Asphalt Binder Cracking Device Research Articles

Nano-Scale and Macro-Scale Characterizations of the Effects of Recycled Plastics on Asphalt Binder Properties

This paper summarizes the results of one of the first comprehensive laboratory studies that was conducted to evaluate the effects of adding different contents of recycled polyethylene terephthalate (rPETE) as a modifier to an asphalt binder on the rheological and mechanical properties of the modified binder as well as on the agglomeration behavior between the rPETE and asphalt binder at a multiscale level. The high-temperature and low-temperature performances of the modified binder were investigated at the macro-scale and compared with those of the unmodified binder using dynamic shear rheometer (DSR) and bending-beam rheometer (BBR) rheological tests, as well as asphalt binder cracking device (ABCD) testing. The nano-scale evaluation of the binder properties, including the surface roughness, bonding energy, and reduced modulus, was accomplished using atomic force microscopy (AFM). The results indicated that the addition of rPETE enhanced the high- and intermediate-temperature rheological properties of the modified PG 64-22 binder. The low-temperature rheological properties and resistance to cracking decreased slightly with increasing rPETE content in the asphalt binder. However, this reduction was not remarkable when adding 4%, 8%, and 10% rPETE contents. The asphalt binder modified with 4% rPETE had a low-temperature grade of −22, similar to that of the unmodified binder, indicating that 4% rPETE can be added to the binder to improve its high- and intermediate-temperature properties without reducing its resistance to low-temperature damage. The AFM tapping-mode results indicated that the inclusion of rPETE in the asphalt binder improved the stiffness properties of the modified binder as compared with those of the control asphalt binder. In addition, the rPETE-modified binders showed rougher surfaces than the control binder. The addition of rPETE to the binder increased the values of the reduced modulus and bonding energy compared with those of the control binder.

Enhancing aged SBS-modified bitumen performance with unaged bitumen additives

This study investigated the performance of SBS-modified bitumen (SBSMB) after aging and rejuvenation by utilizing macroscopic performance and microscopic characterization methodologies. The blending of aged SBS-modified bitumen (SBSPAV) with different proportions of SBSMB or 80–100 penetration grade base bitumen (90BB) was performed to produce SMB-rejuvenated bitumen (a blend of SBSMB and SBSPAV) and 90BB-rejuvenated bitumen (a blend of 90BB and SBSPAV). To evaluate high-temperature rutting behavior, multiple stress creep recovery (MSCR) tests were conducted on the binders, and the outcomes were analyzed using the Burgers model to elucidate their viscoelastic behaviors. Low-temperature performance was assessed using an asphalt binder cracking device (ABCD). Furthermore, the microscopic structure, roughness, and Young's modulus of the binders were investigated using an atomic force microscope (AFM). Thermal stability was assessed using a thermogravimetric analyzer (TGA). The findings indicated that SMB-rejuvenated bitumen exhibited favorable resistance to high temperatures and the ability to withstand heavy traffic loads. The stress sensitivity of 90BB-rejuvenated bitumen surpassed that of SMB-rejuvenated bitumen. The high-temperature performance rating of 90BB-rejuvenated bitumen displayed a continuous decline, indicating poor load-bearing capacity. Regardless of the unaged bitumen type, higher doses of unaged bitumen led to a gradual decrease in the rejuvenated bitumen's cracking temperature, indicating the enhancement of low-temperature performance of SBSPAV. However, both SMB-rejuvenated bitumen and 90BB-rejuvenated bitumen fell short of matching the performance level of pure SBSMB. AFM outcomes demonstrated that with increasing SMB dosage, the number of bee-like structures initially decreased before rising again, coupled with an increase in their volume. Conversely, an increase in 90BB dosage led to a gradual reduction in bee-like structures, accompanied by increased volume. The roughness of both SMB-rejuvenated bitumen and 90BB-rejuvenated bitumen exhibited improvements compared to SBSPAV, suggesting enhanced adhesion performance of the rejuvenated bitumen. TGA results unveiled lower thermal stability in 90BB-rejuvenated bitumen in comparison to SMB-rejuvenated bitumen. This study introduces a novel perspective on the design of SBS-rejuvenated bitumen.

