlled low-strength material (CLSM) for pavement applications in road construction. Two distinct CLSM mixtures were developed: one based on cement and the other on alkali activation. The study evaluated the workability, mechanical properties, and microstructures of both CLSM formulations. Key fresh properties, including slump flow, setting time, and bleeding, were analysed to assess their impact on the self-compaction process. Mechanical characteristics such as unconfined compressive strength, resilient modulus, and wave velocities were also measured. Some CLSM mixtures, both cement-based and alkali-activated, were found to meet the requirements for soil cement bases and subbases. Notably, the resilient modulus values showed significant improvement after 28 days, with certain mixtures achieving subbase-quality gravel standards. The study concludes by recommending the use of both cement-based and alkali-activated CLSMs in pavement design, highlighting their potential to enhance the field of pavement engineering.

Moisture accumulation within road pavements, particularly in unbound granular materials with or without thin sprayed seals, presents significant challenges in high-rainfall regions such as Queensland. This infiltration often leads to various forms of pavement distress, eventually causing irreversible damage to the pavement structure. The moisture content within pavements exhibits considerable dynamism and directly influenced by environmental factors such as precipitation, air temperature, and relative humidity. This variability underscores the importance of monitoring moisture changes using real-time climatic data to assess pavement conditions for operational management or incorporating these effects during pavement design based on historical climate data. Consequently, there is an increasing demand for advanced, technology-driven methodologies to predict moisture variations based on climatic inputs. Addressing this gap, the present study employs five traditional machine learning (ML) algorithms, K-nearest neighbors (KNN), regression trees, random forest, support vector machines (SVMs), and gaussian process regression (GPR), to forecast moisture levels within pavement layers over time, with varying algorithm complexities. Using data collected from an instrumented road in Brisbane, Australia, which includes pavement moisture and climatic factors, the study develops predictive models to forecast moisture content at future time steps. The approach incorporates current moisture content, rather than averaged values, along with seasonality (both daily and annual), and key climatic factors to predict next step moisture. Model performance is evaluated using R2, MSE, RMSE, and MAPE metrics. Results show that ML algorithms can reliably predict long-term moisture variations in pavements, provided optimal hyperparameters are selected for each algorithm. The best-performing algorithms include KNN (the number of neighbours equals to 15), medium regression tree, medium random forest, coarse SVM, and simple GPR, with medium random forest outperforming the others. The study also identifies the optimal hyperparameter combinations for each algorithm, offering significant advancements in moisture prediction tools for pavement technology.

This study conducted an experimental and numerical investigation on the stabilization of clayey subgrades using nano-silica and geogrid reinforcement. Nano-silica was incorporated in varying contents (0-4%) to assess its effects on Atterberg limits, compaction behavior, shear strength, and California bearing ratio. The results showed optimal performance at 2.5% nano-silica, with reduced plasticity index and enhanced dry density, cohesion, friction angle, and bearing capacity. A three-dimensional finite element model was developed to simulate subgrade behavior under cyclic loading, incorporating the effects of both nano-silica and geogrid layers. The model was calibrated using laboratory data to reflect observed settlement and stress distribution. The numerical results confirmed that nano-silica reduced settlement significantly up to the optimal content, while geogrid reinforcement further enhanced load distribution and reduced displacement. The combination of nano-silica and geogrid resulted in improved mechanical performance of the subgrade. These findings demonstrate the effectiveness of integrating chemical stabilization and mechanical reinforcement in clayey soils to improve structural capacity and reduce long-term deformation, providing a viable solution for pavement subgrade enhancement.

This study evaluated the stabilization of dam sediment using a blended binder of eucalyptus wood ash (EWA) and cement for cost-effective and environmentally safe pavement material development. The sediment is classified as a sandy lean clay. EWA, a pozzolanic byproduct, was used as a partial cement replacement to enhance the material's geotechnical properties and reduce environmental impact. The optimized mixture showed a 12-fold increase in unconfined compressive strength (1.4 MPa) and a California bearing ratio of 70%, meeting Thailand Department of Highways' specifications for subbase and base layers. The microstructural analysis confirmed the formation of calcium silicate hydrates, improving durability and reducing weight loss by 30% under wetting-drying cycles. Leachate tests showed that heavy metal concentrations remained within regulatory limits. EWA also reduced costs by 2.6 times compared to conventional stabilization methods, highlighting its potential for pavement applications.

