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Steel slag was used in asphalt pavement instead of aggregate because of its huge output and good physical properties. However, the poor volume stability of steel slag formed the predominant factor that affected its extensive application. In this study, steel slag was pretreated by enzyme induced carbonate precipitation (EICP) technology. Soybean urease was used to catalyze urea to produce carbonate ions (C O 3 2 −) , which were combined with calcium ions (Ca2+) in steel slag to form white substances to reduce the quantity of free calcium oxide (f -CaO). Firstly, the effects of concentration, temperature and pH on urease activity were discussed. Secondly, the properties of steel slag were characterized by macroscopic and microscopic methods, and the volume stability of steel slag was determined. Finally, the effect of modified steel slag on the performance of asphalt mixture was evaluated. Research indicated that the activity prepared with a soybean powder concentration of 20 g/L was the best, and the micropores of the steel slag were fully filled with the generated white substances. This not only reduced the water absorption rate of steel slag of various particle sizes by about 20 % and the expansion rate by 36.9 %, but also improved the crushing resistance of steel slag. Furthermore, as the content of steel slag increased, the properties of asphalt pavement were effectively enhanced. EICP technology effectively solved the issue regarding the inferior volume stability of steel slag, and promoted the massive-scale resource application of steel slag. [Display omitted] • The utilization of EICP technology to treat steel slag was proposed. • The EICP technology effectively reduced the water absorption rate of MSS. • Compared with OSS, the content of f -CaO and the R-value in MSS were decreased. • Microscopic analysis indicated that the EICP solution had reacted effectively with steel slag. [ABSTRACT FROM AUTHOR]

Waste tire rubber particles have potential to improve the road durability and reduce road noise. However, the current research on the influencing factors and noise reduction mechanisms of rubber asphalt mixtures' noise reduction performance is not very in-depth, which hinders the balanced design of low-noise road performance and noise reduction function. This research aims to investigate the effects of dry-process rubber particle addition on the road performance and noise reduction capabilities of asphalt mixtures, clarifying the road performance enhancement and noise reduction mechanism of dry-process rubber asphalt mixtures. This study initially evaluated the high- and low-temperature performance, water stability, and fatigue performance of Stone Matrix Asphalt (SMA) mixtures with varying rubber particle contents (0 %, 1 %, 1.5 %, and 2 %) prepared using the dry -process, and clarified the modification mechanism of dry-process rubber particles from a microscopic perspective. Furthermore, explored the trend of damping characteristics of asphalt mixtures with rubber particle content through dynamic modulus tests. The dry-process rubberised asphalt mixtures sound absorption and noise reduction performance were analyzed through tire/road noise test and absorption coefficient detection. The results show that the road performance of asphalt mixture first improves and then decreases with the increase of rubber particles content. The optimal road performance of asphalt mixture is achieved when the rubber content is 1.5 %. The formed semi continuous phase network structure between rubber particles and asphalt can enhance the structural strength of asphalt mixtures, thereby improving its road performance. Rubber particles enhance the sound absorption and damping capabilities of asphalt mixtures, improving their noise-reduction performance. The 1.5 %RSMA (SMA mixture with 1.5 wt% rubber particles by aggregate) can reduce noise to 3 dB(A) compared to the 0 %RSMA mixture, and road noise levels are correlated with vehicle speed and rainwater blockage. • The optimal rubber content in RSMA was analyzed from road performance perspective. • The noise reduction and sound absorption performance of RSMA mixture were analyzed. • The mechanism causing and influencing tire/road noise were analyzed. [ABSTRACT FROM AUTHOR]

Through the viscosity-reducing and modification effects of warm-mix additives, the severe short-term thermal degradation of styrene-butadiene rubber (SBR) polymer in road construction can be mitigated, while compensating for the lack of SBR modified bitumen (SBRMB) pavement in high-temperature performance. This study investigated the road performance of SBRMB mixture warm-mixed by a novel compound consisting of Sasobit and epoxidized soybean oil (ESO) using Hamburg wheel-tracking, Marshall stability, −10 °C indirect tensile strength (ITS), freeze-thaw ITS, and indirect tensile fatigue tests. Aging susceptibility for bituminous mixtures was assessed through in-service performance, rheological property, and chemical structure aging indexes. Additionally, changes in the SBR network structure during thermal oxidative aging were observed by a fluorescence microscope. The results show that the Sasobit/ESO compound can effectively improve the resistances of SBRMB mixture to high-temperature rutting and thermal cracking owing to the complementary characteristics of its components. The moisture susceptibility of the SBRMB mixture is increased by Sasobit, whereas the Sasobit/ESO composite still provides a pronounced enhancement effect on moisture stability under the compensating action of ESO as well as the aging reaction. Compared with Sasobit, Sasobit/ESO composite is less effective in increasing the fatigue life of SBRMB mixture due to the undesirable effect of ESO, but the long-term aging action significantly reduces this discrepancy. Sasobit can compensate for the adverse influence of ESO on aging susceptibility, and consequently the short- and long-term aging resistances of SBRMB mixture are strengthened by Sasobit/ESO compound. Since Sasobit plays a decisive role, Sasobit/ESO compound is effective in mitigating the thermal degradation of SBR polymer in bituminous mixtures. • Sasobit/ESO enhances the comprehensive road performance of SBRMB mixture. • Sasobit/ESO improves the short- and long-term aging resistances of SBRMB mixture. • The degradation degree of SBR polymer can be effectively mitigated by Sasobit/ESO. [ABSTRACT FROM AUTHOR]

The recycling and reusing of reclaimed asphalt pavement (RAP) are generally restricted by the limited integration of RAP and the insufficient service life of recycled products. This research incorporated the polyurethane prepolymer (PUP) system into bitumen, creating an innovative bonding material to develop a fully reclaimed asphalt pavement (FRAP) mixture including 100 % RAP. The performance and modification mechanism of the PUP system modified bitumen (PUPB) binder, PUPB-RAP interface, and PUPB/FRAP mixture were systematically investigated. The permanent non-deformability of PUPB was effectively enhanced due to the formation of carbamide and amide, whereas the soft segment increment contributes to a slight improvement in low-temperature cracking resistance. Compared to the neat bitumen-RAP interface, the PUPB-RAP interface possessed greater adhesion and cohesion properties based on the free-surface energy measurement. The PUPB/FRAP mixture demonstrated its application prospect in regions with heavy vehicle loads, low temperatures, or dramatic seasonal variations, especially for damaged upper surface courses. The efficient utilization of RAP with the addition of a small amount of PUPB creates significant new opportunities for sustainable development and environmental footprint reduction associated with road construction and maintenance. • The application of 100 % RAP was realized by employing the PUP system as a chemical bituminous modifier. • The application prospect of fully reclaimed asphalt pavement was explored. • The chemical interactions between the bonding materials were investigated. [ABSTRACT FROM AUTHOR]

Welded galvanized steel wire mesh is fabricated from longitudinal and transverse steel wires welded at specific intervals, followed by hot-dip galvanizing. To address the issue of asphalt pavement cracking, this study incorporates the welded galvanized wire mesh between the base and surface layers, thereby reducing the stress-strain levels of the pavement structure and mitigating the stress concentration at cracks. This results in a novel reinforced asphalt pavement structure. To validate the road performance of asphalt mixtures reinforced with welded galvanized steel wire mesh, this paper presents an indoor experimental study comparing various reinforcing materials: unreinforced, glass fiber geogrid, a polyester fiberglass geotextile, and 1.0 mm welded galvanized steel wire mesh. The results demonstrate that welded galvanized steel wire mesh significantly constrains asphalt mixture deformation under wheel loads, enhancing shear strength by 58.9 % compared to unreinforced asphalt mixtures, and exhibiting robust high-temperature deformation resistance. Moreover, the flexural tensile strength of asphalt mixtures reinforced with welded galvanized steel wire mesh increased by 36.3 %, and the maximum bending and tensile strains rose by 79.9 %, showcasing exceptional low-temperature crack resistance and crack propagation properties. Additionally, the fatigue life of the asphalt mixtures was markedly improved. Comprehensive analysis indicates that welded galvanized steel wire mesh is cost-effective, enhances the integrity and continuity of asphalt pavements, and extends their service life. Over the pavement's life-cycle, this method reduces overall investment, providing a robust basis for extensive application of welded galvanized steel wire mesh in asphalt highways. • Uses 1.0 mm steel mesh to reinforce asphalt, improving strength and fatigue life. • The addition of the galvanized steel mesh enhances heat and crack resistance, extending asphalt life. • This study provides a strong basis for using the galvanized steel mesh in roads, boosting safety and cutting costs. • This technology aligns with green principles, reducing maintenance needs and cutting emissions. [ABSTRACT FROM AUTHOR]

To efficiently reduce the release of hazardous substances from road asphalt (AHS) under high temperatures, a novel low-emission asphalt was prepared with tourmaline/biochar/diatomite (TBD) composite and base asphalt in this research. The testing and evaluation method for the emission reduction efficacy of AHS was proposed. The preparation process parameters of TBD modified asphalt (TBD-A) were optimized. The micromorphology and the road performance of TBD-A were deeply studied. The AHS emission characteristics and emission reduction effects of TBD-A were clarified. The optimal ratio of TBD was recommended. The results indicated that the optimal shear temperature, shear speed, and shear time for preparing TBD-A were recommended as 150℃, 3000 rpm/min, and 40 min, respectively. TBD was equally dispersed throughout asphalt and worked well with it according to scanning electron microscopy. TBD improved the temperature sensitivity, enhanced the high temperature and aging resistance, improved the deformation resistance, and promoted the low temperature cracking resistance of asphalt. TBD-A emitted fewer AHS than basic asphalt. Increasing temperature and TBD content enhanced the emission reduction effect of TBD-A. The highest emission reduction rate of AHS exceeds 70 %. Considering the road performance and emission reduction efficiency of TBD-A, the TBD content was recommended as 20 %. • The testing and evaluation method for the emission reduction efficacy of TBD-A has been proposed. • The preparation process parameters of TBD-A have been optimized. • The road performance of TBD-A has been deeply studied. • The emission reduction efficacy and mechanism of TBD-A have been clarified. [ABSTRACT FROM AUTHOR]

