Crushed stone, gravel, or sand.
· Must be washed.
· Crushed aggregate is required for primary and interstate roadways and may be specified for other projects.
· Produce crushed gravel as a separate operation by crushing the gravel particles retained on a screen at least 1/4 inch larger than the aggregate size specified.
Meet aggregate gradation requirements for the gradation number specified in Table 4125.02-1. Unless specified otherwise, use the 1/2 inch sieve size.
Table 4125.02-1: Aggregate Gradation Requirements (Bituminous Sealcoat)
|
Size |
Gradation No. |
|
1/2 inch Crushed Gravel or Stone |
19 |
|
Screened Gravel |
20 |
|
3/8 inch Crushed Gravel or Stone |
21(a) |
|
Sand Cover Aggregate |
1(b) |
(a) 1/2 inch size may be used when 3/8 inch size is specified except for Primary Road applications.
(b) For a crushed stone product allow up to 4% passing the No. 200 sieve.
· Free from objectionable clay coatings that prevent emulsions from fully coating the aggregate when determined using Materials I.M. 349.
· Type 4 or better frictional classification as shown in Materials I.M. T203.
· For cover aggregate for bituminous sealcoat, meet the requirements of Table 4125.03-1:
4125.03-1: Aggregate Quality (Bituminous Sealcoat)
|
Aggregate Quality |
Maximum Percent Allowed |
Test Method |
|
Abrasion |
40 |
AASHTO T 96 |
|
C Freeze |
10 |
Iowa DOT Materials Laboratory Test Method No. 211, Method C |
|
Shale (+ No. 4 sieve) |
5.0 |
|
|
Shale (+ No. 16 sieve) (Sand cover aggregate) |
2.0 |