The objective of this paper was to study low temperature crack resistance mechanism of steel slag asphalt mixture(SAM).Thermal stress restrained specimen test(TSRST)and three-point bending test were carried out to eva...The objective of this paper was to study low temperature crack resistance mechanism of steel slag asphalt mixture(SAM).Thermal stress restrained specimen test(TSRST)and three-point bending test were carried out to evaluate the low-temperature crack resistance of SAM and basalt asphalt mixture(BAM).Based on the digital image correlation technique(DIC),the strain field distribution and crack propagation of SAM were analyzed from the microscopic point of view,and a new index,crack length factor(C),was proposed to evaluate the crack resistance of the asphalt mixture.The crystal phase composition and microstructure of steel slag aggregate(SA)and basalt aggregate(BA)were studied by X-ray diffraction(XRD)and scanning electron microscopy(SEM)to explore the low-temperature crack resistance mechanism of SAM.Results show that the low-temperature crack resistance of SAM is better than that of BAM;SAM has good integrity and persistent elastic deformation,and its bending failure mode is a hysteretic quasi-brittle failure;The SA surface is evenly distributed with pores and has surface roughness.SA has the composition phase of alkaline aggregate-calcite(CaCO3),so it has good adhesion to asphalt,which reveals the mechanism of excellent low-temperature crack resistance of SAM.展开更多
The application of reclaimed asphalt pavement(RAP)and reclaimed asphalt shingles(RAS)on asphalt pavement can reduce the asphalt paving cost,conserve energy and protect the environment.However,the use of high contents ...The application of reclaimed asphalt pavement(RAP)and reclaimed asphalt shingles(RAS)on asphalt pavement can reduce the asphalt paving cost,conserve energy and protect the environment.However,the use of high contents of RAP and RAS in asphalt pavement may lead to durability issues,especially the fatigue cracking and thermal cracking.It is necessary to conduct a series of analyses on asphalt mixtures containing high RAP and RAS,and seek methods to enhance their long-term performance.This paper provides a comprehensive over-view of the long-term performance of recycled asphalt mixtures containing high contents of RAP and RAS.The findings in this research show that rutting resistance of high recycled asphalt mixtures is not a concern,whereas their resistance to fatigue and thermal cracking is not conclusive.Recycling agents can be used to improve the thermal cracking resistance of high recycled asphalt mixtures.An optimum decision on recycling agents will improve the durability properties of high recycled asphalt mixtures.It is recommended that to use a balanced mixture design approach with testing of the blended asphalt binders will provide better understanding of long-term performance of recycled asphalt mixtures containing high RAP and RAS.展开更多
This study normalized the mixture's fatigue behavior at various temperatures,and the strength and fatigue tests of the mixture were conducted.The stress state of the asphalt mixture includes direct tensile,uniaxia...This study normalized the mixture's fatigue behavior at various temperatures,and the strength and fatigue tests of the mixture were conducted.The stress state of the asphalt mixture includes direct tensile,uniaxial compression,and indirect tensile.The Desai yield surface and fatigue path were proposed.And a normalized fatigue characteristics model of the mixture was established.The following conclusions were obtained.With the increases in the loading rate,the strength of the asphalt mixture increased.As the temperature increases,the strength of the mixture is reduced.At various temperatures and rates,the strength forms a closed curved surface.The Desai strength yield surface was established,which forms a closed curved surface.When the loading rate and temperature are below a certain critical line,the asphalt mixture will not undergo strength damage.At a fixed stress state,the fatigue damage path of the mixture was determined.The stress ratio was determined considering the influence of the loading rate.In this way,a normalized model can be described to express the asphalt mixture fatigue properties at various temperatures and stress levels.For the asphalt mixture in an indirect tensile state,the normalized fatigue equation parameter is 4.09.This model is more suitable for reflecting the viscous-elastic behavior of the mixtures than the fatigue equation determined by the notional stress ratio.展开更多
Although there are many kinds of fracture tests to choose from in evaluating the crack resistance of asphalt mixture,the semi-circular bending(SCB)test has attracted a lot of attention in the academic road engineering...Although there are many kinds of fracture tests to choose from in evaluating the crack resistance of asphalt mixture,the semi-circular bending(SCB)test has attracted a lot of attention in the academic road engineering community because of its simplicity,stability,and flexibility in testing and evaluation.The SCB test has become a common method to study the cracking resistance of asphalt mixture in recent years.This paper mainly summarizes the overview of the SCB test,summarizes some research results and common characterization parameters of the SCB test method in monotone test and fatigue test in recent years,and predicts and suggests the research direction of the SCB test in the future.It is found that the research on the monotonic SCB test is more comprehensive,and the research on the SCB fatigue test needs to be further improved in the aspects of loading mode,characterization parameter selection,and so on.Researchers can flexibly adjust the geometric dimensions and the test parameters of semi-cylindrical specimens,and conduct comprehensive analysis combined with the results of numerical simulation.The crack resistance of asphalt mixture can be comprehensively evaluated by fracture energy,fracture toughness,stiffness,flexibility index and other fracture indicators,combined with the crack propagation of the specimen.The analysis of numerical simulation can confirm the test results.In order to standardize the setting of fatigue parameters for future application,it is necessary to standardize the setting of bending performance.展开更多
