presentation on full depth rehabilitation
TRANSCRIPT
FDRFull Depth Rehabilitation
By: Donatas Greb, PE Richard Haro HSI Engineering, Inc.
OUTLINE
1. What is FDR?2. Challenges of traditional design3. Benefits of using FDR?
• Low cost• Sustainability• Constructability• Performance
4. Design of FDR5. Construction of FDR 6. Questions & Answers
TYPICAL CALIFORNIA STREET
FDR is a process in which the existing asphalt surface is Pulverized in place and blended with the underlying base, sub-base, and/or subgrade materials, mixed with Portland Cement, and compacted to provide a new stabilized base that is high strength, non-plastic, and less permeable. A new surface course is then applied, which completes the FDR process.
FDR Definition
FDR SHOULD BE USED WHEN:
■ SERIOUSLY DAMAGED PAVEMENT
■ BASE OR SUB-BASE FAILURE
■ PATCHING OVER 15%-20% of PROJECT AREA
■ TRAFFIC LOADING EXCEEDS DESIGN
WHEN TO USE FDR ?
PAVEMENT RECYCLING OPTIONS
Cold In-Place Recycling ( 2 to 9 inches)
(8-10 years design life)
Hot In-Place Recycling ( 0.6 to 4 inches)
(2-4 years design life)
Full-Depth Rehabilitation ( 6 to 18 inches)
(20+ years design life)
BENEFITS
• Increased Strength Spreads Loads
• Bound Base Material Section
• Reduced Moisture Susceptibility
• Faster & Easier to Construct
• Thinner AC Pavement Section
• Longer Pavement Life Cycle
• 30%-50% lower cost
AGGREGATE SHORTAGE CHALLENGE(Caltrans Warning)
“…tremendous amount of aggregate needed…”
“…concern about the availability of aggregate…”
“…encourage the development of new material sources…”
SOLUTION: RECYCLE FIRST
ECONOMIC CHALLENGE
-”Best First Approach” doesn’t address all roads
-Projected funding can not keep up
-Increasing rehab costs
Project ProfileBancroft Avenue, San Leandro2-lane Major Collector, 136,000sft.4” AC over 12” FDR using 5% cement
$4.05/sft. - FDR Cost $7.36/sft. - Traditional Pavement CostHSI Engr’g & Inspection Services Fee= 3% const.
ENVIRONMENTAL & ECONOMIC SAVINGS
FDR VS. REMOVE/REPLACE (50,000 sft. , 12-in Deep )
Number of Trucks Required
Material Required (Tons)
Diesel Fuel Consumed (Gal)
120 Loads Export
146 Loads of Aggregate Import
4 Loads of Cement
3,650 Tons New Aggregate
108 Tons of Cement
3,920 Gallons 480 Gallons
FDR ProcessRemove/ Replace Process
ENVIRONMENTAL SAVINGS
1 Cement Truck =
40 Gravel Trucks
IMPROVED LOAD DISBURSEMENT
100 psi 100 psi
20 psi
NON-STABILIZED BASE STABILIZED BASE
5 psi
Stabilized Bound Base
Non-Stabilized Unbound Base
FDR CREATES AN “Inverted Pavement”
NON-STABILIZED BASE STABILIZED BASE
LANDSCAPE AREAMOISTURE INFLUENCE ON PAVEMENT SECTIONS
Moisture infiltrates base:
• High water table • Trench leaching• Landscape irrigation• Capillary action
Stabilization:
• Reduces Permeability • Reduces moisture influences• Maintains strength and stiffness
MAINTAINS PERFORMANCE UNDER SATURATED CONDITIONS
LOCAL FDR CLIENTS
Public Works Projects
City of San Leandro City of Oakland City of Santa Clara City of Marysville City of Hayward City of San Carlos City of Watsonville Yolo County City of Tracy Santa Cruz County
Private Projects
Stockton Lockeford Port of Oakland Campbell Palo Alto Dublin Mountain View Gilroy San Jose Pleasanton Hayward San Benito Carmel Valley San Mateo County Danville San Carlos
HSI FDR SERVICES
