Laboratory and Field Evaluation of Modified Asphalt Binders and Mixes for Alaskan Pavements

In order to properly characterize modified asphalt binders and mixes for Alaskan pavements, this study evaluated properties of 13 asphalt binders typically used in Alaska from three different suppliers, and 10 hot mix asphalt (HMA) mixtures which were either produced in the lab or collected from existing paving projects in Alaska. Various binder and mixture engineering properties were determined, including true high binder grades, complex modulus (G*), and phase angle (δ) at high performance temperatures, multiple stress creep recovery rate and compliance, bending beam rheometer stiffness and m-value, Glover-Rowe parameter, ΔT, rheological index, and crossover frequency for binders, and rut depth, critical strain energy release rate (Jc), Indirect tensile (IDT) creep stiffness and strength for mixtures. Binder cracking temperatures were determined using asphalt binder cracking device. Mixture cracking temperatures were determined with IDT creep compliance and strength data. It was found that rutting and cracking resistances of the mixtures with highly modified binders were better than the mixture with unmodified asphalt binder (PG 52-28). Future recommendations for highly modified asphalt binders applications and research were provided based on laboratory testing results and field survey evaluation

Toughness, Tenacity and Maximum Initial Strength of Rubber Modified Asphalt Binders

The toughness and tenacity test method, which was developed in the 1980s, is popular for evaluating a polymermodified binder. Several states like Nevada require performing this test to evaluate non-modified binder samples, as well as other types of modified binders. In this regard, a toughness and tenacity test was performed on rubber-modified samples produced from virgin binder PG58-28, PG64-16 and AC-20. In order to take the rubber size, type and content into account, two rubber sizes, mesh #20 and #40, two rubber types, ambient and cryogenic, and three rubber contents, 10%, 15%, and 20% were produced and tested. The results then were compared with polymer-modified and terminally blended rubber-modified samples. The results show improvement in the amount of initial maximum strength, and a decline in the magnitude of elongation, toughness and tenacity for the rubber-modified binder, compared to other types of binders

Physicomechanical assessments and heavy metals’ leaching potential of modified asphalt binders incorporating crumb rubber and tin slag powders

Industrial solid waste has been widely used as an alternative additive for bituminous material modification. This study aims to evaluate the basic properties and quantify the leaching potential of modified asphalt binders incorporating crumb rubber powder (CRP) from waste tires and tin slag (TS) for a local smelting company. Three percentages of CRP and TS, at 5, 10, and 15%, were considered. The conventional asphalt binder (PEN 60/70), CRP, and TS-based modified asphalt binders were analyzed for toxicity, softening point, penetration value, elastic recovery, torsional recovery (TR), and coatability index. The findings indicated that the addition of the waste materials led to no significant heavy metal content in the asphalt binder mix. Moreover, the basic and physical properties of the asphalt binders were also improved by 5, 10, and 15% of the waste, respectively. However, TS waste exhibited limited effects on all the parameters and had a 5% optimum dosage. The modified binders’ results showed that the CRP modified asphalt binders had fewer heavy metals and responded more to elastic recovery and coatability

