1. Streets and Local Roads
Proper Design Details for PCC Pavement
Performance
Mike Byers
Indiana Chapter – American Concrete Pavement
Association
2. Streets & Local Roads
Chapter/States Associations of ACPA
North
Dakota
Northwest
Minnesota
Wisconsin
South
Dakota
ColoradoWyoming
Western
States
Utah
Michigan
Iowa
Northeast
Indiana
Illinois
Ohio
Missouri-Kansas
Kentucky
Oklahoma-Arkansas
Southeast
Louisiana
American Concrete Pavement Association
4. Thickness Design Procedures
Empirical Design
Procedures
Based on observed
performance
AASHO Road Test
Mechanistic Design
Procedures
Based on mathematically
calculated pavement
responses
PCA Design
Procedure (PCAPAV)
StreetPave (ACPA
Design Method)
Ottawa, Illinois (approximately 80 miles southwest of
Chicago) between 1956 and 1960
5. New Design Tools for SLR
MEPDG – MechanisticEmperical Design Guide
StreetPave Software
Concrete Thickness
Asphalt Institute Design
Thickness
Life Cycle Cost Analysis
Information Sheet IS184
Thickness Design Manual
for Concrete Streets and
Local Roads EB109
Equivalent Pavement
Design Charts
What’s Equivalent
7. StreetPave Software
Concrete pavement thickness
design based on revised criteria
Asphalt equivalent section based
on converted total carrying
capacity
Life-Cycle cost analysis based on
initial costs of equivalent
pavements and predicted
maintenance
9. How Pavements Carry Loads
7000 lb.
7000 lb.
pressure < 1-3 psi
pressure
≈ 6-10 psi
Concrete’s Rigidness spreads the load over a large area
and keeps pressures on the subgrade low.
10. Comparison of Concrete vs. Asphalt
It’s not the same old
Asphalt and
Concrete anymore!
Just look at the Gas
Pumps!
Gasoline prices are a
good indicator of
what asphalt
pavement cost!
11. Streets and Local Roads Thickness
Design Procedure
Longitudinal joint
Surface smoothness
or rideability
Thickness Design
Transverse joint
Surface Texture
Concrete materials
Dowel bars
Tiebars
Subgrade
Subbase or base
19. SLR Pavement Design
Street classification and
traffic
Geometric design
Subgrades and subbases
Concrete quality
Thickness design
Jointing
Construction specifications
20. Street Class Description
Two-way
Average Daily
Traffic
(ADT)
Two-way Average
Daily Truck
Traffic (ADTT)
Less than 200
2-4
4.0 - 5.0 in.
(100-125 mm)
200-1,000
10-50
5.0 - 7.0 in.
(125-175 mm)
Typical Range
of Slab
Thickness
Light
Residential
Short streets in subdivisions and similar
residential areas – often not throughstreets.
Residential
Through-streets in subdivisions and
similar residential areas that
occasionally carry a heavy vehicle
(truck or bus).
Collector
Streets that collect traffic from several
residential subdivisions, and that may
serve buses and trucks.
1,000-8,000
50-500
5.5 - 9.0 in.
(135-225 mm)
Business
Streets that provide access to shopping
and urban central business districts.
11,000-17,000
400-700
6.0 - 9.0 in.
(150-225 mm)
Industrial
Streets that provide access to industrial
areas or parks, and typically carry
heavier trucks than the business class.
2,000-4,000
300-800
7.0 - 10.5 in.
(175-260 mm)
Arterial
Streets that serve traffic from major
expressways and carry traffic through
metropolitan areas. Truck and bus
routes are primarily on these roads.
4,000-15,000
(minor)
4,000-30,000
(major)
300-600
6.0 - 9.0 in.
(150-225 mm)
7.0 - 11.0 in.
(175-275 mm)
700-1,500
21. Geometric Design
Utilities
Increase Edge Support
Integral Curb
Tied Curb & Gutter
Widened Lanes (2 feet no parking)
Parking Lanes
Rural Areas – Tied Concrete Shoulders
Street Widths
Minimum width of 25 ft.
Maximum Cross Slope of 2 percent
(¼” per ft.)