Characterization of styrene-butadiene-styrene (SBS)-modified asphalt binders using the bending beam rheometer and the asphalt binder cracking device

The addition of styrene butadiene styrene (SBS) to asphalt binders has led to enhanced performance in pavements across the entire range of working temperatures. SBS-modified binders have also proven to be more difficult to characterize in terms of their rheological properties. Low-temperature properties of asphalt binders are typically evaluated using the bending beam rheometer (BBR), which was developed to measure creep stiffness. Recent refinements to the BBR analysis have led to the development of Δ Tc which is meant to provide more insight into the relaxation properties of the binder. The Asphalt Binder Cracking Device (ABCD) was developed to improve on this characterization by also taking into consideration the failure strength and coefficient of thermal contraction. Previous research has shown that the ABCD provides more valuable insight into the effect of SBS on the low-temperature properties of asphalt binders. This paper will evaluate the ability of these two low-temperature tests to characterize the performance of five different asphalt binders with increasing concentrations of SBS. It was found that the evaluation of the materials using Δ Tc was inconsistent with binder type and generally indicated that SBS reduced cracking resistance, while the ABCD critical temperature and the proposed Δ Tf parameter generally showed an improved correlation with SBS concentration.

A case study of the comparison between rubberized and polymer modified asphalt on heavy traffic pavement in wet and freeze environment

Ground tire rubber (GTR) usage in asphalt pavement with the dry process has gained more prominence in recent times. The objective of this work is to investigate the pavement performance of GTR-modified asphalt pavement and polymer-modified asphalt pavement on heavy volume of traffic conditions in Michigan's wet and freeze environment. A suite of laboratory tests was done to evaluate the pavement performance of GTR-modified and polymer-modified asphalt mixtures. To reveal the strain and stress relationship under different frequencies and temperatures, the dynamic modulus test was applied. The Hamburg wheel tracking device (HWTD) was used to assess the high-temperature deformation resistance. The disc-shaped compact tension (DCT) test was used to evaluate the low-temperature cracking characteristics. The characteristics of the asphalt binder were assessed by the dynamic shear rheometer (DSR) for high-temperature properties and the asphalt binder cracking device (ABCD) for low-temperature properties. After the construction, a field noise test was conducted. The experimental results stated that the polymer-modified asphalt mixture and GTR-modified asphalt mixture showed higher dynamic modulus and better ability to prevent cracking than the conventional asphalt mixture at low temperatures, as well as better permanent deformation and stripping resistance than the conventional asphalt mixture. The fracture energy of the GTR-modified hot mix asphalt (HMA) is 13–16 % larger than the polymer-modified HMA. The number of passes to the stripping point of GTR-modified was 510–518 % higher than the conventional HMA. When compared to the field core, the lab-compacted HMA offers superior pavement performance. The extracted asphalt binder test results show the GTR-modified asphalt has better rutting resistance and cracking resistance than polymer-modified asphalt, and the results in the noise test demonstrated that the rubber-modified asphalt pavement mitigated the noise level by 2–3 dB on the road at different vehicle speeds. Moreover, the pavement condition was noticeably enhanced after the reconstruction of the surface course. The total number of passenger tires to be used in this project is about 2270. To summarize, better rutting and cracking properties in asphalt pavement are shown by the project's utilization of rubber technology. And the GTR-modified HMA is comparable to polymer-modified HMA. Therefore, it may be appropriate to utilize rubber technology on high-traffic volume asphalt pavement in Michigan's wet and freeze climate.

Procena niskotemperaturnih svojstava smeše bitumena i SBS polimera različitih topologija metodom ABCD

Introduction: Due to climate change, scientists around the world, including specialists in the road construction industry, are forced to take into account the need for regular monitoring of the low-temperature properties of both individual building materials and the properties of multicomponent road composites based on them. Therefore, the possibility of developing new approaches and methods for evaluating these properties is being studied. Methods: For these purposes, Dr. Kim Sang-Soo proposed a new method for evaluating the low-temperature properties of road binders, which was called the ABCD (Asphalt Binder Cracking Device) method. The use of the device does not require special skills and knowledge and auxiliary equipment is widely available in laboratories of road construction organizations. The duration of the test does not exceed 4-5 hours. Results: The possibility and effectiveness of regulating the cracking temperature of bitumen-containing binders by introducing styrene-butadiene thermoplastics of various topologies into the composition is shown using the example of industrially produced batches of petroleum road viscous oxidized bitumen and applying the ABCD methodology. Conclusions: In Russia, where winter temperatures in the vast majority of the country fall below minus 30 degrees Celsius, it is extremely important to control the behavior of bitumen binders and multicomponent mixtures of different compositions (asphalt concrete mixtures). The national standard GOST R 58400.11-2019 has been put into effect and the production of appropriate measuring equipment has been established. At the same time, the ABCD method can be used both to study the properties of mixtures of binders with polymers of various topologies and to select a commercial binder that meets the requirements of a specific region of highway operation.

