Performance-graded Asphalt Binders Research Articles

Superpave performance graded asphalt binder selection for asphalt mixture design in Ghana

The Superior Performing Asphalt Pavements (Superpave) system – comprising asphalt binder grading, mixture design and mixture performance evaluation – has been in existence for nearly 30 years and has been implemented or evaluated for possible adoption in several countries to help address fatigue cracking, rutting and thermal cracking. These asphalt pavement distresses minimize pavement integrity to cause significant increase in maintenance cost, safety risks and roughness. Premature fatigue cracking and rutting failures are common in Ghana. Currently, only the mixture design component of the Superpave system is an option in the country's standard construction specification; asphalt binder selection is based on viscosity grading. Recently, very few projects have utilized Superpave-graded binders, and some of the binder grade selections were problematic. The use of Superpave-graded binders on high-volume roads is anticipated to become a common practice in the foreseeable future. However, there is no road agency guidance document on Superpave binder grade selection in Ghana currently, and this study sought to fill the gap. Such a guidance document will facilitate binder grade selection and streamline binder grade selection practices. This study utilized 42 years (1979–2020) of air temperature data collected from 24 weather stations across the country and measured asphalt pavement temperature to evaluate four existing Superpave binder grade prediction models. The model derived from the Long-Term Pavement Performance program better represented Ghana's climatic conditions and suggested the country may be partitioned into two Superpave binder grade selection zones: the Northern Savannah zone and the Transition/Forest/Coastal zone. At 98% reliability level, a binder grade of PG 70–10 was determined for the northern sector and PG 64–10 for the rest of the country. These are base binder grades (based on weather only) which must be adjusted for traffic conditions at the project site. Research should focus on local model formulation for refined Superpave binder grade selection and, during construction, selected binder grades must be verified through laboratory testing. Proper binder grade selection must be supplemented with effective pavement design, construction, axle load control and maintenance for good pavement performance and longevity.

AN EXPERIMENTAL STUDY ON THE PERMANENT STRAIN OF DENSE-GRADED ASPHALT AND POROUS ASPHALT USING UNIAXIAL CYCLIC COMPRESSION TEST WITH CONFINEMENT

This study investigated the permanent strain of dense-graded asphalt and porous asphalt material using uniaxial cyclic compression test with confinement. Based on the test results, the comparison of the permanent strain was carried out. The results showed that the permanent strain resistance of porous asphalt material was better than that of the dense-graded asphalt material. In addition, the use of higher performance-graded asphalt binder improved remarkably the permanent strain resistance of porous asphalt material. The analysis of the two prediction models showed that the power model performed better in prediction of the permanent strain. In future, more studies need to be conducted to investigate the effect of other factors such as moisture, freeze/thaw cycle on the mechanical performance of the porous asphalt material.

Performance-graded asphalt binder selection catalog for asphalt overlays

The selection of a proper asphalt binder grade is an important step toward a long-lasting asphalt pavement. Currently, almost all states in the US are grading asphalt binders using the Performance-Graded (PG) system, which was originally developed for new pavement constructions three decades ago. Nowadays, asphalt overlays rather than new pavement constructions are the predominant work most state Departments of Transportation (DOTs) deal with. The biggest difference between new pavement constructions and asphalt overlays is pre-existing cracks underlying the asphalt overlays, which are not considered in current PG asphalt binder selection catalogs used by many DOTs. Therefore, it is critical to address this practical need for a new PG binder selection catalog suitable for asphalt overlays. This paper employed a calibrated mechanistic-empirical asphalt concrete overlay program (TxACOL) to simulate the reflective cracking performance of 2700 asphalt overlay cases under five climatic conditions, four traffic levels, three overlay thicknesses, three existing pavement types, and fifteen aggregate/binder combinations. Based on the reflective cracking simulation results, two new color-coded binder grade maps were developed – one for asphalt overlays over existing asphalt pavement and another for asphalt overlays over existing jointed plain concrete pavements. Furthermore, a life cycle cost analysis was conducted to confirm the validity of the new binder selection catalog for asphalt overlays. Finally, a revised binder selection catalog was recommended for TxDOT to incorporate asphalt overlays as part of the binder selection process.

