Concrete Pavement
Preservation
National Concrete Pavement Technology Center
Iowa’s Lunch–Hour Workshop
In cooperation with the Iowa DOT
and the Iowa Concrete Paving Association
Maintaining the Service and Investment of the
Highway by Implementing Pavement Management
Into Cost-Effective
PAVEMENT PRESERVATION MEASURES
Service/Investment
2
Service Life
SHORT-TERM PAVEMENT
3
Service Life
LONG-TERM PAVEMENT
PDR and/or DG
4
What is Preservation?
5
• Materials
• Design
• Construction
WEST DES MOINES PAVEMENT
CURVES
6
Trigger/Limit Values for Preservation
(JPCP)
Performance
Indicator
Trigger
Value
Limit
Value
Repair
Trans. Cracking1.5-2.5% of
slabs cracked
5-15% of
slabs cracked
Partial, Full,
Dowel Bar
Repairs
Joint
Deterioration
2.0-4.0% of
joints
15-20% of
joints
Partial-Depth
Repair
Joint Faulting 1/8 inch3/8 – 1/2
inches*
Dowel Bar
Retrofit
Roughness 90 in/mi 170 in/mi*Diamond
Grinding
7
* CP Tech Center Values Adapted from Table 3.2 Preservation Guide
Start Programming
8
Treatment Performance Life
8 - 15
8 - 15
12 - 20
15 - 25
15 - 20
* CP Tech Center (adapted from Preservation Guide)
*
*
*
*
*
Order of Operations
9
Fig. 12.1 Preservation Guide (ACPA 2006)
• Surface Defects
• Surface Delamination
• Material Related Cracks
• Transverse & Diagonal Cracking
• Longitudinal Cracking
• Corner Cracking
• Spalling
• Faulting
• Joint Warping and Curling
• Blowups
• Settlement and Heaves
• Subgrades & Base Support Conditions
• CRCP
• Concrete Overlays, BCOA, BCOC, UBCOA,
UBCOC
• Laboratory & Field Testing
Distress Guide 2017
Focus:
• Identification
• Causes
• Prevention
• Rehabilitation
Concrete Pavement Preservation Guide
2014
• Contains 12 Chapters on
Preservation Techniques
• Focus on Repair Techniques
(how to do it)
DISTRESS TYPES
12
Settlement and Heaves
13
Causes
• Inadequate base compaction
• Consolidation of support layers under traffic
• Subgrade soil movement
• Loss of support (contamination of base layers)
• Frost heave
• Expansive soils
14
Settlement and Heaves
Prevention
Causes Design Material
Selection
Construction Preventive
Maintenance
Poor
consolidation
Characterize soil
based on
engineering
properties
Limit % fines to
10%
(passing #200
sieve)
Proper
compaction Routine joint
sealing
Periodic
maintenance
of drainage
system
including
cleanout of
outlets
Volume
changes in
soil
Compaction
specification based
on optimum M & D
Uniform soil,
blend, granular
subbase or
chemical
treatment
Uniform soil,
blend, granular
subbase or
chemical
treatment
Excessive
moisture
Provide drainage
Consider chemical
stabilization
Use drainable
subbase
Dry soils
Compact at
optimum M & D
Longitudinal and Transverse
Cracking
15
Types
• Volumetric changes (concrete)
• Volumetric changes (subgrade)
• Settlement and poor support
• Slab length
• Sawing practices
• Traffic loading (design)
• Sympathy cracks
16
Longitudinal and Transverse
Cracking – Causes and Prevention
Causes Prevention
Excessive slab length Follow guidelines, saw to
adequate depth
Late sawing Maximize sawing window,
increase labor/equip forces
Inadequate saw depth Check blades, saw to T/4
on transverse joints
Non-Uniform support Uniform drainage, compact
& subgrade volume changes soils, chemically stabilize
subgrade if needed
Traffic loading Use proper thickness, keep
construction traffic away
from edges
Cracking Treatment and Repairs
Repairs
• Full-depth repair
• Cross-stitching/Slot stitching
(longitudinal cracking)
• Crack sealing/Filling (if not
working crack)
• Diamond grinding
Maintenance
• Crack sealing
17
Slot Stitching
Appendix 9-6 Iowa DOT Construction Manual
18
Drainage System
Surface Water
Capillary Fringe
Water Table – 100% Saturation
Subsurface Water
Zone exposed to constant high moisture levels.
