recycling dfw metroplex pavements: why, how & how much?
TRANSCRIPT
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
Thank You!
Dan Richwine
Texas Industries
972-409-3240