Mix Selection
Mix Selection
Objectives in selecting a mix include:
1. Resistance to rutting.
- Select quality aggregates
- Specify proper gradation
- Specify proper asphalt content
2. Resistance to fatigue cracking.
- Design correct air voids and asphalt viscosity
3. Resistance to thermal cracking.
- Select appropriate asphalt binder
Mixture selection charts for 2350 and 2360 mixes are available from this site.
Click here for information on hot and cold recycled mixtures.
Mix selection
for other mixtures are given in following table.
Table 1. Design Criteria for Bituminous Pavements
|
20 year ESALS Design Lane x 106 |
Specification |
Base |
Binder/Level |
Wear |
|
< 1 and shoulders (AADT < 2,300) |
Specify |
31BBB50000 |
31BIB50000/ 31LVB50000 |
31WEA50000 |
|
Contractor’s option to supply |
Type 32 Agg. Size A, C |
Type 32 |
Type 32 |
|
|
1 – 3 (2,300 < AADT < 6,000) |
Specify |
31BBB50000 |
41BIB50055/ 41LVB50055 |
41WEA50055 |
|
Contractor’s option to supply |
Type 32 Agg. Size A, C |
Type 42 |
Type 42 |
|
|
Note: No Type 31 or Type 32 mixture shall be placed in upper 80 mm. |
||||
|
3 – 10 (6,000 < AADT < 24,000) |
Specify |
31BBB50000 |
41BIB50070/ 41LVB50070 |
41WEA50070 |
|
Contractor’s option to supply |
Type 32 Agg. Size A, C |
Type 48 |
Type 48 |
|
|
Notes: No Type 31 or Type 32 mixture shall be placed in upper 100 mm. Special requirements for Type 47/48 mixtures apply. |
||||
|
> 10 (AADT > 24,000) |
Specify |
41BBB50055 |
61BIB75100/ 61LVB75100 |
61WEA75100 |
|
Contractor’s option to supply |
Type 42 Agg. Size A |
None |
None |
|
|
Notes: No Type 41 or Type 42 mixture shall be placed in upper 100 mm. Class B carbonates allowed in non-wear provided they meet Quality Requirements of Specification 3139.2D2c, including the micron insoluble residue. |
||||
General Notes:
- All wear courses, including Type 6, shall be 40 mm thick minimum.
- Aggregate sizes specified and contractor’s options are to be used unless lift thickness precludes large aggregate or otherwise specified (e.g. Size B wear). Specify Size A when lift thickness is < 40 mm or 25 mm minimum.
Table 2. Mix Designation Example: 47BBB500070
|
Type |
Lift |
Spec. 3139 Aggregate Size |
No. of Blows |
% +4 Crush |
|
31 |
BB |
A |
50 |
000 |
|
41 |
BI |
B |
75 |
055 |
|
47 |
LV |
C |
070 |
|
|
61 |
WE |
100 |
||
|
SH |
Lift Abbreviations
BB: Base course
BI: Binder course
LV: Leveling course
WE: Wear course
SH: Shoulder course
Mix Design Requirements
Design
criteria for 2350 mix
Design Criteria for 2360 mix
Mixture design requirements for other mixtures are given in the following table. It is taken from Section 2331 of the Mn/DOT Standard Specification for Construction.
Table 3. Mixture Design Requirements*
|
(A) Mixture Type |
Compacted Lift Thickness |
(B) Spec. 3139 Aggregate Size |
(C) Marshall Stability, Newtons (pounds) |
Air Voids in Mixture (%) |
(D) |
(E) Min. Added new asphalt Percentage limits |
|
31 & 32 (Wear) |
< 40 mm (1.5 in) |
A |
3350-13350 (750-3000) |
3.0-5.0 4.0 (D) |
50 |
5.8 (31 Mix) 3.0 (32 Mix) |
|
31 & 32 (Wear) |
40 mm (1.5 in) |
A |
3350-13350 (750-3000) |
3.0-5.0 4.0 (D) |
50 |
5.8 (31 Mix) 3.0 (32 Mix) |
|
31 & 32 (Wear) |
³ 40 mm (1.5 in) |
B |
3350-13350 (750-3000) |
3.0-5.0 4.0 (D) |
50 |
5.5 (31 Mix) 3.0 (32 Mix) |
|
31 & 32 (Non-Wear) |
£ 25 mm (1.0 in) (F) |
A |
3350-13350 (750-3000) |
3.0-5.0 4.0 (D) |
50 |
5.0 (31 Mix) 2.8 (32 Mix) |
|
31 & 32 (Non-Wear) |
> 25 mm (1.0 in) |
A & B |
3350-13350 (750-3000) |
3.0-5.0 4.0 (D) |
50 |
5.0 (31 Mix) 2.8 (32 Mix) |
|
31 & 32 (Base Only) |
³ 75 mm (3.0 in) |
A, B, & C |
3350-13350 (750-3000) |
3.0-5.0 4.0 (D) |
50 |
5.0 (31 Mix) 2.8 (32 Mix) |
|
41, 42, 47 & 48 (Wear) |
