SHRP-A-379 traducir

5.2 The complex shear modulus is an indicator of the stiffness or resistance of
asphalt binder to deformation under load. The complex shear modulus and the phase angle
define the resistance to shear deformation of the asphalt binder in the linear viscoelastic
region. Other linear viscoelastic properties, such as the storage modulus (G'), or the loss
modulus (G"), can be calculated from the complex modulus and the phase angle. The loss
modulus is a measure of the energy dissipated during each loading cycle.
5.3 The complex modulus and the phase angle are used to calculate performancerelated
criteria in accordance with MP1.
6. APPARATUS
6.1 Dynamic Shear Rheometer Test System--A dynamic shear rheometer test system
consisting of parallel metal plates, an environmental chamber, a loading device, and a control
and data acquisition system.
6.1.1 Testplates--Metal test plates with smooth polished surfaces. One 8.00 + 0.05
mm in diameter and one 25.00 + 0.05 mm in diameter. The base plate in some rheometers
is a flat plate. A raised portion 2 to 5 mm high with the same radius as the upper plate is
recommended. The raised portion makes it easier to trim the specimen and may improve test
repeatability.
6.1.2 Environmental Chamber--A chamber for controlling the test specimen
temperature, by heating (in steps or ramps), or cooling (in steps or ramps), to maintain a
constant specimen environment. The medium for heating and cooling the specimen in the
environmental chamber is a gas or liquid (note 1) that will not affect asphalt binder
properties. The temperature in the chamber may be controlled by the circulation of fluid or
conditioned gas; nitrogen or water is acceptable. When air is used, a suitable drier must be
included to prevent condensation of moisture on the plates and fixtures and, if operating
below freezing, the formation of ice. The environmental chamber and the temperature
controller shall control the temperature of the specimen, including thermal gradients within
the sample, to an accuracy of + 0.1 °C. The chamber shall completely enclose the top and
the bottom plates to minimize thermal gradients.
NOTE1.--A circulating bath unit separate from the dynamic shear rheometer which pumps the bath fluid
through the test chamber may be required if a fluid medium is used.
6.1.2.1 Temperature Controller--A temperature controller capable of maintaining
specimen temperatures within 0.1 °C for test temperatures ranging from 5 to 85°C.
6.1.2.2 Temperature Detector--A reference thermal detector (RTD) mounted inside
the environmental chamber, in intimate contact with the fixed plate, with a range of 5 to
85°C, readable and accurate to the nearest 0.1°C. This detector shall be used to control the
temperature in the chamber and provide a continuous readout of temperature during the
mounting, conditioning, and testing of the specimen.
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