9. SO, WHAT ARE WE DOING
ABOUT IT?
WE’RE WORKING IN PARTNERSHIP TO
DEVELOP STRATEGIES AND
GUIDELINES FOR PROJECT SPECIFIC,
COST EFFECTIVE CONCRETE
SOLUTIONS.
15. WT BOL UBOL
Secondary 1177.6 88.4 490.5 1756.5
Primary 81.8 52.7 160.7 295.2
1259.4 141.1 651.2 2051.7
miles
Municipal 300,000 SY
(approximate)
Airport 739,840 SY
(24 Runways)
16.
17. CONTENTS
1. Overview of Overlay
Families
2. Overlay Types and Uses
3. Evaluations & Selections
4. Six Overlay Summaries
(11”x17 “sheets)
5. Design Section
6. Miscellaneous Design
Details
7. Overlay Materials Section
8. Work Zones Under Traffic
9. Key Points for Overlay
Construction
10. Accelerated Construction
11. Specification Considerations
12. Repairs of Overlays
18. CONCRETE OVERLAYS
Bonded
Concrete
Overlay of
Concrete
Pavements
Bonded
Concrete
Overlay of
Asphalt
Pavements
Bonded
Concrete
Overlay of
Composite
Pavements
Bonded Overlay System
Unbonded
Concrete
Overlay of
Concrete
Pavements
Unbonded
Concrete
Overlay of
Asphalt
Pavements
Unbonded
Concrete
Overlay of
Composite
Pavements
Unbonded Overlay System
Thinner Thicker
BOND IS INTEGRAL TO DESIGN OLD PAVEMENT IS BASE
19. Not a new design procedure!
Background of recommended
overlay design techniques
Detailed examples of how to
use the existing design
methodology
Learn by example – then apply
for your situation!
http://www.cptechcenter.org
20.
21. Check Out
PavementDesigner
Pavement Design Simplified
for:• Streets and Roads
• JPCP
• RCC
• CRCP
• Overlays
• Parking Facilities
• Intermodal Yards
FREE Pavement
Design Program
26. ACKNOWLEDGEMENTS
Full Report: Performance of Concrete Overlays in
Iowa
Phase I of Iowa Highway Research Board TR-689
Project Team:
CP Tech Center: Jerod Gross, Dale Harrington, Dr.
Peter Taylor
Iowa State University: Yu-An Chen, Dr. Halil
Ceylan, Inya Nnelanya, Dr. Omar Smadi
27. CONCRETE OVERLAYS IN IOWA
Iowa: over 2,000 centerline miles of concrete
overlays have been constructed since the late ‘70s
Over half constructed since 2005
Mostly on county highway system
28. PROJECT BACKGROUND
How well have Iowa’s overlays
performed? (How long do they last?)
Approximately 470/506 overlay
projects are still in service today
Includes 68/96 constructed before
1990
Compare to older sources that
indicate expected service life for a
concrete overlay is only about 20
years Dallas County, IA, Constructed 1977
29. PROJECT BACKGROUND
However, as of 2015, there had been no attempt to
characterize performance of overlays to determine
expected service life & what made projects successful
Dallas County, IA, Constructed 1992
30. PROJECT OBJECTIVES
Define performance of Iowa’s concrete overlays
Create performance curves
Analyze specific design choices and characteristics and
link to performance
Overlay type (thin bonded, unbonded)
Thickness
Joint spacing
Traffic
Incorporate lessons learned to improve overlay design and
performance
31. DATA COMPILATION & COLLECTION
Automated pavement condition
data: Iowa Pavement Management
Program (IPMP)
Opt-in program for local agencies
Data collection began in early
2000s (opt-in)
Since 2013, all streets & roads
are covered every other year
This data then combined with
ICPA overlay project records to
produce the complete data set
32. OVERLAY TYPES
Bonded Concrete Overlay of Concrete (BCOC)
Bonded Concrete Overlay of Asphalt (BCOA)
Defined as thickness ≤ 6 inches
Unbonded Concrete Overlay of Concrete (UBCOC)
Unbonded Concrete Overlay of Asphalt (UBCOA)
Defined as thickness > 6 inches
33. DATA DISTRIBUTION
Typical designs in Iowa
Early on: 6 inches on asphalt
(“whitetopping”) or 6+ inches
unbonded on concrete
Performance data for
projects up to 40 years old
Washington County, IA, Constructed 1977
34. DATA DISTRIBUTION
Typical designs in Iowa
‘00s: more types of
projects, including
thinner overlays
Advent of new design
procedures, shorter slabs,
fiber-reinforcement
About 10 years worth of
data, with some
exceptions
Boone, IA, Constructed 2005
52. RESULTS AND ANALYSIS
Key findings and trends:
Overall performance of Iowa’s concrete overlays has been
excellent
As a whole: about 35 years to PCI = 60
About 40 years to IRI = 170 in/mi
Good performance from each of BCOA, UBCOA & UBCOC
Overlays of asphalt slightly better than UBCOC
BCOC less successful overall, but performed well in context of
design life expectations
53. RESULTS AND ANALYSIS
Key findings and trends:
Thickness
In general: thicker overlays have performed better for all overlay
types (e.g. for BCOA, 6” > 5” > 4”)
Transverse joint spacing
Good early performance from short slab designs (6”) on BCOA/thin
overlays
Older designs with 15-20 foot slabs performed well long-term
12 foot slabs—inconclusive
Traffic—inconclusive
Most of these projects are low-volume, <1,000 vpd
Not enough truck traffic data available from local agencies
54. RESULTS AND ANALYSIS
12 foot transverse joint spacing
Across multiple splits, apparent decline in performance of
overlays with 12 foot joint spacing (even compared to
longer spacings)
UBCOA (organized by joint spacing):
Figures: Chen and Ceylan
55. FIELD REVIEWS
Field reviews were performed to:
supplement data analysis
verify findings
investigate trends, outliers
Pottawattamie County, IA, Constructed 1993
56. FIELD REVIEWS
Observed distresses:
Materials-related
Pottawattamie County, IA, Constructed 1999
57. FIELD REVIEWS
Observed distresses:
Rough ride—construction or curling/warping
Occasional faulting
