Recycling DFW Metroplex Pavements: Why, How & How Much?

Matthew W. Singel, P.E.

Program Manager

Soil Cement/

Roller-Compacted Concrete

Recycling DFW Metroplex Pavements:

Why, How & How Much?

Dan Richwine

Sales Manager

Cement Treated Materials

Cement Council of Texas

Hurst, Texas

(Fort Worth Area)

Serving Texas as:

•Technical Resource

•Catalyst for Research Initiatives

•A Conduit for Innovations

•Trainers for Design and

Construction Professionals

Water Content

Cem

en

t C

on

ten

t

Roller-Compacted

Concrete

Conventional

Concrete

Soil-Cement

Flowable Fill

Cement-Modified

Soil

Full-Depth

Reclamation

Cement-

Treated

Base

Cement-Based Pavement

Materials

Pervious

Concrete

Soil Cement Materials in a

Pavement Section

Method of flexible pavement reconstruction that utilizes the existing asphalt, base, and subgrade material to produce a new stabilized base course for an asphalt, chip seal, or concrete wearing surface.

Alternative Terms:◦ Full-Depth Recycling (FDR)◦ Cement Stabilized Reclaimed Base (CSRB)◦ Full-Depth Rehabilitation (FDR)◦ Cement-Treated Existing Roadway Materials (C-TERM)◦ Cement Recycled Asphalt and Base (CRAB)◦ Cement Recycled Asphalt Pavement (CRA……)

Definition of Reclamation

Reconstruct Pavements

◦ Fast - ½ to 1 lane-mile/day

◦ Inexpensive – Saves 25% to 40% vs remove & replace

◦ Increase Strength, Uniformity & Moisture Resistance

Reuse Materials In-Place

Drastically Reduce Impact on Natural Resources (Virgin Materials) and Material Hauling

Provides Low-Maintenance, Long-Lasting Base (25+ years)

Benefits ofAsphalt Pavement Recycling (Full-Depth Reclamation with Portland Cement)

Design

(pre-construction evaluation)

The procedure includes the following steps:

◦ Site Investigation.

Determine cause of failure

Take core samples/test holes

Establish layer thicknesses

Obtain material samples to use for mix design

◦ Lab Evaluation.

Develop representative samples

Use proportioned materials from site investigation

Goal: Simulate Construction Process

Pre-Construction Testing

Construction Process

Pulverize existing pavement

Add cement (dry or slurry form)

Mix & add moisture (if necessary)

Compact

Place surface◦ Asphalt

◦ Seal Coat

◦ Concrete

Easy Construction Process!

Spray Bar for Water

Pulverize

Dry Form

Slurry Form

Apply Cement

Blend Materials & Add Moisture

Compact & Grade

Asphalt

Concrete

Add Surface Pavement

The success of a recycling project depends upon the careful attention to the following specified control factors:

Sieve Analysis (ASTM C136)

Atterberg Limits (ASTM D4318)

Moisture-Density (ASTM D558)

Durability Tests

◦ Wet-Dry (ASTM D559)

◦ Freeze-Thaw (ASTM D560)

Soluble Sulfates (ASTM D516)

Compressive Strength (ASTM D1633)

Quality Control

Introduces a network of fine fractures into the base to mitigate the formation of major cracks

10-12 ton vibratory roller applied 1–2 day after placement

Low Speed

At High Amplitude

2 – 4 passes

Microcracking

PCA Document LT 299

Finished Base

• Retards Reflective Cracking

• Increased Stiffness Spreads Loads

• Eliminates Rutting Below Surface

• Reduced Moisture Susceptibility

• Reduced Fatigue Cracking

• Allows Thinner Overall Pavement

Section

Engineering Benefits

“The need to ensure that development meets the needs of the present without compromising the ability of future generations to meet their own needs.”◦ 1987, UN Bruntdland Report

Sustainable Development

Diesel

(gal)

Removal

(cu yd)

Material

(tons)

Trucks

(Number)

New

Recycle

180

12

4500

300

2700

0

3000

500

1 Mile of 24’-wide 2-lane road,

6” base + 2” asphalt surface

Equipment & Materials:

