Table of Contents

Appendix B 5.2 Grading of Crushed Rock Base and Subbase

The grading of the crushed rock after compaction shall comply with the relevant requirements of Tables B.6, B.7, B.8 and B.9.

Table B 6: Grading requirements for Class 1 & 2, 20 mm base

AS sieve size (mm)Target grading (% Passing)Test value
Limits of grading (% Passing) Retained between Sieves %

26.5

19.0

13.2

9.5

4.75

2.36

0.425

0.075

100

100

85

73

54

39

18

9

100

95–100

78–92

63–83

44–64

30–48

14–22

7–11

0–5

7–18

10–16

14–24

10–20

14–28

6–13

Table B 7: Grading requirements for Class 3, 20 mm subbase

AS sieve size (mm)Target grading (% Passing)Test value limits of grading (% Passing)
26.5 100 100
19.0 100 95–100
13.2 85 75–95
9.5 75 60–90
4.75 59 42–76
2.36 44 28–60
0.425 21 14–28
0.075 10 6–13

Table B 8: Grading requirements for Class 3, 40 mm subbase

AS sieve size (mm)Target grading
(% Passing)
Test value limits of grading (% Passing)
53.0 100 100
37.5 100 95-100
26.5 85 75-95
19.0 77 64-90
9.5 60 42-78
4.75 46 27-64
2.36 35 20-50
0.425 17 10-23
0.075 9 6-12

Class 4 crushed rock subbase shall comply with the relevant nominal size grading requirements given in Table B.9. The crushed rock shall not be graded from near the coarse limit on one sieve to near the fine limit on the following sieve or vice versa.

Table B 9: Grading requirements for Class 4 subbase

AS Sieve Size (mm)Test Value Limits of Grading (% Passing)
Nominal Size (mm)
50 40 30 25 20 14 10
75.0 100       
53.0   100      
37.5    100 100    
26.5      100   
19.0 54-75 64-90     100 100
9.5    48-70 54-75    
4.75      42-76 54-75 64-84
2.36        
0.425 7-21 7-23 9-24 10-26 10-28 15-32 18-35
0.075 2-10 2-12 2-12 2-13 2-14 6-17 7-18