In order to comprehensively utilize the remaining bamboo residue of bamboo products,this paper presents a research on recycling the bamboo fibers from bamboo residue for improving the performance of the asphalt mixtur...In order to comprehensively utilize the remaining bamboo residue of bamboo products,this paper presents a research on recycling the bamboo fibers from bamboo residue for improving the performance of the asphalt mixtures.First of all,the basic performance parameters of sinocalamus affinis fiber,phyllostachys pubescens fiber,green bamboo fiber were tested and analyzed,and the optimal content and length were put forward.Then,the mix ratio design of the bamboo fiber modified asphalt mixture was further designed through the response surface method,and was verified the rationality of the mix ratio.Finally,the mixture specimens were made according to the experimental design mix ratio,and the high temperature,low temperature performance and moisture susceptibility of the bamboo fiber modified mixtures asphalt were tested.The results showed that the high temperature performance,low temperature performance and moisture susceptibility of bamboo fiber modified asphalt mixtures were improved compared with the performance of SBS modified asphalt mixture.When the length of bamboo fiber is 7.25 mm and the content of 0.22%,the road performance of the asphalt mixture was optimal.Consequentially,the decomposition of bamboo residue into bamboo fiber and its application in asphalt pavement can improve the reuse of bamboo waste,with remarkable environmental benefits and great promotion value.展开更多
For evaluating the water stability of hot-mixed renewable asphalt mixture(HRM),the traditional methods are all tested under still water conditions.Except for damage in still water conditions,the hydrodynamic pore pres...For evaluating the water stability of hot-mixed renewable asphalt mixture(HRM),the traditional methods are all tested under still water conditions.Except for damage in still water conditions,the hydrodynamic pore pressure generated by the tire driving on the surface water has a great impact.Thus,the RAP contents of the HRMs were designed at 0%,30%,45%and 60%with AC-25 gradation.Then,the self-designed evaluation methods of water stability and dynamic modulus were studied.Finally,the mechanism of the influence of hydrodynamic pore pressure damage on HRMs was studied.The results show that the water stability of HRM containing 30%RAP is equivalent to that of 45%RAP,and the water stability of HRM containing 60%RAP decreases significantly.The Contabro test after MIST treatment can be used as an evaluation method for hydrodynamic pore pressure damage on HRM.Low-speed,heavy-load traffic and larger RAP content have greater damage to the mixture after hydrodynamic pore pressure damage.The performance differences between the aged bitumen and pure bitumen,as well as the aged minerals and new minerals,are continuing to be enlarged in hydrodynamic pore pressure conditions,finally affecting the water stability and dynamic modulus of the HRMs.展开更多
As a byproduct of the steelmaking process,significant amounts of hazardous electric arc furnace dust(EAFD)are produced.Utilizing the solidification/stabilization technology with asphalt mix is one way to safeguard the...As a byproduct of the steelmaking process,significant amounts of hazardous electric arc furnace dust(EAFD)are produced.Utilizing the solidification/stabilization technology with asphalt mix is one way to safeguard the environment from its negative effects.Rutting was used as an indicator to assess the asphalt mixture with EAFD since it is an important factor in pavement design.This study’s major goal is to ascertain how EAFD affects the rutting of asphalt-concrete mixtures.To evaluate the ideal asphalt content,the Marshall test method was applied to asphalt-concrete mixtures.EAFD was added to the asphalt cement in four different volume percentages as a binder addition.Then,using the Universal Testing Machine,participants were exposed to a replica of the rutting test(UTM).Experiments were conducted at 25℃,40℃ and 55℃,and at frequencies of 1 Hz,4 Hz and 8 Hz.Rutting was measured for each specimen.Test results showed that rut depth has a negative correlation with EAFD%and a positive correlation with temperature.The use of EAFD has dual advantages,protecting the environment from the adverse impact of EAFD and reducing the cost of asphalt mix without jeopardizing pavement performance.展开更多
The fatigue property of asphalt mixtures under complicated environment (low-temperature bending performance, chloride penetration, freezing-thawing cycle and their coupling effect) and the improvement effect for rel...The fatigue property of asphalt mixtures under complicated environment (low-temperature bending performance, chloride penetration, freezing-thawing cycle and their coupling effect) and the improvement effect for relevant property of basalt fiber-reinforcing asphalt mixture under complicated environment are studied. Two grading types of asphalt mixtures, AC-16I and AC-13I, are chosen, whose optimum asphalt-aggregate ratio and optimum dosage of basalt fiber are determined by the Marshall test. The standard specimens are made firstly, and then the low temperature bending tests of asphalt mixture and basalt fiber-reinforced asphalt mixture under the coupling effect of the chloride erosion and freezing-thawing cycle have been carried out. Finally, the fatigue property tests of asphalt mixture and basalt fiber-reinforced asphalt mixture under complex environment are performed on MTS material testing system. The results indicate that the tensile strength, the maximum curving tensile stress, the curving stiffness modulus, and fatigue properties of asphalt mixture are influenced by the coupling effect of the chloride erosion and freezing-thawing cycle. The low-temperature bending performance and fatigue property of asphalt mixtures under complicated environment can be greatly improved by adding moderate basalt fiber. The dense gradation asphalt mixture possesses stronger ability to resist adverse environmental effects under the same condition.展开更多
