Search Results (165)

In this paper an experimental study and comparative analysis of temperature and moisture in pavements and their soil bases on experimental road sections located in two southern metropolises of Kazakhstan—in the cities of Almaty and Shymkent—were conducted. The temperature and moisture values were measured by systems for long-term continuous monitoring of temperature and moisture in structural elements of roads. Sensors were installed at ten locations within the pavements and soil bases at depths ranging from 2.5 cm to 270–275 cm below the pavement surfaces. The temperature and moisture monitoring period extends from 21 October 2024 to 31 December 2025. Temperature and moisture readings were recorded hourly. It has been established that the temperature conditions of pavements and their soil bases in the two cities are qualitatively the same, and the quantitative differences are small: air temperatures and soil temperatures at depths of 2.5 cm and 10 cm in Shymkent are higher than in Almaty by an average of 4.75 °C, 5.69 °C and 2.12 °C, respectively. These facts make it possible to use a single methodological approach to account for temperature changes in the design of new roads and in the operation of existing roads. It is recommended to pay attention to ensuring the resistance to rutting and fatigue cracking of asphalt concrete layers of pavement. The moisture regime at the experimental section in Almaty up to 130–140 cm depth is unstable due to seepage of precipitation and surface water through the stone mastic and the two coarse-grained porous asphalt concrete layers of the pavement; in Shymkent the pavement and the soil base have a stable moisture regime throughout the year; these features should be taken into account when calculating accumulations of plastic strains (increasing of rut depth) and fatigue damage in asphalt concrete layers of pavements while also accounting for temperature changes in them and transport facility loads in different time periods. Full article

This study investigates how asphalt layer structural combinations affect the internal mechanical response and rutting development of asphalt pavements on long steep grades. A three-dimensional Abaqus finite element model was developed for a typical semi-rigid base asphalt pavement used on long-gradient highway sections in China. Under coupled thermal and loading conditions, temperature, shear stress, shear strain, and total rut depth were analyzed, and a rutting prediction model incorporating structural-combination variables was obtained by nonlinear regression. The results show that increasing the intermediate-course thickness improves shear stress dispersion and reduces rutting. An excessively thick lower course produces stiffness incompatibility within the pavement structure, causing shear stress concentration, increasing shear deformation in the surface and intermediate courses, and aggravating rutting. The maximum longitudinal and transverse shear stresses on long steep grades occur mainly at depths of 6–12 cm and gradually decrease as deformation accumulates. Rutting is concentrated primarily in the surface and intermediate courses. The recommended asphalt layer combination for rutting resistance is 4 cm surface course + 12 cm intermediate course + 8 cm lower course. These findings provide a reference for optimizing asphalt pavement structural design on long, steep grades. Full article

Road networks providing access to forest stands, including integral parts such as timber yards, are subjected to significant loads from timber-transporting vehicles. These loads act on the road surfaces, causing them to deform. This study measured and compared the extent of deformation at two timber yards in the mountain forests of southern Poland in the Western Carpathians. These surfaces were constructed as: crushed stone (timber yard in the Ustroń Forest District) and earth (Forest Experimental Station of the University of Agriculture in Kraków). The measurements were carried out using photogrammetric techniques based on aerial surveys by an unmanned aerial vehicle. The measurements were based on networks of reference points with coordinates in local coordinate systems. During the period between the flights, timber was being stored, handled and transported at both sites. The forest administration provided data on the volume of timber delivered to and removed from the storage yard, as well as basic information on the transport vehicles. Soil samples were taken from the surface of both storage yards for laboratory analysis to illustrate working conditions—the soil type, current moisture content, organic matter content and filtration coefficient (from the soil particle size distribution curve) were determined. Digital terrestrial model (DTM) rasters obtained from both aerial surveys at each storage yard were used to calculate differential rasters, which were analysed by plotting cross-sections at selected locations and directions and by calculating the volume of changes in surface geometry between the survey dates. The observed depths of ruts reach 0.4 m at the Ustroń storage yard and 0.5 m at the LZD storage yard, whilst changes involving the displacement of soil from the ruts above the previous surface level are 0.3 m at the Ustroń storage yard and 0.4 m at the LZD storage yard. Greater deformation was observed on the earth surface (with a high organic content and poorer drainage) than on the crushed stone surface, even though the latter was covered by an uncleared layer of mud and waste left over from timber handling. Given the two-site, single-cycle design of this study, this pattern is consistent with—but cannot on its own confirm—a stabilising effect of surface reinforcement; differences in soil moisture, organic content and observation period between the two sites may also have contributed and could not be separated from the effect of surface type alone. Full article

