A new testing procedure to estimate the low-temperature stiffness of the reclaimed asphalt pavement （RAP） binder was developed. In the testing procedure, the SuperpaveTM Bending Beam Rheometer （BBR） with special m...A new testing procedure to estimate the low-temperature stiffness of the reclaimed asphalt pavement （RAP） binder was developed. In the testing procedure, the SuperpaveTM Bending Beam Rheometer （BBR） with special modifications and binder blending charts by Asphalt Institute were utilized. Modifications involved the development of a new kind of sample mold and different testing parameters were made to BBR testing procedure to capture the theological properties of bitumen mortars produced by mixing fresh binder with fine RAP materials or RAP aggregate. The stiffness relationship between binder and bitumen mortar was established based on the BBR test results. The blended binder stiffness in bitumen RAP mortar was estimated from the RAP mortar stiffness based on the binder-mortar relationship. And finally, the RAP binder stiffness was estimated from the blended binder and fresh binder stiffness based on the blending charts by Asphalt Institute. The results indicate that the new procedure can capture the rheological properties of bitumen mortar and can be used to estimate the low temperature stiffness of RAP binder without binder extraction and/or any chemical treatments.展开更多
Reclaimed asphalt pavement(RAP)has significant recycling value because it contains nonrenewable resources including asphalt and aggregate.However,thus far,only a small part of RAP materials can be used in the con-stru...Reclaimed asphalt pavement(RAP)has significant recycling value because it contains nonrenewable resources including asphalt and aggregate.However,thus far,only a small part of RAP materials can be used in the con-struction of recycled asphalt pavement,and the usage is regarded as a low-value utilization in the underlying layers.One of the most important reasons for this shortcoming is the problem of false particle size and pseudo gradation of RAP materials.Therefore,identifying suitable asphalt-aggregate separation technology is essential for improving the utilization of RAP materials in recycled asphalt mixture and enhancing the construction quality of recycled asphalt pavement.To address this,the paper performed a systematic review of asphalt-aggregate separation technologies for processing RAP materials and their prospects.Firstly,based on the composition of the asphalt mixture and the characteristics of RAP materials after aging,the key RAP separation technologies were proposed.Then,the concept,principle,and implementation methods of physical,chemical,and biological sep-aration methods of RAP materials were comprehensively analyzed.Moreover,the advantages and disadvantages of various separation technologies were discussed by comparing them with the related technologies in the petrochemical industry.The application prospects of various asphalt-aggregate separation methods for RAP materials can provide a reference for upgrading and expanding solid waste recycling technology for asphalt pavement.展开更多
The utilization of reclaimed asphalt pavement(RAP)in asphalt mixtures has gained momentum in recent years,yet concerns persist regarding the long-term performance and binder properties of high RAP content mixtures.To ...The utilization of reclaimed asphalt pavement(RAP)in asphalt mixtures has gained momentum in recent years,yet concerns persist regarding the long-term performance and binder properties of high RAP content mixtures.To overcome these challenges,rejuvenators have emerged as a promising solution to enhance the properties of aged asphalt binders and improve the overall performance of asphalt mixtures.This paper provides a comprehensive state-of-the-art review of rejuvenator technology and its potential to enhance the performance and sustainability of asphalt pavements.Rejuvenators are additives used to restore the properties of aged asphalt binders,particularly when incorporating high percentages of RAP.The performance of these additives varies based on their origin,and different methods can be used to analyze the rejuvenation process.Since proper specifications for rejuvenators are not available,blending charts are used to determine the optimum dosage of rejuvenators.However,proper blending must be achieved to maximize results and reduce the effect of black rock.Laboratory tests and some field performance studies on rejuvenated aged asphalt binders and RAP mixtures have shown improved or similar performance compared to virgin materials.Additionally,the use of rejuvenators has been observed to reduce construction costs,suggesting that this is a cost-effective technology for asphalt pavements.While rejuvenators show promise in improving the performance of pavements with recycled materials,challenges remain regarding optimization,long-term durability,and environmental effects.This review paper also identifies key areas for future research,including life-cycle cost analyses,comprehensive environmental impact assessments,and long-term field performance monitoring.展开更多
The performance of roller compacted concrete(RCC)was greatly influenced by variations in material proportion,optimum moisture content,density of mixes and methodology adopted making it different from conventional conc...The performance of roller compacted concrete(RCC)was greatly influenced by variations in material proportion,optimum moisture content,density of mixes and methodology adopted making it different from conventional concrete mixes.Even though RCC has gained popularity,the complex phenomenon involved in developing the RCC mixes limits it from large-scale applications.In this study,reclaimed asphalt pavement(RAP)incorporated roller-compacted geopolymer concrete(RGC)mixes were developed herein with different compaction techniques such as vibratory hammer(VH),modified proctor(MP),vibration table(VT)and compression machine(CM)are studied and compared with control mixes of natural aggregates.Initially,the effect of alkali solutions such as sodium hydroxide(SH)and sodium silicate(SS)on the physical properties.During,the second phase mechanical properties such as dry density,compressive,flexural and split-tensile strength,modulus of elasticity and microstructure properties will be investigated.The test results revealed that compaction efforts were greatly influenced by the alkali solution.Furthermore,the poor bond characteristics between RAP and the binder matrix had a significant effect on strength properties.Also,the various compaction techniques affected the mechanical properties of mixes developed herein.In Comparison with various compaction efforts,VH and MP produced comparable results,whereas the VT method underestimated and overestimated the various strength properties.Although,the CM method reports comparable results but difficult to maintain consistency in strength aspects.Therefore,optimization of various parameters influencing the concrete properties needs to be achieved for field density.展开更多