Comprehensive performance evaluation of high polymer-modified asphalt binders beyond linear viscoelastic rheological surrogates

• High polymer-modified (HP) binders exhibit superior performance compared to PMA. • LVE surrogates fail to predict failure properties of complex and modified binders. • HP binders displayed higher strain tolerance in DENT compared to conventional PMA. • HP binders tend to have lower cracking temperature in ABCD compared to typical PMA. • FTIR I PTDB and I PVDB indices can be used to detect potential polymer degradation. Polymer modification of asphalt binders has progressively become more common over recent decades. Styrene-Butadiene-Styrene (SBS) is a well-recognized elastomer that has been commonly used in asphalt pavements. SBS polymer specifically exhibits a chemical morphology of hard polystyrene segment tethered by soft polybutadiene segment. Concerns related to binder pump clogging and reduced mixture workability have limited the SBS copolymer content in polymer-modified asphalt (PMA) to around 3 %. This motivated researchers to develop a new SBS polymer structure by modifying the midblock structure to have much higher vinyl content. High polymer-modified (HP) binder technology allowed the use of SBS at higher levels of 7–8 %. Although several studies have highlighted the positive impacts of HP on asphalt binders, they were mostly limited to the linear viscoelastic (LVE) domain. Therefore, there is still a need for a comprehensive evaluation of HP binders that considers failure properties, which constituted the main motivation of this research. In this study, Multiple Stress Creep Recovery (MSCR), Double Edge Notched Tension (DENT) and Asphalt Binder Cracking Device (ABCD) test results showed that HP binders exhibited superior performance compared to PMA in terms of higher strain recovery and lower non-recoverable creep compliance at high temperatures (52–70 °C), higher strain tolerance at intermediate temperature (25 °C), and lower (colder) cracking temperatures at sub-zero temperatures. Additionally, chemical analysis showed minimal HP degradation potential compared to PMA.

Proposed Changes to Asphalt Binder Specifications to Address Binder Quality-Related Thermally Induced Surface Damage

Superpave specifications address binder properties that may lead to rutting, transverse cracking, and fatigue damage with varying degrees of success. However, asphalt binder production and formulation has significantly changed and introduced much more variability in relation to quality since the development of the Superpave Performance-Grade system because of economic, technical, and environmental reasons. Consequently, aged-induced surface distresses under combined thermal and traffic loading have become the main challenge for highway agencies. Thermally induced surface deterioration appears in the form of traditional transverse cracking, block cracking, and raveling, or accelerating damage at construction joints. This study evaluated the limitations of the proposed linear viscoelastic (LVE) rheological cracking surrogates, such as ΔTc, R-value, and G-R parameters, and the ability of the Asphalt Binder Cracking Device (ABCD) failure test to overcome these limitations. ABCD is particularly appropriate to rank binder performance because the measured cracking temperature (Tcr) encompasses binder LVE properties, failure strength, coefficient of thermal contraction, and cooling rate. The proposed parameter (ΔTf = Tc(S = 300 MPa) from BBR—Tcr from ABCD) relates the failure temperature to the equi-stiffness temperature and gives credit to well-formulated and compatible polymer-modified binders expected to increase binder strength and strain tolerance. This paper proposes a specification framework based on both ΔTc and ΔTf, universally applicable, regardless of binder composition. Additionally, preliminary purchase specification limits for binders used in surface layers are proposed based on the analysis of 44 binders, 15 with corresponding field performance data. Obviously, as confirmed by a recent stakeholder workshop and industry feedback, these preliminary specification limits need further validation and possible adjustments to account for regional experience and local challenges.

