Aptifirst has introduced the CTPT3 Controlled Two-Point Workability Tester for fresh cement mortars and concrete mixes.
Aptifirst has introduced the CTPT3 Controlled Two-Point Workability Tester for fresh cement mortars and concrete mixes.
The instrument is designed to determine the flow properties, or "workability" of these otherwise difficult-to-measure materials and to provide useful engineering data, for example for use in computer applications modelling the casting of the fluids through spaces with a network of reinforcing bars.
The traditional test for workability is the "slump test", which involves filling a standard bucket with the test specimen, then inverting the bucket onto a solid surface, removing the bucket and measuring the distance that the resulting pile has slumped compared to the original height of the bucket.
However, although quick, this test provides little meaningful information.
The CTPT3, on the other hand, is designed to measure the flow behaviour in the manner of a rheological test.
An impeller of known geometry is rotated at a series of accurately controlled speeds in a sample of known volume, and the torque required to maintain mixing at each speed is determined by a torque transducer.
The CTPT3 incorporates a novel torque transducer designed especially for this application; it is robust, with good axial stiffness, and uses state-of-the-art, licence-free, wireless radio telemetry as a non-contacting means of transferring the torque data to a computer system.
This gives excellent resolution and high-speed data acquisition.
The torque transducer is located between the impeller and the drive gearbox, obviating the need for baseline determination, and eliminating signal drift due to gear-box warming.
The computer controls the speed of the impeller (between 0 and 120rpm), processes displays and stores the data, and allows several modes of operation; "Ramp Mode" continuously changes the speed between pre-selected start and end points, recording torque as it does so; "Staircase Mode" controls the speed at a series of pre-set speeds, and records the torque at each speed, "Constant Mode" runs the machine at a constant speed for a pre-set period of time, and "Manual Mode" allows the speed to altered manually, at will.
All data is saved in comma-separated ".csv" format, making for ease uploading into spreadsheets and other applications for further analysis, if required.
Roy Carter, of Aptifirst, observed, "The CTPT3 is an evolution of the versions of the instrument that came before, dating back to the 1970s".
"We have designed out sources of noise, so that the torque reading is taken directly from the impeller shaft".
"The instrument is designed with safety in mind, with interlocked guards, emergency stop button and a keyswitch".
"Also, it is designed with practicalities in mind, so fits through a standard doorway, and is mounted on lockable castors to faciliate transportation".
"It is a valuable tool for those wanting to characterise cement-based formulations, for quality control, for formulation development and for troubleshooting".