The property of reclaimed asphalt pavement（RAP） mixture will be affected mainly by composition of old asphalt/soil and cement content in CIR system. We studied the relationship between A/S and cementitious materials...The property of reclaimed asphalt pavement（RAP） mixture will be affected mainly by composition of old asphalt/soil and cement content in CIR system. We studied the relationship between A/S and cementitious materials. It showed that if there was no soil in RAP, the unconfined compressive strength was only from 0.18 MPa to 1.07 MPa even if adding cement was from 2% to 6%, and RAP samples collapsed during conserving in water. The optimum water content rose from 6.5% to 11% with the declining of A/S from S=0 to A/S=1/5. Five RAP samples all got the maximum compressive strength when A/S=5/5, and the maximum compressive strength of the samples adding 6% cement was 3.17 MPa. It showed that the capacity of RAP was not only affected by A/S, but also by the content of cement. The dynamic modulus of RAP will increase with the rise of loading frequency and decrease with the temperature rising. SEM test showed that C-S-H interlacing formed the netted structure, and it enwrapped the aggregate and improved the strength of RAP.展开更多
Reclaimed asphalt pavement (RAP) is a byproduct of milling flexible pavements and is typically used in recycling initiatives worldwide. The excessive dosage of RAP can have negative effects on asphalt mixture properti...Reclaimed asphalt pavement (RAP) is a byproduct of milling flexible pavements and is typically used in recycling initiatives worldwide. The excessive dosage of RAP can have negative effects on asphalt mixture properties unless it goes through a rejuvenation process. Waste cooking oil (WcO) is one of the green solutions for rejuvenating aged binder in asphaltic concrete, and, like virgin asphalt binder, it contains light oil components. This review article offers current information on WCO's rejuvenating performance and the effect of its variable dosage on binders of varying grades. Several physical and rheological characteristics were investigated, and an appropriate spectrum of reported data was defined for the virgin and rejuvenated binders to ascertain the distinctive characteristics.Additionally, the effect of WCO on binders' asphaltene content, molecular structure,microscopic morphology, mechanical properties, and aging indices was discussed. In the high point of this review, a data range is developed for rejuvenated aged binders based on different properties prior to making a better prediction under different circumstances.Moreover, an optimum value is discussed suggesting the best balance between fatigue performance and rutting resistance. The aged binders modified with WCO exhibit better microchemical properties and particle orientation, with enhanced surface area and coating with aggregates, imitating the micropattern of conventional asphalt binder. Moreover, this review further discusses the economic and ecological aspects of WCO usage as a green asphalt binder rejuvenator.展开更多
In this study,reclaimed asphalt pavement(RAP)used in different percentages in hot mix asphalt(HMA)and warm mix asphalt(WMA)were tested for moisture,fracture and rutting resistance adding hydrogenated castor oil flakes...In this study,reclaimed asphalt pavement(RAP)used in different percentages in hot mix asphalt(HMA)and warm mix asphalt(WMA)were tested for moisture,fracture and rutting resistance adding hydrogenated castor oil flakes(HCOF)as rejuvenating agent.Volumetric and Marshall parameters were evaluated for both types of mixtures.Addition of 5%of HCOF by weight of binder content in RAP found to restore properties of aged binder.WMA mix was made by adding 0.1%Zycotherm by weight of optimum binder content.Moisture,rutting and fracture damage performance were assessed utilizing indirect tensile strength,wheel tracking and semi-circular bending tests.The mix's tensile strength ratio increased by 2.3%in the HMA with RAP(HMA-R)mix compared to the WMA with RAP(WMA-R)mix at 10%RAP content.HMA mixes provide better resistance to rutting compared to WMA.However,40%of RAP content HMA-R and WMA-R using HCOF rejuvenator shows greater rutting performance compared to other RAP mix.HMA-R mix fracture resistance increased by 18.14%compared to WMA-R mix when RAP content increases to 40%.Regression analyses were carried out to validate the strain energy found from fracture damage analysis of both HMA-R and WMA-R with R2 value more than 0.9.HMA-R protected moisture and fracture damage better than WMA-R.The rejuvenating efficiency of HCOF was further validated using Fourier transform infrared and microscopic analysis.展开更多
Long-life pavement has been introduced to address the urgent need for durable and reliable transportation infrastructure.This review overviews the development of aggregates for long-life pavements and summarizes futur...Long-life pavement has been introduced to address the urgent need for durable and reliable transportation infrastructure.This review overviews the development of aggregates for long-life pavements and summarizes future research directions.The review indicates that natural aggregates,being non-renewable resources,are steadily declining in availability and may need to meet future demands.Construction solid waste aggregates are rapidly developing,with fine separation of reclaimed asphalt pavement(RAP)and reinforcement of cementbased recycled aggregates serving as key strategies to enhance their application.Industry solid waste aggregates possess properties suitable for long-life pavements and offer additional functionalities such as cooling,conductivity,and reflectivity,demonstrating significant development potential.While artificial aggregates exhibit superior performance,their large-scale application requires consideration of economic and environmental impacts.Current aggregate evaluation methods need to address the needs of long-life pavements.Aggregate performance requirements should be graded based on mechanical stress and temperature distribution,with corresponding evaluation methods and indices developed.Evaluating the mechanical properties of aggregates should align more closely with actual stress states.Tests such as triaxial,repeated load,and wheel abrasion polishing are better suited for assessing the strength and durability of long-life pavement aggregates.Similarly,evaluating aggregates'physicochemical properties should be based on studies correlating these properties with road performance,with proposed evaluation criteria.Morphological characteristics of aggregates significantly influence asphalt mixture performance,and efficient evaluation of their profile,angularity,and texture will be a key focus of future research.展开更多
