Webinar_Full_Depth_Reclamation_2_3_2022.pptx

1
Dirt Gravel and Low
Volume Road Program
WEBINAR
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2/3/22 Starts at 9am

Full Depth Reclamation
Presenters
- Eric Nevel
- Dave Morrison
- Steve Bloser
CDGRS WEBINAR SERIES

Objectives
Dust Control
• FDR is a tool, but not a silver bullet
• DGLVR Program does not fund many FDR projects
Additional requirements enacted in
2019, and limited to paved roads

Objectives
- Define FDR
- Define when FDR is appropriate
- Define what additives are appropriate and program approved
- Understanding of mix design steps
- Understanding of construction process
- Understand why assumptions often lead to poor FDR pojects
CDGRS WEBINAR SERIES

DGLVRP funding of FDR overview
• Fill out grant application- (10% Design)
• Get approved by QAB
• Get an independent mix design
• Put mix design out to bid. (All contractors bidding
on same mix design, based on soils, traffic, etc.)
• Construction
• Quality Control

Full Depth Reclamation : Total road rehabilitation of
existing surface and base, including adding water and
other materials (when necessary), mixing, shaping,
and re-compaction to create a stable road base.
Objectives
Dust Control

Reclamation (FDR): Total road rehabilitation of existing surface and
base, including adding water and other materials (when necessary),
mixing, shaping, and re-compaction to create a stable road base.
Objectives
Dust Control
4-8” grind depth is “re-profiling”, not FDR
- Often sold to the customer as FDR
- Used to reestablish road shape (crown/cross-slope)
- Often used on paved roads when the asphalt needs resurfacing
- Does not address underlying base problems
- There are often better ESM options than a shallow grind
8-12” grind depth (or deeper) is FDR
- FDR, if properly done, can fix the underlying base issues that cause problems
in the surface
- Provides a solid base for the new surface material

Objectives
Dust Control
• The most cost-effective solution when poor subgrade is
contributing to pavement failure on a long road section
• Stronger than aggregate subbase…results in a higher
strength sub-base section
• Stabilizes soils…eliminates the need to undercut and
replace unstable soils
• Permits regrading of poor roadway profiles caused by base
failure
• Can widen roadway by widening road base
BENEFITS OF FDR

Objectives
Dust Control
BENEFITS OF FDR
• Repairs the entire road width; mill/fill or traditional base
repair can miss suspect areas
• Uniform roadway support; no variability from past
widening/overlays
• Traffic control (can work one lane at a time and open to
vehicular traffic after 2 to 4 hours and heavy truck traffic in 1-
5 days)

Objectives
Dust Control
BENEFITS OF FDR

Objectives
Dust Control
BENEFITS OF FDR
FDR is a “green” technology
that reuses all existing
materials
• Little removal of
material
• Little landfilling or
wasting material
• Less quarrying for
aggregate

THE SHALE GAS BOOM
FDR is a fairly new technology
that was brought to PA during
the Marcellus gas boom

THE SHALE GAS BOOM
PennDOT and CDGRS developed
the specification for FDR
(PennDOT Pub. 447) during the
early years of the gas boom.

THE SHALE GAS BOOM

THE TYPICAL PROBLEM
Full Depth Reclamation is also a useful tool
for traditional road base/surface problems.

THE TYPICAL PROBLEM

Resurface with Stone, Chip Seal or Asphalt
• Is the overlay fixing the problem or temporarily hiding the
problem?
Problems/Issues
• Only temporary if underlying soils or aggregate sub-base are
not capable of providing support
Traditional Repair Options
1. Throw rock, chip seal, or asphalt at it…
2. Mill and fill…
3. Base Repair…

Mill and fill
• Does the milling remove all unstable base material, including
shoulders and edges for the new surface?
Problems/Issues
• Milling isn’t deep enough to correct base problems
• Shoulders and edges can still be unstable, affecting the road edge.
2. Mill and fill…
3. Base Repair…

Base Repair
• How much base repair is needed? Cost…
Problems/Issues
• Will base repair cover all unstable areas?
• Inconsistent road base
2. Mill and fill…
3. Base Repair…

Base Repair…

ESM Option - FDR
• FDR involves mixing the existing
asphalt, aggregate subbase, and
underlying soils with imported
materials to produce a high
strength subgrade layer.
• Surface is placed overtop of FDR
layer.
• Depth: 8” to 12” – normal traffic
and 12” to 16” for heavy traffic.
• Stabilized layers are stronger and
more durable than aggregate
subbase.

