Viscometer Tests Research Articles

The role of nanomaterials in enhancing adhesion properties between bitumen and aggregate particles

During production and construction stages of asphalt mixtures, rheology of bitumen must be set at certain level. In addition, the adhesion strength between bitumen and the aggregate particles should be high enough so that during the service life of the pavement, asphalt mixture can resist various distresses. There are different methods of controlling rheological properties of bitumen binders and increasing adhesion properties of asphalt mixtures. One of the most effective methods of modifying bitumen binders of asphalt mixtures is using nanomaterials. In this research, two bitumen types of 60/70 and 85/100 penetration grades, three aggregate types (limestone, siliceous, and granite) and four nanomaterials; namely, nanohydrated lime (NHL), nanosilica (NSiO2), nanolime (NCaCO3) and, nanoclay bentonite (NClay) were used at 2, 4, and 6 % of the weight of bitumen. X-ray diffraction and X-ray fluorescence tests were performed and, microscopic images of thin-sections of aggregates and asphalt mixtures were taken with the aim of evaluating petrographic properties of aggregates and bonding characteristics of the bitumen binders with aggregate particles. Physical and rheological properties of the nano-modified bitumen binders were evaluated, performing dynamic shear rheometer and rotational viscometer tests. Boiling water and pull-off tests were also carried out in order to investigate the coating ability and the adhesion strength that is performed at the aggregate surface in the interface with the bitumen binders. Digital images were analyzed using Digimizer Software. The results indicated that the addition of nanomaterials at certain optimal percentage, affected viscosity and improved rheological behavior of bitumen binders at different temperatures; and, increase adhesion properties of the bitumen coating the aggregate particles. Comparing the effects of different aggregates, it resulted that the binder coating limestone aggregates performed better than the siliceous and the granite aggregates. Adhesion and rheological properties of the 60/70 pen bitumen that was modified with nanomaterials were better than those of the pure 85/100 pen bitumen. Nano-modified binders at 4 % NHL, or 2 % NSiO2, or 4 % NCaCO3, or 4 % NClay exhibited the best behavior. Among these, nano-modified binders containing 4 % NHL resulted in better performance. Finally, correlation between adhesion and rheological behavior of mixes were adequate for nano-modified binders in order to improve charcteristics of asphalt mixes at mixing operation and construction stages.

Effect of nano-TiO2 on physical and rheological properties of asphalt cement

Abstract In recent years, nano-modified asphalt has gained significant attraction from researchers in the design of asphalt pavement fields. The recently discovered Titanium dioxide nanoparticles (TiO2) are among the most exciting and promising nanomaterials. This study examines the effect of 1, 3, 5, and 7% of nano-TiO2 by weight of asphalt on some of its rheological and hardened properties. The experimental study included physical and rheological properties. The asphalt penetration, softening point, ductility, and rotational viscometer tests indicate that 5% nano-TiO2 is the ideal amount to be added to bitumen as a modifier. The study of the rotating viscosity test showed that the addition of nano-TiO2 helped to increase viscosity and lessen bituminous sensitivity. Rutting factor in terms of G*/sin δ indicated the addition of 3 to 7% of nano-TiO2 increased the rutting resistance of asphalt against higher temperatures and promoted performance grade by about one grade at 3% and two grades at a range of 5–7% this suggests that nano-TiO2 increased the stiffness of the asphalt and leading to enhance the rutting performance of asphalt. While fatigue parameter, G*.sin δ shows that as nanocontent increases, higher stiffness at 5 and 7% of TiO2 content leads to an increase in complex modulus and a decrease in fatigue parameter. Higher creep stiffness and higher m-values were noted at low temperatures as nano increases in asphalt binder, increasing stiffness and decreasing the m-value at −6 and 12°C. As a result, using 5% nano-TiO2 will improve asphalt’s physical properties and enhance asphalt anit-rutting and fatigue resistance.

