Pavement Test Research Articles

Quantifying the Performance of Warm-Mix Asphalt and Reclaimed Asphalt Pavement in Flexible Airfield Pavements

Warm-mix asphalt (WMA) is a current paving technology that uses various techniques for producing and constructing asphalt at lower temperatures. The benefits associated with WMA range from reduced carbon dioxide emissions to extended paving seasons. The performance and the environmental benefits of WMA can be enhanced by the addition of reclaimed asphalt pavement (RAP) to the aggregate portion of the mix. This technology has been extensively used in the highway sector, but its use in the airfield sector has not been documented fully. Currently, asphalt mixtures used in the surfaces of airfield pavements are designed in accordance with the FAA P-401 specifications. This study quantified the performance of a WMA-RAP mixture compared with the standard FAA P-401. The asphalt mixture performance tester was used to test the mixtures for flow time and load cycles to failure so as to capture the rutting and fatigue cracking potentials of both mixtures. The laboratory data were used as input to the three-dimensional finite element analysis software ABAQUS, and the mechanical responses were determined within the surface layer of the airfield flexible pavement section modeled to represent the section constructed at the FAA National Airport Pavement Test Facility. The Greenhouse Calculator for State Departments of Transportation, a product of NCHRP Project 25–25, was used to assess the environmental impacts of both mixtures. This study's findings indicate that the laboratory and predicted performance of the WMA-RAP mixture are comparable to the performance of a standard FAA P-401 mixture. The cost and environmental benefits of the WMA-RAP mixture make this type of material a viable alternative to the standard FAA P-401 mixture.

Modification of the Resistivity-Rutting Model to Use Recoverable Creep Compliance

The resistivity-rutting model was developed as part of NCHRP Projects 9-25 and 9-31 and later was improved as part of Airfield Asphalt Pavement Technology Program Project 04-02. The model was intended to provide insight into the effects of mixture composition and binder properties on resistance to permanent deformation, but the use of |G*|/sin δ to characterize binder flow properties did not accurately capture the performance of modified binders, so an empirical correction factor was needed to address this problem. The modified model presented in this paper incorporated Jnr from the multiple stress creep and recovery (MSCR) test, in place of |G*|/sin δ, as an indicator of binder resistance to permanent deformation. This adjustment provided a more theoretically correct and more accurate means to characterize asphalt binder flow properties for use in the resistivity-rutting model. Because a large number of pavement test sections does not yet exist to provide information on rutting, including MSCR test data, the approach used here was to develop an empirical equation that related Jnr to standard dynamic shear rheometer test data. This relationship was then used to estimate Jnr for a database that consisted mostly of the original data used to develop the resistivity-rutting model. The recalibrated model appeared to have an accuracy similar to that of the previous version of the model but properly predicted the performance of modified binders without empirical correction factors.

Effects of Binder, Curing Time, Temperature, and Trafficking on Moduli of Stabilized and Unstabilized Full-Depth Reclamation Materials

This paper provides a summary of in situ layer moduli of several full-depth reclamation (FDR) materials used in an accelerated pavement test (APT) track. The reclaimed layers were constructed during the FDR of four lanes of 60 mm of rubberized hot-mix asphalt (HMA), 60 mm of HMA, and 130 mm of aggregate base. The FDR layer served as the base under a new HMA layer. Each lane had a different stabilization strategy, namely, unstabilized, stabilized with foam asphalt plus cement, stabilized with cement only, and stabilized with engineered asphalt emulsion. Falling weight deflectometer testing was conducted on the test track at various times during the course of the study, and the data were used to backcalculate the FDR layer moduli. The results were used to investigate the effects of each stabilization strategy, loading temperature, curing time, and trafficking on the in-place layer moduli of the FDR layers and to provide critical inputs for mechanistic–empirical pavement design of FDR layers.

