Assessing the Asphalt Binder Film Thickness in Recycled Asphalt Mixtures Using Micro-Level Techniques (original) (raw)
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2021
Asphalt binder film thickness has relation to mixing temperature and binder content in hot mix asphalt, which influences mixture’s performance. A significant variation in assessing the asphalt binder film thickness has been observed in the literature. Development of state of the art technology and Superpave specification requires the study of actual asphalt binder film thickness at micro-level. This study estimates asphalt binder film thickness at micro-level and compares results with those obtained through analytical models from the previous studies. The study utilizes different asphalt mixtures at various mixing temperatures and binder contents. The asphalt binder film thickness around the finest particles of 500 nm (0.5 micron) size in asphalt mastic was detected and measured by image analysis (using scanning electron microscope) and elemental analysis (using energy dispersive X-ray spectroscopy) at magnifying power of ×30,000. The analytical estimation revealed that the asphalt ...
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Motivated with sustainability and economic factors, there is a rapid increase in the use of recycled asphalt pavement (RAP) material in the construction of new asphalt pavements. This necessitates the development of better understanding of the interaction between recycled and virgin binders, as well as studying the influence of this interaction on the properties of the blended binder. This paper provides in-depth evaluation of these properties at various scales using chemical, mechanical and rheological tests. This study involved the use of binders with different proportions of RAP (0, 15, 25, 35 and 100%). The chemical characterization of these binders was carried out using Fourier Transform Infrared Spectroscopy (FTIR), and the results showed that higher peak levels of C@O and S@O bonds were observed with the increase in RAP binder content. Atomic Force Microscopy (AFM) imaging of these binders showed that the surface roughness increased with an increase in RAP content especially when the RAP proportion exceeded 25%. The multiple stress creep recovery (MSCR) test was used to measure the rutting resistance, and the linear amplitude sweep test (LAS) was used to evaluate the fatigue resistance. There was slight improvement in rutting resistance with an increase in RAP content; however, the fatigue resistance degraded with the addition of RAP. The moduli/stiffness of virgin, RAP and blended binders was determined using Dynamic Shear Rheometer (DSR), Nanoindentation (NI), and AFM. The moduli obtained from these three techniques increased exponentially and at similar rates up to 25% of RAP. However, the dynamic modulus from DSR increased at a higher rate than the nano-scale moduli at higher RAP contents. This finding suggests that the nano-scale interactions were not influenced by the increase in RAP content as the DSR measurements of dynamic modulus and fatigue life values imply. The nano-scale understanding of blended binder offers opportunities for better engineering and accommodation of RAP in asphalt mixtures.
Validity of Asphalt Binder Film Thickness Concept in Hot-Mix Asphalt
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Despite the possible benefits of implementing asphalt binder film thickness into current specifications to address durability problems, most of the related research has been theoretical and only a few attempts have been made to measure this property experimentally. The objective of this study was to investigate the concept of asphalt binder film thickness experimentally on the basis of measurements obtained by image analysis techniques, reflective light microscopy, and scanning electron microscopy. The results of the experimental program were used to gain insight into the concept of asphalt binder film thickness and its validity. Experimental results indicated that asphalt binder films coating large aggregates do not actually exist in hot-mix asphalt. Instead, what are referred to as asphalt binder films surrounding large aggregates are actually asphalt mastic films. These films are highly irregular in shape and have a thickness greater than 100 μm in the mixture considered in this ...
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Internal Structure Features of Asphalt Mixture for Field Samples
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Asphalt mixture is heterogeneous in nature; consequently, macroscopic parameters alone cannot describe the mechanical behavior of the mixture. In recent years, the arrangement of the aggregate particles in terms of spatial and directional distributions, and contact points are contemplated as the internal structure of asphalt. The main purpose of this article is to examine the microstructural characteristics of asphalt cores applying 2-D images. Comparison between the internal structure features in the laboratory samples and the Field samples is indicated in this paper. The results reveal that the survey of microstructural characteristics of asphalt cores by image processing provides new and functional information. This finding indicates that the number of contact points in cores is close to the lab samples that have been made at 45 to 65 blows on each end of the sample.
