Use of Viscosity Standard Fluid To Control Quality of Rheological Measurements for Characterizing Asphalt Binders
01 Jan 1997-Transportation Research Record (Transportation Research Board of the National Academies)-Vol. 1586, Iss: 1586, pp 24-31
TL;DR: In this paper, the results of a study to establish a protocol for calibrating and maintaining Superpave rheometers are described, and the main objective was to determine whether sound calibration practices and adequate training can improve the repeatability and reproducibility of the rheological parameters required in the SuperPave binder specification.
Abstract: The results of a study to establish a protocol for calibrating and maintaining Superpave rheometers are described. The reference standard material used was supplied by Cannon Instrument Co. The material (high viscosity standard) is designated as N2700000 and is supplied with ASTM traceable values of steady shear viscosity at various Superpave specification temperatures. The main objective was to determine whether sound calibration practices and adequate training can improve the repeatability and reproducibility of the rheological parameters required in the Superpave binder specification. Ten laboratories participated in the study. The results indicate that the viscosity standard can be used as a standard fluid to calibrate and maintain the Superpave rheometers. The repeatability and reproducibility data were compared with similar estimates reported by the AASHTO Materials Reference Laboratory. It was found that the reproducibility (between-laboratory variation) improved by a factor of two and repeatabilit...
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01 Jan 2002
TL;DR: In this article, the linearity limits of various unmodified (penetration grade) and modified (both process modification and polymer modification) bitumens and asphalt mixtures incorporating these binders have been determined by means of stress sweeps at various temperatures and frequencies using a dynamic shear rheometer (DSR).
Abstract: In order to predict the engineering performance of a material, it is necessary to understand its stress/strain behaviour. This is usually accomplished by means of laboratory tests under controlled stress or controlled strain conditions. As bituminous materials are viscoelastic in nature, their performance must be characterised with test methods and analytical techniques that account for time (or rate) of loading and temperature. In addition, it is usually advisable to confine the characterisation of a bitumen to its linear viscoelastic (LVE) response (small strains) to simplify the mathematical modelling of the material, as non-linear response, particularly for viscoelastic materials, is extremely difficult to characterise in the laboratory and model in practical engineering problems. This thesis describes research into the linearity limits of various unmodified (penetration grade) and modified (both process modification and polymer modification) bitumens as well as the linearity limits of asphalt mixtures incorporating these binders. The linearity limits for the binders have been determined by means of stress sweeps at various temperatures and frequencies using a dynamic shear rheometer (DSR). The linearity limits and dynamic mechanical properties of the conventional and modified asphalt mixtures have been determined by means of a purpose built dynamic, direct tension-compression, servo-hydraulic testing apparatus. The linearity results show that for sensibly engineered modified binders (softer base bitumens with higher modifier contents) there is no significant narrowing of the linear range. The process modified, plastomeric (EVA PMB) and conventional binders show a strain dependent LVE criterion between 2% and 6% at low temperatures (high stiffness and intermediate to low phase angles) as well as a stress dependent LVE criterion between 1.5 and 7 kPa at high temperatures (low stiffness and high phase angles). The thermoplastic rubbers (SBS PMBs) show, in addition to the low temperature strain criterion, a high temperature (low stiffness) polymeric-based strain dependent LVE criterion between 50% and 150%. The asphalt mixtures studied in this thesis consisted of dense bitumen macadam (DBM), hot rolled asphalt (HRA) and HRA mortar mixtures with conventional 50 pen bitumen, radial and linear SBS PMBs, EVA PMB and multigrade bitumen. Cylindrical specimens of the mixtures were subjected to sinusoidal loading conditions at temperatures between 10 and 40°C under stress sweep conditions. The results indicate that the linearity limits of behaviour for the asphalt mixtures are strain dependent and found to be between 20 and 100 microstrain for the DBM and HRA mixtures and between 50 and 150 microstrain for the HRA mortars. Additionally, upon establishing the LVE limit, the viscoelastic properties of the bitumens and asphalt mixtures, in their linear region, were evaluated by means of frequency sweep tests at various temperatures and frequencies. The results show that, in the low frequency region (high temperatures), the rheological behaviour of the SBS PMBs differs from that of the other bitumens. The DBM and HRA mixtures all show very similar rheological characteristics over the temperature and frequency range used in this study. With regard to the HRA mortars, due to their higher binder and air void volumetric proportions, their stiffness values tend to be approximately half that of the DBM and HRA mixtures. Finally, the relationship between binder and mixture stiffness was investigated in the linear viscoelastic region, for different unmodified and modified binders and asphalt mixtures. Measured asphalt mixture stiffness was compared with selected empirical and theoretical mixture stiffness prediction methods. In general, the bitumen to mixture complex modulus relationship was independent of temperature. However, although a straight line could be established for the EVA PMB and linear SBS PMB binders, the results show that the binder to mixture stiffness relationship exhibits temperature dependence for mixtures produced with these two binders. The results show that there are large differences between the stiffness predicted by the empirical and theoretical methods and those measured experimentally.
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1,719 citations
01 Jan 1991
TL;DR: In this article, the authors describe the program of research that is being pursued by the authors to develop new or improved test methods and specification criteria that are suitable for the development of a performance-related specification for asphalt cement.
Abstract: One of the primary objectives of the Strategic Highway Research Program (SHRP) is to develop performance-related specifications for asphalt cement. This paper describes the program of research that is being pursued by the authors to develop new or improved test methods and specification criteria that are suitable for the development of a performance-related specification for asphalt cement. This paper consists of six sections, each of which is relevant to the problem of developing more effective specifications for paving grade asphalts: (1) a review of asphalt rheology; (2) a brief discussion of the chemistry and microstructure of asphalt cement; (3) a review of the traditional methods of characterization; (4) a discussion of the shortcomings of current specifications; (5) a description of proposed test methods and specification framework; and (6) a final section in which the information presented in this paper is summarized, and a few important conclusions are made concerning the development of performance-related specifications for asphalt cement.
124 citations
TL;DR: In this paper, the precision of complex viscosity measurements in the constant stress and constant strain modes was examined for isotropic polymeric melts with a Bohlin Controlled Stress Melt Rheometer, which was used to make the measurements, covering a stress range of 400 to 3227 Pa and a frequency range of 0.01 to 30 hertz.
Abstract: This paper examines the precision of complex viscosity measurements in the constant stress and constant strain modes. A Bohlin Controlled Stress Melt Rheometer was used to make the measurements, which cover a stress range of 400 to 3227 Pa and a frequency range of 0.01 to 30 hertz. In principle, oscillation in the linear region should give the same values regardless of how it is done. In reality, various measurement modes exhibit different precision. A wide range of parameters encompassing three decades in complex viscosity and over three decades in frequency are considered. Contrasting frequency dependence, i.e., shear-thinning and Newtonian plateau, are also considered. Constant stress measurements are found to provide improved precision at lower frequencies, while constant strain measurements provide improved precision at higher frequencies. This is significant because low frequency data are often used to estimate the zero-shear viscosity, which correlates with the weight-average molecular weight. The “between-sample” and “within-sample” components of the total variation are examined separately for poly(dimethyl siloxane) and polyethylene. To do this for polyethylene, a new technique (moving range average) had to be used. Initial attempts at modeling are discussed. The discussion is limited to isotropic polymeric melts. This paper provides guidance in determining the most appropriate way to perform oscillation.
6 citations