This document provides an overview of a workshop on two-lift concrete paving held on May 23, 2013. It discusses the background and motivation for using two-lift paving, including allowing the use of lower-quality aggregates in the bottom layer while maintaining high-quality surface characteristics in the top layer. The document summarizes experiences with two-lift paving in Europe and the US and reviews the construction process and considerations. It outlines the tasks of a research project evaluating the feasibility and cost-effectiveness of two-lift paving for Texas, including literature reviews, contractor surveys, and cost analyses.
5. What is two-lift paving?
Placing two layers of concrete, wet on wet, rather than
the usual single lift of concrete.
Bottom layer is much thicker, e.g. 8 or 9 in, and the top
layer is much thinner, e.g. 2 or 3 in.
Bottom layer can contain aggregates that are not suitable
for top layer.
Top layer contains better quality aggregates
5
6. Major benefits
1. Permits concrete with lower unit cost to be used
for lower layer
significant amounts of local materials including aggregates
that are inappropriate for surface courses including
recycled and high CTE coarse aggregates and carbonate
fine aggregates which reduces transportation
Lower cement contents
Higher amounts of supplementary cementitious materials
6
7. 2. More efficient and economical use of specialized
mixtures to produce desirable surface characteristics
for top layer
Improved skid resistance
Reduced noise
Improved durability
7
8. Importance to TxDOT
Some areas including Dallas and Fort Worth are faced
with depleting sources of quality natural silica sands.
The carbonate manufactured sands make good concrete
but are not suitable for concrete pavement surfaces due
to polishing.
Fine aggregates have the greatest influence on skid resistance in
concrete pavements.
Softer carbonate fines tend to polish faster than harder silica
aggregates
8
9. Skid Resistance – Aggregate Test
The test adapted by most highway state agencies is the
acid insoluble residue test (AI).
It was originally 28% in Texas and effectively omitted all
carbonate fine aggregates.
When the specifications were rewritten in 1993, the limit
was set at 60% because that was representative of the
value used by the districts.
99
10. Skid Resistance – AI Test
The minimum acid insoluble residue limit in Texas was
originally 28%.
This limit effectively omitted all carbonate fine
aggregates.
Between 1982 and 1993, some districts had started
using higher requirements by plan note.
When the specifications were rewritten in 1993, the
limit was set at 60% because that was representative
of the value used by the districts.
1010
11. Skid Resistance – Fine Aggregates
11
Hard siliceous FA
Original Section
Abraded Section
Soft limestone FA
Texture created by finishing technique
11
18. What is the implication for two-lift paving?
100% carbonate fine aggregates can’t be used.
Blending may permit up to 60% carbonate fines in top lift
and 100% in bottom lift.
18
19. Reduction in amount of natural sand
For single lift 100% natural sands = 100% N.S.
For two lift, 10” bottom lift and 2”
top lift using 100% natural sand
= 2/12 x 100 = 16.7% N.S.
For two lift with 40% N.S. and 60%
MFA for 2” top lift = 0.4 x 16.7 = 6.7% N.S.
19
20. What we hope to learn
Under what conditions is two-lift paving appropriate for
Texas?
This involves many factors:
Economics
Materials
Equipment
Construction
Specifications
20
22. Project Tasks
Project 0-6749: Feasibility Study of Two-lift Concrete
Paving
Task 1 Literature survey of past experience of 2LCP
Task 2 Evaluation of the state-of-the-practice of 2LCP
Task 3 Summary of construction perspectives of
implementation of 2LCP
Task 4 Cost effectiveness analysis and best practice of
2LCP
22
23. Task 1 Literature survey of past experience of
2LCP
23
Task 1.1 Summary of previous experiences and past
performance of 2LCP
Task 1.2 Summary of potential benefits, challenges
and cost effectiveness of 2LCP
24. Task 1.1 Summary of previous experiences
and past performance of 2LCP
24
Year
Country
/State Highway/Location EAC?
Length
(mi.)
