Use of RAP in Asphalt Mixtures

2 Outline Why Recycle? Economics of HMA Recycling Current Practices for Using RAP Sources and Processing of RAP Sampling & Testing RAP Using RAP in Mix Designs Resources

3 Use of RAP in Asphalt Mixtures Hot-Mix Asphalt (HMA) Recycling Hot-Mix Asphalt Plant Milling an Asphalt Pavement Reclaimed Asphalt Pavement (RAP)

4 Use of RAP in Asphalt Mixtures Why Recycle Asphalt? Pavement Benefits Economic Payoff Energy Savings Natural Resource Conservation Milling (Cold Planing) of an Asphalt Pavement

5 Use of RAP in Asphalt Mixtures Benefits of Milling Removes cracked and aged pavement layers Improves pavement smoothness and cross-slopes Maintains curb heights, drainage inlets, and bridge clearances Creates a rough texture that bonds better with the overlay

6 Use of RAP in Asphalt Mixtures Economics of HMA Recycling

7 Use of RAP in Asphalt Mixtures Materials savings will depend on... Virgin binder cost Asphalt content of the mix design Aggregate cost RAP cost Asphalt content of the RAP Percentage of RAP

8 Use of RAP in Asphalt Mixtures Recycling Economics Example Aggregate: $10.00/ton Asphalt: $500.00/ton Mix Design AC Content: 5.0% $10 x.95 = $ 9.50 $500 x.05 = $25.00 Total Mix $34.50

9 Use of RAP in Asphalt Mixtures Monthly Asphalt Binder Prices

10 Use of RAP in Asphalt Mixtures Recycling Economics Example Aggregate: $10.00/ton Asphalt: $500.00/ton RAP: $6.00/ton (5% AC in RAP) Mix Design AC Content: 5.0% RAP content 20% (19% rock, 1% AC) $10.00 x.76 = $ 7.60 $ x.04 = $20.00 $6.00 x.20 = $ 1.20 Total Mix $28.80

11 Use of RAP in Asphalt Mixtures Recycling Economics Example Virgin Mix: $34.50/ton Recycled Mix: RAP: Savings = 16.5%

12 Use of RAP in Asphalt Mixtures

13 Use of RAP in Asphalt Mixtures Energy Consumption Related to Road Construction and Maint. MJ/tonne Source: The Environmental Road of the Future, Life Cycle Cost Analysis, Chappat and Bilal, Colas Group 2003, p.34

14 Use of RAP in Asphalt Mixtures Current Practices for HMA Recycling

15 Use of RAP in Asphalt Mixtures Surface Mixes: % RAP Allowed

16 Use of RAP in Asphalt Mixtures Base Mixes: % RAP Allowed

17 Use of RAP in Asphalt Mixtures Asphalt recycling specifications and practices are inconsistent across the USA Goal to increase average RAP content to 25% by 2013 Some technical issues need to be resolved for using RAP contents above 25% Some perceptions exist that recycled HMA is inferior to all virgin HMA, which stifles the effort to increase recycling. Asphalt Recycling in the USA

18 Use of RAP in Asphalt Mixtures Milling for Success The primary goal for milling is to remove distressed pavement layers and restore a good profile for the overlay. Prior to milling, obtain cores to help decide the milling depth. Avoid leaving damaged layers or thin layers that are likely to scab. Mill so that the RAP is not contaminated with soils.

19 Use of RAP in Asphalt Mixtures Ownership of Millings Some highway agencies take ownership of RAP on rehab projects and use the RAP for maintenance applications such as shoulder build up or in equipment yards or driveways. These applications do not utilize the full value of RAP The best value of RAP can be achieved when to contractor owns the reclaimed material In a low-bid competitive environment, HMA producers generally will use RAP in its best economic application

20 Use of RAP in Asphalt Mixtures Agency Requirements on RAP Sources Some agencies only allow RAP obtained from their projects to be used in the mixes for their projects. This restriction hinders the use of RAP to its full advantage. The quality of materials (e.g. aggregate and binder properties) in the RAP can and should be verified with routine testing as part of mix design and quality control.