The dynamic characteristics of fiber-modified asphalt mixture were investigated. Cellulose fiber, polyester fiber and mineral fiber were used as additives for asphalt mixture, and the dosage was 0.3%, 0.3%, 0.4%, resp...The dynamic characteristics of fiber-modified asphalt mixture were investigated. Cellulose fiber, polyester fiber and mineral fiber were used as additives for asphalt mixture, and the dosage was 0.3%, 0.3%, 0.4%, respectively. Dynamic modulus test using SuperPave simple performance tester (SPT) was conducted to study the dynamic modulus (E') and phase angle (δ) for the control asphalt mixture and fiber-modified ones at various temperatures and frequencies. Experimental results show that all fiber-modified asphalt mixtures have higher dynamic modulus compared with control mixture. The dynamic modulus master curves of each type of asphalt mixtures are determined based on nonlinear least square regression in accordance with the time- temperature superposition theory at a control temperature (21.1℃). The fatigue parameter E^*×sinδ and rutting parameter E^*/sinδ of asphalt mixture are adopted to study the fatigue and rutting-resistance properties, and experimental results indicate that such properties can be improved by fiber additives.展开更多
Design method for large stone porous asphalt mixtures (LSPM) was analyzed to avoid the early distresses of semi-rigid asphalt pavements. Based on stone-to-stone skeleton structure concept, processes of LSPM gradatio...Design method for large stone porous asphalt mixtures (LSPM) was analyzed to avoid the early distresses of semi-rigid asphalt pavements. Based on stone-to-stone skeleton structure concept, processes of LSPM gradation design was given. The gradation composite design for LSPM shows that the LSPM nominal maximum size ( N MS) should be larger than 26.5 mm, and the NMS sieve passing percentage should be greater than 50%. Through experiments and calculations on the volume properties of the aggregate, the range of aggregate gradation curve of LSPM was given. In terms of asphalt binder's normalized test results, MAC-70 and SBS modified asphalt were selected as the asphalt binders. The applicability of large scale Marshall Method and gyratory compaction method to shape specimens was investigated. Based on the asphalt mixture performance evaluation, the optimum asphalt content range (3.1%-3.6%), the bitumen film's thickness range (13-16 μm) and the air void range (13%-18 %) were recommended. Finally, LSPM was tested by the laboratory performance tests including rutting resistance test, fatigue test and water stability test. The theoretic and practical analysis shows that LSPM has a good performance on water permeability, rutting resistance and reflection crack resistance.展开更多
A micromechanical model based on discrete element method(DEM) was employed to investigate the effects of aggregate size and specimen scale on the cracking behavior of asphalt mixture. An algorithm for generating thr...A micromechanical model based on discrete element method(DEM) was employed to investigate the effects of aggregate size and specimen scale on the cracking behavior of asphalt mixture. An algorithm for generating three-dimensional aggregates that can reflect the realistic geometry such as shape, size and fracture surface of aggregate particles was developed using a user-defined procedure coded with FISH language in particle flow code in three-dimensions(PFC3 D). The parallel-bond model(PBM), linear contact model(LCM), and slip model(SM), whose sets of micro parameters were obtained by comparing experimental tests with numerical simulation results, were used to characterize the internal contact behavior of asphalt mixture. Digital asphalt mixture specimens were used to simulate the effects of aggregate size and specimen scale on the cracking behavior by the indirect tensile(IDT) test. Some conclusions can be drawn as follows: Both cracks and IDT strength decrease with increasing aggregate size. However, the heterogeneity of contact-force distribution augments with increasing aggregate size, especially with 13.2-16 mm aggregate. The aggregate size of 4.75-9.5 mm dominates in forming skeleton structure for asphalt mixture. The IDT strength decreases and cracks augment with increasing sample scale. The crack growth can be well interpreted from the perspective of energy analysis. The conclusions show that the proposed micromechanical model is suitable for the simulation of crack propagation. This study provides an assistant tool to further study the cracking behavior of particle-reinforced composites material such as asphalt mixture and Portland cement concrete.展开更多
By using the falling weight deflectometer(FWD),the dynamic loading tests on different thickness of asphalt mixture pavement in different temperature were performed.The experimental results show that the effects of t...By using the falling weight deflectometer(FWD),the dynamic loading tests on different thickness of asphalt mixture pavement in different temperature were performed.The experimental results show that the effects of temperature on dynamic properties of asphalt mixture are significant,and the thickness of asphalt mixture is also another important influence factor.The comparisons indicate that effect of temperature on the behaviors of dynamic loading properties and static loading properties of asphalt mixture were quite different.展开更多
In order to study the effects of loading condition and temperature on the dynamic properties of asphalt mixtures, the dynamic loading tests on different loading condition (various speeds and loads under a certain rou...In order to study the effects of loading condition and temperature on the dynamic properties of asphalt mixtures, the dynamic loading tests on different loading condition (various speeds and loads under a certain roughness) and temperature conditions were performed. The experimental result show that the dynamic properties of asphalt mixtures are influenced by vehicle load and speed, besides, the effects of temperature on dynamic properties of asphalt mixture are significant.展开更多