The demand for skid-resistant and wear-resistant alternative aggregates in the preparation of ultra-thin friction course (UTFC) asphalt mixtures is a key direction for achieving high durability and low-carbon development in pavement maintenance. As a typical industrial waste, steel slag with high alkalinity and strong adhesion can facilitate the mechanical property of asphalt mixtures. However, few researches focused on the impact of steel slag on the comprehensive road performance of UTFC mixtures. Hence, the issue merits systematic exploration. In this study, the chemical components, microstructure and morphological characteristics of three steel slags (GXSS, HBSS and IMSS) obtained from different sources were surveyed. Then the stone matrix asphalt (SMA)-5 and open-grade friction courses (OGFC)-5 mixtures with different steel slags were fabricated. And their comprehensive road performances were quantitatively explored via the improved radar chart. The results indicate that steel slag with approximately 40 % Ca content, about 20 % Fe content, irregular shapes and tiny pores endows its wear resistance and strong adhesion. IMSS demonstrates the largest average angularity and form 2D values of 3850 and 7.28, respectively, representing its significant crowding function and interlocking structure. Incorporating steel slag remarkably reinforces the rutting resistance, skid resistance and anti-interlayer shear performance of UTFC. While the effect of water stability and crack resistance of UTFC depend on the category of steel slag. All three steel slags manifest the improvement function on the comprehensive assessment indexes (CAI) of OGFC-UTFC. IMSS-OGFC reveals the optimal comprehensive road performance, achieving the highest CAI of 0.9909. It is inferred that steel slag is more suitable for OGFC-UTFC than SMA-UTFC due to its relatively high CAI and consistent performance regardless of the steel slag type. • Steel slag demonstrates higher average angularity and form 2D values than basalt. • Incorporating steel slag remarkably reinforces the skid resistance and interlayer shear resistance of UTFC. • IMSS-OGFC reveals the optimal comprehensive road performance. • Steel slag is more suitable for OGFC-UTFC for its higher CAI than SMA-UTFC. [ABSTRACT FROM AUTHOR]

Waste additives have been used for emulsified asphalt cold recycled mixture (CRM) in recent years. However, the action mechanism of waste additives in CRM is not clear, the reasonable utilization of waste additives worths to be explored for improving the performance of CRM as well. Therefore, this work investigated the influence of different waste additives and/or cement on the microstructure and basic road performance of CRM. Three types of waste additives (rice husk ash-RH, fly ash-FA, flue dust-FD) with different contents (0.75 %, 1.5 % and 3.0 %) and composite additives (0.75 % cement+0.75 % waste additive) were chosen to prepare CRMs. Optical microscope, environmental scanning electron microscopy and X-ray diffraction tests were employed to characterize microstructures of CRMs, and basic road performance was obtained by air void, indirect tensile strength (ITS) at 15°C, wheel tracking, low-temperature ITS and freeze-thaw ITS tests. The results showed that adding FA can accelerate the breaking of asphalt emulsion to some extent. Meanwhile, some locally continuous and denser microstructures composed of waste additives (dispersed phase) and demulsified asphalt binders (continuous phase) are formed in CRM after 2 days of curing. Besides, when the FA and cement are utilized in combination, a pozzolanic reaction can occur and more hydration products are generated in CRM. Compared with the CRM with 1.5 % cement, the CRM with 1.5 % waste additive shows higher ITS (especially for FA) and low-temperature cracking resistance, whereas the air void, water stability and high-temperature stability are lower. Compared with the CRM with only 1.5 % waste additive, the 0.75 % cement+0.75 % waste additive can effectively improve the high-temperature stability and water stability (particularly for FA), while maintaining the low-temperature cracking resistance essentially unchanged. Additionally, waste additives partially or completely substituting cement in CRM can obviously reduce carbon emissions. • The interaction of waste additive, emulsified asphalt and/or cement in CRM was revealed. • The feasibility of waste additive completely or partially replacing cement in CRM was analyzed. • A denser microstructure composed of waste additives and demulsified asphalt binders is formed in CRM after 2 days curing. • Using waste additives and cement in CRM simultaneously can combine their advantages and cover their shortages. [ABSTRACT FROM AUTHOR]

The volume expansion risk of steel slag is a predominant challenge hindering its usage as an alternative aggregate in road pavements. In this study, the interfacial adhesion properties of base asphalt-basalt, base asphalt-steel slag, rubber modified asphalt (RMA) -basalt and RMA-steel slag were compared employing both experiment and molecular dynamics simulation. The volume stability and road performance of the asphalt mixture was also explored. The results showed that the residue rate of the RMA asphalt mixed with steel slag aggregates showed an increase from 87.5 % to 95.7 % compared to base asphalt after 100°C boiling water test. The interfacial adhesion between steel slag and asphalt surpasses that of basalt and asphalt, with the use of rubber modified asphalt further enhancing the adhesion with steel slag aggregates, as investigated through quantitative evaluation of interface adhesive work. The enhanced interaction between steel slag and RMA was primarily due to the integration of acidic functional groups from rubber chain with the alkaline active constituents (f-CaO) of steel slag aggregates, as confirmed by molecular dynamics simulations and accurate density functional theory calculations. Furthermore, the volume stability and road performance of the steel slag stone mastic asphalt were also greatly improved compared with basalt asphalt mixture. The dynamic average stability of RMA steel slag mixture was 9218 cycles/mm and the expansion rate of steel slag asphalt mixture under did not exceed 1.2 % after 216 hours water immersion. Therefore, this study provides an alternative aggregate for road pavement and a sustainable recycling strategy for the steel slag waste. • Volume expansion risk of the steel slag asphalt mixture was greatly reduced. • The integration of acidic functional groups from rubber modified asphalt enhanced interfacial adhesion with steel slag. • An unparalleled perspective on the binding mode of the asphalt and steel slag by MD simulation and DFT calculation. [ABSTRACT FROM AUTHOR]

Achieving high-quality utilization of reclaimed asphalt pavement (RAP) is challenging due to the subpar technical performance of aggregates and the aging of asphalt within RAP. This study investigates the use of epoxy asphalt (EA) and steel slag to enhance recycled asphalt mixtures (RAM) for superior performance and increased RAP content. The rheological performance of epoxy asphalt (EA) was evaluated using a dynamic shear rheometer (DSR), and its curing process was analyzed. Steel slag-epoxy recycled asphalt mixtures (SRAM) with 40 %, 80 %, and 100 % RAP were prepared, and their road performance was assessed through Marshall, wheel tracking, and semi-circular bending tests. Additionally, the effects of steel slag's surface morphology and element distribution on moisture and skid resistance were examined. The volatile organic compound (VOC) emission characteristics were also studied. The results show that EA forms a uniformly dispersed structure, providing excellent high-temperature deformation resistance. EA and steel slag significantly enhanced the road performance of SRAM, with SRAM-80 (80 % RAP, 20 % steel slag) achieving a dynamic stability of 15027 times/mm. Steel slag improved SRAM-80's skid resistance, with a British pendulum number (BPN) of 68 and a texture depth (TD) of 0.5889 mm. Compared to 60/80 asphalt, EA reduced VOC emissions by over 75 %. Incorporating 80 % RAP and 20 % steel slag into RAM effectively utilizes RAP while enhancing performance. • High-quality utilization of reclaimed asphalt pavement (RAP) was achieved by using steel slag and epoxy. • The performance of steel slag-epoxy recycled asphalt mixture (SRAM) with various RAP content were studied. • SRAM has excellent high-temperature deformation resistance and remarkable environmental benefits. • The recommended content of RAP and steel slag is 80 % and 20 %, respectively. [ABSTRACT FROM AUTHOR]

Recently, there have been many studies on the inhibition of asphalt fumes; however, the study on the inhibition of component of asphalt fumes is still limited. In this paper, four kinds of fumes and odor suppressant were selected based on the principles of physical adsorption and chemical inhibition, and the particulate matter of asphalt fumes was taken as the object of fume suppression, and the benzene organic matter among volatile organic compounds was taken as the object of odor purification. The inhibition effects of fumes and odor suppressant on asphalt fumes particulate matter and volatile organic compounds were investigated based on the gravimetric method and gas chromatography-mass spectrometry. The effects of fumes and odor inhibitors on rheological properties were obtained by dynamic shear rheometry. Results showed that asphalt fumes particles and benzene organics in volatile organic compounds were used as fumes suppression and odor purification targets, respectively. Activated carbon was the most effective in suppressing fumes with 65.7 %. It was 1.2 times more effective than diatomaceous earth and Odor Cleaner A. Odor cleaner B had the highest suppression rate of 76.4 % on the benzene component of volatile organic compounds released from asphalt binder. Activated carbon also had a good suppression effect on the benzene component of volatile organic compounds released from asphalt binder, with suppression rate of 59 %. Fumes and odor suppressants had a low impact on asphalt pavement performance, especially suppressants based on chemical inhibition principles. • Experimental parameters affect the release of asphalt fumes. • Activated carbon inhibited asphalt fumes by 65.7 %. • The inhibition of benzene organic compounds by odor cleaner B was 76.4 %. • Verify the road performance of asphalt binder. [ABSTRACT FROM AUTHOR]

Given the growing demand for sustainable road construction materials, this research aims to evaluate the synergistic effects of incorporating recycled concrete aggregate (RCA) and reclaimed asphalt pavement (RAP) in asphalt mixtures. Induction heating was also utilized to enhance the self-healing ability of asphalt mixtures, with the intention of prolonging their lifespan and mitigating environmental impacts. This research assessed the pavement performance of recycled asphalt mixtures (RAM) with different RCA and RAP dosages. The induction heating performance, cooling performance, and effective heating depth of RAM were tested. Lastly, the cumulative healing efficiency of the RAM was evaluated under multiple "fracture-healing" conditions. Findings indicated that the inclusion of RCA and RAP negatively influenced the water stability, high-temperature deformation resistance, and crack resistance at low temperatures of the RAM. However, when the RCA content was 20 % and the RAP content did not exceed 20 %, the road performance of the RAM met the requirements. The contents of the RCA and RAP had no discernible effect on the RAM's induction heating capability. Moreover, when the RCA content was 20 % and the RAP content did not exceed 10 %, the effective heating depth of the RAM could reach 50 mm. Using fracture energy recovery rate as the healing index, after three cycles of "fracture-healing", the RAM with 20 % RCA achieved the highest cumulative healing efficiency of 291 %. The cumulative healing efficiency of recycled asphalt mixtures with 20 % RCA and 10 % RAP was close to that of normal asphalt mixtures. This research contributes to reducing the consumption of non-renewable resources, minimizing environmental impact, and maintaining or even improving the performance of asphalt pavements by optimizing the use of RCA and RAP. [Display omitted] • The synergistic use of RCA and RAP in asphalt mixtures for sustainable road construction was examined. • The optimal RCA and RAP contents for maintaining road performance were identified. • Induction heating was utilized to enhance the self-healing of recycled asphalt mixtures. • Using 20 % RCA and no more than 10 % RAP improves the cumulative healing efficiency of asphalt mixtures. [ABSTRACT FROM AUTHOR]

