Aggregate 'Ten Percent Fine Value' (TPFV):

The other way of representing the strength of aggregate is the 'ten percent fine value' (TPFV), that is basically the load needed for 10% fines. As compared to aggregate crushing value test this test is more reliable for representing the strength of aggregate. To determine the 'ten percent fine value' the aggregate sample is prepared in the same manner as in the case of determining the aggregate crushing value. A prepared aggregate sample (weighing 'A') is placed in the test apparatus and the load is applied uniformly through a plunger at uniform rate so as to cause total penetrations in 10 minutes as below:

• 15.00 mm for rounded or partially rounded aggregates.
• 20.00 mm for normal crushed aggregates.
• 24.00 mm for honeycombed aggregates (e.g. expanded shale and slag).

After achieving the desired penetration the load is removed and the aggregate is taken out and sieved by 2.36 mm sieve. The weight 'B' of the fraction passing by 2.36 mm is taken. The load applied should be such that the percentage of fines [i.e. (B/A) × 100] be in the range of 7.5-12.5% otherwise the test is repeated with another load. Two such tests are conducted and the load required for ten percent fines [TPFV] is obtained by:

TPFV = 14 × X/Y + 4

where,            X = Load in tons causing 7.5-12.5 % fines, and

Y = Mean percentage fines from two tests at X tons load.