Virgin Binder Research Articles

Laboratory Investigation of Different Standards of Phase Separation in Crumb Rubber Modified Asphalt Binders

AbstractThe phase separation between polymer additives and virgin asphalt binders during hot storage is an important issue in the asphalt industry. Traditionally, it has been customary to evaluate the degree of phase separations in polymerized asphalts by laboratory testing, such as the cigar tube test (CTB). However, the test circumstances, temperature, and storage time vary depending on different standards used in many countries. Based on a comprehensive literature review, the range of temperatures and oven storage times were selected to be 140–180°C and 2–7 days, respectively. The phase separation of 11 storage stability conditions selected from 12 different places using crumb rubber modified asphalts (CRMAs) were compared and evaluated in this study. The CRMAs produced in the laboratory were made with PG 64-22 virgin binder and ambient crumb rubber with various concentrations (10, 15, and 20% by weight of virgin binder). The CTB was used as the storage stability test method, and percent separation was...

Partial replacement of asphalt binder with bio-binder: characterisation and modification

This paper introduces bio-binder as a partial replacement for bituminous binder on highway and airport pavements. The proposed bio-binder is produced from the thermochemical conversion of swine manure. Bio-binder is then blended with virgin binder to produce bio-modified binder (BMB). In addition to being a renewable alternative for petroleum-based binder, the production and application of bio-binder may provide a solution for the management of swine manure waste. Furthermore, the application of bio-binder will improve asphalt binder's properties while reducing asphalt pavements' construction cost; the cost of bio-binder production is $0.54/gallon compared with that of asphalt binder $2/gallon. However, although the BMB has improved low-temperature properties, it may decrease the high-temperature grade of the binder. To address this concern, we in this paper investigate the feasibility of applying polyphosphoric acid into BMB. Using BMB in asphalt pavements can reduce mixing and compaction temperatures and ageing and stiffening characteristics of the reclaimed asphalt pavements (RAPs) and virgin binders.

How to Construct an Asphalt Binder Master Curve and Assess the Degree of Blending between RAP and Virgin Binders

The master curve of an asphalt binder provides a relationship between the binder stiffness and reduced frequency over a range of temperatures and frequencies. Accordingly, the master curve makes it possible to predict viscoelastic properties over a wide frequency range and also to predict viscoelastic properties at any temperature. To construct a master curve, the stiffness of an asphalt binder at multiple temperatures and frequencies is measured. The data are then fitted into a viscoelastic model applied to asphalt binders. Recently, a methodology has been developed that utilizes the measured dynamic modulus of a hot-mix asphalt (HMA) mixture and the master curves for the as-recovered binders to determine the degree of blending between aged and virgin binders in asphalt mixtures that incorporates recycled materials. This study presents the methodology for constructing asphalt binder master curves in a step-by-step format. The study also describes in a step-by-step format the methodology for evaluating the degree of blending between aged and virgin binder. Furthermore, to clarify the method and elaborate on the analysis of experimental results, plant-produced mixtures containing different percentages of recycled asphalt pavement (RAP) were obtained and tested. The test results were used to develop the master curves and examine the degree of blending by the aid of the methodology explained in the paper.

Application of Slow Curing Bitumen as a Rejuvenating Agent in Aged Bituminous Mixes

Recycling of bituminous mixes is extending worldwide with the aim of conserving natural resources and the environment. Rejuvenating agents are generally used in recycling processesin order to soften the aged binders in mixes. Cutback bitumens have been used in Iran mainly in preparing conventional cold mixes. However, the long term good performance of these cold mixes in various parts of the country has shown less hardening of these mixes, compared with conventional HMA mixes. In this research the application of a cutbackbitumen has been investigatedas a rejuvenating agent in mixes containing laboratory aged binders. A 60-70 penetration grade bitumen from Refinery of Tehran was aged under Thin Film Oven Testing (TFOT) conditions. Asphalt Concrete samples were prepared using TFOT aged and virgin binders. Additional samples were prepared using the aged binders together with various amounts of a slow curing SC-250 cutback bitumen from the above refinery. The compacted four inchdiameter samples were tested under static creep testing. The results showed promising effects of the cutback binder in rejuvenating the aged mixes. Based on the results of this study, a mix design criteria wasset for recycled mixes containing cutback bitumen as the rejuvenating agent.