In order to evaluate the effects of three preparation processes, namely dry process (DP), wet process (WP) and wet/dry mixing process (MP), and resin high viscosity modifier (RHVM) on the road performance of porous asphalt mixtures, the frequency scanning, multi-stress creep recovery, and bending beam rheometer tests were used to analyze the rheological performance of resin-modified high viscosity asphalt under different processes. Uniaxial compression, Wheel tracking, Semi-circular bending and Freeze-thaw indirect tensile tests were used to test the properties of resin-modified porous asphalt mixtures under different processes. The commonly used TAFPACK-Super (TPS) modifier was a control group. Finally, the changes in the microscopic morphology characteristics and chemical composition were used to illustrate the enhancement mechanism of resin modifiers. The results showed that the high-temperature deformation resistance and low-temperature cracking resistance of RHVM modified asphalt prepared by DP and MP are weaker than that of the WP. Compared to the RHVM(WP), the J nr (3.2) of RHVM(DP) and RHVM(WP) decreased by 14.3 % and 63.8 %, the strength modulus of RHVM(DP) and RHVM(MP) increased by 21.5 %, 28.0 % and the creep rate decreased by 2.37 %, 4.45 %, respectively. As for the performance of asphalt mixture, compared to the RHVM(WP) asphalt mixture, the dynamic stability of RHVM asphalt mixture prepared by the DP and MP decreased by 17.3–18.2 %, σ s and ε s of RHVM(DP) and RHVM(MP) increased by 15–35 % and 21–29 %, respectively. The water stability of RHVM(DP) asphalt mixtures was better than that of RHVM(WP) when the mixing time reached 180 s. RHVM(WP) asphalt mixtures have superior low-temperature cracking resistance, comparable water stability, and slightly poorer high-temperature stability than that of TPS(WP) asphalt mixture. Microscopic morphology observation found that some modifier particles and asphalt binder did not realize effective mixing under the DP and MP, and infrared spectroscopy results confirmed that TPS modifiers are mainly physically co-mingled with asphalt, while the tackifier resin in the RHVM reacts with the asphalt to form new functional groups to increase the viscosity of the asphalt. • The road performance of resin porous asphalt mixtures under dry, wet and dry-wet mixed processes was evaluated. • The rheological performance of resin modified high viscosity asphalt extracted from dry, wet and dry-wet mixed process asphalt mixture was evaluated. • The modification mechanism of resin high viscosity modifiers on asphalt was discovered. [ABSTRACT FROM AUTHOR]

• The absorption peak of the sulfoxide group is apparent after long-term aging. • The stabilizer can improve the high temperature stability of asphalt effectively. • The furfural extract oil can crosslink the modifiers to form a network structure. • Degradation and polymerization occur during thermal aging of modified asphalt. In order to improve the road performance of modified asphalt binders, the macroscopic and microscopic properties of five asphalt binder samples were compared, including matrix asphalt, styrene-butadienestyrene (SBS), styrene-butadiene-rubber (SBR), stabilizer, and furfural extract oil. The five asphalt samples were mainly subjected to macroscopic experiments of penetration, softening point, ductility, viscosity and elastic recovery. Short-term aging experiments and long-term aging experiments were carried out. From this, fifteen groups of samples corresponding to before aging, short-term aging and long-term aging were obtained. All samples were subjected to infrared spectroscopy and gel permeation chromatography experiments, and experimental data were obtained for analysis. The characteristic peaks of infrared spectrum and gel permeation chromatography molecular weight in various stages, including before aging, short-term aging and long-term aging, were studied. The main characteristics of the oxidation peak and the changes in number average molecular weight, weight average molecular weight and dispersion coefficient obtained by gel permeation chromatography (GPC) were analyzed. This paper found that the absorption peak of the carbonyl group appeared after both short-term aging and long-term aging while the absorption peak of the sulfoxide group was only apparent after long-term aging. Oxidation is the main reason for the decline of asphalt pavement performance and the modifier can effectively enhance anti-aging properties. Macromolecular degradation and small molecule polymerization occur simultaneously during thermal aging of modified asphalt binders. The stabilizer group and furfural extract oil group had the best anti-aging performance and the best road performance. The macro performance indicators also reached the same conclusion. [ABSTRACT FROM AUTHOR]

• HGM and HGM/SBS modified asphalts and their mixtures are prepared. • HGM increases high temperature stability and decreases low temperature performance of asphalts. • HGM improves the cooling, high-temperature and low-temperature performances of AC-13. • HGM has no obvious effect on cooling performance of SMA-13 mixture. • It is recommended to use 5% HGM modified AC-13 mixture. High temperature in asphalt pavements often leads to rutting of asphalt pavements and heat island effects in urban areas. In this study, to improve the thermal resistance of asphalt pavement, hollow glass microspheres (HGM) modified asphalt and HGM/Styrene-Butadiene-Styrene (SBS) modified asphalt were used to prepare asphalt concrete (AC) and stone mastic asphalt (SMA) respectively. The effects of HGM on the penetration, ductility, softening point and rheological properties of asphalt binder and the cooling performance, mechanical property, high temperature stability, low temperature resistance, water stability and other properties of asphalt mixture were investigated. Finally, the composition of the thermal resistance surface layer was recommended. Results showed that, adding HGM increased the high temperature stability of both matrix asphalt and SBS modified asphalt while the low temperature performance of both the two types of asphalts decreased. For the asphalt mixture, the addition of HGM improved the cooling performance of the AC-13 mixture but had no effect on the cooling performance of the SMA-13 mixture. HGM also showed positive effects on the pavement performance of the asphalt mixtures. For the AC-13 mixture, it improved the mechanical property, high-temperature stability, low-temperature cracking resistance and immersion residue stability but had no effect on the thaw-splitting strength ratio (TSR). For the SMA-13 mixture, it improved the Marshall stability, high-temperature stability, immersion residue stability, scattering resistance while impaired the low-temperature crack resistance, TSR and anti-drainage ability. Finally, it was recommended to use 5% HGM modified AC-13 mixture as the thermal resistance surface layer. [ABSTRACT FROM AUTHOR]

Shield tunneling has emerged as a predominant method for tunnel excavation, and immediate attention is required for the disposal of excavated soil. To convert waste soils into high-quality roadbed filling materials, the lime-treated soil was improved with industry by-products (IBPs) (i.e., fly ash, soda residue and flue gas desulfurization gypsum (FGD gypsum)). A series of laboratory tests, including California Bearing ratio (CBR) tests, unconfined compressive strength (UCS) tests, drying shrinkage tests and SEM were performed to explore the effects of the content of IBPs on the mechanical and microstructural properties of lime-treated soil. The results indicate that with the addition of lime-based binders, the CBR value was improved over 10 times to more than 100%, and the swelling rate was reduced substantially from 2.57% to a range of 0.30–0.45%. After 7 days of curing, the UCS increased by 3–5 times, accompanied by a noticeable enhancement in water stability. The group with 3% lime and 5% FGD gypsum achieved a maximum UCS value and water stability coefficient (k) of 2.73 MPa and 0.76 respectively at the curing age of 28 days. Furthermore, the drying shrinkage coefficient of specimens improved with lime-fly ash and lime-FGD gypsum significantly decreased and remained at a low level around 250 × 10−6. This demonstrated potential application in mitigating road base cracking. Notably, the optimal comprehensive effect can be achieved when 3% lime and 3% desulfurization gypsum were added. This study contributes to the development of environmentally sustainable IBPs and saves traditional binders in roadway construction. ● Mechanical and microscopic properties of lime-treated soil were studied. ● Effects of hydrated calcium chloroaluminate and ettringite were reported. ● The modification mechanisms of different industrial by-products were explored. ● This study proposes an optimal ratio for engineering application. ● The benefits using industrial by-products to treat shield tunneling soil were proved. [ABSTRACT FROM AUTHOR]

To broaden the sources of subgrade filler and the utilization of Soda Residue (SR), SR was employed to modify clay by adding a small amount of lime for further stabilization, forming a Lime-Soda-Residue-Stabilized Soil (LSRSS). A set of intensive research paths was established, from testing of laboratory mechanical property, mechanism disclosure, and field verification to operational effect. Through Unconfined Compressive Strength (UCS), California Bearing Ratio (CBR), and Resilient Modulus (MR) experiments, it was concluded that with the increase in SR content, the UCS, CBR, and MR values of LSRSS showed an increasing trend then followed by a decrease, reaching their peak values, respectively of 0.62 MPa, 65.0%, 78.83 MPa, all at 30% SR content. An optimal proportion was determined for LSRSS as 6% lime, 30% SR, and 70% clay. The UCS, CBR, and MR values of optimal proportion all increased with the increase of compaction degree, but increased first and then decreased with the increase of water content. Their maximum values did not correspond to the OWC of 23% but to 27%, called the compaction water content, which was suitable for application in the actual LSRSS subgrade. Field test results showed that the UCS, CBR, and MR values were 0.85 MPa, 86.5%, and 135.7 MPa, which all were higher than the laboratory values, and the long-term road performance was outstanding. The analysis demonstrates that the better strength and road performance of LSRSS are mainly determined by the superior gradation and the reaction of three materials. The laboratory and field test results collectively provide data evidence for excellent performance and lay a solid foundation for the wider application of the LSRSS subgrade. [Display omitted] • Soda residue effectively enhances properties of high-liquid-limit clay, forming a promising subgrade material. • We have intensively investigated mechanical properties, mechanical mechanisms, and road performance of LSRSS. • Compaction Water Content instead of optimum water content is proposed for application of LSRSS. • Field tests are conducted to verify the superior practicality and durability of the LSRSS subgrade. [ABSTRACT FROM AUTHOR]

