Accelerated Loading Test Research Articles

Spatiotemporal evolution analysis of pavement texture depth on RIOH track using statistical and rescaled range approaches

The spatial and temporal variability of road surface texture with the environment is closely related to the management and maintenance of pavement performance. To understand the spatiotemporal evolution, accelerated loading test was carried out during a four-year period on Research Institute of Highway (RIOH) track. Statistical and rescaled range (R/S) analysis were introduced to analyze the texture depth data collected using an automatic detection vehicle. As a result, even though a high linear correlation, there are significant differences statistically between the two indexes mean profile depth (MPD) and sensor measured texture depth (SMTD). Further, the spatial variability of texture depth, generally between 5% ∼ 15%, does not change obviously with service environments. However, the variation range of texture depth with time is as low as 0.2 mm and as high as 0.75 mm. The climate-loading effect increases the variation range of MPD more than the climate effect. Through R/S analysis, the Hurst exponent of the MPD sequence is<0.5, indicating the evolution of texture depth is an anti-persistent alternating process between increase and decrease. In addition, the average cycle period, representing the past duration of events affecting future trend, is generally<8 months. These studies took some new insights into the evolution behaviors of texture depth, providing the groundwork for estimating and setting texture level.

Long-Term Performance of Recycled Asphalt Pavement with Recycled Engine Oil Bottom Based on Accelerated Loading Test

The practical performance of recycled asphalt obtained from recycled engine oil bottom (REOB) was evaluated by paving a test road of base asphalt and REOB-recycled asphalt mixture in a laboratory, where accelerated loading tests with 700,000 cycles were conducted. During accelerated loading, pavement temperature, layer bottom strain, pavement skid resistance, and rutting were monitored. The performance of pavement core material was tested after loading to analyze the index change of binder and the compaction degree of the mixture. The results show that the long-term anti-rutting ability of REOB-recycled asphalt pavement is approximately 10% higher than that of the base asphalt pavement, although the long-term anti-sliding force and anti-fatigue performance are poor. A developed model of rut with loading time can better predict the development trends of these parameters with loading cycles. The performance test of the pavement material after loading shows that 700,000 cycles can only degrade the performance of the test pavement, not damage it. The recycled asphalt pavement with 7% REOB has basically the same performance as the base asphalt under 700,000 cycles, indicating that REOB-recycled asphalt pavement can ensure basic road performance, while providing economic and environmental advantages. These results provide a reference for the application and form optimization of REOB-recycled asphalt pavement.

Interlaminar Shear Characteristics, Energy Consumption, and Carbon Emissions of Polyurethane Mixtures

The interlaminar shear characteristics of a polyurethane (PU) mixture composite structure, quantitatively calculating its energy consumption and carbon emissions were analyzed in this study. Inclined shear tests were carried out on thirteen structures without interlaminar treatment, and high-temperature water bath accelerated loading tests were conducted on three composite structures; further, the interlaminar shear strength of the tire trace position after the accelerated loading test was tested to analyze the influence of both the high-temperature water bath environment and loading on the structure. In addition, based on the medium repair project of the Qingdao-Yinchuan expressway, the construction log of PU mixture pavement and asphalt pavement was investigated. Combined with the calculation parameters provided by the United Nations Intergovernmental Panel on Climate Change (IPCC), the consumption and carbon emissions of the two types of mixtures were calculated and compared quantitatively. The results showed that the shear strength between layers of asphalt mixtures, PU mixture and asphalt mixture was less than 2 MPa; however, the shear strength between PU mixture–cement-stabilized macadam and PU mixture–PU mixture was greater than 3 MPa. Therefore, it was recommended to spread a 0.4 L/m2 two-component PU adhesive layer as the interlayer treatment scheme for the structure of asphalt mixture-PU mixture and PU mixture-asphalt mixture; the high-temperature water area and accelerated loading had different effects on the interlaminar shear strength of the three structures. The PUM-16 mixture could effectively reduce energy consumption by 88.3 and 87.2%, carbon emissions by 81.1% and 79.1% in comparison to Stone Matrix asphalt with Nominal maximum particle size of 13.2 mm (SMA-13) and Stone Matrix asphalt with Nominal maximum particle size of 19.0 mm (SMA-20). Thus, the PU mixture was confirmed to be an environmentally friendly road pavement material.