Experimental investigation of the homogeneity of the blended binder of a high rate recycled asphalt

Nowadays, with the increasing material costs and the environmental needs to reduce energy consumption and greenhouse gases emission, the technique of asphalt recycling becomes more and more used in the road industry. To ensure the performance of recycled asphalt, a quality control of the bituminous mixture is required. In this context, this work was carried out within the framework of a partnership between the IRC/ESTP and the company Eurovia. In this paper, we present an experimental approach to characterise the level of blending of the binder from reclaimed asphalt pavement (RAP) in hot recycled bituminous mixture. First, a series of laboratory tests are performed on asphaltic concrete including 70% of RAP to extract the bituminous binder mixture using an appropriate solvent. This leads to define an appropriate progressive extraction procedure that allows a regularly stripping of the recycled concrete (three solutions containing about 30% of the bituminous binder). Then, both conventional tests and infrared spectroscopy analysis are performed in order to quantify the evolution of the RAP and virgin binders mass proportions during the stripping process. The experimental results show a “bad” remobilisation of the virgin bitumen in the blended binder of the hot recycled bituminous mixture. This finding correlates with the hypothesis of the “heterogeneous asphalt” considered during the manufacture process.

Stiffness of High-RAP Asphalt Mixtures: Virginia’s Experience

In the year 2006, the price of asphalt binders in the United States increased by almost 50% over the 2005 prices. The use of higher recycled asphalt pavement (RAP) percentages with locally available binders was adopted as an approach to reduce the demand on specialty more expensive virgin binder and virgin aggregates in Virginia. The purpose of this study was to investigate concerns that the performance of these higher RAP mixtures could be compromised because of excessive mixture stiffening due to the aged RAP binder. The results indicated that measured binder stiffnesses of high-RAP mixtures are not significantly affected by RAP amount, high temperature true grade of high-RAP mixtures averaged only approximately 2.0°C above that of base virgin binder, and that the correlation between binder stiffness and flow number for the selected high-RAP mixtures considered was good. The study concludes that the addition of higher amounts of RAP to asphalt-concrete mixtures currently produced in Virginia has not resulted in excessively stiffened mixtures as previously thought; the stiffnesses of high-RAP mixtures are primarily governed by the virgin binder stiffness.

Observation and evaluation of the degree of blending of reclaimed asphalt concretes using microscopy image analysis

In order to contribute to the protection of the environment, asphalt concrete is produced incorporating a high percentage (70%) of reclaimed materials from the deconstruction of road surfaces under renovation. In this paper we propose a microscopic observation technique to appreciate the way the virgin binder and the reclaimed asphalt pavement binder blend together. This technique is applied to compacted samples. Quantitative indicators are proposed to characterise the properties of the blend of binders and quantify the influence that production parameters, materials temperature and mixing time, have on the disappearance kinetics of the reclaimed asphalt pavement binder clusters initially present.

Performance characteristics of plant produced high RAP mixtures

The main focus of this study was to obtain plant produced Reclaimed Asphalt Pavement (RAP) mixtures, to document the mixture production parameters and to evaluate the degree of blending between the virgin and RAP binders. The effect of mixture production parameters on the performance (in terms of stiffness, cracking, rutting, and moisture susceptibility) and workability of the mixtures was evaluated. Eighteen plant produced mixtures were obtained from three locations in the Northeast United States. RAP contents (zero to 40%) were varied and softer binders were used. The data and analysis illustrated that the degree of blending between RAP and virgin binders is a function of production parameters. The stiffness of the mixtures increased as the percentage of RAP increased, but not when the discharge temperatures of the mixtures were inconsistent. The cracking resistance was reduced as the percentage of RAP increased. The rutting and moisture damage resistance improved as the percentage of RAP in the mixtures increased. Finally, reheating the mixtures in the laboratory caused a significant increase in the stiffness of the mixtures.

Effects of reclaimed asphalt pavement content and virgin binder grade on properties of plant produced mixtures

This paper presents the results of a study to evaluate the mixture properties of plant-produced asphalt mixtures containing up to 40% reclaimed asphalt pavement (RAP). Five sets of asphalt mixtures were tested to determine their dynamic moduli and low temperature tensile creep compliance and strength. The mixture moduli were analyzed to assess changes in mixture behavior over a range of temperatures (frequencies) and in combination with extracted binder properties to analyze the extent of binder blending in the mix. The low temperature test results were analyzed to predict the critical cracking temperature of the mixtures. The results suggest that, for these materials, up to 25% RAP could be added to the mix with no change in the virgin binder grade without detriment to the low temperature properties of the mix.