Asphalt bridge deck pavements are highly susceptible to rutting, shoving, and interlayer slippage under high-temperature traffic conditions, where interlayer shear stress plays a decisive role. To clarify the coupled effects of thermal gradients and moving loads, this study developed a sequential three-dimensional thermo-mechanical finite element model for a double-layer pavement in Zhongshan, China. Field-recorded air temperature, solar radiation, sunshine duration, and wind speed were used to define transient thermal boundaries. The calculated temperature field was then transferred to a fully bonded moving-load model with dual rectangular contact areas and braking-induced longitudinal traction. Axle load, roadway slope, braking coefficient, and the thicknesses of the SMA-13 and AC-20 layers were varied. The predicted temperature fluctuation attenuated and the peak time was delayed with depth. The pavement surface reached 58.95 °C at 13:00, whereas the bottom of the asphalt overlay reached 46.99 °C at 17:00. Under the adopted 14:00 near-peak summer condition, increasing axle load amplified the overall response and raised the maximum asphalt-layer shear response from 0.172 to 0.223 Mpa. Roadway slope mainly affected traffic-direction stress transfer. Increasing the braking coefficient from 0 to 0.7 increased longitudinal shear response from 57.9 to 161.2 kPa in the asphalt layers and from 56.4 to 112.6 kPa near the AC-20/concrete interface. Increasing SMA-13 thickness reduced thermal and mechanical demand in the underlying layers, whereas increasing AC-20 thickness reduced the response near the concrete deck but shifted part of the tensile and shear demand toward the upper asphalt layer. Full article

The expansion of sustainable timber harvesting on peatland forests is important for forest owners, contractors, and the forest industry. This study investigated the effects of site-specific conditions on summertime harvesting operations and modeled the influence of a light nine-ton forwarder on rut formation. Three logistic mixed-effects models predicted peat surface disturbance (ROC = 0.60, 0.63, and 0.67), while a linear mixed model predicted rut depth when rutting occurred (R² = 0.35). Rut formation was associated with the number of machine passes, cumulative load, groundwater table depth, peat layer thickness, and interactions between stand and harvesting variables. The results indicate that timber can be successfully forwarded from drained peatlands with limited bearing capacity when operations are adapted to local site conditions. The findings highlight the importance of road-network planning, load management, and operator decision-making in reducing rut formation. This modeling approach also supports operator training, thereby contributing to more sustainable timber harvesting on low-bearing-capacity sites. Full article

Haul-road condition in open-pit mining affects fuel consumption, transport-cycle throughput and dump-truck mechanical loading. This study conducted a quasi-experimental field assessment of local maintenance effects on severely degraded road segments. The full cycle register contained 32,000 entries, of which 30,808 passed quality control and were used for background engineering characterization. The primary difference-in-differences (DiD) analysis used 2634 matched-control cycle–focal-segment observations, while 72,000 one-second telemetry records formed a separate 20 h dynamic validation subset. Relative to matched-control dynamics, maintenance increased RCI by 3.26 points and reduced IRI by 6.24 m/km, the apparent rolling-resistance descriptor by 2.71 percentage points and rut depth by 41.2 mm. Regression-adjusted effects were −10.6 L/cycle for fuel, −0.78 min for cycle time, +10.7 km/h for segment speed, −0.351 g for vibration RMS and −78.2 MPa-eq. for the suspension-stress proxy. A 14-day lead-placebo/event-time diagnostic found no detectable pre-intervention divergence, and non-negative cohort-weighted group-time ATT estimates closely matched the TWFE results. The coefficients are interpreted as site-specific local intervention-window effects rather than annual fleet-wide constants. Full article

