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The Arkansas Department of Transportation (ARDOT) Maintenance Division is concerned about the use of certain aggregates in asphalt mixture because of their durability and performance issues. Good performance of the pavements can be ensured by selecting good-quality aggregates along with asphalt binders that can produce compatible aggregate–binder systems. The primary goal of this research was to determine proper asphalt binders and aggregates for the construction of highways in Arkansas. Three performance grade (PG) asphalt binders, namely PG 64-22, PG 70-22, and PG 76-22, prepared from two different crude sources, were investigated. This study also included four types of ARDOT-commissioned aggregates, namely gravel, sandstone, limestone, and dolomite, from four quarries throughout Arkansas. Selected properties of asphalt binders and aggregates (e.g., physical, mechanical, and chemical) were evaluated by performing a series of routine laboratory tests. To evaluate the performance of the asphalt mixtures, work of cohesion, work of adhesion, and boiling resistance tests were conducted. These aggregates, binders, and aggregate–binder systems were ranked based on the properties obtained from laboratory tests. In general, any combination of dolomite or limestone with a stiffer binder such as PG 76-22 or PG 70-22 is expected to be superior to an asphalt mixture with either sandstone or gravel. The outcomes of this research will help highway agencies and pavement professionals in selecting suitable asphalt binders and aggregates for long-lasting pavement construction. [ABSTRACT FROM AUTHOR]

Compatibility holds great importance because it can predict the overall performance of asphalt mixtures. Incompatible aggregate-binder duos can result in a weak and friable mix as well as increase mixtures' stripping potential. Being unaware, local agencies and contractors often struggle with premature pavement failure, which consequently places unexpected strain on the budget. Thus, this study assessed the compatibility among 18 asphalt binders with a performance grade (PG) of PG 64-22, PG 70-22, and PG 76-22, each collected from six different refineries; and eight different types of aggregates (sandstone, novaculite, limestone, and dolomite, each collected from two different quarries). Viscosity, penetration, pH, and work of cohesion values of binders were used to develop a binder ranking system. Similarly, the aggregates were ranked based on physical (specific gravity and absorption), durability (abrasion resistance and soundness), and chemical (pH and surface free energy) properties. Overall relative rankings of aggregates and binders were also provided by assigning weight factors to different tested parameters. A total of 144 aggregate-binder mixture systems were ranked based on their dry and wet work of adhesion values as well as Texas boiling test results. The compatibility ratio (CR) was also computed, and each of the systems was designated A, B, C, or D based on their relative CR values. Upon analysis, three binders (S2B2, S3B1, and S4B1) and three aggregates (DM2, LS2, and DM1) were designated as the most preferable construction materials. CR values predicted LS2, DM1, and DM2 mixtures as the most compatible mixtures. SS2, LS1, and DM2 mixtures showed the highest stripping resistance in the Texas boiling test. These databases are expected to help the agency and asphalt producers to select compatible binders and aggregates for producing durable asphalt concrete. This study covered a wide variety of aggregates and asphalt binders prevalent in but not limited to Arkansas. A database developed under this project was based on observed individual aggregates' and binders' performances as well as their combined performances. The information provided in this study will help contractors and agencies to choose the most appropriate aggregate-binder system within their reach for producing quality asphalt mixtures. By knowing the rankings, state agencies can adjust project budgets and assign timely rehabilitation due to the usage of less compatible aggregate-binder systems. Contractors can tweak the existing mix design if they must use local but inferior materials. This ranking will also help them to select project-specific materials depending on the project's significance. The refineries as well will have the opportunity to improve their products to be more compatible with local materials. [ABSTRACT FROM AUTHOR]

Asphalt binder often is modified to obtain better performance of the pavement. Some recent studies have considered nanoclay as an alternative to currently practiced styrene-butadiene-styrene (SBS) modification to reduce the asphalt binder's overall cost. This study evaluated any notable changes in the chemical composition of the binder due to the nanoclay modification and investigated any correlation between the chemical composition and mechanistic properties of the asphalt binder. It was found that changes in the chemical composition of nanoclay-modified binders are crude source–dependent. After nanoclay modification, the binders that originated from the Arabian crude were found to be more acidic than the binders from the Canadian crude source. However, nanoclays did not have any notable impact on the polarity of the tested asphalt binders regardless of their crude sources. The saturates, aromatics, resins, and asphaltenes (SARA) analysis results of asphalt binders revealed that the n -heptane insoluble contents increased notably after modification with nanoclays, whereas the saturates content decreased due to aging. Some mechanical properties (e.g., viscosity and rutting factor) were found to be correlated with n -heptane insoluble contents. Moreover, the sessile drop analysis test result showed that the nanoclay-modified binders offered superior bonding with gravel than with sandstone. Multiple linear regression analyses suggest that there is a fair (R2=0.55) correlation between the binders' SARA components and compatibility for gravel. [ABSTRACT FROM AUTHOR]