The effectiveness of zeolitic tuff (ZT) based geopolymer stabilization as a sustainable alternative to conventional cement stabilization for expansive soils is investigated in this study. Mechanical and geotechnical properties of geopolymer stabilized soil are evaluated in terms of ZT content, sodium silicate to sodium hydroxide (NS:NH) ratio and curing time. Soil improvement was assessed by laboratory tests, unconfined compressive strength (UCS), plasticity, compaction, and free swell tests. The test results show that the geopolymer stabilization increases the UCS significantly, as the NS:NH=2:1 mixture attains the maximum UCS of about 5.0 MPa in 28 days of curing, representing a 40 % increase over 12 % cement-stabilized soil. Furthermore, geopolymer-stabilized soils show a higher swelling reduction with free swell percentages as low as 0.25 %, a 42 % improvement compared to cement. The environmental assessment shows a 19 % lower CO2 emission per MPa of strength for geopolymer stabilization compared to cement-based stabilization, making it an eco-friendly choice. Pavement performance analysis using the Mechanistic-Empirical Pavement Design Guide (MEPDG) indicates that geopolymer-stabilized subbase layers improve structural integrity while reducing overall pavement rutting and fatigue cracking. Scanning Electron Microscopy (SEM) results validate the creation of a dense geopolymer matrix structure that enhances the strength and stability characteristics of soil materials. The study concludes that geopolymer stabilization using ZT with optimized NS:NH ratios delivers effective, high-performing, environmentally sustainable alternatives to traditional cement.

Using air-cement-treated clay (ACTC) as a subgrade material for flexible pavements has gained widespread interest and acceptance. The mechanical properties of ACTC, including its compressive strength and elastic modulus (i.e., equivalent elastic modulus, Eeq\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_{{{\text{eq}}}}$$\end{document}) are required to realistically model its behavior in simulating pavement structure. This paper investigates the impact of different mixing proportions, particularly cement content and unit weight, on the mechanical properties of ACTC. These properties include its unconfined compressive strength (qu\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$q_{{\text{u}}}$$\end{document}) and elastic moduli (initial modulus (E0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_{{0}}$$\end{document}), secant modulus (E50\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_{{{50}}}$$\end{document}), and Eeq\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_{{{\text{eq}}}}$$\end{document}). The aim of the current study is to develop an equation for estimating the Eeq\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_{{{\text{eq}}}}$$\end{document}, which is essential for analyzing pavement structures under cyclic loading. The study involves applying continuous monotonic and cyclic loads to evaluate the mechanical properties of ACTC mixtures with varying cement contents (35-135%) and controlled unit weights (8, 10, and 12 kN/m3). Our study findings indicate that both qu\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$q_{{\text{u}}}$$\end{document} and the elastic moduli are significantly influenced by cement content and unit weight, and are well described using the effective void ratio (est\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$e_{{{\text{st}}}}$$\end{document}) parameter. The ranges for qu\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$q_{{\text{u}}}$$\end{document}, E0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_{{0}}$$\end{document}, and E50\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_{{{50}}}$$\end{document} were 51.9-411.2 kPa, 42.8-289.4 MPa, and 33.9-183.1 MPa, respectively. Eeq\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_{{{\text{eq}}}}$$\end{document} varied between 37.6 and 289.4 MPa, depending upon the cement content, unit weight, and applied stress level. Notably, Eeq\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_{{{\text{eq}}}}$$\end{document} values decreased with increasing vertical stress. A simplified equation, accounting for the combined effects of cement content and unit weight on the Eeq\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_{{{\text{eq}}}}$$\end{document} variation under different stress levels, is developed and recommended for practical use in designing ACTC mixtures for pavement analysis.

Silt soil is widely distributed in coastal, river, and lacustrine sedimentary zones, characterized by high water content, low bearing capacity, high compressibility, and low permeability, representing a typical bulk solid waste. Studies have shown that cement and ground granulated blast furnace slag (GGBFS) can significantly enhance the strength and durability of stabilized silt. However, potential variations due to groundwater fluctuations, long-term loading, or environmental erosion require further validation. This study comprehensively evaluates cement-slag composite stabilized silt as a sustainable subgrade material through integrated laboratory and field investigations. Laboratory tests analyzed unconfined compressive strength (UCS), seawater erosion resistance, and drying shrinkage characteristics. Field validation involved constructing a test with embedded sensors to monitor dynamic responses under 50% overloaded truck traffic (simulating 16-33 months of service) and environmental variations. Results indicate that slag incorporation markedly improved the material's anti-shrinkage performance and short-term erosion resistance. Under coupled heavy traffic loads and natural temperature-humidity fluctuations, the material exhibited standard-compliant dynamic responses, with no observed global damage to the pavement structure or surface fatigue damage under equivalent 16-33-month loading. The research confirms the long-term stability of cement-slag stabilized silt as a subgrade material under complex environmental conditions.