Performance Grade Grade Research Articles

Determination of the continuous grade of a binder in the South African performance grade binder specification

A Performance Grade (PG) Bitumen Specification, SATS-3208 (SATS 2019), was developed in South Africa during the period up to 2019. Since that time a period of implementation has begun on selected projects in South Africa. The implementation activities have included testing of data in accordance with the final anticipated standards. Formulation of a national standard is in the final stages and is expected to be published towards the end of 2024. The PG grade is specified using a high temperature number and a minimum temperature number that indicate the climate range within which a bitumen would be expected to perform. For example, a PG64-22 has a high temperature of 64°C and a minimum temperature of -22°C, from which intermediate and low operating temperatures are derived. A material meeting this grade will always have a performance range which is, ideally, just bigger than the specification grade and this is typically referenced as the continuous grade. A further definition is the difference between the two continuous grade numbers, referenced as the "Useful Temperature Interval" or UTI. As part of this implementation, it is required to determine the continuous grade for bitumen, including for modified binders, to ensure compliance with the specification. The UTI must be equal to or greater than 80°C. This technical note has been developed to demonstrate correct procedure to determine the continuous grade and UTI.

Multiple Stress Creep Recovery (MSCR) Test for Determination of Waste Engine Oil Modified Asphalt Binder as Pavement Material

Engineers have been using modified binders to improve the quality of flexible pavements. The use of waste material is one of the solutions taken in this direction. It is for this ground that the studies emphasis on the evaluation of waste engine oil as a modifier for asphalt binder as a pavement material. In the study uses four samples extracted from 80/100 penetration grade bitumen. From four sample first sample was checked for weather requirements of asphalt binder meet or not and the three were modified with different content of engine oil (3,6 and 9%). The behaviors of both unmodified and modified binder were checked for rheological properties. Dynamic shear rheometer (DSR) was used to determine high temperature performance grade (PG) and multiple stress creep recovery tests to determine rutting resistance properties of the binder. PG analysis indicates that both aged and un-aged 3% and 6% modified binder have similar higher PG grade with the unmodified one and 9% modified to have lower PG vale. Jnr3.2 value of modified asphalt binder is lower than unmodified binder indicating that modification had improved the rutting resistance and design traffic load (ESALS). The study shows that it is possible to use waste engine oil-modified binder as a pavement material.

Evaluation of Low- and Intermediate-Temperature Performance of Bio Oil-Modified Asphalt Binders

Fatigue cracking and low-temperature cracking are two major distresses that occur in asphalt pavements. Fatigue cracking is a load-associated distress caused by the tensile stresses at the bottom/top of the asphalt concrete (AC) layer due to repeated traffic loading. On the other hand, low-temperature cracking occurs when tensile stresses built up with in the AC layer at low temperatures exceed the tensile strength of that layer. In this study, the performance of date seeds oil bio-modified asphalt binders (DSO-BMB) is evaluated against fatigue and low-temperature cracking. The DSO-BMBs are prepared using volume ratios of 1.5, 2.5, 3.5, 4.5, and 5.5% date seeds oil-to-asphalt binder. The base asphalt binder used in the study is a 60/70-penetration grade with a Superpave performance grade (PG) of PG 64–16. The dynamic shear rheometer (DSR) standard test was used to assess the fatigue performance of the bio-modified binders (BMBs), while the bending beam rheometer (BBR) test was used to test the BMBs for low-temperature performance. In addition, the DSR linear amplitude sweep (LAS) test was used to evaluate the fatigue tolerance behavior of the DSO-BMBs. The analysis and results of the study showed that the bio-oil enhanced the low-temperature performance. The low PG grade improved from −16 °C for the control asphalt binder to −28 °C for the BMB. Additionally, the fatigue resistance of the BMBs was improved as illustrated by the damage–characteristic curves of the modified asphalt binders from the visco-elastic continuum damage (VECD) analysis and the increase in the number of cycles to fatigue failure (Nf).

