ASTM D7741-11

This test is primarily used for field production control of Asphalt-Rubber (A-R) and other high viscosity binders; however the test can also be used in a laboratory setting.

A hand held rotational viscometer is used to measure the apparent viscosity of a completed blend of A-R or high viscosity binder. A rotor (spindle), turning at constant speed, is inserted in the liquid binder to be measured. The resistance to movement of the spindle (torque) caused by the viscosity of the surrounding liquid is measured using a special mechanism to obtain direct readings in Pa·s or cP.

Note 1—Spindle generally made of stainless steel, although another metal such as brass could be used.

The measured apparent viscosity is used to control the production of the A-R or other high viscosity binder, to assess the uniformity of the binder produced or for other related purposes.

As the spindle turns in the A-R or other high viscosity binder, it has a tendency to “drill” into the sample (i.e., for A-R, the spindle spins the rubber particles out of the measurement area). Consequently, the apparent viscosity drops to reflect only the liquid phase of the high viscosity binder. Therefore, the peak viscosity measurement value is recorded to reflect the viscosity of the blended material.

1.1 The use of high viscosity asphalt binders like Asphalt-Rubber is becoming more common in the United States and worldwide. Specifications such as Specification D6114 note the need for field control of the apparent viscosity and require the use of a field production rotational viscometer. The testing of Asphalt-Rubber Binder for use in Asphalt- Rubber Hot Mix and for Asphalt-Rubber Membrane is necessary to ensure consistent mix properties that will ensure good performance of these materials. Logistics of field applications limits the use of conventional laboratory controls and testing equipment. This test, using a hand held rotational viscometer can be conducted in either the field or laboratory to determine the apparent viscosity of Asphalt-Rubber and other high viscosity binders for field production control and to assess the uniformity of the binder produced or for other related purposes.

1.2 Asphalt-Rubber Binder consists of a blend of paving grade asphalt cement and crumb rubber as described in Specification D6114. Other high viscosity asphalt binders may consist of asphalts modified with polymer or fiber or both. Testing is performed following the specified reaction time, if any, within the production process. Control of the raw materials is separate from the test.

1.3 The values stated in SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; each system shall be used independently of the other. Combining values from the two systems may result in non-compliance with the standard.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.