Influence of Asphalt Binder Formulation and Source on the Performances of Binders with the Same Continuous PG WALAA S. MOGAWER, ALEXANDER J. AUSTERMAN,

The objectives of this research study were to determine the effects of asphalt binder formulation and source on the performance of binders with the same continuous Performance Grade (PG) using recently developed asphalt binder and mixture tests and provide recommendations, if needed, concerning the following: (1) the effect of asphalt binder formulation and source on performance, (2) the current PG specification and (3) the tests used in this study. Various asphalt binders were formulated so they would have the same continuous high and low PGs which would meet the AASHTO M 320 specifications for a PG 58-28 binder. Other binders were formulated to meet the AASHTO M 320 specifications for a PG 64-28 binder. Thus, there were two target PG’s. Three sources of straight run asphalt binders were obtained, although one source was eliminated because for most of the modifiers obtained for this study, the target PGs could not be met. This showed that whether a continuous PG can be achieved through modification is dependent on binder source and modifier type. The modifiers used in the formulations consisted of two sources of re-refined engine oil bottoms (REOB), aromatic oil, polyphosphoric acid (PPA) and an air-blown asphalt, either alone or in combination. It is believed these modifiers are becoming more commonly utilized to supply the required PG asphalt binders for today’s paving industry. Asphalt binder formulation and source had an effect on fatigue cracking, cohesion, adhestion, moisture susceptibilty and non-load associated cracking even though the binders had closely matching continuous PGs based on high and low temperature properties. They had no effect on rutting performance except when measured by the MSCR, or thermal cracking performance except when measured by the EBBR. In conclusion, not all asphalt binders with the same continuous PG will perform identically in regard to all distresses.

Properties of Pavement Bitumens Assessed Using European and American Approach

This paper compares the different approaches to assessing asphalt binders used in Europe and the Unites States. A series of pavement bitumens is assessed using European standards and also by the Performance Graded Asphalt Binder Specification based on AASHTO MP 1, which was developed as part of the Strategic Highway Research Program (SHRP) in the United States of America. The results show that the European approach places high requirements on the pavement bitumens in relation to their behavior at low-temperatures, while in case of the American approach, the key parameter is fatigue behavior after short-term and long-term aging. It is evident that it is necessary to evaluate properties of pavement bitumens after long-term aging in Europe, too.

Feasibility of ultrasonic measurements for characterizing rheological properties of asphalt binders

Ultrasonic measurement (UM) may provide an inexpensive alternative to sophisticated tests currently used to characterize rheological properties of asphalt binders. This research investigates the feasibility of application of high frequency immersion UM to characterize performance grade (PG) asphalt binders. Nine different PG asphalt binders were selected for this investigation. Short term aged, long term aged and un-aged samples were prepared for ultrasonic measurements. For each binder, velocity (V) and integrated response (IR) of the ultrasonic wave were measured at five temperatures. Mechanical test to obtain rheological properties were also performed on the same asphalt binder grades. Variation of ultrasonic measured parameters with temperature was studied. Correlations between the ultrasonic measurements and rheological properties were explored. Results indicated that ultrasonic velocity of the asphalt binders decreases with increase in their temperature. Modified asphalt binders showed lower velocity compared to un-modified ones.

Selection and verification of performance grading for asphalt binders produced in Jordan

Selection of proper binder is one of the most important factors considered in mixture design. Three different asphalt grading systems are normally used; they are penetration grading system, viscosity grading system and performance grading (PG) systems. PG system is a method of measuring asphalt binder performance; it was originally developed during strategic highway research program in the early 1990s in order to accurately and fully characterise asphalt binders for use in hot mix asphalt pavements. PG system is based on the idea that the properties of an asphalt binder should be related to the conditions under which it is being used. This involves expected climatic conditions, pavement temperature as well as ageing conditions. Performance-graded asphalt binders are selected to meet expected climatic conditions as well as traffic speed and load conditions. Therefore, the PG system uses a common set of tests to measure physical properties of the binder which can be directly related to field performance of the pavement at its service temperatures. In order to adopt the Superpave system in Jordan, it is essential to develop climatic zones for Jordan and to select the proper performance-graded binder to be used in different regions in Jordan. Selection of performance-graded binder is based mainly on the air temperature of the desired location. Several models were used to calculate the pavement temperature. Different reliability levels were used in developing the climatic zones in Jordan. Finally, Jordan was divided into different zones and specific binder type to be used there. On the basis of analysis, binder grade having designation PG 64-10 can be used in most parts of Jordan. The only source for asphalt binders used in the construction of flexible pavements for Jordan's highways and streets is the Jordan Petroleum Refinery (JPR). Typically, the JPR produces two main types of original asphalt binders; these are 60/70 penetration grade asphalt binder and 85/100 penetration grade asphalt binder. On the basis of laboratory test and according to the Superpave asphalt binder classification system, the 60/70 penetration grade asphalt binder can be classified as PG 64-16 and the 85/100 penetration grade asphalt binder as PG 58-16.