Moisture-induced damage in asphalt concrete is a major concern to the transportation agencies. Existing moisture sensitivity tests are mostly conducted at the macro- or micro-level and focused on the qualitative measurements only. In this study, the atomic force microscopy (AFM) technology is utilized to investigate moisture susceptibility of asphalt binders through the estimation of nano-level dissipated energy (DE). For the comparison of the AFM test results, two macro-level tests data are also used. Asphalt binders used in this study include a Performance Grade (PG) base binder (PG 64-22) along with its modified counterparts, which are blended with polyphosphoric acid (PPA), styrene–butadiene-styrene (SBS), and SBS plus PPA. Additionally, the effects of three different types of liquid anti-stripping agents (LAA) were investigated. The test specimens of these binder samples were prepared under dry and wet conditions, and their DE values were estimated from AFM tests. Results showed that the base binder and the PPA-modified binder had higher DE values than the SBS- or the SBS + PPA-modified binders. Among all the LAAs, Evotherm showed better resistance to moisture damage than the other ones. Findings of this study are expected to help highway agencies to quantify the moisture resistance of asphalt materials precisely. [ABSTRACT FROM AUTHOR]

For characterizing polymer modified binders, different state Departments of Transportation (DOTs) use a variety of laborious and empirical Performance Grade (PG) "Plus" test methods such as elastic recovery (ER) and tenacity. However, the effects of elastomeric and/or plastomeric polymers are not been accurately identified through these conventional tests. The main research goal of this study is to recommend alternative test method(s), which can be pursued by using a, commonly available, dynamic shear rheometer (DSR). To this end, efficacies of test methods such as multiple stress creep recovery (MSCR), elastic recovery using a DSR (ER-DSR), linear amplitude sweep (LAS), and binder yield energy test (BYET) were explored in this study. Also, a viscoelastic continuum damage (VECD) model was developed to characterize the fatigue cracking of asphalt binders. Two types of polymer modified binders from ten sources approved by the Arkansas Department of Transportation (ARDOT) and Texas Department of Transportation (TXDOT) were evaluated in the laboratory. Test results and analyses suggest that without risking the suppliers or users, either the ER-DSR or MSCR test can be a good replacement of the ER test method. A new ER-DSR binder grading system has been proposed. Among the selected fatigue tests, the BYET results were found to be highly related to fatigue damage. [ABSTRACT FROM AUTHOR]

In recent years, the use of reclaimed asphalt pavement (RAP) in pavement construction has become a common practice in the U.S. Addition of RAP with virgin asphalts alters the properties of base binders, resulting in a different in-service performance. Superpave tests are routinely used to characterise modified asphalt binders even though they are applicable for unmodified binders and cannot capture properties of modified asphalts. Recently, several researchers used Atomic Force Microscopy (AFM) techniques to characterise asphalt binders at an atomic level. In this study, binders from two field RAP samples collected from I-40 and I-30 in Arkansas were recovered using a Rotavapor (AASHTO T 319-08). Different amounts (25, 40, and 60%) of RAP binders were blended with a Performance Grade (PG 64-22) binder. Selected microscale (stiffness) and nanoscale (e.g. morphology and elastic modulus) properties of the blended binders were evaluated in the laboratory through test results obtained from selected Superpave tests and the PeakForce Quantitative Nanomechanical Mapping™ (PFQNM) mode of an AFM, respectively. As expected, the addition of RAP binder with the base binder increased the stiffness, thereby increasing the high PG temperature up to 85 °C for 60% RAP. The micro-structures as well as the nanomechanistic properties of the blended binders were found significantly different from those of the base binder; the elastic modulus of 60% RAP was over 70% higher than that of the base binder. The modulus was found to be correlated with the morphology. The nanoscale properties were in agreement with microscale properties of the tested binders. [ABSTRACT FROM AUTHOR]

The incorporation of supplementary cementitious material (SCM) in the concrete industry has become a common practice in recent years. Addition of SCMs (e.g., fly ash and silica fume) in concrete as a partial replacement of Ordinary Portland Cement (OPC) improves the mechanical properties of concrete. In Arkansas, there is an imminent deficiency of fly ash supply from local coal plant industries. Therefore, use of rice husk ash (RHA) as an alternative SCM has been investigated in this study. RHA is an agro-based by-product and treated as waste material. It has the potential to be used as SCM due to its high silica content. In this study, three different sizes of RHA (600 µm, 150 µm, and 44 µm) with two different percentages (10% and 20%) were used to modify concrete as a partial replacement of ASTM Type I OPC. A predominantly used local Class C fly ash (CFA) was also incorporated in this study for comparative analysis with RHA-modified concrete specimens. Laboratory tests were carried out to determine the properties of the fresh concrete mix as well as mechanical properties of hardened concrete. To observe the behavior of concrete under adverse weather conditions, tests pertinent to alkali-silica reaction (ASR) and effects of deicing chemicals were conducted in this study. Finally, One-way ANOVA method was used to determine any significant differences of means of tests data. Test results showed that both CFA-modified and finer RHA-modified concrete had better concrete properties than the coarse RHA-modified concrete. The 10% replacement dose was found to be the better of the two amounts evaluated in this study. Findings of this study are expected to give a better understanding of the use of RHA in producing concrete. [ABSTRACT FROM AUTHOR]