The quality of the waterproof adhesive layer significantly impacted the safety and service life of concrete bridge deck pavements. Therefore, this study focused on the preparation of the waterborne epoxy resin-polyurethane-emulsified asphalt (WEPEA) and investigated the factors influencing its road performance. The component proportions of WEPEA were determined based on tensile strength and elongation at break, while its physical and chemical properties were systematically studied. Indoor tests were conducted to investigate the impact of environmental factors and surface treatment processes on WEPEA's road performance. The research findings indicated that the optimal proportions for WEPEA were 30% waterborne epoxy resin (WER) and 8% waterborne polyurethane (WPU). WEPEA exhibited excellent bonding performance, low-temperature flexibility, adhesion, waterproof properties, and corrosion resistance. Surface contaminants, freeze-thaw cycles, and immersion in water reduced the road performance of WEPEA. Surface treatments such as surface brushing, surface grooving, and surface milling enhanced WEPEA's road performance, with surface grooving being the most effective method. According to value engineering theory, compared to other waterproof adhesive materials, WEPEA had better economic benefits as a waterproof adhesive material. • WER and WPU improved the strength and flexibility of WEPEA. • Environmental factors reduced the road performance of WEPEA. • The surface treatment process improved the road performance of WEPEA. • As a waterproof adhesive material, WEPEA demonstrated superior cost-effectiveness. [ABSTRACT FROM AUTHOR]

The escalating costs of aggregates and stringent sustainable development policies have emphasized the significance of effective high-content recycled asphalt pavement (RAP) regeneration technology. This study aims to present a novel laboratory separation and treatment approach for RAP materials, ensuring optimal performance of high-content RAP recycled asphalt mixtures. The proposed method is compared against factory-separated RAP materials in terms of agglomeration evaluation and mixture performance comparison. High- and low-temperature performance of the recycled asphalt mixture were evaluated through wheel tracking and trabecular bending tests. Furthermore, the moisture sensitivity of the recycled mixture was studied through immersion Marshall and freeze-thaw splitting tests. The uniformity and fusion between aggregates and asphalt in the recycled asphalt mixtures were meticulously analyzed using advanced techniques such as Scanning Electron Microscope and industrial Computed Tomography scans. The laboratory separation method encompasses flexible separation for 5–10 mm RAP materials and rigid separation for 10–20 mm RAP materials. Notably, the laboratory separation methods proved more effective in removing aged asphalt from the surface of 10–20 mm RAP materials compared to factory separation, thereby enhancing the adhesion between aggregates and asphalt and ensuring a more uniform recycled mixture. Although the dynamic stability of recycled asphalt mixture was reduced using laboratory separation, it still meets the requirements of relevant specifications. Moreover, the low-temperature maximum flexural tensile strain of the recycled asphalt mixture increased by 16%, with the residual stability and tensile strength ratio rising by 1.33% and 2.69%, respectively. Compared with the factory separation method, the laboratory separation method reduces the porosity percentage of the recycled asphalt mixture cross-section by 3.47%. Overall, the laboratory separation method for RAP materials provides valuable insights for enhancing the factory processing of RAP materials, contributing to the successful application of high RAP content regeneration technology in the pursuit of sustainable and cost-effective road construction practices. • Proposed a laboratory method and identified suitable parameters for RAP material separation. • Compared the efficacy of the laboratory separation method with the factory separation method. • Established that the recycled asphalt mixture exhibits superior road performance and stability. [ABSTRACT FROM AUTHOR]

The purpose of this study is to assess the effect of polyurethane solid-solid phase change materials (PUSSPCMs) and polyethylene glycol (PEG4000) on the thermoregulatory and rheological properties of asphalt, as well as their potential for regulating asphalt pavement temperature. The chemical and thermodynamic characteristics of PEG4000 and PUSSPCMs were investigated using infrared spectroscopy (FTIR), adsorption test, polarized light microscopy (POM), X-ray diffractometer (XRD), differential scanning calorimetry (DSC), thermogravimetric (TG), and atomic force microscopy (AFM). Meanwhile, the effects of PEG4000 and PUSSPCMs on asphalt road performance and micromorphology were determined by tests of thermoregulation, three major indexes, DSR segregation, and scanning electron microscopy (SEM). The results indicate that PUSSPCMs have no hydroxyl characteristic peaks of PEG4000 and isocyanate bonds after the complete reaction. PUSSPCMs exhibit better phase stability over PEG4000, the soft segment for thermal storage changes from crystalline to amorphous and is limited by the hard segment micro-region to maintain a stable solid phase. PUSSPCMs exhibit slightly weaker thermal storage properties than PEG4000, while the thermal stability and elastic modulus are stronger. PUSSPCMs-modified asphalt performs lower thermoregulation properties than PEG4000-modified asphalt, which improves with the increasing soft segments. Furthermore, the advantages of PUSSPCMs-modified asphalt are in terms of basic physical, rheological properties and storage stability. The micromorphology of PUSSPCMs-modified asphalt shows no visible cracks compared to PEG4000-modified asphalt and flattens with soft segment rises, which contributes to the thermoregulation and rheological properties of asphalt. • The phase change behavior, thermal storage properties, and mechanical properties of PUSSPCMs and PEG4000 are investigated. • The thermo-mechanical properties of PUSSPCM and rheological properties of PUSSPCM-modified asphalt are investigated. • The correlation of the thermo-mechanical properties of PUSSPCMs and PEG4000 with the thermoregulation and rheological properties of modified asphalt was analyzed. • Micro-morphological characteristics of PUSSPCMs-modified asphalt and PEG4000-modified asphalt are observed. [ABSTRACT FROM AUTHOR]

Purification of urban runoff is of great significance for reducing the pollution of receiving water bodies and protecting the urban water environment. Zeolite powder is added to porous asphalt mixture in this study to improve the purification effect. The influence of zeolite powder on the road performance was evaluated to determine its optimal content. The effects of air void content, suspended solid (SS) concentration, heavy metal concentration, and rainfall intensity on the purification effect were studied and the purification durability was also analyzed. The experimental results show that the addition of zeolite powder has no obvious impact on road performance of porous concrete and can increase the removal rates of SS, chemical oxygen demand (COD), Zn2+, and Pb2+ by 6.4%, 25.2%, 20.6%, and 23.5%. The removal rates of SS, COD, Zn2+, and Pb2+ increase with the increase in SS concentration while the removal rate of heavy metals decreased with the increase in heavy metal concentration. Large air void content and rainfall intensity result in a decrease in the adsorption and purification effect. The removal rate shows a rapid decline since the sixth year, especially for SS, indicating that maintenance should be conducted at this time. • Zeolite is added into porous concrete to improve the purification effect. • Binder drainage test and abrasion test were used in the design process. • Effects of pollutant concentration and rainfall intensity were studied. • Purification durability of porous concrete was analyzed. [ABSTRACT FROM AUTHOR]

Polyurethane-modified asphalt (PA) stands out as an environmentally sustainable road material, renowned for its exceptional performance that significantly extends road surface lifespans while reducing maintenance costs. This study focuses on the preparation of PA using a single-component blending method that incorporates polyether polyol PTEMG (Poly-(tetra methylene ether glycol)) and isocyanate MDI (4,4′-diphenylmethane diisocyanate) as primary raw materials. Various analytical techniques, including Fluorescence Microscopy, Fourier-transform Infrared Spectroscopy (FTIR), Thermogravimetric analysis (TG), Differential Scanning Calorimetry (DSC), Viscosity Testing, Tensile Testing, and Bending Beam Rheometer (BBR), were employed to investigate PA's microstructure, modification mechanism, thermal properties, viscosity characteristics, curing properties, and low-temperature stability. A porous polyurethane-modified asphalt mixture, targeting a void content of 20%, was designed and compared to a high-viscosity modified asphalt mixture with the same void content in terms of performance. The results indicate a combination of chemical and physical processes in PA modification. Through TG and DSC experiments, it was ascertained that polyurethane-modified asphalt commences decomposition at 252 °C, exhibiting an exothermic peak within the temperature range of − 19.98–2.73 °C. The introduction of polyurethane substantially enhances the thermal performance and cryogenic stability of the asphalt binder. Viscosity tests and tensile experiments indicate that the curing reaction of polyurethane-modified asphalt is protracted and irreversible. Consequently, it is recommended to prepare polyurethane-modified asphalt mixtures employing a compaction temperature of 175 °C and a maximum resting time of 100 min. Additionally, specimens should rest at room temperature for at least 3 days. Comparatively, the porous asphalt incorporating polyurethane exhibits notable advantages over the high-viscosity modified asphalt mixture. It demonstrates superior high-temperature stability, excellent resistance to low-temperature cracking, reduced sensitivity to strains, prolonged fatigue life, and improved flexibility. However, its fatigue resistance and resistance to dynamic loads are slightly inferior. This study offers valuable insights into the use of polyurethane in porous asphalt mixtures, making it a promising option for sustainable road construction. • Three-dimensional structure is produced in polyurethane modified asphalt. • The performance of polyurethane-modified asphalt can be enhanced through the blending parameters and curing duration. • Polyurethane-modified asphalt surpasses high-viscosity modified asphalt in multiple performance aspects. [ABSTRACT FROM AUTHOR]