Evaluation and Implementation of PG 76-22 Asphalt Rubber Binder in Florida

The Florida Department of Transportation (DOT) has had a long history of recycling ground tire rubber (GTR) from waste tires in highway projects. The Florida DOT first experimented with asphalt rubber binder (ARB) more than 35 years ago. In 1988, the Florida legislature mandated the investigation of using recyclable materials such as GTR in roadway construction. For more than 25 years, the Florida DOT has effectively satisfied the intent of the legislature. However, the ARB has often been associated with unpredictable performance and handling issues, such as the separation of the GTR from the binder. These performance and handling issues have resulted in higher construction costs and have made ARB less appealing because a more reliable alternative, PG 76-22 polymer modified asphalt (PMA), is available. As a result, a task team of the Florida DOT and industry members was formed with the goal of finding a way to make ARB handle and perform similarly to PG 76-22 (PMA), Florida's gold standard binder. This paper documents an accelerated pavement testing (APT) study to compare hot-mix asphalt mixtures constructed with PG 76-22 (PMA) and PG 76-22 (ARB). This APT study represents the final stage of the implementation of a new PG 76-22 (ARB) specification.

Evaluation of a permanent deformation model for asphalt concrete mixtures using extra-large wheel-tracking and heavy vehicle simulator tests

This paper evaluates a mechanistic–empirical permanent strain model for asphalt concrete mixtures. The evaluation was carried out based on two different types of tests: an extra-large wheel-tracking (ELWT) test and a full-scale accelerated pavement test using a heavy vehicle simulator (HVS). Asphalt slabs from three different types of asphalt mixtures were prepared for the ELWT test and tested at several pavement temperatures and tyre inflation pressures. Lateral wandering was also incorporated. The measured permanent deformations in the asphalt slabs were thereafter modelled using the permanent strain model from the US Mechanistic-Empirical Pavement Design Guide and model parameters were estimated for the three types of mixes. For validation, data from an HVS tested pavement structure consisting of the same asphalt mixtures as those tested using the ELWT were used. A set of calibration factors for the three mixtures were therefore obtained between the two tests. In all cases, the calibration factors were within ±20% from unity. Differences in geometry, scale, wheel loading configuration as well as the speed of loading between the two test devices could be the possible reasons for the differences in observed calibration factors.

Field validation of recycled cold mixes viscoelastic properties

Visco-elastic properties of recycled cold mixes are analyzed in this paper by tests carried out in laboratory; the aim of the paper is to evaluate how reliable are these properties to be used for the prediction of visco-elastic response of pavement layers containing recycled cold mixes.The paper focuses on both bitumen emulsion and foam bitumen recycled cold mixes; two different mixtures were designed in laboratory to achieve specific mechanical properties and used to build two instrumented test sections. Visco-elastic properties and fatigue resistance of these mixtures were determined on cores extracted from the test sections and compared with those determined on a conventional hot asphalt mixture for base layer. This comparison allowed to highlight the reduced thermo-sensitive and time-dependant behavior of these mixtures.Visco-elastic properties of the recycled cold mixtures determined in laboratory, then were used to predict strains in the base layer of the test pavements by using the ViscoRoute 2.0 software. The comparison between measured and predicted strain pulses allowed to evaluate the reliability of visco-elastic parameters determined in laboratory to predict response of layers composed of recycled cold mixes. The obtained results show that visco-elastic parameters of bitumen emulsion recycled cold layers exhibit a satisfactorily capacity to accurately reproduce the pavement response; the same reliability cannot be found for foam bitumen recycled cold layers, whose behavior diverges significantly from that of a continuum.

Full-scale test of thermally induced reflective cracking in airport pavements

While a reflective cracking propagation rate of 25 mm per year is well accepted by airport pavement engineers, the mechanism of reflective cracking under field conditions has not been fully investigated. A recently completed project sponsored by the Federal Aviation Administration (FAA) led to the development of the Temperature Effect Simulation System (TESS). After an in-depth evaluation of the TESS, full-scale tests to mechanically simulate thermally induced reflective cracking were conducted. A large simulation matrix was first developed to select promising joint opening and displacement rates using three-dimensional viscoelastic-based finite element analyses. A test pavement was then built, instrumented, and tested at the FAA National Airport Pavement Test Facility (NAPTF). This paper describes the successful full-scale test, crack monitoring under accelerated loading, and the data analysis used to evaluate the crack development. Main research conclusions included: (1) “25 mm per year” was quite conservative for thermally induced reflective cracking; (2) Once bottom-up reflection cracks reached a critical length, the crack evolution became very aggressive. For that reason, it is hypothetical to sandwich a strain-relieving hot mix asphalt interlayer between the Portland cement concrete slabs and the new overlay to minimise overlay stresses and to tolerate horizontal movements at the joint. Furthermore, significant insights into the mechanisms and mitigation of thermally induced reflective cracking were obtained and presented. Findings from this study are of immediate assistance to airports supporting light to medium weight aircraft and experiencing significant temperature cycling.

