•Incorporation of fly ash into asphalt provided the crack-arresting effect at low temperatures.•The use of fly ash improved the rheological response of the asphalt binders.•The use of fly ash enabled ...binder grade increase to the levels achieved with polymer modification.•The improved rutting resistance of hot-mix asphalt with 5–60% of fly ash is expected.
Fly ash has been effectively used in concrete; however, there are limited applications in which fly ash has been used in asphalt pavements. The reported research demonstrates that the use of fly ash in bitumen materials is an attractive option because it improves performance and reduces costs and environmental impacts. Microstructural investigation demonstrated that the crack-arresting was induced by the fly ash particles evenly distributed within bitumen matrix.
To assess the effect of fly ash on the rheological performance of asphalt cement, a dynamic shear rheometer was used to measure the binder’s resistance to shear deformation in the linear viscoelastic region. The rutting factor, G*/sin(δ) and dynamic viscosity, η′, were determined for different types of bitumen at different temperatures, with 5%, 15%, 30% and 60% of binder replacement by weight of fly ash class C and F. The addition of fly ash improved the rutting factor and reached a higher performance grade of the binders. The viscosity for both bitumen types increased at 124°C degrees, but for the most of the compositions it remained within the range for mixing and placement of asphalt concrete.
Using sustainable, renewable substances that can be locally-sourced instead of petroleum-based asphalt binders would be better for our environment. Replacing a small portion (maximum of 6%) of ...asphalt binder with three different types of lignin was investigated to determine its effects on aged and unaged asphalt binder and mix. Commercially available Kraft lignin, lignin precipitated from black liquor in the laboratory, lignin produced from rice hulls in the laboratory using a deep eutectic solvent, and a standard asphalt binder (control) were evaluated. Lignin improved the high temperature performance grade. All lignin-modified binders showed higher strain tolerance than unmodified binders in strain sweep tests. Lignin precipitated from black liquor and lignin produced from rice hulls improved the long-term aging index. Rutting, cracking, and moisture damage susceptibility tests were performed on an asphalt mix prepared with 6% lignin precipitated from black liquor asphalt binder. Improved rutting resistance was observed from the lignin-modified asphalt mix, without sacrificing moisture-induced damage resistance. Better cracking resistance with respect to increased flexibility index was observed according to the semi-circular bend test. Replacing petroleum-based binder with up to 6% of lignin precipitated from black liquor is practicable for hot mix asphalt, and may be feasible in the lower temperature warm mix asphalt process.
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•6% of petroleum asphalt binder can be replaced with lignin from agricultural waste.•Replacement with lignin can improve high T performance grade & long term aging.•In asphalt pavement mix, lignin replacement improved flexibility.•Better rutting resistance with lignin suggests its feasibility for asphalt use.
AbstractIn this study, a handheld Fourier transform-infrared spectrometer (FT-IRS) is used as the primary equipment to determine the reclaimed asphalt pavement (RAP) content in a mix by quantifying ...the extent of aging of a fresh mix. Binders of different performance grades and sources were used for laboratory aging and were analyzed to comprehend and compare different aging processes in terms of a carbonyl index (ICO). The results show that the ICO of the RAP from 10 different sources varies from 0.0275 to 0.0607. Standard PAV aging produces ICO of only 0.0239, which indicates the significantly higher oxidation reaction in a service life than the laboratory aging. Attenuated total reflectance (ATR)-FTIRS data collection requires a small amount of the binder, which can be extracted in the field in 15 min by following the quick extraction method developed in this study. A spectral analysis of an unaged binder and RAP can predict the ICO in the fresh mix. The predicted and the measure ICO values were found to be in good agreement in two different plant mixes. So, the handheld FT-IRS has the potential to be used as a quality control tool in the field by precisely and quickly detecting the presence of aged RAP in the mix.
AbstractIn this study, the role of the dewetting mechanism in moisture damage of asphalt pavements was investigated. Three main asphalts, and mainly two antistrip additives, were utilized. A unique ...dewetting-based moisture damage test procedure was developed consisting of a moisture conditioning procedure and quantitative analysis of the dewetting with the use of a microscope and an application software. The dewetting analysis procedure includes measurements of the total dewetted area and number of dewetted holes. It was observed that the dewetting phenomenon occurs primarily under a trapped air bubble in the asphalt film submerged in water. Polymer (styrene butadiene styrene) in PG 76-22M (modified) asphalt did aid in reducing dewetting. At high pH, 10, the Adhere LOF 6500 additive increased dewetting for all three asphalts. The critical film thickness for all three asphalts was estimated experimentally and found to be 300 μm. The findings of this study on understanding the role of dewetting on moisture damage in asphalt pavements will assist in the implementation of a unique dewetting-based moisture damage test procedure and analysis.