Traffic Lanes 10-12 feet
Parking Lanes 7-8 feet
22. Subbase vs. NO Subbase
For Concrete Pavements
Subbase
Subgrade
24. Subgrade and Subbases
Subgrade
Natural ground, graded, and
compacted on which the pavement is
built.
Subbase
Layer of material directly below the
concrete pavement.
26. Design for Uniform Support
Three Major Causes for Non-Uniform Support
Expansive Soils
Differential Frost Heave
Pumping (loss of support)
27. Subbase vs. NO Subbase
Presence of fine-grained soil
Presence of water
Sufficient volume of trucks to
cause soil pumping (> 100
trucks/day)
Pavements on > 15% grade
28. Subgrade Properties
Modulus of Subgrade
Reaction, k-value
Plate-Load Test
Reaction
Plate load on subgrade
k = Plate deflection on subgrade
5.0 psi
k = 0.5 in = 100 psi / in.
Stacked Plates
Pressure Gauge
Subgrade
29. Subgrade Properties
Plate-load test is rarely performed
time consuming & expensive
Estimate k-value by correlation to other tests
e.g. California Bearing Ratio (CBR) or R-value tests
Lean concrete subbases increases k-value
substantially
30. Subgrade Properties
Correlated k-values for Subgrade Support
Historical
k-values
(pci)
California
Bearing Ratio
(CBR), %
Resistance
Value
(R-value)
(ASTM D 1183)
(ASTM D 2844)
Low
75 - 120
2.5 - 3.5
10 - 22
Sand and sand-gravel
with moderate
silt/clay
Medium
130 - 170
4.5 - 7.5
29 - 41
Sand and sand-gravel
with little or no
silt/clay
High
180 - 220
8.5 - 12
45 - 52
Type
Fine-grained with
high amounts of
silt/clay
Amount of
Support
31. Subgrade and Subbases
Design Summary
Subgrade strength is not a critical element in the
thickness design.
Has little impact on thickness.
Need to know if pavement is on:
Subgrade (k ≈ 25 MPa/m (100 psi/in.)),
Granular subbase (k ≈ 40 MPa/m (150 psi/in.)),
Asphalt treated subbase (k ≈ 80 MPa/m (300 psi/in.))
Cement treated/lean concrete subbase (k ≈ 125 MPa/m
(500 psi/in.)).
32. Subgrade and Subbases
Performance Summary
Proper design and construction are absolutely necessary
if the pavement is to perform.
Must be uniform throughout pavement’s life.
Poor subgrade/subbase preparation can not be overcome
with thickness.
Any concrete pavement, built of any thickness, will have
problems on a poorly designed and constructed subgrade
or subbase.
33. Subbase Effects
At the AASHO Road Test,
concrete pavements with
granular bases could carry
about 30% more traffic.
The current design procedures
allows concrete pavements built
with granular bases to carry
about 5 - 8% more traffic.
34. Drainable Subbase??
Aggregate Quality – marginal Dcracking?
Traffic Level – high volume may
warrant drainable subbase
Edge drains behind curb still
good detail
35. Concrete Quality
Portland Cement
Materials
Supplementary
Cementitious Materials
Aggregates
Chemical Admixtures
Water
Testing
36. Concrete Quality
Recommended Air Contents for Durable Concrete
Maximum size aggregate
Total target air content, percent *
Severe
Exposure
Moderate
Exposure
in.
mm
3/8
9.5
7.5
6
1/2
12.5
7
5.5
3/4
19.0
6
1
25.0
6
4.5
1½
37.5
5.5
4.5
2
50.0
5
4
Suggest 6.5
5
37. Concrete Quality
Maximum Permissible Water-Cement Ratio for Durable
Concrete Pavement
Type of exposure
Freezing/thawing
with deicing chemicals
Severe sulfate exposure
[water-soluble sulfate (SO4) in
soil > 0.20 % by weight]
Moderate sulfate exposure
[water-soluble sulfate (SO4) in
soil of 0.10 to 0.20 % by
weight]
Maximum water-cementitious
ratio by weight
0.45
INDOT max 0.42
0.45
0.50
41. The latest design and cost analysis tool from ACPA…
Determine and compare thickness requirements and costs
for concrete and asphalt pavements using StreetPave.
