COLD IN-PLACE RECYCLING (CIR) Starting with what is there i.e. in situ materials

Definitions: ARRA (Asphalt Recycling/Reclaiming Ass.) Cold In-Place Recycling (CIR) is the on-site recycling process to a typical treatment depth of 2 to 5 inches, using a train of equipment (tankers, trucks, milling machines, crushing and screening units, mixers, pavers and rollers), an additive or combination of additives (asphalt emulsion, rejuvenating agents, lime, fly ash, cement), generating and re-using 100% RAP, with the resulting recycled pavement usually opened to traffic at the end of the work day.

Definitions: continued Granite Construction Company: Cold in-place recycling is performed by milling, screening, and crushing existing asphalt pavement at the work site. We restore the crushed asphalt by blending it together with a rejuvenator (usually an emulsion) and laying the material to form new pavement. Since the process occurs as one continuous operation, cold in-place recycling is an efficient and costeffective method of revitalizing roads while recycling 100% of the existing road material.

Definition: simplified CIR is an environmentally responsible, cost effective and value added process making an interlayer from in situ asphalt paving, using appropriate emulsions, such as PASS R, and strengthening additives.

Process Particulars and/or Nuances: Substitute for HMA?...NO! NO! NO!

Process Particulars: Milling Crushing Additives Mixing Lay-down Coating Compaction

Milling: Types of milling machines down-cut & up-cut Size of RAP Miller usually pulls the train Liquid additives can be sprayed into milling chamber; cutter mandrel needs cooling water

Milling

Crushing Re-circulating crushers are common with up-cutting trains Maximum RAP size Crushing too fine may cause poor coating Modify gradation by adding virgin material

Crushing

Additives Liquid additives can be incorporated thru the milling chamber or into the pug-mill Emulsion/rejuvenators e.g. PASS R Lime or cement slurries Water Rule of Thumb 5% Total Fluids Dry additives are spread in front of train Sand, Gravel, Cement, Lime, Fly-ash, etc.

Additives

Mixing Multiple-unit trains: use twin shaft pug-mill Single-unit trains: mandrel cutter chamber Sufficient water required for coating Mixed CIR dropped out of rear of pug-mill

Mixing

Lay-Down Normal windrow paving equipment used Material can also be blade laid CIR is wet Don t Ever Heat the Screed!! CIR is not HMA Has its own behavior

Lay-Down

Coating Incomplete coating of larger RAP particles Emulsion sticks to AC matrix around RAP Exposed/Fractured Faces not well coated Can Flush/Fog Coat Surface

Coating

Compaction Many schools of thought and theories Same equipment employed as with HMA Mediums/Vehicles of Compaction HMA uses heat CIR uses water Laboratory and Field Methods 95% of Marshall?? 88% of MTD? Rolling Patterns, Test Strips, Max Obtainable

Compaction

Field Operations Control Processes Climatic Conditions Pavement Conditions Traffic Control Grade Control Opening Roadway to Traffic Payment

Climatic Conditions Ideal Hot, Dry and Breezy Avoid Rainy Weather or Threat of it CIR can be done in cool weather, but it will take longer for the material to cure out. Curing of material is effected by humidity

Pavement Conditions Free of debris not necessarily swept Repair soft, spongy, subgrade failures For extensive repair consider FDR Assure adequate & uniform width

Traffic Control CIR an in-line process need only 1 lane Going against traffic mitigates stopping and starting problems under early traffic Allow sufficient time each day to roll-out

Traffic Control

Grade Control Miller & Paver have depth/grade controls Paver also has screed and slope controls Improvements to ride will occur Can make minor cross-slope adjustments Material must balance negates grade changes

Opening to Traffic Usually traffic can occupy CIR same day Suggest opening a section at mid-day to ascertain whether it will sustain traffic May need or want to LIGHTLY Fog-Coat Allow Fog-Coat to penetrate before opening Too much Fog-coat will require light sanding Perhaps County can do fogging and sanding

Payment Most CIR is paid by the Square Yard Use different items for different depths Emulsions and additives paid by the ton Water is incidental to the work Accurate quantities & specs. yields better prices

Characterization of CIR Design Parameters: Modulus Voids Strength Characterization of Product Properties

Modulus 2008 AASHTO MEPDG uses moduli and states overlying modulus is not to exceed 3 times the underlying modulus CIR is bound but not as bound as HMA Resilient Modulus of CIR is mid-range: 200k psi. Relationship with Elastic Moduli & Stability

Voids As a design parameter could control CIR stiffness as well as porosity Voids of CIR are commonly around 12% Sufficient to maintain its modulus Offers good resistance to crack propagation Low enough to resist rutting

Strength Paving layers generally have a surrogate strength requirement: many are flexural Marshall and Hveem have strength-like test procedures but are run at HMA temp. CIR specimens have tender surfaces and don t lend themselves well to some tests

Characterization of CIR Properties CIR is produced from the existing asphalt concrete paving layers using in-place recycling methods, creating an interlayer of semi-bound material of medium modulus, higher voids resisting crack propagation and enhanced resiliency to the pavement structure, while being of sufficient strength to withstand loads transmitted from the overlying layer(s) of asphalt concrete. CIR can be designed, constructed and placed to meet almost whatever parameters are required and conditions that are encountered in the field, including the occasional and/or temporary possibility of it being the top ridding surface or in some cases even the final roadway surface.