Characterization of Highly Polymerized Alaskan Asphalt Binders and Mixtures

Highly polymerized asphalt binders (HPABs) and mixtures have been used in recent years to address the cracking and rutting concerns due to varying climates and seasonal extreme conditions in Alaska. However, there has not been systematic characterization and performance data development for these materials. Hence, as presented in this paper, this study intends to systematically characterize the HPABs and mixtures and identify the performance benefits of these materials through laboratory tests and monitoring of field sections. Three HPABs (PG 52-40, PG 64-40, and PG 52-46) along with one unmodified asphalt binder (UAB) (PG 52-28) used in Alaska were used, and their morphologies and chemical and rheological properties were evaluated. The Fourier-transform infrared spectroscopy (FTIR) spectra and fluorescence microscopy (FM) morphology results presented the unique chemical functional groups of HPABs and the biphasic structure found with polymers distributed in the HPABs, respectively. The bending bean rheometer (BBR) and asphalt binder cracking device (ABCD) test results indicated that the HPABs apparently had lower (colder) cracking temperatures (i.e., better low-temperature cracking resistance) than the UAB. The multiple stress creep recovery (MSCR) test results showed that the HPABs had better rutting resistance than the UAB, as predicted by lower Jnr but higher %R values. The G* master curves illustrated that the HPABs were softer and less temperature susceptible than the UAB at intermediate temperatures, which implied better fatigue cracking resistance. The laboratory evaluation of performance of asphalt mixtures also confirmed that the asphalt mixtures with PG 52-40 and PG 64-40 had better resistance to rutting and low-temperature cracking than the mixture with PG 52-28. These results were further confirmed through field surveys of recent paving projects constructed in Alaska and data from pavement sections in the Long-Term Pavement Performance program database.

Study of the Influence of SBS and APDDR on the Low-Temperature Properties of Road Bitumen

A comparative assessment of the effect of two modifiers on the low-temperature properties of BND 90/130 bitumen was investigated using Asphalt Binder Cracking Device (ABCD test) and Dynamic Shear Rheometer (DSR 4-mm test). These modifiers are styrene-butadiene-styrene block copolymer (SBS) and active powder of discretely devulcanized rubber (APDDR) - powder elastomeric modifier obtained by high-temperature shear grinding of waste tire crumb rubber. ABCD results of RTFO-aged samples showed clear and gradual decrease of the ABCD cracking temperature (improvement) for all BC as the modifier concentration increases. It is noteworthy that the Bitumen Composites (modified bitumens) were cracking at higher strain and fracture stress values compared to neat bitumen. Results of DSR-4 mm test showed a decrease in the complex shear modulus (G*), storage modulus (G¢) and loss modulus (G²) BC compared to the neat bitumen. It is shown that bituminous composites have no maximum on the Cole-Cole diagram (dynamic vitrification) at T = -28°C which is observed in the neat bitumen.

Waste cathode-ray-tube glass powder modified asphalt materials: Preparation and characterization

Cathode-ray-tube (CRT) is the ingredient of glass used in obsolescent televisions or computer monitors. CRT glass contains a considerable amount of heavy metals, and the landfilling of CRT glass is significantly harmful to the environment. In an effort to recycle waste CRT glass instead of landfilling it, recycled CRT glass powders were introduced to asphalt binders as a modifier in this preliminary investigation. The recycled CRT glass was processed to a particle size smaller than 0.075 mm and mixed with asphalt binder (PG 58–28) to produce asphalt mastics with four different concentrations (0, 5, 10, and 15 wt%). The rheological performance was characterized with the rotational viscosity (RV), dynamic shear rheometer (DSR), and multiple stress creep recovery (MSCR) tests. The fatigue performance was evaluated by linear amplitude sweep (LAS) test. Meanwhile, the low-temperature properties were measured by the asphalt binder cracking device (ABCD). The hazard materials leaching test was applied to evaluate the leaching potential of lead content into the external environment due to the high lead content in the modified asphalt. The test results revealed that the increase of CRT glass powder content improved the energy of activation compared with that of virgin binder, as well as the resistance of permanent deformation. Furthermore, the incorporation of CRT glass powder may slightly increase the fatigue life of asphalt because of the improved physicochemical interaction between glass and bitumen. The low-temperature cracking temperature first decreased with the increase of CRT glass powder content and then increased as the CRT content increased further. The leaching test demonstrated that the CRT glass powders incorporated into asphalt binders represented a lower lead leaching content than that of the original CRT glass powder, where the lead leaching amount of CRT glass modified asphalt binder is obviously lower than the specified level of 5 mg/L. Therefore, it is possibly acceptable to recycle CRT glass powders in asphalt binders as an additive as an environmental-friendly recycling method, in which the optimal addition content of CRT glass powders could be up to 10% (wt.).

Cold In-Place Recycling Asphalt Mixtures: Laboratory Performance and Preliminary M-E Design Analysis.