Evaluating Foamed Asphalt Stability Using Acoustic Emission Techniques

AbstractThis paper focuses on the feasibility of using acoustic emission (AE) techniques to evaluate stability of foams produced from paving-grade asphalt binders. The study compared asphalt foamability index [expansion ratio (ER) and half-life (H-L)] measurements with AE measurements for the same foamed asphalt produced using a Wirtgen Model WLB 10 S Laboratory Asphalt Foaming Device. Both ER and H-L are used to characterize the suitability of asphalt binders to produce good-quality foamed asphalt binders for pavement construction. However, current methods for determining foamability are considered as empirical, operator-dependent, and cannot be used for continuous monitoring of the foaming process. Two performance-graded asphalt binders, four foaming water contents, and two foaming temperatures were used. Spectral analyses using a test for white noise suggest AE signals resulting from asphalt foaming are not white noise (p-value<0.0001) and therefore could be useful for evaluating foamed asphalt stabili...

Comparison of permeable friction course mixtures fabricated using asphalt rubber and performance-grade asphalt binders

Permeable friction course mixtures (PFC) are special hot mix asphalt (HMA) mixtures that are designed to improve motorist safety and reduce traffic noise (i.e., tire–pavement noise). In terms of pavement structural design and construction, PFC mixtures are typically used as the surfacing course layer where in addition to improving the skid resistance, also serve as the surface drainage layer. This paper compares PFC mixtures designed and fabricated using performance grade (PG) and asphalt rubber (AR) asphalt-binders (or asphalts). The experimental design included assessment of total air voids (AV) content, durability, drainability, stone-on-stone contact, and internal structure of the PFC mixtures fabricated using both AR and PG asphalts; denoted herein as AR–PFC and PG–PFC mixtures, respectively. The analysis conducted provided evidence of differences between AR–PFC and PG–PFC mixtures that suggest the need for differentiation and refinement of the existing specifications to consider these mixtures as independent materials. Future research should, therefore, focus on defining particular specifications for mix design and control for AR–PFC and PG-PFC mixtures.

Effect of Antistrip Additives on Surface Free Energy Characteristics of Asphalt Binders for Moisture-Induced Damage Potential

Abstract In this study, the effect of antistrip additives on asphalt binders was evaluated by both laboratory tests and a proposed chemical model of asphalt binder based on the surface free energy characteristics. Two performance graded asphalt binders, namely, PG 64-22 and PG 70-28 and two amine-based liquid antistrip additives, namely, AD-Here HP Plus and Redicote E-6 were evaluated at different percentages (0.25 %, 0.75 %, and 1.5 %). It was found that 1.5 %AD-Here HP Plus and 1.5 % Redicote E-6 increased the total SFE of PG 64-22 by 67 % and 208 %, respectively. Also, the acid components of PG 64-22 and PG 70-28 are 2.9 dyne/cm and 2.5 dyne/cm, respectively, whereas, the corresponding base components are 0.4 dyne/cm for both. With the addition of 1.5 %. Redicote E-6 in PG 64-22, the acid component of the binder reduced by 92 % and the base component of the binder increased by 1141 %.