Asphalt binders are complex chemical composites of various organic molecules. They are often modified chemically to obtain some rheological and physical superiority over the unmodified neat binders. The chemical compositions they inherit from their crude origins determine the suitable modification methodologies, which eventually lead to their rheological changes. The changes in chemical compositions due to the modifications of selected asphalt binders with Polyphosphoric Acid (PPA) and Styrene Butadiene Styrene (SBS) were observed in this study. The percentage fractions of Saturates, Aromatics, Resins, and Asphaltenes (SARA) were measured for binders modified with different amounts of PPA and SBS. The Asphaltenes content was found to increase linearly with the addition of PPA and SBS, and so did their viscosity values. Unlike acidic binders (pH < 7.0), basic binders (pH > 7.0) demonstrated a distinctive decline of pH with PPA modifications. The Aromatics and Resins contents had a sharp change after a certain amount of PPA that demonstrated a demarcation point beyond which further addition of PPA would result in no desirable benefits. The demarcation points were different for two different (crude origin) binders. The addition of SBS did not contribute in changing the Asphaltenes content. Rather, SBS changed the Aromatics and Resins contents to yield the desired paving grade binder. [ABSTRACT FROM AUTHOR]

For the past several decades, researchers around the world have used nanoindentation techniques to characterize different materials for biological, medical, and polymer science applications. In recent years, nanoindentation techniques have been explored by some pavement professionals to characterize asphalt materials. This study used the atomic force microscope (AFM)-based PeakForce quantitative nanomechanical mapping (PFQNM) technique to evaluate nanoscopic properties of asphalt binders modified with four different types of industrial and agricultural waste materials, which included ground tire rubber (GTR), reclaimed asphalt pavement (RAP), reclaimed asphalt shingles (RAS), and rice husk ash (RHA). Three scan sizes (20×20, 10×10, and 5×5 µm) were used to map the properties of the aforementioned binder samples. Mechanistic properties such as adhesion, energy dissipation, deformation, and Derjaguin, Muller, and Toropov (DMT) moduli of modified binder samples were estimated at different morphological phases. The PFQNM analyses revealed distinct microstructures and grain distributions among tested additive-modified binder samples. The GTR-modified samples exhibited two distinct phases, namely, Catana and Peri phase, but the other additives provided another called the Perpetua phase. Mechanistic properties of the asphalt samples in the Catana and Peri phases were found to be similar but different for the Perpetua phase. The DMT moduli varied from 70 to 800 MPa, and the adhesion ranged from 8 to 12 nN. Among the four additives, RHA reduced the hardness of the asphalt binder unlike the others. The dissipation energy of the binder samples was found to be related to the adhesion, whereas the hardness depended on the depth of deformation. Demonstrations of quantitative mappings of the nanomechanistic properties of asphalt binders are expected to help build an understanding of the underlying sciences. [ABSTRACT FROM AUTHOR]

Due to an increasing rate of traffic volume and truckloads in recent years, asphalt binders are often modified with synthetic polymers to increase stiffness and sustain excessive heat during hot summer days. However, the cost of polymer-modified binders (PMBs) is significantly higher than unmodified binders. Nanoclays, on the other hand, are relatively inexpensive and naturally abundant, and have favorable intrinsic properties, such as nanoscopic size and high surface area. To this end, the research reported in this paper investigated moisture resistance properties of a commonly used Performance Grade (PG) 64-22 binder modified with different dosages of two selected nanoclays [(1) Cloisite 15 A, and (2) Cloisite 11B]. The state of dispersion of the nanoclay in the binder was examined using a scanning electron microscope and small-angle x-ray diffraction. The morphological analyses of scanning electron microscope scans and inter-gallery distances ( -spacing values) of small-angle x-ray diffraction data of the two selected nanoclays are effective in evaluating the state of ex- d foliated microstructure of nanoclays in asphalt binders. In particular, the small-angle x-ray diffraction data of two of the tested samples [(1) 4% of Cloisite 11B, and (2) 6% of Cloisite 11B] showed fully exfoliated microstructure. Moisture resistance of nanoclay-modified binders was evaluated through the surface free energy (SFE) technique. The adhesive energies and compatibility ratios (CRs) of nanoclay-modified binder and selected aggregate (four acidic and four basic) systems were also evaluated. The total SFE increases when the asphalt binder is modified by nanoclays. When the asphalt binder is modified with nanoclays, the wetting ability decreases. A 4% Cloisite 15 A and a 6% Cloisite 11B (by the weight of the binder) showed the highest adhesive energy in maintaining good wetting ability, with different acidic and basic aggregates. The work-of-adhesion values under dry and wet conditions of nanoclay-modified binders were highly dependent on the nature (acidic or basic) of aggregate. The CR, an indicator of moisture resistance or bond strength in wet conditions, of the nanoclay-modified asphalt binder decreased for all aggregates except for granite, which showed a slight increase of the CR values. Thus, unless modified with an antistripping agent or other additives, nanoclay modified binders are expected to have poorer moisture resistance than the base binder. While maintaining a dosage level of 4% (by weight) nanoclay, Cloisite 15 A, consisting of smaller particle size than Cloisite 11B, is more compatible with different aggregates than Cloisite 11B. At a lower dosage level (2% by weight), Cloisite 11B is more compatible than Cloisite 15 A. Furthermore, the nanoclay technology is expected to be a cost saving approach, which can reduce the cost per metric ton of asphalt binder from 22-33% compared to the polymer-modified binders. Findings of this paper are expected to assist pavement professionals in evaluating moisture resistance of nanoclay-modified asphalt binders through a fundamental science approach. [ABSTRACT FROM AUTHOR]

