Search

The mounting impacts of climate change on infrastructure demand proactive adaptation strategies to ensure long-term resilience. This study investigates the effects of predicted future global warming on asphalt binder performance grade (PG) selection in the United States using a time series method. Leveraging Long-Term Pavement Performance (LTPP) data and Superpave protocol model, the research forecasts temperature changes for the period up to 2060 and calculates the corresponding PG values for different states. The results reveal significant temperature increases across the majority of states, necessitating adjustments in PG selection to accommodate changing climate conditions. The findings indicate significant increases in average 7-day maximum temperatures across the United States by 2060, with 38 out of 50 states likely to experience rising trends. Oregon, Utah, and Idaho are anticipated to face the largest temperature increases. Concurrently, the low air temperature has risen in 33 states, with notable increases in Maine, North Carolina, and Virginia. The widening gap predicted between required high and low PG poses challenges, as some necessary binders cannot be produced or substituted with other grades. The study highlights the challenge of meeting future PG requirements with available binders, emphasizing the need to consider energy consumption and CO2 emissions when using modifiers to achieve the desired PG properties. [ABSTRACT FROM AUTHOR]

The long-term aging of bitumens and its effect on low-temperature performance is a detrimental phenomenon. In order to investigate the effects of the aging phenomenon on the low-temperature performance of bitumens, it is very important to accurately simulate the behavior of bitumens in repeated aging cycles and to investigate related viscoelastic, chemical, and microstructural changes. In this research, three types of bitumen with penetration grades of 40/50 , 60/70 , and 85/100 were subjected to one to three cycles of pressure aging vessel (PAV) aging. Comprehensive data on the bitumen's behavior were obtained by conducting bending beam rheometer, Fourier transform infrared spectroscopy, and atomic force microscopy tests. Using the results of the conducted tests, an attempt was made to find precise relationships between different indicators of bitumen aging in terms of chemistry and viscoelasticity. The results revealed a linear correlation between the aging index and the ΔTc and dissipated energy ratio (DER) values, as well as the aging index and the vertical shift factor of the stiffness-time curve. The fitting coefficients of these linear relationships were R2=0.8 and above, indicating a strong linear relationship between these parameters. Furthermore, the viscoelastic indices DER and the derivation of creep compliance (J′) exhibited a fairly good linear relationship. [ABSTRACT FROM AUTHOR]

The volume filling ratio and type of filler significantly influence the rheological and mechanical properties of bituminous composites. This effect can stem from either chemical interactions between the filler and bitumen or simple physical phenomena. Understanding the influence of filler on asphalt mastic performance is crucial for comprehending the behavior of asphalt mixtures. This study employs both experimental and numerical modeling approaches. The rheological properties of asphalt mastic samples made with pure bitumen and limestone filler at various filler contents were determined using frequency sweep tests. The experimental results indicated that increasing the volume filling ratio in asphalt mastic leads to non-linear changes in the values of the complex shear modulus (G*) and phase angle (δ), known as the stiffening phenomenon. Considering the concept of transitional zone between filler and bitumen, a parameter called Effective Volume Filling Ratio (EVFR) was introduced to explain this phenomenon. To predict the viscoelastic behavior of asphalt mastic based on the mechanical properties of bitumen and filler, finite element method (FEM) simulations were utilized. The accuracy of these models was evaluated by calculating the relative difference between the experimental complex shear modulus (G*) and the complex shear modulus predicted by the model. Results of this evaluation indicated that incorporating the EVFR into the numerical model can significantly enhance the accuracy of the predictions for viscoelastic behavior of asphalt mastic samples. [ABSTRACT FROM AUTHOR]

Predicting faulting failure is useful in the optimal concrete pavement design. In this study, artificial neural networks and the random forest method have been used to predict the amount of this failure. The general prediction model was created by inserting 32 available input variables into artificial neural networks. An integer two objectives optimisation problem was designed to select features that significantly affect the faulting. After applying this method, 19 important variables were identified and used to develop two simplified models based on artificial neural networks and the random forest method. It is shown that the simplified model developed by artificial neural networks is the best model to accurately predict the faulting considering the number of input variables. The cumulative number of days when the precipitation is more than 12.7 mm, the elastic modulus of concrete slab, the number of days passed since the pavement was built, base thickness, the cumulative ESALs in the traffic lane, and the annual average number of days when the temperature is more than 32°C were identified as the most important parameters in predicting faulting using the random forest method. A Sensitivity analysis has been then performed on these variables and optimal values were determined. [ABSTRACT FROM AUTHOR]

Acid sludge is an environmental pollutant that is produced daily in large amounts in used engine oil refineries. Recycling this waste is the primary goal of this paper. This study used 'washing with water' and 'neutralization with quicklime' methods to prepare acid sludge for use in bituminous materials as huge potential disposal. The neutralised sludge by the 'washing with water' method was added to bitumen in the wet blending process at 10, 20, and 30 wt%. This product is brittle without proper adhesion and cohesion and cannot meet the standard limits as an acceptable binder. It performs like long-term aged bitumen, reducing penetration and ductility and increasing the aging potential and viscosity. In another method, the neutralised sludge by adding quicklime was added to the asphalt mixture to replace fine aggregates in 50, 75, and 100 wt%. Using this product decreases the aging potential and moisture susceptibility up to 36.4, and increases rutting resistance up to 34.7%, indirect tensile strength up to 17.3%, and resilient modulus up to 17.3%. Despite the presence of large amounts of heavy metals in acid sludge, using this product in asphalt mixtures is an economical and completely hygienic solution for disposing of acid sludge. [ABSTRACT FROM AUTHOR]

The effect of different volume filling ratios (VFR) of filler on the flexural creep stiffness and complex shear modulus of bituminous composites can be identified using BBR and DSR test setups. This research compares the findings of extensive experimental studies with the biphasic heterogeneous micromechanical finite element (FE) models to introduce the Effective Volume Filling Ratio (EVFR). The different VFRs from 10 to 40% were selected to fabricate asphalt mastic samples. The effects of loading regime, temperature, loading frequency, and VFR on the mechanical behavior of asphalt mastic were investigated, and practical formulations were proposed to determine the EVFR for both shear and bending stiffening. It was found that for VFR ≤ 20%, the differences between the FE and test results are negligible under both loading schemes. However, higher VFRs cause a further increase in the stiffening and percolation effects which produce more differences between the experimental and FE results. [ABSTRACT FROM AUTHOR]