Field implementation of WMA mixtures containing recycled asphalt shingles (RAS)

Combining Warm Mix Asphalt (WMA) technology with another green technology (asphalt recycling) can lead to a double saving in total cost of asphalt paving production. In this study, field implementation of Hot Mix Asphalt (HMA) with Recycled Asphalt Shingles (RAS) and WMA mixture containing RAS was performed and both mixtures were tested at asphalt laboratory for performance evaluation. To analyze binders and mixtures performance, Fourier-Transform Infrared (FTIR) Spectroscopy test, block cracking test, rutting and moisture resistance (Hamburg Wheel Tracking) test, thermal cracking potential (Disc-Shaped Compacted Tension) test were conducted. A short and medium-term field evaluations were also carried out. Binder extracted from mixtures constructed with and without WMA additive showed the same Performance Grade (PG); however, the extracted binder from WMA mixture was a little softer than the binder extracted from HMA but not enough to bump down the PG grade. Based on sulfur and carbonyl indexes calculated from FTIR test results, WMA mixture found to be more aged. No block cracking was observed in HMA and WMA mixtures by determining G-R values and developing block cracking black space chart. HWT results showed that using WMA technology in asphalt mixtures containing RAS resulted in a relatively better moisture and rutting resistance. The DCT results indicated almost the same fracture energy for both mixtures. The short-term field evaluation after one year of construction showed that the overall condition of both HMA and WMA sections are satisfactory. However, medium-term evaluation (after 39 months) showed more traverse cracks and stripping in WMA mixture.

Prediction of Dynamic Modulus of Hot Mix Asphalts with Reclaimed Asphalt Pavement

This study evaluated the viscoelastic properties of a performance grade (PG) binder blended with different percentages of binders recovered from reclaimed asphalt pavement (RAP) for conditions (materials, climate, and specifications) prevailing in Oklahoma. The viscoelastic properties of the blended binders were then used to estimate dynamic modulus (E∗) values of the new mixes with RAP by using the Witczak model through time‐temperature superposition (TTS) principles. The recovered binder from RAP was found to be significantly stiffer than the virgin binder (PG 64‐22). The addition of RAP increased the complex modulus (G∗) of the base binder, so did the E∗ of the corresponding mix. The creep stiffness resistance of the asphalt binder at low service temperatures decreased with the addition of RAP. With up to 10% RAP binder, no notable changes were observed in the viscosity and PG grade of the virgin binder. With 25% and 40% RAP binder, the PGs of the blended binders were found to be PG 70‐16 and PG 76‐16, respectively. It was observed that the E∗ master curves predicted from PGs of the blended binders were in close agreement with those estimated from the laboratory‐measured E∗ data. The dynamic shear rheometer (DSR) data of rotational thin film oven (RTFO)‐aged blended binders predicted significantly lower E∗ values compared to the measured ones. The E∗ values predicted from rotational viscosity (RV) test data were found to be higher than the measured E∗ values. The findings of this study are expected to provide transportation professionals with a better understanding of new mixes with high RAPs.

Chemical, rheological and aging characteristic properties of Xinjiang rock asphalt-modified bitumen

Recently, rock asphalt has been widely used to modify bitumen binder; however, limited studies have been conducted to comprehensively evaluate the chemical, rheological and aging characteristics of bitumen modified with Xinjiang rock asphalt (XRA) from China. In this study, base bitumen (K64) was added with 0%, 8%, 12%, 16% and 20% XRA by mass respectively to prepare different modified binder, and rolling thin-film oven (RTFO) and pressure aging vessel (PAV) tests were performed to simulate short-term and long-term aging, respectively. The evolution of the chemical and rheological characteristics of the binders before and after aging were monitored with Fourier transform infrared (FTIR), rotational viscosity, dynamic shear oscillatory, frequency sweep, multiple stress creep recovery (MSCR) and bending beam rheometer (BBR) tests. Furthermore, several empirical indexes were tracked with softening point, ductility and penetration tests. The FTIR results indicated that with the introduction of the XRA modifier, the carbonyl functional group of the binders was reduced after aging, and the carbonyl index was more stable than the sulfoxide index to characterize the aging extent of the XRA-modified bitumen binders. Moreover, the rheological and empirical indexes suggested that the XRA could reduce excessive plastic deformations at high temperatures and broaden the final performance grade (PG) of the binder, while a high XRA addition ratio could compromise the low-temperature stress relaxation properties of the bitumen. Additionally, principal component analysis (PCA) suggested that ten parameters employed in this paper (such as stiffness, PG grade, percent recovery and etc.) have similarity and can be explained by two variables: PG grade and carbonyl index. Generally, based on the above evaluations and selection sort algorithm, 12% XRA was the optimum dose for modifying K64 to exhibit the best performance.