Asphalt Binder Laboratory Short-Term Aging

The Rolling Thin Film Oven (RTFO) is widely used to simulate asphalt binder short-term aging. However, there is a general interest to improve the current short-term aging protocol especially for reducing the aging time. Besides, there are some doubts about the capability of RTFO in the simulation of aging of highly polymer modified asphalt binders which is mainly due to improper dispersion of such binders in the bottles during rotating and creeping of highly viscous binder out of the bottles during rotation. This work addresses the effect of time, temperature, airflow rate, and weight of asphalt binder on the laboratory short-term aging of asphalt binders and proposes an alternative protocol that can reduce the aging time and resolve some of the current short-term aging protocol shortcomings. In the first part of this study, two asphalt binders, from different sources, were examined in RTFO at different combinations of the above-mentioned test parameters. The high-end continuous performance grading temperature (estimated by dynamic shear rheometer), and carbonyl index (estimated by Fourier transform infrared spectroscopy) were considered as the two responses for quantification and qualification of laboratory aging. The statistical analysis showed that the first order terms of time, temperature, and weight as well as their interactive terms were statistically significant. However, the effect of airflow rate, within the studied range, was insignificant. Based on the findings of the first part of study, an alternative protocol was proposed for the study of short-term aging in a RTFO. One unmodified and three highly modified binders were aged in a RTFO under the current and proposed aging conditions for comparative purposes. According to the obtained rheological (high- and low-end continuous performance grading temperature and viscosity) properties as well as the chemical characteristics (carbonyl index, saturate-aromatic-resin-asphaltene fractions, and oxygen content), it was shown that the proposed laboratory short-term aging protocol not only can reduce the aging time of the conventional protocol, but also that it is applicable to both neat and polymer-modified modern asphalt binders

THE PERFORMANCE AND MODIFICATION OF RECYCLED ELECTRONIC WASTE PLASTICS FOR THE IMPROVEMENT OF ASPHALT PAVEMENT MATERIALS

Bulk electric waste plastics were recycled and reduced in size into plastic chips before pulverization or cryogenic grinding into powders. Two major types of electronic waste plastics were used in this investigation: acrylonitrile butadiene styrene (ABS) and high impact polystyrene (HIPS). This research investigation utilized two approaches for incorporating electronic waste plastics into asphalt pavement materials. The first approach was blending and integrating recycled and processed electronic waste powders directly into asphalt mixtures and binders; and the second approach was to chemically treat recycled and processed electronic waste powders with hydro-peroxide before blending into asphalt mixtures and binders. The chemical treatment of electronic waste (e-waste) powders was intended to strengthen molecular bonding between e-waste plastics and asphalt binders for improved low and high temperature performance. Superpave asphalt binder and mixture testing techniques were conducted to determine the rheological and mechanical performance of the e-waste modified asphalt binders and mixtures. This investigation included a limited emissions-performance assessment to compare electronic waste modified asphalt pavement mixture emissions using SimaPro and performance using MEPDG software. Carbon dioxide emissions for e-waste modified pavement mixtures were compared with conventional asphalt pavement mixtures using SimaPro. MEPDG analysis was used to determine rutting potential between the various e-waste modified pavement mixtures and the control asphalt mixture. The results from this investigation showed the following: treating the electronic waste plastics delayed the onset of tertiary flow for electronic waste mixtures, electronic waste mixtures showed some improvement in dynamic modulus results at low temperatures versus the control mixture, and tensile strength ratio values for treated e-waste asphalt mixtures were improved versus the control mixture

The Laboratory Evaluation of Bio Oil Derived From Waste Resources as Extender for Asphalt Binder

A shortage of petroleum asphalt is creating opportunities for engineers to utilize alternative pavement materials. Three types of bio oils, original bio oil (OB), dewatered bio oil (DWB) and polymer-modified bio oil (PMB) were used to modify and partially replace petroleum asphalt in this research. The research investigated the procedure of producing bio oil, the rheological properties of asphalt binders modified and partially replaced by bio oil, and the mechanical performances of asphalt mixtures modified by bio oil. The analysis of variance (ANOVA) is conducted on the test results for the significance analysis. The main finding of the study includes: 1) the virgin bioasphalt is softer than the traditional asphalt binder PG 58-28 but stiffer after RTFO aging because bio oil ages much faster than the traditional asphalt binder during mixing and compaction; 2) the binder test showed that the addition of bio oil is expected to improve the rutting performance while reduce the fatigue and low temperature performance; 3) both the mass loss and the oxidation are important reasons for the bio oil aging during RTFO test; the mixture test showed that 1) most of the bio oil modified asphalt mixture had slightly higher rutting depth than the control asphalt mixture, but the difference is not statistically significant; 2) the dynamic modulus of some of the bio oil modified asphalt mixture were slightly lower than the control asphalt mixture, the E* modulus is also not statistically significant; 3) most of the bio oil modified asphalt mixture had higher fatigue lives than the control asphalt mixture; 4) the inconsistence of binder test results and mixture test results may be attributed to that the aging during the mixing and compaction was not as high as that in the RTFO aging simulation. 5) the implementation of Michigan wood bioasphalt is anticipated to reduce the emission but bring irritation on eyes and skins during the mixing and compaction