More than 300 million scrap tires are being generated every year in the United States and their proper disposal has been a major concern from environmental safety and economical point of views. Using these scrap tires as ground tire rubber (GTR) in asphalt mixes is becoming a common practice now a days. A number of research studies have been conducted to characterize the mechanistic properties of GTR modified asphalt. However, a very limited research has been conducted to evaluate their moisture susceptibility, particularly through fundamental science approaches. Moisture damage or stripping, the loss of strength and stiffness of asphalt mixes due to the existence of moisture, of asphalt pavements is one of the major concerns to the state and federal highway agencies for many years. The objective of this research was to evaluate moisture susceptibility of GTR modified asphalt binders through a surface science approach, in which surface free energy (SFF) components were estimated by following the sessile drop method. In the experimental plan, a commonly used performance grade (PG) binder (PG 64-22) modified with different dosages (0%, 10%, 15%, and 20%) of GTR were tested for static contact angles. Three different probe liquids, namely: water, formamide and ethylene glycol were used to determine contact angle with binder samples using an optical contact angle analyzer (OCA) device. The SFE of five different aggregates, namely: sandstone, gravel, granite, basalt and limestone, were used to evaluate the work of adhesion and compatibility ratio (CR). The SFE results of unmodified and modified binders showed that SFE increased due to the addition of GTR in binder. The work of adhesion of a binder aggregate system also increased with an increase of the GTR content when measured in the absence of water, but it decreased gradually in the presence of water. Granite and basalt showed lowest work of adhesion, whereas sandstone showed the highest work of adhesion. The CR data showed that granite and basalt were the most compatible aggregates with GTR modified binders. The CR value also had an increasing trend with an addition of higher GTR content, indicating an improved moisture resistance. The CR values of all asphalt aggregate systems were found to be greater than 1.5 with 20% GTR, indicating “good” moisture susceptibility. [ABSTRACT FROM AUTHOR]

The recent increased interest in 'fingerprinting' or identifying commonly used construction materials such as asphalt binders is expected to continue in years to come. To capture the basic fingerprint of asphalt binders, spectroscopy devices can be handy and useful. In particular, this study evaluated the effects of two warm-mix asphalt (WMA) additives, Sasobit and aspha-min, on the chemical compositions of a performance grade binder (PG 64-22). Spectroscopy techniques including Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR), and X-ray photo electron spectroscopy (XPS) were used in this study. Mass precipitated asphaltenes and maltenes and straight-run asphalt binder samples were analyzed using these techniques, and test results were compared with the rheological data. The effectiveness of an antistripping agent (ASA), AD-here HP Plus, on a WMA-modified binder was also evaluated. Furthermore, the effects of aging on chemical compositions of the ASA-modified binder were evaluated. Spectroscopy analysis data from this study were in agreement with high-temperature performance data of the tested binders. The findings of this study are expected to help in fingerprinting WMA mixes. [ABSTRACT FROM AUTHOR]

Effects of varying dosages of a water-bearing warm mix asphalt (WMA) additive, Advera®, on a performance grade (PG) binder, PG 64-22, were evaluated. The effectiveness of an amine-based liquid anti-stripping (AS) agent, AD-here® HP Plus, on the Advera®-modified binder was also studied. Furthermore, the effect of reduced oxidative ageing on Advera®-modified binder was investigated. The optimum dosage of Advera® was found to be 6% (by the mass of the binder), which did not alter the base binder's PG. A fairly small amount (0.5%) of the AS agent was found to be effective in increasing the fatigue and low temperature resistances of the Advera®-modified binder. A notable reduction in the high PG temperature was observed when the Advera®-modified binder was aged (short term) at 135°C, and this observation is in agreement with the test results of the Advera® mix, which showed excessive rutting and moisture susceptibility. Test data from a rotational viscometer showed no reduction in the viscosity and the production temperature of the Advera® mix thereof, indicating the need of an alternate laboratory test method to simulate the working mechanism of Advera®. The findings of this study are expected to enhance the inventory of rheological database and help in implementing WMA mixes in Oklahoma and elsewhere. [ABSTRACT FROM AUTHOR]