On basis of the Burgers model, a new model consisting of modified dashpot and Van Der Poel model was derived from rheological and viscoelastic theory. Subsequently, triaxial repeated load permanent deformation tests o...On basis of the Burgers model, a new model consisting of modified dashpot and Van Der Poel model was derived from rheological and viscoelastic theory. Subsequently, triaxial repeated load permanent deformation tests of AC16 asphalt mixtures were conducted to validate this new developed model. Parameters of new developed model were obtained by a nonlinear regression analysis of test data, and then permanent strains and flow number of each mixture were calculated. The experimental results prove that the new developed model can well describe three phases permanent deformation of asphalt mixture under repeated load and it can be used for pavement mechanical analysis and rutting prediction.展开更多
A three-dimensional(3D) lattice model for predicting the rheological behavior of asphalt mixtures was presented.In this model asphalt mixtures were described as a two-phase composite material consisting of asphalt san...A three-dimensional(3D) lattice model for predicting the rheological behavior of asphalt mixtures was presented.In this model asphalt mixtures were described as a two-phase composite material consisting of asphalt sand and coarse aggregates distributed randomly.Asphalt sand was regarded as a viscoelastic material and aggregates as an elastic material.The rheological response of asphalt mixture subjected to different constant stresses was simulated.The calibrated overall creep strain shows a good approximation to experimental results.展开更多
Low temperature cracking has become one of the important factors that diminish asphalt pavement's ride quality and service life.Especially in cold region,cracking caused by low temperature is the main distress for...Low temperature cracking has become one of the important factors that diminish asphalt pavement's ride quality and service life.Especially in cold region,cracking caused by low temperature is the main distress form.This paper discussed the effect of aggregate gradation on the low temperature performance in asphalt paving mixtures.A total of 11 asphalt mixtures with 11 different aggregate gradations and one asphalt binder content were studied.Volumetric properties of the coarse aggregate and asphalt mixtures showed aggregate grading has a significant impact on the degree of aggregate interlock in asphalt mixtures.A trend is existed in the low temperature performance with the change of gradation.With the aid of mathematic statistics,it indicates gradation affects the low temperature performance significantly.The findings also indicate the relationship between the degree of aggregate interlock in asphalt mixtures and the low temperature performance:With the stone-to-stone contact developed,the mixture has a high energy to resist contract and deformation at low temperature.The properties of fine aggregate and asphalt play an important part in resisting low temperature cracking in floating structure.But it provides lower energy to resist low temperature cracking compared to the skeleton structure.展开更多
Small stone asphalt mixture(SSAM) was designed by Bailey method and coarse aggregate voids-filling method.The optimum asphalt content was determined by Marshal test.Surface texture depth for SSAM with different void...Small stone asphalt mixture(SSAM) was designed by Bailey method and coarse aggregate voids-filling method.The optimum asphalt content was determined by Marshal test.Surface texture depth for SSAM with different voidage,and the BPN of SSAM and SMA before after wet track abrasion were measured.The experimental results indicate that the surface texture depth increases with the decreasing of asphalt aggregate ratio.The SSAM with the optimal asphalt content has a good skid resistance.BPN of asphalt mixture decreases with the increasing of wearing time,but the extent of reduction is different.The reduction rate of BPN for SSAM is smaller than that of SMA,indicating that SSAM has a good skid resistance attenuation capacity.Finally,the other properties of SSAM are also evaluated,showing that the splitting strength and modulus and SSAM are higher than those of SMA,and the other properties of SSAM,such as high-temperature performance and water stability can also satisfy the technical requirements.展开更多
Asphalt mixtures exhibit strong viscous properties under repetitive loads. This phenomenon can be simulated in creep and recovery tests. By applying the visco elastoplastic model proposed, data recorded in the tests ...Asphalt mixtures exhibit strong viscous properties under repetitive loads. This phenomenon can be simulated in creep and recovery tests. By applying the visco elastoplastic model proposed, data recorded in the tests are interpreted. It is emphasised that applicability of the visco elastoplastic model depends on the proper method of characterising parameters involved in the constitutive equations. Since two or more strain components of elasticity and viscosity coexist during the loading or unloading, a measuring system of two loggers is introduced to decouple these components. Test data are analysed in three steps as elastic, visco elastic and visco plastic evaluations, using the records collected at the moment of unloading, during the periods of recovery and creep respectively. Factors that may influence the accuracy of data analysis are also discussed.展开更多
In order to analyze the microstructure of salt anti-freezing asphalt concrete, i e, MFL(Mafilon) modified asphalt concrete, MIP(mercury intrusion porosity) method was used to obtain the data including porosity and...In order to analyze the microstructure of salt anti-freezing asphalt concrete, i e, MFL(Mafilon) modified asphalt concrete, MIP(mercury intrusion porosity) method was used to obtain the data including porosity and pore size distribution in micro scale. Results show that the porosity grows up with the increase of immersion duration and the salt content. During the immersion, the amount of large pores(60-200 μm) grow up gradually and porosity also grows up correspondingly. Even with different immersion duration, most pores' size distribute is beyond 7000 nm.展开更多
