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Accelerated Polishing Machine

The Cooper Accelerated Polishing Machine is the industry standard device for the determination of the Polished Stone Value PSV.

Accelerated Polishing Machine CRT-APM was first manufactured over 30 years ago. In the 1950’s increased traffic flow and higher speeds, together with concerns about road safety led to research into the relationship between road materials and skid-resistance. Research at the UK Transport Road Research Laboratory showed a significant relationship between polishing of aggregates used in road surfaces and skid resistance. Tests were devised using an Accelerated Polishing Machine and a friction measuring device, known as the Pendulum Skid Tester (also manufactured by Cooper), to determine a Polished Stone Value (PSV).
Fourteen specimen aggregate samples are clamped around a rotating road wheel. These samples are subjected to two timed stages of abrasive polishing under a loaded rubber tyre. First by Corn Emery grit, and secondly by Flour Emery powder.
With the best quality as market leaders, Cooper have recently been copied by low quality manufacturers. Imitators’ machines may look similar, but precision, repeatability and reproducibility come only with years of experience.



EN 1097-8:2009 (formerly BS 812 pt114: 1989)
ASTM E303-93
ASTM D3319-99


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  • Pendulum Skid Resistance Tester