Incorporation of warm mix asphalt （WMA） and reclaimed asphalt pavement （RAP） has benefited the asphalt industry in many ways such as reducing the demand for virgin materials, lowering energy requirement during the...Incorporation of warm mix asphalt （WMA） and reclaimed asphalt pavement （RAP） has benefited the asphalt industry in many ways such as reducing the demand for virgin materials, lowering energy requirement during the asphalt production and construction, in addition to reducing greenhouse-gas emissions. This study evaluated the effects of Evotherm and RH-WMA and RAP on mixtures＇ behavior in terms of the compaction energy index （CEI）, indirect tensile strength （ITS） and resilient modulus. The results showed that warm mix additives reduced the CEI, ITS and resilient modulus; while RAP increased the corresponding values. Statistical analysis showed that mixtures incorporating Evotherm and RAP had significant effects on CEI, while the effects of RH-WMA on the corresponding value were found to be statistically insignificant. General Linear Model showed that Evotherm, RAP and RH-WMA exhibited no significant effects on the ITS and resilient modulus. The one-way analysis of variance showed that Evotherm influenced mixture behavior significantly, while RAP and RH-WMA effects were found to be statistically insignificant. Regression equations with high accuracy levels were proposed to predict CEI, ITS and resilient modulus with respect to modification of mixture variables such as mix constituents （Evotherm, RH-WMA, and RAP） and compaction temperature.展开更多
The shortage of natural aggregates is becoming a severe problem in the pavement industry globally.To address this issue,in this study,an effort was made to use reclaimed asphalt pavement(RAP)and coal gangue(CG)as coar...The shortage of natural aggregates is becoming a severe problem in the pavement industry globally.To address this issue,in this study,an effort was made to use reclaimed asphalt pavement(RAP)and coal gangue(CG)as coarse and fine aggregate,respectively for producing the hot mix asphalt(HMA).As the replacement of natural aggregate,there were seven types of HMA containing 20%and 40%RAP coarse aggregate content,and 10%and 25%CG fine aggregate content were designed and prepared.In addition,Marshall Stability test,rutting resistance test,immersion Marshall test,freezing-thaw splitting test,moisture-induced sensitivity test,and low-temperature semicircle bending test were conducted.The results show that the properties of the asphalt mixture containing both RAP and CG meet the Chinese specification through it is slightly lower than the virgin asphalt mixture.Furthermore,the addition of 40%RAP coarse aggregate and 25%CG fine aggregate to asphalt mixes can significantly reduce manufacturing costs,energy consumption,and CO_(2)emissions by 29.4%,19.8%,and 21.9%,respectively,compared to the virgin asphalt mixture.The finding of this study contributes to current knowledge by investigating the feasibility of jointly using the RAP and CG in asphalt mixture,which could be interested by both industry and academic society.展开更多
A new research method was proposed（A/S method） to study the components and properties of reclained asphalt mixture（RAP）. The RAP was divided into two main parts, one was marked with A that included all the reclaim...A new research method was proposed（A/S method） to study the components and properties of reclained asphalt mixture（RAP）. The RAP was divided into two main parts, one was marked with A that included all the reclaimed old asphalt materials（including some parts of particle materials covered by asphalt）, the other was marked with S which mainly included works soil in the road structure. The actual working conditions were simulated by this kind of new method, and the adaption between the RAP properties, A/S, and the content of cementitious materials were studied. The research indicated that the real working condition could be simulated effectively by means of A/S method. It was also showed that high content of cement could improve the overall performance of RAP significantly, but it would have a negative effect on the properties of RAP if the types and sizes of aggregate particles in RAP mixture were too single. The optimum water content and maximum dry density could not be regarded as the primary basis to evaluate the overall performance of RAP, when S=0 in the experiments, although the maximum density of samples was bigger than that with A/S=1/1, the samples were not strong enough and they were easy to collapse, which indicated that component design of RAP played a great role in improving the overall properties of RAP and the comprehensive tests should be considered to evaluate the stability of RAP. Low frequency load in high temperature environment had the negative effect on the overall stability of RAP, and factors such as the loading state of the materials, the hydration degree of cementitious materials, and the aggregate gradation in the mixture were the determining factors for improving the overall performance of RAP.展开更多
