Resistance to permanent deformation is the best known and most recognizable feature of courses made from SMA mixtures. This resistance has its origins in the very strong skeleton of coarse particles of an aggregate mix. This issue was already thoroughly deliberated in Chapters 2, 3, and 6, therefore only some additional information about testing that feature is provided below.
A Comparison of Essential Functional Properties of Some Popular Asphalt Mixtures for Wearing courses
|
preferred Functional |
Required Fundamental mix |
Typical values of various surfacing Types 0/13 mm size |
|||
|
properties |
properties |
oca |
UTFC |
SMA |
cca |
|
High skid |
High surface |
2-3 mm |
1.5-3 mm |
1-2 mm |
0.2-0.5 |
|
resistance |
texture High |
18-25% |
12-20% |
0% |
mm 0% |
|
interconnected internal voids High aggregate |
Aggregate |
Aggregate |
Aggregate |
Aggregate |
|
|
polishing |
dependent |
dependent |
dependent |
dependent |
|
|
Low tire-road |
resistance Negative texture |
Yes |
Yes |
Partially |
No |
|
noise Low spray |
Macrotexture |
2-3 mm |
1.5-3 mm |
1-2 mm |
0.2-0.5 |
|
generation Low construction |
Low layer |
30-40 mm |
18-20 mm |
30-40 mm |
mm 30-40 mm |
|
and maintenance |
thickness High durability |
Medium- |
Medium- |
High |
High |
|
cost and construction delays and |
(low maintenance cost) Long functional |
high 8-12 years |
high 8-12 years |
10-12 |
Lowa |
|
vehicle damage |
life Early trafficking |
Yes |
Yes |
years Yes |
Yes |
|
Low windscreen |
Low |
Low |
None |
None |
|
breakages |
Source: From Pretorius F. J., Wise J. C., and Henderson M., Proceedings of the 8th Conference on Asphalt Pavements for Southern Africa (CAPSA’04), 12-16 September 2004.
Note: CGA = Continuous graded asphalt; OGA = open graded asphalt; SMA = stone matrix asphalt;
UTFC = ultra-thin friction courses.
a Functional life is low or non-existing relative to spray reduction and wet weather friction.
