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Moisture damage resistance assessment in asphalt mixtures traditionally relies on the tensile strength ratio (TSR) method, which may not capture the complex behavior of asphalt under moisture ingress. This study proposes an innovative multifaceted approach for assessing moisture susceptibility, challenging the overreliance on TSR, and integrating multiple intricate aspects of asphalt behavior. Employing two dense-graded and one gap-graded polymer-modified binder mixtures with nominal maximum aggregate size (NMAS) of 13 and 19 mm, the study defines threshold values for total air voids, effective air voids, indirect tensile strength, and percentage density change. Evaluations were conducted using a device selected for its dynamic capabilities in inducing stresses and creating pore pressure under elevated temperatures. This research proposes a new zone-based approach to classify mixtures as moisture-resistant, partially moisture-resistant, or moisture-susceptible. This innovative method, grounded on maximum effective air voids and percentage density change, offers nuanced insights for more accurate moisture resistance assessments. Furthermore, the study explores the effect of effective air void size on moisture damage resistance by image processing for dense and gap-graded gradation of 13.2 NMAS, unveiling clogging behavior especially in dense-graded mixture due to smallest pore size. In conclusion, the study provides an in-depth understanding of asphalt mixture behavior under moisture ingress. By offering a novel approach that integrates multiple parameters and extends beyond the conventional TSR approach, it contributes a practical solution for mitigating moisture damage in asphalt mixtures. This research sets the stage for a potential paradigm shift in the approach to moisture susceptibility assessment, enriching the asphalt field with critical insights. [ABSTRACT FROM AUTHOR]

The present study aimed to understand the impact of inert-active filler combinations on cracking and resistance of asphalt mastic using work of fracture approach. A control grade asphalt binder (VG-30) and three fillers (inert: basalt (B); active: hydrated lime (HL) Nano hydrated lime (NHL)) were considered. The HL and NHL were added from 0% to 20% at 5% increment rate by weight of binder. The dosages of B were adjusted with respect to specific filler to binder ratios (0.6 to 1.2). The study focused on the influence of NHL on cracking resistance of mastic by means of ductile and fracture behaviour, evaluated using double edge notched tension test (DENT) at intermediate temperature condition. Findings indicated a beneficial impact in improving the cracking and fracture resistance of mastic due to reduction in the size of HL (NHL). The results signify that both HL and NHL can enhance the resistance to withstand ductile failure and fracture. Also, mastic prepared with B-NHL can be less susceptible to fracture over B-HL and hence, possessed improved ductile properties. Consequently, a lower dosage of NHL found to be superior over a higher dosage of HL in improving the cracking and fracture resistance of asphalt mastic. [ABSTRACT FROM AUTHOR]

Long-term aging of asphalt binder plays a major role in fatigue cracking resistance of asphalt mixes. With the use of polymer-modified binder (PMB) with different polymer concentrations, aging susceptibility of asphalt mixes becomes an interesting area to explore. This study evaluated four types of asphalt mixes prepared with PMB, subjected to compacted mix aging (CMA) (85°C, 5 days) and loose mix aging (LMA) (85°C, 8 days). The aged asphalt mixes were tested for their resistance to cracking using the indirect tensile asphalt cracking test (IDEAL-CT). Furthermore, aged binders were extracted from long-term-aged loose and compacted mixes, and their fatigue resistance was examined using the Superpave fatigue factor (|G*|·sinδ), linear amplitude sweep (LAS) test, and binder yield energy test (BYET) parameters. The results indicated that both asphalt binder and mixes exhibit better cracking resistance in CMA conditions compared to LMA conditions. Mixes prepared using PMB with higher polymer content performed better in cracking resistance and were less sensitive to aging. Furthermore, to evaluate the effect of rheology of aged binder on fatigue cracking resistance of mixes, binder fatigue parameters were correlated to cracking index (CTindex) and postpeak slope (|m75|) of mixtures. Other than the yield energy parameter of BYET, a good correlation was observed between binder fatigue and mix fatigue parameters. Outcomes of this study will potentially help to understand the relationship between mixture cracking parameter and standard binder fatigue parameters and their aging sensitivity. [ABSTRACT FROM AUTHOR]

The recent emphasis on adopting the balanced mix design (BMD) concept has encouraged highway agencies and practitioners to explore simple performance tests to capture the rutting performance of asphalt mixes. Though many researchers have adopted the Hamburg wheel tracking test (HWTT) to evaluate rutting resistance, certain limitations, such as using this test method during quality control/quality assurance (QC/QA) are challenging. Therefore, researchers are exploring ways to implement surrogate simple performance tests, namely the ideal shear asphalt rutting test (IDEAL-RT) and the high-temperature indirect tensile strength test (HT-IDT) to support QC/QA of asphalt mixes. However, establishing limiting threshold values of rutting parameters based on such simple performance tests is still in the research stage. Eight mixes with different types of aggregates, binders [unmodified, polymer-modified binder (PMB), and crumb rubber–modified binder (CRMB)] and gradations having different nominal aggregate sizes (NMAS) were collected from various plants. HWTT, IDEA-RT, and HT-IDT were conducted on samples compacted at 7%±0.5% air voids using the Superpave gyratory compactor. The data analysis showed that the rutting resistance index (RRI) parameter derived from HWTT are promising and advantageous compared with final rut depth, as it incorporates the combined effect of rut depth and number of passes. The study presented correlations of different rutting parameters (shear strength, RTIndex , and HT-IDT strength) derived from IDEAL-RT and HT-IDT with the HWTT RRI parameter. Moreover, to ascertain the pass/fail criteria of asphalt mixes, critical threshold values were proposed and recommended for shear strength, RTIndex , and HT-IDT strength as 1.0 MPa and 65 and 135 kPa, respectively. IDEAL-RT followed by HT-IDT are the most suitable potential surrogate simple performance tests for HWT to screen better and worse rutting performance. [ABSTRACT FROM AUTHOR]

This study explored a new simple monotonic Marshall rutting test (Marshall-RT) to evaluate the rutting resistance of asphalt mixtures. The Marshall-RT test setup combines the Marshall fixture (at the bottom) and the IDT fixture (at the top). The rutting resistance of asphalt mixtures was evaluated using peak load (Pmax) and work done for the deformation damage obtained from the load-displacement curve. Nine plant-produced asphalt mixtures having different types of binders (unmodified, crumb rubber modified binder (CRMB)), and polymer modified binder (PMB)) and gradations having different nominal maximum aggregate sizes (NMAS) were evaluated. The Marshall-RT test parameters (i.e. Pmax and $W_{P_{{\rm max}}}$ W P m a x ) have shown a strong correlation with fundamental (i.e. Flow Number (FN)), simulative (i.e. Hamburg wheel tracking test (HWTT)), and simple monotonic (i.e. Ideal rutting test (IDEAL-RT)) rutting tests. Moreover, the Marshall-RT test has shown good repeatability, the highest differentiation potential, and consistent ranking with other rutting tests. Furthermore, for high traffic levels (i.e. 100 MSA (Million Standard Axle)), at 50°C preliminary minimum threshold criteria were proposed for Marshall-RT (Pmax and $W_{P_{{\rm max}}}$ W P m a x ), and IDEAL-RT (RTIndex) as 5 kN, 14 kN-mm, and 90, respectively, to avoid premature rutting failure. Thus, the newly developed monotonic Marshall-RT test can also be used as a surrogate simple performance test to estimate the rutting potential of asphalt mixtures during the mix design and plant production phases as quality control (QC)/quality assurance (QA). [ABSTRACT FROM AUTHOR]

This study explored a new simple monotonic Marshall rutting test (Marshall-RT) to evaluate the rutting resistance of asphalt mixtures. The Marshall-RT test setup combines the Marshall fixture (at the bottom) and the IDT fixture (at the top). The rutting resistance of asphalt mixtures was evaluated using peak load (Pmax) and work done for the deformation damage obtained from the load-displacement curve. Nine plant-produced asphalt mixtures having different types of binders (unmodified, crumb rubber modified binder (CRMB)), and polymer modified binder (PMB)) and gradations having different nominal maximum aggregate sizes (NMAS) were evaluated. The Marshall-RT test parameters (i.e. Pmax and $W_{P_{{\rm max}}}$ W P m a x ) have shown a strong correlation with fundamental (i.e. Flow Number (FN)), simulative (i.e. Hamburg wheel tracking test (HWTT)), and simple monotonic (i.e. Ideal rutting test (IDEAL-RT)) rutting tests. Moreover, the Marshall-RT test has shown good repeatability, the highest differentiation potential, and consistent ranking with other rutting tests. Furthermore, for high traffic levels (i.e. 100 MSA (Million Standard Axle)), at 50°C preliminary minimum threshold criteria were proposed for Marshall-RT (Pmax and $W_{P_{{\rm max}}}$ W P m a x ), and IDEAL-RT (RTIndex) as 5 kN, 14 kN-mm, and 90, respectively, to avoid premature rutting failure. Thus, the newly developed monotonic Marshall-RT test can also be used as a surrogate simple performance test to estimate the rutting potential of asphalt mixtures during the mix design and plant production phases as quality control (QC)/quality assurance (QA). [ABSTRACT FROM AUTHOR]