For designing pavements many state agencies, including those in Oklahoma, use the 1993 AASHTO Guide for Design of Pavement Structures, which is empirical in nature. However, the Mechanistic-Empirical Pavement Design Guide (MEPDG) is believed to predict pavement distresses in a more mechanistic approach, on the basis of material properties, local traffic, and climate conditions. Among material properties in the MEPDG, the dynamic modulus () of the asphalt mix is one of the key parameters necessary to achieve the highest level of design reliability. The present study was conducted to estimate values of two commonly used hot mix asphalt (HMA) mixes (S3 and S4) in Oklahoma. Different design reliability levels, on the basis of rheological properties of three performance grade (PG) binders, were considered. These asphalt binders were collected from three different sources in Oklahoma. Furthermore, sensitivities of major pavement distresses, namely, rutting, fatigue cracking, thermal cracking, and roughness to the design reliability, and asphalt binder type and source were evaluated by using the MEPDG software (Version 1.100). It was observed that rotational viscometer (RV) test data overestimate the values in the case of stiff binders. Conversely, dynamic shear rheometer (DSR) test data predict significantly lower values of asphalt mixes with all PG binders. Among distress factors, the rutting in HMA layers' was found to be highly sensitive to the design reliability and asphalt binder's PG grade. The asphalt binder source was also found to be somewhat sensitive to rutting. Other distresses were not significantly influenced by the design reliability, asphalt binder PG grade, and source. The findings of this study are expected to provide transportation professionals with a better understanding of material input parameters that influence values of asphalt mixes and pavement distresses, and assist in implementing the MEPDG for local conditions. [ABSTRACT FROM AUTHOR]

This study presents a testing protocol for evaluating the viscoelastic properties of selected performance grade (PG) binders using a dynamic mechanical analyzer (DMA). It also presents the effects of amine-based liquid anti-stripping additives on the binders' rheological properties. Out of total 183 samples tested, 51 samples for three PG binders (PG 64-22, PG 70-28, and PG 76-28) were tested to establish the DMA-based testing protocol. The remaining samples were tested to obtain rheological data of the PG 64-22 binder with different dosages of two anti-stripping (AS) additives. Test results of the DMA were validated by comparing with those obtained from a dynamic shear rheometer (DSR). Test results show that the DMA can be used as an alternative tool for examining the viscoelastic behavior of binders. It was observed that the rutting factor [G*/sin(δ)] of the binder decreased when the amount of AS additive was increased. The optimum dosage of either of these AS additives was found to be 0.50%. AS additives did not alter the mechanical workability and the linear viscoelastic limit of the binder. Also, a good correlation between the complex modulus of the PG 64-22 binder and the dynamic modulus of the corresponding mix was observed. [ABSTRACT FROM AUTHOR]

• Morphological and stiffness of asphalt binders with high reclaimed asphalts were evaluated. • An Atomic Force Microscope (AFM) was used to evaluate nanoscale properties. • Rejuvenators are very effective to reduce the hardness of stiff asphalt binders. • The effects of rejuvenator are seen in the surface images obtained from the AFM. • Modulus values of stiff binders reduce significantly when rejuvenators are used. A properly formulated rejuvenator is a possible remedy for asphalt pavements with a high percentage of Reclaimed Asphalt Pavement (RAP), which is traditionally too stiff to resist premature damage due to fatigue cracking. Rejuvenated asphalt binders with high RAP have traditionally been evaluated by micro- and macro-level test methods, which are transcendental in providing binders' molecular level properties that govern their performance properties. This paper presents the usefulness of an Atomic Force Microscope (AFM) and its nanoindentation technique to observe morphological and nanomechanical properties of rejuvenated asphalt binders with high RAP. A commercial rejuvenator is applied in a Performance Grade (PG) (PG 64-22) binder blended with different percentages (25%, 40%, and 60%, by the weight of the blended binder) of a bulk RAP. The rejuvenated asphalt binder blends were subjected to routine tests such as Penetration, Rotational Viscosity (RV), and Dynamic Shear Rheometer (DSR) as well as the AFM-based PeakForce Quantitative Nanomechanical Mapping (PFQNM™) analysis. As expected, the routine test results reveal that the rejuvenator reduces the stiffness of the RAP-modified binders. The effects of rejuvenator on the RAP-blended binders are evident in the morphological images and nano-level mechanistic data. Based on the AFM test results, it is observed that modulus values of RAP blended binders reduced significantly when the rejuvenator was used. The findings of this study will benefit the pavement professionals for assessing the effectiveness of rejuvenators in asphalt binders with high RAP contents. [ABSTRACT FROM AUTHOR]