Biomass waste to produce bio oil as rejuvenator for asphalt based on pyrolysis technology

ABSTRACT The objective of the current study is to research the suitability of using two bio-oils produced from corncob and birch bark as two bio-rejuvenators to regenerate aged asphalt binders. To this end, the pyrolysis characteristics of corncob and birch bark were analysed using a thermogravimetric analyzer. The chemical characteristics of the bio-rejuvenators were then evaluated via an elemental analyzer and the Gas Chromatograph Mass Spectrometer (GC-MS) test. The results revealed the presence of a great quantity of lightly weighted compounds in bio-oils. Pen70 asphalt was used as control asphalt binders. The Rotational Viscometer (RV) test result showed that bio-rejuvenators could help reduce the viscosity of aged asphalt binders. In addition, the Dynamic Shear Rheometer (DSR) experiments revealed that bio-rejuvenators could reduce the complex shear modulus, decrease percent strain recovery, increase non-recoverable creep compliance and restore the fatigue performance of the aged asphalt. The Bending Beam Rheometer (BBR) tests indicated that the cracking performance of the bio-rejuvenated asphalt was also improved compared with the aged asphalt. The Fourier transform infrared spectra demonstrated that the bio-rejuvenators helped reduce the aged asphalt's carbonyl and sulfoxide indexes. In addition, the Gel Permeation Chromatography (GPC) test indicated that bio-rejuvenators reduced the polydispersity and molecular weight of the aged asphalt.

Investigation into Rheological Behavior of Warm-Mix Recycled Asphalt Binders with High Percentages of RAP Binder

The rheological properties of warm-mix recycled asphalt binders are critical to enhancing design quality and interpreting the performance mechanisms of the corresponding mixtures. This study investigated the rheological behavior of warm-mix recycled asphalt binders with high percentages of RAP binder. The effects of two warm-mix additives [wax-based Sasobit (S) and surfactant-based Evotherm-M1 (E)], a rejuvenating aging [ZGSB (Z)], four RAP binder contents (0%, 30%, 50% and 70%), and three aging states (unaged, short-term aged and long-term aged) were evaluated in detail using the dynamic shear rheometer (DSR), bending beam rheometer (BBR) and Brookfield rotational viscometer tests as well as conventional performance tests over the whole range of temperatures. The results showed that the rejuvenating agent Z effectively alleviated the aging effect of the RAP binder; however, it could hardly eliminate entirely this negative impact, especially at higher RAP binder contents. The addition of S remarkably lowered the apparent viscosity of the warm-mix recycled binders by up to 35.0%, whereas E had little influence on the binder viscosity due to its surfactant nature. Besides, S performed much better in improving rutting resistance (with the increase of up to 411.3% in |G*|/sinδ) than E, while E exhibited superior fatigue performance (with the reduction of up to 42.3% in |G*|·sinδ) to that of S. In terms of the thermal cracking resistance, E had very slight influence and S even yielded an adverse impact (with the increase of up to 70.2% in Sa and the decrease of up to 34.1% in m-value). Further, S broadened the ranges of pavement service temperatures by about 12 °C, whereas E almost did not change the PG grades of the binders. Finally, regarding the characteristics of viscoelastic master curves, S considerably improved the dynamic modulus and lowered the phase angle of the binders over a wide range of frequencies and temperatures but led to the failure of the time-temperature superposition principle due to its thermorheologically complex nature. Nevertheless, in this regard, the effect of E was found very mild.

