Durability Of Asphalt Pavement Research Articles

Effect of tack coat dosage and temperature on the interface shear properties of asphalt layers bonded with emulsified asphalt binders

The shear strength of the interface of asphalt concrete structure has a great influence on the mechanical properties and durability of asphalt pavement. This paper describes the experimental design and analysis of the shear properties of the interface between asphalt layers. A self-designed device was employed to measure the direct shear strength of the interface with the aid of the Universal Test Machine (UTM-100). The effect of temperature, dosage of tack coat and type of tack coat on the shear properties of the interface were studied through laboratory testing. Two types of emulsified asphalt binders, namely PC-3 and HV, were selected as the tack coats. The property was evaluated in three tack coat dosages (0.25Kg/m2, 0.5Kg/m2 and 0.75Kg/m2 based on residual binder) and at four test temperatures (−10°C, 0°C, 25°C and 50°C). Hence, a total number of 72 composite specimens made of AC-13 and AC-20 were subjected to the shear test to evaluate the interface shear characteristics in terms of interface shear strength, the shear failure displacement and the coefficient of interface bonding at the initial stage of shear. The results showed that the shear strength at the interface decreases gradually with increasing temperature. The least failure shear displacement of all specimens was observed at the highest temperature of 50°C. Moreover, the results indicated that the brittleness at low temperatures, the flowability at intermediate temperatures, and the viscosity at high temperatures of tack binder have the most significant effects on the shear property of the interface of asphalt pavement.

Effect of freezing-thawing and ageing on thermal characteristics and mechanical properties of conductive asphalt concrete

Conductive asphalt concrete with graphite can improve the workability of asphalt solar collector (ASC), which provides an interesting method to mitigate a series of realistic problems related to asphalt pavement. The freezing-thawing cycles and ageing of asphalt material are recognized as critical factors that could affect the durability of asphalt pavement. In this paper, the influences of freezing-thawing and ageing on mechanical properties and thermal characteristics of conductive asphalt concrete (CAC) were experimentally investigated. Control asphalt concrete samples were prepared by the same aggregate gradation and volume composition with CAC. The thermal properties of asphalt concrete were studied by Thermal Constants Analyzer. Experimental results indicated that freezing-thawing effect would lead to volume expansion and strength degradation of CAC samples. During the freezing-thawing test, the thermal conductivity and specific heat of CAC tend to decrease while the thermal diffusivity increased correspondingly. Although ageing process would degrade the moisture resistance, low temperature and fatigue properties of conductive asphalt concrete, there was no significant differences in thermal conductivity, thermal diffusivity and specific heat between the original and aged samples. Compared to control asphalt concrete, the incorporation of graphite improved the anti-ageing properties of conductive asphalt concrete.

Effects of environmental aging and ultra violet radiation on asphalt mixture dynamic modulus, permanent deformation and fatigue life

The aging process causes changes in the properties of asphalt mixtures, such as weak adhesion of mineral aggregates to the asphalt and increase of asphalt’s rigidity and viscosity, which in turn directly affect the durability of asphalt pavement. This study aims to evaluate the behavior of asphalt mixtures at different aging stages through the comparison of samples treated under ultraviolet radiation and samples extracted from the field. Laboratory mixtures were prepared from one aggregate source and one asphalt cement. Four types of asphalt mixtures were analyzed: un-aged, laboratory-aged - UV and Pressure Aging Vessel, and field-aged. For laboratory accelerated aging a UV radiation chamber was designed and samples were exposed to 100, 200 and 500-hour treatment periods. Samples aged in the field were obtained from in-service pavements of 1.5 to 11 years after construction. Mechanical behavior was evaluated through dynamic modulus, rutting and trapezoidal fatigue. Results showed that when aging time increases all samples undergone significant increases in dynamic moduli up to two times of unaged mixtures. Permanent deformation exhibited better resistance in aged mixtures than the unaged ones. On the other side, aging affected negatively fatigue life due to significant changes in the slope of fatigue law. Accelerated aging by UV chamber simulated up to 1.5 years in fatigue life and 11 years in permanent deformation performance.