This study presents a laboratory-scale assessment of heat-assisted fly ash-based geopolymer concrete as a potential thin protective layer in one asphalt–geopolymer pavement configuration. The programme comprised water penetration under pressure, abrasion, initial skid resistance, wheel tracking, four-point-bending fatigue, mechanical strength, freeze–thaw response, de-icing-salt scaling, thermal characterization, and qualitative scanning electron microscopy. The selected geopolymer reached mean flexural, compressive, and splitting tensile strengths of 10.756, 61.058, and 3.797 MPa, respectively. Final rut depths were 1.57 mm after 7 days and 0.72 mm after 28 days, with corresponding WTSAIR values of 0.020296 and 0.014238 mm per 10³ cycles. After 10⁶ cycles at 10 Hz, 72–85% of the initial stiffness modulus remained across the tested strain levels. Mean de-icing-salt scaling was 0.500 kg/m² after 28 days and 0.995 kg/m² after 56 days. Standalone geopolymer specimens underwent full-depth water penetration, whereas no leakage through the asphalt layer was observed in the intact layered specimen during the 5 bar, 72 h test. This system-level observation supports functional tightness only under the tested intact condition and does not establish intrinsic material impermeability or long-term interface durability. Interpretation is limited to this laboratory-scale configuration: the 90 °C heat-assisted curing protocol limits transfer to conventional in situ paving; no ambient- or standard-cured control and no same-condition conventional overlay control were included; and only one composite geometry was evaluated. The findings therefore define application boundaries for further validation rather than a field-ready specification or proof of comparative superiority. Full article

Conventional pavement design methods are generally intended for highways and are not suited to the extreme loading conditions experienced by mining haul roads. This study presents an innovative pavement design for a heavily trafficked phosphate mine haul road (≈22.35 kT·day⁻¹) constructed entirely from phosphate mine waste rock (PMWR), offering a sustainable alternative to conventional aggregates. The proposed structure comprises a 0.35 m sub-base (0–100 mm), a 0.25 m base (0–63 mm), and a 0.07 m semi-granular asphalt concrete (BBSG 0–20 mm) wearing course designed to combine high mechanical performance with effective dust control. The design was validated through an integrated experimental program that included repeated load triaxial testing (RLTT), asphalt stiffness, fatigue and rutting tests, thermogravimetric analysis (TGA), and full-scale field trials involving EV₂ plate-load testing, dust monitoring, and emergency braking tests using a Komatsu 730E haul truck. The results demonstrate that the proposed pavement provides excellent structural performance. The asphalt mixture achieved a stiffness modulus of 9160 MPa, a fatigue resistance of 139.6 µε, and a proportional rut depth (PRD) of only 2.2%. In the field, the compacted sub-base and base reached average EV₂ values of 153 MPa and 181 MPa, respectively, confirming their high load-bearing capacity. The paved haul road reduced airborne dust emissions by approximately 91%, surpassing the mine’s target of 80%, while also enabling haul-truck operating speeds to double, with associated reductions in tire wear and maintenance. Despite these performance gains, the proposed solution remains economically attractive, with a construction cost of approximately 23.97 €/m². Overall, the study demonstrates that phosphate mine waste rock can be successfully transformed into a durable, cost-effective, and environmentally sustainable pavement solution for heavy-haul mining roads, providing a practical example of circular economy principles in mining infrastructure. Full article