Characterization of the performance of aluminum oxide nanoparticles modified asphalt binder

This study investigates the physical and rheological properties of asphalt binders modified by nano aluminum oxide (AL2O3). Several conventional tests were conducted, including penetration, softening point and ductility, rotational viscosity and dynamic shear rheometer (DSR). Based on the results of the tests, it was found that the hardness of modified asphalt binders increased with the addition of nano AL2O3 up to 5%. As a result of the increased hardness, the softening point of modified asphalt improved compared with base asphalt binders. The rheological property of modified binders was enhanced at low and high temperatures. The results of a DSR test revealed that the G* were improved, whereas the δ decreased slightly. The addition of a different percentage of AL2O3 to base binder had a remarkable influence on resistance to permanent deformation (high temperature rutting and low temperature fatigue). Results recognize 5 wt.% as the optimum content of the modifier. Therefore, nano AL2O3 can be considered as a proper alternative additive to modify the properties of asphalt cement

Rheological performance evaluation of asphalt modified with bio-based polymers

Fuel-based polymers, used as modifiers and additives in asphalt cement binders, improve the rheological performance of the base asphalt binders, therefore increase the resistance to pavement distresses. However, demand for polymers that are biodegradable, environmentally friendly, and cost effective is increasing. Soybean oil used as an alternative in place of soft and rubbery elastomers polybutadiene derived from crude oil was synthesized to bio-based polymers via chemical synthesis methods reversible addition-fragmentation chain transfer (RAFT) and atom transfer radical polymerization (ATRP). In this study, bio-based polymers (PS-PAESO and PS-PAESO-Cl) with different styrene parameters were blended at a dosage of 3% by weight to a base asphalt binder by the solvent blending approach and three different shear blending methods. The objective of this study was to characterize the rheological properties of bio-based polymer modified asphalt blends by conducting dynamic shear rheometer (DSR), rolling thin film oven (RTFO), pressurized aging vessel (PAV), and bending beam rheometer (BBR) based on the Superpave performance graded asphalt binder specifications. The complex modulus (G*), phase angle (δ), mass losses, creep stiffness were determined to evaluate the rheological properties of the modified blends. Statistical analysis was conducted to evaluate the related factors that may influence the test results and to develop statistical modeling for predicting the bio-based polymers with appropriate styrene parameters that would optimize the rheological performance of the modified blends. Results from high temperature performance tests show that the addition of bio-based polymer (PS-PAESO and PS-PAESO-PS) used in this study increase the critical high temperature of the base binder that indicate an improvement on the resistance of rutting at high temperature. The similar results are observed from the master curves and the black diagrams which both exhibit stiffer behavior of the base asphalt at higher temperatures after modification, which indicates a rubber-elastic network establishment within the blends. Whereas, these bio-based polymers do not substantially improve the resistance to low temperature thermal cracking based on the critical low temperature results. Another finding is the use of bio-based polymers generally widened the continuous performance grade range of the base asphalt binder, which indicates that the bio-based polymers reduce the temperature susceptibility of the base asphalt binder. Furthermore, the statistical analysis on laboratory test results show no statistically significant difference between the three shear blending methods used in this study and no statistically significant difference between the polymer synthesis reaction durations. However, further statistical analysis by using block design on the shear blending methods and the polymer reaction durations shows there is statistically significant difference between the short and long reaction durations but no statistically significant difference between the shear blending methods. The finalized prediction models based on the response surface modeling present the same predicated styrene parameters in polymer to the test result analysis, which indicates that bio-based polymer with styrene parameters as lower molecular weight and lower styrene content are recommended for achieving higher critical high temperatures