Enhancement of permanent deformation resistance of modified asphalt concrete mixtures with nano-high density polyethylene

The present research was carried out to inspect the influence of Nano-High Density Polyethylene (Nano-HDPE) particles and Styrene-Butadiene-Styrene (SBS) on the rheological characteristics of modified asphalt binders and performance of modified asphalt concrete mixtures. In this study, the base asphalt binder of the PG (64-16) grade was modified with Nano-HDPE and SBS polymers at a concentration of 3% and 5% by weight of total asphalt binder content. The Superpave dynamic shear rheometer (DSR), rolling thin film oven (RTFO), rotational viscosity (RV), pressure aging vessel (PAV) and bending beam rheometer (BBR) were conducted to evaluate performance grade of base and modified asphalt binders, also gyratory compactor was used to find optimum asphalt content. Roller compactor and wheel track tests were utilized to assess the rutting performance of modified asphalt mixture with Nano and SBS polymers, and the Indirect Tension Test (IDT) was used to assess the strength of mixtures before and after water conditioning. The results of the study show that Nano-HDPE particles have a considerable influence on improving Performance Grade (PG) of the binder, but at an equal concentration of polymer, it is not as effective as the SBS. However, the HDPE shows a significant advantage in keeping the viscosity of the modified binder at significantly lower levels and thus allowing much lower mixing and compaction temperatures as determined by the equ-viscous standard procedure. Although the PG grades of the binders showed the SBS to be more effective in improving the high-temperature grade than the HDPE, the mixture rutting performance shows that the HDPE modified binders provide better rutting resistance at 3% and 5% than the SBS modified binders. This finding shows that binder testing of G*/sin δ only could give a misleading indication of the true contribution of modified binders to rutting resistance as polymers could improve mixtures in different mechanisms than what is measure with binder PG testing. The IDT testing also shows that the strength of the mixtures produced with the modified binders at 25 °C is superior to the control mixture, with the HDPE providing slightly higher strength values before and after water conditioning. The overall results of the study show that HDPE can be used as a viable modifier requiring lower mixing and compaction temperature and equal or significantly better rutting and strength performance than conventional SBS Modifier. The study also highlights the need to check mixture performance when using specialty modifiers and not depend on only DSR testing as specified in the Superpave PG grading.

Investigating High-Temperature PG Grade Adjustment Recommendations for Airfield Pavements

This study aims to investigate the high-temperature performance grade (PG) adjustment (bumping) recommendations included in various international specifications and guidelines for airfield pavements, particularly for asphalt intermediate and base layers. The research was instigated following recent asphalt rutting occurrences in airport pavements. Mechanistic analysis, using the software FlexPave™, was employed to assess airfield pavement responses under hot climatic conditions and for different loading conditions. The results of the analysis pointed to three important factors that should be considered when selecting binder PG grades for airfield pavements, particularly for the asphalt intermediate and base layers: (1) deeper layers within an airfield pavement structure are subjected to considerably high compressive stresses; (2) deeper layers within an airfield pavement structure are subjected to longer loading times compared with surface layers; and (3) deeper layers within a pavement structure experience consistently high temperatures. Therefore, it is recommended that PG grade bumping be applied beyond the surface layer in airfield pavements, to the intermediate and base layers, in locations that experience very high temperatures and where rutting is a critical distress. This recommendation was supported by two case studies of airfield pavements in hot climates, where the one that applied PG grade bumping for the base layer performed well under heavy loading, while the one that did not apply PG grade bumping experienced premature rutting failure.

Comparative Evaluation of WMA Additives Effects on Conventional and Polymer Modified Asphalt Pavements

This study is mainly focused on the evaluation of the effect of Warm Mix Asphalt (WMA) additives on the performance grade of straight and polymer modified asphalt binder and the performance of asphalt mixtures. In order to analyze these effects, the Performance Grade (PG) of asphalt binder and the degree of compaction of WMA mixtures with various additives were examined initially. Moreover, the degree of compaction was evaluated in field test sections. Lastly, the effect on WMA performance were evaluated using wheel tracking test and indirect tensile (IDT) strength test for the rutting resistance, moisture susceptibility and crack resistance, respectively. Based on the laboratory and field test results, it can be concluded that WMA additives can affect the PG grades of conventional but not for polymer modified asphalt binder while viscosity related to mixing and compaction results in conversely. From the field test, the rutting and crack resistances of WMA pavements are higher than HMA pavements in most cases.