Cold in-place recycling (CIR) asphalt mixtures are an attractive eco-friendly method for rehabilitating asphalt pavement. However, the on-site CIR asphalt mixture generally has a high air void because of the moisture content during construction, and the moisture susceptibility is vital for estimating the road service life. Therefore, the main purpose of this research is to characterize the effect of moisture on the high-temperature and low-temperature performance of a CIR asphalt mixture to predict CIR pavement distress based on a mechanistic–empirical (M-E) pavement design. Moisture conditioning was simulated by the moisture-induced stress tester (MIST). The moisture susceptibility performance of the CIR asphalt mixture (pre-mist and post-mist) was estimated by a dynamic modulus test and a disk-shaped compact tension (DCT) test. In addition, the standard solvent extraction test was used to obtain the reclaimed asphalt pavement (RAP) and CIR asphalt. Asphalt binder performance, including higher temperature and medium temperature performance, was evaluated by dynamic shear rheometer (DSR) equipment and low-temperature properties were estimated by the asphalt binder cracking device (ABCD). Then the predicted pavement distresses were estimated based on the pavement M-E design method. The experimental results revealed that (1) DCT and dynamic modulus tests are sensitive to moisture conditioning. The dynamic modulus decreased by 13% to 43% at various temperatures and frequencies, and the low-temperature cracking energy decreased by 20%. (2) RAP asphalt incorporated with asphalt emulsion decreased the high-temperature rutting resistance but improved the low-temperature anti-cracking and the fatigue life. The M-E design results showed that the RAP incorporated with asphalt emulsion reduced the international roughness index (IRI) and AC bottom-up fatigue predictions, while increasing the total rutting and AC rutting predictions. The moisture damage in the CIR pavement layer also did not significantly affect the predicted distress with low traffic volume. In summary, the implementation of CIR technology in the project improved low-temperature cracking and fatigue performance in the asphalt pavement. Meanwhile, the moisture damage of the CIR asphalt mixture accelerated high-temperature rutting and low-temperature cracking, but it may be acceptable when used for low-volume roads.

Universal and practical approach to evaluate asphalt binder resistance to thermally-induced surface damage

Economic drivers, changing material streams, environmental regulations, and formulation changes driven by the climate-based PG grading system itself have led to substantial changes in the production and modification of paving grade asphalt since the development of Superpave Performance-Graded (PG) binder specifications during the 1990s. Superpave specifications and mechanistic-empirical pavement design criteria attempt to address pavement distresses such as rutting, transverse cracking, and fatigue damage with varying degrees of success. Unexpectedly though, aged-induced surface distresses have worsened to become the primary cause of pavement damage for many highway agencies. Thermally-induced surface deterioration, which may not be directly linked to traffic loading, appears in the form of traditional evenly spaced transverse thermal cracking, block cracking, raveling, or accelerating damage at joints or other areas where density is insufficient to prevent moisture and oxygen from permeating into the asphalt surface layer. The source of damaging stresses leading to such failures are not well-understood, nor have binder properties contributing to early pavement surface damage been completely and effectively controlled by PG specifications.Transverse cracking damage is known to require external restraint in one-dimension to impose tensile stresses on the asphalt concrete mixture as it cools and contracts. Recent experimental results from mixture bending beam testing (BBR Sliver), acoustic emissions, and finite element analysis (FEA) provide evidence that asphalt concrete can be damaged on cooling even when no external restraint is imposed. A second “Internal Restraint” damage mechanism has been theorized to create localized tensile stresses due to differential contraction between mastics and the surrounding aggregate skeleton as a pavement surface cools. This recently proposed concept is now thought to be one of the primary causes for surface block cracking and raveling. Moreover, damage accumulating via the internal restraint mechanism acts cumulatively with other sources of stress on the mixture, such as the top-down fatigue cracking that initiates near the tires edge, transverse cracking due to externally restrained cooling, thermal fatigue cycling without sufficient healing, longitudinal cracking at the construction joints or reflective cracking from cracks in the underlying layer that propagate through the overlays at the surface.Other researchers have proposed various rheological parameters measured in the linear-viscoelastic region (LVE) to be indicators of problematic binders that are prone to age-induced surface damage. Most of these parameters can be fundamentally or empirically related to binder stress relaxation properties at low temperatures. Although these LVE rheological surrogates can be used to rank binder performance for straight-run asphalts produced by conventional vacuum distillation, these materials typically have a narrow strain tolerance and strength range. Limitations of LVE parameters, such as ΔTc, R-value, or G-R parameter, are more noticeable when used to characterize the performance of complex binders. This study indicates that rheological surrogates in the LVE region are not a direct measure of binder failure properties such as strength, ductility, strain tolerance, fracture toughness, or fatigue resistance, particular after a bitumen has been modified with polymers (PMA). Hence, rheological surrogates within the LVE domain are important, but not sufficient for a universal and blind approach to evaluate binders without knowing their composition or production process. LVE surrogates alone cannot rank performance for a wide range of complex systems such as incompatible blends, recycled materials (crumb rubber, shingles, plastics, biomaterials) or PMA’s using the same thresholds for pass/fail specifications. This paper proposes a practical approach to rank a binder’s resistance to low-temperature age-induced surface damage by combining LVE rheological measurements with failure parameters using the Asphalt Binder Cracking Device. ABCD is particularly appropriate to ranking surface damage via the internal restraint cooling model because the binder cracking temperature measured in this test depends upon both failure strength, cooling rate, and the binder’s coefficient of thermal contraction (CTC).