Long-Term Performance of Superpave in Specific Pavement Study 9A

As part of the Long-Term Pavement Performance Program, an experiment identified as Specific Pavement Study 9A (SPS-9A) was established to evaluate the long-term performance of the Superpave® mix design methodology. At each project location, three main test sections were constructed, incorporating the conventional agency mix design, the Superpave Level I mix design with a 98% reliability performance-grade (PG) asphalt binder, and Superpave with an alternative PG binder to evaluate rutting or thermal cracking performance. Further supplementary test sections were constructed at most projects to evaluate the use of other PG asphalt binders with the Superpave mix design. This paper provides a performance comparison and paired T-test analysis of the Superpave Level I mix methodology with conventional agency mix methodology based on the SPS-9A experiment test sections. In addition, the performance impact of PG asphalt binder grades and the use of reclaimed asphalt pavement in Superpave was assessed by statistical analysis of field distresses. Field distresses evaluated in the study include fatigue cracking, thermal cracking, and rutting. Although some trends were identified, overall there was no statistically significant difference in performance between the considered PG asphalt binder grades and mix design types. These results would indicate that asphalt binder and mixture properties probably play a larger role in performance than binder and mix design classification. However, because of the level of asphalt binder and mixture property data in DataPave Release 20.0, a more detailed evaluation of binder and mixture properties on performance was not possible.

Municipal Implementation of Superpave Technology

The reconstruction of 30 km of County Road 2 by the county of Frontenac in 1996 provided the opportunity for municipal implementation of Superpave performance graded asphalt binder and volumetric mix design technology. The Superpave surface course asphalt mix was placed over a cold in-place recycled binder course pavement. Placement and compaction procedures were similar to those for conventional asphalt mixes, with the application of a light soap solution to avoid pickup associated with the polymer-modified performance graded asphalt cement on compaction equipment. The Superpave mix properties for trial batches were verified with a Superpave gyratory compactor. Basic mechanistic properties (resilient modulus, resistance to permanent deformation, and resistance to fatigue) of the Superpave surface course mix were determined with the Nottingham asphalt tester. Three long-term performance monitoring test sections were established at representative locations on County Road 2. The test section performance monitoring included visual distress surveys, structural capacity testing with the falling weight deflectometer, and transverse profiles with the digital incremental profiler (Dipstick). Monitoring of the County Road 2 Superpave pavement indicates that, after almost 3 years of service, the pavement has no significant surface distresses and is in excellent overall condition.

Collaborative Evaluations of Low-Temperature Superpave Performance-Graded Asphalt Binders

Superpave developed the specifications and selection of performance-graded asphalt binders to address performance in the field. To facilitate the implementation of Superpave, highway agencies are sharing information and working with industry. Wisconsin, Iowa, and Minnesota have collaborated to develop a joint certification program to streamline the process and promote partnerships with suppliers. The low-temperature grading of the Superpave asphalt binders is of special interest in severe climates. Several projects are examined that have incorporated Superpave asphalt binders, including new construction, reconstruction, overlays on rehabilitated highways, and overlays on existing highways. The projects vary from low-volume highways to high-volume Interstates to an airport in an extremely severe climate. The projects, which have been in place for several years, have been evaluated for their field performance, especially for behavior at low temperatures. The new asphalt binders have been found to increase the resistance to thermal cracking on newly constructed roads and to inhibit reflective cracking on overlays.

Relationship Between Pavement Temperature and Weather Data: Wisconsin Field Study to Verify Superpave Algorithm

Six test sections were constructed on US-53 in Trempealeau County by using different performance-graded asphalt binders to validate the Superpave pavement temperature algorithm and the binder specification limits. Field instrumentation was installed in two of the test sections to monitor the thermal behavior of the pavement as affected by weather. The instrumentation was used specifically to monitor the temperature of the test sections as a function of time and depth from the pavement surface. A meteorological station was assembled at the test site to monitor weather conditions, including air temperature. Details of the instrumentation systems used and analysis of the data collected during the first 22 months of the project are presented. The analysis was focused on development of a statistical model for estimation of low and high pavement temperatures from meteorological data. The model was compared to the Superpave recommended model and to the more recent model recommended by the Long-Term Pavement Performance (LTPP) program. The temperature data analysis indicates a strong agreement between the new model and the LTPP model for the estimation of low pavement design temperature. However, the analysis indicates that the LTPP and Superpave models underestimate the high pavement design temperature at air temperatures higher than 30°C. The temperature data analyses also indicate that there are significant differences between the standard deviation of air temperatures and the standard deviation of the pavement temperatures. These differences raise some questions about the accuracy of the reliability estimates used in the current Superpave recommendations.