Cold milling is a widely used method for rehabilitating asphalt pavement,generating reclaimed asphalt pavement(RAP)chunks.Within this process,aggregates within the asphalt pavement will be crushed,forming RAP agglomer...Cold milling is a widely used method for rehabilitating asphalt pavement,generating reclaimed asphalt pavement(RAP)chunks.Within this process,aggregates within the asphalt pavement will be crushed,forming RAP agglomerates and aggregate breakdown.However,the mechanism of these phenomena has remained unclear,and a unified evaluation method has yet to be established.In this study,RAP agglomeration and aggregate fragmentation were characterized,five distinct methods were systematically assessed,and the mechanism of RAP agglomeration and breakdown was analyzed by discrete element method(DEM)simulation based on setting different particle contact parameters,then followed by a mechanical analysis,and demonstrated in engineering.The results revealed that both agglomeration and aggregate breakdown occur within RAP particles of various sizes,with the five methods showing similar trends in quantifying these effects.Through DEM simulations and mechanical analyses,the aggregate breakdown predominantly occurs at the cutter's motion trajectory of the cutter and during crack propagation,while agglomeration was mainly related to the sliding surface's area.The milling speed and depth positively impact RAP agglomeration,while negatively affecting aggregate breakdown,and milling drum speed exerts minimal influence on these phenomena.RAP agglomeration varies considerably in different engineering projects,and cold milling parameters should be determined based on the material composition of the asphalt pavement and design requirements to control agglomeration and breakdown rates of RAP.展开更多
The use of reclaimed asphalt pavement （RAP） in new hot mix asphalt （HMA） by means of hot recycling techniques generates the advantage linked to the exploitation of both lytic and bituminous component, consequently...The use of reclaimed asphalt pavement （RAP） in new hot mix asphalt （HMA） by means of hot recycling techniques generates the advantage linked to the exploitation of both lytic and bituminous component, consequently leading to the decrease of both virgin aggregates and bitumen supplying. However, many agencies and public administration authorise RAP percentages ranges from 10% to 30% in hot recycling. The main reason for such a low amount of allowable RAP content is related to the aged bitumen contained in the RAP materials, which is more brittle than a virgin bitumen leading to a final mixture more susceptible to fatigue, thermal and reflection cracking. The use of rejuvenators has the potential to restore rheology and chemical components of aged RAP bitumen, thus allowing a significant increase in the amount of RAP to be properly implemented in HMA. The experimental investigation is described in this paper and carried out through a dynamic shear rheometer （DSR） which provides the rheological characterisation of a paving grade bitumen during its overall service life including its reuse in hot recycling by adopting different rejuvenators. Results show that rejuvenators modify bitumen chemistry and consequently rheology by enhancing the viscous response. Moreover, it was observed that oxidation is less harmful, in terms of stiffness increase, on the 50/50 aged bitumen - virgin bitumen blends （rejuvenated or not） than on the virgin bitumen. Moreover, the addition of a rejuvenator in a bituminous blend containing 50% of bitumen reactivated from RAP could lead to a corresponding composite bituminous phase less subjected to ageing phenomena and even less stiff at the end of service life than the associated virgin bitumen alone.展开更多
Worldwide,flexible pavements are the paramount type of pavements.These national assets can be recycled to serve the next design life without the need to dispose of them in landfill.The old/distressed,flexible pavement...Worldwide,flexible pavements are the paramount type of pavements.These national assets can be recycled to serve the next design life without the need to dispose of them in landfill.The old/distressed,flexible pavement material is called,reclaimed asphalt pavement(RAP)material.In view of the sustainable development practice,100%RAP should be recycled.However,the practical range of RAP incorporation in a drum mix plant ranges from 10%to 50%whereas in a batch mix plant,it is 10%-35%.In a batch mix plant,incorporation of the hot dried RAP(instead of cold RAP feeding)can increase the RAP incorporation level by 20%.Studies recommended that the rejuvenator should be added over the RAP material instead adding with the base binder.The addition of rejuvenator on the RAP conveyor belt(to the pug mill),provided sufficient time for rejuvenating the aged binder coating over RAP aggregates.Further,a thorough knowledge of the mix design process of recycled hot mix asphalt(RAP-HMA)is essential to produce a durable mix.For high RAP content(>20%),the RAP binder properties are important for the mix design process.However,very limited studies discussed(in detail)the recovery process of the RAP binder.The review article through light on the binder recovery process,method of RAP gradation,specific gravity determination for RAP material,minimum desirable properties of the RAP material etc.This review paper also provides a narrative review of the historical development of RAP-HMA technology,technical aspects related to the procurement of RAP material,mix design and production of the recycled mix.Moreover,the international&national policies/laws for construction and demolition waste are discussed.展开更多
基金Project(200831800044) supported by the Ministry of Communication of ChinaProject(50878054) supported by the National Natural Science Foundation of ChinaProject(06Y31) supported by the Department of Communication of Zhejiang Province,China
文摘A new testing procedure to estimate the low-temperature stiffness of the reclaimed asphalt pavement （RAP） binder was developed. In the testing procedure, the SuperpaveTM Bending Beam Rheometer （BBR） with special modifications and binder blending charts by Asphalt Institute were utilized. Modifications involved the development of a new kind of sample mold and different testing parameters were made to BBR testing procedure to capture the theological properties of bitumen mortars produced by mixing fresh binder with fine RAP materials or RAP aggregate. The stiffness relationship between binder and bitumen mortar was established based on the BBR test results. The blended binder stiffness in bitumen RAP mortar was estimated from the RAP mortar stiffness based on the binder-mortar relationship. And finally, the RAP binder stiffness was estimated from the blended binder and fresh binder stiffness based on the blending charts by Asphalt Institute. The results indicate that the new procedure can capture the rheological properties of bitumen mortar and can be used to estimate the low temperature stiffness of RAP binder without binder extraction and/or any chemical treatments.