AbstractTwo most common distresses found in chip seals are raveling and bleeding. Although raveling is a process that continues throughout the whole service life of chip seals, current performance ...tests available for chip seals focus mainly on early raveling and bond maturation. In this study, chip seals binders from the field were extracted and recovered for two consecutive years. Rheological properties of original, field-aged, and laboratory-aged binders were compared. Results showed that pressurized aging vessel (PAV-) aging simulates 3 to 4 years of field-aging for hot asphalt and less than 3 years for emulsion. Strain tolerance, shear stress at failure, oxidative aging index, and yield energy of the binder were correlated with long term field performance (raveling). Shear stress at failure of field-aged binders showed strong correlation with long-term field performance, exhibiting an R2 value of 0.95. However, yield energy (a product of strain tolerance and shear stress at failure) of original binder, which showed an R2 value of 0.83 with long-term field distress rating (raveling), was recommended as performance parameter for chip seals binder.
Warm-mix asphalt (WMA), which reduces the production temperatures (mixing and compaction) while maintaining the advantages of hot-mix asphalt (HMA), is becoming an attractive paving material. In this ...study, rheological properties of two commonly used performance grade (PG) binders (PG 64-22 and PG 70-28) were evaluated, with and without Sasobit and Aspha-Min additives. For PG 64-22,2%, 3%, and 4% Sasobit additive reduced the mixing temperature of the pure binder from 163°C to 147°C (i.e., by 16°C). In case of the PG 70-28, the reductions are 10°C, 12°C and 13°C, respectively, for 2%, 3%, and 4% Sasobit additive. No significant decrease in mixing temperature by the Aspha-Min additive was observed in using the rotational viscometer. Evaluation of the binders on the basis of G*/sin(δ) demonstrates no negative effect on high-temperature grading due to high-temperature viscosity reduction. With the addition of 4% Sasobit additive, the high-temperature binder grading of PG 64 (actually PG 65) increases to PG 69, while 4% Sasobit additive improves the PG 70 (actually PG 75) to PG 80. No significant changes in grading were observed with the addition of the Aspha-Min additive. In fact, reduction in binder viscosity and improvement in binder grading without increasing the viscosity indicate two-way reductions (both direct and indirect) in production temperatures by the Sasobit additive. Finally, the Sasobit additive is found to decrease the asphalt pavement analyzer rut depths significantly, and these rut depths correlate well with the rutting factor G*/sin(δ). It was also observed that rutting potential decreases with decreasing mixing and compaction temperatures. Comparatively, a smaller reduction in rut depths was observed by adding the Aspha-Min additive.
The influence of natural wax in asphalt binders and hot-mix asphalt has been studied for decades, with consideration of both negative and positive effects. Recent advances in warm-mix asphalt (WMA) ...have spurred interest in the use of commercial waxes such as Sasobit and Asphaltan B as additives in asphalt binders to achieve certain positive effects. Despite a number of previous studies, the effect of Sasobit on wettability and adhesion between asphalt binders and aggregates is not fully understood. Likewise, the effect of water vapor released from Aspha-Min, another WMA additive, at production temperatures is not adequately understood, although such water may negatively influence the behavior of WMA. In the present study, the effect of Sasobit and Aspha-Min on wettability and adhesion was investigated using the surface free energy (SFE) method. Dynamic advancing-wetting contact angles were measured for wettability (coating) and dewetting-receding contact angles were measured to evaluate adhesion. It was observed that Sasobit increases the wettability of asphalt binders over aggregates, as indicated by the change in the spreading coefficient. Conversely, a general trend is that Sasobit reduces the adhesion (free energy of adhesion) between asphalt binders and aggregates. In this study, moisture susceptibility is defined as the amount of spontaneously released free energy due to the breaking of the binder-aggregate bond with water. For PG 64-22, a small or no reduction in moisture susceptibility was observed; for PG 70-28, an increase in moisture susceptibility was observed. In case of the Aspha-Min, the overall SFE results are insignificant.