Features:
Updated mechanistic design method for concrete pavement
Fatigue and erosion analysis
Jointing spacing & load transfer recommendations
Thickness rounding and reliability considerations
Analysis of existing concrete pavements
Asphalt design based on the Asphalt Institute method
Comparison to equivalent concrete pavement
Life cycle cost analysis module
Printable summary reports and charts
Design summary
Design factor sensitivity & life-cycle plots
User-friendly format and features
Walkthrough Wizard
Help information for all inputs
Compatible with Windows™ 95, 98, NT, 2000, XP
42. Thickness Design for Streets and Local Roads
StreetPave User Inputs & Outputs
Global Settings
Region
Units (English or Metric)
Terminal Serviceability
Percent Slabs Cracked at end
of design Life
Design Life
Reliability
Traffic
Pavement Properties
Thickness/Dowel/Jointing
Recommendations
44. Thickness Design Procedure
Design controlled
by:
Fatigue usually controls design of light-traffic
pavements
Single-axles usually cause more fatigue damage
Erosion usually controls design of undoweled
medium- and heavy-traffic pavements
Tandem-axles usually cause more erosion damage
Tridem-axles usually cause more erosion damage
45. Thickness Design Procedure
Concrete Properties
Flexural Strength
(Modulus of Rupture,
ASTM C 78)
Third-point Loading
Avg. 28-day strength in
3rd-point loading
d=L/ 6
Other Factors
Concrete Strength Gain
with Age
Fatigue Properties
L/3
Span Length = L
51. Design Period/Life
20 to 35 years is commonly used
Shorter or longer design period may be
economically justified in some cases
High performance concrete pavements
Long-life pavements
A special haul road to be used for only a few years
Cross-overs
Temporary lanes
52. Design Reliability
Practically everything associated with pavement
design is variable
Variability in mean design inputs—traffic, materials,
subgrade, climate, and so on
Error in performance prediction models
In StreetPave design, the fatigue variability can be
modeled and applied as an adjustment factor
53. Reliability
Levels of Reliability for Pavement Design
Functional Classification of
Roadway
Recommended Reliability
Urban
Rural
Interstates, Freeways, and
Tollways
85 - 99
80 – 99
Principal Arterials
80 - 99
75 – 95
Collectors
80 - 95
75 – 95
Residential & Local Roads
50 - 80
50 – 80
54. Thickness Design
Combined Reliability & Slabs
Cracked Spreadsheet
Recommended Levels of Slab Cracking by Roadway Type
Roadway Type
Recommended Percent of
Slabs Cracked at End of
Design Life
(Default)
15%
Interstate Highways, Expressways,
Tollways, Turnpikes
5%
State Roads, Arterials
10%
Collectors, County Roads
15%
Residential Streets
25%
55.
56.
57.
58.
59. Basics of Thickness Design
Deflection / Erosion
Higher k-value will lower
deflections
Load transfer will lower
deflections
60. Concrete Pavement Design
For Municipal Streets
Load Transfer (slabs ability to share its load with neighboring slabs)
Dowels
Aggregate Interlock
Edge Support
Tied curb & gutter
Integral curb & gutter
Parking lane
Tied concrete
L= x
U= 0
Poor Load Transfer
=
L x/2
Good Load Transfer
U= x/2
61. Dowels vs. NO Dowels
Load Transfer
L=
x
U=
0
The slabs ability to share its
load with its neighboring
slab
Dowels
Poor Load Transfer
High Traffic Volumes
(Pavements > 8 in.)
(> 120 Trucks/day)
Aggregate Interlock
L=
x Good Load Transfer
U=
x
Low Traffic Volumes
(Pavements < 7 in.)
62. Load Transfer Efficiency
Load Transfer Mechanism LTE, %
aggregate interlock
stabilized base
dowel bars
30 - 80
50 - 90
80 - 95
65. Design - Erosion
Conditions for Pumping
Subgrade soil that will go into
Suspension
Free water between slab and
subgrade
Frequent heavy wheel loads /
large deflections
66. Dowel bars
Lengths from 15-18 in.