Effect of using Fibre on the Durability of Asphalt Pavement

Using the fibre additives with a uniform distribution in asphaltic concrete mixture is a well-known technique for improving the mechanical properties and durability of asphalt pavement. The purpose of this study is to investigate the effect of preparing fibre and production of the properties of bitumen and asphalt concrete mixture. In this study, a dense-graded aggregation, mineral fibres (asbestos) and synthetic fibres (polyester and nylon) were used. Laboratory studies were done by comparing different rheological properties, mechanical and moisture susceptibility of mixtures of fibres. Results of the penetration and softening point on mixtures of bitumen – fibre show that fibres improve the mixed rheological properties and stiffening effect of fibre properties. The results of Marshall Tests indicate that adding fibres reduces the strength in Marshall and results in the slight increase in the percentage of optimum bitumen content and asphalt percentage of air voids in comparison with typical fibre. The results of the indirect tensile tests showed that the addition of fibres, depending on the percentage of fibres significantly improves the durability of the mixture.

Asfalty modyfikowane chemicznie o poprawionej adhezji do kruszywa

Durability of asphalt pavements is dependent on the use of high-quality road binders. Good bitumen should exhibit adequate viscoelastic properties, resistance to ageing and good adhesion to mineral aggregates. In order to improve bitumen properties the modification of binder is used. For over 15 years, mainly in the USA, polyphosphoric (PPA) modifier is used, which improves viscoelastic properties of the binder and its adhesion to aggregate. The paper presents the extensive research results of adhesion of binders modified with polyphosphoric additive and SBS polymer, as well as the research results of water resistance of asphalt mixtures comprising these binders. In order to evaluate the adhesion test results a new computer image analysis, developed by the author at Warsaw University of Technology, was used. Computer analysis may constitute an alternative to inaccurate visual method. It is shown that there is a possibility to significantly improve binder adhesion to the aggregate as a result of bitumen modification with both SBS polymer and polyphosphoric (PPA) additive.

Rheological Evaluation of Ageing Properties of SEBS Polymer Modified Bitumens

Ageing of bitumen is an important cause of reduced durability of asphalt pavements. Therefore, the polymer modified bitumens are recommended to increase the durability of the material. In the present work, rheology has been applied to evaluate the properties of Styrene-Ethylene- Butadiene -Styrene (SEBS) polymer modified bitumen (PMB) to compare to the 35 / 50 penetration grade bitumen, before and after ageing. The effects of ageing on the physical and rheological properties of (PMB) were evaluated using SARA analysis, penetration test, softening point test and dynamic shear rheometer test (DSR). The binders were aged by Rolling Thin Film Over Test (RTFOT) and Pressure Ageing Vessel (PAV). The results showed that use of SEBS polymer reduces the ageing effect on physical and rheological properties of the bitumen binder as illustrated through lower ageing index of complex modulus and an increase in tang δ indicating that the SEBS polymer improve the ageing resistance of bitumen binder.

Rheological characteristics of unaged and aged epoxidised natural rubber modified asphalt

Durable pavement with long service life and low maintenance and rehabilitation costs are preferred; hence, the demand for high-quality asphalt is growing. This situation has led to the research and development of new materials with increased performance, such as polymer-modified asphalt (PMA). This study was conducted to investigate the use of epoxidised natural rubber (ENR) mixed with asphalt, both unaged and aged. The physical and rheological properties of base asphalt and ENR-modified asphalt (ENRMAs) were measured. Fundamental parameters were used to describe the significant benefits of ENR as a modifier. However, it was observed that the rheological properties differ considerably between the base asphalt and ENRMAs. The rheological parameters of complex modulus and phase angle indicate that the presence of ENR increases the stiffness and elasticity behaviour of the binder, particularly at high temperatures. For the aged binders, the dynamic mechanical analysis of the effect of ageing on the rheological performance of the binders indicated that there is a considerable difference in behaviour between the base asphalt and PMAs. Based on the dynamic mechanical analysis of the binders, it can be concluded that the asphalt component of the modified binders ages in a manner similar to that of the base asphalt. However, the rheological changes that occur after ageing differ from the base asphalt in regions where the polymer is the dominant component. Finally based on the physical and rheological tests, it can be concluded that ENR can increase the durability of asphalt pavements.