Buchanan County, IA, Constructed 1996
58. FIELD REVIEWS
Observed distresses:
Load-related, possibly mis-designed
or under-designed
Dallas County, IA, Constructed 2006
59. FIELD REVIEWS
Key takeaways:
Observed performance generally matches data
Poor performing outliers & early failure causes:
Materials-related
Load-related/under-design
Rough ride
In short... mostly the same issues that we run into with
conventional PCC pavements
Be aware of increased potential for curling/warping
Beyond above explanations, no direct observations to indicate that
there’s a specific problem with 12 ft joint spacing design
60. CONCLUSIONS
Overall performance of Iowa’s concrete overlays has
been excellent
Upwards of 30-40+ year performance life
Overlays are very well-suited to county highways
Good success to date on interstate, state highways, and
city streets as well
61. NEXT STEPS
Move from performance history → survivability, performance
models
Continue compiling data, keeping the database updated
Le Mars, IA, Constructed 2017
65. NORTHBOUND US 81 NEAR STRANG AND BELVEDERE, NE
8” UNBONDED PCC OVERLAY (1982 AND 1984)
65
66. US 30 BETWEEN LEXINGTON AND COZAD, NE
5” UNBONDED OVERLAY OVER ASPHALT OVER OLD
PCC (2015)
66
67. A 6-INCH UNBONDED OVERLAY OVER FULL-DEPTH HMA
PLACED IN 2010 IN PIERCE COUNTY ON 556TH
STREET
JUST NORTH OF NORFOLK, NEBRASKA
67
68. CELEBRATING 50 YEARS OF LEADERSHIP AND SERVICECELEBRATING 50 YEARS OF LEADERSHIP AND SERVICE
I-70I-70
Western KansasWestern Kansas
6x6x6 Concrete Overlay6x6x6 Concrete Overlay
THIS ISTHIS IS
RESURFACING!RESURFACING!
But it wasn’t always concrete – in the 20s – we had to “get out of the mud”!
Our first concrete street was built in LeMars in 1904
Allow me to offer some brief insight to Iowa’s paving market as we prepare to look at proven cost effective pavement resurfacing solutions.
And our focus on what need’s to be done has changed, too. No longer building new roads, but taking care of what is out there.
Overlays on concrete, on asphalt, on composites, designed as bonded or unbonded, we’ve proven that we can effectively address all of these needs
The proof of the overlay success in Iowa.
See how the overlay is becoming more important to our future?
There is ongoing work to update and finish this document (explained later in this presentation), but it will be released early in 2012.
From ACPA’s overlay explorer. IA = about 1/3 of all overlay projects nationwide
Note two projects—same county, one failed in ~25 years, another going on 40 yrs old with no plan to replace
Briefly cover different overlay types. Note difference in thickness and joint spacing between different overlay types.
We have some older 3-5” PCC overlays, but newer short slab designs only really started appearing in ‘00s
Almost half of all projects are 6” overlays; thinner (4-5”) now account for close to 1/3 of total overlay mileage
Faulting is indirectly measured via IRI
PCI = 60 is where condition changes from ‘good’ to ‘fair.’ ‘Poor’ condition doesn’t actually begin until PCI = 40Performance plot of PCI vs. age for all concrete overlays. (Includes all types of overlays, all thickness, joint spacing, etc.) Key point of emphasis here is that the majority of concrete overlays are on track to fulfill a very good long-term service life. The trendline reaches a PCI of 60 at 35 years. Variability in the data means that you can’t directly infer a 35 year performance life for all concrete overlays, but projects are clearly performing well—certainly the vast majority are lasting longer than 20 years. (May also note here that PCI = 60 is where condition changes from ‘good’ to ‘fair.’ ‘Poor’ condition doesn’t actually begin until PCI = 40.)
PCI for BCOA projects only. This slide is here primarily to give a “sneak peek” at how many different plots/charts are available in the full report, breaking down the data into smaller groups and offering comparisons. One thing you can note here is that thicker BCOA projects (5-6 in.) have shown better long-term performance than thinner BCOA projects (4 in.). Although the more modern thin overlay designs only have data for about 10 years or so.
This slide makes performance of newer, short slab designs more clear. Also you can see kind of an outlier with 12 ft joint spacing performance. Similar to prior slide, but now BCOA performance is sorted by joint spacing as opposed to thickness.
Another sneak peek slide, this time for thick “unbonded” overlays of asphalt. Shows very good long term performance of 7 and 8 inch overlays.
Somewhat worse observed performance than our bonded and unbonded overlays of asphalt—except for very thick design (interstate)
Performance plot of IRI vs. age for all overlays. (Includes all types of overlays, all thickness, joint spacing, etc.) The reason a line is drawn at IRI = 170 in/mi is because that is FHWA’s standard for when ride quality becomes “not acceptable.” Like previous slide, data demonstrates great long-term performance of overlays in terms of ride quality. Trendline intersection appears to be at approx. 40 years, although same caveat applies.
So among thin overlays, the relatively thicker ones have had the longest performance life
Greater susceptibility for curling and warping on overlays—more surface area relative to volume of slab.
Maybe not just under-designed but also poor choice of slab size. Smaller slabs would have mitigated stresses.