Multiwalled carbon nanotubes (MWCNTs) and nanoalumina (nano-Al₂O₃) have each been studied separately in asphalt binders, but whether their combined thermal gain translates into microwave-induced healing at the mixture scale remains unestablished. This study aimed to evaluate, through a multiscale approach, their combined incorporation into a polymeric asphalt binder modified with 4% styrene-butadiene-styrene (SBS), focusing on mechanical performance and microwave-induced healing. Binders with 0 to 6% hybrid nanomaterial (50:50) were characterized structurally, chemically, rheologically, and thermally, and mixtures were evaluated for rutting, four-point bending fatigue, and microwave heating and healing. A content of 2.3% was selected from rheological and thermal criteria. At this content, the mixture heating rate rose from 0.18 to 0.41 °C/s (127.8%) and rut depth decreased by 22.1%. The nanomodified binder reduced the top-to-bottom Jnr_3.2 gradient from over 250% to 56–59%, indicating improved storage compatibility rather than complete stability. Fatigue life at 250 μm/m decreased by 53.7%. Despite this, healing increased by 9.6% in dynamic modulus recovery and 61.9% in fatigue healing index. Overall, hybrid nanomodification improved resistance to permanent deformation and microwave-induced healing, clarifying their combined effect, although the fatigue penalty requires further investigation. Full article

Accurate reconstruction of complex pavement surface textures is essential for reliable texture characterization and skid resistance evaluation. In this study, a three-dimensional point cloud correction method based on a quaternion rotation matrix was proposed to eliminate point cloud tilting and displacement caused by pavement slope and the initial orientation of the scanning equipment. A unified spatial rotation model was established to align the point cloud normal vector with the Z-axis while preserving the geometric relationships among points. The method was validated using a pavement model with regular sharp textures and then applied to distressed pavements containing cracks, raveling, and rutting. The results showed that the proposed method more accurately reconstructed the original elevation features and effectively avoided the peak–valley blunting and texture smoothing associated with conventional profile-fitting correction. Compared with the conventional method, the average error of mean texture depth (MTD) was reduced by 48.3%, while the error of maximum texture elevation difference (Δh) remained within 39.9%. Statistical analysis indicated that the observed differences mainly resulted from the correction strategy rather than measurement uncertainty. The proposed method improves the accuracy of pavement texture reconstruction and texture parameter calculation and provides a reference for pavement evaluation and digital pavement modeling. Full article

The use of reclaimed asphalt pavement (RAP) has been increasing due to its economic benefits and environmental sustainability. Adding RAP materials introduces age-hardened binder, which tends to increase the rutting resistance but decrease cracking resistance. This study aims to evaluate the effects of various RAP contents and binder additives on asphalt performance using the Hamburg wheel tracking test, the Semi-Circular Bending-Illinois Flexibility Index Test (SCB-IFIT) and the Indirect Tensile Asphalt Cracking Test (IDEAL-CT). Asphalt mixtures with RAP contents of 0%, 20%, 30%, 40%, and 50% were prepared using two different binder additives of Zero-M polymer cool mix asphalt additive (PCMA) and Anova vegetable oil-based rejuvenator. Based on the Hamburg test results, the rutting resistance significantly increased by adding 20% RAP but did not increase the rutting resistance any further when RAP increased from 20% to 50%. However, the increase in RAP content exhibited a negative impact on cracking resistance by lowering Flexibility Index (FI) based on the SCB-IF test by 50% or more and CT Index (CTindex) based on IDEAL-CT test by 60% or more. For each RAP content, asphalt mixtures incorporating two different additives were tested: (1) Zero-M additive at a dosage rate of 10% of the total binder with mixing/compaction temperature of 110 °C and (2) Anova additive at a dosage rate of 5% of the RAP binder with mixing/compaction temperature of 135 °C. Compared to the control specimens without additive, asphalt mixtures with Zero-M additive increased FI and CTindex by 50% except CTindex of 30% RAP mix. Zero-M additive increased the rut depth from 3 mm to 10 mm for 20% and 30% RAP mixes but, for 40% and 50% RAP contents, the rutting was less than 5 mm after 20,000 repetitions. Anova rejuvenator did not increase FI and CTindex of 30% and 50% RAP mixes but increased FI and CTindex by 50% for 40% RAP mix. Anova additive did not increase the rutting of the control mix. The SCB-IFIT test results exhibited an average coefficient of variation (COV) of 0.25 whereas the IDEAL-CT test results had a COV of 0.20. The IDEAL-CT test, with its simpler preparation process and more consistent results, is recommended as the preferred test procedure over the SCB-IFIT test. Full article