Types of Full Depth Reclamation
Selection of FDR depends on existing conditions, materials,
and target strength (bearing capacity)
• Pulverization (with no external material added, 1st step for all FDR
• Chemical Stabilization (cement, flyash, calcium chloride, etc.)
• Bituminous Stabilization (emulsion, foaming)
• Mechanical Stabilization (aggregates, RAP)
• Combination of preceding methods (all include added water)
• All additives must be DGLVR Program “Approved products”

DGLVRP funding of FDR
• Independent sampling and mix design
• Construction
• Quality Control

Design Process

Distress Assessment
• Determine the primary causes of the pavement distress in order to
evaluate feasible options for remediation
• Determine types and severity of distress:
• Asphalt rutting vs base rutting
• Cracking – fatigue, edge, thermal, base failure
• Base failure – determine percent repair necessary
• Asphalt oxidation and aging
• Identify drainage and groundwater problems
• Identify any variable cross-sections (esp. along roadway edges)
• Identify any deficient shoulder (support and width)

Candidates – Base Repair

Candidates – Base Rutting

Candidates – Drainage

Candidates – Subgrade Instability
Note - only LVR roads are eligible for
FDR grant funding in the DGLVR
program. Roads must be paved or
sealed.

Unpaved roads – not a candidate in DGLVR Program

Asphalt surface distress – not a candidate

Independent Sampling for FDR
• Evaluates the existing
pavement and soil subgrade.
Obtain samples
• Measure thickness of asphalt
and aggregate subbase
(becomes part of mix)
• Determine type of subgrade
soils, in-situ stability
(DCP/CBR), and moisture
• Identify drainage and
groundwater problems

Cores vs. Test Pits
CORING
Pro – less road disturbance
before project
Cons - requires use of an auger to
get material for a sample. Will
add to cost of mix design if
engineer has to mobilize coring
machine and/or auger
- May require multiple cores at
each test location to obtain
sufficient size representative
sample

Cores vs. Test Pits
Test Pits
Pros - If you use your own
equipment to provide test pits
for the engineer, it will save you
money on the mix design
- Easy sample collection
Con – more road disturbance
before project

What to expect during sampling
- Sampling spec. is 1 test pit every 500 feet, minimum of 3 test pits.
(1 mile would be about 10 test pits) – PennDOT Pub. 447
- Collect sample from first test pit. Additional test pits are to make
sure soil, gravel, pavement, etc. are consistent for entire length of
road
- If material changes, additional samples are taken to make an
“average” mix design

-The reclaimer cannot grind bedrock
-This road section is not an FDR candidate

The mix design can account for areas where the road has been widened without stabilizing the base

Be sure to plan for correcting all drainage issues before construction

Mix Design Basics
• Soil classification – gradation, Atterberg limits, and moisture
to help determine appropriate chemicals to use
• Design will include:
– additive type(s) used (if any)
– grind depth
– application rate
– Soil moisture
– Long-term traffic and service life
– Can be custom designed for desired surface material
– Required compaction effort to achieve design strength
– Water content (optimum moisture)
• The only additive common to all FDR mixes

Common chemical additives
• Aggregate – Mechanical Stabilization
• Cement
• Bituminous Emulsions
• Flyash
• Quicklime and Limekiln Dust
• Calcium Chloride
*The additive/chemical type, depth, and application rate depend on
- soil type (gravel, sand, silt, clay)
- moisture
- weather and construction season
- Long-term traffic and service life

DGLVR Policy on additives
 Aggregate – Mechanical Stabilization
 Cement
 Bituminous Emulsions*
 Flyash**
 Quicklime and Limekiln Dust**
X Calcium Chloride (may not be used)
Any additives or binding agents used in chemical stabilization must be on the
Program’s “Approved Products” list or possess DEP certification for use as road fill.
* Bituminous emulsions must be on the Programs approved products list to be used on DGLVR
funded projects.
* * Flyash, Limekiln dust and other industrial byproducts must possess a DEP certification or be
included on the Programs approved products list to be used on DGLVR funded projects.