Thermal storage properties of polyurethane solid-solid phase-change material with low phase-change temperature and its effects on performance of asphalt binders

Preparing phase change materials (PCMs) with appropriate phase-change temperatures is of great significance in preventing the low-temperature disease in pavements. In this study, several polyurethane solid-solid PCM (PUPCM) samples were prepared via a two-step condensation reaction of polyethylene glycol, polytetramethylene ether glycol, 4,4′-diphenyl methane diisocyanate, and 4,4′-methylenebis-(2-chloroaniline). Considering the phase-change temperature and thermal stability, a PUPCM sample with a suitable molar ratio was used for the asphalt modification. The prepared materials were characterised by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, three indices of asphalt and viscosity tests, rotational viscometer tests, and other techniques. PUPCM samples with different soft and hard segment ratios exhibit different phase-change temperatures and enthalpies, and their physical, chemical, and phase-change properties are stable. When the ratio of soft and hard segments is 8:2 (PU-14), the freezing and melting temperatures were −2.7 °C and 12.9 °C, and the enthalpy was 46.8 J/g. The PUPCM modification of asphalt only involves physical miscibility. Adding PUPCM negligibly affects the high- and low-temperature performances of the modified asphalt binder. The viscosity of the PUPCM-modified asphalt binder is slightly higher than that of the original asphalt binder, and the storage stability of the modified asphalt binder is satisfactory. The addition of PUPCM improves the anti-ageing performance of asphalt, and the improvement becomes significant with increasing PUPCM content. Moreover, the phase-change energy storage properties of PUPCM in asphalt were found to be satisfactory. Hence, PUPCMs can potentially be used for asphalt modification to further improve the low-temperature performance of pavements.

A molecular insight into cracking of the asphaltene hydrocarbons by using microwave radiation in the presence of the nanoparticles acting as catalyst

This research aims to the microwave-assisted catalytic cracking of the asphaltene by using nanoparticles of SiO2, Al2O3, clay, and ZnO acting as a nanocatalyst. The nanoparticle-added oil samples were treated by microwave radiation at the radiation power of 1200 W for 10 min. After extracting the asphaltene, Nuclear Magnetic Resonance (NMR), Fourier Transformed Infrared (FTIR), elemental analysis, Energy-dispersive X-ray (EDX) spectroscopies, and Inductively Coupled Plasma Atomic Emission (ICP-OES) were implemented to characterize the treated asphaltene. Based on the characteristic results, aromatic fused rings have been slightly cracked due to the microwave radiation in the presence of the ZnO and Al2O3 nanoparticles. Besides, the average carbon number of the associated aliphatic chains was reduced to the range of 3.3–3.9 from 5.4 after the microwave radiation. In addition, the microwave radiation in the presence of the nanoparticles reduces the Vanadium and Nickel concentrations of the asphaltenes to 71–90% and 75–93% of the ones in the crude asphaltene, respectively. Based on the indexes, calculated from FTIR spectrums, the asphaltenes are adsorbed on the nanoparticles, leading to absorbing higher microwave energy. By adsorbing the polar functional groups of asphaltene on the nanoparticle, they are heated until the bond cracking, leading to asphaltene release. An analogical insight to the viscometric tests and asphaltene molecular structure showed that the reduction of the electrostatic forces and the Hydrogen interactions are the main reason for the lower tendency of treated asphaltene to aggregate. Based on this study, fine particles, co-producing with crude oil, could catalyze the asphaltene cracking during microwave radiation.

To Study the Mixing and Compaction Temperatures of Organophilic Nanoclay Modified Asphalt Binder

Abstract: The use of modified asphalt binders in hot-mix asphalt has steadily increased over the past several decades. Mixing and compaction temperatures of an asphalt binder plays a vital role in the production and placement of asphalt mixes but there are no standards for mixing and compaction temperatures for modified asphalt binder especially with Organophilic nanoclay. In this study the effect of nanoclay modified binder on mixing and compaction temperatures of asphalt mixture was observed using conventional test for asphalt mixture-softening point test, penetration test and rotational viscometer test. Five different percentages i-e 3, 3.5, 4, 4.5 and 5% of Nanoclay (modifier) are selected for three different binders (ARL 60/70, ARL 80/100 & NRL 60/70). Six different samples for each binder are prepared and conventional testing is carried out using standard procedures. With an increase in the percentage of Nanoclay the softening point values and viscosity values increases, similarly the penetration values decrease. The mixing temperature range is 155-165°C and compaction temperature range is 135-145 °C to achieve maximum density in the field