Direct injection modifiers revealed vast development potential because of their convenience utilization and no need for professional equipment. However, different characteristics of each direct injection modifier fluctuate significantly on the mixing process and road performance of their modified asphalt mixtures. The purpose of this paper is to evaluate the effectiveness of two novel asphalt rubber pellets (ARP) and asphalt desulfurized rubber pellets (ADRP) in improving the performance of asphalt mixtures. Firstly, this paper used orthogonal experimental design method to determine the priority order of the influencing factors on direct injection modifiers (ARP and ADRP), and further optimized the mixing technology of asphalt mixtures containing direct injection modifiers. Then, using base asphalt, commercial asphalt rubber (AR) and SBS (styrene-butadiene-styrene block copolymer) modified asphalt as control groups, the road performance of five asphalt mixtures was evaluated. Finally, the volatile organic compounds (VOCs) release characteristics of the asphalt mixtures were quantitatively analyzed. The results indicated that the priority order of factors affecting the ARP and ADRP is digestion time > dry mixing time > mixing temperature, and the optimal mixing process parameters are dry mixing for 90 s, mixing temperature of 180 °C, and digestion time of 90 min. Additionally, road performance of ADRP modified asphalt mixtures (ADRP-AM) is superior to that of ARP modified asphalt mixture (ARP-AM), which reaches or even exceeds the road performance of asphalt rubber mixtures (AR-AM) and SBS modified asphalt mixtures (SBS-AM) prepared by wet process. The five asphalt mixtures demonstrate the similar VOCs composition, and the total concentration of VOCs emissions is ARP-AM > AR-AM > ADRP-AM > B-AM > SBS-AM. P-/m-xylene, acetone, benzene, ethylbenzene and substances containing chlorine emerge high concentration for the VOCs composition of the five asphalt mixtures. This research can provide technical support for promoting the widespread application of direct injection asphalt rubber pellets. • Mixing technology of asphalt mixtures containing direct injection asphalt rubber pellets were optimized. • Road performance of asphalt mixtures containing direct injection asphalt rubber pellets were investigated. • VOCs of asphalt mixtures containing direct injection asphalt rubber pellets were evaluated. [ABSTRACT FROM AUTHOR]

Highlights • 6% APAO was the optimal dosage in asphalt binder and asphalt mixture performance perspective. • Asphalt mixture with 6% APAO had the best high temperature performance, moisture damage resistance. • Negligible tensile strength differences occur between asphalt mixture with 4% APAO and 6% APAO. Abstract In this paper, asphalt binder was blended with 0%, 4%, 6%, and 8% Amorphous poly alpha olefins (APAO) to prepare modified asphalt binders. Based on the penetration, ductility, softening point, and Dynamic Shear Rheometer (DSR) test, 6% APAO was the optimal dosage in asphalt binder performance perspective. The dense graded aggregate was mixed with APAO modified asphalt binder to prepare the APAO modified asphalt mixture. The volumetric parameters of the asphalt mixture with APAO modified asphalt binder was tested. The standard Marshall stability test, immersion Marshall test, Freeze-thaw splitting test, and Marshall stability of aged asphalt mixtures test were conducted on asphalt mixtures with APAO modified asphalt binder. Based on the Marshall stability test, immersion Marshall test, and Freeze-thaw splitting test, asphalt mixture with 6% APAO possessed the best high temperature performance, the highest moisture damage resistance, and the least splitting tensile strength loss after the freeze-thaw conditions. The tensile strength decreased after the addition of APAO. There was only negligible tensile strength difference between asphalt mixture with 4% APAO and 6% APAO. Based on the Marshall stability and retained Marshall stability ratio (RMSR) of asphalt mixtures after aging, the optimal content of APAO was 6%. Therefore, 6% APAO was the optimal content for both modified asphalt binder and APAO modified asphalt mixture. [ABSTRACT FROM AUTHOR]

To investigate the performance of asphalt mixture designed by the vertical vibration method, the vertical vibration design method (VTM design method) and Marshall design method were used to design the AC-16 (asphalt concrete with nominal maximum aggregate size = 16 mm) asphalt mixture. The physical properties, mechanical properties, road performance and fatigue property of the asphalt mixture designed by these two methods were examined. The results show that compared with that of the Marshall method, the optimal asphalt content of the asphalt mixture designed by the VTM method is decreased by 9.0%, and the density is increased by 1.8%; the mechanical properties, anti-rut ability and anti-crack ability are increased by at least 30%, 34% and 17%, respectively; and the water stability is also improved slightly. In addition, the fatigue life can be increased by at least 59%. The results also show that the Marshall stability, compression strength, splitting strength, tensile strength and shear strength of field drill cores designed by the VTM method are increased by at least 42%, 32%, 21%, 31% and 33%, respectively, compared with those of the Marshall method. Clearly, the performance of the asphalt mixture designed by the VTM method is better than that of the Marshall method, which could offer a better choice for asphalt mixture design. [ABSTRACT FROM AUTHOR]

• Warm-mixed agent can reduce viscosity and VOCs emission in LDHs/SBS modified asphalt. • The optimal content of LDHs for warm-mixed LDHs/SBS modified asphalt mixture is determined to be 3 wt%. • Warm-mixed LDHs/SBS modified asphalt mixture test road has good mechanical and anti-ultraviolet aging performance. MgAl-Layered double hydroxides (LDHs) is commonly applied to improve the anti-ultraviolet (UV) aging performance of SBS-modified asphalt concretes. However, LDHs elevates the mixing temperature of SBS-modified asphalt, resulting in more energy consumption and more volatile organic compounds (VOCs) emission. The surface-active warm-mixed agent (W-MA) can effectively reduce the viscosity of asphalt binder. This study explored the use of W-MA in LDHs/SBS-modified asphalt binder (LA) and LDHs/SBS-modified asphalt mixtures (LAM) to reduce the mixing temperature and VOCs emission. Firstly, the structural stability of LDHs and the effect of W-MA on viscosity reduction and VOCs emission in LA were studied. Then, the physical properties, UV aging resistance, and optimal LDHs content of warm-mixed LAM were examined. Finally, the performances of the test road applying warm-mixed LAM were investigated. The results demonstrated that the excellent structural stability of LDHs and the application of W-MA could effectively reduce the viscosity of LA and VOCs emission. Warm-mixed LAM exhibited excellent UV aging resistance and high-temperature performance. However, its low-temperature performance and moisture damage resistance performance were slightly lower than warm-mixed asphalt mixtures. The optimal LDHs content in warm-mixed LAM was found to be 3 wt%. The test road showed minor differences in road performance compared to that in the laboratory, and the test road has great anti-UV aging performance. [ABSTRACT FROM AUTHOR]

• The preparation and surface treatment methods for producing bamboo and corn straw biomass fibers were proposed. • The enhancement effects of proposed biomass fibers on the road performance of SMA mixtures were validated. • The micromorphology evaluation demonstrated the mechanism of biomass fiber reinforcement in SMA mixtures. With the sustainable development of infrastructure construction materials, the use of renewable biomass resources in asphalt mixtures could contribute to better sustainability. The bamboo fibers and corn straw fibers with lengths ranging from 1.5 to 12 mm were produced in the laboratory through the proposed crushing, steaming, and grinding processes. A surface treatment with the phenolic resin copolymer modifier was utilized to reconstruct the micro-surface of biomass fibers. The surface treatment effectively reduced the oil absorption multiplier and mass loss of proposed biomass fibers by about 0.6 and 2 %, respectively. The FI-IR absorption peak and change of micromorphology also validated the effective surface reconstructive. Afterward, the virgin asphalt (70#) mixtures and SBS-modified asphalt mixtures with/without biomass fibers were produced for road performance tests and fatigue resistance tests. The results showed that the proposed biomass fibers contributed to about 20 % to 30 % improvement in the high-temperature performance, while the low-temperature cracking resistance was also obviously increased. In addition, the moisture damage resistance and fatigue life were also improved after the addition of biomass fiber modifier, in which the residual stability and tensile strength ratio were increased by about 9 % and 6 % by comparing that with fibreless mixtures, respectively. By comparing the effect of different types and lengths of fiber modifiers, the long bamboo fiber with surface treatment represented the optimized strengthening efficiency. The enhancement mechanism of proposed biomass fiber modifiers was revealed through the microstructure observation. The feasibility of using proposed biomass fibers with surface treatment for producing high-performance SMA has been verified, which can be utilized in the field application for replacing the lignin fiber modifiers for achieving better sustainability. [ABSTRACT FROM AUTHOR]

• A novel de-icing fiber permeable mixture (DFPM) is prepared. • The water permeability, road performance and de-icing performance of DFPM were evaluated. • A long-term performance test process was designed to predict the de-icing longevity of DFPM. • DFPM with 0.3% fiber and 5% de-icing agent shows superiority in performance and cost. The complex and changeable service conditions require pavements with greater functional diversity and environmental adaptability. In this paper, the de-icing fiber permeable asphalt mixture (DFPM) that satisfied the multiple service requirements of rapid drainage and ice melting in various seasons was proposed. Various performance characterization tests were utilized to evaluate the permeability and de-icing properties and the pavement performance of the mixtures with different contents of de-icing agents and fibers. Meanwhile, the high temperature dynamic water scouring experiment was designed to predict the effective de-icing life. The results show that adding de-icing agents and fibers slightly affects the water permeability of the mixtures. The incorporation of de-icing agents is beneficial to the high temperature performance yet detrimental to the low temperature behavior and water stability, while the incorporation of fibers compensates for the negative effect; the de-icing performance of the mixture correlates positively with the amounts of de-icing agents and correlates negligibly with the fiber incorporation. DFPM with 0.3% fibers and 5% de-icing agent shows superiority in performance and cost and is recommended for practical applications. Therefore, building a composite functional asphalt pavement with excellent performance appears feasible while creating a pavement micro-ecology by applying de-icing fibers permeable asphalt mixtures. [ABSTRACT FROM AUTHOR]

• A robust PE plastic concrete was prepared by adding low-density polyethylene (LDPE) as a binder to the aggregates. • The preparation parameters of LDPE PC were determined by orthogonal experiments, and a design method of LDPE PC was proposed. • The evaluation results of the road performances of LDPE PC showed that LDPE PC has excellent high temperature performance, low temperature performance, and anti-scattering performance. This paper presents an innovative method of polyethylene plastic concrete (PC) to enhance the recycling rate of waste polyethylene. Based on experimental results, low-density polyethylene (LDPE) was selected as the binder, and a suitable gradation for PC was recommended. LDPE PC was mixed at 200 °C for 210 s and compacted 50 times on both sides. The workability was improved by adding a flow agent, with a 9% content determined through water stability evaluation indexes. Comprehensive volume and performance evaluations established an optimum binder-stone ratio of 5.7%. LDPE PC exhibited excellent high temperature, low temperature, and anti-scattering performance, making it promising for road applications. [ABSTRACT FROM AUTHOR]