Evaluation of moisture sensitivity of stone matrix asphalt mixtures using polymerised warm mix asphalt technologies

The present study is focused on using warm mix asphalt (WMA) technology in stone matrix asphalt mixtures and investigated in detail on the moisture sensitivity of these mixtures using three different types of WMA technologies. The experimental design involved three sources of aggregates (A, B and C) and three WMA technologies using additives Asphamin®, Sasobit® and Evotherm® technology. Test results indicated that 13 mixtures failed to meet the minimum tensile strength ratio requirement of 85%, and all mixtures tested met the minimum wet indirect tensile strength (ITS) value of 448 kPa (65 psi) as per SCDOT specifications. Statistical analysis showed that there was significant difference in the wet ITS values between aggregate A (micaceous granite) and granite (C) for all the mixtures studied. Statistical analysis showed that except for two mixtures, there were no significant differences in the wet ITS values of WMA mixtures amongst four types of mixtures under identical conditions. The mixtures containing over 15% rubber (by weight of virgin binder) produced similar resistance to moisture susceptibility compared with mixtures made with PG 76-22+fibres.

Factors Affecting the Measurement of Effective Specific Gravity for Reclaimed Asphalt Pavement

Proper use of high amounts of reclaimed asphalt pavement (RAP) in recycled asphalt mixtures requires a better understanding of RAP properties before mix design to ensure confidence that RAP properties are not changed by the mix design or asphalt production process. This paper presents the results of an investigation into the measurement of effective specific gravity of RAP and if RAP has any propensity to absorb additional asphalt during mix design or production. Factors of heating time, heating temperature, warm mix additives and amount of virgin asphalt added to RAP were investigated. The factors included two warm mix additives, three mixing temperatures, three asphalt contents and three RAP sources for a total of 34 test conditions and 68 tests. Results indicate that RAP does not absorb noticeable amounts of virgin asphalt or existing RAP asphalt during mix design or under approximate production conditions. A proposed method to improve measurement simplicity for the effective specific gravity of RAP by first coating RAP samples with 2% virgin binder is also discussed.

Determining the Influence of Plant Type and Production Parameters on Performance of Plant-Produced Reclaimed Asphalt Pavement Mixtures

The purpose of this research study was to evaluate the effects of plant type and production parameters on the stiffness, performance, and degree of blending between the aged and virgin binders of plant-produced reclaimed asphalt pavement (RAP) mixtures. Mixtures from a batch and a drum plant and the corresponding production information were obtained. The stiffness of each mixture was evaluated by measuring the dynamic modulus. Moisture susceptibility and rutting potential were evaluated with the Hamburg wheel tracking device. Low-temperature cracking characteristics were evaluated with the asphalt concrete cracking device. Finally, the workability of the mixtures was evaluated with an asphalt workability device. Binder was extracted from each mixture to measure the degree of blending between the aged and virgin binder. The degree of blending between the aged RAP and virgin binder in each mixture was evaluated with an analysis approach that used the ratio of the mixture dynamic modulus to the recovered binder shear modulus. Batch and drum plants produced RAP mixtures that performed similarly to the control mixtures and exhibited good blending. None of the RAP mixture tested showed increased susceptibility to moisture damage, rutting, and low-temperature cracking susceptibility as the RAP content was increased. Workability testing identified a potential construction issue as the mixture workability decreased as the amount of RAP in the mixture increased. Finally, the performance data indicated the importance of the proper virgin binder grade selection for mixtures with higher amounts of RAP.

Effects of Long-Term Oven Aging on Reclaimed Asphalt Pavement Mixtures

As the use of reclaimed asphalt pavement (RAP) in asphalt concrete mixtures increases, it is important to understand how the addition of asphalt binder that has already been aged affects the overall properties and performance of the mixture. In this study, four plant-produced mixtures containing 0%, 20%, 30%, and 40% RAP were aged long-term in an oven in the laboratory to three levels. The dynamic modulus was measured for each aging level and compared with unaged values to determine whether there was a statistical difference. It was found that as RAP content increased, aging had less effect on stiffness; this finding was quantified with areas under the dynamic modulus curves and aging ratios. The greatest differences were observed at the high-temperature and low-frequency ranges. The study also showed that the slope of relaxation modulus was less affected by aging as RAP content increased. The Global Aging System (GAS) was used to predict the change in dynamic modulus over time with the virgin binder properties. This method overpredicted the measured changes in stiffness. The GAS was also used to predict how many months of service life were simulated for each mix by long-term oven aging. It was found that as RAP content increased, hot-mix asphalt mixes stiffened at a slower rate than virgin mixes.