Controlled Drainage System
19
Subgrade Treatment Based on
Subgrade Conditions
No Subgrade Conditions Treatment
1 • Varying types of soil
• Meets M & D tests
• Passes proof roll test
• Disc and mechanically blend soils (8
in. lifts to 2 ft. depth) for subgrade
• Compact to 95% standard proctor
2 • Uniformly wet soils
• Does not pass proof
rolling or density test
• Dry subgrade by disking
• If drying weather is not available or
soils are too wet, utilize quick lime,
cement or fly ash
3 • Expansive or unsuitable
soils
• Chemically stabilize soil with cement
(changes the PL and LL to acceptable
levels.
• Remove unsuitable soils and replace
with select material
20
Spalling
21
Freeze thaw damage Saturated joint
backer rod damage Saturated joint with
unsound aggregate Incompressible joint
damage
Deflection spalling from
heavy vertical loads Early saw joint raveling Chloride penetration Dowel bar misalignment
Spalling - Causes
22
Distress Category Description
Spalling
(Material
or
Chemical)
Heavy application of
Magnesium &
Calcium Chlorides
Deicing chemicals react with Calcium Hydroxide (CH) causing flaking
of hardened paste
Freeze Thaw
Damage
Damage to the paste of the concrete from:
• Poor air entrainment system
• Saturated concrete joints/cracks
• Chemical breakdown of the concrete from deicing salts such as
calcium and magnesium chloride (Calcium Oxychlorides)
Thermal Expansion High coefficient of thermal expansion (CTE) of the aggregate results
in higher compressive stresses at the joint or crack.
Spalling
(Physical)
Infiltration Infiltration of incompressibles into poorly sealed or unsealed joints.
Compression Shear Compression shear from deflection of the slab, lack of load transfer,
or lack of subgrade support
Chipping/Fraying Early sawing of the joint which chips or frays the edges of the joint.
Moving Dowels Dowel bar movement from misaligned dowels.
Longitudinal Freeze Damage
From Backer Rod
Spalling – Saturation & Poor Air
• Saturation
• Marginal aggregate soundness
• Poor air void system
– Spacing < 0.008 in.
23
Shadowing
Spalling – Deicers
• The formation of Calcium Silicate Hydrate (C-S-H)
and Calcium Hydroxide (CH) are the two principal
ingredients that mesh into a solid mass forming
concrete pavement.
• Magnesium and calcium chloride will react with CH
with water at between 32ºF and 122ºF, depending on
the salt concentration.
Spalling – Deicers (Calcium
Oxychloride)
• This reaction results in the formation of calcium oxychloride which results in flaking (expansion) of the hardened paste causing significant damage particularly in joints.
• Oxychloride expansion can be 3 times greater than freeze-thaw expansion.
• The use of SCM’s ( fly ash, slag, and silica fume) will reduce formation of calcium oxychlorides by tying up CH
• Use of sealers has also shown the potential to limit interaction between salts and CH
Spalling – Summary of Prevention
• Prevent saturation
• Reduce concrete permeability
(Use fly ash to tie up CH)
• Ensure adequate air
entrainment
26
Image of a Super Air Meter (SAM)
(Photo credit Tyler Ley)
Spalling - Treatment and Repairs
Repairs
• Partial-Depth Repair
• Full-Depth Repair/Slab Replacement
• Retrofitted Edge Drains
• Unbonded Concrete Overlay
Maintenance
• Winter maintenance
• Maintaining sealed joints
• Maintaining sub-drain systems
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Faulting
28
Faulting - Causes
29
Distress Item Description
Faulting
(Physical)
Load Transfer
Loss
Failure of aggregate interlock or mechanical devices
that transfer load across pavement joints and cracks
Cracking
Longitudinal and transverse cracks that allow water
intrusion and lead to future faulting including loss of
load transfer
PumpingSeeping or ejection of water beneath the pavement
through joints or cracks
Loss of Seal
Integrity
Portal for intrusion of water into the grade
Faulting
(Material or
Chemical)
Poor Aggregate
Soundness
Poor quality coarse aggregate leads to early loss of
load transfer due to low shear capacity
Aggregate particles deteriorate resulting in loss of
support
Faulting - Treatment and Repairs
Repairs
• Dowel Bar Retrofit
• Bonded Concrete Overlay (if
faulting is less than less than 3/8”
faulting or Unbonded Concrete
Overlay for 3/8” to 5/8”)
Maintenance
• Diamond Grinding
30
Material Related Cracks - Causes
31
Physical and Material/Chemical Causes of Material Related Distresses – Distress Guide
Distress Category Description
Durability
Cracking
(Physical)
Freezing and
ThawingFreezing and thawing of critically saturated, susceptible
coarse aggregates that result in fracturing and/or
damaging dilation of the aggregate.
