Solar radiation in plateau permafrost regions is strong. The asphalt pavement strongly absorbs and slowly dissipates heat, leading to significant heat accumulation on the pavement. This accumulation disturbs the underlying permafrost and eventually causes serious pavement damage. To improve the heat resistance and dissipation capabilities of asphalt pavement, a nanofluid directional heat conduction structure (N-DHCS) was suggested and analyzed in this paper. The designed structure can resist heat in the daytime due to the low thermal conductivity of liquid and dissipates heat at night through natural convection. The finite element method and laboratory irradiation experiment were employed to performed thermal analyses of N-DHCS. The results demonstrated that establishing the N-DHCS in asphalt pavements can enhance active heat dissipation capacity, which is beneficial for protecting the frozen soil in plateau permafrost regions.

Cement kiln dust (CKD) is the by-product of cement manufacturing. It is collected using air pollution control devices (APCDs) also known as electrostatic precipitators in the form of flue dust to minimize environmental hazards. This study investigates the potential use of CKD as a filler material and its novel antistripping properties on recycled asphalt pavement (RAP). CKD's chemical properties, make it desirable for improving stripping resistance of asphalt in areas prone to high rainfall or moisture exposure, but its application in RAP remains a grey area to explore. Its dual role in improving both adhesion and mechanical properties of asphalt makes it particularly advantageous, in terms of sustainability, cost and resource efficiency. The rising production cost, environmental safety concerns, and the push towards sustainable consumption/production seek alternatives for traditional antistripping agents for asphalt production, thus, CKD. This study prepared dense-graded asphalt concrete with nominal maximum aggregate size (NMAS) of 14 mm with 1%, 3%, and 5% of CKD by weight of RAP according to Malaysian standard. A total of five (5) asphalt concrete (AC14) mixtures were produced with an optimal 3% CKD used in the modified mixtures at the optimum binder content (OBC). The antistripping properties of CKD in hot mix asphalt (HMA) were assessed through indirect tensile strength test (ITS), indirect tensile stiffness modulus (ITSM) and boiling tests on the asphalt mixtures. In addition to the physical, mechanical, chemical, and structural/morphological tests, the safe inclusion of CKD in terms of heavy metals was evaluated by applying toxicity characteristic leaching procedure (TCLP) test. The findings confirm that CKD meets ASTM C150 standards for type II and type IIA hydraulic cement for use as a filler in asphalt. The fatigue cracking resistance, antistripping resistance in terms of the tensile strength ratio (TSR) & indirect tensile stiffness modulus (ITSM) tests indicated that CKD modified RAP mixes performed better than the control (CNTRL), RAP only and CKD modified RAP mixes. It also compares favourably with CNTRL + CKD mixture. Ultimately, the boiling test results indicated that CKD blended RAP mix surpassed the minimum 80% TSR for moisture damage resistance.

In modern highway construction, asphalt pavement is a widely used structural form, which is easily affected by various external conditions, among which the temperature effect is the most significant. In this paper, the cohesion model is used to simulate the structural cracks of asphalt pavement, the finite element method is used to simulate the asphalt concrete pavement model, and the temperature field simulation model of the pavement is established by using ABAQUS software, with the help of which the spatial distribution of stresses under different temperature conditions is deeply explored, and then the crack extension law during the process of temperature change is systematically investigated, and the effect of the temperature load on the degree of damage to the asphalt pavement is also studied. With the temperature change, the pavement surface layer is affected the most, and the soil base layer is affected the least. The higher the external temperature, the larger the crack expansion width inside the pavement structure, and the faster the corresponding expansion rate. The fatigue damage rate of the pavement structure is accelerated along with the increase of temperature. The research results can provide a theoretical basis for improving the high temperature performance of asphalt pavement.

Near-surface seismic refraction tomography and electrical resistivity imaging were used to study the collapse and subsidence of two asphalt roads on the campus of South Valley University in southern Egypt. The roads surround a garden where irrigation water was suspected to be the cause of the damage to the asphalt roads. Two seismic refraction tomography (SRT) lines were measured on the asphalt roads, and a single SRT line and an electric resistivity tomography (ERT) line were measured within the garden. The tomographic inversion of the SRT lines on the road shows several low velocity anomalies indicating areas of weakness beneath the asphalt. The SRT and ERT lines in the garden show a thin surface soil of fine sand and clay overlying a low electric resistivity and low seismic velocity clay layer. Examination of the results suggests that the damage to the asphalt roads could be caused by the presence of loose silt and clay soil that was used as a sub-base for the asphalt. This soil had not been compacted and engineered for use as a strong base layer. Instead, the asphalt was laid directly on top of it, which later led to the