The impact of bio-oil as rejuvenator for aged asphalt binder

Recycling technology has been widely applied on road pavement due to the aging problem of asphalt binder and the extensive requirement for maintenance. The aim of this research is to use bio-oil generated from sawdust as a rejuvenator to recycle aged asphalt. In this research, the performance graded asphalts PG 58-28 and PG 64-22 were selected as the base binders. The bio-oil contents were 10%, 15% and 20% of the total binder by weight. The Rotational Viscometer (RV) test, Dynamic Shear Rheometer (DSR) test, and Asphalt Binder Cracking Device (ABCD) test were applied to characterize the properties of bio-rejuvenated asphalts and virgin control asphalts. Additionally, the Fourier Transform Infrared Spectroscopy (FTIR) test was conducted to characterize the degree of restoration of aged asphalt binders from the aspect of functional groups. It was found that the bio-rejuvenator decreases the viscosity and activation energy, while increasing the temperature susceptibility and the content of viscous components of the aged asphalts. The aged asphalt can be softened by the bio-rejuvenator significantly; with the use of bio-rejuvenator, the rutting index of aged asphalts PAV PG 58-28 and PAV PG 64-22 at high temperatures from 52 °C to 76 °C was decreased by 75.5% and 77.2% in average, respectively. The bio-oil can restore the low temperature crack resistance of aged asphalts PAV PG 58-28 and PAV PG 64-22 to, or even better than, the level of virgin asphalts. The sulfoxide (SO) index and aromatic (CC) index can be used to evaluate the degree of restoration using bio-rejuvenator to recycle aged asphalt, but carbonyl (CO) is not applicable. Therefore, the bio-oil generated from sawdust can be used as a rejuvenator to recycle the aged asphalts PAV PG 58-28 and PAV PG 64-22. Moreover, the bio-rejuvenator contents of 15% and 20% are recommended to recycle the aged asphalt PAV PG 58-28 and aged asphalt PAV PG 64-22, respectively.

Impacts of WMA Additives on Viscosity and Cracking of Asphalt Binder

Abstract The basic concept of warm mix asphalt (WMA) technologies is to reduce the asphalt binder viscosity, which allows the asphalt to attain a suitable viscosity to coat the aggregates and thus to compact asphalt mixtures at lower temperatures. A main concern for adding WMA additives to asphalt is that it might reduce the rutting resistance at high temperatures and the cracking resistance at low temperatures. To address these concerns, this article presents the impacts of various amounts of WMA additives on the viscosity and low-temperature cracking of asphalt binder. The test results at 135°C show that the viscosity of asphalt reduced significantly when 0.5 % of Additive B was added; the viscosity did not decrease when up to 1.0 % of Additive A was added. When the temperature was lowered to 120°C, however, a more drastic reduction in viscosity was observed when just 0.5 % of additives were added, and the viscosity remained relatively steady as the dosage was increased up to 3.0 %. These viscosity test results confirm that the higher amounts of WMA additives do not necessarily reduce the viscosity of asphalt binder. To characterize the low temperature property of the asphalt binder, the asphalt binder with WMA additives were tested using the asphalt binder cracking device (ABCD). As the WMA additives were increased from 0.5 % to 3.0 %, the cracking temperature increased slightly but remained steady near the cracking temperature of the virgin asphalt binder. The ABCD test results confirm that the cracking temperature of asphalt binder is not significantly affected by WMA additives.