6.0 in. min. embedment
length
Diameter
1.00 - 1.25 in. for SLR
Epoxy or other coating
used in harsher climates
for corrosion protection
67. Dowel Recommendations
Dowels recommended when
ADTT is greater than or equal to
80:
If pavement thickness is 6” or less
dowels not recommended
If pavement thickness is 6.5” to 7.5” use
1” dowels
If pavement thickness is 8” or greater
use 1¼“ dowels
68. Faulting Model
Faulting, in
0.20
Dense-graded base
No dowel
0.15
Permeable base
No dowel
0.10
Dense-graded base
1-in dowel
0.05
0.00
0
Dense-graded base
1.25-in dowel
5
10
15
Traffic, million ESALs
20
69. Construction of Concrete Pavement
Plant Operations
Central Mixed Concrete
Plant Operations
Truck Mixed Concrete
Paving Operations
Slipform Paving
Paving Operations
Fixed Form Paving
Saw & Seal
Central Mix Concrete Batch Plant
72. Curing
Curing is one of the most
important steps in quality
concrete construction and
one of the most neglected.
Effective curing is
absolutely essential for
surface durability.
Durability = resistance to
73. Curing
Curing requires adequate —
Moisture
Temperature
Time
If any of these factors are
neglected, the desired
properties will not develop
75. Curing
The simplest, most economical and
widely used method is a liquid
membrane which is sprayed on the
surface of a slab as soon as possible after
finishing.
Apply at manufacture’s rate of
coverage.
Perform field check to verify application
rate.
78. The latest design and cost analysis tool from ACPA…
Determine and compare thickness requirements and costs
for concrete and asphalt pavements using StreetPave.
Features:
Updated mechanistic design method for concrete pavement
Fatigue and erosion analysis
Jointing spacing & load transfer recommendations
Thickness rounding and reliability considerations
Analysis of existing concrete pavements
Asphalt design based on the Asphalt Institute method
Comparison to equivalent concrete pavement
Life cycle cost analysis module
Printable summary reports and charts
Design summary
Design factor sensitivity & life-cycle plots
User-friendly format and features
Walkthrough Wizard
Help information for all inputs
Compatible with Windows™ 95, 98, NT, 2000, XP
79. SLR Publications
Information SheetMaturity Testing of ConcreteInformation Sheet- (IS
Concrete Pavement for
GA Business &Commuter
Aircraft
Information SheetLongevity and Performance
of DG Pavements
Information SheetSpecification Guideline for
Dowel Bar Retrofit
www.pavement.com
Engineering Bulletin- (EB
Early Cracking Causes/Solutions
Engineering Bulletin-(EB
The design tools are primarily intended for concrete pavement designs for new construction for all categories of streets and local roads pavements.
These are base on the PCAPAV “Thickness Design for Concrete Highway and Street Pavements (SLR Only) and the accompanying software. These projects are budgeted for 2004 but work is currently underway. The thickness guide will be primary a rewrite of our current metric version for SLR pavements only.
The equivalent design charts are tools requested during the Chapter/State meetings and is a simple comparisons of equivalent Concrete to Asphalt cross sections incorporating the Structural Number concept.
Reproducing the graphics from ENR demonstrating the cost increase of Asphalt vs. the Cost Increase of Concrete
Notes:
Utilities should be located outside pavement structure whenever possible.
StreetPave treats each of the above category the same for additional edge support and typically will reduce the cross-sectional thickness by approximately 1 inch.
Pavement lane widths greater than 14 (stripped) may cause drives to try and pass, especially on the right.
Parking lanes of 6 ft. are not recommended.
As well as being Drainable and Compactable
When a pavement is subjected to traffic loadings the pavement reacts by bending and creating both compressive and flexure stresses. Since the Stresses ratio is much greater for flexural than compressive, the flexural strength governs the thickness design
When a pavement is subjected to traffic loadings the pavement reacts by bending and creating both compressive and flexure stresses. Since the Stresses ratio is much greater for flexural than compressive, the flexural strength governs the thickness design
Source (Modeled after) RD102, Evaluation of the Long-Term Properties of Concrete, by Sharon Wood.
Fig. 1-14. Concrete strength gain versus time for concrete exposed to outdoor conditions. Concrete continues to gain strength for many years when moisture is provided by rainfall and other environmental sources (Wood 1992).