Moisture-induced stress tester (MIST) has been recently developed to simulate the dynamic stresses that cause moisture damage. In the current study, asphalt mixes containing 0%, 10%, 20%, 30%, and 40% RAP were subjected to 0, 1000, 2000, 3500, 5000, and 10,000 stress cycles of MIST and IDT strength test was conducted. The test results were analysed using the concepts of survival and atrophy to propose a damage mechanism and suggest an alternative to TSR. In unconditioned state, the control mix depicted a superior survival as compared to RAP mixes with <20% RAP, and an inferior survival as compared to RAP mixes with >20% RAP. Rate of atrophy indicated that the control mix has a higher instantaneous potential to fail (2.34 MPa in unconditioned state for control mix) than RAP mixes (0.90, 1.07, 1.13 and 1.21 MPa for 10%, 20%, 30%, and 40% RAP mix, respectively, in the unconditioned state). Stiffness and peak stress carrying capacity for control mix in unconditioned state was 310.87 and 1.47 MPa, respectively, which was higher than RAP mixes. For RAP mixes, MDRs based on rate of atrophy and TSR were > 80% thereby indicating that RAP has the potential to improve the moisture-induced damage resistivity of asphalt mixes. [ABSTRACT FROM AUTHOR]

Fillers are known as dust fractions in asphalt mixes having a predominant particle size less than 75 micrometer (μm). Typical filler concentration in an asphalt mix varies from 4% to 12% (by aggregate weight). The effects of filler intrinsic properties on mastic behavior can get magnified with the concentration of filler. Thus, in filler-rich mixes like stone matrix asphalt (SMA), the filler characteristics and concentration can be sensitive factors, playing significant roles in the performance of asphalt mastic and mix. The study considered six different types of fillers to capture the effect of filler characteristics on mastic. The mastics were prepared with a constant filler concentration by volume (F/Bvol=0.49), which was determined by a typical SMA mix design. The fillers were characterized based on their surface area, size distribution, shape, Rigden voids (RV), clay content, and chemical composition. The filler effects on mastic were evaluated based on the stiffness (complex modulus) and stiffness ratio. The weak correlation observed between the mastic stiffness and the fixed and free binder reveals that the RV and filler fixing factor (FFF) can mislead regarding the stiffening potential of filler material. The surface areas by Brunauer–Emmett–Teller (BET) and Blaine's methods were insufficient to represent the stiffening potential while the stiffness showed a better correlation with the concentration of finer gradations in the filler evinced by a higher coefficient of P10 (percentage passing 10 μ sieve size) and fineness modulus (FM) parameters. Further, the micromechanics based understanding of mastic behavior explains the mastic stiffening phenomenon as the combined effects of adsorbed asphalt layer thickness and interparticle interaction. The linear relation observed between stiffness ratio and newly derived micromechanism stiffening factor (MMSF) indicates that in filler-rich mastics, the stiffness may be improved with a finer sized filler (lower FM) and higher volume concentration. However, the adsorbed layer thickness didn't show correlation with any of the filler properties considered. The study recommends a limiting value for mastic stiffness in terms of stiffness ratio which is established based on MMSF factor. A limiting value for stiffness of mastic could be significant to avoid dry mixes and subsequent poor fatigue performance. [ABSTRACT FROM AUTHOR]

India is witnessing unprecedented growth in its road network. To meet the asphalt binder demand, distillation towers have been loaded with crude oil from different sources. Although the quality system is expected to guarantee reduced variability, a quality system based on traditional indexes may lead to high variability in binders of the same grade. Because India relies on traditional indexes for quality control, we aimed to quantify such variability and its impact specifically on moisture damage resistivity. Additionally, the response of binders from different sources in the short term and long term has also been evaluated. Five binder sources were selected, and they were meant to conform to the same viscosity grade. Thereafter, moisture damage assessment tests such as surface free energy (SFE) measurements, bitumen bond strength (BBS) test, rolling bottle test (RBT), and boiling water test (BWT) were performed in unaged, short-term aged, and long-term aged conditions. Additionally, variations in chemistry of the binders were assessed based on Fourier transform infrared (FTIR) spectroscopy. It was concluded that the chemical and moisture damage characteristics had a strong dependence on the source of the binder. Furthermore, there was substantial variability in the moisture damage performance for binders from different sources. This implied that quality systems based on traditional indexes may not be stringent enough to reduce the variability. The impact of aging on the moisture damage resistivity of the asphalt–aggregate system was also discussed. Given the limited information available in the literature on asphalt binder variability of the traditional grading system, the data reported in this study can serve as reference for future studies dealing with its characterization and assist in developing a strategy for reducing uncertainty related to the performance of asphalt mixes. [ABSTRACT FROM AUTHOR]

Moisture-induced damage of asphalt pavements constitutes a primary distress. To quantify the extent of moisture-induced damage efficiently, a moisture-induced stress tester (MIST) was developed. This study adopts varying stress cycles of MIST to condition the asphalt mixes without and with reclaimed asphalt pavement (RAP) to ascertain their moisture-induced damage resistivity. Hence, the control mix (0% RAP) and mixes containing 10%, 20%, 30%, and 40% RAP by weight were prepared and conditioned using 0, 1,000, 2,000, 3,500, 5,000, and 10,000 stress cycles of MIST. Thereafter, an indirect tensile (IDT) strength test was conducted on the prepared mixes. Using analytical approaches, the biaxial state of stress was defined to compute the static (ES,H) and average modulus (ES,A). Increasing stress cycles of MIST decreased the stiffness of control and RAP mixes. The compressive stress–strain curve (SSC) was plotted and utilized to compute the linearity and toughness index (TI) of control and RAP mixes. Increasing stress cycles of MIST were observed to increase the ductility of control and RAP mixes, whereas prepeak linearity was observed to reduce it. The TI increased with the increase in stress cycles of MIST. New moisture damage ratios (MDRs) were computed by utilizing ES,H and ES,A and compared with the commonly adopted tensile strength ratio (TSR). Based on such MDRs, it was concluded that RAP improves the moisture-induced damage resistivity of asphalt mixes. Statistical analysis indicated that both ES,H and ES,A have the potential to be good indicators of moisture-induced damage of control and RAP mixes. [ABSTRACT FROM AUTHOR]

The present study evaluated the effects of six different bitumen film thicknesses (0, 0.2, 0.4, 0.6, 0.8, and 1 mm); four polishing levels of aggregate [220, 400, 600, and 800 Silicon Carbide (SiC)]; three moisture conditioning temperatures (25°C, 40°C, and 60°C); and three different aging levels of bitumen (143°C, 163°C, and 173°C) on interfacial strength of basaltic-unmodified bitumen system using binder bond-strength (BBS) test. Further, two different basaltic aggregates were procured, and their interfacial bond with three different types of bitumen, namely, unmodified (VG30), polymer-modified (PMB40), and crumb rubber–modified (CRMB60) was evaluated. The results showed that basaltic aggregate with higher porosity (and thus higher rate of moisture absorption) showed lower bond strength, although the polishing level of both aggregates was kept at 220 SiC. Further, PMB40 had higher bond strength followed by VG30 and CRMB60, depicting the influence of crumb rubber particles on interfacial bonding behavior of CRMB60. The study showed that 220 SiC polished aggregates having 0.8-mm bitumen film thickness and conditioned at 40°C can provide appropriate results on aggregate-bitumen bond strength using the BBS test, which supports the recommendations provided in AASHTO T 361. Thus, the authors believe that the BBS test may be beneficial in evaluating aggregate-bitumen bond strength in the field. [ABSTRACT FROM AUTHOR]

The present study was undertaken to evaluate the effects of different warm mix asphalt (WMA) additives on bonding behaviour of asphalt binder and aggregates using two different approaches: (i) The surface free energy (SFE) method and (ii) The asphalt bond strength (ABS) test. The study involved two phases, the first phase involved measurement of the SFE of control, and WMA (Sasobit, Advera, and Rediset) modified asphalt binders by the Wilhelmy plate method, and aggregate's (limestone and granite) SFE by the dynamic vapour sorption (DVS) method. Thereafter, bond energies were computed using SFE method for understanding the bonding behaviour of WMA modified binders with different aggregates in dry and wet conditions. The second phase involved direct measurement of bond strength and failure pattern between asphalt binder and aggregate combinations by the ABS test in both dry and wet conditions. Furthermore, bond strength of all combination of asphalt binder and aggregates were compared by SFE and ABS methods. The results indicated that Sasobit and Advera effectively contributed in enhancing the cohesive energy of control binder, whereas Rediset decreased the cohesive energy of control binder. Bond strength of WMA modified binder depends on both aggregate type and WMA additives. The results show that asphalt binder with Sasobit can have better bonding performance with limestone (basic) aggregate, whereas, asphalt binder after addition of Advera showed better bonding performance with granite (acidic) aggregate. After wet conditioning, asphalt binders with limestone (basic) aggregate combinations exhibited cohesive failure showing minimal effect of water on bond strength compared to binders with granite (acidic) aggregate combinations which showed adhesive failure. The comparison of bond strength by mechanical ABS test and energy based SFE methods have shown a fair correlation between bond strength ratio (BSR) and energy ratio (ER). [ABSTRACT FROM AUTHOR]

Supplementary Cementitious Materials (SCMs) have been widely accepted in the concrete industry due to their varied advantages. However, the same reflects little in the case of Cementitious Stabilized Aggregates (CSA). The present work focuses on the potential and practical application of SCMs in CSA based on laboratory-based growth and performance analysis followed by their design aspects and economic advantages. Fly ash and Crushed Granulated Blast Furnace Steel Slag (GBFS) were chosen at 30% and 50% by weight of cement as partial replacement to cementitious material to prepare a cementitious stabilized mix of aggregates. Mechanical and microstructural properties were then assessed through critical tests like Unconfined Compression Strength (UCS), Flexural Strength (FS), Flexural Modulus (FM) and Thermogravimetric Analysis (TGA) over subsequent curing periods. Results from these tests revealed improved performance on including SCMs in significant proportion when compared to cement mix of aggregates. Power-law relationships proved optimal for comprehending strength and stiffness growth in CSA. Mixes with SCMs exhibited higher growth coefficients and growth rates for UCS, FS and FM. TGA data showed higher bound water loss %, indicating increased hydration for SCMs mixes. Composite pavement design revealed a 5 mm increase in the bituminous layer for cement-fly ash mix, while it remained unchanged for cement and cement-GBFS mix. Economic analysis demonstrated SCM cost savings of 6% to 16% in the CSA layer in mixes with SCMs. [Display omitted] • Performance Evaluation of fly ash and GBFS-infused CSA through FM, FS and UCS. • Results showed enhanced mechanical performance, supported by TGA findings. • Simulated power-law relationships in CSA for strength and stiffness behaviour. • Composite pavement design with SCMs-infused CSA showed significant cost savings. [ABSTRACT FROM AUTHOR]