• The use of graphene and carbon fiber as conductive phase materials for the preparation of graphene-conductive asphalt-recycled permeable concrete. • Determined the optimal conductive filler ratio and achieved a resistivity of only 3.2 Ω·m. • The effect of the required snow melting thickness and snow melting time on the efficiency of pervious asphalt slabs for snow melting are studied. Conductive-asphalt-recycled pervious concrete alleviates the urban "heat island effect" and "rain island effect" to realize the resourceful and efficient use of waste concrete and also reduces the probability of urban snow and ice disasters to ensure the safety of winter operation of asphalt pavements in cold areas. This study presents a theoretical and technical basis for ensuring the winter operational safety of asphalt pavements in cold regions. First, we compound graphene and carbon fiber as conductive phase materials and prepare graphene-conductive asphalt-recycled permeable concrete using recycled coarse aggregates with straight top and bottom holes. Then, we analyzed the electrical conductivity, road performance, and electrothermal performance of the specimens prepared using different recycled coarse aggregate substitution rates under different snowfall levels to determine their snow melting efficiency and verify their application in cold regions. The results indicate that the quality of the recycled aggregates is high, the optimal conductive filler ratio is 0.3% polyacrylonitrile-based carbon fiber and 1.5% graphene by mass of asphalt, and the resistivity of the specimens is only 3.2 Ω·m. Moreover, the conductivity and road performance of the graphene-conductive asphalt-recycled concrete decreases with an increase in the replacement rate of the recycled coarse aggregate, and the artificially prefabricated upper and lower through holes affect the conductivity of the specimens to a certain extent. Further, the graphene-conductive asphalt-recycled pervious concrete shows excellent snow melting potential, and as the required snow melting thickness and snow melting time increase, the effect of pervious asphalt slabs for snow melting efficiency becomes more significant. Moreover, when the replacement rate of the recycled concrete aggregate is within the range of 0–50%, it can be completed in 2–3 h under different snowfall levels of snow melting requirements. [ABSTRACT FROM AUTHOR]

Phosphate type single alkyl oxygen base titanates TM-P was used to modify the surface of phosphorus slag powder in this paper. The surface characteristics and modification mechanism of phosphorus slag particles were characterized by using Scanning Electronic Microscopy (SEM). The effects and mechanism of the surface modified phosphorus slag powder to the asphalt and asphalt mixtures were analyzed by Fourier Transform Infrared Spectroscopy (FTIR), dynamic shear rheological test (DSR), Marshall test, rutting test and freeze-thaw splitting test. The results show that phosphorus slag powder modified by TM-P (10% by weight of the powder) enhance the compatibility with asphalt, resulting in the increase of anti-aging, rutting resistance and water damage resistance of asphalt mixture. [ABSTRACT FROM AUTHOR]

This study aims at investigating the possibility of using basalt, limestone and andesite aggregates combinations in asphalt treated base mixture. Rapid developing of asphalt pavement construction results in the lack of high quality aggregates and environmental damage. Using the composite aggregates in asphalt mixtures is an effective way to solve problems of aggregate shortage and minimize the environmental depredation. Two types of composition methods, Coarse-Fine (C-F) composition method and Coarse-Coarse (C-C) composition method, were proposed and studied. Effective density was used in the mixture design to improve the accuracy on using composite aggregate. Research results illustrate that composite aggregate will change the volumetric properties of composite asphalt mixtures. The incorporation of alkaline coarse aggregates or surface roughness coarse aggregates on the aggregate can improve the mechanical properties of asphalt treated base. Asphalt mixture with composite of basalt and limestone aggregates can significantly enhance the moisture resistance property. Changing the types of coarse aggregates will result in more variables than changing the fine aggregates types. [ABSTRACT FROM AUTHOR]

• Comprehensive performance of Polyurethane Porous Elastic Mixture (PUPEM) is studied. • The rubber particle content has an important impact on the performance of PUPEM. • A rubber content of 10% and PU-Ⅰ with larger isocyanate index are recommended. • The PUPEM has the potential to balance road performance and noise reduction. Poroelastic road surface (PERS)has high rubber particle content and air void, and its noise reduction performance is excellent. However, the performance of Polyurethane Porous Elastic Mixture (PUPEM) prepared with different contents of rubber particles and different types of polyurethane (PU) are rarely studied. This study aims to evaluate the comprehensive and functional performance of PUPEM and to analyze the influence of rubber particle content and PU type on PUPEM. PUPEM was prepared using different types of PU and different rubber particle content. The high-temperature performance, low-temperature bending performance, water stability performance, and skid resistance performance of PUPEM were evaluated by rutting test, low-temperature bending test, freeze–thaw splitting test, immersion Cantabro loss test, pendulum friction coefficient tester and sand patch method. The effects of air void content, rubber particle content, and thickness on the noise reduction performance of PUPEM were also studied by impedance tube test and dynamic modulus test. The results indicate that the PUPEM has excellent high-temperature performance, favorable low-temperature bending performance and skid resistance, and its water stability can meet the specification requirements. PUPEM also has favorable sound absorption and noise reduction performance through voids and noise reduction performance through elastic damping. In addition, the maximum sound absorption coefficient of PUPEM corresponds to a frequency that is influenced by the thickness. In order to balance the road performance and noise reduction of PUPEM mixture, it is recommended that the rubber particle content is 10%, and the polyurethane PU-Ⅰ with larger isocyanate index is used. [ABSTRACT FROM AUTHOR]

• Using aeolian sand to replace 100% of the fine aggregate in the semirigid base of asphalt pavements, it was obtained that the road performance at 4% cement content with 50% and 58% of aeolian sand meet the design requirements for any level of highway and primary road. • Cement and fly ash stabilised aeolian sand gravel has good resistance to sulfate erosion and can mitigate semi-rigid subgrade damage problems. • The microscopic mechanism of cement and fly ash stabilized aeolian sand gravel under the dry-wet cycle of Na 2 SO 4 sulfate solution. To alleviate the scarcity of road construction materials in desert areas, the feasibility of 100% replacement of fine aggregates by aeolian sand for semirigid base pavement was studied. First, complete the design of the proportion of cement, fly ash, aeolian sand and gravel was completed by orthogonal testing. Second, based on mechanical property tests, compressive strength and splitting strength of each mix proportion were investigated at the maintenance ages of 7 d and 28 d. The resistance to sulfate erosion and water stability of each mix proportion were investigated at different ages with durability tests. Moreover, the strength development and deterioration mechanism of aeolian sand mixtures were analysed by SEM and EDS test systems. The results show that the increasein aeolian sand content significantly degrades the strength of the road performance of cement and fly ash stabilized aeolian sand gravel base; the 7 d unconfined compressive strength was 2.8 MPa, and splitting strength was 0.61 MPa when the aeolian sand content was 66%. The erosion products and hydration products of the binding material during the dry and wet cycles of the specimens under different ages filled the voids between the aggregates which improved the structural density, increasing the water stability coefficient and sulfate erosion resistance coefficient more than 95%. The complete replacement of fine aggregate by aeolian sand for semi-rigid type bases meets the design requirements of highway roadbases, which shows that the replacement of fine aggregate by 100% aeolian sand for a semirigid base was feasible. [ABSTRACT FROM AUTHOR]

• Self-adhesive basalt fiber geotextiles extend the service life of asphalt pavements. • The self-adhesive layer improves the interlayer adhesion of the pavement structure. • Basalt fiber geotextiles improve the performance of asphalt pavements. • Self-adhesive geotextiles suppress the propagation of cracks in the base layer. Achieving sustained asphalt pavements can minimize the structural damage brought on by minor pavement cracks, which will reduce the high repair and maintenance costs resulting from pavement distress. This study introduces a new composite geomaterial, self-adhesive basalt fiber geotextiles (SBFG) prepared by hot-melt lamination of basalt fiber cloth and modified asphalt, intended for the deterrence and control of reflection cracks in asphalt pavements. In this study, the self-adhesive geotextile was placed between the cement-stabilized macadam base and AC-20 surface layer to prepare composite samples, and the road performance was evaluated by a three-point bending test, Overlay Tester, dynamic shear rheology test, and the crack expansion time under different parameters of SBFG was simulated by ABAQUS finite element to predict the whole life cycle of the pavement structure. The results indicate that the fracture energy of the SBFG sample is the largest among all samples, and the structural design of fiber reinforcement disperses the concentrated stress at the crack tip, increases the stress area, and prolongs the time of crack expansion from the subgrade to the surface layer; Smooth and stable load loss curve of the sample in the reflection crack test, with slow crack expansion. This new geomaterial has an excellent rutting factor and maintains good resistance to permanent deformation at high temperatures; In the finite element prediction of fatigue cracking life of asphalt pavement, the structural life of the pavement with the addition of SBFG was improved by 78.3% compared to the control group. The application of basalt fibers in geosynthetics provides a new idea for achieving prolonged asphalt pavements. [ABSTRACT FROM AUTHOR]

• A cold patching asphalt liquid is developed with high performance and easy storage. • Effect of asphalt components on its performance is statistically analyzed. • The diesel plays a key role in properties of cold patching asphalt liquid. The cold patching asphalt liquid (CPAL) is an environment-friendly paving material, which is more preferable in pavement construction and has lower energy consumption than the hot mix asphalt. However, the CPAL is mainly applied in the quick repair of potholes because of the limitation in its cost and storage stability. This study primarily investigates the effect of the compositions and contents of CPAL on its road performance through the multivariate analysis to develop a low-cost and storable CPAL. In this study, the CPAL was synthesized by base asphalt, diesel, diethylene glycol (DG), oleic acid (OA), and coconut oil acid diethanolamine (COAD). Orthogonal experiments with four factors and four levels were performed to optimize the mechanical properties of CPAL. The microstructure and characteristic functional groups of different CPAL schemes were analyzed to further understand the influence of different components of CPAL on its pavement performance. Results show that the proposed multivariate evaluation method in this study can accurately evaluate the significant relationships between different functional components and properties of CPAL. Furthermore, the dosage of diesel should be strictly controlled in the productions considering that only the t value of diesel passes the inspection. The optimal design scheme of CPAL in this study is 20% diesel, 0.6% DG, 6% OA, and 6% COAD, and its mixture has high adhesion, strength, and good storage stability in pavement engineering. The multivariate evaluation method is also conducive for scientifically developing a green and high-performance road material. [ABSTRACT FROM AUTHOR]