Moisture and cracking damages are two of the most common asphalt pavement distresses in the United States. The use of stone matrix asphalt mixture has gained popularity due to its high durability, resistance to permanent deformation and cracking, and reduced noise pollution. Warm-mix additives and nanomaterials have also gained significant interest as promising asphalt binder additives. In order to achieve enhanced resistance to moisture and cracking in extremely wet regions, this study investigated the effects of three warm-mix additives, an anti-stripping agent, and one nanomaterial (graphene nanoplatelet) on the cracking and moisture resistance performance of stone matrix asphalt. Fourier transform infrared spectroscopy and sessile drop tests were used to evaluate the functional groups and moisture susceptibility of the modified asphalt binder blends, respectively. The indirect tensile asphalt cracking test and the modified Lottman tests were used to evaluate the mixtures' resistance to cracking and stripping damage. A cost-effectiveness analysis as well as a two-dimensional performance interaction diagram were employed based on the laboratory performance of the mixtures. Results indicated that the graphene nanoplatelet modification of the asphalt binder had the highest wettability potential, adhesion, and debonding properties, as well as moisture resistance potential compared to other additives. In terms of mixture cracking performance, both the graphene nanoplatelet and a chemical warm-mix asphalt significantly improved the mix cracking performance by 34.1 and 30.0 %, respectively, compared to the control mix. However, the graphene nanoplatelet modification had a tensile strength ratio of 0.76, which is below the acceptance threshold of 0.80 set by AASHTO T 283 for moisture damage resistance of asphalt mixture. Overall, all mixtures with warm-mix additives showed adequate cracking and stripping damage resistance performance and are expected to be cost-effective. • Graphene nanoplatelet modification improved surface free energy, wettability, adhesion, and bonding properties. • Warm-mix additives showed superior performance against moisture damage. • Chemical warm-mix additives showed optimum cost effectiveness. • Graphene nanoplatelet might not exhibit adequate performance against moisture in the field. [ABSTRACT FROM AUTHOR]

Introduction: Children with cerebral palsy (CP) in Bangladesh suffer immensely, with no means or hope for a decent life and a public system lacking basic facilities. This study aims to analyze the quality of life (QoL) and depression status of parents among children with CP, as well as the relationship between these factors and their demographic profile. Materials and Methods: This is a descriptive cross-sectional study in which data were collected from the Pediatric Department of Centre for the Rehabilitation of the Paralysed (CRP) in Savar. The participants included 150 children with CP between January 2018 and December 2020. Results: The mean age of the mothers (29.86±6.14) was between 25 and 29 years (32.7%). The most common type of CP was spastic CP among 100 mothers (66.7%). A significant relationship was observed between the mother's age during marriage and World Health Organization quality of life (WHOQoL-BREF), physical health (P<0.01), psychological health (P<0.01), and the age group of 31-35 years had the lowest scores (Mean±SD 62.00±5.16, 51±0.683) in both domains. A strong correlation (P<0.001) was observed between QoL, physical health (r=0.319), psychological (r=0.365), social (r=0.390) and environmental (r=0.388). From the box plot, QoL showed that spastic CP posed good QoL for mild depression while all other types had neither poor nor good QoL. Conclusion: A hidden issue in every parent is that CP children are the misfortune of their fate that increases their level of depression and consequently decreases their QoL. [ABSTRACT FROM AUTHOR]

Hepatitis E virus (HEV) is the major cause of epidemic and sporadic hepatitis globally. Outbreaks are associated with fecal contamination of drinking water, yet the environmental reservoir of HEV between epidemics remains unclear. In contrast to neighboring countries, where epidemics and sporadic disease co-occur, HEV-endemic communities in rural Bangladesh seldom report outbreaks; sporadic hepatitis E is reported from urban and rural areas of the country. Besides typical enteric risk factors, other routes for HEV infection and disease are unclear. We conducted monthly household surveillance of a southern Bangladeshi community of 23,500 people to find incident cases of acute hepatitis E over a 22 month period. An algorithm was used to capture 279 candidate cases, of which 46 were confirmed acute HEV infections. An exploratory case-control study was conducted to identify putative risk factors for disease. Nearly 70% of cases were over 15 years old. Female gender seemed protective (OR:0.34) against hepatitis E in this conservative setting, as was the use of sanitary latrines (OR:0.28). Socioeconomic status or animal exposures were not significant predictors of disease, although outdoor employment and recent urban travel were. Unexpectedly, recent contact with a “jaundiced” patient and a history of injection exposure in the 3 months prior to disease (OR:15.50) were significant. Susceptible individuals from “endemic” communities share similar enteric exposure risks to those commonly associated with tourists from non-endemic countries. This study also raises the novel possibility of parenteral and person-to-person transmission of HEV in non-epidemic, sporadic disease settings. [ABSTRACT FROM AUTHOR]

Hepatitis E virus (HEV) is the most common cause of acute viral hepatitis in the world. Most of South Asia is HEV endemic, with frequent seasonal epidemics of hepatitis E and continuous sporadic cases. This author group's epidemiologic work and clinical reports suggest that Bangladesh is HEV endemic, but there have been few population-based studies of this country's HEV burden. The authors calculated HEV infection rates, over an 18-month interval between 2003 and 2005, by following a randomly selected cohort of 1,134 subjects between the ages of 1 and 88 years, representative of rural communities in southern Bangladesh. Baseline prevalence of antibody to hepatitis E virus (anti-HEV) was 22.5%. Seroincidence was 60.3 per 1,000 person-years during the first 12 months and 72.4 per 1,000 person-years from >12 to 18 months (during the monsoon season), peaking by age 50 years and with low rates during childhood. Few of the seroconverting subjects reported hepatitis-like illness. Overall incidence was calculated to be 64 per 1,000 person-years, with 1,172 person-years followed. No significant associations were found between anti-HEV incidence and demographic or socioeconomic factors for which data were available. This is the first study to document annual HEV infection rates among “healthy” and very young to elderly subjects in a rural Bangladeshi population. [ABSTRACT FROM PUBLISHER]