The development of recycled asphalt mixtures combining reduced production temperatures with adequate mechanical performance remains challenging in circular pavement engineering. This study assessed the performance-based redesign of a half-warm mix asphalt (HWMA) produced at approximately 90 °C with a very high reclaimed asphalt pavement (RAP) content and foamed bitumen, using previously validated cold recycled mixture (CRM) and hot recycled mix asphalt (HRMA) formulations as contextual benchmarks. An initial CRM-derived HWMA was evaluated to assess whether cold-recycling design logic could be transferred to half-warm production without added water or cement. Although the mixture showed satisfactory volumetric and moisture-related responses, wheel tracking identified rutting as the governing limitation. The mixture was redesigned by incorporating coarse steel slag aggregate (SSA) to correct the aggregate size distribution, reducing filler content and adjusting the added foamed bitumen while maintaining RAP and SSA at 98% of the aggregate skeleton. The combined redesign reduced the wheel-tracking slope in air from 1.25 to 0.32 mm/10³ cycles and the proportional rut depth in air from 28.1% to 10.4%. Nevertheless, the redesigned HWMA remained less rut-resistant than both benchmarks, confirming the need for further optimisation. It achieved stiffness close to the HRMA benchmark and a fatigue response compatible with base-layer application, although moisture durability requires further validation. Overall, the study demonstrates the feasibility of a sequential performance-based redesign approach for high-RAP HWMA while highlighting the need for systematic optimisation and field validation before broader implementation. Full article

The growing use of reclaimed asphalt pavement (RAP) in hot mix asphalt (HMA) is an important practice to achieve more sustainable pavements, as it reduces the consumption and environmental impact of virgin materials. However, aging induces binder stiffening that requires effective rejuvenation to restore overall performance. This study provides a comprehensive comparative analysis of ten chemically different waste oils—waste engine oil (WEO), waste cooking oil (WCO), yellow grease (YG), waste hydraulic oil (WHO) waste electric transformer oil (WETO), slop oil (SO), sludge-derived bio-oil (SDBO), tire pyrolysis oil (TPO), plastic pyrolysis oil (PPO), and algal residue oil (ARO)—as recycled HMA mixture rejuvenators, linking oil composition to binder regeneration and mixture performance. Binder properties were determined by rotational viscosity (RV), dynamic shear rheometer (DSR) and bending beam rheometer (BBR), whereas mixture performance was assessed in terms of Superpave mechanical properties, Hamburg wheel-tracking test (HWTT) for rutting resistance and mixture BBR for low-temperature cracking resistance. Performance grade (PG) evaluations showed that WETO and WEO restored the 50% and 75% RAP binders, respectively, to a grade close to PG 64-16 at the lowest dosages. The Superpave volumetric properties of all restored mixtures were similar to those of the control mixture, denoting corrected mixture balance and compaction level. HWTT results indicated that WETO-recycled mixtures revealed the lowest rut depth at 50% RAP, while WEO-recycled mixtures exhibited the lowest rut depth at 75% RAP after 20000 passes. Additional evidence supporting these results can be found in BBR mixture data, which demonstrated that WETO at 50% RAP and WEO/WETO at 75% RAP showed the most reduction in creep stiffness and improvement in creep rate. The correlation, regression, and PI analyses were in good agreement with the experimental results, where WETO and WEO exhibited the best overall performance at 50% and 75% RAP, respectively. In summary, these results indicate that the performance of waste oil rejuvenator in recycled HMA mixtures is highly dependent on RAP content and point to WETO and WEO as feasible, environmentally friendly options for high-RAP recycled HMA. Full article