• Comparison of the property of three types of deformation-adapted binders. • Propose a mixture design method for deformation-adapted mixtures. • Evaluation of three deformation-adapted mixtures' road and recovery performance. In this study, three deformation-adapted binders (rubber asphalt [RA], modified asphalt [MA], and polyurethane [PU]) and their mixtures were selected as the research objects to determine their performances under the same evaluation indices. First, the high-temperature, low-temperature, compressive, and tensile properties of three deformation-adapted binders were examined by performing anti-flow, low-temperature flexibility, compression permanent deformation, and tensile tests, respectively. Second, the road and recovery performance of the deformation-adapted mixtures were investigated through rutting, Marshall stability, low-temperature trabecular bending, tensile and Overlay Tester tests. From the extracted outcomes, it was demonstrated that, among the three deformation-adapted binders, PU exhibited superior high-temperature, low-temperature, compression, and tensile characteristics, followed by MA and RA. Furthermore, the deformation-adapted mixture of PU displayed the best high-temperature, low-temperature, water stability, and fatigue crack resistance performance. The deformation-adapted mixtures of RA and MA also had excellent performance in terms of tensile, compression, and strength recovery characteristics. Notably, the deformation-adapted mixtures of PU only exhibited excellent tensile and compression recovery properties, while the strength recovery properties were not good. [ABSTRACT FROM AUTHOR]

• Developed an environmentally friendly CPM for pothole repair on asphalt pavements. • EUPM showed excellent performance in high temperature resistance, low temperature deformation and water stability. • EUPM with ER binder as interfacial agent had better repair effect than SBS modified bitumen. Currently, cold patching materials (CPMs) have become a preferred choice for pothole repair on asphalt pavements in cold and wet weather, to timely restore pavement serviceability and improve traffic safety. However, the survival time of conventional asphalt-based CPMs is not satisfactory, and volatile and toxic components in emulsified or dissolved asphalt are more easily leached to cause water and air pollution, while advanced CPM that can achieve a longer repair longevity may be more cost-effective and environmentally friendly in the long term. The main objective of this paper is to develop a pollution-free, economical and high-performance CPMs to repair asphalt pavement potholes more effectively and sustainably. Specifically, a low viscosity, high toughness and low temperature curing epoxy resin (ER) binder was designed and the unsaturated polyester was selected adaptively. On this basis, the mix proportion of epoxy/unsaturated polyester-based mixture was designed and its performance of the mixture during construction and service was investigated. The results show that epoxy/unsaturated polyester mixture (EUPM) with the optimal material composition possessed excellent high temperature rutting resistance, low temperature deformation performance and water stability. The cold patching materials using EUPM and epoxy resin as the interface agent had excellent repair effect and adapted to a certain humid environment. The study proved the feasibility and advantages for the investigation utilizing EUPM as cold patching materials in asphalt pavement maintenance. [ABSTRACT FROM AUTHOR]

• PCTIA can effectively slow down the cooling process of asphalt mixture during construction. • The road performance of modified asphalt mixture with 2.5% PCTIA content is good. • PCTIA had the most application value in low temperature and low wind speed environment. Highway construction strategies impact the early damage of asphalt pavement and its sustainability. The pavement quality is directly influenced by the temperature of the asphalt mixture during paving and rolling, but delaying the cooling of the mixture at this stage has rarely been investigated. An asphalt mixture modified with a phase-change thermal-insulation agent (PCTIA) was prepared potentially improve the temperature of the asphalt mixture during construction. The high-temperature, low-temperature, and water-stability performance of asphalt mixtures with different PCTIA contents were analysed. The temperature regulation test was carried out, and the temperature field model of the asphalt pavement paving process was established. Based on the laboratory test and FEM models, the influence of different construction environmental conditions on the thermal-insulation performance of PCTIA and its thermal-insulation mechanism were analysed by using the distribution of temperature, average temperature, and equivalent temperature. The thermal-insulation effect of PCTIA was quantified by latent heat accumulated temperature value (LHATV). Results show that PCTIA improves the high and low-temperature performance of asphalt mixture, and has little effect on water stability. The best overall road performance is achieved at 2.5% PCTIA content. PCTIA can significantly reduce the cooling rate of asphalt mixture, and the distribution of temperature difference and time difference is obviously different in different positions of loose asphalt mixture layer and different external environments. Latent heat accumulated temperature value (LHATV) can characterize the phase-change insulation effect of PCTIA well. The wind speed increases and air temperature-bottom temperature decreases reduced LHATV indicating that too rapid cooling of asphalt mixture would weaken the thermal-insulation performance of PCTIA. Both average temperature and equivalent temperature can reflect the thermal-insulation effect of PCTIA, where the average temperature can be used to analyse the specific phase-change process of PCTIA in asphalt mixture and then analyse the insulation mechanism of PCTIA. Combining average temperature and equivalent temperature, PCTIA had the most application value in low temperature and low wind speed environments. This study aims to explore the effective method of delaying the cooling of high-temperature asphalt mixture from the perspective of phase-change energy storage and explain its mechanism. [ABSTRACT FROM AUTHOR]

[Display omitted] • This paper develops a new epoxy resin binder with high bonding strength, good durability, and easy operation and excellent low-temperature toughness. • A mix design method of macroporous(18%–26%) epoxy resin mixture is proposed. • The design method of the mixture ratio of macroporous epoxy resin mixture can directly calculate the target mixture ratio according to the porosity requirement, and the key performance and road performance of the prepared mixture is better than those of porous asphalt mixture. • This mix proportion method effectively avoids the randomness of determining the gradation composition of the porous mixture and the amount of binder and dramatically reduces the test time and cost in the process of mix proportion design. At the problems of insufficient bonding force and low overall strength of asphalt as the binder in the porous mixture, this paper developed a new epoxy resin binder with high bonding strength, good durability, and easy operation and excellent low-temperature toughness, prepares macroporous epoxy resin mixture, put forward the corresponding mix design method, and studied its performance. The mass ratio of the component of the new epoxy resin binder is modified epoxy resin:diluent:curing agent:accelerator = 120:65:45:3. The mixture ratio design method of macroporous (18 %∼26 %) epoxy resin mixture can directly calculate the target mixture ratio according to the porosity requirement, and the prepared mixture not only shows good mechanical strength and deformation coordination ability.. When the void ratio is greater than 22 %, the permeability of the mixture is significantly improved, and the anti-scattering performance still meets the specification requirements. The dynamic stability times of macroporous epoxy resin mixture at 60 °C are 18000 ∼ 157500 times/mm; the ratio of 15 °C splitting strength to-10 °C splitting strength is between 80 % and 100 %, shows good toughness at low temperature and is insensitive to temperature; the immersion Marshall stability is between 85.97 % and 92.51 %, and the road performance is better than that of porous asphalt mixture. This mix proportion method effectively avoids the randomness of determining the gradation composition of the macroporous mixture and the content of binder and dramatically reduces the test time and cost in the process of mix proportion design. [ABSTRACT FROM AUTHOR]

• An intelligent control system is developed for asphalt mixture paving. • A temperature cloud map is drawn for asphalt mixture paving. • A comprehensive evaluation of temperature segregation is presented for asphalt mixture paving. • The effect of paving temperature segregation on the performance of asphalt pavement is analyzed. The index of temperature segregation in asphalt mixture paving is one of the key indicators of quality control of asphalt pavement construction. Intelligent control techniques have also been recently used as a novel technology in controlling the temperature segregation of asphalt mixture for paving. Hence, the present study aims at developing an intelligent control system of asphalt mixture paving. Accordingly, to monitor and visualize the quality of the real-time paving, a temperature cloud was mapped for the asphalt mixture paving. Furthermore, a comprehensive evaluation method of paving temperature segregation was developed based on two indices, i.e., temperature segregation index and low-temperature area index. In addition, the accuracy of the developed system in controlling the paving temperature, thickness and segregation degree was practically confirmed. Moreover, the influence of paving temperature segregation on the asphalt pavement performance (compactness and smoothness) were practically explored. The obtained results corroborated the real-time effectiveness of the smart system in controlling the entire process of asphalt mixture paving. Also, the cloud map enabled the visual displaying of the asphalt pavement temperature segregation in real-time. Consequently, the quality of asphalt pavement construction was improved. Hence, the proposed evaluation metric was capable of accurately assess and predict the state and performance of the asphalt mixture paving temperature segregation. [ABSTRACT FROM AUTHOR]

[Display omitted] • The micro modification mechanism of bio-asphalt/TLA modified asphalt are analyzed. • Bio-asphalt improves the low temperature performance of TLA modified asphalt. • The relationship between indexes of modified asphalt and mixture is established. Trinidad Lake Asphalt (TLA) modified asphalt has excellent high temperature performance, but its low temperature performance is poor, which limits its engineering application. But bio-asphalt presents relatively excellent low temperature performance. In this paper, TLA and Bio-asphalt were used as additives to prepare composite modified asphalt with excellent properties both at high and low temperatures. The micro modification mechanism of asphalt was studied by Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The macro mechanical behavior of asphalt binder was explored through routine physical property test and rheological property test. Finally, the mechanical properties of asphalt mixture were studied through the routine test of asphalt mixture, and the relationship between the macro and micro indexes of asphalt binder and the high and low temperature performance of asphalt mixture was established through grey correlation. The test shows that the mixing mode of TLA, bio-asphalt and base asphalt is physical blending. Modifiers affect the macro mechanical properties of asphalt by changing the distribution of asphalt components, the size of molecular weight, the interaction strength and arrangement of molecules. TLA improves the performance of asphalt binder at high temperature, but weakens the low-temperature performance. The low temperature performance of TLA modified asphalt was significantly improved by adding bio-asphalt at the cost of slightly reducing the high temperature performance. When the content of bio-asphalt is 9%–12%, the bio-asphalt/TLA modified asphalt and its mixture have better performance on high and low temperature properties than that of base asphalt. The micro indexes such as aromatic ring index and weight average molecular weight are good indicators of the high temperature performance of asphalt mixture. Creep rate (m), equivalent brittle point (T1.2) and stiffness modulus (S) can reflect the low-temperature performance of asphalt mixture. [ABSTRACT FROM AUTHOR]