基金This paper was financially supported by the National Natural Science Foundation of China(No.52178420 and 51878229)Research Project of Liaoning Provincial Transportation Investment Group Co.,Ltd.(202004)Key R&D projects in Liaoning Province(No.2020JH2/10300097).
文摘Reclaimed asphalt pavement(RAP)has significant recycling value because it contains nonrenewable resources including asphalt and aggregate.However,thus far,only a small part of RAP materials can be used in the con-struction of recycled asphalt pavement,and the usage is regarded as a low-value utilization in the underlying layers.One of the most important reasons for this shortcoming is the problem of false particle size and pseudo gradation of RAP materials.Therefore,identifying suitable asphalt-aggregate separation technology is essential for improving the utilization of RAP materials in recycled asphalt mixture and enhancing the construction quality of recycled asphalt pavement.To address this,the paper performed a systematic review of asphalt-aggregate separation technologies for processing RAP materials and their prospects.Firstly,based on the composition of the asphalt mixture and the characteristics of RAP materials after aging,the key RAP separation technologies were proposed.Then,the concept,principle,and implementation methods of physical,chemical,and biological sep-aration methods of RAP materials were comprehensively analyzed.Moreover,the advantages and disadvantages of various separation technologies were discussed by comparing them with the related technologies in the petrochemical industry.The application prospects of various asphalt-aggregate separation methods for RAP materials can provide a reference for upgrading and expanding solid waste recycling technology for asphalt pavement.
基金the Office of Research&Economic Development and Department of Civil,Coastal and Environmental Engineering at University of South Alabama for the support.
文摘The utilization of reclaimed asphalt pavement(RAP)in asphalt mixtures has gained momentum in recent years,yet concerns persist regarding the long-term performance and binder properties of high RAP content mixtures.To overcome these challenges,rejuvenators have emerged as a promising solution to enhance the properties of aged asphalt binders and improve the overall performance of asphalt mixtures.This paper provides a comprehensive state-of-the-art review of rejuvenator technology and its potential to enhance the performance and sustainability of asphalt pavements.Rejuvenators are additives used to restore the properties of aged asphalt binders,particularly when incorporating high percentages of RAP.The performance of these additives varies based on their origin,and different methods can be used to analyze the rejuvenation process.Since proper specifications for rejuvenators are not available,blending charts are used to determine the optimum dosage of rejuvenators.However,proper blending must be achieved to maximize results and reduce the effect of black rock.Laboratory tests and some field performance studies on rejuvenated aged asphalt binders and RAP mixtures have shown improved or similar performance compared to virgin materials.Additionally,the use of rejuvenators has been observed to reduce construction costs,suggesting that this is a cost-effective technology for asphalt pavements.While rejuvenators show promise in improving the performance of pavements with recycled materials,challenges remain regarding optimization,long-term durability,and environmental effects.This review paper also identifies key areas for future research,including life-cycle cost analyses,comprehensive environmental impact assessments,and long-term field performance monitoring.
文摘The performance of roller compacted concrete(RCC)was greatly influenced by variations in material proportion,optimum moisture content,density of mixes and methodology adopted making it different from conventional concrete mixes.Even though RCC has gained popularity,the complex phenomenon involved in developing the RCC mixes limits it from large-scale applications.In this study,reclaimed asphalt pavement(RAP)incorporated roller-compacted geopolymer concrete(RGC)mixes were developed herein with different compaction techniques such as vibratory hammer(VH),modified proctor(MP),vibration table(VT)and compression machine(CM)are studied and compared with control mixes of natural aggregates.Initially,the effect of alkali solutions such as sodium hydroxide(SH)and sodium silicate(SS)on the physical properties.During,the second phase mechanical properties such as dry density,compressive,flexural and split-tensile strength,modulus of elasticity and microstructure properties will be investigated.The test results revealed that compaction efforts were greatly influenced by the alkali solution.Furthermore,the poor bond characteristics between RAP and the binder matrix had a significant effect on strength properties.Also,the various compaction techniques affected the mechanical properties of mixes developed herein.In Comparison with various compaction efforts,VH and MP produced comparable results,whereas the VT method underestimated and overestimated the various strength properties.Although,the CM method reports comparable results but difficult to maintain consistency in strength aspects.Therefore,optimization of various parameters influencing the concrete properties needs to be achieved for field density.