21 Use of RAP in Asphalt Mixtures Principles of RAP Management Good materials management practices should always be part of the quality control program for any asphalt mix production operation As RAP contents increase, it becomes more important to accurately determine properties of RAP and control its consistency

22 Use of RAP in Asphalt Mixtures Keep millings from different projects in separate stockpiles. Milled RAP can typically be used “as is” in HMA without further crushing. Milled RAP

23 Use of RAP in Asphalt Mixtures Multi-Source RAP Multisource piles can be an agglomeration of materials from milled projects, pavement rubble, rejected mix, and plant waste. It should be obvious, but unprocessed multi- source RAP stockpiles are not suitable for use in new mixes.

24 Use of RAP in Asphalt Mixtures RAP Processing Tips Avoid contamination from the beginning Mix RAP from different sources going into the screen or crusher Don’t over crush because it will generate excess fines and result in more uncoated particles Fractionation helps for design of high RAP mixes Watch the weather when processing Blend again when moving RAP stockpiles

25 Use of RAP in Asphalt Mixtures Multi-Source RAP Stockpiles Prevent dumping of any deleterious materials in the multi-source pile from the beginning. Instruct all truck drivers hauling materials to the yard where to dump different types of materials Use of RAP in Asphalt Mixtures

26 Use of RAP in Asphalt Mixtures Avoid Contamination It is vital to prevent dumping of any deleterious materials in the pile from the beginning. Clearly instruct all truck drivers hauling materials to the yard where to dump different types of materials Use of RAP in Asphalt Mixtures

27 Use of RAP in Asphalt Mixtures RAP Crushing Process Small dozer to break up RAP and push it to a loader Mix the multiple source material while feeding it into the Processing Unit Use of RAP in Asphalt Mixtures

28 Use of RAP in Asphalt Mixtures Over Crushed RAP

29 Use of RAP in Asphalt Mixtures Cool weather helps minimize caking of RAP in crushers and blinding of screens which will alter the gradation and asphalt content Weather Free moisture in the RAP can cause the same problems

30 Use of RAP in Asphalt Mixtures Variability of RAP 1. Is RAP more variable than virgin aggregates? 2. Does fractionation reduce the variability of RAP stockpiles? 3. Is single source RAP more consistent than processed RAP from multiple sources? All are NO!

31 Use of RAP in Asphalt Mixtures ICAR-401-1/98 Based on stockpiles at contractors plant site… Analysis of variance on the median coefficient of variation revealed that RAP had a lower variation than virgin aggregates The statistical analysis revealed that increasing the percentage of RAP does not increase the coefficient of variation of the mix. (This is in the RAP range of 15 to 40% and most of the mixes had between percent RAP).

32 Use of RAP in Asphalt Mixtures More Information on RAP Variability Statistics NCAT gathered data from 20 contractors across the U.S. Received data for over 130 stockpiles Compiled data for fractionated RAP, non- fractionated RAP, and aggregate stockpiles Calculated the standard deviations for key properties for each stockpile Data for stockpiles with less than 10 samples were not used

33 Use of RAP in Asphalt Mixtures Variability: RAP vs. Aggregate Based on 74 RAP stockpiles in 14 states, and 60 Aggregate stockpiles in 6 states

34 Use of RAP in Asphalt Mixtures Fractionated RAP -3/16” RAP +3/4” RAP 3/4 x 3/16” RAP In back Screening RAP into two or more sizes A huge advantage for mix design. Allows RAP to be used in practically any mix type

35 Use of RAP in Asphalt Mixtures

36 Use of RAP in Asphalt Mixtures Gradations and Asphalt Contents for Fractionated RAP Samples Example Data

37 Use of RAP in Asphalt Mixtures Fractionating RAP However, the practice should not be mandated; it should be the contractor’s business decision if and when to fractionate RAP.

38 Use of RAP in Asphalt Mixtures Fractionated vs. Unfractionated

39 Use of RAP in Asphalt Mixtures Stockpiling RAP Building steep sided stockpiles will create segregation within the pile

40 Use of RAP in Asphalt Mixtures Stockpiling RAP Minimize Moisture in RAP Covered Stockpiles Sloped Pavement Underneath

41 Use of RAP in Asphalt Mixtures Effect of RAP Moisture on Superheating Temperature

42 Use of RAP in Asphalt Mixtures Sampling RAP The goal of sampling RAP is to obtain representative samples for evaluating materials properties. Samples are needed from throughout the stockpile to assess variability. A minimum sampling frequency of 1 per 1000 tons with a minimum of 10 samples is recommended.

