This new developed fully automatic device is made as a laboratory testing device for skid resistance prediction and polishing resistanceof asphalt, concrete and aggregates by Wehner/Schulze method according to EN 12697-49：2014.

This method of the test has the ability to test large samples which can be obtained directly from the actual road, or compacted samples from mixed materials or plate single aggregates which these both types are manufactured in laboratory to simulate the polishing action of vehicles on road surface.

In accordance to many years of research work in different Universities and material testing institutes a new FAP (Friction after polishing)device is developed, which includes the conclusions of experiences and testing results.

This new device stays loyal to the originaltechnical measuring concept, but our engineersmodernized and optimized the mechanical and electronic parts of the components and also made easier handling of the system according to international technical requirements and industrial standards. Also, we looked to a news oftware solution as well.

Controlling / Electronic Station

High quality industrial controller with touchpanel and graphic display for simultaneousmonitoring of measured values and testprocedures is located in Electronic cabinet. Allelectronic parts and relays of device are mountedhere.

Operator is able to control of the entire devicevia touch panel Display (including the input ofthe basic parameters, Calibration data, languageand help settings). The Graphical and easy-tounderstand menu navigation is an advantage ofusing the deice. The Data exports via Ethernetinterface (ASCII Format) to the pc as an optionalevaluation software is also available.

The controller has 16-bit resolution for allmeasured and controlled variables and is 5 measurements can be saved internally (via thesoftware).In the lower part of the electronic station andin the same cabinet, there is an incorporatedcontainer and pump for quartz flour/watertreatment.

This quartz flour/water would be continuouslyadded during polishing process that is simulatingtraffic by using rubber rollers which polish theslab surface.

There is an emergency stop button, an indicatorand on/off switch on the door of cabinet for easyhandling of the system.

Accelerated Polishing Head

At the polishing workstation (on the left sideof main unit), a core specimen with 225 mmdiameter or rectangular sample of 320mm by260mm is held in a mould on a round base andattached firmly to the mounting table under thepolishing rollers in the machine so that the tableand specimen surfaces are  parallel. 

The polishing operation is fully automatic,and the operator has to set test parameterse.g.: Number and speed of revolutions and thepolishing quartz flour/water temperature.

Then the device starts to simulate the acceleratedvehicle impact on sample by three rubber conicalrollers. Rubber cones are lowered to contact thesurface of sample and rolling over the specimensurface during the polishing process per asrelevant standard.

The rotation frequency of rollers is 500 rotationsper minute (giving a linear speed 17 km/h) instandard version. The pressure between the rollerand the sample is 0.4 N/mm2 (tyres pressure forpassenger cars is about 0.25 N/mm2). 

A suspension fluid consisting of about 5% quartzpowder in 95% tap water is mixed at a controlledtemperature of 200C in a separate tank and issupplied through the center of the polishing headto the surface with a pumping rate of 5 l/min. topolish the sample surface during the test.

At the whole process of testing ,thepolishing parts and sample is surrounded by apolycarbonate shield.When the polishing process is completed, thesample is washed with tap water to remove

all traces of abrasive before starting of next stepwhich is the stage of measurement of the friction.

The mounting table automatically slidesbetween polishing station and the friction testingstation by a pneumatic actuator very smoothly.

Friction Meaxurement Head

The friction measurement head is equipped withthree small rubber slider pads attached to a rotatinghead and a system for measuring the momentumduring breaking. The mounted specimen ismoved and locked into position under the frictionmeasurement head and a polycarbonate shield islowered around the specimen.

The measuring head is accelerated until to reacha speed of 2700 rpm (90 km/h) and at this momentwater at 10C degree is sprayed on to the specimento give a theoretical water film thickness of 0.5mm. 

When the measuring head reaches a rotationof 3000rpm, which is equivalent to speed of100km/h, the motor turns off and the head is dropped and pressed to the specimen surface.The contact pressure being 0.2 N/mm2 equivalentto 2bar (29psi) in tyre pressure. The rotation of themeasuring head decreases by the friction betweens liding blocks and the specimen surface up tocomplete stop.

Pure water is in jecting to surface of sampleduring this breaking phase and rotation speed isrecorded by a proximity sensor and reaction forceis continuously measured by a torque transducer.

• In both polishing and friction measurement apolycarbonate shield is surrounding the sample and testing parts.

• The sample is sliding from polishing station to Friction measuring workstation by the use of pneumatic sliding system which does not need.

The machine comes with a cooling station whichhas a high-power capacity to reduce the waitingtime of temperature controlling of water for eachtest. The whole parts of the cooling system isCorrosion-less to make a long-term working lifetime for it.

Evaporator at back of the machine would do the heat transfer to water to reach the required temperature.