Penetrometer and CBR Values
Table 1: Field CBR Estimated from Scala Penetrometer
(Table From Country Roads Board)
Penetration In Millimetres Estimated Field CBR
less than…
1 blow 2 blows 4 blows 8 blows
5
50 + 50 + 50 + 50 +
6
50 50 + 50 + 50 +
  32 50 + 50 + 50 +
10
22 50 50 + 50 +
  18 39 50 + 50 +
15
14 32 50 + 50 +
  12 26 50 + 50 +
20
10 22 50 50 +
  9 20 45 50 +
25
8 18 40 50 +
  7 16 36 50 +
30
6 14 32 50 +
  6 13 29 50 +
35
5 12 26 50 +
  5 11 24 50
40
4.5 10 22 50
  4.5 10 21 47
45
4 9 20 45
  4 9 19 43
50
3.5 8 18 40
  3.5 8 17 38
55
3.5 7 16 36
  3      
60
3      
  2.5      
65 - 70
2.5      
75 - 100
2      
100 - 160
1.5