43 Use of RAP in Asphalt Mixtures Sampling RAP The best method to sample RAP is to use a loader to create flat-topped miniature stockpiles A good time to sample is when a stockpile is being built at its final location Do not combine samples from different parts of the stockpile. Tests need to be performed on individual samples to assess uniformity.

44 Use of RAP in Asphalt Mixtures Photo courtesy of Tim Murphy

45 Use of RAP in Asphalt Mixtures Photo courtesy of Tim Murphy

46 Use of RAP in Asphalt Mixtures Photo courtesy of Tim Murphy

47 Use of RAP in Asphalt Mixtures Photo courtesy of Tim Murphy

48 Use of RAP in Asphalt Mixtures Testing RAP General properties:  asphalt content  aggregate gradation  aggregate bulk specific gravity  fine aggregate angularity  fractured face count  flat & elongated percentage  deleterious materials

49 Use of RAP in Asphalt Mixtures Testing RAP Asphalt Content: ignition method is preferred. An aggregate correction factor must be assumed. For regions that utilize dolomite aggregates that have erratic correction factors, a solvent extraction method is recommended.

50 Use of RAP in Asphalt Mixtures Testing RAP Aggregate bulk specific gravity: estimated from a three step process 1. Determine Gmm (w/ dryback) of RAP sample 2. Calculate Gse using the Gmm from step 1 and the asphalt content from the ignition method (or extraction test if ignition method is not reliable)

51 Use of RAP in Asphalt Mixtures Testing RAP 3. Estimate Gsb from Gse using a typical offset value or regression from historical mix designs with the aggregates in the region

52 Use of RAP in Asphalt Mixtures Testing RAP Other RAP aggregate properties – tests can be performed on aggregate recovered from the ignition oven. Gradations Fine aggregate angularity F&E Fractured faces LA Abrasion Sulfate soundness

53 Use of RAP in Asphalt Mixtures RAP Sampling & Testing Flowchart At least 10 samples when building stockpile asphalt contents gradations Max. specific gravities Split each sample Ignition method tests Combine samples for other aggregate tests Gse → Gsb

54 Use of RAP in Asphalt Mixtures Summary & Analysis of RAP Data Calculate average and standard deviation of asphalt contents, gradations, and estimated Gsb Compare to these recommended tolerances: RAP property Max. Standard Deviation (%) Asphalt Content0.5 % Passing Median Sieve5.0 % Passing 75 micron Sieve1.0

55 Use of RAP in Asphalt Mixtures Current Superpave Guidelines for Selecting the Virgin Binder Grade Tier 1: Up to 15% RAP use the normal binder grade Tier 2: 15%-25% RAP use one binder grade lower, e.g., PG instead of PG Tier 3: Over 25% RAP use blending charts to determine required binder grade Binder

56 Use of RAP in Asphalt Mixtures RAP Nomograph- High PG Temp.

57 Use of RAP in Asphalt Mixtures High RAP (>25%) Guidelines Additional guidelines for High RAP content mix designs are under development RAP Management Best Practices Revised recommendations on selecting the appropriate grade of virgin binder Additional mixture tests to ensure pavement durability

58 Use of RAP in Asphalt Mixtures Producing HMA with RAP

59 Use of RAP in Asphalt Mixtures Screening to Remove Oversized RAP Particles

60 Use of RAP in Asphalt Mixtures Test samples before and after the “crusher” to determine if gradation is changed In-Line Crushing of RAP

61 Use of RAP in Asphalt Mixtures Parallel Flow Drum with RAP Center Entry This plant design is likely to have pollution problems when using high RAP contents

62 Use of RAP in Asphalt Mixtures HMA Recycling Already a successful standard practice Economics has been the primary driver The goal of RAP management is to develop stockpiles with consistent properties Summary

63 Use of RAP in Asphalt Mixtures Resources Basic Asphalt Recycling Manual, Asphalt Recycling and Reclaiming Association, PUB: NHI01-022, 2001 Recommended Use of Reclaimed Asphalt Pavement in the Superpave Mix Design Method: Technician’s Manual, NCHRP Report 452 Recycling Hot-Mix Asphalt Pavements, Information Series 123, National Asphalt Pavement Association