Summary of Rubber Modified Asphalt Product Specifications around ...

New Jersey, and Massachusetts DOTs specified higher temperatures when adding CRM into the
base asphalt cement. California is at the higher end with a specification of 190 -226 o C (375-
440 o F) when CRM is added and 190-218 o C (375-425 o F) when blending. Ontario’s blending
temperature 180 o C (356 o F) is similar to that of Arizona and is in the middle of all agencies in
the Table 2.
Blending time is also a big factor affecting final uniform formation of rubberized asphalt cement.
The field blend viscosity, normally measured by a Haake viscometer, increases at the beginning
of the blending process, reaches a peak value, and then starts to drop or remain constant with
longer blending times. This procedure is called asphalt rubber design profile and is required by
California. Ontario doesn’t require an asphalt rubber design profile. It requires a minimum of 45
minutes of blending time and requires field blend viscosity of 1500 – 4000 cP.
The common tests specified for rubberized asphalt cement are field blend rotational viscosity,
cone penetration, resilience, and softening point.
Table 2. Comparison of Rubberized Asphalt Cement from Various Agencies
Agency CRM
percentage
Ontario,
Canada
Blending
temperature
18-20% 180 o C
(356 o F)
California 20 ± 2%;
for CR,
75% scrap
tire CR and
25% high
natural CR.
190 -226 o C
(375-440 o F)
when CRM
is added.
190-218 o C
(375-425 o F)
when
blending.
Blending
time
45
minutes
45
minutes
min.
Field blend
viscosity, cP,
and other tests
1500-4000
using California
LP-11;
Penetration 25-
70
Resilience 18%
min;
Softening point,
52-74 o C (125-
165F)
1500-4000
using California
LP-11;
Penetration 25-
70
Resilience 18%
min;
Softening point,
52-74 o C (125 -
165F)
Others
CRM gradation,
mixing method,
dosage, reaction
time, storage
condition, etc. shall
be determined by
contractor. Make
sure anti-stripping
agent is compatible
with the RMA mix
and RAC.
Asphalt modifier
should be added to
the binder at 2.5 to
6% of paving
asphalt. The asphalt
modifier shall be a
resinous, high flash
point, aromatic
hydrocarbon
compound.
Maximum of 2
reheat cycles.
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