Instrumentation and performance modelling of heavy vehicle simulator tests

Flexible test road structures have been built and tested in accelerated pavement tests using a heavy vehicle simulator (HVS) at VTI in Sweden for 15 years. The objectives have been to investigate pavement responses and pavement performance behaviour, which can be used to validate mechanistic performance schemes. Here, the instrumentation is described, its accuracy is estimated, the response and performance are modelled and a performance prediction is carried out. The registrations of the measurements were rather smooth with acceptable variation. In general, good agreement was established between the measurements and calculations. The HVS machine can be used to evaluate new road concepts and maintenance strategies and provides the option of performing a life cycle cost analysis, which can decrease both costs and environmental impacts.

Performance of Permeable Block Pavements in Accelerated Pavement Test and Rainfall Simulation

As industrialization advances, the increase in impermeable areas in urban regions has changed the water circulation system. Hence, many environmental issues such as heat islands and city floods have arisen. To solve this issue, related research with a high budget allocation is currently being carried out. A method of addressing this issue is to utilize permeable block pavements. The bearing capacity and hydrological efficiency of permeable block pavement with different base types was evaluated in this study using two accelerated pavement testings (APTs). Rutting was evaluated by performing a comparative analysis in each permeable block pavement. Furthermore, the hydrological characteristics were reviewed through a rainfall simulation experiment. The results of APT show that performance of permeable block pavements varies depending on the base type and traffic volume. Based on the result, it was demonstrated that the permeable block pavement is applicable for a vehicle road as well as the sidewalk. In addition, it was demonstrated that this pavement can improve the water circulation system.

Modulus evolution of asphalt pavement based on full-scale accelerated pavement testing with Mobile Load Simulator 66

A full-scale accelerated pavement testing was conducted with Mobile Load Simulator 66 in Chongming Island, Shanghai, to study the performance response of a semi-rigid base asphalt pavement with fine-sand subgrade designed for the G40 construction. As an index sensitive to temperature and load, three different moduli including the seismic modulus, field falling weight deflectometer back-calculation modulus and interior material testing system resilient modulus were all measured during and after the test. The modulus evolution of asphalt pavement with the loading applications, rutting, strain and temperature, and the comparison of three methods for measuring modulus were analysed. There exists a modulus gradient from top to bottom, which can be considered in the pavement design or fatigue life prediction. Because of the strain level differences, the seismic modulus was the largest, followed by back-calculation and resilient modulus; the development of seismic and back-calculation modulus better reflected the anti-deformation changes.

An evaluation of warm-mix asphalt performance using accelerated pavement testing in Korea

As part of the research to evaluate the Warm-Mix Asphalt (WMA) performance for use in Korea, an extensive testing program has been conducted on the warm-mix asphalt technology that is newly developed in Korea, along with Hot Mix Asphalt (HMA). This research program consists of Accelerated Pavement Test (APT) and laboratory test. This paper presents the rutting and fatigue performance test results of both WMA and HMA. The rut development due to trafficking loading was evaluated using APT with 8.2 ton loading at 40°C temperature. The transverse profile was measured periodically at each point per test section as a function of mixture types. In order to investigate the fatigue performance, APT applied trafficking loading under wet and dry condition. The very stiff base is likely to complicate the planned fatigue cracking test, in that a huge number of APT repetitions will be generally required before any distress occurs. In this study, therefore, the fatigue test was conducted at 20°C with adding water into the aggregate base layer to accelerate the distress after the given trafficking loading. Cores were taken to be tested in the laboratory after construction of the test track as well as after completion of APT testing on and off the wheel path. The air voids were measured for all cores and dynamic modulus test and fatigue test in indirect testing mode were conducted. Based on the limited data obtained from this study, it is concluded that WMA mixture performs comparable to HMA mixture in terms of rutting and fatigue resistance.

Selecting a rutting performance test for airport asphalt mixture design

This paper presents results from a laboratory study to identify a performance-based acceptance test for hot asphalt mixtures when constructing airport pavements designed to accommodate high-tyre-pressure traffic. Four performance tests, intended to screen for rutting susceptibility, were performed on 26 hot mix asphalt (HMA) mixtures using one neat binder. Eight of these mixtures were also prepared with a polymer-modified binder. Results from four candidate tests are presented: asphalt pavement analyzer, triaxial creep, triaxial repeated load, and dynamic modulus test. Preliminary criteria associated with these tests that can be used to screen or select airport HMA paving mixtures are proposed. The efficacy of the screening tests and associated criteria were evaluated by constructing and trafficking full-scale pavements using an accelerated pavement tester.