Assessment of nanoparticles dispersion in asphalt during bubble escaping and bursting: Nano hydrated lime modified foamed asphalt

Saving mixing energy by using escaping and bursting bubbles during the production process of nanomaterial-modified water-foamed asphalt is a novel preparation idea, which can be taken as one type of cleaner physical warm-mix asphalt technology. The objective of this study is to assess the dispersal of nano hydrated lime (NHL) particles in the asphalt using a scanning electron microscopy (SEM) test, and to evaluate the physical properties of NHL modified water-foamed asphalt (NMFA). In this study, the NHL and sodium dodecylbenzene sulfonate (C12H25C6H4SO3Na) were added to the water to form suspensions, and the suspensions were mixed with asphalt to form NMFA. The X-ray diffraction (XRD) test was used in order to understand the NMFA’s microstructure and dispersal of NHL in water-foamed asphalt. The dynamic shear rheometer (DSR) and the asphalt binder cracking device (ABCD) were also used to evaluate the high temperature and low temperature performance of NMFAs, respectively. The SEM images show that the NHL particles were well dispersed in the water-foamed asphalt while the XRD test results confirmed it and demonstrated that the NMFAs may form an intercalated microstructure. In addition, the presence of NHL reinforcement in the water-foamed asphalt stiffens the asphalt, consequently decreasing the rutting potential. The addition of NHL also increased the low temperature cracking resistance of NMFAs, i.e. decreased the cracking temperature and increased the fracture stress.

Quantification of physicochemical properties, activation energy, and temperature susceptibility of foamed asphalt binders

Applications of foamed binder have been spurred by the increased focus on sustainable construction approach and stringent environmental laws. This study was initiated to evaluate the performance of foamed asphalt binder produced using a combination of physical and chemical foaming agents, known as ethanol and sodium bicarbonate (NaHCO3), respectively. This paper presents the properties of foamed asphalt binder assessed using Fourier transform infra-red (FTIR) spectroscopy, asphalt binder cracking device (ABCD), and activation energy analysis. The FTIR test was conducted to evaluate the possibility of any chemical reaction taken place, as well as to characterize the effects of oxidation on the chemical functional groups present in foamed asphalt binders. The ABCD test was carried out to evaluate the thermal cracking temperatures of prepared binders. The activation energy of each binder type was analyzed based on the viscosity test results and Arrhenius equation to estimate the energy required to overcome the intermolecular forces between the molecules in the asphalt binder to initiate flow. The FTIR results reveal that ethanol alone is unreactive with the binder, where most of the functional groups have shown comparable change ratios. This indicates that there are no chemical reactions that occurred in the foamed asphalt binders, either with the addition of ethanol or various combinations of ethanol and NaHCO3. The application of foaming agents definitely lowers the activation energy to overcome the intermolecular forces between the molecules in the asphalt binder to allow flow to occur. The foamed binders were found to have a comparable or better low temperature characteristic as compared to the control binder. A higher dosage of foaming agents proportionally increased the resistance to thermal cracking of asphalt binders. Overall, the use of foaming technique and newly proposed foaming agents has shown great potential to produce eco-friendly pavement material.

Effect of Binder Type, Mastic, and Aggregate Type on the Low-Temperature Characteristics of Modified Hot Mix Asphalt

Abstract The purpose of this study was to evaluate the effect of binder type, mastic, and aggregate type on the low-temperature cracking characteristics of asphalt mixtures. Six different performance grade (PG) binders were utilized for this study: PG64-28, PG64-28 with poly phosphoric acid, PG64-34 SBS, PG76-22 SBS, a terminal blend asphalt rubber, and PG64-28 with 2 % latex. Each binder was tested to determine its low-temperature cracking resistance using the asphalt binder cracking device (ABCD) and the Superpave tests. A Superpave 9.5 mm mixture was designed using each of the six binders for this study and two sources of aggregates (crushed stone and gravel). Each mixture was then tested for low-temperature cracking resistance using the asphalt concrete cracking device (ACCD). Mastics corresponding to each mixture were tested for low-temperature cracking resistance using the ABCD. Analysis of the results showed that the AASHTO critical cracking temperature had a strong correlation with the ABCD binder and mastics results, but did not correlate well with the mixture tests. Mastic testing generally did not correlate well with the mixture test results. ABCD and ACCD tests results indicated that they were sensitive to binder type, aging time, and aggregate types.