基金Funded by the National High-tech Research and Development Program of China ('863' Program) (2009AA11Z106)
文摘The property of reclaimed asphalt pavement（RAP） mixture will be affected mainly by composition of old asphalt/soil and cement content in CIR system. We studied the relationship between A/S and cementitious materials. It showed that if there was no soil in RAP, the unconfined compressive strength was only from 0.18 MPa to 1.07 MPa even if adding cement was from 2% to 6%, and RAP samples collapsed during conserving in water. The optimum water content rose from 6.5% to 11% with the declining of A/S from S=0 to A/S=1/5. Five RAP samples all got the maximum compressive strength when A/S=5/5, and the maximum compressive strength of the samples adding 6% cement was 3.17 MPa. It showed that the capacity of RAP was not only affected by A/S, but also by the content of cement. The dynamic modulus of RAP will increase with the rise of loading frequency and decrease with the temperature rising. SEM test showed that C-S-H interlacing formed the netted structure, and it enwrapped the aggregate and improved the strength of RAP.
基金The authors sincerely acknowledge the Ministry of Higher Education,Malaysia for the Fundamental Research Grant Scheme with Project Code:FRGS/1/2021/TK01/USM/02/1Appreciation also goes to the deanship of scientific research at King Khalid University for funding this work through large group research project under grant number(RGP2/418/45).
文摘Reclaimed asphalt pavement (RAP) is a byproduct of milling flexible pavements and is typically used in recycling initiatives worldwide. The excessive dosage of RAP can have negative effects on asphalt mixture properties unless it goes through a rejuvenation process. Waste cooking oil (WcO) is one of the green solutions for rejuvenating aged binder in asphaltic concrete, and, like virgin asphalt binder, it contains light oil components. This review article offers current information on WCO's rejuvenating performance and the effect of its variable dosage on binders of varying grades. Several physical and rheological characteristics were investigated, and an appropriate spectrum of reported data was defined for the virgin and rejuvenated binders to ascertain the distinctive characteristics.Additionally, the effect of WCO on binders' asphaltene content, molecular structure,microscopic morphology, mechanical properties, and aging indices was discussed. In the high point of this review, a data range is developed for rejuvenated aged binders based on different properties prior to making a better prediction under different circumstances.Moreover, an optimum value is discussed suggesting the best balance between fatigue performance and rutting resistance. The aged binders modified with WCO exhibit better microchemical properties and particle orientation, with enhanced surface area and coating with aggregates, imitating the micropattern of conventional asphalt binder. Moreover, this review further discusses the economic and ecological aspects of WCO usage as a green asphalt binder rejuvenator.
文摘In this study,reclaimed asphalt pavement(RAP)used in different percentages in hot mix asphalt(HMA)and warm mix asphalt(WMA)were tested for moisture,fracture and rutting resistance adding hydrogenated castor oil flakes(HCOF)as rejuvenating agent.Volumetric and Marshall parameters were evaluated for both types of mixtures.Addition of 5%of HCOF by weight of binder content in RAP found to restore properties of aged binder.WMA mix was made by adding 0.1%Zycotherm by weight of optimum binder content.Moisture,rutting and fracture damage performance were assessed utilizing indirect tensile strength,wheel tracking and semi-circular bending tests.The mix's tensile strength ratio increased by 2.3%in the HMA with RAP(HMA-R)mix compared to the WMA with RAP(WMA-R)mix at 10%RAP content.HMA mixes provide better resistance to rutting compared to WMA.However,40%of RAP content HMA-R and WMA-R using HCOF rejuvenator shows greater rutting performance compared to other RAP mix.HMA-R mix fracture resistance increased by 18.14%compared to WMA-R mix when RAP content increases to 40%.Regression analyses were carried out to validate the strain energy found from fracture damage analysis of both HMA-R and WMA-R with R2 value more than 0.9.HMA-R protected moisture and fracture damage better than WMA-R.The rejuvenating efficiency of HCOF was further validated using Fourier transform infrared and microscopic analysis.
基金sponsored by the National Natural Science Foundation of China(52178420,52408476)Research Project of Liaoning Provincial Transportation Construction Investment Group Co.,Ltd.(202410)+1 种基金Postdoctoral Fellowship Program of CPSF(GZC20242207)the Fundamental Research Funds for the Central Universities(HIT.DZJJ.2023086).