The present study was undertaken to investigate the impact of a unique combination of fillers on interfacial bond strength and moisture-induced damage potential of asphalt mastic. One asphalt binder (AC-30), three fillers including Basalt (B), Hydrated Lime (HL), and Nano-Hydrated lime (NHL) were selected to prepare asphalt mastics for a wide range of filler-binder (f/b) ratio (0.6 to 1.2). The dosages of HL and NHL were considered 0%, 5%, 10%, 15%, and 20% by weight of asphalt binder, and the dosage of B filler was adjusted to meet the respective f/b ratio. The interfacial bond strength and moisture-induced damage potential of asphalt mastic specimens were determined using the Bitumen Bond Strength (BBS) test. The BBS test parameters inferred that both B-HL and B-NHL filler combinations can enhance the bond strength and moisture damage resistance of asphalt mastic. Besides, asphalt mastic composed of B-NHL filler can be less susceptible to bond failure and moisture damage with improved adhesion and cohesion properties than B-HL filler. Additionally, asphalt mastic composed of a lower percentage (10%-15%) of NHL filler showed better bond strength and moisture damage resistance over mastic composed of a higher percentage (15%-20%) of HL filler. Asphalt mastic prepared with an f/b ratio less than 1.0 was found to be suitable to achieve better performance considering the moisture-induced damage properties. Grey relational analysis (GRA) method was used to analyze the correlation degree between filler properties and moisture damage properties of asphalt mastics. Based on the GRA results, Rigden voids and specific surface area are suggested to be the two most influential properties on the moisture-induced damage potential of asphalt mastic. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) is a nanomaterial that is characterized by a two-dimensional, atomically thin, honey-combed lattice. Studies over the years have indicated potential applications of GO for improving performance characteristics of asphalt binder. This study attempts to explore the impact of GO on various chemical and rheological characteristics of unmodified asphalt binder (AC30). GO was added to AC30 over varying dosages of 1%, 2%, and 3% by weight. Carbon (C), hydrogen (H), and nitrogen (N) determinations and Fourier-transform infrared (FTIR) spectroscopy aided in understanding the chemical interaction of GO with AC30. Further, the effect of GO on dynamic viscosity was also evaluated. Rutting performance of GO-modified AC30 was studied using the multiple stress creep recovery (MSCR) test, whereas fatigue performance was evaluated based on the linear amplitude sweep (LAS) test. Additionally, yield energy GO-modified AC30 was comprehended using the binder yield energy test (BYET). CHN determination and FTIR spectroscopy indicated that modification of GO is mostly physical in nature. An improvement in aging resistivity was observed due to incorporation of GO. GO was observed to increase dynamic viscosity. Improvement in both rutting and fatigue performance of AC30 was observed but different optimum dosages of GO were obtained: 1% for maximum rutting performance and 2% for maximum fatigue performance. Enhancement in yield energy and recovery potential was also observed. [ABSTRACT FROM AUTHOR]

This study evaluates important functional characteristics such as dispersion, aging resistivity potential, temperature susceptibility, and high temperature storage stability of Carbon Nano Tube (CNT) modified asphalt binders. CNT content was varied as 0%, 0.4%, 0.75%, 1.5% and 2.25% by weight of control binder (AC-10). Scanning Electron Microscopic (SEM) images was captured to get direct observation of CNT dispersion. Viscosity was further measured to understand the workability and dispersion characteristics. Further, viscosity temperature susceptibility parameters (A and VTS), activation energy and Penetration Index (PI) values were estimated to evaluate temperature susceptibility. SEM images and viscosity data showed that CNT content up to 1.5% may be recommended without potential problem of entanglement/clustering. Similarly, analysis of softening point, complex modulus and phase angle data showed positive effect of CNT on aging resistivity potential. Such improvement in functional characteristics can be attributed to high specific surface area (190 m2/gm), higher aspect ratio (length/diameter = 645) and excellent mechanical properties of CNT. Likewise, high temperature storage stability was evaluated using softening point and Multiple Stress Creep Recovery (MSCR) tests. Though softening point test method showed sufficiently stable nature of CNT under high temperature storage condition, settling of CNT (unstable nature) was observed from MSCR testing approach. [ABSTRACT FROM AUTHOR]

In this study, geometric features (e.g. road and shoulder width), pavement characteristics (e.g. shoulder type, skid number, and international roughness index), and traffic parameters (e.g. posted speed limit and average daily traffic) were extensively analyzed to identify the significant predictors and develop better-fit 85th percentile speed prediction models for the tangent sections of two-lane rural highways. Three models, representing all highways, lower speed limit highways, and higher speed limit highways, were developed using stepwise multiple linear regression analysis. About 80% data from 251 locations in the State of Oklahoma, United States, was used in model development and 20% for validation. The all highways model is the best-fit among the three. Two most significant parameters of this model are posted speed limit and skid number. Additionally, international roughness index is significant in the higher speed limit highway model. The lower speed limit highway model depends only on the posted speed limit. [ABSTRACT FROM AUTHOR]

The present study evaluates the effects of three different stages of crushing mechanism, namely two stage (2S), three stage (3S) and four stage (4S) on various morphology parameters (i.e. angularity, texture, flatness & elongation, sphericity and form2D) of aggregates. The 2S crushing consisted of primary and secondary crushers as Jaw and HSI (horizontal shaft impactor), respectively, while 3S crushing was composed of primary, secondary and tertiary crushers as Jaw, Jaw and HSI, respectively. In other word, 3S consisted of an additional jaw crusher compared to 2S crushing. Likewise, 4S crushing had primary, secondary, tertiary and quaternary crushers as Jaw, Jaw, HSI and VSI (vertical shaft impactor), respectively. The 4S had an additional VSI crusher to 3S crushing. Three coarse and three fine aggregate sizes were used in the study. A digital device, Aggregate Image Measurement System was used to measure various morphology parameters of aggregates and to assess the effects of stage crushing. The coarse aggregates were subjected to angularity, texture, sphericity and flatness and elongation, while fine aggregates were studied for angularity and form2D. A systematic statistical analysis was conducted to compare the mean value of aggregates shape parameters and draw logical conclusions. It was observed that effects of crushing on aggregate shape are a cumulative function of stage crushing, crushing mechanism and aggregate size. The outcome of the present study may be helpful in understanding effects of stage crushing mechanism on shape parameters of aggregates for quality production. Further, the study can assist in selection of an appropriate source of aggregate and crusher health monitoring via morphological characterisation of aggregates. [ABSTRACT FROM AUTHOR]

Application of condition number (CN) approach is critical in selecting appropriate combination of probe liquids for evaluating the surface free energy (SFE) of bitumen. The CN approach recommends use of probe liquids with CN<10, however, several researchers have used probe liquid combinations having CN>10 without concerning its adverse effects on the SFE of bitumen. Inappropriate choice of probe liquids may result in incorrect SFE values of bitumen, thereby influencing its compatibility with aggregates. Therefore, the present study is strongly motivated to exhibit the application of CN approach for selecting appropriate probe liquids. Further investigating the impact of CN on aggregate-bitumen compatibility, the present research work also aims at validating CN approach. A polymer modified bitumen (i.e., PMB40) and two types of aggregates namely, quartzite, and basalt aggregates were selected in this study. Five probe liquids namely, water, formamide, diiodomethane, ethylene glycol and glycerol were selected, which formed ten different combinations of probe liquid triplets. The CN of probe liquid triplets was calculated based on singular value decomposition (SVD) method. Thereafter, using the SFE of aggregates and bitumen, compatibility of basalt-PMB40 and quartzite-PMB40 was evaluated using compatibility ratio (CR) parameter. Results revealed that except for probe liquids triplets with CN<10, the aggregate-bitumen compatibility was highly inconsistent when evaluated using probe liquids triplets having CN>10. Therefore, the present study addresses the adverse effect of inappropriate selection of probe liquids on aggregate-bitumen compatibility and also validates the CN approach. [ABSTRACT FROM AUTHOR]

• This work compared the rheological and chemical properties of virgin AC30 binder and equivalent grade AC10 binder obtained by blending RAP binder. • The proportion of RAP binder to be blended with AC10 was obtained using viscosity and PG blending charts. • RAP proportion was also determined based on performance tests such as LAS and MSCR. • RAP proportion obtained by various contrasting methods was compared. Use of reclaimed asphalt pavement (RAP) material in mixes is on the rise. Currently, RAP proportion to reach the target binder grade is determined by absolute viscosity and performance grade (PG) methods. However, it is necessary to compare the RAP proportion recommended by the two methods. Further, it is essential to ascertain whether the RAP blended target binder is equivalent to virgin target binder based on various rheological and chemical properties. In this study different percentages (i.e. 0%, 15%, 25%, 40% and 50% by weight of binder) of RAP binder was blended with base binder (AC10). RAP proportion to achieve target grade (AC30) was determined based on absolute viscosity, PG, LAS and MSCR tests. Absolute viscosity and PG methods recommended the RAP proportion of 48% and 32% respectively. Thereafter, average of the two RAP proportions was blended with AC10 binder to obtain target grade of AC30 (AC30_RAP). AC30_RAP was observed to have a higher fatigue life than AC30 binder at lower strains and the trend reversed at higher strain. Higher recovery (R) and lower non-recoverable creep compliance value (J nr) was exhibited by AC30. FTIR spectroscopy indicated that AC30_RAP had higher sulphoxide and carbonyl content. LAS and MSCR tests recommended the RAP proportion of 35% and 48% based on fatigue and rutting performance respectively. [ABSTRACT FROM AUTHOR]