Laboratory Evaluation and Field Implementation of Polyethylene Wax-Based Warm Mix Asphalt Additive in USA

The use of Warm Mix Asphalt (WMA) for the construction of roads around the world is growing rapidly. This paper presents a new organic WMA product that has been recently introduced to the US market, which is Polyethylene (PE) Wax-based WMA additive with crystal controller to increase the low temperature cracking resistance and anti-stripping agent to enhance moisture susceptibility. To determine the optimum dosage rate, the viscosities of the binder with varying amounts of additive were measured. Based on the Asphalt Binder Cracking Device (ABCD) test, it was found that the low-temperature cracking temperature of asphalt binder would not be affected by the amounts of the additive up to 3.0%. The new Polyethylene (PE) Wax-based WMA mixtures with Reclaimed Asphalt Pavement (RAP) materials were also tested using the Hamburg wheel tracking device and the wheel passes were significantly higher with WMA mixtures PG 64-28 binder, Minnesota aggregates and 25% RAP than the ones with 64-22 binder, Iowa aggregates and 10% RAP. The Hamburg test results seemed to be influenced by more on the characteristics of aggregates and RAP materials than the WMA additive. Two in-service roads in Iowa and Minnesota were successfully rehabilitated using the PE Wax-based WMA mixtures. The average void of 3.8-cm (1.5-inch) WMA overlay (9.0%) was higher than that of HMA overlay (7.0%) placed on an urban street in Iowa City. It was partly due to asphalt temperature that was lowered to match the lower aggregate temperature. However, it is interesting to note that the average air void of the cores obtained from the rehabilitation section of the same street using the same WMA was significantly lower (6.0%). In Minnesota's state highway, the average air voids of four WMA and HMA cores for quality control were 5.85% and 5.29%, respectively and those of four other WMA and HMA cores for quality assurance were 6.05% and 6.01%, respectively. The WMA pavements were easier to reach 94% density with fewer passes of a compactor than the HMA.

Low Temperature Performance of Sasobit-Modified Warm-Mix Asphalt

In the summer of 2008, a field trial project using Sasobit-modified warm-mix asphalt (WMA) was established in Alaska, which was Alaska’s first experience with a WMA technology. Previous studies conducted by writers identified a number of engineering benefits of Sasobit-modified WMAs over conventional hot-mix asphalt (HMA). This paper presents a further assessment focusing on low temperature performance of both Sasobit-modified WMA binders and mixes. A series of binder tests including bending beam rheometer (BBR), direct tension test (DTT), and asphalt binder cracking device (ABCD) tests were conducted. Indirect tension tests (IDT) of mixtures along with a thermal cracking analysis were performed to obtain a more definitive answer regarding the WMA application for cold-weather conditions. Results showed a decrease of tensile strength for both WMA binders and mixtures at low temperatures, and the cracking temperatures of both WMA binders and mixtures increased with the increase of Sasobit content. However, the increase in cracking temperature was very slight, which indicated that Sasobit addition had an insignificant effect on resistance to low temperature cracking. Therefore, Sasobit-modified WMA should be suitable for the Northern Region of the Alaska Department of Transportation and Public Facilities (AKDOT&PF) without compromising the resistance to low temperature cracking.

Evaluation of Low-Temperature Binder Properties of Warm-Mix Asphalt, Extracted and Recovered RAP and RAS, and Bioasphalt

This research project evaluates the low-temperature performance of energy-efficient and environmentally friendly hot-mix asphalt (HMA) paving materials. Innovative materials gaining interest in the asphalt pavement industry includes warm mix asphalt (WMA), recycled asphalt shingle (RAS), reclaimed asphalt pavement (RAP), and bioasphalt. The materials are used as modifiers in typical HMA to enhance low-temperature field performances. Sasobit compounds at 0.5, 1.0, and 1.5%, by weight of performance grade (PG) 52-34 asphalt binder, are used to design the WMA. Five and 10% of RAS were also added to a PG 52-34 asphalt binder. 50% of RAP combined with 50% of the base PG 58-28 binder, and 100% RAP extracted from the PG 58-28 HMA, were prepared and tested. Bioasphalt was produced from swine waste and used to modify PG 64-22 asphalt binder. By using the Superpave bending beam rheometer (BBR) and the new asphalt binder cracking device (ABCD) method, the thermal cracking performance of the samples were tested. The results showed that (1) the ABCD method can be used alongside or as a confirmation test for the BBR in evaluating the low-temperature cracking resistance behavior of asphalt binders; (2) adding WMA beyond a certain percentage could potentially reduce the low-temperature cracking performance of asphalt binders; and (3) swine waste bioasphalt can enhance low-temperature asphalt binder performance.