Long-term ageing influence on rheological characteristics of asphalt binders containing carbon nanoparticles

Nano-sized particles have been used in numerous applications to improve properties of various materials. The utilisation of nanotechnology in civil engineering area is relatively new and its use and applications are expected to increase rapidly. The objective of this study was to investigate and evaluate the rheological properties of binders containing various percentages of carbon nanoparticles after a long-term ageing process. The experimental design for this study included the utilisations of five binder sources (three grades of PG 64-22, PG 64-16 and PG 52-28) and four nano percentages (0.0, 0.5, 1.0 and 1.5% by weight of the virgin binder). The rheological characteristics of these pressurised aged vessel (PAV) binders were tested including G* value, creep and creep recovery, and frequency and amplitude sweep at an intermediate temperature and deflection, stiffness and m-value at a low temperature as well. The results of the experiments indicated that the addition of nanoparticles does not increase the G* values and does have an obvious effect on complex modulus, phase angle under a frequency sweep test. However, nanoparticles have a slight effect on creep angle and compliance of a binder. Moreover, at a low tested temperature, the experimental results indicate that the nanoparticles have no effect on deflection, stiffness and m-value of PAV residue. Furthermore, statistical analysis indicates that the asphalt binder source and grade rather than nanoparticles play a key role in determining the rheological properties

The properties of asphalt binder blended with variable quantities of recycled asphalt using short term and long term aging simulations

The objective of this paper is to characterize the rheological properties of asphalt binders blended with various amounts of asphalt extracted from a recycled asphalt pavement (RAP) mixture. Three asphalt binder aging states were simulated and evaluated: unaged, rolling thin film oven (RTFO) aged, and pressure aging vessel (PAV) aged. A Superpave PG 58-28 binder was applied as control binder and another four RAP binder percentages were studied in this research, 30%, 50%, 70% and 100%. Rotational viscosity testing was conducted with a Brookfield viscometer. Temperature and frequency sweep tests were conducted using a dynamic shear rheometer. Master curves were constructed based on the dynamic shear moduli ( G ∗). The results showed that there are significant differences in dynamic shear moduli ( G ∗) master curve performance for high percentage RAP binder blends versus virgin binders at the three aging states. Increasing RAP concentration and further aging conditions contribute to the increased stiffness and viscosity of RAP binder blends.

Performance Evaluation of Recycled PMA Binders Containing Warm Mix Asphalt Additives

Abstract The performance properties of recycled polymer modified asphalt (PMA) binders containing warm mix asphalt (WMA) additives at high, intermediate, and low temperatures were evaluated. First, each combination of two PMA binders (performance grade (PG) 76-22 from two different sources) and two WMA additives (i.e., Aspha-min® and Sasobit®) were blended to produce warm PMA binders. They were then artificially short-term and long-term aged through the rolling thin film oven and pressure aging vessel procedures. Second, long-term aged warm PMA binders were recycled using two virgin binders (PG 76-22 and PG 70-22), and the recycled binders were artificially aged again. Lastly, Superpave binder tests were performed through the rotational viscometer, the dynamic shear rheometer (DSR), and the bending beam rheometer (BBR). In general, the results of this study suggested that (1) the WMA additives and the aged PMA binders were found to have a significant influence on the performance properties of recycled binders (measured by the DSR and the BBR); (2) the use of PG 70-22 as a virgin binder was effective in offsetting the increase of binder stiffness due to the additives and the aged binders; and (3) the recycled warm PMA binders can result in satisfactory binder performance that meets current Superpave binder requirements.