• 280 SiC polished aggregates are suitable to determine SFE using SD method. • ABS is more sensitive than SFE to capture effect of short-term aging temperatures. • Field aging of asphalt binder at temperatures lower than 163°C is undesirable. In the field, roughness of aggregates varies during production process due to abrasion, stripping and ravelling, which influences its bonding potential with asphalt binder. However, no study relating aggregate roughness levels and bond strength of aggregate-binder system was conducted. In addition, change in short-term aging temperature of asphalt binder during production processes may affect aggregate-binder bond. Therefore, present study evaluates effects of aggregate roughness and short-term aging temperature of binder on bond strength based on surface free energy (SFE) and asphalt bond strength (ABS) test approaches. For the purpose of the study, basalt aggregate was polished using 220, 400, 600 and 800 grade silicon carbide (SiC) powders and their roughness values were measured using zeta-profiler. Also, AC30 binder was short-term aged using rolling thin-film oven (RTFO) at temperatures 143 °C, 163 °C and 173 °C. Bond strength was evaluated using energy ratio (ER) and bond strength ratio (BSR) parameters, obtained from SFE and ABS approaches, respectively. Bond strength of aggregates having different roughness values was evaluated with standard short-term aged binder (163 °C for 85 min) whereas, bond strength of binder aged at different temperatures were evaluated with 220SiC polished aggregate. The present study also validates use of 280SiC polished aggregates as recommended by AASHTO T-361, by examining relationship between aggregate roughness and BSR. Results showed that bond strength increases with increase in aggregate roughness and short-term aging temperature of binder. Further, one-way ANOVA and Post-Hoc test showed significant effect of aggregate roughness and binder aging levels on aggregate-binder bond strength. Markedly, linear correlation was observed between ER and BSR with aggregate roughness and binder short-term aging conditions. [ABSTRACT FROM AUTHOR]

The present study evaluates the effects of two different aggregate production (crushing) mechanism, i.e. Jaw-Horizontal Shaft Crusher (HSI) named as JH and Jaw-Jaw-HSI-Vertical Shaft Impact Crusher (VSI) known as JJHV on aggregate dimension distribution. Both crushing mechanisms represents wide range of crushers and stage of crushing (i.e. JH and JJHV as two-stage: 2S and four-stage: 4S, respectively). The study considered three different size of coarse aggregates, namely P19-R12.5, P12.5-R9.5 and P9.5-R4.75. The aggregate dimensions are measured using aggregate image measurement system (AIMS). Further, the dimension based parameters, i.e. Flatness (F), Elongation (E) and Flatness and Elongation (F&E) were determined. In addition, the dimension distribution of aggregate is further analyzed using Zingg distribution, where the aggregate is classified in Rod (R), Blade (B), Disk (D) and Cube (C). The study also discuss algorithm behind measurement of aggregate dimensions using image analysis in AIMS. The result shows that aggregate produced from two stage crushing had higher F and higher E compared to four stage. Similarly, JH produces higher percentage of aggregates with given F&E ratio (i.e. 1:3 and 1:5) compared to JJHV. Additionally, it was found that stage crushing had more significant effect on F compared to E. Further, the Zingg classification revealed that compared to JH, JJHV produces more cube shape aggregates. Whereas, inverse trend was observed for percentage of particle in B and R ranges. Additionally, it has been observed that in image analysis aggregate orientation and pixel spread is function of individual particle co-variance matrix. [ABSTRACT FROM AUTHOR]

To evaluate the contribution of different pavement layers to rutting failure, a 304-meter-long (1,000 feet) test section was constructed on Interstate 35 near Purcell, Oklahoma. The section was comprised of five layers: two Hot Mix Asphalt (HMA), one aggregate base, one stabilized subgrade, and natural subgrade layers. Rutting was measured on the pavement section for approximately six years. The rutted profiles of the test section were compared with those in National Cooperative Highway Research Program (NCHRP) Report 468. Significant rutting value of 22.04-millimeter (0.868 inch) was observed on the test section. To further investigate, trenches were cut at three selected locations having highest, lowest, and average rutting. It was observed that the HMA layers, more specifically the surface layer, contributed to most of the rutting. Minimal to negligible rutting was observed in the aggregate base, stabilized, and natural subgrade layers. Furthermore, the MEPDG rutting models were calibrated based contribution of each of the layers, and the optimized calibration coefficients were: βr1 = 1.35, βr2 = 1, βr3 = 1.05 for HMA; βGB = 0.05 for aggregate base, and βSG = 0.05 for natural subgrade. Results from this field study provide an insight on the behavior of different pavement layers in addressing rutting problems in future designs. [ABSTRACT FROM AUTHOR]

The present study aimed at investigating the effect of Recycled Asphalt Pavement (RAP) binder on high and intermediate temperature performance of Polymer Modified Binders (PMB) through advance laboratory characterization techniques. Different RAP binder proportions (0%, 15%, 25% and 40% by the weight of PMB) were initially blended with PMB. Different characterization techniques such as Superpave rutting parameter (G*/Sinδ), Shenoy parameter, Multiple Stress Creep Recovery (MSCR) and Zero Shear Viscosity (ZSV) tests were used for evaluating high temperature performance. Based on the different rheological parameters, improvement in rutting performance was observed with the addition of RAP binder. Likewise, intermediate temperature performance was evaluated using Linear Amplitude Sweep (LAS), Double Edge Notch Tension (DENT) and Elastic Recovery (ER) test. The improvement in high temperature performance and degradation in intermediate temperature performance shows that care must be taken while selecting the appropriate amount of RAP based on prevalent failure type in the field. [ABSTRACT FROM AUTHOR]

Crumb rubber modified (CRM) binder has high working temperatures, which may be reduced with addition of warm mix additives (WMA). The dynamic mechanical analysis of CRM binder containing three different WMA additives, namely Fischer–Tropsch wax-based (FT), water-based (WB) and chemical surfactant-based (CS) additive, was undertaken in the present study. The CRM binder was blended with different percentages (by weight of asphalt binder) of WMA additives, i.e. FT (1, 2 and 3%), WB (4, 6 and 8%) and CS (1, 2 and 3%). The viscosity, rutting and fatigue performance of CRM binder with and without WMA additives were evaluated using Brookfield viscosity, multiple stress creep recovery and linear amplitude sweep tests, respectively. The FT modification effectively reduced the viscosity of CRM binder, while the inclusion of CS showed similar viscosity and WB increased the viscosity of CRM binder. The WB modification observed to create foaming effect in asphalt binder. The FT- and WB-modified CRM showed same High Superpave performance grade (PG), however, the addition of CS degraded high PG of CRM binder (from PG88 to PG82). The CRM binder showed reduced Jnr value and improved R-value after FT and WB modification, indicating improved rutting resistance. Whereas, CS-modified CRM indicating poor rutting performance (high Jnr and low R). Asphalt binder combinations showed significantly different rutting performance parameters (Jnr and R-value), whereas they were graded as E. Therefore grading of asphalt binders based on AASHTO MP 19 should be relooked. All WMAs improved the Nf i.e. fatigue resistance of CRM binder. The 2% FT dosage observed to be optimum for CRM binder. The study showed that selection of WMA additives should not only be based on viscosity criterion but also rheological performance parameters are to be looked into for making appropriate conclusions about their effectiveness. [ABSTRACT FROM AUTHOR]

• CNT addition improve the rutting performance of asphalt binder. • CNT addition may increase the stress sensitivity of asphalt binder. • It is desirable to have a higher value of η m for improved rutting performance. • Modified power law can model nonlinear strain response in the recovery period. • CNT addition also improve the performance of asphalt binder under sustained loading. The present study aimed at evaluating the rutting performance of Carbon Nano Tube (CNT) modified asphalt binder under different loading conditions. CNT content was varied as 0%, 0.4%, 0.75%, 1.5% and 2.25% by the weight of control binder. Superpave rutting parameter (G*/Sinδ) and Shenoy parameter (G*/(1-(1/TanδSinδ))) were initially evaluated using temperature sweep test. Though both parameters showed a similar trend, the later one found to have more sensitivity towards evaluating unrecoverable strain value. Creep-recovery test was further conducted at four different stress levels (100 Pa, 3200 Pa, 5000 Pa, and 10000 Pa) to understand the effect of CNT under cyclic loading-unloading condition. Improvement in recovery value and a corresponding decrease in non-recoverable creep compliance value was observed with the addition of CNT. Further attempt was made to model the strain response from creep-recovery test using the Burgers model and Power model. Based upon the variation of viscous component of steady flow obtained from the Burgers model, CNT addition found to improve the rutting performance. Further, the power model also showed an excellent prediction of strain response under creep period, however, deviation from the experimentally observed response was observed in the recovery period. Modification to the power law model was done which significantly improved the strain prediction in the recovery period. Likewise, the effects of CNT under sustained loading condition was evaluated using a creep test at two different stress levels (100 Pa and 3200 Pa). Incremental dosages of CNT shifted the binder response from linear to nonlinear viscoelastic region at comparatively lower creep period. Significant decrease in deformation rate was also observed with CNT addition. [ABSTRACT FROM AUTHOR]