Additive vs. Soil Type
- Any additive used should be based on the soils under the road
- Contractors may choose the additive that is most profitable
to them even if it isn’t the best choice for your road

Additive vs. Soil Type

Additive vs. Weather

Basic Mix Design Testing
Specific mix design test will vary between additives
- cement and lime use the unconfined compressive
strength test, while emulsion uses the marshal
stability test.
General procedure is to replicate the soil, aggregate
and additive to be mixed in different percentages of
the chemical to fabricate samples for strength testing.
- i.e. for cement 3 samples for each: 4% cement, 6%
cement, 8% cement
-i.e. for emulsion 4 samples for each: 2%,2.5%, 3%,
3.5% emulsion

Typical Strength Test Results

Strength depends on:
- Soil type
- Aggregate type and gradation
- Amount of existing asphalt
- Amount of existing aggregate
- Moisture conditions
- Temperature

Roadway design criteria
Important to know specifics on desired roadway
- What Type and Volume of traffic is expected, and will it
change over time?
- What life span is needed?
- What type of surface is desired? What thickness?
- Can the vertical alignment change?
(Adding material will raise surface elevation)
- Are there curbs, sidewalks, utilities, etc.?
- Can drainage issues be repaired?
- How quickly will the road be exposed to traffic?
- During what season will work be performed?

FDR Thickness Factors -

Pavement Design Goes hand in hand with mix design
• AASHTO Methodology in accordance with PADOT standards:
– Treat FDR material as a distinct layer within the pavement section
– Low volume traffic FDR is typically 8 to 12 inches
– Heavy traffic FDR is typically 12 to 16 inches
• Surface with:
– Asphalt
– Aggregate Surface
– Chip seal – risky due to loss of chip seal and exposure of base
material (single layer chip seal not recommended)
– Be sure to choose a surface that you will be able to maintain
– The mix design can be tailored to the surface you want

Pavement Design Example
Effect of varying subgrade soils on pavement design
Poor Soil CBR = 3
• Asphalt Pavement = 4.5 in
• FDR Stabilized Base = 12 in
Competent Soil CBR = 8
• Asphalt Pavement = 2.5 in
• FDR Stabilized Base = 12 in
By determining the soil characteristics, the asphalt thickness
was reduced by 2 inches leading to big savings.

Common Problems when not utilizing an
independent mix design
• Using predetermined chemical type – cement, lime and asphalt
emulsion have distinct characteristics and limitations.
• Using untested chemicals
• Using predetermined chemical amount.
• Assuming an FDR depth (should be based on proposed pavement layers
and traffic)
• Not considering the type and strength of the underlying native soils
(native soils have a huge influence on roadway stability and pavement
performance)

Common Problems when not utilizing an
independent mix design
• Using predetermined asphalt overlay thickness (need to design
to specific soil and traffic conditions
– Ex: 5-inch HMA overlay on an alley…waste of money
– Ex: 1.5-inch overlay on a roadway…too thin
• Testing the wrong mixture of materials
• Not performing a pavement design (an over-conservative guess
can be a waste of money and an under-conservative guess will
fail prematurely)

Don’t assume or guess…sample data
6 and 8 percent cement
y = 7.8029x - 691.26
R
2
= 0.1979
y = 12.793x - 1175.1
R2
= 0.1942
0
200
400
600
800
1000
1200
90.0 100.0 110.0 120.0 130.0 140.0
Subgrade MDD (pcf)
UCC
(psi)
6 and 8 percent cement
y = 3.9857x + 222.47
R2
= 0.099
0
200
400
600
800
1000
1200
0 10 20 30 40 50 60 70 80
Milling (%)
UCC
(psi)

-Less than 1 year old FDR project
-Mix design by contractor
-No sampling performed

Entrenched road with drainage issues.
Why wasn’t this a road fill project??