Alkali
Aggregate
Reaction
(Material or
Chemical)
Deleterious
Expansion Chemical reaction between the alkalis in the cement paste
and certain components in aggregates that result in
deleterious expansion
Fractured Aggregate In D-Cracked
Pavement (Photo Credit Karl
Peterson).
Staining Accompanying D-Cracking
at Joints (Photo Credit Aptech).
Aggregate Particle Fracturing due to
ASR (Photo Credit Karl Peterson).
Material Related Cracks - Prevention
ASR Prevention
• Use SCMs
• Avoid susceptible
aggregates
D-Cracking Prevention
• Use durable
aggregates
• Provide adequate
drainage
32
Type of SCM
Total
Cementitious
Materials
Low-calcium fly ash
(<8% CaO; typically Class F fly ash) 20 to 30
Moderate-calcium fly ash
(8 - 20% CaO; can be Class F or Class C
fly ash)25 to 35
High-calcium fly ash
(>20% CaO; typically Class C fly ash) 40 to 60
Silica Fume 8 to 15
Slag Cement 35 to 65
Required Levels of SCMs to Control ASR (Thomas,
Fournier, and Folliard 2013) – Distress Guide
Material Related Cracks -
Treatment and Repairs
Repairs
• Partial-Depth Repair
• Full-Depth Repair/Slab
Replacement
• Retrofitted Edge Drains
• Unbonded Concrete Overlay
Maintenance
• Joint Filling/Sealing
• Edge Drain Maintenance
• Topical Treatments33
COMMON REPAIR METHODS
34
Partial-Depth Repair
Key Factors for Success
• Proper selection of candidate projects
• Proper material selection
• Identification of repair boundaries
• Use of joint/crack reformers
• Achieving good bond
• Proper placement and curing
35
Partial-Depth Repair
36
Type 1 – Spot Repairs
Type 2 – Extended Length Joint and Crack Repairs
Type 3 – Bottom-Half Spot Repairs
Partial-Depth Repair Steps
1. Sounding
2. Marking Removal
3. Removal
4. Sand & Air Blast
37
1 2
3 4
Partial-Depth Repair Steps
5. Compressible Insert
6. Grout/Epoxy
7. Patch (Grout edge)
8. Curing
9. Joint seal
38
5 6 7
7 8 9
7
Partial-Depth Repair Removal
Sawing / Jackhammers
• Small to medium walk-behind saw for
perimeter cuts
– Maneuverability
– Positioning on paint marks
• Select light-weight hammer
– 15 to 30 pound
– More control
– Less fatigue
• Use chisel or narrow spade bit
for removal
Partial-Depth Repair Removal
Milling
40
Milling Speeds
• Speed of Milling (2” depth)
– Limestone: 20 ft per minute
– River Rock: 12 ft/ minute
– Granite: 5 ft/ minute
InvestigationDesign
•PDR Guide
•Iowa DOT DS 15022
•Iowa DOT Spec 2530
(Oct. 17, 2017)
Construction
Partial-Depth Repair Summary
City of West Des Moines
Full-Depth Repair
Key Factors for Success
• Removal (4’ min.)
• Dowel bar holes (grout vs.
epoxy)
• Proper material selection
• Proper placement and
curing
• Include as part of Partial-
Depth Repair
43
Dowel Bar Retrofit
• Restores load transfer
• Reduces probability of pumping, faulting, and corner breaks
• Improves long-term rideability
• Increases service life
44
45
Dowel Bar Retrofit
• Need compressible insert
• 3 bars per wheel path, 6
bars per lane, 12” spacing
• 14” min. length
Pavement
Thickness (in.)
Dowel Diameter
(in.)
8 1.0
8 to 9.5 1.25
> 10” 1.5
46
Dowel Bar Retrofit
47
Dowel Bar Retrofit
Diamond Grinding and Grooving
43
Diamond Grinding and Grooving
Preservation Guide:
• Diamond Grinding Heads
• Information on Slurry Management
• Update on Equipment Capabilities
• Next Generation Concrete Surface
49
New Surface Textures
• Optimized Texture for City
Streets (OTCS)
– Similar to diamond
grinding but reduced land
heights/widths
• Next Generation Concrete
Surface (NGCS)
– Manufactured, low-noise
surface consisting of
flush grinding and
grooving
OTCS
NGCS
50
Preservaion Treatments
51
THANK YOU!
National Concrete Pavement
Technology Center
52
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