• Recycling of simulated Polymerized RAP produced using standard laboratory aging techniques. • Mix aging is better to simulate RAP from SBS PMB with 3 to 4% SBS. • Standard aging methods have distinct impact on performance of aged recycled PMB. Researchers have mostly used three artificial aging techniques, namely pressure aging vessel (PAV) binder aging, compacted mix aging (CMA), and loose mix aging (LMA) to simulate recycled asphalt pavement (RAP) binder in the laboratory. RAP binder (RAPB) simulated using different techniques will differ in characteristics and may affect the performance of the base binder differently. Which may affect the parameters used for blending and recycling, such as the selection of base binder, rejuvenator dosage, etc. Therefore, in this study, three RAP binders, namely RAPB-P, RAPB-C, and RAPB-L, were simulated from a polymer modified binder (PMB) with 3.5% SBS content, using PAV aging (100 °C, 20 hrs, 2.1 MPa), CMA (85 °C, 5 days) and LMA (85 °C, 8 days), respectively. These polymerized RAPBs were added to an unmodified binder (AC 30) at three proportions: 15 %, 25 %, and 40 %. These RAPB and AC 30 blends were characterized in terms of their dynamic viscosity, mixing and compaction temperature, and high temperature performance grade (PG). Superpave rutting factor (|G*|/sin δ) and multiple stress creep and recovery (MSCR) test parameters were used to evaluate the rutting performance of the RAPB blended AC 30 binders. Further, resistance to yielding and elastic recovery values were evaluated using the binder yield energy test (BYET). The test results suggested that all three RAP binders affect the performance of the AC 30 binder differently, which was also confirmed by statistical analysis using one-way ANOVA. From MSCR and BYET test results, it may be stated that RAP binder simulated from standard PAV aging may mislead in predicting the high and intermediate temperature performance of AC 30 binder with RAPB. Overall, the present study is helpful for asphalt researchers and practitioners to understand how the selection of different defined aging strategies affects the performance of aged recycled PMB with unmodified base binder. [ABSTRACT FROM AUTHOR]

The paper presents a performance case study to investigate the effects of micro trenching (MT) technique on structural perfor mance of asphaltic pavements. The study was conducted on a flexible pavement in the city of Mumbai to place underground optic fiber cables. The structural performance of asphaltic pavement was determined using Benkelman beam deflection (BBD) and indirect tensile strength (ITS) test before and after MT. The study includes both dry and wet sections in MT application to understand the effect of moisture conditioning on structural performance of asphaltic pavement. The effect of time after MT reinstatement i.e. 4 hrs and five days were also considered during structural evaluation. In addition, the study presents detailed discussion on the number of steps followed right from site selection to final MT reinstatement (i.e. selection of MT alignment using ground penetrating radar (GPR) survey, depth and width selection of MT, coring, reinstatement etc.). The BBD test result showed that minimal difference was observed in structural capacity of asphaltic pavement before and after five days of MT. Likewise, ITS results exhibited that bond between grouting material (SBS 2511 modified concrete named as SBSMC) and hot mix asphalt (HMA) layer was found to be intact. Finally, the study suggests various precautions and s uggestions for field execution of MT technique. It is expected that the advantage of MT technique in terms of structural performance along with other benefits such as costeffectiveness, environmental friendly, rapid laying etc. will encourage the application of MT technique as compared to other similar techniques. [ABSTRACT FROM AUTHOR]

Highlights • Development of semi-empirical correlation to predict actual CoF from theoretical CoF. • Wet adhesion was found to be highest contributor to the total theoretical CoF. • Dry adhesion of tire-basalt had least impact on the total theoretical CoF. • Hardness of rubber showed a good correlation with the actual CoF. Abstract The interaction between tire rubber and pavement surface depends upon their surface characteristics and physical properties. Presence of water on the pavement surface aggravates the interaction and decreases the skid resistance drastically. Due to the interfacial water, the real contact area between pavement and tire decreases, which leads to decreased Coefficient of Friction (CoF). It is reported that CoF in this triphasic system (tire- water – pavement) can be derived from three components: hysterical, dry adhesion (tire-pavement) and wet adhesion (tire- water – pavement). The present study analyses a mechanistic-empirical model to evaluate the CoF between pavement and tire in wet conditions considering Surface Free Energy (SFE) characteristics of materials. The present study was conducted on five distinct types of rubber samples prevalent in Indian condition with basalt rock chosen as the surface mimicking pavement. Physical properties of the rubber samples (Hardness, material yield strength and tan delta values) were determined according to the ASTM standards. SFE parameters were calculated by measuring the contact angles using Sessile drop method. Surface roughness of basalt aggregate was measured using a Zeta Profilometer. Actual friction coefficient was measured using British pendulum (BP) tester under wet conditions. Further, theoretical CoF was calculated by inputting the experimental material properties into mathematical model. The results showed that the wet adhesive friction was the main contributor to the theoretical CoF, whereas dry adhesive friction was the least. Also, the correlation between actual CoF and the material properties was tried. The actual CoF showed fairly good correlation with the hardness of the rubber samples (R2 = 0.95). The study concludes that the SFE based model to determine friction coefficient between wet pavement and road shows potential to ascertain the frictional interactions taking place between the two surfaces. [ABSTRACT FROM AUTHOR]

Utilization of ground tire rubber (GTR) binder in combination with reclaimed asphalt pavements (RAP) binder can provide added benefits in terms of material, cost and environmental saving, and hence a promising step toward sustainable construction of pavements. The present study utilized essential work of fracture (EWF) principal to evaluate performance of a GTR binder blended with two different types of RAPs: RAP-A and RAP-S, having different rheological properties. The GTR binder was mixed with different percentages (0%, 15%, 25% and 40% by weight of virgin binder) of RAP-A and RAP-S. First, Superpave performance grade (PG) of different combinations of asphalt binders was determined in the laboratory. Thereafter, the EWF of binders was determined using a newly developed double edge notch tension (DENT) test. Further, the data obtained from the DENT test were used to estimate critical crack tip opening displacement (CTOD). The results showed that addition of RAP decreased fracture resistance of GTR binder. Addition of RAP-A resulted in a faster decrease in performance of GTR binder compared to RAP-S. It can be concluded that low percentage of RAP may be utilized with GTR binder. Further, analyses indicated that RAP sources and its quantity could have significant impact on performance of asphalt mixes. [ABSTRACT FROM AUTHOR]

In the present study, intermediate temperature cracking performance of different types of asphalt binders containing warm mix asphalt (WMA) additives was evaluated using three test methods namely, Superpave fatigue parameter, linear amplitude sweep (LAS) and double edge notch test (DENT). The Superpave fatigue, LAS, and DENT tests are based on dissipated energy, viscoelastic continuum damage (VECD) and work of fracture approaches, respectively, and thus each of the tests may result into different performance ranking of asphalt binders. The outcome of the Superpave fatigue, LAS and DENT tests are G ∗ sinδ, number of cycles to fatigue failure (N f ), and critical tip opening displacement (CTOD) based on which cracking potential of asphalt binder can be assessed. An asphalt binder having a low Superpave parameter, high N f and high CTOD values are expected to have better intermediate temperatures cracking performance. The present study selected three control binders namely virgin (AC), styrene-butadienestyrene (SBS) and crumb rubber modified (CRM) binders were modified using three WMA additives namely Fischer-tropsch (FT) wax based, chemical surfactant (CS) based and water based (WB). Control binders were modified with 2%, 6% and 2% (by weight of asphalt binder) of FT, WB and CS, respectively, using a mixer. The results showed that, based on G ∗ sinδ and CTOD parameters, CS modification reduced stiffness (reduced G ∗ sinδ) and improved ductile performance (increased CTOD) of control binders. However, WB and FT modification increased stiffness and degraded the ductile performance of control binders, except for SBS with 6%WB binder which showed higher CTOD than control SBS binder. On the other hand, considering performance based on N f parameter, WMA additive modification improved fatigue life of control binders, except for SBS with 2%CS binder which showed lower N f as compared to control SBS binder. Control binders with and without WMA additives were ranked based on G ∗ sinδ, N f and CTOD parameters. AC and CRM binder with and without WMA additives followed similar performance ranking based on G ∗ sinδ and CTOD parameters. It is difficult to conclude over the best suitability of intermediate temperature performance parameter as mentioned tests involve different loading conditions and analysis approaches. Hence, further investigation on asphalt mixes is necessary to identify the best suited intermediate temperature performance parameter of asphalt binders, and its possible correlation with mix performance. [ABSTRACT FROM AUTHOR]

The present study evaluates two different methods for selection of probe liquids to determine the surface free energy (SFE) of asphalt binders: (i) Condition Number (CN) of probe liquids, and (ii) plot between cosine of total SFE ( ϒ L Cosθ) and total SFE of probe liquids ( ϒ L ) . Five different probe liquids, i.e. Water (W), Formamide (F), Ethylene Glycol (E), Diiodomethane (D), and Glycerol (G) were selected. Overall, ten different combinations of probe liquid triplets (W-G-F, W-G-E, W-G-D, W-F-E, W-F-D, W-D-E, G-F-E, G-F-D, F-E-D, and D-E-G) were formed to examine CN and plot of ϒ L Cosθ versus ϒ L . Three asphalt binders, namely unmodified (VG30), SBS polymer modified binder (PMB40) and crumb rubber modified (CRMB60) binders were selected for the present study. The contact angle of asphalt binders was measured using sessile drop method, and SFE of each of the selected asphalt binders was determined for all ten combinations of probe liquids. Thereafter, CN of probe liquid triplets was determined using Singular Value Decomposition (SVD) method. In addition, ϒ L Cosθ versus ϒ L plot was made for triplets using the measured contact angles of probe liquids. The CN approach and ϒ L Cosθ versus ϒ L plot were compared based on binder’s total SFE to identify a better approach for selecting appropriate probe liquid triplets. CN approach was observed to be superior compared to the plot of ϒ L Cosθ versus ϒ L . In fact, it was observed that the plot approach may not be valid for asphalt binders. [ABSTRACT FROM AUTHOR]