Evaluation on Improvement Effect of Different Anti-Stripping Agents on Pavement Performance of Granite-Asphalt Mixture.

There are abundant granite reserves in China, but the adhesion between granite and asphalt is poor, and there are problems such as insufficient water stability, which seriously restrict the application and promotion of granite in asphalt pavement. In order to improve the adhesion between granite and asphalt, as well as the water stability of asphalt mixture, amines and polymers were selected as anti-stripping agents. First, silane coupling agent modified asphalt (SCAMA), rock asphalt modified asphalt (RMA), SBS modified asphalt (SBS), and double rock composite modified asphalt (SCA&RMA) were produced; the modification effect of different anti-stripping modified asphalts was evaluated. Then, the adhesion of different types of asphalts and granite aggregates before and after aging was evaluated by time-delayed water immersion method. Finally, AC-10 and AC-16 granite–asphalt mixtures were designed, through indoor performance test and 1/3 scale accelerated loading test, evaluating the improvement effect of granite–asphalt mixture on pavement performance. The results show that the asphalt modified by amine or organic polymers anti-stripping agent could significantly improve the adhesion between granite and asphalt. The Hamburg wheel-tracking test failed to fully reflect the whole process of high-temperature rutting failure. When evaluating the high-temperature performance and water stability of asphalt mixtures, it is recommended that the evaluation method should cover the whole failure stage of asphalt mixtures; considering the coupling effect of water and high temperature, the order of water stability of granite–asphalt mixture is proposed as follows: SCA&RMA > RMA > SBS > SCAMA > 70-A, and SCA&RMA has the best modification effect.

GMA material design and construction quality control for asphalt pavement of steel box girder: Case study of the Hong Kong–Zhuhai–Macau Bridge

To improve the quality of the Hong Kong–Zhuhai–Macao Bridge paving project, a new paving layer material, Guss-mastic asphalt (GMA), was proposed in this paper by combining the advantages of two types of cast asphalt mixtures: mastic asphalt (MA) and Guss asphalt (GA). Based on the characteristics of GMA, to simulate its actual production process, this study developed a small-simulated cooker mixing equipment. Moreover, the flow degree, 60 ​°C dynamic stability, and impact toughness were proposed to be used to evaluate the construction and ease, high temperature stability, and fatigue resistance of GMA cast asphalt mixtures, respectively. Moreover, the quality control standards for GMA paving materials by indoor tests, field trial mix GMA material performance tests, and accelerated loading tests were finalized. The study showed that the developed simulated cooker yielded consistent mixing results in the same working environment as the engineering cooker device. Increasing the coarse aggregate incorporation rate, coarsening the mastic epure (ME) gradation composition, and using a smaller oil to stone ratio can reduce the flowability of the GMA materials to varying degrees. The four-point bending fatigue life and impact toughness of the different GMA materials are correlated well. A mobility of <20 ​s, 60 ​°C dynamic stability of 400–800 ​times/mm, 15 ​°C impact toughness of ≥400 ​N·mm, and cooker car mixing temperature control standard of 210 ​°C–230 ​°C form an appropriate control index system for the design and production of GMA cast asphalt mixtures. Simultaneously, accelerated loading tests verified the accuracy and reliability of the quality control index system that has been used in the GMA paving project of the Hong Kong–Zhuhai–Macao Bridge deck and has achieved good application results.

Laboratory accelerated loading test to investigate the fatigue algorithm of the interface debonding of bonded concrete overly of Asphalt

The debonding mechanism of bonded concrete overlay of asphalt (BCOA) due to fatigue loading was investigated quantitatively based on an accelerated loading test. During the test, a nondestructive technique was deployed to measure the area of interface debonding. In addition, a numerical model incorporating a cohesive-zone based interface was developed to calculate the fracture energy associated with the interface debonding. Finally, the fatigue algorithm of the interface debonding was established by relating the area of debonding to the fracture energy. This fatigue algorithm can be used to predict the degree of BCOA debonding due to repeated traffic loading and the consequent stress increase in the overlay. Its development is of great significance, because it not only represents the physics of BCOA debonding more closely than the other existing models, but can also greatly improve the accuracy of the predicted life of the BCOA when incorporated into the design process.