Performance of Modified Asphalt Binder with Tire Rubber Powder

The two major distresses associated with flexible pavement are rutting deformation and fatigue cracking in world highways. This is mainly because of the increasing load and higher tire pressure of vehicles which are applied to highway pavements today. At the same time, the asphalt containing neat binders does not always performed as expected. As a consequence, these distresses reduce the design life of the pavement and increase the maintenance costs tremendously. Therefore, in order to minimize the distresses and increase the durability of asphalt pavement, there is need to improve the performance properties of neat asphalt binders. Many researchers reported that using different types of polymer to modify the asphalt binder could be a solution to minimize the distresses occurred in asphalt pavement and improve the overall performance of the pavement. Disposal of waste tires is a serious environmental concern in many countries. Several attempts were made in the past to modify asphalt binder using tire rubber powder to improve the performance of neat asphalt binders. It is believed that the use of Tire Rubber Powder (TRP) as an additive in the modification of asphalt binder can improve the binder performance properties, increase the durability of the pavement, and reduces the waste disposal problem. This study aims to review the previous studies conducted on the use of tire rubber powder in the modification of asphalt binder. It was observed that addition of tire rubber powder to the asphalt binder enhances the properties of modified binder. It was found that an increase in the percentage of tire rubber powder causes an increase in rutting factor (G*/sinδ) and decrease in fatigue factor (G*sinδ) indicating higher resistance against rutting and fatigue cracking. In addition, the use of tire rubber powder to modify asphalt binder is considered as a solution to enhance environmental and economic sustainability of pavements.

Moisture damage assessment using surface energy, bitumen stripping and the SATS moisture conditioning procedure

Durability is one of the most important properties of an asphalt mixture. A key factor affecting the durability of asphalt pavements is moisture damage. Moisture damage generally results in the loss of strength of the mixture due to two main mechanisms; the loss of adhesion between bitumen and aggregate and the loss of cohesion within the mixture. Conventional test methods for evaluating moisture damage include tests conducted on loose bitumen-coated aggregates and those conducted on compacted asphalt mixtures. The former test methods are simpler and less expensive to conduct but are qualitative/subjective in nature and do not consider cohesive failure while the latter, though more quantitative, are based on bulky mechanical test set-ups and therefore require expensive equipment. Both test methods are, however, empirical in nature thus requiring extensive experience to interpret/use their results. The rolling bottle test (RBT) (EN 12697-11) for loose aggregate mixtures and the saturation ageing tensile stiffness (SATS) test (EN 12697-45) for compacted asphalt mixtures are two such methods, which experience suggests, could clearly discriminate between ‘good’ and ‘poor’ performing mixtures in the laboratory. A more fundamental approach based on surface energy (SE) measurements offers promise to better understand moisture damage. This article looks at results from the rolling bottle and the SATS tests in an attempt to better understand the underlying processes and mechanisms of moisture damage with the help of SE measurements on the constituent bitumen and aggregates. For this work, a set of bitumens and typical acidic and basic aggregate types (granite and limestone) were selected. Combinations of these materials were assessed using both the rolling bottle and SATS tests. The SE properties of the binders were measured using a dynamic contact angle Analyser and those of the aggregates using a dynamic vapour sorption device. From these SE measurements it was possible to predict the relative performance of both the simple RBT and the more complicated SATS test. Mineralogical composition of the aggregates determined using a mineral liberation analyser was used to explain the differences in performance of the mixtures considered.

高速道路におけるアスファルト舗装の「解体新書」プロジェクト

This project is launched to identify the specific deterioration of asphalt pavement, and detect the real cause of each damage occurred in field. The study was conducted with comparison of in-situ status in damaged and non-damaged sections after almost twenty years under traffics. Specimens for lab tests were taken by block sampling of both asphalt layers and granular subbase course. Based on the field observation of the damaged part and various testing results, several important key factors were found out for long term durability of asphalt pavement. Those points, such as total thickness of asphalt layers, durability of asphalt stabilized (third) layer and bonding property of each layers are vitally important to prevent fatigue cracking. Well graded in good compaction of granular subbase and subgrade are also key issue to support traffics in long period without permanent deformation. Preventing water penetration through the pavement into its base is another important factor to avoid severe deterioration in field. 高速道路の供用年数が伸びるに従い，アスファルト舗装の経年劣化や下層の脆弱化により，路盤からの厚層打換補修を強いられる箇所が近年増加している．このような状況を憂い，供用後約20年を経た高速道路において，補修履歴のない健全部と数度の補修を繰返してきた損傷部を比較する形で，大規模な開削調査を実施した．本プロジェクトは，実道におけるアスファルト舗装の損傷実態の把握と原因の究明を行うものであり，調査の結果，高速道路における疲労ひび割れや永久変形の発生事例が確認され，アスファルト混合物の層間接着や路盤の滞水による脆弱化等，現地の舗装において長期耐久性の鍵を握っているポイントを明らかにした．

Fracture mechanics of idealised bituminous mixes

The durability of asphalt pavements is strongly impaired by cracks, caused primarily by traffic loads and environmental effects. In this work, fracture behaviour of idealised asphalt mixes is investigated. Experiments on idealised asphalt mixes under pure-tension mode (mode I cracking) were performed and fracture parameters were evaluated. In these three-point bend fracture tests, the test variables were temperature and load rate. The test data were stored in an asphalt materials database and special-purpose tools were implemented to analyse and handle the laboratory data automatically. Fracture mechanism maps were constructed, showing the conditions associated with ductile, brittle and ductile–brittle transition regimes of behaviour. The mechanism maps show the failure response of the material in terms of the stress intensity factor, strain energy release rate and J-integral as a function of the temperature-compensated crack mouth opening strain rate. Fracture behaviour of asphalt mix specimens was simulated by cohesive zone model in conjunction with a novel material constitutive model for asphalt mixes. The finite element model agrees well with the experimental results and provides insights into fracture response of the notched asphalt mix beam specimens.