The present research work was undertaken to develop a simple empirical model to evaluate superpave rutting factor (G ∗ /Sinδ) and viscosity value for Nano Clay (NC) and Carbon Nano Tube (CNT) modified asphalt binders. The amount of NC was varied as 0%, 2%, 4% and 6%, while CNT was varied as 0%, 0.4%, 0.75%, 1.5% and 2.25% by the weight of control binder. Nanomaterial factors (NC f for NC modified and CNT f for CNT modified asphalt binder) and temperature factors were evaluated to develop the final empirical model for G ∗ /Sinδ and viscosity. NC factor (NC f ) as well as CNT factor (CNT f ) were found to have exponential variation for viscosity model. In case of G ∗ /Sinδ model, CNT f found to have quadratic variation due to reduction in stiffness value at higher CNT doses, whereas, NC f showed exponential variation. Development of empirical model for evaluating G ∗ /Sinδ and viscosity value for NC and CNT modified asphalt binders has been successfully demonstrated in the present paper. Overall, it is expected that the proposed models may be helpful to practicing engineers for making judicious decision on selection of amount of NC or CNT to improve rutting and workability requirement of asphalt binder. [ABSTRACT FROM AUTHOR]

Artificial Intelligence algorithm support vector regression (SVR) has proved successful in outperforming conventional Witczak and ANN models for estimation of dynamic modulus (E ∗ ) of asphalt mixes. However, there were two issues related to the development of E ∗ prediction models that the present study addresses. Firstly, since aggregates occupy almost 95% by weight of HMA, it is quite possible that the morphology of these aggregates play an important role in influencing the E ∗ values. To address this issue, aggregate shape parameters, namely, angularity, sphericity, texture and form were used with aggregate gradation for stiffness estimation. Secondly, to fine tune the hyper-parameters firefly algorithm (FA) was coupled with SVR. E ∗ tests of 20 HMA mixes having different sources, sizes of aggregates, and volumetric properties were conducted at 4 temperatures and 6 frequencies. Aggregate shape parameters were measured using the automated aggregate image measurement system (AIMS). SVR-FA models were developed that predicted the E ∗ with an R 2 of 0.98. SVR-FA models were compared with SVR and ANN models for E ∗ prediction. Further, a sensitivity analysis was conducted to identify the important input parameters. Lastly, an approach for formulation of SVR-FA model equations for direct prediction of HMA stiffness is also discussed. FA proved instrumental in improving the efficiency of SVR by optimizing the hyper-parameters with lesser manual effort. Finally, it was concluded that SVR-FA algorithm is capable of successfully predicting the E ∗ values using the aggregate shape parameters. [ABSTRACT FROM AUTHOR]

Durability and sustainability are two major requirements of the asphaltic pavement structure. Durability aspect may involve performance parameters such as fracture property, moisture sensitivity etc., whereas, sustainability aspect may involve utilization of Recycled Asphalt Pavement (RAP) and Warm Mix Additive (WMA) in the conventional asphaltic mixture. Though improvement in high temperature performance may be expected with the addition of RAP due to its stiffer nature, it may degrade intermediate temperature performance. Additionally, RAP utilization may also increase the mixing and compaction temperature during the construction phase. Therefore, researchers have recommended using different WMA additives to decrease production temperature of mixes containing RAP. Though the use of WMA additives with RAP may decrease mixing and compaction temperature, their effects on various performance parameters of the asphaltic mixture must be evaluated. Sufficient research works have been reported on the performance of RAP and WMA mixes at high temperature, however, so far, limited work is available on understanding effects of RAP and WMA additives on fatigue and moisture sensitivity of asphalt mixture. Therefore, the present research work aimed at evaluating intermediate temperature fracture properties and moisture sensitivity of asphaltic mixture containing RAP and WMA. Five different RAP contents (0%, 10%, 20%, 30%, and 40%), two different types of WMA additives (2% wax based “Sasobit” and 0.5% chemical based “Evotherm”) and one without WMA additive (Control mixture) were considered. Fracture properties of different asphaltic mixture combinations were evaluated using Semi Circular Bending (SCB) test. Improvement in fracture property of Control mixture was observed with increase in RAP content, however, the addition of wax based and chemical based WMA additives showed an overall reduction in fractured resistance. Further, the asphaltic mixture containing wax based WMA additive showed better fracture performance compared to the corresponding mixture containing chemical based WMA additive. Similarly, moisture sensitivity of asphaltic mixtures was evaluated using Tensile Strength Ratio (TSR) approach. Addition of both WMA additives resulted in lowered Indirect Tensile Strength (ITS) under dry as well as wet condition. Though the addition of WMA additive showed a negative impact on moisture sensitivity, all mixture considered in the present research work passed the minimum TSR requirement. Therefore, wax and chemical based WMA additive may deem acceptable from moisture sensitivity point of view. [ABSTRACT FROM AUTHOR]

Polyphosphoric acid (PPA) along with reactive elastomeric terpolymer (RET) are being used to enhance rheological performance of asphalt binders. However, PPA+RET modified asphalt binders results in higher working temperature, thus difficult to use it in practice. Therefore, some energy efficient warm mix additives (WMA) are used to decrease working temperature, to saving of energy and fuel. However, suitability of varieties of energy efficient additives for PPA+RET modified asphalt binders has not been evaluated so far. Similarly, performance of PPA+RET modified asphalt binder may deteriorate with addition of anti-stripping agent such as hydrated lime (HL), because acidic effects of PPA may be neutralized with basic nature of HL. The present study contributes to understand suitability of energy efficient additives and HL on bonding and debonding potential of PPA+RET asphalt binder (called Control binder) with two types of aggregates (basalt and granite) using surface chemistry based approach. The Control binder was blended with three different energy efficient WMA additives namely, Wax based (WB), chemical based (CB), and foam based (FB) along with HL. First contact angle of Control binder with WMA additives with and without HL was measured using Wilhelmy plate. Thereafter, acidic and basic surface free energy (SFE) components of selected asphalt binders were determined using acid-base theory. The SFE components of asphalt binders and aggregates were used to evaluate adhesion bond energies in dry and wet condition. Overall, the results showed that bonding potential of Control binder with selected aggregates decreased after addition of WMA additives. In fact, addition of HL with WMA additives further degraded the bonding potential of asphalt binders, thus nullifying the effects of anti-stripping agent. Out of three WMA additives, FB showed good results with HL compared to WB and CB. Basalt aggregates (basic) showed relatively better bonding behavior with Control asphalt after addition of WMA and HL additives as compared to granite (acidic) aggregates. [ABSTRACT FROM AUTHOR]

The present study evaluates moisture and fracture resistance performance of Hot Mix Asphalt (HMA) and Warm Mix Asphalt (WMA) containing different percentages of Reclaimed Asphalt Pavement (RAP) materials. The HMA and WMA mixes with different percentages of RAP (i.e., 0%, 10%, 20%, 30% and 40%) were designed using Marshall mix design. The warm mixes were prepared by adding 2% wax. Overall, 10 mixes (five HMA-RAP mixes, and five WMA-RAP mixes) were prepared in the laboratory. The moisture damage potential of different mixes was determined using Tensile Strength Ratio (TSR) test. Furthermore, fracture resistance of HMA-RAP and WMA-RAP mixes were evaluated using a Semi Circular Bending (SCB) test based on fracture mechanics principles. The analyses of results showed that addition of RAP increased TSR value of the mix, indicating that RAP may help in enhancing moisture damage potential of a mix. The TSR value of HMA-RAP mixes was found to be higher compared to WMA-RAP mixes for all RAP percentages, showing that WMA mixes are more prone to moisture damage compared to HMA mixes. The fracture resistance was found to be increasing with increase in RAP content in this research work. However, it is to be noted that improvement in fracture property with increase in RAP content may not be theoretically correct due to increase in stiffness characteristics. Such trend in the present research work may be attributed to absence of relaxation time in SCB testing protocol, unaccountability of post peak behaviour in the present research work and variability in material properties. Therefore, further investigation is needed in this direction to develop more understanding for such change before making further recommendation. Furthermore, the fracture resistance of HMA-RAP mixes was found to be better compared to WMA-RAP mixes. Overall moisture and fracture resistance performance of HMA-RAP mixes were observed to be better compared to WMA-RAP mixes. Moreover, Literature showed that asphaltic mixture containing RAP and WMA additive is highly influenced by amount of RAP and WMA added to HMA, type of WMA additive, source and nature of collected RAP etc. Therefore considering finding of current research work and reported literature in this area, inclusion of RAP in WMA mixes should be evaluated carefully before making further recommendation. [ABSTRACT FROM AUTHOR]