A study of crumb rubber modified bitumen used in South Africa

In South Africa, an empirical characterisation of crumb rubber modified (CRM) bituminous binders has historically been the only means of predicting their performance in pavement layers, short of constructing pavement test sections. An improved characterisation is provided by means of rheological analysis using a dynamic shear rheometer (DSR). However, the heterogeneous morphology of CRM bitumen makes it a challenge to test using current methods and equipment. DSR testing of CRM bitumen requires a plate gap adjustment to avoid any influence by the rubber particles. This has been done by monitoring the effect of changing the DSR plate gap setting on the measured linear visco-elastic properties of the binder. An adjusted gap was adopted for rheological measurements so as to characterise CRM bitumen properties with ageing. But, the incomplete recovery of CRM binder from asphalt/seals makes it impossible to monitor the rheological properties of the in situ binder within a pavement layer. This has led to indirect methods of investigating relationships between tested properties of the pure CRM bitumen to those of the in situ binder.

Effect of full-size and down-scaled accelerated traffic loading on pavement behavior

Accelerated pavement testing (APT) is an effective testing procedure to evaluate asphalt pavements. With APT it is possible to determine and measure the structural response and pavement performance under a controlled, accelerated damage accumulation in a compressed period of time. However, different types of APT technologies can lead to different results. Full-size loading devices simulate road traffic accurately, but are expensive, while down-scaled size simulators are cost effective, nevertheless further away from reality. In this work, two types of APT mobile load simulators with different loading characteristics are compared with respect to pavement response in the field and in the laboratory. The MLS10 is a full-size simulator, whereas the MMLS3 is a one-third scale device. The relationship between the devices was studied in terms of the measured strains induced by both machines in the same pavement. Therefore, a testing field was instrumented with strain gauges and first trafficked with MLS10. Later, a slab of the instrumented pavement was cut off the road and tested in the laboratory with the smaller MMLS3. Furthermore, the structure of the pavement was modelled with a viscoelastic finite element method model and the moving loads of both machines were simulated considering size, speed and approximate footprints of their tires. As for the pavement materials, the properties of the different asphalt layers were determined in the laboratory. Experimentally acquired strain data were used to validate the models. Stress fields under different loading and environmental conditions were analysed and compared. The evaluation shows that the models can predict the pavement response under different loading conditions. However, they still need to be improved to increase the accuracy under different conditions. Further, the analysis of the strains show that both load simulators induce a different stress–strain situation and scaling of the pavement should be considered.

Correlation of Non-Destructive Pavement Test Devices

This paper studies the correlation of non-destructive pavement test devices, the falling weight deflectometer (FWD) and Benkelman Beam (BB), in evaluation of pavement structure capacity. Field measurements were made at an expansion highwayG6 in Ningxia Hui Autonomous Region, China. Based on the deflection results measured with FWD and BB, the relationship between FWD and BB was established. The subgrade moduli of the test section were back-calculated. The results show that the ratio of E(sta) and MR(dyn) is consistent with the suggestion of AASHTO 1993. Due to the fact that the use of FWD test is convenient and the results are stable, it demonstrates that the falling weight deflectometer (FWD) is an appropriate device to evaluate the pavement structural and to select the optimal pavement rehabilitation strategy in the near future.

Stormwater quality of spring–summer-fall effluent from three partial-infiltration permeable pavement systems and conventional asphalt pavement