Assessing asphalt mixture moisture susceptibility through intrinsic adhesion, bitumen stripping and mechanical damage

Durability is one of the most important properties of an asphalt mixture. A key factor affecting the durability of asphalt pavements is moisture damage. Moisture damage is generally considered to be the result of two main mechanisms; the loss of adhesion between bitumen and the aggregate and the loss of cohesion within the mixture. Conventional test methods for evaluating moisture damage include tests conducted on loose bitumen-coated aggregates and those conducted on compacted asphalt mixtures. This paper looks at results from the rolling bottle and the saturated ageing tensile stiffness (SATS) tests in an attempt to better understand the underlying processes and mechanisms of moisture damage with the help of surface energy measurements on the constituent bitumen and aggregates. Combinations of materials were assessed using both the rolling bottle and SATS tests. The surface energy properties of the binders were measured using a dynamic contact angle analyser and those of the aggregates using a dynamic vapour sorption device. From these surface energy measurements, it was possible to predict the relative performance of both the simple rolling bottle test and the more complicated SATS test. Mineralogical composition of the aggregates determined using a mineral liberation analyser was used to explain the differences in performance of the mixtures considered.

Evaluation and Validation of Characterization Methods for Fatigue Performance of Asphalt Mixes for Western Australia

The determination of appropriate pavement thickness using laboratory determined parameters is one of the key issues facing the road manager. Five different types of asphalt mixes were produced in laboratory to modify pavement performance mixture. The main objective of this study is to evaluate the characterization methods for fatigue performance of asphalt mixes to Western Australia road. In this study, laboratory test for indirect tensile modulus, dynamic creep, wheel tracking and aggregate gradation tests were taken to analyze each asphalt mixtures for a design traffic road. The results and analysis showed that AC20-75 asphalt mix blow is the most effective and efficient in pavement performance than the other asphalt mixes. AC14-75 was the second in rank to strengthen and durability of asphalt pavement. All asphalt mixes in this study can be used to strength and stable the overall stiffness of pavement, and modification rank can be described as AC20-75 Blow > AC14-75 Blow > AC14-50 Blow > AC7-50 Blow > SMA7-50 Blow in this research.

Analysis of Performance Decay Behavior for Asphalt Pavement Based on Aging

Aging is a main factor affecting the durability of asphalt pavement. To study decay behavior of asphalt pavement with aging, aged asphalt was extracted from stratified pavement mixtures for different service-life. The changes of asphalt properties with service time and depth variations of the pavement were discussed. And numerical simulation analysis of pavement structure was conducted with pavement gradient modulus changes caused by aging. The results indicate that asphalt stiffness increases and low-temperature performance decays sharply with the extension of pavement service life, especially in the first several years. The vertical aging differences from top to bottom of pavement were significant, the aging extents decrease continuously from the surface, which cause the gradient changes of pavement modulus. The maximum tensile stress and maximum shear stress all increase with surface modulus increasing, so more serious aging can induce greater gradient modulus, shear stress and tensile stress are larger under the same loads, which have more serious damage to the pavement structure.

Study on the Durability of Highway Bridge under Heavy Traffic

through the study on durability of highway bridges under heavy traffic,And from the subgrade, subbase and base, asphalt surface layer analysis of the three dimensions of the relation between compactness and durability of asphalt pavement,the article pointed out that the current national norms in the compaction of standards and to propose recommendations for improvement,and made to improve durability of asphalt pavement compaction under the current heavy traffic technical measures.

The Application of Large Particle Size Hot Mix Asphalt Macadam Roadbase Structure in the Maintenance Overhaul Engineering

In recent years because of the growing volume of traffic, axle load and tire unit pressure increases, as well as in rough weather, under the action of the traditional cement stabilized macadam roadbase structure is easy to cause more reflection crack, rutting, pumping the asphalt such as early diseases, seriously affect the service life of pavement, and in the construction process for keeping in good health cycle is long and bring greater side to traffic edge construction of traffic organization pressure. Xiaogan belongs to the area of low winter air temperature and the high summer air temperature, traffic flow, high underground water level, the large size macadam base can reduce pavement cold cracking diseases, improve the pavement anti-rutting ability, so as to improve the durability of asphalt pavement.

