AS 1141.42:2017 pdf free.Methods for sampling and testing aggregates Method 42: Pendulum friction test.
5.2 Conditioning new rubber sliders
Condition two new rubber sliders on the day of the test as follows:
NOTE: Two sliders are used in a test run to even out the effects of wear on a slider during a run and to facilitate differentiation between a faulty slider and a defective instrument.
Each slider is reversible and has two edges which can be conditioned for use; both edges may be used but not for the same test run and each edge is used on only one test run.
To commission new apparatus, including new sliders, it is desirable to have access to specimens already polished, tested and validated including a set of friction tester control specimens of known values. In the absence of these. on the very first run a polished reference specimen will be required to act as a conditioning specimen and this should not be soaked after polishing. Also in this case, if the specimen mean value (Vc) after the run for the conditioning specimen is below 48 or the value for the reference specimen or specimens is not within the expected range (see Appendix A). it is necessary to discard the two sliders and all test specimens from the run and begin again with fresh materials. A set of friction tester control specimens should be prepared and evaluated as soon as possible after commissioning the friction tester.
(a) Position an unsoaked, air-dried conditioning specimen. with friction value not less than 48, in the specimen holder so that the slider will traverse the specimen in the direction of the traffic flow.
NOTE: For specimens prepared in accordance with AS 1141.40 or AS 1141.41, this is against the direction of the arrow.
(b) Secure the new slider on its pivot ensuring the correct positioning of the two washers and spring. Check that the trailing edge of the slider is parallel to the minor axis of the polished area of the specimen when the pendulum hangs freely at rest.
(c) Adjust the height of the axis of suspension of the pendulum by means of the rack and pinion so that the whole trailing edge of the slider is in contact with the polished area of the specimen for a set length while traversing the specimen. This length is set by aligning the trailing edge of the slider against the marks on the rule supplied with the friction tester. The contact length shall be as given in Table 2.
Return the pendulum to its horizontal position and move the pointer against its stop.
(d) Release the pendulum and pointer from the horizontal position, allowing them to swing over the specimen. As the pendulum falls back from its peak after the slider has traversed tile specimen. it has to be caught and the slider lifted befr’re it hits the specimen again, otherwise (lie slider will he damaged and may have to he discarded.
Return the pendulum and pointer to the horizontal position.
(e) Swing each slider to be conditioned five times along the dry surface of the conditioning specimen. Wet the surface of’ the specimen with clean water at 23 ±2°C from the water spray bottle. Then swing each slider 20 times along the wetted surface of the specimcn, rewetting the specimen before each swing.AS 1141.42 pdf download.