To investigate the rutting resistance of Large Stone Asphalt Mixture (nominal maximum aggregate size of 53 mm, abbreviated as LSAM-50), this study evaluated the effects of temperature, load, and their interaction on the rutting performance of LSAM-50 through large-thickness rutting tests. It analyzed the characteristics of rutting deformation under varying thermal and loading conditions, established a permanent deformation-temperature-load dependency model, and explored the correlations between permanent deformation and high-temperature evaluation indicators. The findings indicate that the temperature-load interaction fundamentally alters the load-transfer mechanism between the viscoelastic matrix and coarse aggregates within LSAM-50, thereby activating the interlocking effect of its thick structural skeleton. The dynamic stability undergoes a pronounced reduction as temperature or load increases, peaking at a degradation rate of 40–57% within the 40–50 °C interval. Furthermore, the rutting deformation of the LSAM-50 mixture demonstrates significant temperature and load dependency; as the number of loading cycles increases, the deformation exhibits an initial rapid escalation before reaching a plateau. During temperature elevation and load escalation, the rutting deformation increases in a step-wise manner. Notably, the preliminary application of low temperatures and light loads imparts a substantial “training” effect on the material’s rutting resistance. Once the mixture is wheel-tracked to densification under high temperatures or heavy loads, negligible new deformation is generated during the subsequent cooling or unloading phases. Specifically, upon the initial unloading from 1.1 MPa to 0.9 MPa, the incremental deformation is merely 0.04 mm; upon further unloading to 0.7 MPa, the additional deformation approaches 0 mm. The established permanent deformation-temperature-load dependency model for LSAM-50 yields a high predictive correlation of 96%. Moreover, the permanent deformation exhibits robust linear relationships with 1-h rutting depth (R² = 0.95), compressive strength (R² = 0.91), and shear strength (R² = 0.97). These indicators can thus facilitate the rapid and precise estimation of permanent pavement deformation. Full article

Waste plastic aggregate (WPA) is a promising recycled material for asphalt mixtures, but its polymeric surface can weaken binder adhesion and increase moisture-related damage, even in SBS-modified systems. Therefore, a clear need exists to identify anti-stripping agents that are compatible with WPA, rather than simply increasing WPA content in asphalt mixtures. This study evaluates the interfacial and mixture-scale performance of SBS-modified asphalt mixtures containing two WPA types, namely coarse WPA and fine WPA, treated with three liquid anti-stripping agents: amine-based agent (AS-Am), organosilane coupling-type adhesion promoter (AS-OS), and ester/surfactant-based wetting agent (AS-Es). The novelty of this study lies in selecting the anti-stripping system based on WPA–binder adhesion compatibility and validating it through moisture, rutting, rheological, and fracture performance. Binder bond strength, tensile bond strength, shear bond strength, indirect tensile strength/tensile strength ratio (ITS/TSR), Hamburg wheel tracking (HWT), multiple stress creep recovery (MSCR), and semi-circular bending (SCB) tests were conducted. AS-OS showed the best overall performance. It increased binder bond strength (BBS) by 52.8% for coarse WPA and 61.5% for fine WPA, while the optimum 0.5% dosage improved tensile bond strength by 81.0% and 97.2%, respectively. AS-OS also increased shear strength by 58.8–68.3% and improved TSR to 89.0% and 86.2%. In HWT, C-OS and F-OS reduced final rut depth by 44.0% and 45.8%, respectively. SCB results further showed higher fracture work, especially for F-OS. The findings indicate that proper anti-stripping chemistry is essential for durable WPA–SBS asphalt mixtures. Full article