Investigation of rheological properties and Superpave PG of PMB mixed with reclaimed asphalt pavement binders

The present study was undertaken to evaluate the effects of two types of reclaimed asphalt pavement (RAP) binders on rheological properties and Superpave performance grade (PG) of a styrene-butadiene-styrene (SBS) co-polymer modified binder (PMB). Two RAP materials: one from urban highway (RAP-A) and other from rural highway (RAP-S) were collected in the study. The asphalt binder extracted from RAP-A and RAP-S had different viscosity, rheological and chemical characteristics. The asphalt binder extracted from RAP-A was found to be stiffer compared to the binder obtained from RAP-S. The PMB was blended with different proportions (i.e., 0, 15, 25 and 40% by weight of binder) of RAP-A and RAP-S binders. Different physical tests, namely penetration, softening point, viscosity, ductility and elastic recovery were conducted on PMB blended with the RAP binders. In addition, high and low temperature Superpave PG of PMB with RAP blended binders were determined based on dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests, respectively. The results from physical properties of asphalt binders showed that addition of RAP binders adversely affected performance of PMB. Both type of the RAP binders had difference influence on physical properties of PMB. Addition of 15% of RAP bumped PG of PMB by one grade interval (i.e., from PG76 to PG82). The maximum grade bump for high temperature PG was found to be one grade interval even after addition of 40% RAP. The low PG grade did not change with addition of the RAP binders. Statistical analyses were conducted to compare effects of two types of RAP binders on properties of PMB. Overall the results showed that type of the RAP binder can have different influence on consistency and Superpave PG of PMB, thus caution should be taken during selection of grade of a base binder.

Effect of climate change on asphalt binder selection for road construction in Italy

This work explores the influence of climate changes on the proper selection of asphalt binder for pavement construction purposes, according to the Performance Grade (PG) defined in the SUPERPAVE specifications. Based on temperature data at national level, it is possible to obtain thematic maps for the whole Italian territory, which is extremely useful for technicians and pavement engineers for selection of asphalt binder for road construction purposes. Furthermore, the statistical significant temperature trends’ knowledge enables deriving thematic maps which allows to include the effects of climate change in the asphalt binder design. It is argued that, due to climate change, the binders to be selected may be different from those commonly selected at the design stage of the infrastructure, since likely higher temperature determine more demanding constraints. The comparison among the PG grades necessary for covering the needs for construction in the different regions of Italy also call for highly performing binders, such as those obtained via specific modification with polymers. This will also imply the need for even more performing materials, in terms of mechanical properties and durability, to be used for modification of neat asphalt as well as the need for defining new specification and testing methods, specifically valid for these modified materials.

Impacts of lubricating oils on rheology and chemical compatibility of asphalt binders

Modifiers have been widely used to improve the engineering value of asphalt binders and the performance characteristics of asphalt mixtures. In recent years, a wide range of oil-based modifications have been introduced to improve asphalt binder performance, with the enhancement of the low-temperature characteristics as the specific goal. Using oil modification was found to improve the Superpave low-temperature performance grade (PG), but at the expense of the high-temperature PG grade. This paper studies different combinations of lubricating oils and also hybrid systems of polymers and lubricating oils in order to improve characteristics of seven different types of neat binder and also satisfy the needs for covering the required PGs. The laboratory performance of binders was evaluated in three main categories based on the temperature range of interest (i.e. high, intermediate and low service temperatures) using Superpave testing, damage characterising tests and chemical compatibility using gel permeation chromatography. Oil modification showed to be significantly effective in improving the rheological properties of modified binders across all performance temperature ranges specifically when they are applied in hybrid systems with polymers.

Temperature Zoning of Libya Desert for Asphalt Mix Design

The current asphalt binder specifications in Libya are based on the Penetration Grade: penetration test is performed at 25°C. Penetration is an empirical measure of the consistency that is used as an empirical indicator of the rutting and fatigue susceptibility of asphalt binder, and is not related to pavement performance. The new mix design methodology developed under the Strategic Highway Research Program (SHRP), called the SUPERPAVE is a performance-based approach. The first step in the implementation of SUPERPAVE methodology is to establish high and low pavement temperatures for a location. The temperatures define the required Performance Grade (PG) of asphalt binder. This paper documents the initial ground work towards implementation of SUPERPAVE mix design for establishing high and low geographical temperature zones. The temperature zoning of Libya was carried out by using temperature data obtained from 8 weather stations. The SHRP and LTPP prediction models were utilized for predicting pavement temperatures. A significant difference was observed between the predicted pavement temperatures from both the models. The SHRP model gives higher, high temperature PG grade providing additional protection against rutting. Since rutting is the most common distress on flexible pavements in Libya , the SHRP models at 50% level of reliability is recommended. The PG of roads that located in Libyan desert are classified to three zones (PG70-10, PG76-10 and PG82-10.PG 76-10 binder seems to be the most common grade that encompasses more than 70% area of Libya desert .However, currently none of the two local refineries produce the bitumen under penetration grade 60-70,that grade equivalent to PG 82-10 binder, thus it should be a concern for highway or the project location. The polymer modified asphalt binder are not produced by Libya refineries.

