Polished stone value test

This test is conducted on coarse aggregates that are used for surfacing mixes. The PSV test determines the resistance of the coarse aggregate to the polishing action of vehicle tyres. The test consists of two parts in the first part, test specimens are subjected to a polishing action in an accelerated polishing machine. In the second part of the test, the state of polish reached by each specimen is measured using the Pendulum tester apparatus. The PSV is then calculated from the friction determinations. 

The test is carried out in accordance with CEN EN 1097-8 (2009) or with ASTM D 3319 (2011) (AASHTO T 279 2012). The key differences between the two standards are the nominal size of aggregate used, the polishing medium used, the number and the type of test wheels, the way the aggregates are subjected to polishing and the way the PSV index is 

Approximately 36 to 46 aggregate particles of size 7.2/10 mm are carefully placed in a single layer in a mould with their flattest surface lying on the bottom. The interstices between the aggregates are filled with fine sand. The quantity of sand used is such that only three quarters of the depth of the interstices is filled. Then, the mould is in-filled with an epoxy resin and any surplus is removed with a spatula. After the resin has hardened, the specimen is cleaned thoroughly to remove any sand and is transferred to the polishing machine. 

After the first 3 h, the second rubber-tyred wheel is fitted and the test is repeated for another 3 h using flour emery. The emery flour rate is 3 1 g/min with the rate of water approximately twice that of the emery flour. 

The determination of PSV is considered necessary for determining the suitability of aggregate for any type of surfacing asphalt and surface dressing. Aggregates are considered to be suitable when their PSV is greater than or equal to the value given by the national specification. These values are related to traffic level and the type of site. 

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Other mechanical test procedures are given in BS 812, namely the aggregate crushing value, aggregate abrasion value and the polished stone value. Other tests are widely used, such as the Los Angeles test for impact resistance [8.6]. 

Polished stone value (PSV) is the resistance of an aggregate to polishing, using the accelerated polishing test in BS 812. High values indicate increased resistance to polishing. 

CEN EN 1097-8.2009. Tests for mechanical and physical properties of aggregates - Part 8 Determination of the polished stone value. Brussels CEN. 

Other geometrical and physical tests on the aggregates of the RA (angularity, resistance to fragmentation, resistance to polishing polished stone value [PSV], resistance to surface abrasion aggregate abrasion value [AAV], particle density, water absorption, etc.) may also be necessary to be determined when comprehensive mix design is followed. 

The Mohs hardness test (the word scratch is assumed) is almost a nondestructive test. The hardness of a gemstone is usually referred to as its Mohs hardness. Since this hardness value is determined by a scratch test, it is not actually a hardness. The scale has many drawbacks including the fact that it is not linear, it does not necessarily relate to wear resistance, and it damages the specimen so it is not ideal for polished stones. 

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