Zahid Hossain

Evaluation for Warm-Mix Additive-Modified Asphalt Binders Using Spectroscopy Techniques

AbstractThe 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...

Effects of an Amine Anti-Stripping Agent on Moisture Susceptibility of Sasobit and Aspha-Min Mixes by Surface Free Energy Analysis

Warm mix asphalt (WMA) is a fairly recent technology developed primarily to address issues such as high vapor emissions and high energy costs associated with the traditional hot mix asphalt (HMA) paving. Although the WMA is becoming a popular paving technology through field and laboratory evaluations, many researchers and transportation personnel are concerned about its moisture resistance. The present study analyzes the free energy of adhesion or wetting ability between eight different aggregates and an asphalt binder modified with varying dosages of two warm mix additives, namely Sasobit and Aspha-Min. Sasobit showed a maximum of 20.9 % and an average of 12.8 % increase in the free energy of adhesion in dry condition. The adhesion in the presence of moisture, referred to as free energy of reduction, was also evaluated to understand the moisture susceptibility of the WMA. The lower the free energy of reduction, the lower the asphalt binder’s tendency to de-bond from aggregates in the presence of moisture. A maximum of 20.5 % and an average of 13.2 % decrease in the free energy of reduction were observed for asphalt binder with 3 % Sasobit. However, Aspha-Min did not exhibit any significant effect on any of the surface properties. One amine-based anti-stripping agent, AD-here HP Plus, is studied to evaluate its effect on adhesion and moisture susceptibility of the WMA. While its performance as an anti-stripping agent was good on the plain asphalt binder, AD-here HP Plus did not improve the adhesion of the selected binder modified with WMA additives either in dry or wet condition. The free energy of adhesion in wet and dry conditions showed either detrimental or no effect with selected aggregates, suggesting a negative or no influence of AD-here HP Plus on the WMA additive-modified binder.

Effectiveness of water-bearing and anti-stripping additives in warm mix asphalt technology

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 binders 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.

Laboratory characterisation of asphalt mixes containing RAP and RAS

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 todays 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.

Rheological Evaluation of Warm Mix and Anti-Stripping Additives Modified Performance Grade Binders

ABSTRACT This study evaluated the effects of a warm mix asphalt (WMA) additive, Sasobit®, and a liquid anti-stripping agent, AD-here® HP Plus, onthe rheological properties of a selected performance grade binder (PG 64-22) as per Superpave® specifications. The optimum dosage (mass) of Sasobit®was found to be 1.5%, which was expected to reduce the mixing and the high PG temperatures by 9oC and 4.5oC, respectively. Sasobit® was also found to decrease the fatigue resistance and low temperature resistance of the base binder to some extent. Furthermore, a reduced rolling thin film oven (RTFO) temperature was expected to exhibit significant reduction in the rut resistance of the WMA. While anti-stripping agent was expected to reduce the rutting resistance, it was anticipated to increase low temperature resistance of the WMA. The findings of this study are expected to enhance rheological database and help in implementing WMA mixes in Oklahoma and elsewhere.

Behavior of Selected Warm Mix Asphalt Additive Modified Binders and Prediction of Dynamic Modulus of the Mixes

This study evaluated the viscoelastic properties of a performance grade binder modified with different dosages of a selected wax-based warm mix asphalt (WMA) additive (WMA1). The effects of reduced rolling thin film oven (RTFO) aging on the stiffness of the WMA1-modified binder were also evaluated. The viscoelastic properties of the modified binders were then used to estimate the dynamic modulus (E*) values of the WMA mixes through time temperature superposition principles. Furthermore, the effects of a selected liquid anti-stripping agent (ASA), ASA1, on the properties of the WMA1-modified binder were investigated. It was observed that the linear viscoelastic limits of WMA1-modified binders decreased with an increasing dosage of WMA1. Reduced RTFO aging was found to have significant effects on the stiffness of the WMA1-modified binder. The Hirsch model was found to provide better approximations of the E* values than the Witczak model. The Witczak model, based on dynamic shear rheometer data, was found to significantly underestimate the E* values. Although ASA1 did not reduce the beneficial effects of WMA1, it was found to increase the E* values of the WMA mix. The findings of this study are expected to offer transportation professionals a better understanding of the evaluation of WMA binders and mixes.