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An X-ray diffraction (XRD) technique has been applied to the study of asphalt binders. XRD patterns were obtained using a Rigaku DMax 2200 V-PC (personal computer). Jade software (version 6.1) was used to perform the peak search, full width at half-maximum, and profile fits with Pearson VII and pseudo-Voigt mathematical functions over the areas of interest. The XRD spectra were also modeled in Mathematica using a generalized Fermi function (GFF). Analysis shows a mixed correlation in the data in terms of mathematical fit, analysis of fit, and plotting. Aromaticity and crystallite size parameters were calculated for the asphalt binders using the data from the three functions (Pearson VII, pseudo-Voigt, GFF). Results are compared and discussed with respect to aging effects, asphalt binder models (Yen, Yen−Mullins), and fuel technology.
Asphalt binders characterization and modeling x-ray diffraction
2018
Cracking is a common occurrence in asphalt pavements in colder climates, while pavements in hotter climates experience rutting; both of which are considered on-going problems from an industry standpoint. Asphalt presents in crude oil was studied to know their structure with the help of X-ray diffraction (XRD). Six samples of Asphalt binder were taken from Canada and USA then converted into thin films of 1mm to get XRD pattern. In addition, Cu-K-a monochromatic radiations were used at 40kV using a Rigaku DMax 2200V-PC at 40 mA with scan ranges from 2θ= 5⁰ to 35⁰ and 60⁰ to 110⁰. Mathematical functions such as Pearson VII and Pseudo-Voigt are used to profile fit the data obtained by the XRD. After profile fitting, they are modeled using GFF i.e. Generalized Fermi Function in Mathematicaᵀᴹ. The analysis showed a correlation among the three mathematical functions. The outcomes discussed here substitute to the accuracy of profile fitting whereas the exponents of Pearson VII and pseudo- V...
Use of X-ray diffraction in assessing the aging pattern of asphalt fractions
Fuel, 2002
The X-ray diffraction (XRD) method was employed to investigate and compare some of the crystallite parameters and aromaticity of asphaltenes obtained from fresh and aged Arabian asphalts, procured from Ras Tanura (RT) and Kuwait (KW) re®neries. A few crystallite parameters in the polar aromatics, naphthene aromatics and saturate fractions of these Arabian asphalts were also determined. The results obtained by XRD method for both the types of asphaltenes and other fractions were evaluated and compared. Signi®cant differences were observed between the structure and the aging patterns of fresh and aged asphaltenes of RT and KW asphalt. The results indicate that the source and chemistry of asphalt are responsible for the aging behavior of its components. The rolling thin-®lm oven and the pressurized aging vessel tests were used to simulate asphalt aging in this research. q
A practical approach to estimate the degree of binder activity of reclaimed asphalt materials
Road Materials and Pavement Design, 2019
A practical approach to estimate the degree of binder activity of reclaimed asphalt materials Using Reclaimed Asphalt (RA) in new asphalt mixtures can reduce the amount of new material required thereby saving money and natural resources. In addition, asphalt mixtures with RA have shown comparable properties and performance to that generally associated with asphalt mixtures made with 100% virgin material. However, RA content in pavement surface layers is still limited due to specification and technical limitations. For higher contents, the aged RA binder must be analysed to accurately determine the requirements for virgin binders and additives while the degree of blending (DOB) between the RA binder and the virgin binder also needs to be quantified. This is not a simple process and generally designers assume one of two opposing theories associated with 100% (full blending) or 0% ("Black Rock") DOB. This paper proposes a new approach to estimate a unique property of the RA known as the Degree of Binder Activity (DoA) as a function of the processing temperatures of the RA. The study showed positive results and indicated that this DoA approach can be used as a tool to better understand RA in order to improve the binder/blend design for recycled asphalt mixtures.