In order to verify the validity of finite element numerical simulation method for asphalt mixture, which consists of aggregates, mastic (where mastic is a kind of fine mixture composed of asphalt binder mixed with fin...In order to verify the validity of finite element numerical simulation method for asphalt mixture, which consists of aggregates, mastic (where mastic is a kind of fine mixture composed of asphalt binder mixed with fines and fine aggregates) and air voids, based on three-dimensional (3D) heterogeneous specimen, X-ray computerized tomography (X-ray CT) was used to scan the asphalt specimens to obtain the real internal microstructures of asphalt mixture. CT images were reconstructed to build up 3D digital specimen, and the viscoelastic properties of mastic were described with Burgers model. The uniaxial creep numerical simulations of three different levels of aggregate gradation were conducted. The simulation results agree well with the experimental results. The numerical simulation of asphalt mixture incorporated with real 3D microstructure based on finite element method is a promising application to conduct research of asphalt concrete. Additionally, this method can increase the mechanistic understanding of global viscoelastic properties of asphalt mixtures by linking the real 3D microstructure.展开更多
基金Funded by the National Natural Science Foundation of China(No.11962024)Key Technology Project of Inner Mongolia Autonomous Region(No.2019GG031)。
文摘The objective of this paper was to study low temperature crack resistance mechanism of steel slag asphalt mixture(SAM).Thermal stress restrained specimen test(TSRST)and three-point bending test were carried out to evaluate the low-temperature crack resistance of SAM and basalt asphalt mixture(BAM).Based on the digital image correlation technique(DIC),the strain field distribution and crack propagation of SAM were analyzed from the microscopic point of view,and a new index,crack length factor(C),was proposed to evaluate the crack resistance of the asphalt mixture.The crystal phase composition and microstructure of steel slag aggregate(SA)and basalt aggregate(BA)were studied by X-ray diffraction(XRD)and scanning electron microscopy(SEM)to explore the low-temperature crack resistance mechanism of SAM.Results show that the low-temperature crack resistance of SAM is better than that of BAM;SAM has good integrity and persistent elastic deformation,and its bending failure mode is a hysteretic quasi-brittle failure;The SA surface is evenly distributed with pores and has surface roughness.SA has the composition phase of alkaline aggregate-calcite(CaCO3),so it has good adhesion to asphalt,which reveals the mechanism of excellent low-temperature crack resistance of SAM.
基金supported by National Natural Science Fund for Excellent Young Scientists Fund Program (Overseas) (Grant No.22FAA02811)Pearl River Talent Plan for the Introduction of High-level Talents (Young Top-notch Talents) (Grant No.2021QN02G744)+1 种基金National Natural Science Foundation of China (Grant No.52178426)the Fundamental Research Funds for the Central Universities (Grant No.SCUT 2022ZYGXZR066 and 2023ZYGXZR001).
文摘The application of reclaimed asphalt pavement(RAP)and reclaimed asphalt shingles(RAS)on asphalt pavement can reduce the asphalt paving cost,conserve energy and protect the environment.However,the use of high contents of RAP and RAS in asphalt pavement may lead to durability issues,especially the fatigue cracking and thermal cracking.It is necessary to conduct a series of analyses on asphalt mixtures containing high RAP and RAS,and seek methods to enhance their long-term performance.This paper provides a comprehensive over-view of the long-term performance of recycled asphalt mixtures containing high contents of RAP and RAS.The findings in this research show that rutting resistance of high recycled asphalt mixtures is not a concern,whereas their resistance to fatigue and thermal cracking is not conclusive.Recycling agents can be used to improve the thermal cracking resistance of high recycled asphalt mixtures.An optimum decision on recycling agents will improve the durability properties of high recycled asphalt mixtures.It is recommended that to use a balanced mixture design approach with testing of the blended asphalt binders will provide better understanding of long-term performance of recycled asphalt mixtures containing high RAP and RAS.
基金This manuscript is supported by the National Natural Science Foundation of China(Grant numbers:52108398,52225806,52078063)the Open Fund of Key Laboratory of Special Environment Road Engineering of Hunan Province(kfj210502).
文摘This study normalized the mixture's fatigue behavior at various temperatures,and the strength and fatigue tests of the mixture were conducted.The stress state of the asphalt mixture includes direct tensile,uniaxial compression,and indirect tensile.The Desai yield surface and fatigue path were proposed.And a normalized fatigue characteristics model of the mixture was established.The following conclusions were obtained.With the increases in the loading rate,the strength of the asphalt mixture increased.As the temperature increases,the strength of the mixture is reduced.At various temperatures and rates,the strength forms a closed curved surface.The Desai strength yield surface was established,which forms a closed curved surface.When the loading rate and temperature are below a certain critical line,the asphalt mixture will not undergo strength damage.At a fixed stress state,the fatigue damage path of the mixture was determined.The stress ratio was determined considering the influence of the loading rate.In this way,a normalized model can be described to express the asphalt mixture fatigue properties at various temperatures and stress levels.For the asphalt mixture in an indirect tensile state,the normalized fatigue equation parameter is 4.09.This model is more suitable for reflecting the viscous-elastic behavior of the mixtures than the fatigue equation determined by the notional stress ratio.
基金The authors acknowledge the financial support from the National Natural Science Foundation of China(No.51968006).
