Normal stress and stress relaxation of sand asphalt mixtures are measured using a torsional rheometer. The description and the operating principle of the torsional rheometer and the measurement procedure are presented. The raw data obtained, namely the torque and the normal force, are documented for different rotation rates and loading times. Repeated experiments exhibit remarkable consistency and show that the normal force and the torque decrease with the decrease in rotation rate. The results show the necessity for developing non-linear constitutive models for asphalt mixtures. © 2004 Published by Elsevier Ltd.

Krishnan J Murali

Department Of Civil Engineering

Lavankumar Reddy Kasula

K.R.Rajagopal

D.N.Little

Concretes

FLUID MECHANICS

Granular materials

Non Newtonian flow

sand

stress relaxation

Torque

Torsional stress

ASPHALT MIXTURES

SAND ASPHALT

TORSIONAL FLOW

Asphalt

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Mechanics Research Communications

This paper presents the results of a set of transient experiments conducted on asphalt binders that serve to highlight the nonlinearity of the viscoelastic response of asphalt binders. Two grades of binders were used in this study. A transient test that combines both creep and stress relaxation tests was conducted using a dynamic shear rheometer at several loading conditions and at different temperatures. The acquired experimental data was satisfactorily fit using a nonlinear six-parameter viscoelastic model. © 2012 Taylor &amp; Francis.

Road Materials and Pavement Design

Nonlinear viscoelastic response of asphalt binders in transient tests

Sand-asphalt mixtures are difficult to model, partly due to their composition and partly due to the complex interplay among their constituents. This work is concerned with the development of an anisotropic model to describe the nonlinear behaviour of sand-asphalt mixtures. A general thermodynamic framework is used, which allows for the material to have multiple natural configurations corresponding to its underlying structure. The evolution of the natural configuration takes place in a thermodynamically consistent manner. The model developed is corroborated using experimental results published by Ravindran et al. (2007a,b) on torsion tests of sand-asphalt specimens over a range of conditions. © 2009 Taylor &amp; Francis.

International Journal of Pavement Engineering

Modelling sand-asphalt mixtures within a thermodynamic framework: Theory and application to torsion experiments

Asphalt is processed in India through various means such as straight-run, air blown and blending. Production of asphalt for paving purposes in some of the refineries is carried out by blending the heavy extract with the PDA pitch. Since 60/70 or 80/100 penetration grade is predominantly used in India, appropriate proportions of PDA pitch and extract are determined to meet the penetration grade. Considering the current move in India towards viscosity grading and then to performance grading, a need was felt to observe the rheological properties of blended asphalt and the role of blending process on the final end product. This investigation reports the rheological characterization of various blends made with PDA pitch and heavy extract. Three blend proportions were manufactured by two different blending process and all the blends were subjected to short term aging in rolling thin film oven. The unaged and short term aged blends were tested for steady shear, creep and recovery and stress relaxation properties. The single point measurement of viscosity at a specific temperature cannot reveal the complex behaviour of asphalt. A complete and systematic rheological characterization is necessary. In fact, this investigation reports for the first time, stress overshoot in steady shear and measurement of first normal stress difference relaxation for blended asphalt. From the analysis of the experimental data it is shown that blends with higher proportion of PDA pitch are more temperature susceptible and the blending process tends to “homogenize” the mixture. One can use the data gathered from these experiments for designing asphalt blend with the required appropriate property. These experiments also underline the requirement to develop non-linear constitutive models for asphalt and asphalt blends. © 2008 Taylor &amp; Francis Group, LLC. All rights reserved.

Rheological characterization of blended paving asphalt

There is sparse documentation of the large normal stresses that develop in asphalt mixtures subjected to shear, a typical characteristic of non-linear materials. In this study, we continue our initial investigations of using a torsional rheometer for measuring the normal stresses developed in asphalt mixtures when subjected to torsion. Samples of sand-asphalt mixture are subjected to rotation rates as low as one revolution in ninety minutes. This study provides further clear evidence of significant development of normal stresses due to shearing and emphasizes the need for the development of models that can describe such a phenomenon. © 2007 Elsevier Ltd. All rights reserved.

Characterization of the non-linear response of asphalt mixtures using a torsional rheometer

This study documents the measurement of normal stresses and stress relaxation in sand-asphalt mixtures fabricated with different fillers and asphalts during torsion. Hydrated lime and limestone fillers and asphalts graded as PG64-22 and AC-30 (from Sinclair (Wyoming), Crown (Nevada), and Crown (Canada)) are used in the fabrication of the sand-asphalt mixtures. The specimens are tested in a torsional rheometer. The experimental results clearly show that the normal stresses that are developed are quite significant even for specimens tested at very low rotational rates. Also, asphalts from different sources show differences in peak normal stresses and in their relaxation pattern. The measurement of significant normal stresses is a reflection of the nonlinear character of the material and warrants the development of nonlinear constitutive models for describing their behavior. Copyright © Taylor &amp; Francis Group, LLC.

Particulate Science and Technology

An experimental investigation into the influence of fillers on the development of normal stresses and stress relaxation in asphalt mixtures due to torsion

Knowledge of the mechanical and thermodynamic behavior of straight run asphalt is desirable in view of its use as a binder for pavement applications. The different complex processes undergone by asphalt concrete mixtures such as healing, aging, etc. can be understood more clearly, if one has a better understanding of the constitutive behavior of asphalt. The need is pressing as the use of polymer-modified asphalt as a binder has increased in recent years. Most of the studies carried out on constitutive modeling of asphalt model pure asphalt either as a Newtonian fluid or as a linear viscoelastic fluid over a wide range of temperatures. The complexity related to the study of the constitutive behavior of asphalt is compounded by the fact that asphalt is a mixture of different chemical species some of which are amorphous and some of which are crystalline in nature. The relaxation mechanisms of asphalt are diverse with different relaxation mechanisms at different temperatures. In this study, we use a thermodynamic framework for the constitutive modeling of asphalt and we model asphalt as a material with multiple relaxation mechanisms. This framework recognizes the fact that materials like asphalt can exist in more than one natural configuration (for instance, stress free configuration). We use the experimental data available in the literature (Lethersich, W., 1942. The mechanical behaviour of bitumen. Journal of the Society of Chemical Industry 61, 101-108; Cheung, C.Y., Cebon, D., 1997. Experimental study of pute bitumens in tension, compression, and shear. Journal of Rheology 41 (1), 45-73) for asphalt from different sources and demonstrate the efficacy of the model. © 2005 Elsevier Ltd. All rights reserved.

Mechanics of Materials

On the mechanical behavior of asphalt

Treatise on Natural Philosophy

Triaxial testing and stress relaxation of asphalt concrete

Journal of Materials in Civil Engineering

Thermodynamic Framework for the Constitutive Modeling of Asphalt Concrete: Theory and Applications

Applied Mechanics Reviews

Review of the uses and modeling of bitumen from ancient to modern times

Normal stress and stress relaxation data for sand asphalt undergoing torsional flow

Journal	Data powered by TypesetMechanics Research Communications
Publisher	Data powered by TypesetElsevier Ltd
ISSN	00936413
Open Access	No