full depth reclamation...hydrated lime – dry or slurry (1-2%) portland cement & hydrated lime...

Cold Recycling

Overview

► Asphalt pavements eventually develop distress such as:

CrackingRavelingPot holesPoor Ride Quality

► Traffic, weather and hardening of the asphalt binder all contribute to these problems.

Introduction

► Cold Recycling is a process whose time has come…

environmentally soundgives enhanced performanceand saves dollars.

Types of Cold Recycling

► Cold Central Plant Recycling (CCPR)

► Cold In-Place Recycling (CIR)

CIR – Process Description

► Pulverizing existing pavement (2-5”)► Sizing of the reclaimed asphalt► Addition of new binder/additives► Mixing all component materials► Placement of the mixture► Compaction of the mixture

CIR – Cross Section

Classes of CIR

Multi-Unit Train Pulverize, Screen, Crush, Add Recycling Agent Based on RAP Weight & Mix in Pugmill

Two-Unit Train Pulverize, Add Recycling Agent Based on RAP Weight & Mix in Pugmill

Single Unit Train Pulverize, Add Recycling Agent – All in Cutting Chamber of Milling Machine

CIR – Multi-Unit Train

Multi-Unit Train

► Cuts to precise depth & width specified► Adds mixing water/liquid additives► Processes one full lane width► Propels the train► Pushes tankers ► Highly productive

Multi-Unit Sizing

► All reclaimed asphalt pavement (RAP) is screened to achieve a maximum size requirement(typically 1.25”).

► Oversized material is crushed and returned to the screen deck for total sizing control.

Multi-Unit Pugmill

► Belt scale weighs RAP, computer controls additives

► Multiple additives may be added simultaneously

► Pugmill thoroughly blends RAP and additives

Two-Unit Train

Single Unit Train

►Small size for urban projects►Short turning radius

Single Unit Train

►Pulverizing, sizing and mixing of Recycling Agent with RAP all take place in the milling machine down-cutting head.

►Proportioning of Recycling Agent is based on depth and width of cut and forward speed of train.

CIR - Laydown

Traditional Asphalt Pavers Used or …

CIR - Laydown

Mix Pavers may be also be used

CIR - Laydown

► Cold In-place Recycling laydownis done with the same equipment and controls as other maintenance mixes.

CIR - Compaction

Rollers necessary for CIR include a heavy pneumatic roller(s) (25 ton) and a steel wheeled roller(s)

CIR –Widening

CIR –Widening

Additional aggregate may be placed in the area to be widened.

CIR –Widening

CIR - Benefits

►Conserves Energy►Conserves Materials►Improves Mix Characteristics►Cracking Eliminated/Reduced►Improves Geometrics►Cost Effective►Saves Time►May Be Performed Under Traffic

CIR – Pavement Types

►Airport Runways►County Roads►State & US Highways►Interstate Highways►City Streets

CIR - Candidates

Thermal Cracking

Fatigue Cracking

Patched

Dry, Raveled

Poor Rideability

CIR – Project Selection

►Material Properties Evaluation►Existing Road Geometrics►Life Cycle Cost Analysis►Environmental Impact►Structural Strength►Pavement Condition►Road History►Traffic Study

CIR – Mix Design

1. Obtain Sample of RAP from Field2. Determine RAP Gradation, Binder Content,

Extracted Gradation and Aged Binder Properties

3. Select Amount and Gradation of Additional Aggregate, if required

4. Select Type and Grade of Recycling Additive5. Determine Pre-Mix Moisture Content6. Test Trial Mixtures: Initial Cure Properties, Final

Cure Properties, and Water Sensitivity7. Establish Job Mix Formula

CIR – Additive Selection

Asphalt Additives:► Asphalt Emulsion (w/ & w/o polymer)

Anionic Emulsions●HFMS-2●HFMS-2s

Cationic Emulsions●CSS & CMS

► Rejuvenating Agents► Foamed Asphalt

CIR – Additive Selection

Chemical Additives:► Portland Cement – Dry or Slurry (1-2%)► Hydrated Lime – Dry or Slurry (1-2%)► Portland Cement & Hydrated Lime have

been used in conjunction with asphalt emulsion to improve early strength,

increase rut resistance and improve moisture resistance

► Fly Ash – Class C Fly Ash (8-12%)► Used to cement RAP particles together

CIR – Additive Application

Dry Application.

Type C Fly Ash, Portland Cement or Hydrated Lime may be spread dry in front of the recycling train.

Slurry Application.

Portland Cement and Hydrated Lime may be applied in slurry form.

CIR – Aggregate Application

► The existing asphalt pavement properties may be enhanced with the addition of aggregate or RAP.

► The mix properties be improved and additional structure may also be added to the asphalt pavement.

CIR – QA/QC Plan

1. Calibration of meters2. RAP Gradation3. Recycling Additive4. Recycled Mat Smoothness5. Moisture added to RAP6. Compacted Density7. RAP Gradation8. Moisture content before overlay9. Recycling additive content10. Depth of pulverization/milling

Surface Treatments

Chip SealSlurry SealMicro-SurfacingCold Mix OverlayHot Mix Overlay

Cold Central Plant

► Cold Central Plant Recycling (CCPR) is a viable alternative when stockpiles of high quality RAP are available or when it is not possible to in-place recycle the pavement.

CCPR - Process

► Aggregate Feeding/Blending► Screening/Crushing► Liquid Metering Systems► Pugmill Mixing

CCPR - Applications

► Stockpile Mix. When the recycled cold mix is to be stockpiled for later use, an emulsion with cutters, such as diesel fuel, may be used. Rejuvenators may also be used to enhance mix workability.

CCPR - Applications

► Immediate Lay. When the recycled cold mix is to be placed immediately a quicker setting emulsion may be used.

Weather Limitations

►Air Temperature of 50 Degrees F. is preferred.

►Heavy Rain must not be occurring.

CIR Advantages

►Conserves Energy►Conserves Materials►Improved Mix Characteristics►Cracks Eliminated/Reduced►Cost Effective►Saves Time►May Be Performed Under Traffic.

After Overlay

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