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