文摘Although there are many kinds of fracture tests to choose from in evaluating the crack resistance of asphalt mixture,the semi-circular bending(SCB)test has attracted a lot of attention in the academic road engineering community because of its simplicity,stability,and flexibility in testing and evaluation.The SCB test has become a common method to study the cracking resistance of asphalt mixture in recent years.This paper mainly summarizes the overview of the SCB test,summarizes some research results and common characterization parameters of the SCB test method in monotone test and fatigue test in recent years,and predicts and suggests the research direction of the SCB test in the future.It is found that the research on the monotonic SCB test is more comprehensive,and the research on the SCB fatigue test needs to be further improved in the aspects of loading mode,characterization parameter selection,and so on.Researchers can flexibly adjust the geometric dimensions and the test parameters of semi-cylindrical specimens,and conduct comprehensive analysis combined with the results of numerical simulation.The crack resistance of asphalt mixture can be comprehensively evaluated by fracture energy,fracture toughness,stiffness,flexibility index and other fracture indicators,combined with the crack propagation of the specimen.The analysis of numerical simulation can confirm the test results.In order to standardize the setting of fatigue parameters for future application,it is necessary to standardize the setting of bending performance.
基金Funded by the Key Research and Development Projects in Shaanxi Province(No.2022SF-328)Science and Technology Project of Shaanxi Department of Transportation(Nos.19-10K,19-28K)Science and Technology Project of Henan Department of Transportation(No.2020J-2-3)。
文摘In order to comprehensively utilize the remaining bamboo residue of bamboo products,this paper presents a research on recycling the bamboo fibers from bamboo residue for improving the performance of the asphalt mixtures.First of all,the basic performance parameters of sinocalamus affinis fiber,phyllostachys pubescens fiber,green bamboo fiber were tested and analyzed,and the optimal content and length were put forward.Then,the mix ratio design of the bamboo fiber modified asphalt mixture was further designed through the response surface method,and was verified the rationality of the mix ratio.Finally,the mixture specimens were made according to the experimental design mix ratio,and the high temperature,low temperature performance and moisture susceptibility of the bamboo fiber modified mixtures asphalt were tested.The results showed that the high temperature performance,low temperature performance and moisture susceptibility of bamboo fiber modified asphalt mixtures were improved compared with the performance of SBS modified asphalt mixture.When the length of bamboo fiber is 7.25 mm and the content of 0.22%,the road performance of the asphalt mixture was optimal.Consequentially,the decomposition of bamboo residue into bamboo fiber and its application in asphalt pavement can improve the reuse of bamboo waste,with remarkable environmental benefits and great promotion value.
基金This work was financially by the Self-Financing Technology Plan Project of Foshan(2020001005386).
文摘For evaluating the water stability of hot-mixed renewable asphalt mixture(HRM),the traditional methods are all tested under still water conditions.Except for damage in still water conditions,the hydrodynamic pore pressure generated by the tire driving on the surface water has a great impact.Thus,the RAP contents of the HRMs were designed at 0%,30%,45%and 60%with AC-25 gradation.Then,the self-designed evaluation methods of water stability and dynamic modulus were studied.Finally,the mechanism of the influence of hydrodynamic pore pressure damage on HRMs was studied.The results show that the water stability of HRM containing 30%RAP is equivalent to that of 45%RAP,and the water stability of HRM containing 60%RAP decreases significantly.The Contabro test after MIST treatment can be used as an evaluation method for hydrodynamic pore pressure damage on HRM.Low-speed,heavy-load traffic and larger RAP content have greater damage to the mixture after hydrodynamic pore pressure damage.The performance differences between the aged bitumen and pure bitumen,as well as the aged minerals and new minerals,are continuing to be enlarged in hydrodynamic pore pressure conditions,finally affecting the water stability and dynamic modulus of the HRMs.
文摘As a byproduct of the steelmaking process,significant amounts of hazardous electric arc furnace dust(EAFD)are produced.Utilizing the solidification/stabilization technology with asphalt mix is one way to safeguard the environment from its negative effects.Rutting was used as an indicator to assess the asphalt mixture with EAFD since it is an important factor in pavement design.This study’s major goal is to ascertain how EAFD affects the rutting of asphalt-concrete mixtures.To evaluate the ideal asphalt content,the Marshall test method was applied to asphalt-concrete mixtures.EAFD was added to the asphalt cement in four different volume percentages as a binder addition.Then,using the Universal Testing Machine,participants were exposed to a replica of the rutting test(UTM).Experiments were conducted at 25℃,40℃ and 55℃,and at frequencies of 1 Hz,4 Hz and 8 Hz.Rutting was measured for each specimen.Test results showed that rut depth has a negative correlation with EAFD%and a positive correlation with temperature.The use of EAFD has dual advantages,protecting the environment from the adverse impact of EAFD and reducing the cost of asphalt mix without jeopardizing pavement performance.
基金Fund by Collaborative Innovation Center of Water Conservancy&Transportation Infrastructure Safety,Henan Province,China Postdoctoral Science Fund(No.20110491008)Science and Technology Planning Project of Department of Transportation of Henan Province(No.2013-2-12)The State Key Laboratory Open Fund of Harbor,Coastal and Offshore Engineering(No.LP1113)
文摘The fatigue property of asphalt mixtures under complicated environment (low-temperature bending performance, chloride penetration, freezing-thawing cycle and their coupling effect) and the improvement effect for relevant property of basalt fiber-reinforcing asphalt mixture under complicated environment are studied. Two grading types of asphalt mixtures, AC-16I and AC-13I, are chosen, whose optimum asphalt-aggregate ratio and optimum dosage of basalt fiber are determined by the Marshall test. The standard specimens are made firstly, and then the low temperature bending tests of asphalt mixture and basalt fiber-reinforced asphalt mixture under the coupling effect of the chloride erosion and freezing-thawing cycle have been carried out. Finally, the fatigue property tests of asphalt mixture and basalt fiber-reinforced asphalt mixture under complex environment are performed on MTS material testing system. The results indicate that the tensile strength, the maximum curving tensile stress, the curving stiffness modulus, and fatigue properties of asphalt mixture are influenced by the coupling effect of the chloride erosion and freezing-thawing cycle. The low-temperature bending performance and fatigue property of asphalt mixtures under complicated environment can be greatly improved by adding moderate basalt fiber. The dense gradation asphalt mixture possesses stronger ability to resist adverse environmental effects under the same condition.