文摘Long-life pavement has been introduced to address the urgent need for durable and reliable transportation infrastructure.This review overviews the development of aggregates for long-life pavements and summarizes future research directions.The review indicates that natural aggregates,being non-renewable resources,are steadily declining in availability and may need to meet future demands.Construction solid waste aggregates are rapidly developing,with fine separation of reclaimed asphalt pavement(RAP)and reinforcement of cementbased recycled aggregates serving as key strategies to enhance their application.Industry solid waste aggregates possess properties suitable for long-life pavements and offer additional functionalities such as cooling,conductivity,and reflectivity,demonstrating significant development potential.While artificial aggregates exhibit superior performance,their large-scale application requires consideration of economic and environmental impacts.Current aggregate evaluation methods need to address the needs of long-life pavements.Aggregate performance requirements should be graded based on mechanical stress and temperature distribution,with corresponding evaluation methods and indices developed.Evaluating the mechanical properties of aggregates should align more closely with actual stress states.Tests such as triaxial,repeated load,and wheel abrasion polishing are better suited for assessing the strength and durability of long-life pavement aggregates.Similarly,evaluating aggregates'physicochemical properties should be based on studies correlating these properties with road performance,with proposed evaluation criteria.Morphological characteristics of aggregates significantly influence asphalt mixture performance,and efficient evaluation of their profile,angularity,and texture will be a key focus of future research.
基金the Malaysian Ministry of Higher Education for funding this research through the Exploratory Research Grant Scheme (ERGS grant number 203/ PAWAM/6730111)
文摘Incorporation of warm mix asphalt （WMA） and reclaimed asphalt pavement （RAP） has benefited the asphalt industry in many ways such as reducing the demand for virgin materials, lowering energy requirement during the asphalt production and construction, in addition to reducing greenhouse-gas emissions. This study evaluated the effects of Evotherm and RH-WMA and RAP on mixtures＇ behavior in terms of the compaction energy index （CEI）, indirect tensile strength （ITS） and resilient modulus. The results showed that warm mix additives reduced the CEI, ITS and resilient modulus; while RAP increased the corresponding values. Statistical analysis showed that mixtures incorporating Evotherm and RAP had significant effects on CEI, while the effects of RH-WMA on the corresponding value were found to be statistically insignificant. General Linear Model showed that Evotherm, RAP and RH-WMA exhibited no significant effects on the ITS and resilient modulus. The one-way analysis of variance showed that Evotherm influenced mixture behavior significantly, while RAP and RH-WMA effects were found to be statistically insignificant. Regression equations with high accuracy levels were proposed to predict CEI, ITS and resilient modulus with respect to modification of mixture variables such as mix constituents （Evotherm, RH-WMA, and RAP） and compaction temperature.
基金the Natural Science Foundation of Jiangxi Province of China(Grant No.20202BABL214046)lthe Natural Science Foundation of Uygur Autonomous Region of China(Grant No.2020D01A92)l the China Postdoctoral Science Foundation(2020M683709XB).
文摘The shortage of natural aggregates is becoming a severe problem in the pavement industry globally.To address this issue,in this study,an effort was made to use reclaimed asphalt pavement(RAP)and coal gangue(CG)as coarse and fine aggregate,respectively for producing the hot mix asphalt(HMA).As the replacement of natural aggregate,there were seven types of HMA containing 20%and 40%RAP coarse aggregate content,and 10%and 25%CG fine aggregate content were designed and prepared.In addition,Marshall Stability test,rutting resistance test,immersion Marshall test,freezing-thaw splitting test,moisture-induced sensitivity test,and low-temperature semicircle bending test were conducted.The results show that the properties of the asphalt mixture containing both RAP and CG meet the Chinese specification through it is slightly lower than the virgin asphalt mixture.Furthermore,the addition of 40%RAP coarse aggregate and 25%CG fine aggregate to asphalt mixes can significantly reduce manufacturing costs,energy consumption,and CO_(2)emissions by 29.4%,19.8%,and 21.9%,respectively,compared to the virgin asphalt mixture.The finding of this study contributes to current knowledge by investigating the feasibility of jointly using the RAP and CG in asphalt mixture,which could be interested by both industry and academic society.
基金Funded by the Natural Science Foundation of Fujian Province(Nos.2016J01241 and 2016H0021)the Science & Technology Pillar Program of Fujian Provincial Education Department(No.Z1425072)
文摘A new research method was proposed（A/S method） to study the components and properties of reclained asphalt mixture（RAP）. The RAP was divided into two main parts, one was marked with A that included all the reclaimed old asphalt materials（including some parts of particle materials covered by asphalt）, the other was marked with S which mainly included works soil in the road structure. The actual working conditions were simulated by this kind of new method, and the adaption between the RAP properties, A/S, and the content of cementitious materials were studied. The research indicated that the real working condition could be simulated effectively by means of A/S method. It was also showed that high content of cement could improve the overall performance of RAP significantly, but it would have a negative effect on the properties of RAP if the types and sizes of aggregate particles in RAP mixture were too single. The optimum water content and maximum dry density could not be regarded as the primary basis to evaluate the overall performance of RAP, when S=0 in the experiments, although the maximum density of samples was bigger than that with A/S=1/1, the samples were not strong enough and they were easy to collapse, which indicated that component design of RAP played a great role in improving the overall properties of RAP and the comprehensive tests should be considered to evaluate the stability of RAP. Low frequency load in high temperature environment had the negative effect on the overall stability of RAP, and factors such as the loading state of the materials, the hydration degree of cementitious materials, and the aggregate gradation in the mixture were the determining factors for improving the overall performance of RAP.