1. Coring/Sampling 2. Lab Analysis3. Mix Design4. Strength Determination5. Contract Documents6. Construction Inspection /
Support
FDR DESIGN
A standardized structural value is given to the stabilized base:
Caltrans Design Equation:
Gf = 0.9 + (UCCS/1000) UCCS in psi
Minimum Unconfined Strength = 300 psi
Minimum Thickness = 10 inches
Maximum Thickness = 18 inches
“Making a Better Aggregate Base”
1. CORING / SAMPLING
2. LAB ANALYSIS 3. MIX DESIGN
Determine moisture density relationships (ASTM D1557)
Add between 3 to 7 percent cement
Prepare Unconfined Compressive Strength (UCCS) test samples
4. STRENGTH DETERMINATION
UCS Testing per ASTM D1633 (Method A)7-day strength targets from 300 psi to 650 psiUse accelerated cureTest performance (durability) in wet-dry
environments
5. CONTRACT DOCUMENTS
REMEMBER! - FDR IS A FLEXIBLE PAVEMENT
300 psi = Gf 1.2
Typical Strength Curves for Cement Treated Bases and Soils
FDR CONSTRUCTION STEPS
1. Pulverize 2. Regrade / Shape3. Spread cement4. Mix & Hydrate5. Compact6. Apply Surface
1. Before Full-Depth Rehabilitation 2. Pulverize Pavement 3. Re-Shape Grade
4. Apply Cement 5. Mix & Hydrate Cement 6. Initial Compaction
7. Final Grading 9. Pave FDR8. Final Compaction & Curing
S T A R T
FINISH
THE PROCESS Start to Finish in about 3-5 Days
STEP 1: PULVERIZE
PULVERIZED
SUBGRADE
SUBGRADE
EXISTING BASE
EXISTING BASE
RE-ESTABLISHING GRADE:
• Allows room for new AC section
• Observe conditions for instability
• Allows for temporary traffic
STEP 2: REGRADING AND SHAPING
SUBGRADE
PULVERIZED
EXISTING BASE
STEP 2: REGRADING AND SHAPING
65% to 80% Recycle In-Place
75% to 100% Recycle In-Place
100% Recycle In-Place
Curb & Gutter Conform to established grades
Remove existing AC to allow for new AC section
Re-establish Crown allows for additional use of recycled material
No grade restraints allows for 100% In-place recycling
IS OFFHAUL REQUIRED?
Spreading of Stabilizer
STEP 3: SPREAD CEMENT
SUBGRADE
PULVERIZED
On-board controls provide for ametered material application.
Mechanical vane spreader allows for uniformdistribution.
STEP 4: MIX & HYDRATE
Complete mixing, hydration and
compaction within 2 hours.
STEP 5: COMPACTION
FINAL GRADING
•Finish grade after initial compaction achieved
•Final Compaction with smooth drum roller
Moisture Cure
• Keeps section from drying
• Allows for continued hydration and even curing
Chip Seal
HMA Overlay
STEP 6: APPLY SURFACE
CONSTRUCTION QUALITY CONTROL
Gradation Moisture Density
Compact between 93% and 95%
modified proctor (ASTM D1557).
Add moisture for Compaction and
moisture for Cement Hydration for
minimal shrinkage.
-100% pass 2-inch sieve-minimum 95% pass 1-
inch sieve, and a minimum of 55% passing
No. 4 sieve
Maximum Density
95% of Maximum
Allowable Moisture Range @ 95%
Optimum Moisture
Moisture Content Relationships
Required Moisture for Cement Hydration @ 2 cement to 1 water Relationship
Cement - Allow for cement hydration prior to compacting (Approx.. 30 min from final mixing)
Optimum Cure Moisture Range
MOISTURE CONSIDERATION
HSI ENGINEERING INC. SERVICES
• VALUE ENGINEERING
• EVALUATION OF EXISTING PAVEMENTS
• ASSESSING REHABILITATION OPTIONS
• ENGINEERING AND DESIGN
• FORENSICS, REFEREE TESTING
• INSPECTION & QUALITY CONTROL
ALTERNATIVES
FULL-DEPTH REHABILITATION
SOLUTIONS IN CEMENT STABILIZATION
QUESTIONS ?
www.fulldepthrehabilitation.com