Viskomat NT, Mortar, Cement and Fine Concrete Rheometer

• Robust apparatus for industrial environments
• Quality control, research and development
• Informative, easy to use test procedures
• Automatic running of predefined test procedures which can be either standardized or tailored to your own requirements
• Inhomogeneous materials measurable with particles up to 2 mm using special paddles to avoid separation

Construction and Operating Principle

The Viskomat NT is a true speed-controlled viscometer driven by a high precision syn. Chron. motor. Each rotation is resolved within 200.000 steps. It allows ramping from 0.001 rpm to 400 rpm in both directions to record flow curves and yield points. The torque up to ±250 Nmm is measured by a special transducer.

The standard measuring system consists of a stationary probe which is mounted concentrically in a rotating cylindrical sample container. As the sample flows around the paddle the shear resistance generates a torque which is continuously monitored electronically. The paddle is mounted on a measuring head, which runs up and down automatically to allow easy filling, emptying and cleaning of the sample container. The sample container is mounted on a speed drive shaft. The temperature is measured by a sensor located within the measuring paddles.

All the electronic is housed in a separate case. One powerful microprocessor and two special signal processors do their work there. An online display shows torque, time and temperature during the measurement in a graphical way. The electronic has an ethernet interface to any PC. With the Ethernet interface you can integrate the Viskomat NT in any TCP/IP based (100 Mbit, RJ45) network. The Viskomat NT has a built in WWW Server so any WEB browser may be used as user interface. The Viskomat NT can be directly operated by the PC (Linux) included, or remote controlled from any Windows (95 or higher) workplace in your local area network.

Measurement Modes

• Speed controlled
• The torque over a defined speed profile is measured
• Torque controlled
• The speed over a defined torque profile is measured
• Angle controlled
• The torque over a defined angle profile is measured
• Oscillation mode f
• The torque over defined frequency profile at a constant amplitude is measured
• Oscillation mode a
• The torque over defined amplitude profile at a constant frequency is measured

Probes

The Viskomat NT is delivered with two standard probes for mortar and cement paste. Additional you can get a cylinder-cylinder probe according to EN ISO 3219 (volume 127 ml, gap size 2.1mm) and a cone plate-probe (angle 15°, diameter 100mm). See below for further information on the unique basket probe offered with the Viskomat NT.

Basket Probe for the Viskomat NT

It is well known that standard probes for rheometers like cylinder-cylinder system doesn't work well for building materials like mortars and pastes. Due to the segregation of the coarse and the liquid phase the so-called wall slippage may occur. This may be reduced by rough or ripped surfaces of the probes. Another suggestion is to replace the adhesion forces between the wall and the-material by cohesion effects between the material itself. A shearing two layers of material may be approximated if you build up a layer of material with a filigree structure of meshes.

Design of the Probe

Based on the operation principle a known double ring-gap probe is enhanced by a special designed inner cylinder. Its not a rigid but structured like a basket.

Prerequisite for using this probe is a stable fluid like:

• SCC, SLU or injection mortars
• Powder suspensions, coatings etc.
• Liquids like methyl cellulose