Consolidation testing of tailings in a slurry consolidometer using constant rate and accelerated loading

A high rate of rise of fine-grained mine tailings slurry on disposal in a tailings storage facility (TSF) may maintain their condition as underconsolidated. The proper simulation of such field deposition of tailings in conventional laboratory consolidation testing is challenging. A slurry consolidation test using a high constant rate of loading (CRL) simulates a faster rate of tailings disposal in a TSF. A better simulation is achieved, however, by applying accelerated loading in a slurry consolidometer to allow for the increased drainage path length as tailings are built up in the TSF. CRL and accelerated loading were used in a purpose-built, large, instrumented, stress-controlled slurry consolidometer to examine and compare the consolidation behaviour of coal tailings, red mud and gold tailings. At the end of the CRL and accelerated loading tests, the excess pore water pressures had not fully dissipated and the maximum applied stress was maintained to achieve full primary consolidation. The findings of this study showed that the consolidation behaviour of the tailings studied varied with the nature of the tailings and with the loading applied.

Characterization of dynamic response of asphalt pavement in dry and saturated conditions using the full-scale accelerated loading test

Asphalt pavement exhibits different dynamic responses to vehicle loading in saturated conditions and in dry conditions. It is essential to directly conduct field full-scale tests to systematically investigate comprehensive influence of water on dynamic response of asphalt pavement. However, real vehicles which were often applied in field tests might result in a certain deviation in dynamic responses measured from each field loading test due to the inevitable influence of the driver’s subjective operation and the tread pattern on vehicle wheel. This study adopted the full-scale accelerated loading test system to comprehensively characterize dynamic response of asphalt pavement in both dry and saturated conditions based on the strict control of loading vehicle’s path. The results indicated that dynamic responses showed relatively larger magnitudes in saturated condition than those in dry condition. Strain and stress respectively showed slowly increasing and decreasing trends with the increase of vehicle load and speed correspondingly. Pore water pressure was apparently sensitive to vehicle speed compared with vehicle load. Pore water pressure generated by the front axle wheels showed obviously larger magnitudes than those produced by the rear axle wheels due to the change in thickness of surface runoff. The transverse distribution of pore water pressure obtained from both field tests and numerical simulation exhibited consistent variation trends. Decline degree of pore water pressure magnitudes was obtained at 86.1% for the two adjacent testing points with a distance of 100 mm under the vehicle wheel, which proved the great influence of the tread pattern of vehicle wheel on the transverse distribution of dynamic pore water pressure. A prediction model of positive pore water pressure that considered vehicle load and speed was proposed.

Noise Reduction Characteristics of Macroporous Asphalt Pavement Based on A Weighted Sound Pressure Level Sensor.

Based on the manual of macroporous noise-reducing asphalt pavement design, the indoor main drive pavement function accelerated loading test system was applied to investigate the impact of speed, loading conditions (dry and wet) and structural depth on the noise reduction of macroporous Open Graded Friction Course (OGFC) pavement, as well as its long-term noise reduction. Combined with the noise spectrum of the weighted sound pressure level, the main components and sensitive frequency bands of pavement noise under different factors were analyzed and compared. According to experimental results, the noise reduction effect of different asphalt pavements from strong to weak is as follows: OGFC-13 > SMA-13 > AC-13 > MS-III. The noise reduction effect of OGFC concentrates on the frequency of 1–4 kHz when high porosity effectively reduces the air pump effect. As the effect of wheels increases and the depth of the road structure decreases, the noise reduction effect of OGFC decreases. It indicates the noise reduction performance attenuates at a later stage, similar to the noise level of densely graded roads.