An evaluation of the suitability of SUPERPAVE and Marshall asphalt mix designs as they relate to Thailand’s climatic conditions

The most commonly-used asphalt mix design in Thailand still relies on the Marshall Mix design procedure which is empirical in its nature, in the sense that it is based on data produced by experiment and observation rather than reliable “in-field” data. As a result of this, the Marshall Mix design procedure has substantial drawbacks with respect to replicating the real or actual behaviour of asphalt during construction and in actual in-service conditions.The Strategic Highway Research Program (SHRP) has developed the Superior Performance Asphalt Pavements (SUPERPAVE) mix design procedure, which shifts to a large degree away from the empiricism of the Marshall Mix design to provide a more reliable and responsive solution to actual pavement conditions.This study aims to evaluate whether the SUPERPAVE mix design procedure can be reliably implemented under Thailand pavement conditions. A map of the Performance Grade (PG) asphalt binders was generated to cover the study area, namely the North part of Thailand, according to the SUPERPAVE asphalt classification with the highest and lowest temperature ranges that the asphalt might be subjected to. Using local materials, and considering loading and environmental conditions, a comparative study of the performance of two mixes, designed using SUPERPAVE and Marshall Mix design procedures, was carried out.The SUPERPAVE mixes proved superior to the Marshall Mixes. However, the asphalt binder commonly used in Thailand is not suitable for Thailand pavement conditions, based on the PG grade asphalt classification system.

Investigation of Moisture Dissipation in Foam-Based Warm Mix Asphalt Using Synchrotron-Based X-Ray Microtomography

Foam-based Warm Mix Asphalt (WMA) technologies decrease the viscosity of the asphalt so that it is workable during construction. However, after construction, viscosity increases rapidly as the foam disappears and temperature drops. During the process of dissipation of foam, depending on the environmental conditions, the moisture may not escape and may be trapped inside the mixture. This trapped moisture can cause detrimental failures by breaking the adhesive bonds between the aggregates and the asphalt binder (because of diffusion and freeze/thaw cycles). It is crucial to know how the moisture escapes from the asphalt mixture as the specimen cools down and foam disappears. In this research, dissipation of the moisture from foamed asphalt binders was directly measured and quantified by using a high-resolution synchrotron-based X-Ray Microtomography (XRM) system. Different foamed asphalt binders were instantly frozen by using liquid nitrogen at different times after the initial foaming. The 3D internal structure images of these specimens were acquired by using XRM available at the Argonne National Laboratory (ANL). These images were analyzed and the moisture dissipation processes in different types of asphalt binders were directly quantified. It was observed that the rate of moisture dissipation in high performance grade (PG) (stiff) binders was slower than that of low PG grade (soft) binders. It was also observed that the size distribution of moisture bubbles in the binders varied in different binders.

Asphalt modification with used lubricating oil

The viability of used lubricating oil as an asphalt modifier was studied, with the enhancement of the low-temperature grade as the specific goal. Used oil modification was found to improve the Superpave low-temperature performance grade (PG), but at the expense of the high-temperature PG grade. When evaluated according to the Superpave MP1 specification, the low-temperature grade of the modified asphalt was not significantly improved due to failure of the bending beam rheometer (BBR) test’s m value. When evaluated according to the Superpave MP1a specification, the modified asphalt overall PG grade temperature spread remained essentially constant, varying only by approximately two degrees. The asphalt took as much as 12% of oil and still had less than the maximum limit of 1.0% rolling thin film oven test (RTFOT) mass loss (emissions). However, the oil may possibly have a detrimental effect on the asphalt quality, such as reduced adhesiveness to the aggregates, leading to stripping and raveling. The field performance test should be checked before considering lubricating oil as a modifier.

Adapting Superpave Technology to Design of Hot Recycled Mixes

Abstract Mix design procedures for recycled asphalt pavements require the selection of virgin asphalt or recycling agent and recycled hot mix asphalt (HMA) mix design. This research project was undertaken (a) to develop a procedure for selecting the performance grade (PG) of virgin asphalt binder based on the Superpave PG grading system and (b) to design hot recycled mix using Superpave technology. Blending charts were constructed and used to select the PG grade of virgin asphalt binder for mixes with 0, 20, 30, and 40 percent of recycled asphalt pavement material (RAP). Superpave volumetric mix design were conducted on mixes with 0, 20, 30, and 40 percent RAP. Evaluation of the volumetric properties of these mixes has indicated that the Superpave volumetric mix design procedures can be adapted to design recycled HMA mixtures with minimal modification.