Performance Improvement Effect of Asphalt Binder Using Pyrolysis Carbon Black

The generation of waste tires is rapidly increasing. Waste tire pyrolysis is an alternative to waste tire recycling. The main substances extracted in the waste tire pyrolysis method include oil, carbon black, and iron. In this study, carbon black from the pyrolysis of waste tires was used to modify and improve the permanent deformation properties of the asphalt binder, and 0%, 5%, 10%, 15%, and 20% of pyrolysis carbon black by weight were mixed in raw asphalt, which is called AP-3 and AP-5. Laboratory tests, such as the softening point test, flash point test, rotational viscometer test, dynamic shear rheometer test, and bending beam rheometer test, were carried out. The use of pyrolysis carbon black increased the softening point and rotational viscosity at 135 °C. When using 15% PCB for AP-3 and 10% PCB for AP-5, the performance improvement effect of the resistance to permanent deformation was significant. The use of pyrolysis carbon black decreased fatigue at room temperature and improved the resistance of low-temperature cracking up to −12 °C but gave poor results at −18 °C.

A novel enzymatic method discriminating wheat pre-harvest sprouting from Late Maturity alpha-amylase

The primary quality assessor of wheat grain is the Hagberg Falling Number (FN) method. This is a viscometric test surrogate for α-amylase activity. Despite being used for over sixty years, FN has been increasingly scrutinised due to its low throughput, poor reproducibility and inability to differentiate between the causes of low FN including Pre-harvest Sprouting (PHS) and Late Maturity α-Amylase (LMA). Our study describes initial efforts to analyse a specific wheat flour set tailored for the identification of enzymatic candidates that would allow discrimination between PHS and LMA affected grains. Using the sensitive enzyme-coupled assay substrate R-AMGR3, results suggest that α-glucosidase (exo-α-glucosidase) is a potential enzyme marker candidate to specifically detect sprouted but not LMA-affected grain.

Effectiveness of Thermal Stimulation of Superplasticizers on Fresh Properties of Cement Mortar

Polycarboxylic acid-based superplasticizers are used in various types of concrete work. Wide variations in environmental temperatures are known to affect how well chemical admixtures perform as superplasticizers, influencing the properties of the concrete. However, little has been reported on changes in performance caused by thermal variations. Previous studies have reported that heating superplasticizers change the polymer structure, improving and sustaining cement particles' dispersibility. Moreover, the improved fluidity from thermal stimulation is not temporary. The effect has been observed to remain for about seven days, with the residual characteristics differing depending on the superplasticizers used. Therefore this study evaluates mortar stiffness when using thermally stimulated superplasticizers and evaluates how the stimulation affects construction performance using measures such as the flow and rheological properties (plastic viscosity) of fresh mortar, vane shear tests, blade viscometer tests, and mortar vibration box tests. Mortar's fluidity was found to improve by about 25% when using thermally stimulated additives, with plastic viscosity dropping by up to 45% and the stress likely to be needed for pumping also being reduced by about 16%. Filling speed was also found to increase by about 26%. Thus, thermal stimulation improves mortar and concrete construction performance, and it may be possible in the future to carry out the construction with fewer workers utilizing this technology’s benefits. The study indicates a need for further investigation of how thermal stimulation affects polymer molecules’ adsorption efficiency with cement to elucidate the mechanism at full scale and propose ways to adopt thermal stimulation at actual construction sites.