Evaluation of High Temperature Rheological Characteristics of Asphalt Binder with Carbon Nano Particles

Abstract In recent years, nano technology, a relatively new field in science dealing with structures that are on the nano scale, have been used in numerous applications to improve properties of various materials. However, the use of this technology has not been explored in detail in the area of asphalt binder materials. The objective of this study was to investigate and evaluate the high temperature rheological properties of the binders containing various percentages of carbon nano particles. The experimental design for this study included the utilization of five binder sources, three binder grades (PG 64-22, PG 64-16, and PG 52-28), one type of nano particle, and four percentages of nano particles (0.0 %, 0.5 %, 1.0 %, and 1.5 % by weight of the virgin binder). Some of the rheological characteristics of these binders were obtained, including rotational viscometer (four testing temperatures of 120, 135, 150 , and 165°C) and dynamic shear rheometer. The results of the experiments indicated that the addition of nano particles was helpful in increasing the viscosity, failure temperature, phase angle, and viscous and elastic modulus values and in improving the rutting resistance of the binders. On the other hand, the binder sources and grades generally influenced their rheological properties as the nano particles were added to the asphalt binder.

Prediction of Absorbed, Inert, and Effective Bituminous Quantities in Reclaimed Asphalt Pavement

This paper presents methods to predict quantities of absorbed, inert, and effective bituminous material in reclaimed asphalt pavement (RAP) for particular sets of conditions; three RAP sources were investigated. The approach couples a data set of properties for 568 asphalt mix designs spanning five years of practice and testing of 100% RAP with added virgin binder; 394 compacted specimens and 68 loose specimens of 100% RAP were tested. A method to predict RAP absorbed asphalt was developed requiring two inputs: (1) total asphalt content; and (2) RAP effective specific gravity when coated with virgin binder. The method, was shown to yield more reasonable results than conventional methods, which were shown to very likely give incorrect absorbed asphalt estimates in some conditions. The relative effectiveness of RAP surface asphalt was evaluated, and estimates of inert and effective RAP asphalt were made for a variety of temperature, compactive effort, and warm mix additive conditions. Results showed differe...

Influence of Short-Term Aging on Rheological Characteristics of Non-Foaming WMA Binders

AbstractThe objective of this study was to conduct a laboratory investigation of rheological properties of non-foaming warm mix asphalt (WMA) binder after a short-term aging procedure. The conventional testing procedures such as viscosity, performance grade, creep and creep recovery, amplitude sweep, and frequency sweep were performed to determine the influences of non-foaming additives on asphalt binders. The experimental design included four binders and four non-foaming WMA additives. The test results indicated that, as expected, the non-foaming WMA additive can reduce the viscosity value of asphalt binder and thus decrease the mixing and compaction temperatures of the mixture. The failure temperatures of unaged and rolling thin film oven (RTFO) binders containing non-foam additives have a slight increase compared with the virgin binder, therefore improving the rut resistance of the mixtures. In addition, the creep recovery, amplitude, and frequency sweep tests show that the unaged and RTFO binders with...

Effects of Recycled Asphalt Pavement Amounts on Low-Temperature Cracking Performance of Asphalt Mixtures Using Acoustic Emissions

Significant increases in the cost of asphalt paving and increased awareness of the need for sustainable infrastructure in recent years have in turn increased the use of recycled asphalt pavement (RAP) in the manufacture of hot-mix asphalt (HMA). The use of RAP reduces the overall cost of HMA and provides significant environmental benefits. Experience has shown, however, that the addition of RAP to HMA can have a negative effect on the low-temperature fracture characteristics of the pavement. The purpose of this study was to determine the effects of RAP amounts on the low-temperature cracking performance of asphalt mixtures. Different percentages of RAP material, ranging from 0% to 50%, were studied. The embrittlement temperature of mixtures was determined with the use of an acoustic emissions technique. The disk-shaped compact tension [DC(T)] test was used to determine the fracture energy of asphalt mixtures. DC(T) fracture tests were conducted on two control mixtures with no RAP and mixtures that contained 10%, 20%, 30%, 40%, and 50% RAP. Both control and RAP mixtures were manufactured with PG 64-22 and PG 58-28 as the virgin binders, which brought the total number of mixtures tested to 12. In addition to DC(T) fracture testing, indirect tensile testing was conducted on HMA specimens that contained 20% and 40% RAP. Test results clearly indicated the effects of the presence of RAP materials on the low-temperature performance of mixtures. This study demonstrates the benefit of performing fracture tests before RAP is added to the asphalt mixture, and it demonstrates the use of an acoustic emissions-based testing procedure to screen mixtures susceptible to cracking at low temperatures.