• This synthesis reviewed the current research progress of ICLR in asphalt mixture. • ICLR can be developed as fine aggregate to produce asphalt mixture and improve its performances. • The current research focuses on the conventional performance of ICIR asphalt mixture. • It is necessary to control and recommend reasonable substitution amount and particle size. • It is essential to study mechanical and fatigue properties of ICLR ICIR asphalt mixture. Indirect coal liquefaction residue (ICLR) is a by-product of coal-to-liquid technology that cannot be avoided in the process of converting raw coal to liquid fuel, causing potential threats to the environment and physical health. In this paper, the global research status of ICLR in asphalt pavement is summarized to promote the further application of ICLR in this field. Firstly, the properties of DCLR are introduced, including physical and chemical properties. Secondly, the current status of comprehensive utilization of ICLR and the research progress of its usage in asphalt pavement is summarized, including the particle size, amount of addition, and its effect on the performance of asphalt mortar and mixture. Finally, the article concludes that the future studies of ICLR should focus on controlling the added particle size and content, clarifying the effect of ICLR's particle size and amount on the mixture's performance, and proposing the rational use index of ICLR. It is necessary to study the working performance and mechanical behavior of ICLR asphalt mixture, especially the research on modulus and fatigue performance needs to be further deepened. [ABSTRACT FROM AUTHOR]

[Display omitted] • The difference of de-icing effect of different types of eco-friendly de-icing asphalt mixture(EDAM) is analyzed. • The pavement performance of de-icing asphalt mixtures in the simulated pavement service conditions is studied. • The influence of the adhesiveness on the road performance and de-icing effect is discussed. To address the icing problem on the road, this paper, based on the salt accumulation and de-icing technology, used binary acetate as the de-icing material to prepare an eco-friendly de-icing filler(EDF), and EDF replaced the mineral fillers into four types of asphalt mixtures of matrix, SBS, high viscosity and rubber to prepare four different eco-friendly de-icing asphalt mixtures (EDAM). The compatibility and adhesiveness of four types of asphalt with the EDF were studied by scanning electron microscope test and pull-out test. By setting the freeze–thaw cycle conditions, the performance changes of water stability and low-temperature crack resistance of the four types of EDAM were studied. The pavement-ice interface adhesion reduction test and de-icing salt precipitation test were used to analyze the differences in the de-icing effect of four types of EDAM. The test results show that the adhesiveness between four types of asphalt mastic and EDF are different, which has an important impact on the road performance; In the freeze–thaw cycle environment, the addition of EDF damages the water stability and low temperature flexibility of the asphalt mixture, but enhances the anti-rutting performance after washout. In the de-icing effect, the four types of EDMA show various performances. This paper shows that the road performance and de-icing performance of EDMA with high viscosity are the best, which provides a new method for deicing asphalt pavement. [ABSTRACT FROM AUTHOR]

[Display omitted] • PU's raw materials, synthesis process, structure, and applications were described. • The isocyanate can react with asphalt's active hydrogen groups. • One-shot process, prepolymer process, semi-prepolymer process, and direct injection process for preparing PUMA were summarized. • The road performance of PUMA asphalt was thoroughly analyzed. During its service life, ordinary asphalt pavement frequently develops rutting, cracking, spalling, and other ailments. Polyurethanes (PUs) are frequently utilized in the construction, transportation, and furniture industries as soft and stiff foam, elastomers, and adhesives. Over the past five years, research on the use of PU and its raw materials as modifiers for road asphalt has increased annually. Thus, this paper primarily reviews the following topics: 1) First, the necessity of modified asphalt, the limitations of SBS-modified asphalt and Rubber powder modified asphalt, and the benefits of polyurethane-modified asphalt (PUMA) are discussed; 2) Second, the relevant background of PU, including common raw materials, synthesis methods, structures, and primary application scenarios, is presented. 3) Bitumen's chemical composition and typical functional groups are summarized. Based on this, the mechanism of PUMA was analyzed from four different perspectives: chemical reaction, Fourier Transform Infrared Spectroscopy (FTIR), change in the proportion of SARA, and Fluorescence Microscopy (FM). 4) Four processes of preparing PUMA are reviewed: one-shot process, prepolymer process, semi-prepolymer process, and direct injection process. The most prevalent process is the prepolymer process; 5) The road performance of PUMA with different preparation processes was systematically analyzed. In general, PU can significantly increase the high-temperature performance, water stability, fatigue resistance, anti-aging qualities, and adhesion of asphalt, but their low-temperature performance and temperature sensitivity remain debatable; 6) Five research directions for PU as an asphalt modifier for roads are summarized: PU modified emulsified asphalt, Bio-based polyol PUMA, PU and other materials composite modified asphalt, waste PU modified asphalt, and PU foam asphalt; 7) Finally, the existing problems and development trend of PUMA are reviewed. [ABSTRACT FROM AUTHOR]

• High heat source (HHS) steel slag was screened by steel slag classification. • Microwave heating uniformity of SSAM with HHS was significantly improved. • Microwave cycles can negatively affect the durability of SSAM. • Microwave heating can reduce micro voids in SSAM. Steel slag (SS) has good microwave absorption and microwave heating potential. Firstly, SS was classified by the difference of microwave capacity, and high heat source (HHS) steel slag was selected to partially replace limestone to prepare steel slag asphalt mixture (SSAM) in this work. The morphology and elements of SS were analyzed by microcosmic tests. Then the surface temperature and thermal transfer process of SSAM were studied. In addition, the road performance of SSAM under different microwave cycles was evaluated. Finally, the influence of microwave heating on the air voids structures of SSAM was analyzed by X-ray computed tomography (CT). The results show that the surface temperature of SSAM prepared by HHS steel slag is not significantly reduced, and the uniformity of microwave heating is greatly improved. The metallic elements in SS are the reasons for enhancing the microwave absorption performance of SSAM. After microwave cycling, the road performance of the mixture continues to decline; CT scan results show that microwave heating can reduce the micro voids in SSAM but increase the ratio of large voids and extra-large voids, which causes the decrease of durability. Overall, this work contributes to improving the durability and sustainability of asphalt pavements under microwave irradiation. [ABSTRACT FROM AUTHOR]

Highlights: [•] We analyze the mineral composition of RCA and observe surface morphology by SEM. [•] We select the best activator out of three used to activate RCA. [•] We prove that substituting natural aggregate by RCA in ATB is feasible. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effect of TPU/APAO on the asphalt mixture performance was explored. • APAO could enhance the rutting resistance of TPU modified asphalt mixture. • TPU has positive impact on the cracking resistance of asphalt mixture. • 2 % TPU + 6 % APAO modified asphalt mixture had superior road performance. The using of waste polymer modified asphalt binder in pavement construction is cost effective and beneficial to the environment. In this paper, the modified asphalt binders are prepared by adding thermoplastic polyurethane (TPU, 0 %, 2 %, 4 %, 6 %, by weight of asphalt binder) and amorphous poly alpha olefins (APAO, 0 %, 2 %, 4 %, 6 %). The conventional physical, rotational viscosity and dynamic shear rheometer (DSR) tests were conducted on the modified binders and the results indicated that the addition of APAO could improve the rutting resistance the TPU modified asphalt binder, and the modified asphalt binder with 2 % TPU and 6 % APAO showed the best rutting resistance among the studied binders. To assess the effect of APAO dosage on the performance of TPU modified asphalt mixture, mechanical performance tests including Marshall stability, dynamic stability, indirect tensile, immersion Marshall, freeze–thaw splitting and long-term aging tests were carried out on asphalt mixtures with various TPU/APAO content combinations. The test results proved that 2 % TPU + 6 % APAO modified asphalt mixture showed better resistance to rutting and moisture damage, the superior long-term aging damage resistance, and the excellent anti-freeze–thaw damage ability, when compared to the unmodified asphalt mixture. According to the indirect tensile test results at −10 °C, despite the indirect tensile strength (ITS) value of 2 % TPU modified asphalt mixture decreased after APAO added, the ITS value of asphalt mixture modified with 2 % TPU and 6 % APAO was still improved 5.8 % than base asphalt mixture. Based on the comprehensive analysis of the data, 2 % TPU + 6 % APAO modified asphalt mixture has superior road performance, and the performance characteristic of TPU/APAO compound modified asphalt mixture indicated that it could be applied for warmer regions. [ABSTRACT FROM AUTHOR]

• PP fiber and nano-TiO 2 modification improves the road performances of PMM. • The optimum ratio of PP fiber and nano-TiO 2 in PMM has been determined. • The PMM showed excellent photocatalytic exhaust degradation capacity. • The PMM significantly reduces the energy consumption and greenhouse gas emissions. To purify severe air pollution in traffic-intensive urban areas and tunnels, an innovative type of photocatalytic micro-surfacing mixture (PMM) was designed, which was enhanced by polypropylene (PP) fiber and nano-TiO 2. In this work, the road performance of sixteen PMMs with the different contents of PP and nano-TiO 2 were evaluated by wet-track abrasion test, wheel rutting deformation test and low-temperature splitting test. The vehicle exhaust (VE) gas degradation capacity of sixteen PMMs was characterized under ultraviolet (UV) light and visible light conditions. The life cycle assessment (LCA) methodology was applied to evaluate the environmental impact of PMM. The results showed that the road performances of PMM were improved with the increase of the PP fibers amount. The VE gas degradation capacity was significantly enhanced with the increase of nano-TiO 2 amount. PMM with 0.2 wt% PP fibers and 60 wt% replacement of mineral filler with nano-TiO 2 was a viable alternative to improve photocatalytic degradation of VE in pavement engineering. In addition, the modified micro-surfacing mixture facilitates a significant reduction in energy consumption and greenhouse gas emissions. [ABSTRACT FROM AUTHOR]