The study aims to determine the level of Knowledge, Attitude, and Practice (KAP) related to COVID-19 preventive health habits and perception of fear towards COVID-19 in subjects living in Bangladesh. Design: Prospective, cross-sectional survey of (n = 2157) male and female subjects, 13–88 years of age, living in Bangladesh. Methods: Ethical approval and trial registration were obtained before the commencement of the study. Subjects who volunteered to participate and signed the informed consent were enrolled in the study and completed the structured questionnaire on KAP and Fear of COVID-19 scale (FCV-19S). Results: Twenty-eight percent (28.69%) of subjects reported one or more COVID-19 symptoms, and 21.4% of subjects reported one or more co-morbidities. Knowledge scores were slightly higher in males (8.75± 1.58) than females (8.66± 1.70). Knowledge was significantly correlated with age (p <.005), an education level (p <.001), attitude (p <.001), and urban location (p <.001). Knowledge scores showed an inverse correlation with fear scores (p <.001). Eighty-three percent (83.7%) of subjects with COVID-19 symptoms reported wearing a mask in public, and 75.4% of subjects reported staying away from crowded places. Subjects with one or more symptoms reported higher fear compared to subjects without (18.73± 4.6; 18.45± 5.1). Conclusion: Bangladeshis reported a high prevalence of self-isolation, positive preventive health behaviors related to COVID-19, and moderate to high fear levels. Higher knowledge and Practice were found in males, higher education levels, older age, and urban location. Fear of COVID-19 was more prevalent in female and elderly subjects. A positive attitude was reported for the majority of subjects, reflecting the belief that COVID-19 was controllable and containable. [ABSTRACT FROM AUTHOR]

Objective: We aimed to describe the causes, types, and consequences of lower limb amputation and the demographics of subjects with such amputation who attended a tertiary rehabilitation center in Bangladesh, Centre for the Rehabilitation of the Paralysed. Methods: Cross-sectional data were collected from subjects with lower limb amputation who attended a specialized rehabilitation center between January 2014 and August 2016. Telephone interviews were conducted using a structured questionnaire. Descriptive analysis, paired t-test, and Fisher's exact test were conducted as well as a regression analysis was performed. Results: A total of 332 respondents, aged 5 to 76 years (mean 37.5± SD 13.8), with lower limb amputation participated in the study. Of the respondents, the majority were male (87.7%) and lived in rural areas (64.8%). Road traffic accidents were the leading cause (58.7%) of amputation followed by peripheral vascular diseases (7.5%) and hit by sharp objects (7.2%). Age (odds ratio: 0.9) and driving as occupation (odds ratio: 7.3) were found to be statistically significant covariates for amputation from road traffic accidents. The mean duration between having an amputation and receiving the first prosthetic fitting was 6.4 years (±8.9). Among the study participants, 30.7% lost their jobs after amputation and their mean monthly income reduced significantly (p < 0.01) from US$119.9 (±421.5) to US$45.8 (±63.1). Conclusion: Majority of the lower limb amputations resulted from traumatic road traffic accidents. Younger males and drivers were found to be more prone to amputation from road traffic accidents. Lower limb amputation creates great health and economic disparity in the amputee's lives. Majority of the lower limb amputation cases in Bangladesh were attributable to road traffic accidents—a largely preventable cause. The mean time between amputation and prosthetic fitting was more than 6 years which implies lack of awareness and inaccessibility of prosthetic management. Policymakers, regulators, law enforcement, and traffic safety advocates should take urgent actions to prevent road traffic accidents and raise awareness about and improve availability of prosthetic rehabilitation in Bangladesh. [ABSTRACT FROM AUTHOR]

We present a hardware setup and a set of executable commands for spatiotemporal programming and interactive control of a swarm of self-propelled microscopic agents inside a microfluidic chip. In particular, local and global spatiotemporal light stimuli are used to direct the motion of ensembles of Euglena gracilis, a unicellular phototactic organism. We develop three levels of programming abstractions (stimulus space, swarm space, and system space) to create a scripting language for directing swarms. We then implement a multi-level proof-of-concept biotic game using these commands to demonstrate their utility. These device and programming concepts will enhance our capabilities for manipulating natural and synthetic swarms, with future applications for on-chip processing, diagnostics, education, and research on collective behaviors. [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]