Effect of laboratory-produced cellulose nanofiber as an additive on performance of asphalt binders and mixes

In recent years, major initiatives have been taken to replace non-renewable materials with environmentally friendly and sustainable ones. The present study was undertaken to apply a scalable process for laboratory production of Cellulose Nanofibers (CNF) and to evaluate feasibility of using the produced CNF as a sustainable plant-based asphalt additive to improve the mechanical properties and durability of asphalt pavements. To achieve this goal, CNF was produced in the laboratory by applying electrospinning technique. Structure, morphology, and the size distribution of the produced CNF were evaluated using Scan Electron Microscopy. Also, tensile strength tests in two perpendicular directions were conducted on lab-produced CNF. The effect of incorporating different amounts of CNF in three types of asphalt binders, namely PG 58-28, PG 64-34, and PG 70-28 on fracture energy and dynamic viscosity of binder blends were evaluated by conducting Izod impact and rotational viscometer tests, respectively. Additionally, effect of CNF dosage in binder on its adhesion and moisture-induced debonding potential with aggregates of three different mineralogy was evaluated by conducting binder bond strength test. Furthermore, effect of incorporating CNF in asphalt mixes on their cracking, rutting, and moisture-induced damage potential was evaluated by conducting semicircular bend, Hamburg wheel tracking, and tensile strength ratio tests, respectively. From the tests conducted on asphalt binders and mixes, it was concluded that, incorporation of CNF resulted in an overall improvement in binder-aggregates adhesion, an asphalt binder with a higher fracture energy and dynamic viscosity, and an asphalt mix with a higher resistance to rutting, cracking, and moisture-induced damage.

Rheological and mechanical properties of fibre-reinforced cemented paste and foam backfill

ABSTRACT The properties of fibre-reinforced cemented paste backfill (CPB) and foam backfill (FB) were investigated through bench-scale vane viscometer, mini-slump and compression tests. Samples of CPB (no air entrained) and FB (10, 20, 30, and 40% air by volume) were made with four concentrations of sisal, basalt, or Nanofibrillated cellulose fibres (0, 0.2, 0.5, and 0.8%). The results show that air entrainment decreased the unconfined compressive strength (UCS) and yield stress of FB, while the addition of the three types of fibre helped to compensate the UCS and built stronger internal bonds and sound structures, which led to different failure characteristics.

Effects of styrene butadiene styrene and Lucobite on stone mastic asphalt performance

This study evaluates the performance of stone mastic asphalt road paving mixtures modified with two polymer additives: styrene butadiene styrene and Lucobite. The test samples were made from limestone aggregate, pure bitumen 60/70 and polymer additives of 3 and 5% by weight. Penetration, softening point and rotational viscometer tests were conducted to assess the effects of additives on the physical properties of modified binders. Marshall stability, indirect tensile strength, moisture susceptibility, four-point beam fatigue, dynamic creep and wheel track tests were also performed to compare the performance of modified samples against an unmodified control sample. According to the test results, the additives improved binder performance and resistance against moisture, permanent deformation and fatigue compared with a conventional mixture. Based on the results, asphalt modified by styrene butadiene styrene had improved moisture sensitivity, permanent deformation performance (from wheel track tests) and fatigue behaviour up to 15, 32 and 53% better than unmodified asphalt, respectively. Lucobite-modified mixtures improved these properties up to 14, 20 and 40%, respectively.

Correlation between asphalt concrete induced healing and rheological properties of asphalt binder

The induction heating-induced healing of asphalt concrete is an innovative method of crack repairing. As concluded in previous studies, the temperature of asphalt concrete, raised through the induction heating, directly affect the process of the induced healing. As the speculation in this study, not only the temperature level but also the rheological properties of asphalt binder at the relevant temperature affects the induced healing process in asphalt concrete. In this study, the correlation between zero shear viscosity of asphalt binder and induced healing efficiency of asphalt concrete was scrutinized. The neat and modified asphalt binders with carbon black and activated carbon were utilized in the asphalt concrete comprised of limestone and siliceous aggregates. Initially, the influences of specimen dimension on the rate of induction heating were investigated. Then, the zero shear viscosity of asphalt binders, resembling the low-speed movement of melted asphalt binder, was identified based on data acquired from the rotational viscometer test. The semi-circular bending test was conducted for assessing the induced healing process of the asphalt concrete under repeated cracking-healing loading scenarios. The analysis of the induced healing index for different asphalt concrete types confirms the concurrent influences of temperature level and rheological properties of asphalt binders. Moreover, it can be deduced that the zero shear viscosity and capability of asphalt binder to move at far low-speed play a pivotal role in the accomplishment of induced healing in asphalt concrete. The proposed approach can be beneficially used to characterize the induction heating-induced healing characteristics of asphalt concrete specimens made of different ingredients.