Recycling vs. New Base

Systematically evaluates environmental impacts of a product or system

Considers all impacts◦ Extraction of raw materials

◦ Manufacture

◦ Service life

◦ Demolition

Helps determines systems with least impact on environment

3 Phases: Inventory, impact assessment and evaluation

Life Cycle Inventory/Analysis

Full-Depth Reclamation

Evaluation

Provides Structure in Subgrade Soils

Reduces Construction Time & Fuel Consumption vs Other Base Methods

Offers Long-Term Support for Overlying Pavements◦ Does Not Dissipate (Leach Out) With Time

◦ Reduces Thickness of Overlying Pavements

Cement-Stabilized Base:

Unstabilized Granular Base

100 psi

15 psi Cement-Stabilized Base

• Soil-Cement Base

• Cement-Treated Base

• Full-Depth Reclamation

100 psi

4 psi

Increased Rigidity Spreads Loads

High water table

Moisture infiltrates base:

• Through high water table

• Through capillary action

• Causes softening, lower strength,

and reduced modulus

Cement stabilization:

• Reduces permeability

• Helps keep moisture out

• Maintains high level of strength

and stiffness even when saturated

Unstabilized Granular Base Cement-Stabilized Base

Reduced Moisture Susceptibility

Unstabilized Granular Base

Cement-Stabilized Base

• Soil-Cement Base

• Cement-Treated Base

• Full-Depth Reclamation

Thinner Pavement Section

Recent Local Projects

Cities◦ Bedford◦ Dallas ◦ Grand Prairie◦ Fort Worth◦ Southlake◦ Denton◦ Arlington

Counties◦ Collin County◦ Dallas County◦ Denton County◦ Ellis County◦ Kaufman County◦ Tarrant County

& Local TxDOT Districts (and many districts statewide)

Reconstructs Asphalt Pavements

◦ Fast - ½ to 1 Lane Mile/Day

◦ Inexpensive – Saves 25% to 40% vs Remove & Replace

Reuse Materials In-Place

Drastically Reduces Impact on Natural Resources

(Virgin Materials)

Provides Long Lasting Base (25+ years)

“Portland Cement is probably the closest thing we have to a

universal stabilizer.”

- From a U.S. Army Corps of Engineers Report dated September 2002

Benefits ofAsphalt Pavement Recycling (Full-Depth Reclamation with Portland Cement)

What About Performance?

Full Report

(60 pages)

PCA SR016

Summary

(4 pages)

PCA IS689

News, Events, Developments

General FDR Information

Project Descriptions

Provides Testimonials

www.RecyclingRoads.org

Case Study: City of Dallas

Sustainable is Obtainable

A Success Story

Pre - 2004

Today The City of Dallas recycles a minimum of 80% of their streets

Three new categories were established to evaluate each street

Each street is classified either Rehabilitation, Restoration or Partial Reconstruction

For asphalt street.

25% or less of the street needs fixing.

Repairs a localized area.

Millings are recycled to produce CTB and placed back into the patched area.

For asphalt street.

30% or more of the street needs repair.

Requires Full Depth Reclamation (FDR).

Some milling may be required if existing grade is higher than curb lines.

For concrete streets.

30% or less of the street is need of repair.

Concrete is hauled to crushing facility.

Rebar is removed & recycled.

Concrete is crushed into base material.

In 6 months started benefiting economically, environmentally and socially.

Of the three categories FDR is most beneficial.

FDR saves approximately 40% per lane mile.

By using FDR, Dallas is able to restore 3 times as many lane miles in a given period.

This saving in time is also a saving in cost.

Un-bonded

Cost Type FDR COST C.T.B. COST Flexbase COST %Reduction

N0x emissions 7.30 376.88 852.46 99%

(in pounds)

Fuel Consumed 772.50 1284.64 4324.17 86%

(in gallons)

Truck Miles 253.3313,086.2

1 29,599.14 99%

TOTAL COST $38,508.25 $70,678.47 $110,147.50 79%

*To replace 1 mile of street 20' wide, 6" depth,(6% cement except for flex base which is un-bonded)

10 miles from plant, 20 miles from landfill, 67 miles from stone quarry

Truck emission of N0x as EPA standards is =1.802 tons per 125,000 miles, average fuel 5 MPG

Using a FDR program Dallas has

Dallas has achieved ISO 9001 (QC Standards) & ISO 14001 (Environmental Standards)

Working on ISO 18001 (Safety Standards)

Matthew W. Singel, P.E.

Cement Council of Texas

817-540-4437 ext 13

msingel@cementx.org

Thank You!

Dan Richwine

Texas Industries

972-409-3240

drichwine@txi.com