This study explored the thermal cracking resistance of hot-mix asphalt (HMA) mixes containing recycled asphalt pavement (RAP). One RAP source was used to design two types of Superpave mixes, namely, Oklahoma S3 base and Oklahoma S4 surface course. Four mixes containing different percentages of RAP, namely, 25 and 40% RAP for S3 base courses and 0 and 10% RAP for S4 surface courses, were designed and tested. It was found that at lower temperatures, the mix containing a lower RAP content was stiffer, as indicated by higher creep compliance and indirect tensile strength values. At higher temperatures, however, the mix containing a higher content of RAP was also stiffer. Furthermore, the measured creep compliance values were compared with current predicted compliance values. The influence of RAP content on thermal cracking resistance was also evaluated through thermal stress analysis within the mechanistic framework. [ABSTRACT FROM AUTHOR]

This study explored the potential of using high reclaimed asphalt pavement (RAP) content with hot mix asphalt (HMA) in base and surface courses. A total of four Superpave mixes containing different percentages of RAP namely, 25% RAP and 40% RAP for S3 base courses and 0% RAP and 10% RAP for S4 surface courses were designed, constructed and tested. The mechanistic characteristics of mixes were evaluated by conducting creep compliance, dynamic modulus, Hamburg rut, and 4-point beam fatigue tests. The creep compliance results showed reduction in compliance of the mix due to increase in the RAP content. The dynamic modulus test results illustrated that the asphalt mix containing a higher amount of RAP has higher dynamic modulus values. The increase in RAP content reduced rutting susceptibility and improved moisture damage potential of both S3 and S4 mixes. [ABSTRACT FROM AUTHOR]

Background Epidemiologic research suggests that increased cancer risk due to chronic arsenic exposure persists for several decades even after the exposure has terminated. Observational studies suggest that antioxidants exert a protective effect on arsenical skin lesions and cancers among those chronically exposed to arsenic through drinking water. This study reports on the design, methods and baseline analyses from the Bangladesh Vitamin E and Selenium Trial ( BEST), a population-based chemoprevention study conducted among adults in Bangladesh with visible arsenic toxicity. Materials and methods Bangladesh Vitamin E and Selenium Trial is a 2×2 full factorial, double-blind, randomized controlled trial of 7000 adults having manifest arsenical skin lesions evaluating the efficacy of 6-year supplementation with alpha-tocopherol (100 mg daily) and L-selenomethionine (200 μg daily) for the prevention of nonmelanoma skin cancer. Results In cross-sectional analyses, we observed significant associations of skin lesion severity with male gender (female prevalence odds ratio ( POR) = 0·87; 95% CI = 0·79-0·96), older age (aged 36-45 years, POR = 1·27; 95% CI = 1·13-1·42; aged 46-55 years, POR = 1·44; 95% CI = 1·27-1·64 and aged 56-65 years, POR = 1·50; 95% CI = 1·26-1·78 compared with aged 25-35 years), hypertension ( POR = 1·29; 95% CI = 1·08-1·55), diabetes ( POR = 2·13; 95% CI = 1·32-3·46), asthma ( POR = 1·55; 95% CI = 1·03-2·32) and peptic ulcer disease ( POR = 1·20; 95% CI = 1·07-1·35). Conclusions We report novel associations between arsenical skin lesions with several common chronic diseases. With the rapidly increasing burden of preventable cancers in developing countries, efficient and feasible chemoprevention study designs and approaches, such as employed in BEST, may prove both timely and potentially beneficial in conceiving cancer chemoprevention trials in Bangladesh and beyond. [ABSTRACT FROM AUTHOR]

We introduced flocculant-disinfectant water treatment for 12 weeks in 103 households in Bangladesh to assess if drinking water would be chemically and microbiologically improved and the body burden of arsenic reduced. The median concentration of arsenic in tubewell water decreased by 88% after introduction of the flocculant-disinfectant from 136 μg/l at baseline to 16 (p < 0.001). The median concentration of total urinary arsenic decreased 42% from 385 μg/g creatinine at baseline to 225 μg/g creatinine after intervention (p < 0.001). Among 206 post-intervention drinking water samples that were reportedly treated on the date the sample was collected, 99 (48%) lacked residual free chlorine and 100 (49%) were contaminated with thermotolerant coliforms. The flocculant-disinfectant markedly reduced arsenic in drinking water, but treated drinking water was frequently contaminated with fecal organisms. The lesser reduction in urinary arsenic compared to water arsenic and the health consequences of this reduction require further research. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the nonlinear dynamic responses of a string are simulated using the Cellular Automata method based on the reflection rule. In the case of nonlinear systems, the velocity of wave propagation is not constant and depends on the amplitude. A new treatment of the dynamic time step is proposed for the Cellular Automata method considering the effect of the propagation velocity. As numerical examples, first, the dynamic responses of a string with linear characteristic are simulated using the Cellular Automata method. A typical resonance curve can be obtained. Second, the dynamic responses of a string with nonlinear characteristic are simulated using the proposed method. Some characteristic types of vibration can be obtained. It is concluded that the linear and nonlinear dynamic responses of a string may be obtained by simulation using the Cellular Automata method. [Copyright &y& Elsevier]