The American Concrete Pavement Association design procedure incorporates reliability as an input variable. Reliability, simply stated, is the factor of safety of the pavement design. It is a measure of how likely the specified design will perform before “failure.” This design procedure predicts when the pavement will “fail” either due to fatigue (a crack will form) or erosion (the subgrade material will pump out from underneath the pavement).
The recommended level of reliability depends on the type of roadway that is being designed. A relatively high reliability is used for high-traffic, high-speed roadways, while low-traffic, low-speed roads typically need a low level of reliability. The importance of this innovation is that it allows the design professional to use lower levels of reliability to produce design thicknesses more practical for streets and local road design. Table 12 lists the recommended reliability levels for roadway design, dependent on the classification of the facility.
The design tables 13(a) and 13(b) were developed using a reliability value of 80 percent, which is common for most street and local road applications and takes into account the variations in materials and layer thicknesses for each traffic category.
The design procedure also incorporates the amount of slab cracking as another factor used to evaluate the predicted long-term pavement performance. Primarily, this factor assists in planning future maintenance or pavement preservation activities at the end of the pavement’s design life. For Tables 13(a) and 13(b), the percent slabs cracked at the end of the design life was set at 15 percent for all roadway classifications, which reduces the overall repairs required to extend the pavement service life past the design period. For additional information on concrete pavement preservation or restoration, see American Concrete Pavement Association publication The Concrete Pavement Restoration Guide, Reference 9.
Emphasize that:
Adequate load transfer reduces vertical movement at the joints, minimizing joint-related distresses.
Typical load transfer mechanisms are aggregate interlock and dowel bars. Also, stabilized bases can be used to reduce to potential of pumping
Note to the speaker: Stabilized bases are developed using procedures and techniques by which otherwise unsuitable soils may be improved. In many instances, the existing subgrade soils are unsatisfactory in their natural state but can be altered through stabilization to improve the material properties to meet the requirements of subbase and base layer materials. In some instances, stabilized bases are used to improve the structural integrity of the pavement layers supporting the pavement surface.
Many factors influence the type of stabilizing material selected for a particular project, such as the type of soil. In addition, different stabilizers are used for different reasons, such as strength gain, waterproofing, or water retarding. Therefore, some stabilizing materials are more appropriate for a given soil type than others. Stabilizing admixtures include cement, lime, lime flyash, bitumen (asphalt), and calcium or sodium chloride.
The use of edge support will reduce the stresses at the pavement edge and reduce the overall cross-sectional thickness. In residential and collector, and minor arterials this would typically be 1 inch major arterials this thickness reduction is approximately 1.5 inches.
These are the expected average performance ranges of load transfer efficiency for highway pavements over the life of the pavement for each load transfer mechanism listed. The load transfer performance will depend on the selected materials and the quality of construction within a given project.
As you can see from these ranges, dowel bars provide the best and most reliable load transfer.
Note: Due to rounding at a thickness of 6.01 inches the recommended thickness is rounded up to the nearest 0.5 inch 6.5 inches. In these cases, dowels may or may not be recommended. The use of a non-pumping subgrade/subbase could be used in place of 1” dowels.
0.10 in of faulting typically becomes uncomfortable to the driving public, as well as the vehicular commerce, and triggers rehabilitation.
The “beige” faulting trend increases very rapidly as ESALs accumulate.
The “orange” faulting trend is similar.
The “light blue” trend becomes uncomfortable around 15 million ESALs.
The “dark blue” trend remains well below the uncomfortable threshold for rehabilitation.
Therefore, dowels reduce faulting better than nondoweled JPCP or permeable bases.
Faulting is just one of the distresses caused by poor load transfer.
Fig. 11-22. An excellent method of wet curing is to completely cover the surface with wet burlap and keep it continuously wet during the curing period. (69946)
Fig. 12-1. Curing should begin as soon as the concrete stiffens enough to prevent marring or erosion of the surface. Burlap sprayed with water is an effective method for moist curing. (69973)
It is vital to our program for people to get involved in the Streets and Local Roads program. The SLR subcommittee will met twice in 2004. These meetings are where key areas of our promotion initiative are discussed and future products/programs are outlined. Get involved!