Styrene-butadiene-styrene (SBS) modified PG 64-22 and PG 76-22 binders are studied to investigate the degradation of polymer because of aging applied by: rolling thin film oven (RTFO), pressure aging ...vessel (PAV), and ultraviolet (UV). Upon observing the temperature increment of unmodified binder during high shear mixing, a polymer mixing procedure has been established. SBS (2%, 4%, and 6%), polyphosphoric acid (PPA) (0.5%, 2%, and 3.5%), and PPA (2%)-SBS (0.5%, 2%, and 3.5%) are mixed with PG 64-22 binder. Sentmanat extensional rheometer, based on dynamic shear rheometer, is used to investigate the extensional deformation characteristics in which SBS modified binders exhibit both first peak elongation force, F1, and second peak elongation force, F2, whereas, unmodified binders and PPA modified binders exhibit no F2. SBS is the most effective in increasing F2 with an increasing rate of 1.16N/% of SBS polymer. At 12°C and 16°C, F2 of RTFO aged SBS modified binder reduces, which indicates the polymer is degrading. In the case of PAV aged SBS modified binder, no F2 is found at 12°C and 16°C. With the increment of temperature, the PAV aged sample shows F2, but the value is less than the F2 of the original and RTFO aged binder of similar stiffness (F1). A normalized parameter, F2/F1, also shows that RTFO and PAV aging degrade SBS. Evaluation of UV aged SBS modified binder shows no F2 at any temperature while oven aged binder shows F2 value at similar aging temperature, duration, and thickness, indicating SBS completely degrades because of UV aging.
The concern over ensuing freshwater scarcity has forced the developing countries to delve for alternative water resources. In this study, we examined the potential of stagnant surface water bodies ...(SSWBs) as alternative freshwater resources in the densely populated Chittagong metropolitan area (CMPA) of Bangladesh--where there is an acute shortage of urban freshwater supply. Water samples were collected at 1-month intervals for a period of 1 year from 12 stations distributed over the whole metropolis. Samples were analyzed for pH, water temperature (WTemp), turbidity, electrical conductivity (EC), total dissolved solids, total solids, total hardness, dissolved oxygen (DO), chloride, orthophosphates, ammonia, total coliforms (TC), and trace metal (Cd, Cr, Cu, Pb, As, and Fe) concentrations. Based on these parameters, different types of water quality indices (WQIs) were deduced. WQIs showed most of CMPA-SSWBs as good or medium quality water bodies, while none were categorized as bad. Moreover, it was observed that the minimal water quality index (WQIm), computed using five parameters: WTemp, pH, DO, EC, and turbidity, gave a reliable estimate of water quality. The WQIm gave similar results in 72% of the cases compared with other WQIs that were based on larger set of parameters. Based on our finding, we suggest the wider use WQIm in developing countries for assessing health of SSWBs, as it will minimize the analytical cost to overcome the budget constraints involved in this kind of evaluations. It was observed that except turbidity and TC content, all other quality parameters fluctuated within the limit of the World Health Organization suggested standards for drinking water. From our findings, we concluded that if the turbidity and TC content of water from SSWBs in CMPA are taken care of, they will become good candidates as alternative water resources all round the year.
Viscosity determination of thixotropic emulsions with good repeatability has always been a major challenge. Currently, Saybolt Furol viscometer (SFV) is used to determine the viscosity of the ...emulsion, but the main drawback of the SFV is that it cannot simulate the behaviour of emulsion under different shear rate. Rotational viscometer (RV) can measure viscosity at different shear rates. Due to the thixotropic behaviour of the emulsions, getting repeatable results by following the hot binder specification is a problematic task. In this study, a new multiple shear step approach is used to determine the viscosity of the emulsified asphalt using RV. Three low viscous (SS-1, SS-1H and SS-1L) and two high viscous (CRS-2 and CRS-2P) emulsions were used in this study. Shear stress is gradually stepped up to different levels after certain time interval to determine the viscosity. In this manner, emulsion undergoes a known shear state and each reading is preceded by a certain repeatable shear history. It was observed that with the progression of time and simultaneous increase in shear rate, the viscosity results are much more stable and repeatable with less than 5% coefficient of variance. The final specifications proposed are 220-730 and 5-90 cP at 50 rpm and 30 °C for high and low viscous emulsions, respectively, which are based on 98% probability. Viscosity measured by this approach also showed strong correlation with water content (R
2
> 0.94). The correlation between viscosity and water content is even stronger after dilution. With different dilution water content, viscosity of CRS-2 and CRS-2P exhibited R
2
values of 0.97 and 0.98, respectively.
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