基金the Education Ministry for the New Century Excellent Talents Project(NCEF-05-0656)
文摘The dynamic characteristics of fiber-modified asphalt mixture were investigated. Cellulose fiber, polyester fiber and mineral fiber were used as additives for asphalt mixture, and the dosage was 0.3%, 0.3%, 0.4%, respectively. Dynamic modulus test using SuperPave simple performance tester (SPT) was conducted to study the dynamic modulus (E') and phase angle (δ) for the control asphalt mixture and fiber-modified ones at various temperatures and frequencies. Experimental results show that all fiber-modified asphalt mixtures have higher dynamic modulus compared with control mixture. The dynamic modulus master curves of each type of asphalt mixtures are determined based on nonlinear least square regression in accordance with the time- temperature superposition theory at a control temperature (21.1℃). The fatigue parameter E^*×sinδ and rutting parameter E^*/sinδ of asphalt mixture are adopted to study the fatigue and rutting-resistance properties, and experimental results indicate that such properties can be improved by fiber additives.
文摘Design method for large stone porous asphalt mixtures (LSPM) was analyzed to avoid the early distresses of semi-rigid asphalt pavements. Based on stone-to-stone skeleton structure concept, processes of LSPM gradation design was given. The gradation composite design for LSPM shows that the LSPM nominal maximum size ( N MS) should be larger than 26.5 mm, and the NMS sieve passing percentage should be greater than 50%. Through experiments and calculations on the volume properties of the aggregate, the range of aggregate gradation curve of LSPM was given. In terms of asphalt binder's normalized test results, MAC-70 and SBS modified asphalt were selected as the asphalt binders. The applicability of large scale Marshall Method and gyratory compaction method to shape specimens was investigated. Based on the asphalt mixture performance evaluation, the optimum asphalt content range (3.1%-3.6%), the bitumen film's thickness range (13-16 μm) and the air void range (13%-18 %) were recommended. Finally, LSPM was tested by the laboratory performance tests including rutting resistance test, fatigue test and water stability test. The theoretic and practical analysis shows that LSPM has a good performance on water permeability, rutting resistance and reflection crack resistance.
基金Funded by the National Natural Science Foundation of China(No.51108081)
文摘A micromechanical model based on discrete element method(DEM) was employed to investigate the effects of aggregate size and specimen scale on the cracking behavior of asphalt mixture. An algorithm for generating three-dimensional aggregates that can reflect the realistic geometry such as shape, size and fracture surface of aggregate particles was developed using a user-defined procedure coded with FISH language in particle flow code in three-dimensions(PFC3 D). The parallel-bond model(PBM), linear contact model(LCM), and slip model(SM), whose sets of micro parameters were obtained by comparing experimental tests with numerical simulation results, were used to characterize the internal contact behavior of asphalt mixture. Digital asphalt mixture specimens were used to simulate the effects of aggregate size and specimen scale on the cracking behavior by the indirect tensile(IDT) test. Some conclusions can be drawn as follows: Both cracks and IDT strength decrease with increasing aggregate size. However, the heterogeneity of contact-force distribution augments with increasing aggregate size, especially with 13.2-16 mm aggregate. The aggregate size of 4.75-9.5 mm dominates in forming skeleton structure for asphalt mixture. The IDT strength decreases and cracks augment with increasing sample scale. The crack growth can be well interpreted from the perspective of energy analysis. The conclusions show that the proposed micromechanical model is suitable for the simulation of crack propagation. This study provides an assistant tool to further study the cracking behavior of particle-reinforced composites material such as asphalt mixture and Portland cement concrete.
基金Funded by the Science and Technology Program of Communications Department of Henan Province (No.200612)
文摘By using the falling weight deflectometer(FWD),the dynamic loading tests on different thickness of asphalt mixture pavement in different temperature were performed.The experimental results show that the effects of temperature on dynamic properties of asphalt mixture are significant,and the thickness of asphalt mixture is also another important influence factor.The comparisons indicate that effect of temperature on the behaviors of dynamic loading properties and static loading properties of asphalt mixture were quite different.
基金Funded by the Science and Technology Program of Communications Depart-ment of Henan Province(No.2006P335)
文摘In order to study the effects of loading condition and temperature on the dynamic properties of asphalt mixtures, the dynamic loading tests on different loading condition (various speeds and loads under a certain roughness) and temperature conditions were performed. The experimental result show that the dynamic properties of asphalt mixtures are influenced by vehicle load and speed, besides, the effects of temperature on dynamic properties of asphalt mixture are significant.
