The slurry surfacing cohesion tester is used to determine the minimum cohesion of a slurry surfacing mix which enables the set time and trafficability time to be determined. According to EN 12274-4, torque measurements are taken on five samples of the same slurry mix at suitable intervals after casting. This gives a picture of the Cohesion Build Up in the slurry.
Historically EN 12274-4 was carried out with manual equipment with which torque was generated by hand using a torque screwdriver. The requirement of the standard is to apply a rotation of between 90° and 120° in 0.5 to 0.7 seconds. This gives not only a wide range of conditions, but also a very difficult set of conditions to achieve and monitor, and has inevitably led to results which have a high dependence on the operator. Coupled with this there is also a source of inaccuracy in the way the torque is measured. As the torque meter is placed at the rear of the through rod cylinder the friction in the seals of the actuator will oppose the rotational motion and thus an additional torque is generated which shows up in the torque reading. The friction in the seals is also likely to change as the machine ages and thus results on a nominally similar sample can be different from one day to the next.
Cooper Technology’s Slurry Surfacing Cohesion Tester – Automatic, CRT-SSCT-A eliminates operator error by fully automating the application of both the force and the rotation. It also eliminates errors due to seal friction by measuring the torque with a torque cell which is placed directly behind the rubber foot.