All |
A |
4450-13350 (1000-3000) |
3.0-5.0 4.0 (D) |
50 |
5.8 (41 & 47 Mix) 3.0 (42 & 48 Mix) |
|
41, 42, 47 & 48 (Wear) |
(G) |
B |
4450-13350 (1000-3000) |
3.0-5.0 4.0 (D) |
50 |
5.5 (41 & 47 Mix) 3.0 (42 & 48 Mix) |
|
41, 42, 47 & 48 (Non-Wear) |
> 25 mm (1.0 in) |
A& B |
4450-13350 (1000-3000) |
3.0-5.0 4.0 (D) |
50 |
5.2 (41 & 47 Mix) 3.0 (42 & 48 Mix) |
|
41, 42, 47 & 48 (Non-Wear) |
£ 25 mm (1.0 in) (F) |
A |
4450-13350 (1000-3000) |
3.0-5.0 4.0 (D) |
50 |
5.2 (41 & 47 Mix) 3.0 (42 & 48 Mix) |
|
61 (Wear) |
All |
CS |
4450-13350 (1000-3000) |
3.0-5.0 4.0 (D) |
75 |
5.8 |
|
61 (Wear) |
All |
Blend of CS, SS, and/or TT |
4450-13350 (1000-3000) |
3.0-5.0 4.0 (D) |
75 |
5.8 |
|
61 (Wear) |
All |
TT |
4450-13350 (1000-3000) |
4.0+ |
75 |
7.5 |
|
61 (Non-Wear) |
All |
TT |
4450-13350 (1000-3000) |
4.0+ |
75 |
7.5 |
|
61 (Non-Wear) |
All |
CS or Blend of CS and TT |
4450-13350 (1000-3000) |
3.0-5.0 4.0 (D) |
75 |
5.5 |
*From Table2331-1A, Mn/DOT Standard Specifications
for Construction, 2001 Edition
General
Notes
For mix design purposes, the total asphalt content in recycled mixtures
containing salvaged asphaltic pavement shall be based on the extracted
percent asphalt content (average of three tests) of the salvaged asphaltic
aggregate (without retention factor), multiplied by the percent of salvaged
asphaltic aggregate plus the percent new asphalt added to the total recycled
mixture. In addition to complying with the minimums for added new asphalt,
Types 32, 42, and 48 mixtures shall comply with the minimum requirements
for Types 31, 41, and 47 mixtures, respectively, on a total asphalt basis
(salvaged plus added).
(A) The term "wear" applies to wearing and shoulder wearing courses. The term "non-wear" applied to base, binder and leveling courses.
(B) Where more than one Type of mix is indicated, the size is the Contractor’s option unless otherwise specified.
(C) Marshall stability and Marshall hammer blows shall comply with the given values. Values shall be adjusted based on traffic loadings as stated in the Special Provisions.
(D) To the extent permitted by the Specifications, the Department intends to design and maintain all mixtures at the indicated percentage air voids.
(E) All asphalt contents are based on the total mass of the mixture for new added asphalt.
(F) Includes designed course/lifts identified as 25 mm (1 inch) minimum.
(G) The
use of Type 41 or 47 mixture (wear and shoulder wear) with aggregate
Size B will only be allowed when specifically required in the Contract.
Binder guideline charts for all Districts are outlined in Mn/DOT Technical Memo 99-03-MRR-01.
The PG binder
grade letters utilized for Specifications 2350 and 2360 should be used
in all bituminous mixture designations, regardless of the specification
number. These letters and PG Grade are listed below.
|
Mixture Designation Letter |
Asphalt Binder Grade |
|
A |
PG 52-34 |
|
B |
PG 58-28 |
|
C |
PG 58-34 |
|
D |
PG 58-40 |
|
E |
PG 64-28 |
|
F |
PG 64-34 |
|
G |
PG 64-40 |
|
H |
PG 70-28 |
|
I |
PG 70-34 |
|
L |
PG 64-22 |
Table 5. Binder Selection Criteria for Recycled Asphalt Mixtures
|
Application |
£ 20% RAP |
> 20% RAP |
|
Overlay |
No binder grade adjustments required |
No binder grade adjustments required |
|
New Construction |
No binder grade adjustments required |
See table below |
Table 6. Binder Grade Adjustments for > 20% RAP
|
Specified Asphalt Binder Grade |
New Asphalt Binder Grade to be used with RAP |
|
PG 64-34 |
> 20% RAP not allowed |
|
PG 58-34 |
PG 52-34 |
|
PG 64-28 |
PG 64-28 |
|
PG 58-28 |
PG 52-34 |
|
PG 52-34 |
PG 52-34 |
|
All other grades |
Contact Department Bituminous Engineer |