Rheology measurements of recycling oils and their aging resistance in asphalt binders

ABSTRACT Adding recycling oils (also called as ‘recycling agents’ or ‘rejuvenators’) into the asphalt mixtures with Reclaimed Asphalt Pavement (RAP) and Recycled Asphalt Shingles (RAS) is a widely adopted strategy for improving potential resistance to cracking of recycled asphalt pavements. This study investigates the rheolgoical properties of two Bio-Oils and two Re-refined Engine Oil Bottoms (REOB) by using Dynamic Shear Rheometer (DSR) and Rotational Viscometer (RV) tests at various testing conditions, as well as their chemical properties by using the Fourier Transform-Infrared Spectroscopy (FTIR) measurement. The results are compared for the recycling oils after the Rolling Thin-Film Oven (RTFO), 20- and 40-hours Pressure Aging Vessel (PAV) aging. Furthermore, these four recycling oils were blended with a base binder at a high ratio (50%) and measured for their complex shear modulus and viscosity at various aging levels, as well as their infrared spectra. At the end, two recycling oils were selected to blend with a base binder at low ratios (2.9% and 5.7%) and measured for the standard Performance Grade (PG) properties and PG plus characteristics. The results of oil-asphalt low ratio blends indicate that recycling oil’s content plays an important role in aging behaviour of the binders, not only the type of recycling oils.

Effect of Basicity on the Structure, Viscosity and Crystallization of CaO-SiO2-B2O3 Based Mold Fluxes

In this study, the structure, viscosity characteristics, and crystallization behavior of CaO-SiO2-B2O3 based melts were studied combining molecular dynamics (MD) simulation, Fourier transform infrared (FTIR) spectroscopy, rotating viscometer test, and FactSage thermodynamic calculation. The results showed that, in the ternary CaO-SiO2-B2O3 glass system, stable structural units of [SiO4]4− tetrahedral, [BO3]3− trihedral and [BO4]5− tetrahedral were formed, and the Si-O and B-O structure depolymerize with the basicity increase from 1.15 to 1.25, then the B-O structure become complex with the basicity further increase to 1.35. In fluorine-free mold fluxes, with the basicity increases, the viscosity at 1300 °C increases, the liquidus temperature decreases and then increases, the network structure polymerizes, it indicates that the structural complexity rather than the melting property change plays a predominant role in increasing the viscosity at 1300 °C. Moreover, due to the changes in crystallization phase and solid solution ratio, the viscosity-temperature curve of fluorine-free slag shows the characteristics of alkaline slag and the break temperature increase with the basicity increase. The MD simulation, FTIR experiment, viscosity test, and FactSage calculation results are verified and complemented each other.

Evaluation of Polymer Modified Asphalt Mixtures in Pavement Construction. (Dept. C)

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Assessment of Hydraulic Conductivity of Some Nigerian Hardwood Timbers to Four Timber Treatment Chemicals through Quantitative Anatomical Studies