The stabilization of asphalt pavement bases with granular soil and aggregates emulsified with asphalt is a widely used technique in road construction and maintenance. It aims to improve the mechanical properties and durability of the lower pavement layers. Currently, there is no consensus on the most suitable method for designing emulsified granular aggregates with reclaimed asphalt pavement (RAP), as it is very complex. Therefore, the methodology is generally based on compliance with one or more volumetric or mechanical parameters established in the highway regulations for conventional asphalt mixtures, which does not guarantee the optimization and characterization of the recycled mixture in the base course. In this study, granular mixtures were developed, including five with emulsion and one emulsion-free as a control mix. Granular RAP mixes were designed in this study, including five with emulsion and one emulsion-free as a control mix. The five mixes ranged from 1% to 5% emulsion and were characterized by multi-stage triaxial tests with repeated load resilient modulus (RM) and permanent deformation (PD) to evaluate their mechanical behavior. The results showed that the mixes had RM values between 350 and 500 MPa, consistent with literature values. However, they showed similar levels of accumulated deformation to the control mix without RAP emulsion. The sample with 1 % RAP emulsion exhibited a satisfactory RM value and better performance in PD than the control mix (5 mm) and showed accumulated PD values of up to 4 mm. In contrast, the other samples exhibited deformations of up to 6 mm. In this study, the multi-stagge triaxial RM and PD tests were found to be an effective predictive method for characterizing the behavior of RAP materials in base courses, regardless of the types of admixtures contained. Multi-stage resilient modulus and PD tests can be considered as a predictive method for the behavior of milled material in base courses. They were able to provide initial data for interpreting the behavior of ETB mixtures.

In this paper, the drained shear behavior of cement-stabilized recycled asphalt pavement (RAP)-lateritic soil blends is presented. The marginal lateritic soil was replaced by RAP to reduce the fine content and then stabilized by Portland cement for ground improvement and pavement applications. The effect of cement content and RAP content on the shear behavior of RAP-soil samples was evaluated through a series of drained triaxial test. The result indicated that RAP replacement ratio, cement content, and effective stress significantly affected the drained shear of RAP-soil samples. The shear strength increased with cement content and RAP content. However, the excessive RAP replacement ratio results in the reduction of peak shear strength. The brittle to ductile transition was found when effective confining pressure increased. RAP replacement increased the maximum volumetric compression and the dilatation rate of the blends as the inclusion of compressible asphalt binder increased the ductility of RAP-soil samples. The stress-dilatancy behavior of RAP-soil samples was similar to that of medium to dense soil. The stress ratio and dilation significantly depended on RAP replacement ratio, and cement content. The dilation was suppressed when effective confining pressure increased. Row's stress dilatancy equation can model the stress-dilatancy behavior of unstabilized and stabilized RAP-soil samples.

While plastic has been recognized as one of the top ten notable advancements of the 20th century, extensive utilization of plastic in its various forms has evolved into a complex concern with respect to environmental protection. The large amount of waste plastic and its low biodegradability is driving the research effort seeking alternatives to recycling plastic waste into construction materials, and recycled plastic utilization as a valuable alternative to soil, asphalt, and concrete appears to be one of the more promising solutions for beneficial use of plastic waste. Recent progress on recycled plastic utilization in transportation infrastructure systems, including content, size, shape, mechanism, effectiveness, and its applicability to soil, asphalt, and concrete, is outlined in this review paper. The effects of recycled plastic addition on the mechanical properties of soil, asphalt, and concrete are also discussed in detail. The potential for environmental disturbance and possible implementation difficulties in understanding the progress of recycled plastics utilization has also been investigated.

In this paper, a new method was proposed to decrease the heat accumulation in permafrost embankment by controlling an oriented heat transfer in asphalt pavement Two highly oriented heat-induced structures, named G-OHIS (only gradient thermal conductivity) and G+R-OHIS (combined gradient thermal conductivity and heat reflective layer), were designed by using two indexes of summertime daily heat absorption and annual net heat accumulation on the top of embankment The results showed that the heat absorptions on the top of embankments of the G-OHIS and G+R-OHIS in summer decreased by 9.9% and 23.2% respectively. The annual net heat accumulation on the top of embankment decreased by 6.2% for the G-OHIS and 37.9% for the G+R-OHIS. Moreover, the summertime mean daily temperatures on the top of embankments of the G-OHIS and G+R-OHIS reduced by 0.74 degrees C and 1.66 degrees C respectively. The annual temperature difference on the top of embankment reduced by 1.07 degrees C for the G-OHIS and 1.96 degrees C for the G+R-OHIS. The effectiveness of the G-OHIS in reducing pavement temperature was validated by an indoor irradiation test. It is expected to reduce permafrost thawing and other pavement distresses caused by permafrost thawing by controlling an oriented heat transfer in asphalt pavement. (C) 2016 Elsevier Ltd. All rights reserved.