Fatigue damage property of permeable friction courses under the water-temperature-load coupling action

In order to investigate the fatigue damage property of permeable friction courses (PFC) under the coupling action of water, temperature and load, the PFC with length of 2.93 m, width of 1.10 m and thickness of 0.04 m was prepare in the laboratory and tested by the accelerated loading testing system MMLS3. The profilometer and the portable seismic properties analyzer (PSPA) was utilized to measured the rutting depth and modulus of the whole asphalt pavement, respectively. It is found that the PFC is compaction-type rutting. In the position 200 mm, the modulus first increases and then decreases. The excess pore water pressure is not measured in pavement. The results can provide beneficial references for the design, construction and fatigue damage analysis of PFC.

Influencing factors and mechanism for the attenuation of the skid resistance for bauxite clinker-asphalt mixtures

The maintenance and improvement of the skid resistance of asphalt pavement have been a major concern for road researchers. To explore ways to improve the skid resistance, the attenuation mechanism of the skid resistance must first be understood. In this study, accelerated loading testing equipment MMLS3 was used to analyze the attenuation of asphalt mixtures under different cumulative load times. Also, the impact of the abrasion resistance characteristics of mineral materials, the aging and asphalt film spalling characteristics of asphalt mixtures, the change of the internal structures of asphalt mixtures on the attenuation, and the surface texture characteristic parameters of skid resistance were investigated. The skid resistance attenuation mechanism was also inferred based on the accelerated loading test results. The reason for the accelerated attenuation of the asphalt mixtures was mainly due to the changes in the asphalt mixture structure based on the results of the accelerated loading tests and the abrasion of the aggregates. The positive influence of asphalt film spalling on the anti-sliding performance was not enough to compensate for the negative influence of the structural changes. The aging of asphalt mixtures also had a great impact on the anti-skid performance. In real engineering, the aging time of the asphalt mixture lasts for a long time, so the impact on the anti-skid performance was not obvious.

Characterization of the fatigue behavior of asphalt mixture under full support using a Wheel-tracking Device

Most existing fatigue testing methods in the laboratory are designed to evaluate the cracking resistance of asphalt mixture only, regardless what types of structural support it is used in the field. However, literature has confirmed that fatigue cracking is a structural related distress, and the cracking potential of asphalt layer is strongly affected by its underneath structural supporting conditions. On the other hand, the Hamburg Wheel-tracking Device (HWTD) has gained popularity for characterizing the rut-resistance and moisture susceptibility of asphalt mixtures under moving loads among state Department of Transportation (DOT) and agencies, and it has the capability to be modified to specify supporting conditions. Therefore, in this study, we propose to make some modifications to the existing HWTD and to study its capability of being also utilized as a cracking device for its potential advantages in equipment availability and simulating field loading and structural conditions. The developed HWTD fatigue test was used to simulate the conditions experienced by an asphalt mixture layer paved on the flexible base and applied with a vertical moving load. Three mixtures were specially designed to have known fatigue behavior difference for evaluating the reliability of this newly developed method, and to be compared with the standard American Association of State Highway and Transportation officials (AASHTO) semi-circular bending (SCB) method (AASHTO TP 124-18). A variety of strain and pressure gauges were used to record the load responses for fatigue behavior analysis. Both the phenomenological fatigue life analysis approach and the dissipated energy based ratio of dissipated energy change (RDEC) approach were used for data analysis. It was found that the HWTD fatigue test was essentially a type of laboratory scale accelerated loading test which can simulate the fatigue cracking phenomenon under the proposed testing setup. The RDEC approach with different failure criteria were suitable and effective in analyzing the testing data and can quantify the fatigue behavior of specific mixture within reasonable time frame. The results were consistent with the standard SCB fracture test results. In conclusion, the HWTD fatigue test has the potential to be a rational and convenient method for characterizing the fatigue behavior of hot mix asphalt (HMA) materials with the consideration of supporting conditions.