• Put mix design out to bid and address drainage
issues (All contractors bidding on same mix
design, based on soils, traffic, etc.)
• Construction
• Quality Control

Address Drainage first
Now is the time to fix all
drainage problems
Install underdrains and
cross pipes before FDR
* It will be very difficult to
address any drainage
issues after the base is
stabilized, especially
if chemical stabilizers are
used

Protect Drainage & Other Buried Features
This concrete cross pipe would break the reclaimer!!!
- Buried utilities and drainage
structures need to be clearly
marked so the reclaimer
operator can see them.
- It’s very easy to hit a buried
cable, underdrain, or shave
the top off a new plastic
cross pipe

Consider Intersection Tie-Ins
- You may want to consider
reclaiming 50-200 feet of any
road that intersects the road
you are working on.
- The lack of a smooth transition
between the two roads can
damage both roads, especially
in areas with heavy hauling.

Lateral Restrictions
- Pay attention to lateral restrictions, such as
guiderails, which could affect grind widths
- reclaimers can grind more closely on one side,
some maneuvering may be necessary

Base and surface widths
If the final design is for a
20-foot-wide paved road,
you’re going to need 22
feet of stabilized base!!!

• Construction
• Quality Control

FDR Construction Process
• Pulverization – step one for all types of FDR
• Stabilizing Agent Addition
• Compaction & Shaping

Pulverization
Pulverization consists of grinding the road
surface and base to be reclaimed.

Pulverization
• Before mixing chemicals, the road needs an initial
grind to break up the surface material and mix it
with the underlying base, sub-base, and/or
subgrade.
• At least 2 full passes during pulverization. The
pulverized material should look homogeneous.
• Overlap passes at least a foot.

Carbide teeth, just
like grader blade

Photo courtesy: Cutting Edge Reclamation, LLC

• Pulverization

Stabilization
- Consists of the addition of the selected dry additive
onto the pulverized surface.
- Liquid additives are added directly to the reclaimer

Chemically stabilized roads must be surfaced!!
- Dust can be hazardous
- Chemically stabilized base will fail if
not surfaced

Watch that dust!!!
- If possible, use a grader to create
windrows to keep the chemical
within the road profile
- Silt socks are also recommended
on both sides of the road

In the second pass of the reclaimer, the stabilizing agent
and water are integrated into the pulverized roadway.
Mixing

Mixing
Cement stabilizing
agent
Second pass mixing

Mixing
Does this
material
look like it’s
well mixed?

Mixing
Water
NO!!

Mixing
Water
And/or
liquid
additive
YES!!

• Pulverization

Initial Compaction
A sheepsfoot roller should be used for
maximum compaction immediately after the
final grind.

Shaping
After initial compaction, shaping consists of grading the base to
match the desired crown or slope of the finished surface.

Crown and cross slope need to be built with reclaimed material
Check the base for proper crown prior
to final compaction and surfacing.

Finish Compaction
A smooth drum, vibratory roller finishes the surface after shaping

Regardless of the stabilization method, the
reclaimed roadway will require the placement
of a driving surface overtop.

Quality Control Technician
• Evaluates stability of soils below the FDR layer,
which may need deeper stabilization
• Measure chemical application rate and mix
depth
• Monitor moisture levels in soil and adjust water
application rate
– Too dry - chemical needs water to react
– Too wet – additional chemical to dry soils
• Verify adequate mixing
• Fabricate specimens for compression testing
• Perform field density testing for compaction

Quality Control Technician
• Monitor material application for dust
control (especially cement)
• Monitor traffic control to avoid vehicle
exposure to chemicals and treated soils
• Monitor FDR width to provide 1 foot overlap
at edges and sufficient width to support
surface material
• Identify overlooked drainage issues from
springs and cross-drains
• Evaluate final stability of FDR prior to paving
by proof-rolling.

Typical Problems with No Quality Control
• Uneven application rates of additives
• Uncontrolled moisture rates (too dry and too wet will create
durability problems)
• Waiting too long to roll and fine grade the mixture, which allows it
to set up
• Inadequate compaction and low density of material
• FDR does not extend laterally beyond edge of overlay (too narrow)
• Premature traffic on completed layer

Eric Nevel – CDGRS
ern106@psu.edu
814-599-8297
Resources:
Portland Cement Association (PCA)
National Lime Association (NLA)
Asphalt Recycling and Reclaiming Association (ARRA)

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