Moisture Susceptibility Evaluation of Nanosize Hydrated Lime-Modified Asphalt-Aggregate Systems Based on Surface Free Energy Concept

Moisture susceptibility can cause cohesive and adhesive failures in the asphalt–aggregate system, resulting in serious pavement distresses. The role of regular hydrated lime (RHL) as an antistripping agent in asphalt pavements has been widely addressed with traditional moisture susceptibility evaluation methods. However, the use of nanosize hydrated lime (NHL) in asphalt industries has not yet been initiated. The first objective of this study was to assess the RHL- and NHL-modified asphalt binders on the basis of the surface free energy (SFE) concept by using the Wilhelmy plate method. Advera, a warm-mix asphalt (WMA) foaming additive, was added to the hydrated lime-(RHL and NHL) modified asphalt binders to address the effect of foaming on cohesive bond strength. The NHL material was added with particle sizes of 50 and 100 nanometers. The second objective was to address the adhesive bond strength between the aforementioned asphalt binders and different aggregates. Different acidic and basic aggregates with known SFE components were used along with measured SFE components of the asphalt binders to determine quantitatively the free energy of adhesion in the system. Overall results reveal that SFE components of asphalt binders are dependent on the particle size of hydrated lime. In general, the cohesive bond of the NHL-modified asphalt binder was higher than that of the RHL-modified binder. As hydrated lime particle size decreases, dry and wet adhesive bonds increase. Moisture susceptibility of Advera-foamed mixes seems to depend on aggregate type. The NHL-modified mixes are expected to perform better than RHL-modified mixes in dry and wet conditions.

Evaluation of Viscosity and Rutting Properties of Nanoclay-Modified Asphalt Binders

In pavement constructions, asphalt binders are often modified with synthetic polymers to sustain excessive heat during hot summer days. However, the cost of a polymer-modified binder (PMB) is significantly higher than a neat binder. Nanoclays, however, are relatively inexpensive and naturally abundant and have favorable intrinsic properties (e.g., nanoscopic size and surface area) toward increasing its stiffness. The current study evaluated viscoelastic properties of a performance grade (PG 64-22OK) binder modified with different dosages of Cloisite 15A nanoclay. The state of dispersion and exfoliation of the nanoclay binders were examined using scanning electron microscope (SEM) and X-ray diffraction (XRD) techniques. Preliminary results show that 1% and 2% of Cloisite 15A increased the Superpave rutting factor of the base binder by 16% and 26%, respectively. The rotational viscosity (RV) tests reveal a significant increase in the viscosity of the base binder. The stiffness of the 2% nanoclay-modified binder was found to be about the same as that of a PMB-modified (PG 70-28OK) binder, indicating nanoclays can potentially be alternatives to PMBs toward reducing pavement construction and maintenance costs.

Sensitivity of Oklahoma Binders on Dynamic Modulus of Asphalt Mixes and Distress Functions

AbstractFor 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 (E*) 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 E* 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 r...

Investigation of Rheological Properties of Asphalt Rubber toward Sustainable Use of Scrap Tires

About 300 million scrap tires are generated each year in Unites States. The improper disposal of these scrap tires has posed serious threat to public health and environmental safety over the last few decades. The objective of this study is to assess the viability of sustainable utilization of scrap tires as ground tire rubber (GTR) to prepare new asphalt rubber (AR) by investigating their rheological and mechanistic properties. AR is reported to provide a longer lasting road surface, reduced road maintenance, reduced noise, and shorten breaking distance. The current study has gathered lessons learned and best practices from prior studies. Toward evaluating the mechanistic performance, three different amounts (10%, 15%, and 20%, by the weight of the binder). GTR have been blended with a base binder (PG 64-22) to prepare AR binder samples though the wet process and their rheological properties were tested in accordance with Superpave test protocols. Viscosity and penetration test results reveal that AR is significantly stiffer and it possesses higher rutting resistance compare to the base binder. Preliminary test data and life cycle cost analysis of a typical pavement section suggest that AR is a viable and sustainable alternative to the commonly used polymers.