基金Funded by the National Natural Science Foundation of China (No.50878054)
文摘On basis of the Burgers model, a new model consisting of modified dashpot and Van Der Poel model was derived from rheological and viscoelastic theory. Subsequently, triaxial repeated load permanent deformation tests of AC16 asphalt mixtures were conducted to validate this new developed model. Parameters of new developed model were obtained by a nonlinear regression analysis of test data, and then permanent strains and flow number of each mixture were calculated. The experimental results prove that the new developed model can well describe three phases permanent deformation of asphalt mixture under repeated load and it can be used for pavement mechanical analysis and rutting prediction.
基金Project(10672063) supported by the National Natural Science Foundation of China
文摘A three-dimensional(3D) lattice model for predicting the rheological behavior of asphalt mixtures was presented.In this model asphalt mixtures were described as a two-phase composite material consisting of asphalt sand and coarse aggregates distributed randomly.Asphalt sand was regarded as a viscoelastic material and aggregates as an elastic material.The rheological response of asphalt mixture subjected to different constant stresses was simulated.The calibrated overall creep strain shows a good approximation to experimental results.
基金Sponsored by the National Natural Science Foundation of China(Grant No.50778057)the Research Fund for the Doctoral Program of Higher Education(Grant No.20060213002)
文摘Low temperature cracking has become one of the important factors that diminish asphalt pavement's ride quality and service life.Especially in cold region,cracking caused by low temperature is the main distress form.This paper discussed the effect of aggregate gradation on the low temperature performance in asphalt paving mixtures.A total of 11 asphalt mixtures with 11 different aggregate gradations and one asphalt binder content were studied.Volumetric properties of the coarse aggregate and asphalt mixtures showed aggregate grading has a significant impact on the degree of aggregate interlock in asphalt mixtures.A trend is existed in the low temperature performance with the change of gradation.With the aid of mathematic statistics,it indicates gradation affects the low temperature performance significantly.The findings also indicate the relationship between the degree of aggregate interlock in asphalt mixtures and the low temperature performance:With the stone-to-stone contact developed,the mixture has a high energy to resist contract and deformation at low temperature.The properties of fine aggregate and asphalt play an important part in resisting low temperature cracking in floating structure.But it provides lower energy to resist low temperature cracking compared to the skeleton structure.
基金Funded by the Program for Innovative Research Team in University (IRT1050)the Ministry of Transport Technology Project(201131982020)the Key Program of Shaanxi Natural Science Foundation for Basic Research Plan (2010JZ009)
文摘Small stone asphalt mixture(SSAM) was designed by Bailey method and coarse aggregate voids-filling method.The optimum asphalt content was determined by Marshal test.Surface texture depth for SSAM with different voidage,and the BPN of SSAM and SMA before after wet track abrasion were measured.The experimental results indicate that the surface texture depth increases with the decreasing of asphalt aggregate ratio.The SSAM with the optimal asphalt content has a good skid resistance.BPN of asphalt mixture decreases with the increasing of wearing time,but the extent of reduction is different.The reduction rate of BPN for SSAM is smaller than that of SMA,indicating that SSAM has a good skid resistance attenuation capacity.Finally,the other properties of SSAM are also evaluated,showing that the splitting strength and modulus and SSAM are higher than those of SMA,and the other properties of SSAM,such as high-temperature performance and water stability can also satisfy the technical requirements.
文摘Asphalt mixtures exhibit strong viscous properties under repetitive loads. This phenomenon can be simulated in creep and recovery tests. By applying the visco elastoplastic model proposed, data recorded in the tests are interpreted. It is emphasised that applicability of the visco elastoplastic model depends on the proper method of characterising parameters involved in the constitutive equations. Since two or more strain components of elasticity and viscosity coexist during the loading or unloading, a measuring system of two loggers is introduced to decouple these components. Test data are analysed in three steps as elastic, visco elastic and visco plastic evaluations, using the records collected at the moment of unloading, during the periods of recovery and creep respectively. Factors that may influence the accuracy of data analysis are also discussed.
基金Funded by the National Natural Science Foundation of China(No.51578290)
文摘In order to analyze the microstructure of salt anti-freezing asphalt concrete, i e, MFL(Mafilon) modified asphalt concrete, MIP(mercury intrusion porosity) method was used to obtain the data including porosity and pore size distribution in micro scale. Results show that the porosity grows up with the increase of immersion duration and the salt content. During the immersion, the amount of large pores(60-200 μm) grow up gradually and porosity also grows up correspondingly. Even with different immersion duration, most pores' size distribute is beyond 7000 nm.
基金Project(51038004) supported by the National Natural Science Foundation of China
文摘In order to verify the validity of finite element numerical simulation method for asphalt mixture, which consists of aggregates, mastic (where mastic is a kind of fine mixture composed of asphalt binder mixed with fines and fine aggregates) and air voids, based on three-dimensional (3D) heterogeneous specimen, X-ray computerized tomography (X-ray CT) was used to scan the asphalt specimens to obtain the real internal microstructures of asphalt mixture. CT images were reconstructed to build up 3D digital specimen, and the viscoelastic properties of mastic were described with Burgers model. The uniaxial creep numerical simulations of three different levels of aggregate gradation were conducted. The simulation results agree well with the experimental results. The numerical simulation of asphalt mixture incorporated with real 3D microstructure based on finite element method is a promising application to conduct research of asphalt concrete. Additionally, this method can increase the mechanistic understanding of global viscoelastic properties of asphalt mixtures by linking the real 3D microstructure.