Modification of local asphalt with epoxy resin to be used in pavement

The durability of asphalt pavement is greatly influenced by the environmental changes during the year. In this paper, we prepared asphalt modified by mixing asphalt 60/70 with epoxidized natural rubber (ENR) in different percentages (5, 10 and 15%), which was achieved using preformed peracetic acid (aqueous solution 59%) at 60–80°C, then molten cross-linker maleic anhydride (MA) was added to modified asphalt until homogenous blends are achieved. Marshall test was used to evaluate the asphalt pavement performance depending on the curing time and hardener concentration. To measure marshall test, the pervious mixture was stirred with aggregate jop formula mix (JMF) and 40% MA at 150–170°C for 20h and 1600rpm. From the obtained data, it was found that asphalt mixed with 15% of ENR+40% MA achieves a high stability (16,632Newton), air voids of 2.5%, flow of 2.9mm and mineral voids of 14.6%. While, the stability of the unmodified asphalt was (11,500Newton), the flow 3.2mm, the suitable air void value was 3.7% at 5.5% with the same conditions.

Comparative analysis of strains and durability of asphalt pavement of perpetual and standard type

This paper analyses the key strains and fatigue performance of the following types of road pavements using fatigue cracking and subgrade rutting as the evaluation criteria: conventional asphalt pavement and pavement structure with fatigue-resistant layer (as in perpetual pavement concept). Calculations were performed for two wheel speeds: 60 km/h and 5 km/h. The study included a comparison of results obtained for pavements differing in terms of material specifications and structure: reference model built of only elastic layers and two models built of viscoelastic asphalt layers and layers of aggregate cement-treated base (CTB) on soil subgrade. The determinations included strains, deformation and displacements (for which VEROAD software program was used) also the above-mentioned failure criteria determined using the Asphalt Institute equations. For predicting the fatigue life of pavement the lower asphalt layer was assumed to have the modulus value equal to the initial modulus calculated with Van der Poel equation and dynamic moduli calculated as sensitive or insensitive to the wheel speed respectively. The effect of the respective factors on the life of pavement in million standard axles (msa) was assessed, demonstrating that the calculations assuming elastic behaviour of all the pavement layers lead to overestimating the pavement life. Finally, it was found that the wheel speed had a significant effect on the strain and on the fatigue life of pavement.

Increasing asphalt pavements durability through accurate construction: a model for compaction design

The overall quality and durability of asphalt pavements mainly depends on its ‘design’, which generally includes materials selection, mix design, structural (and functional) design. In the ‘design’ phase, less attention is generally given to the definition of the construction procedures, which somehow seem to assume a secondary importance. The selection of the most suitable rollers and their use (number of passes, vibration settings) is rarely defined before the job, and the definitive choice often depends on the contractor's available equipments and on the experience of the staff. This paper presents the result of a full-scale experimental study carried out to test the effects of different compaction procedures on the final degree of compaction of different asphalt mixes. After introducing a new variable able to represent the compaction action carried out by the roller, a relation was identified which allows to preliminary evaluate the degree of compaction of a layer when a compaction procedure is defined.

Moisture Susceptibility and Stripping Resistance of Asphalt Mixtures Modified with Different Synthetic Waxes

Wax modification of asphalt binders represents an actual resource in warm-mix asphalt technology. Despite its benefits in reducing plant temperatures and atmospheric emissions, the presence of wax can be associated with side effects on the quality and durability of asphalt pavements. A simple procedure to evaluate the influence of wax on asphalt stripping resistance and moisture susceptibility is proposed. An unmodified asphalt binder was blended with waxes having different chemical structures (paraffinic and polyamidic); wax-modified asphalt mixtures were then prepared with various aggregate types. Moisture sensitivity was initially studied using conventional methods, such as indirect tensile strength measured after water conditioning. The stripping resistance of bitumen-coated aggregates was then quantitatively evaluated by identifying the stripped surface with a digital image analysis method. In contrast with expectations, results indicated that enhanced performances can be obtained in the presence of wax-modified asphalts. However, the type of wax was found to be decisive. In the same way, results of contact angle and adhesion measurements performed on bitumen–wax blends indicated that changes in asphalt–water affinity occur according to the type and content of wax.