Study on dynamic modulus of asphalt mixture in cold regionunder rotary accelerated loading

In order to study the evolution law of mechanical properties of asphalt pavement mixture in cold regions under long-term load, the rotary accelerated loading equipment was used to carry out a total of 500,000 accelerated loading tests on the full-scale pavement, and the dynamic modulus test of the mixture before and after wheel load was carried out respectively. The master curve of dynamic modulus and dynamic modulus ratio (dynamic modulus value after wheel load / dynamic modulus value before wheel load) of the mixture at -20ºC were established to predict the long-term mechanical response of the mixture at low temperature. The results show that: low-frequency (or high temperature) has a more significant effect on the viscoelastic properties of the asphalt mixture. In the conversion frequency range of 1.6×10–3~1.6×102 Hz, the dynamic modulus ratio decreases with the increase of frequency, and the maximum ratio is 0.62 when the frequency is 1.6×10–3 Hz, which indicates that the high frequency (low temperature) has little effect on the performance of asphalt mixture. This study can be used as a theoretical reference for the structural design and performance optimization of asphalt pavement in cold regions.

Study on Fatigue Life of Cement Stabilized Macadam Base during Crack Expanding Phase Based on Accelerated Loading Test

The evaluation for remaining life of semi-rigid base layer has a significant effect on pavement maintenance scheduling like resurface or rehabilitation. An accurate evaluation can obviously improve the pavement maintenance, which could also utilize the original pavement structure in a rationally way, and optimize the entire maintenance plan. In this study, a series of laboratory investigation were conducted on the cement stabilized macadam materials. The fatigue life and deterioration characteristics of cement stabilized macadam materials were analyzed during the pre-cracked (fatigue cracks occurring) phase and crack expanding phase by laboratory fatigue test and full-scale accelerated loading test, respectively. Then, a fatigue life correction coefficient of the crack expanding phase was used to analyze the fatigue properties of the semi-rigid base, and a modulus degradation model of the semi-rigid base life was characterized. It proved to be convenient to evaluate the residual life of semi-rigid base according to the modulus.

Research progress of long-life asphalt pavement behavior based on the RIOHTrack full-scale accelerated loading test

Full-scale accelerated loading test is an efficient and effective method for simulating and studying long-term pavement performance because its loading and environment conditions are similar to those of real-world applications. In the past decades, this method has been recognized as an important support for the development of pavement design theory worldwide. In 2000, the long-life pavement was first presented by the researchers in Europe and the USA to obtain the most economical pavement during the whole life cycle. However, the completed design method of the long-life asphalt pavement has not been provided, especially for semi-rigid base asphalt pavement. In 2015, the Research Institute of Highway, Ministry of Transport constructed a 2.038-km-long full-scale field accelerated pavement testing track, which was named as RIOHTrack, to develop a long-life pavement suitable for China. The testing road has 25 asphalt pavement structure sections, and the average length of the testing section is 60 m. In all of the testing sections there were 19 structural testing sections, which are classified into six types, namely, the thin asphalt layer semi-rigid base pavement, the normal semi-rigid base pavement used in China, the composite pavement, the inverted pavements, the thick asphalt layer asphalt pavement, and the full-depth asphalt pavement respectively. In the first research phase, RIOHTrack planned to complete 50 million equivalent single axle loads ESALs (10 tons standard axle loading) by using trucks under the real environment. During the accelerated loading, two types of pavement performance detections were conducted. The first type is the real-time strain/stress responses and the environment information captured by the monitor sensors, and the other type is the periodic pavement performance detection measured by auto-detecting devices or artificial measures. In this paper, the bearing capacity, service performances, and inner mechanism responses under the couple of loading and environment were analyzed on the basis of the whole detecting data captured from December 2016 to January 2020. Four main conclusions were drawn. First, the influence of loading and environment on performance is considerably, and the influence degree of environment is even larger than that caused by the loading. Second, the pavement performance has structural dependence, the ranking of the six main types varies if evaluated using different performance indices, and the rutting depth prediction accuracy depends on the structural type. Third, the stress/strain monitoring results verify the nonlinear characteristic of asphalt pavement structure under the temperature and loading. To calculate the nonlinear effect in pavement behavior, a new mechanical analysis method was presented, which considers material and geometric nonlinearity theory. Lastly, to improve the prediction accuracy of the rutting depth, we utilized multivariate statistics to build the new prediction model based on the measured rutting depth data, and this model considers the changes in loading number and temperature change. The stage research results illustrate that the different type of pavement structure has its advantages and disadvantages, so the type of the long-life asphalt pavement should be multiple choice. China has the longest mileages of semi-rigid base asphalt pavements. Hence, long-life, semi-rigid base asphalt pavement building, and maintenance technology should be developed. More works should be carried out on mechanism analysis, prediction models, and failure criteria, and the accelerated loading test, such as RIOHTrack, will mainly provide support.