Shape characteristics of fine aggregates, namely angularity and form 2D are greatly associated with the types of rocks, mineralogical compositions, and allied crushing mechanism. Thus, for a given source and aggregate, the type of crusher may play a critical role in producing aggregates having different shape parameters. The present study was undertaken to compare shape parameters of fine aggregates produced from three different crushers, i.e. vertical shaft impactor (VSI), cone crusher (CC) and horizontal shaft impactor (HSI). Basaltic fine aggregates collected from three different crushers was divided into five sizes, namely FA1 (P4.75-R2.36: aggregate passing 4.75 mm and retaining on 2.36 mm), FA2 (P2.36-R1.18), FA3 (P1.18-R0.600), FA4 (P0.600-R0.300) and FA5 (P0.300-R0.150). The angularity and form 2D values of different sizes and types of fine aggregates were measured using Aggregate Image Measurement System (AIMS) in accordance with AASHTO TP 81. Further, conventional technique namely fine aggregate angularity (FAA) test was used to measure angularity of fine aggregates. Furthermore, Angle of Repose (AoR) test was conducted to identify influence of shape characteristics on particle packing behaviour. The study showed that both the techniques (i.e., AIMS and FAA) could differentiate among the quality of fine aggregates produced from different crushers. However, both techniques resulted in opposite trend in angularity of aggregates. The AIMS measurement showed that angularity and form 2D was highest for aggregates produced from HSI crusher followed by CC and VSI. On the other hand, FAA showed that aggregates produced from CC crusher had maximum angularity followed by VSI and HSI. Conclusively, the AIMS showed that HSI crusher could produce aggregates with highest angularity, while FAA showed that this type of crusher might produce aggregates with least angularity. Curiously, the AoR values showed no significant difference for the fine aggregates produced from different crushers. The interrelation between angularity and form 2D is also discussed in the paper. [ABSTRACT FROM AUTHOR]

Addition of Warm Mix Additives (WMA) is expected to cause viscosity reduction and hence could offer lower working temperature. However, it is equally important to study effects of WMA additives on rutting and fatigue behavior of binder. Therefore, the current study aims to investigate rheological characterization of a control SBS polymer modified binder (PMB) with and without WMA additives through different tests such as viscosity, Supepave high performance grade (PG), multiple stress creep recovery (MSCR), linear amplitude sweep (LAS). Three WMA additives namely Sasobit® (wax based) (Wax-S), Rediset® (chemical/surfactant based) (Che-R) and Advera® (water based/ zeolite) (Zeo-A) were used in the present study. The PMB was mixed with three different percentages of Wax-S, Che-R and Zeo-A, thus a total of ten binders were prepared in the laboratory. The results showed that addition of Wax-S and Che-R decreased viscosity of PMB, while addition of Zeo-A increased viscosity of PMB. Wax-S additive was found to bump high PG and enhance rutting and fatigue performance of PMB. Che-R additive degraded high PG and also deteriorated rutting and fatigue performance. Similarly, Zeo-A additive reduced high PG and showed negligible effects on rutting and fatigue performance. The study showed that viscosity might not be considered as a sole criterion for selection of WMA additive. Some WMA additives may decrease viscosity, however, they may also degrade short-term and long-term performance of binders. Thus, a proper caution should be taken while selection of a WMA additive for a type of binder. [ABSTRACT FROM AUTHOR]

Modification of asphalt binder with Elvaloy (Elv) and polyphosphoric acid (PPA) has been reported to have better performance. However, such modification may increase mixing and compaction temperatures of asphalt binder. Furthermore, the positive effect of PPA may get neutralized with the addition of lime, which can lead to inferior performance of asphalt binders. Recently, different types of warm mix additives (WMA) are being introduced to reduce production and construction temperatures of asphalt binder. However, the effects of WMA additives with and without lime on various rheological response of PPA + Elv modified asphalt binder is not well understood so far. Therefore, the present study was undertaken to evaluate the rutting and fatigue performance of PPA + Elv modified asphalt binder (referred as Control binder) containing threeWMAadditives (water, chemical, and wax-based) with and without lime. The multiple stress creep recovery (MSCR) and linear amplitude sweep (LAS) tests were conducted to capture the rutting and fatigue performance of asphalt binders, respectively. The results show that rutting and fatigue performance of Control asphalt binder decreased with the addition of chemical and water-based WMA additives. The performance of Control asphalt binder further deteriorated when these WMA additives (chemical and water) were used with lime. Interestingly, the addition of wax showed higher rutting resistance and similar fatigue life as that of Control asphalt binder. The addition of lime with wax additive showed improved rutting resistance and reduced fatigue life compared with Control asphalt binder. Regardless of the type of WMA additives, the addition of lime decreased the fatigue life of Control asphalt binder. The adverse effect of lime was prominent when used with wax compared with water and chemical-based WMA additives. Furthermore, the addition of WMA additives increased the stress sensitivity of Control asphalt binder. The stress sensitivity of asphalt binder further increased when wax and chemical-based WMA additives were used with lime. However, use of water-based WMA additive and lime reduced the stress sensitivity of Control asphalt binder. Overall, it can be concluded that the performance of Elv + PPA modified asphalt binder depends largely on the type of WMA additives and their combination with lime. [ABSTRACT FROM AUTHOR]

• Four different air voids and 60% RAP are studied on the performance of the CMA. • Hamburg wheel tracking and semi-circular bending tests conducted. • Correlation between properties of rut depth and TSR performance of CMA are studied. • Strong correlation between resilient modulus and ITS of CMA. In recent decades, cold mix asphalt (CMA) has become increasingly important in the pavement construction industry. CMA differ from hot mix asphalt (HMA) in the formulation process; CMA is produced by combining unheated aggregates with or without recycled asphalt pavement (RAP) using asphalt emulsion. One of the major concerns associated with CMA is difficulty in compacting the mix in the field. Many researchers have reported that cold mixes despite of best compaction efforts can have air voids in range of 8–14%. The authors were unable to locate research that focused solely on the influence of consequent air voids in cold mixes on their performance. Thus, the strong motivation of the present study was to evaluate performance characteristics of cold mixes having wide range of compaction levels. CMA was prepared by using 60% of RAP containing slow setting emulsion. Superpave gyratory compactor (SGC) was used to compact the CMA samples at different air voids of 6, 8, 10, and 12%. Tensile Strength Ratio (TSR) is the ratio of ITS value of conditioned and unconditioned samples. The moisture damage resistivity of CMA with various air voids was determined using different conditioning procedures: 24-hour soaking and moisture induced stress tester (MIST). Soaked TSR satisfied all air voids, however the MIST-TSR(M-TSR) of CMA with 12% air voids is below the threshold value of 80%, indicating that M-TSR is more severe than soaked TSR. Flexible pavement suffers from various types of distresses, such as cracking and rutting. Hamburg wheel tracking test (HWTT) can be used to evaluate rutting and stripping potential. The lower the inflection point for stripping, the more severe the stripping in the field. This study concluded that the stripping inflection point for 8% air voids was three times more than for 12% air voids. Marshall stability and flow test was performed to evaluate the effect of varying air voids on stability, flow, and bearing capacity of CMA whereas the durability was determined using Cantabro mass loss (CML) Test. It is expected that the findings of this study will assist the researchers in understanding how the air voids in CMA affect the performance containing RAP. [ABSTRACT FROM AUTHOR]

This study focused on evaluating the rutting performance of three different highly polymer-modified asphalt (HiMA) binders (i.e., O, T and B) using binder-based [i.e., multiple stress creep recovery (MSCR) and force ductility (FD)] and mix-based [flow number (FN) and Hamburg wheel tracking test (HWTT)] rutting performance tests. The binder-based rutting indicators were compared with mix rutting performance to determine a parameter that can help in the correct prediction of HiMA rutting resistance. In addition, the study looked into application of a simple performance test, the indirect rutting tolerance index (IDEAL-RT), for HiMA mix rutting prediction. The MSCR test revealed different rankings of recovery at 0.1- and 3.2-kPa stress levels. Moreover, the T and B binders did not satisfy the stress sensitivity criteria (Jnr_difference) of Max 75%. The force ductility tests revealed that the peak force observed for polymer network phase in HiMA was significantly higher than base binder stiffness, which is in contrast with force distribution in polymer-modified binders (PMBs). The mix rutting resistance ranking (O>T>B) was similar in all the tests (i.e., FN, HWTT, and IDEAL-RT). Although IDEAL-RT can be used to compare the rutting resistances of HiMA mixes, detailed future work is required to establish its acceptability in comparing various types of mixes and the minimum requirements of RTIndex. The comparison between binder and mix rutting indicators demonstrated that MSCR testing on binder at stress levels of 6.4 kPa and higher can be used to predict the rutting resistance of HiMA binders. Parameters like slope and cohesion energy and a newly introduced parameter—work done for polymer activation (WPA)—from FD tests can be used to determine the polymeric phase dominance in HiMA binders. Overall, this study provides pavement stakeholders with a framework for rightly predicting the rutting resistance and polymeric phase dominance of HiMA binders and mixes using MSCR, FD, and IDEAL-RT tests. [ABSTRACT FROM AUTHOR]

The current study compared aggregate shape parameters and laboratory performance of coarse aggregates produced from two different types of crushing operations. The coarse aggregates from two type of crushing operations, (1) a series of jaw (J)-cone(C)-vertical shaft impactors (V), called JCV, and (2) a series of jaw (J) and horizontal shaft impactors (H), called JH, were selected in the present study. The coarse aggregates collected from both crushing operations were separated into five different sizes ranging from 4.75 to 25 mm. The shape parameters [angularity, texture, sphericity, and flatness (F) and elongation (E)] of different sizes of coarse aggregates were measured using the aggregate image measurement system (AIMS) device. Further, the influence of aggregate shape parameters on their packing behavior and stability were evaluated by conducting three laboratory tests: void in coarse aggregate (VCAdrc), angle of repose (AoR), and the direct shear test (DST). The results showed that both the JH and JCV series of crushers produced aggregates with similar angularity; however, significant differences were observed in texture, sphericity, and F and E of aggregates. The aggregates produced from the JH crusher were found to have higher VCAdrc, AoR, and friction angle compared to aggregates from the JCV crusher. The results showed that aggregates obtained from the JH crusher may have better interlocking and stability than aggregates from the JCV crusher. [ABSTRACT FROM AUTHOR]

