Evaluation of Stiffness, Strength, and Ductility of Asphalt Binders at an Intermediate Temperature

Author(s):  
Ramez Hajj ◽  
Rachel Hure ◽  
Amit Bhasin

The search for a test and parameter that can effectively describe the fatigue cracking resistance of an asphalt binder has led to many approaches. Of these, researchers have used stiffness, strength, and ductility-based criteria to screen binders on the basis of inherent resistance to cracking. In this study, poker chip testing on thin films of asphalt binder was used at intermediate temperatures to obtain both stress and ductility-based properties of eight binders. In addition, a dynamic shear rheometer frequency sweep at an intermediate temperature was conducted to obtain stiffnesses of the binders and a surrogate parameter for ductility. The results showed no relationship between strength and stiffness. In most cases, binders that were rated to have high ductility on the basis of the dynamic shear rheometer parameter also had high toughness on the basis of the poker chip test. However, some binders clearly departed from this trend, with at least one binder exhibiting both ideally desired high stiffness and toughness. Examination of failure surfaces from the poker chip test provided additional information about the mechanisms that drove failure.

Author(s):  
Ramez Hajj ◽  
Angelo Filonzi ◽  
Syeda Rahman ◽  
Amit Bhasin

The low-temperature properties of asphalt binder have attracted attention in recent years thanks to an increase in the use of reclaimed asphalt pavements (RAP). Traditional methods to evaluate the low-temperature properties of the binder require a large amount of binder that needs to be recovered from RAP samples for testing with a Bending Beam Rheometer (BBR). To economize on sample size for RAP materials and also for emulsion residues, previous researchers have explored the potential of using a 4 mm diameter specimen with a Dynamic Shear Rheometer (DSR) in lieu of the BBR. To compare results from frequency sweep tests conducted using the DSR with results from the BBR, data from the former need to be converted to time domain and subsequently from a shear load response to an axial load response. Previous research studies have developed methods to accomplish these two conversions to compare data from the DSR with data from the BBR. The objective of this study is to examine some of these methods from the literature and elsewhere based on the principles of linear viscoelastic interconversion using a set of 11 different binders. Results using different analytical approaches from this study show that the DSR has good repeatability and verify that it can be used as a surrogate for the BBR to determine low-temperature properties, while exercising some caution with some of the assumptions related to Poisson’s ratio.


Author(s):  
Panos Apostolidis ◽  
Cor Kasbergen ◽  
Amit Bhasin ◽  
Athanassios Scarpas ◽  
Sandra Erkens

With the effort to precisely predict the lifetime of asphalt binders and subsequently optimize their utilization in a more economical way, the objective of this study was to introduce a new methodology to improve the fatigue characterization of asphalt binders through a new dynamic shear rheometer (DSR) sample testing geometry. Initially, numerical analyses were performed to study the geometry-related issues of a standard DSR sample on time sweep tests, and to assist in the effort to increase understanding of the DSR damage phenomena of asphalt samples. On the basis of these numerical analyses, a new testing geometry, the parallel hollow plate, was developed and its test results compared with the standard sample testing geometry. A single type of asphalt binder was assessed using amplitude sweep tests. The obtained results demonstrated a significant difference between the fatigue of the two sets of DSR sample geometries. On the basis of these, time sweep tests were conducted for the same sample geometries and the results demonstrated that the new testing geometry yields material response consistency under different loading conditions. The lifetime prediction of the standard parallel plates showed a significant difference with the newly developed DSR sample testing geometry by overestimating the total number of cycles until asphalt binder failure. The new testing geometry allowed the isolation of the damaged area of asphalt binder by localizing the shear stresses in the samples’ periphery.


