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?

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• 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

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* CP Tech Center Values Adapted from Table 3.2 Preservation Guide

Start Programming

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Treatment Performance Life

8 - 15

8 - 15

12 - 20

15 - 25

15 - 20

* CP Tech Center (adapted from Preservation Guide)

*

*

*

*

*

Order of Operations

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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

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Types

• Volumetric changes (concrete)

• Volumetric changes (subgrade)

• Settlement and poor support

• Slab length

• Sawing practices

• Traffic loading (design)

• Sympathy cracks

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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

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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

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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

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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.

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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

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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

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Faulting - Causes

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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

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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

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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

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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

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Preservaion Treatments

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THANK YOU!

National Concrete Pavement

Technology Center

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