Transcript Warm Mix Asphalt - Purdue University

“Warm Mix Asphalt”
Indiana Experience with
Water Injected Foaming Device
Rick Flint
Chemical Additive WMA
Objectives
• Decrease fuel usage, by lowering mixing
temperature
• Decrease emissions at plant
• Decrease fumes at paver
• Decrease or eliminate tenderness zone
• Improve mat compaction and density
• Improve joint density
• Improve conditions for crew with less heat and
less fumes
WMA ?
• WMA nationally and internationally refers to
the usage of chemical additives to
accomplish a desired workability of Hot Mix
Asphalt at lower temperature.
• Water injection foaming device accomplishes
all WMA objectives, and at less cost than
using additives.
• INDOT 2008 Standard Specifications neither
addressed nor prohibited the water injection
method through the plants.
Water Injected Foamed Asphalt
• Water is injected into the Hot Liquid PG Binder at the
rate of approximately 2% of the virgin Binder = 2lbs /
ton of mix = 0.1% / ton of mix prior to entering the
mixing chamber. (These numbers are based on a
virgin mix with 5.0% binder content.)
• The result is a liquid binder which is foamed prior to
entering the mixing chamber, creating a lower
viscosity fluid due to the presence of microscopic
steam bubbles that remain in the mix until it is
compacted.
• Many times, rolling can begin immediately and
compaction can be achieved with less rolling.
• Once the mix is compacted, the residual moisture is
only 0.0012%, which is not even measureable by our
standards.
INDOT 2008 Specifications
• Section 401.02 (ITM 583) – Plant
specifications did not prohibit modification of
plant by adding manifold or device that
injected water into the liquid asphalt.
• Section 902.03, Note 1 – Defined plant mix
temperature for PG Grades in accordance
with PG Supplier recommendation.
INDOT 2008 Specifications
• INDOT Office of Materials Management
agreed that interpretation of specifications
allowed water injection.
• OMM requested notification of jobs when
used.
• OMM had little concern due to historical
experience with emulsified asphalt.
J. H. Rudolph & Co. Inc.
Experience 2008
• Summer 2008 - JHR determined the water injection
foaming method would;
a) be economical,
b) meet INDOT specification and,
c) meet WMA objectives.
• August 2008 – JHR Installed the ASTEC Green System
water injection manifold system on St. Croix Plant.
ASTEC Green Water Injection Manifold
J. H. Rudolph & Co. Inc.
Experience 2008
• Private and local government Water Foamed
Asphalt work successfully accomplished by JHR
crews and a supplied laydown contractor.
Tell City Greenway Path, Perry Co., Ind.
SR 245, Spencer Co., Ind.
JHR Experience 2008
• R-28507 – US 231, Spencer County
• INDOT Division of Materials Management notified
of WMA water injection method intent.
• Mix successfully produced and placed.
• FHWA visited job, learned of WMA being placed
and stopped placement without determination of
WMA method or regard to INDOT Specs.
SR 231, Spencer Co., Ind.
SR 231, Spencer Co., Ind.
INDOT 2008 Specs Revised
• INDOT – APAI Joint Technical Committee
along with FHWA met to arrive at a solution
to the impasse created by FHWA.
• Specs revised to explicitly allow WMA water
injection for all mixes less than 10M ESALS.
• Additional Sampling required for WMA. This
consisted of 1 moisture per each sublot of
first lot of WMA and 1 moisture per lot
thereafter.
• Applied to 2008 and 2009 work.
INDOT Current Specifications
(Copied from Recurring Special Provisions)
400-R-553 HMA PROVISIONS
(Revised 02-21-11)
The Standard Specifications are revised as follows:
SECTION 401, BEGIN LINE 46, INSERT AS FOLLOWS:
ESAL CATEGORY
ESAL
1
< 300,000
2
300,000 to < 3,000,000
3
3,000,000 to < 10,000,000
4
10,000,000 to < 30,000,000
5
≥ 30,000,000
QC/QA HMA may be produced as warm-mix asphalt, WMA, by using a water injection
foaming device for ESAL category 1, 2 and 3 mixtures. The DMF shall list the
minimum plant discharge temperature for HMA and WMA as applicable to the mixture.
INDOT Current Specifications
Regarding RAP and RAS
Specifications are now based on percent of total
Binder Replacement (BR)from RAP and or RAS
rather than the previous method of percent RAP
or RAS used by weight of mix.
Base and Intermediate mixes are now allowed up
to 25% Binder replacement before switching
from specified PG Binder grade.
Surface mixtures are now allowed up to 25% BR
for ESAL 1 & 2, and 15% BR for ESAL 3,4 & 5
before switching from specified PG Binder grade.
JHR Experience 2009 & 2010
• Water Injection Foaming continues to be a success.
Used on all Base and Intermediate mixes and all
ESAL 1,2 and 3 Surface mixes.
• Mixing mixtures @ 270 – 280 F for RAP or RAS
mixtures. Mixing temperatures @ 250 F for virgin
mixes.
• Use RAP and Shingles in Water Foamed Mixes in
accordance with INDOT HMA specifications.
• Mix designs are unaffected by Water Injection
Foaming because only 0.0012% water remains in
final product.
• Use water injector even in certain HMA applications
for the benefits it provides.