Experience and challenges of long-term performance research on asphalt pavement

The long-term performance of China’s asphalt roads has exhibited significant improvements in the past decades. The material-performance testing methods are being gradually established, the structural thickness-design method has been constructed, and construction technologies and quality-control methods have been developed. Additionally, hundreds of field-test sections were monitored, and accelerated-loading tests were conducted to identify the significant determinants that could potentially affect field performance, including the surface friction, permanent deformation, transverse crack, and fatigue crack. Field-distress-detection method and equipment have been developed to quickly obtain the performance information and provide critical feedbacks to road designers. The mechanisms that correspond to the most observed distresses in China were explored, and predictive models with varied performance in field roads were accordingly developed and validated. Road maintenance strategies were established, and materials that fit the varied field distresses were developed to improve maintenance quality. Despite the aforementioned efforts, asphalt pavements in different regions in China exhibit dramatically varying service lives, and we can see that the service life of roads is commonly lower than the design life. The main reasons are that the long-term performance studies mostly concentrated on small-scale test sections that could not fully represent the full-scale field-pavement sections, and the field test of roads were too concentrated in specific areas to include the effects of key parameters such as the variation in climatic conditions, traffic loads, water table, and local material properties. Furthermore, most research lacked national-level coordination and planning with short time duration, and obtaining the research reports online was difficult. In addition, the long-term performance-prediction models relied more on laboratory tests and lacked diversity and continuity. They were limited to single environmental factor, mismatched traffic loads and actual conditions, limited simulation of long-term-failure forms, and insufficient field validation. Thus, using these models as a guide to effectively design pavements with reasonable durability is difficult. In general, the long-term performance research of asphalt pavement in China has good preliminary foundations, and most policy makers and researchers possess the enthusiasm and confidence to design and construct better roads. However, many challenges remain be solved in terms of performance prediction with higher prediction accuracy, research orientation, research duration, all-round continuous observation, data quality control and standardization, and establishment of open database. We recommend carrying out nationwide deep-level, large-scale, and long-term pavement-performance observation as well as prediction research. The main subjects of these studies include but are not limited to the following: (1) Scaling to supplement and improve nationwide long-term performance field projects based on existing research and layout; (2) building a national unified, continuous, and long-term performance-observation network; (3) establishing a road life-cycle standardized database that includes design information, raw-material resource, construction procedure, service condition, and maintenance strategy and effectiveness; and (4) constructing performance prediction models that consider both mechanical calculated response (i.e., stress and strain) and statistical analysis, factors that cover climatic condition (i.e., environmental factors from different areas), traffic loads, structural thickness, and materials.

Numerical Simulation and Laboratory Testing Verification on the Performance of an Asphalt Pavement Seal Coat with Superficially Permeating and Solidifying Properties

Abstract In recent years, preventive maintenance has been used widely to solve the problem of early-stage asphalt pavement damage. However, conventional preventive maintenance treatments cannot effectively prevent rutting or damage resulting from the leakage of diesel fuel to the pavement. In this context, numerical simulations of uniaxial penetration tests were conducted with the Discrete Element Model to evaluate the feasibility and effectiveness of pavement surface solidification with a special seal coat. Standard viscosity tests on mixtures of waterborne epoxy resin and emulsified asphalt used as the Permeating and Solidifying Seal Coat (PSSC) material were performed, and uniaxial penetration tests and accelerated loading tests were conducted on asphalt mixture specimens with and without the PSSC. The optimum proportion of PSSC material was determined and its permeability, rutting resistance, diesel fuel corrosion resistance, and durability were evaluated. The results of this study indicate that the superficially solidified pavement with PSSC can effectively enhance rutting resistance and diesel fuel corrosion resistance and can provide more durable skid resistance and better antistripping performance than conventional preventive maintenance treatments. Therefore, the PSSC could be considered a new generation of preventive maintenance treatments for asphalt pavements.