基金found by the National Natural Science Foundation of China(grant number 52268068,52368062,52368064)the Natural Science Foundation of Jiangxi Province(grant number 20232BAB214076,20232BAB204085)+3 种基金the National High-level University Scholarship Program(grant number 202306560084)the Fundamental Research Funds for the Central Universities,CHD(grant number 300102210501)the Tianshan Leading Talents in Scientific and Technological Innovation(grant number 2022TSYCLJ0045)the Science and Technology Projects of Xinjiang Communications Investment Group Co.,Ltd(grant number ZKXFWCG-202211-010).
文摘Cold milling is a widely used method for rehabilitating asphalt pavement,generating reclaimed asphalt pavement(RAP)chunks.Within this process,aggregates within the asphalt pavement will be crushed,forming RAP agglomerates and aggregate breakdown.However,the mechanism of these phenomena has remained unclear,and a unified evaluation method has yet to be established.In this study,RAP agglomeration and aggregate fragmentation were characterized,five distinct methods were systematically assessed,and the mechanism of RAP agglomeration and breakdown was analyzed by discrete element method(DEM)simulation based on setting different particle contact parameters,then followed by a mechanical analysis,and demonstrated in engineering.The results revealed that both agglomeration and aggregate breakdown occur within RAP particles of various sizes,with the five methods showing similar trends in quantifying these effects.Through DEM simulations and mechanical analyses,the aggregate breakdown predominantly occurs at the cutter's motion trajectory of the cutter and during crack propagation,while agglomeration was mainly related to the sliding surface's area.The milling speed and depth positively impact RAP agglomeration,while negatively affecting aggregate breakdown,and milling drum speed exerts minimal influence on these phenomena.RAP agglomeration varies considerably in different engineering projects,and cold milling parameters should be determined based on the material composition of the asphalt pavement and design requirements to control agglomeration and breakdown rates of RAP.
文摘The use of reclaimed asphalt pavement （RAP） in new hot mix asphalt （HMA） by means of hot recycling techniques generates the advantage linked to the exploitation of both lytic and bituminous component, consequently leading to the decrease of both virgin aggregates and bitumen supplying. However, many agencies and public administration authorise RAP percentages ranges from 10% to 30% in hot recycling. The main reason for such a low amount of allowable RAP content is related to the aged bitumen contained in the RAP materials, which is more brittle than a virgin bitumen leading to a final mixture more susceptible to fatigue, thermal and reflection cracking. The use of rejuvenators has the potential to restore rheology and chemical components of aged RAP bitumen, thus allowing a significant increase in the amount of RAP to be properly implemented in HMA. The experimental investigation is described in this paper and carried out through a dynamic shear rheometer （DSR） which provides the rheological characterisation of a paving grade bitumen during its overall service life including its reuse in hot recycling by adopting different rejuvenators. Results show that rejuvenators modify bitumen chemistry and consequently rheology by enhancing the viscous response. Moreover, it was observed that oxidation is less harmful, in terms of stiffness increase, on the 50/50 aged bitumen - virgin bitumen blends （rejuvenated or not） than on the virgin bitumen. Moreover, the addition of a rejuvenator in a bituminous blend containing 50% of bitumen reactivated from RAP could lead to a corresponding composite bituminous phase less subjected to ageing phenomena and even less stiff at the end of service life than the associated virgin bitumen alone.
基金supported by Prime Minister’s Fellowship for Doctoral Researchsponsored by industrial body Shell India Markets Pvt.Ltd.Government body Federation of Indian Chambers of Commerce&Industry(FICCI)-Science and Engineering Research Board(SERB),India。
文摘Worldwide,flexible pavements are the paramount type of pavements.These national assets can be recycled to serve the next design life without the need to dispose of them in landfill.The old/distressed,flexible pavement material is called,reclaimed asphalt pavement(RAP)material.In view of the sustainable development practice,100%RAP should be recycled.However,the practical range of RAP incorporation in a drum mix plant ranges from 10%to 50%whereas in a batch mix plant,it is 10%-35%.In a batch mix plant,incorporation of the hot dried RAP(instead of cold RAP feeding)can increase the RAP incorporation level by 20%.Studies recommended that the rejuvenator should be added over the RAP material instead adding with the base binder.The addition of rejuvenator on the RAP conveyor belt(to the pug mill),provided sufficient time for rejuvenating the aged binder coating over RAP aggregates.Further,a thorough knowledge of the mix design process of recycled hot mix asphalt(RAP-HMA)is essential to produce a durable mix.For high RAP content(>20%),the RAP binder properties are important for the mix design process.However,very limited studies discussed(in detail)the recovery process of the RAP binder.The review article through light on the binder recovery process,method of RAP gradation,specific gravity determination for RAP material,minimum desirable properties of the RAP material etc.This review paper also provides a narrative review of the historical development of RAP-HMA technology,technical aspects related to the procurement of RAP material,mix design and production of the recycled mix.Moreover,the international&national policies/laws for construction and demolition waste are discussed.