Aim: Hydraulic conductivity following the Hagen-Poiseuille Law is a quantitative approach to determine the treatability of wood by chemicals. The hydraulic conductivities of the ten selected Nigerian hardwood timber species to four wood treatment chemicals were estimated, using Hagen-Peiseuille equation.
 Materials and Methods: Ten timber species of marketable size and age were sourced from the forestry Departments of Enugu, Anambra and Abia States of Nigeria. Maceration were carried out following standard procedures. The viscosities in centipoises (cp) of the four wood treatment chemicals were measured in a viscometer test, while the hydraulic conductivities were calculated using the Hagen-Peiseuille equation.
 Results: The results obtained show that the different woods responded differently to the chemicals. Treatment with Folithion 200 showed higher conductivity in Triplochiton scleroxylon (9.01 mm-3S-1× 10-5), followed by Mansonia altissima, Milicia excelsa and Terminalia superb. The order of conductivity to treatment with Actellic 25EO was Terminalia superba > Mansonia altissima > Gmelina arborea, > Khaya ivorensis. Ceiba pentandra gave the highest conductivity of 8.58 mm-3S-1× 10-5, followed by Afzelia africana and Canarium schwenfurthii to the chemical Termitox. While Triplochiton scleroxylon gave the highest conductivity of 6.52 mm-3S-1×10-5, followed by Milicia excels and Terminalia superba to the chemical Solignum.
 Conclusion: Folithion 200 would be effective on Milicia excels, Mansonia altissima and Gmelina arborea, Actellic 25 EO would be effective on Khaya ivorensis, Terminalia superb and Antiaris toxicaria while Termitox would be effective on Ceiba pentandra, Afzelia Africana and Canarium schweinfurthii.

Effect of optimized short-term aging temperature on rheological properties of rubberized binders containing warm mix additives

This study investigates the effect of warm mix asphalt (WMA) additives and base binder, on the rheological properties of crumb rubber modified binder (CRMB-55) at higher temperatures. The rheological properties of the base binder VG-30, VG-40, and CRMB-55 are subjected to optimized short-term aging and compared with its unaged condition. WMA such as Sasobit and Rediset additives enhance the CRM binders by optimizing the mixing temperature by reducing it to 18 °C through the rotational viscometer (RV) test. This optimized temperature is implemented on the RTFO aging temperature at 177 °C and compared with both standard mixing temperature of 163 °C for the base binder and 195 °C for the crumb rubber modified binder to simulate the ideal mixing viscosity and to determine its rheological properties. In this study, the dynamic shear rheometer (DSR) is employed to measure the complex shear modulus (G*) and the phase angle (δ) of all the binders at various short-term aging temperatures. The Fourier transform infrared spectroscopy (FTIR) and the Scanning Electron Microscopy (SEM) are also applied to justify the effects of the WMA additives on the CRM binders in terms of chemically and morphological properties. It is identified that the two WMA additives can improve the rheological properties of the CRM binders more effectively by optimizing the short-term aging temperature, and greatly enhance the viscoelastic properties at the high-temperature condition for the CRM binders. It is found that Sasobit has the most remarkable effect on G* and δ at 177 °C RTFO-aged for CRMB-55 than with the Rediset WMA additives, and always suggest implementing this optimized short-term aging temperature for CRM binders before evaluating any rheological behaviour.

Nonlinear modelling of selected micro- and macro-properties of weathered asphalt mixtures

Asphalt mixture specimens with three different gradations of AC-13, SMA-13, and Superpave-13 were aged in an accelerated weathering machine (AWM) for a duration of 0, 1000, 2000 and 3000 h. Gel Permeation Chromatography (GPC), Fourier Transform Infrared Spectroscopy (FTIR) and Brookfield viscometer tests were performed on the recovered asphalt binder samples from the weathered mixtures. Nonlinear models fitted the measured properties by a method of LM+ universal global optimization of 1stOpt software. The results showed that: 1) Nonlinear models fitted the measured properties well, the rate and the degree of aging of the asphalt binders can be well explained by the parameters of these models. 2) As the aging duration is increased, Brookfield viscosity of the weathered asphalt binders increased gradually, and the percentage of Large Molecule Size (LMS) from GPC and the functional group of carbonyls (C=O) from FTIR increased as well. 3) The calculated values by the established models were highly correlated with the measured values of the properties of the weathered asphalts.