2019 ◽  
Vol 29 (1) ◽  
pp. 30-40 ◽  
Author(s):  
André K. Kuchiishi ◽  
João Paulo B. Carvalho ◽  
Iuri S. Bessa ◽  
Kamilla L. Vasconcelos ◽  
Liedi L.B. Bernucci

Abstract Asphalt pavement is under different climatic conditions throughout its service life, which means that fatigue cracking does not occur at a specific temperature, but at a temperature range. The main objective of this paper is to evaluate the influence of different temperatures in the fatigue life of two asphalt binders: a non-modified binder (penetration grade 30/45) and a highly polymermodified binder (HPMB). The fatigue resistance characterization was performed by means of a linear amplitude sweep (LAS) test at the temperatures of 10, 15, 20, 25, and 30°C using a dynamic shear rheometer (DSR). From the dynamic shear modulus (|G*|) results, adhesion loss was observed between the binder and the rheometer parallel plate at the lower temperature of 10°C,while at higher temperatures (25 and 30°C) plastic flow was observed rather than fatigue damage. Therefore, considering that the actual test procedure does not specify the testing temperature, the evaluation of failure mechanism is essential to validate test results, because the random selection of test temperature might lead to inconsistent data.


Author(s):  
Javier J. García Mainieri ◽  
Punit Singhvi ◽  
Hasan Ozer ◽  
Brajendra K. Sharma ◽  
Imad L. Al-Qadi

Fatigue cracking caused by repeated heavy traffic loading is a critical distress in asphalt concrete pavements and is significantly affected by the selected binder. In recent years, the growing use of recycled asphalt materials has increased the need for the production of softer asphalt binder. Various modifiers/additives are marketed to adjust the grade and/or enhance the binder performance at high and low temperatures. The modifiers are expected to alter the rheological and chemical characteristics of binders and, therefore, their performance. In this study, the damage characteristics of modified and unmodified binders, at standard long-term and extended aging conditions, were tested using the linear amplitude sweep (LAS) test. Current data-interpretation methods for LAS measurements (including AASHTO TP 101-12, T 391-20, and recent literature) showed inconsistent results for modified binders. An alternative method to interpret LAS results was developed in this study. The method considers the data until peak shear-stress is reached because complex stress states and failure patterns are observed in the specimens after that point. The proposed parameter (Δ| G*|peak τ) quantifies the reduction in complex shear modulus measured at the peak shear-stress. The parameter successfully captures the effect of aging and modification of binders.


2015 ◽  
Vol 16 (sup1) ◽  
pp. 211-227 ◽  
Author(s):  
Jean-Claude Carret ◽  
Augusto Cannone Falchetto ◽  
Mihai O. Marasteanu ◽  
Hervé Di Benedetto ◽  
Michael P. Wistuba ◽  
...  

2020 ◽  
Vol 2020 ◽  
pp. 1-17 ◽  
Author(s):  
Nonde Lushinga ◽  
Liping Cao ◽  
Zejiao Dong ◽  
Chen Yang ◽  
Cyriaque O. Assogba

This research was conducted to elucidate better understanding of the performance of crumb rubber asphalt modified with silicone-based warm mix additives. Two different silicone-based warm mix asphalt (WMA) additives (herein Tego XP and Addibit) were used to prepare crumb rubber modified (CRM) warm mix asphalt binders. The viscosity of these CRM binders was measured at different temperatures and shearing rates. Furthermore, softening point and penetration tests, Multiple Stress Creep Recovery (MSCR), Time Sweep (TS), Atomic Force Microscopy (AFM), Frequency sweep (FS), and Fourier Transform Infrared (FTIR) tests were also conducted on prepared samples. Based on these robust and rigorous laboratory experiments, it was established that viscosity of CRM binders was reduced by addition of Tego XP and Addibit WMA additives. However, WMA additives had different influence on rheological properties of the binder. CRM binder with Tego XP improved resistance to rutting of the binders but would degrade the fatigue performance. On the contrary, viscoelastic continuum damage (VECD) model results and those of phase angle approach revealed that the binder with Addibit improved resistance to fatigue cracking of the binders but had no adverse effects on high temperature rutting performance. FTIR test results established a presence of polydimethylsiloxane (PDMS) in CRM binders with Tego XP and Addibit. PDMS is a well-known hydrophobic organic and inorganic polymer that is water repellent; therefore, binders containing these silicone-based warm mix additives could be beneficial in resisting moisture damage in asphalt binders and mixtures. Morphology of CRM binders with and without WMA revealed good distribution of the rubber particles in asphalt binder matrix. Further addition of WMA increased surface roughness of the binder, which can be correlated to changes in microstructure properties of the binder. Therefore, the study concluded that addition of Tego XP and Addibit reduces viscosity and improves mechanical properties of the asphalt binder.


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