The present study was undertaken to evaluate rutting, fracture and thermal cracking resistance behavior of asphalt mastic containing inert and active fillers. A control neat binder (AC-30) along with basalt (B) as an inert filler and hydrated lime (HL) as active filler were selected in this study. The asphalt mastics were prepared for different percentages of HL (5, 10, 15 and 20%) filler, in such a way that Filler to Binder (F/B) ratio becomes 0.8. A total of five combinations of asphalt mastic were prepared such as: AC-30 + 80% B + 0% HL, AC-30 + 75% B + 5%HL, AC-30 + 70% B + 10%HL, AC-30 + 65% B + 15%HL, and AC-30 + 60% B + 20%HL. The rutting, fracture and thermal cracking resistance of asphalt mastics was evaluated using Superpave rutting factor parameter, Double Edge Notched Tension (DENT) and Bending Beam Rheometer (BBR), respectively. Influence of HL on the performance of neat asphalt mastic was observed to be predominant in high-temperature range as obtained from the G ∗ /Sinδ value. The aging resistivity of asphalt mastic increased with the inclusion of HL, indicating a better rutting performance of asphalt mastic. The intermediate-temperature performance of asphalt mastic with HL was found to be higher compared to neat asphalt mastic from Critical Tip Opening Displacement (CTOD) results, implying better resistance to fracture. The addition of HL increased the low-temperature performance of asphalt mastic obtained from S(t) and m(t) values with S(t) and E(t) master curve, indicating enhanced resistance to thermal cracking. The combined effect of B and HL filler on the G ∗ /Sinδ, CTOD, S(t), m(t) and E(t) parameters are presented in this study. In addition, ranking of asphalt mastics based on various parameters (i.e. CTOD and m(t)) is discussed in this paper. [ABSTRACT FROM AUTHOR]

The present study was undertaken to understand the moisture damage resistance of unmodified and ground tire rubber (GTR)-modified asphalt binders containing three different type of warm mix asphalt (WMA) additives using the surface free energy (SFE) approach. The SFE parameters of unmodified and GTR-modified asphalt binders with and without WMA additives were determined in the laboratory using theWilhelmy plate method. The SFE of two types of aggregate, namely, granite and limestone, were adopted from literature. Thereafter, work of adhesion, work of cohesion, work of debonding, and energy ratio (ER) were estimated for a total of 16 different combinations of aggregate and asphalt binder. An attempt was made to evaluate sensitivity of SFE parameters with elemental composition (carbon, hydrogen, nitrogen, and sulfur) of asphalt binder. The results showed that moisture damage resistance of unmodified and GTR-modified asphalt binder decreases with addition of WMA additives. The control asphalt binder with Rediset (Akzo Nobel, Netherlands) showed better bond with aggregate, followed by Sasobit (SasolWax, Hamburg, Germany) and Advera (PQ Corporation, Malvern, Pennsylvania). The limestone aggregate showed better moisture damage resistance compared with granite aggregate. The elemental composition (CHNS) of an asphalt binder found to have a fair correlation with SFE parameters. [ABSTRACT FROM AUTHOR]

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

The traffic input parameters in the Mechanistic Empirical Pavement Design Guide (MEPDG) are: (a) general traffic inputs, (b) traffic volume adjustment factors, and (c) axle load spectra (ALS). Of these three traffic inputs, the traffic volume adjustment factors specifically monthly adjustment factor (MAF) and the ALS are widely considered to be important and sensitive factors, which can significantly affect design of and prediction of distress in flexible pavements. Therefore, the present study was undertaken to assess the sensitivity of ALS and MAF traffic inputs on rutting distress of a flexible pavement. The traffic data of four years (from 2008 to 2012) were collected from an instrumented test section on I-35 in Oklahoma. Site specific traffic input parameters were developed. It was observed that significant differences exist between the MEPDG default and developed site-specific traffic input values. However, the differences in the yearly ALS and MAF data, developed for these four years, were not found to be as significant when compared to one another. In addition, quarterly field rut data were measured on the test section and compared with the MEPDG predicted rut values using the default and developed traffic input values for different years. It was found that significant differences exist between the measured rut and the MEPDG (AASHTOWare-ME) predicted rut when default values were used. [ABSTRACT FROM AUTHOR]

Due to its economic and environmental benefits, using reclaimed asphalt pavement (RAP) and reclaimed asphalt shingles (RAS) in new hot-mix asphalt (HMA) has become an integral part of today's asphalt industry. The advantages of using RAP and RAS in HMA are not limited to economic and environmental benefits, and may result in improving a number of mix performance characteristics including rutting and resistance to moisture-induced damage. Despite aforementioned benefits, concerns over premature pavement distresses resulting from using RAP and RAS limit their usage in HMA. Furthermore, because of the lack of mechanistic performance data, use of new mixes containing RAP and RAS remains limited. Therefore, the present study was undertaken to investigate the effects of using different amounts of RAP and RAS on laboratory performance of HMA, and to generate valuable input design parameters for implementation of the mechanistic-empirical pavement design guide (M-EPDG), using local materials. Four types of base course mixes containing 0% RAP, 25% RAP, 40% RAP and 20% RAP+5% RAS, and three types of surface course mixes containing 0% RAP, 25% RAP and 20% RAP+5% RAS were tested. Laboratory tests were conducted to evaluate stiffness, low-temperature cracking, fatigue life, rut and moisture-induced damage potential of the mixes. It was found that dynamic modulus and creep compliance of the asphalt mixes increase and decrease, respectively, with an increase in the amount of RAP and/or RAS used in the mix. Fatigue life was found to increase with increasing RAP content up to 25%, and to decrease when the RAP and/or RAS content exceeded 25%, or when RAS was used in the mix. It should be noted that this conclusion was drawn based on a 15% increment in RAP content. Hamburg wheel tracking (HWT) test results showed increased resistance to rutting and moisture-induced damage, with an increase in the amount of RAP and/or RAS. However, the tensile strength ratio test results were not confirmed by HWT. The findings of this study are expected to be helpful in understanding the effects of using different amounts of RAP and RAS on the performance of asphalt mixes produced using local materials. Furthermore, valuable design input parameters, developed in this study for new mixes containing RAP and RAS, may be used for calibration of the M-EPDG input parameters, with local materials. [ABSTRACT FROM AUTHOR]

The present study evaluates effects of reclaimed asphalt pavement (RAP) obtained from two different sources on fracture and low temperature cracking resistance of a polymer modified binder (PMB). Two different RAPs, one from urban highway (RAP-A) and other from rural highway (RAP-S) were collected. The binder extracted from RAP-A and RAP-S had different viscosity, rheological and chemical characteristics. The binder extracted from RAP-A was found to have higher viscosity and stiffer nature compared to RAP-S. The PMB binder was blended with different proportions (i.e., 0, 15, 25 and 40% by weight of binder) of RAP-A and RAP-S. The double edge notched tension (DENT) test was conducted to evaluate fracture cracking potential of PMB binder containing different percentages of both the RAPs. Further, low temperature cracking potential of RAPs blended binders was measured using bending beam rheometer (BBR) test. The results from the DENT test showed the second peak in the load-displacement curve for the control PMB disappeared with addition of RAPs, indicating damage to polymer interlinking. Inclusion of RAP-A (urban highway source) in PMB resulted in a smaller critical crack tip opening displacement (CTOD) value compared to RAP-S (rural highway source). The statistical analyses showed that lower percentage of RAPs (i.e., 15% RAP-A and 15% RAP-S) had similar effect on CTOD value of PMB, however, at higher percentage of RAPs (25% and 40%), both RAPs found to behave differently. The BBR test showed that addition of RAPs resulted in increase in stiffness and decrease in m-value, indicating poor low temperature cracking potential of PMB. The addition of RAP-A resulted in lower m-value compared to RAP-S. Based on the DENT and the BBR tests, it can be concluded that the PMB binder with RAP-A could be more fracture susceptible compared to binder with addition of RAP-S. The low temperature performance grade (PG) of PMB did not change significantly with addition of even 40% of both the RAPs, which is contrary to what is being reported in literature. The findings presented in the paper showed that RAP source and its proportions can have different impact on performance of mixes, thus assuming that nature of RAP binders remains same irrespective of change in a source may lead to premature failure of a pavement. [ABSTRACT FROM AUTHOR]

Recent impetus on utilization of different types of nanomaterials for modification of asphalt binders has motivated the authors to undertake the present study. The present study evaluated the rutting, fatigue and moisture damage performance of nanoclay (CL-30B) modified asphalt binder based on newly adopted test methods. Based on Superpave rutting parameter, it was observed that rutting resistivity of a binder increases with an increase in CL-30B content. Moisture resistivity of CL-30B modified asphalt binder with different types of aggregates system was studied using Surface Free Energy (SFE) approach. The SFE components of nanoclay modified binder were measured using Wilhelmy plate method. Four different types of aggregates (Basalt, Limestone, Sandstone and Granite) were chosen for the study. Overall increase in total SFE of the binder was observed with addition of CL-30B. Increase in work of cohesion and decrease in work of debonding was observed with an increase in CL-30B for all type of considered aggregate. Based on Energy ratio (ER), asphalt binder with basaltic aggregate was found to have better moisture damage resistivity among different types of aggregate selected in this study. The fatigue performance of CL-30B modified binder was evaluated using Linear Amplitude Sweep (LAS) test which is based on Visco Elastic Continuum Damage (VECD) theory. The analyses of the data showed that addition of CL-30B enhances fatigue life of a binder. The study showed potential of CL-30B to enhance various rheological performance of a binder for better and long lasting pavements. [ABSTRACT FROM AUTHOR]