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“Warm Mix Asphalt”

“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

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“Warm Mix Asphalt”

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  1. “Warm Mix Asphalt” Indiana Experience with Water Injected Foaming Device Rick Flint

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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 CATEGORYESAL 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.

  12. INDOT Current SpecificationsRegarding 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.

  13. 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.

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