This study examined the spring, summer and fall water quality performance of three partial-infiltration permeable pavement (PP) systems and a conventional asphalt pavement in Ontario. The study, conducted between 2010 and 2012, compared the water quality of effluent from two Interlocking Permeable Concrete Pavements (AquaPave® and Eco-Optiloc®) and a Hydromedia® Pervious Concrete pavement with runoff from an Asphalt control pavement. The usage of permeable pavements can mitigate the impact of urbanization on receiving surface water systems through quantity control and stormwater treatment. The PP systems provided excellent stormwater treatment for petroleum hydrocarbons, total suspended solids, metals (copper, iron, manganese and zinc) and nutrients (total-nitrogen and total-phosphorus) by reducing event mean concentrations (EMC) as well as total pollutant loadings. The PPs significantly reduced the concentration and loading of ammonia (NH4++NH3), nitrite (NO2−) and organic-nitrogen (Org-N) but increased the concentration and loading of nitrate (NO3−). The PP systems had mixed performances for the treatment of phosphate (PO43−). The PP systems increased the concentration of sodium (Na) and chloride (Cl) but EMCs remained well below recommended levels for drinking water quality. Relative to the observed runoff, winter road salt was released more slowly from the PP systems resulting in elevated spring and early-summer Cl and Na concentrations in effluent. PP materials were found to introduce dissolved solids into the infiltrating stormwater. The release of these pollutants was verified by additional laboratory scale testing of the individual pavement and aggregate materials at the University of Guelph. Pollutant concentrations were greatest during the first few months after construction and declined rapidly over the course of the study.

Thin asphalt pavement performance equation through direct computation of falling weight deflectometer-derived strains

A fundamental aspect in a pavement management system is the evaluation of the pavement structural condition and its capability in supporting the designated traffic. The nondestructive technique of the falling weight deflectometer and the layered elastic model are commonly used to identify pavement structural condition. The approach in this article is mechanistic–empirical, with the intent to correlate the strain at the bottom of the asphalt layer with the number of coverages to failure. Strains were computed through mathematical approximation of the deflection basin measured at failure. The proposed asphalt criterion showed the same trend of the subgrade strain criterion developed in conjunction with the reformulation of the California bearing ratio (CBR)-Beta design criteria. The approach provided encouraging results when compared with the other analyses in the development of the CBR-Beta criteria. The database was from the full-scale flexible pavement testing at the US Army Engineer Research and Development Center in Vicksburg, MS, USA.

Full-scale field testing of precast Portland cement concrete panel airfield pavement repairs

A series of various sized Portland cement concrete (PCC) airfield repairs was performed using precast panels. The repairs received simulated C-17 aircraft traffic, and each repair was trafficked to failure. A heavy weight deflectometer was used to measure the panels' response to loading with increasing traffic applications. The results of traffic testing were used to evaluate the suitability of the precast panel repair technique for rapidly repairing PCC airfield pavements. Test results showed that the repair system was capable of supporting at least 5000 passes and possibly as many as 10,000 passes of C-17 traffic. Compared with other rapid airfield repair methods, the precast panel repair alternative may provide similar return-to-service timeliness and traffic performance at a slightly higher cost. Modifications to the system design and placement procedures are recommended to improve the field performance of the panels.

Methodology for relating accelerated trafficking to field trafficking for pavement evaluation

Over the years, numerous Accelerated Pavement Testing (APT) devices have been developed to facilitate quick evaluation of the performance and service life of pavements, materials, and related products under various loading and environmental climatic conditions. However, it is often challenging to translate or extrapolate the onset of distress, severity, and evolution caused by accelerated trafficking to that experienced in the field under different loading and environmental conditions. This is especially true if testing is conducted on specimens or reduced-scale slabs. The objective of this study is to present a methodology for establishing a relationship between accelerated and actual trafficking applied in the field. For this purpose, a Finite Element Method (FEM) analysis was conducted for specimens trafficked by the Model Mobile Load Simulator at 1/3rd scale (MMLS3) at conditions that favor rutting. As expected, it was observed that the rutting models developed and calibrated for field traffic do not accurately predict the rutting progression that was measured in these specimens. A methodology to more accurately predict rutting under accelerated trafficking is suggested, by which the loading effect of the MMLS3 is related to an equivalent 18-kip single axle load. New coefficients for the rutting model are devised to be used in conjunction with the MMLS3 testing.

Research on the Influence of Temperature and Humidity to Asphalt Pavement Seedless Detection Technology

In order to study the asphalt pavement testing compaction technology accuracy with the non-nuclear density gauge. Pave TrackerTM Plus 2701-B is used to research the influence of temperature and humidity, and Construction dynamic detection technology and methods is established basing on 2701-B,And the type of mixture was studied. It is found that, because of the difference of temperature and humidity, the result of Compaction degree has the large variability, the increased with temperature and humidity, especially humidity affects more significant. Finally, the non-nuclear detection technology method of asphalt pavement is established, this paper presents adopting the temperature and humidity compensation or increasing the number of calibration samplesisand and testing used to make up accuracy, which can effectively improve the service performance of airport asphalt pavement.