Antiageing Performance Evaluation of Recycled Engine Oil Bottom Used in Asphalt Rejuvenation

To comprehensively evaluate the antiageing performance of recycled engine oil bottom (REOB) used in asphalt rejuvenation, ageing performance studies were carried out on REOB, REOB-rejuvenated asphalt, and REOB-rejuvenated asphalt mixture. The thin film oven test (TFOT) results of REOB and a professional regenerant, RA5, were compared to verify the ageing resistance of REOB as an asphalt regenerant. The quality and viscosity of REOB-rejuvenated asphalt, RA5-rejuvenated asphalt, and base asphalt were measured after extended TFOT (ageing times for 5 h, 10 h, 15 h, 20 h, and 25 h), and the low-temperature performance of three aged asphalts was evaluated by bending beam rheological tests. The corresponding three kinds of asphalt mixtures were used to design and pave surface layers of a full-scale indoor test road. The long-term fatigue performance of indoor asphalt pavement was investigated by a self-developed rotary accelerated loading test (RALT) system. The results show that when used as an asphalt regenerant, REOB meets the antiageing requirements listed in the technical specification. The short-term (TFOT ageing time less than or equal to 10 h) ageing resistance of REOB-rejuvenated asphalt is better than that of RA5-rejuvenated asphalt but worse than that of base asphalt, whereas the long-term (TFOT ageing time greater than or equal to 15 h) ageing resistance of REOB-rejuvenated asphalt is the worst among the three tested asphalts. After long-term ageing, REOB-rejuvenated asphalt is prone to cracking at low temperatures because of its rapid increase in stiffness and sharp decrease in stress relaxation performance. Increasing temperatures increases the deflection value of asphalt pavement as the number of loading cycles increase. High-temperature ageing significantly aggravates the increase of the deflection value of REOB-rejuvenated asphalt pavement under RALT long-term loading, which makes it most prone to fatigue failure among the three pavements. Therefore, the above test results show that REOB used in asphalt pavement rejuvenation is prone to premature and excessive damage.

Performance evaluation of new waterborne epoxy resin modified emulsified asphalt micro-surfacing

Abstract Micro-surfacing is an available choice for pavement preventive maintenance. This paper introduced a new micro-surfacing using developed Waterborne Epoxy Resin (WER) modified emulsified asphalt to overcome the common distress, such as abrasion, rutting, ravelling and poor durability. The skid resistance, bonding, rutting and wear performances of different formulations of the proposed micro-surfacing materials were compared with Styrene Butadiene Rubber (SBR) modified micro-surfacing by load wheel tests, wet track abrasion tests, skid resistance tests, load wheel tracking tests, cantabro tests and accelerated loading tests. Results indicated that WER could improve the early pavement performance of micro-surfacing significantly, especially their bonding and rutting resistance. WER also produced improved durability performance. The damage in the critical condition of water immersion, freeze–thaw and heavy traffic was alleviated greatly by the use of WER. Therefore, it can be concluded that WER modified emulsified asphalt is a good binder for micro-surfacing.

Fatigue Performance Analysis of Pavements with RAP Using Viscoelastic Continuum Damage Theory

This paper presents the results of a study to evaluate the fatigue performance of pavements that contain RAP materials. The study is based on two different accelerated loading tests conducted in the United States. Each of these two projects has corresponding pavements with and without RAP mixtures that were constructed over the same aggregate base and subgrade and subjected to the same traffic loading and environmental conditions. The primary reason for selecting these two projects is that they exhibited opposite trends in a comparison of the fatigue cracking performance of their pavements with and without RAP. The asphalt mixtures in the test pavements were characterized using the simplified viscoelastic continuum damage model. The fatigue cracking performance of the pavements was then modeled using the characterized material properties, in situ pavement structures and traffic loads, and climate conditions in FlexPAVE™, a three-dimensional layered viscoelastic finite element program with moving load analysis. The resultant fatigue cracking performance predictions matched the field observations well. Both the simulation results and the field observations also showed that the fatigue cracking performance of the asphalt mixtures that