Traffic
(ADT) References
EuropeanExperience
1989 Austria Freeway A1 Y NA (Tompkins 2009) (SHRP2)
1994 Austria A1 near Eugendorf Y NA 56,000 (Tompkins 2009) (SHRP2)
1994 Austria A1 near Traun Y NA 55,000 (Tompkins 2009) (SHRP2)
1999 Austria A1 nearVorchdorf Y NA 56,000 (Tompkins 2009) (SHRP2)
2003 Belgium N511 at Estaimpuis* Y 0.8 2,000 (Debroux 2005)
2005 Belgium E34 motorway in Zwijndrecht * 1.9 (Rens 2008)
2008 Germany A6 Near Amberg Y 13 80,000 (Tompkins 2009) (SHRP2)
NA France Highway A71 NA (Cable 2004)
NA Germany Munich Airport NA (Cable 2004)
USExperience
1976 Iowa US 75 NA (Bilec 2010)
1976 North Dakota US 2 b/w Rugby and Leeds NA (Bilec 2010)
1977 Florida US 41 2.5 (Bilec 2010) (Cable 2004)
1994 Michigan I-75, NB Y 1 (Smiley 2010) (Bilec 2010)
1997 Kansas NA Y
0.7
(Cable 2004) (Wojakowski 1998)
0.4
0.8
2008 Kansas I-70 in Saline County Y 5 (Fick 2009) (CP Road Map 2010)
2008 Pennsylvania Mon-Fayette Expressway NA (Bilec 2010)
2010 Minnesota
I-94, Cell 71 Y NA 27,500
(Akkari 2011) (Tompkins 2011)I-94, Cell 72 Y NA 27,500
2012 Illinois Tollway 4.2 (Gillen 2012)
Avg 3.03 43,429
*CRCP section
25. Task 1.1 Summary of previous experiences
and past performance of 2LCP
25
Year
Country
/State Highway/Location
Bottom Lift
Thicknes
s (in.) Aggregate
Slump
(in.) Air (%)
Strength
(psi)
EuropeanExperience
1989 Austria Freeway A1 8.5 RCA and RAP
1994 Austria A1 near Eugendorf 8.3 RCA, MSA 1.26"
1994 Austria A1 near Traun 7.9 RCA, MSA 1.26"
1999 Austria A1 nearVorchdorf 8.3 RCA, MSA 1.26"
2003 Belgium N511 at Estaimpuis* 6 Porphyry 0.59 5
2005 Belgium E34 motorway in Zwijndrecht * 7 Broken stone, max 60% RCA
2008 Germany A6 Near Amberg 10 River gravel
NA France Highway A71 NA Local limestone
NA Germany Munich Airport 9.5 Local gravel
USExperience
1976 Iowa US 75 9 60% RCA, 40% RAP
1976 North Dakota US 2 b/w Rugby and Leeds 6 NA
1977 Florida US 41 9 Limestone
1994 Michigan I-75, NB 7.5 Dolomitic limestone 5000
1997 Kansas NA
7 15% RAP
7 High abs. limestone
7 Limestone & pea gravel
2008 Kansas I-70 in Saline County 11.8 Limestone 1.3 7
2008 Pennsylvania Mon-Fayette Expressway 8 NA
2010 Minnesota
I-94, Cell 71 6 50% RCA, 1
I-94, Cell 72 6 Relaxed agg. Grad. 1
2012 Illinois Tollway 8 RAP& CM-11 Limestone 3 6.5 3500
Avg 7.9 1.4 6.2 4250
26. Task 1.1 Summary of previous experiences
and past performance of 2LCP
26
Year
Country
/State Highway/Location
Top Lift
Thickne
ss (in.) Aggregate
Slump
(in.)
Air
(%)
Strengt
h (psi)
EuropeanExperience
1989 Austria Freeway A1 1.6 Harder aggregate
1994 Austria A1 near Eugendorf 1.6 Diabase aggregate, MSA 0.31"
1994 Austria A1 near Traun 2 Diabase aggregate, MSA 0.43"
1999 Austria A1 nearVorchdorf 2 Diabase aggregate, MSA 0.43"
2003 Belgium N511 at Estaimpuis* 2 Porphyry 1.2 4
2005 Belgium E34 motorway in Zwijndrecht * 2 Broken stone, with polishing resistance requirement
2008 Germany A6 Near Amberg 2 Crushed granite, gap-graded, MSA 0.31"
NA France Highway A71 2 Harder aggregates
NA Germany Munich Airport 5.5 Crushed granite
USExperience
1976 Iowa US 75 4 All virgin materials
1976 North Dakota US 2 b/w Rugby and Leeds 3 Crushed rock and sand
1977 Florida US 41 3 Limestone
1994 Michigan I-75, NB 2.5 Ontario trap rock (crushed basalt) 5500
1997 Kansas NA
3 Limestone
3 Rhyolite
3 Limestone & pea gravel
2008 Kansas I-70 in Saline County 1.6 Rhyolite 1.9 7.5
2008 Pennsylvania Mon-Fayette Expressway 4 NA
2010 Minnesota
I-94, Cell 71 3 ½” and 3/8” W. Chips Granite 1 5600
I-94, Cell 72 3 ½” W. Chips and 3/8” W. Chips 1 5600
2012 Illinois Tollway 3.5 CM-11 Limestone 3 6.5 3500
Avg 2.7 1.62 6 5050
27. Task 1.2 Summary of potential benefits,
challenges and cost effectiveness of 2LCP
27
Additional requirements for 2LCP
Time lag between lifts (up to 30 mins/ 30-60 mins)
Additional mixing plants (drums), paving machines, belt
placer and extra trucks.
Additional crew members and better trained workforce
Well organized jobsite and scheduling of operating additional
equipment
Bottom lift concrete was placed with spreader, spreader box,
Rex Belt placer, or two belt spreader.Top lift was placed
with slip-form paver in every project.
28. Task 1.2 Summary of potential benefits,
challenges and cost effectiveness of 2LCP
Benefits of using 2LCP - Use low quality materials in bottom
layer and high quality materials in top layer.
Locally available low quality/high polish materials can be used
in bottom lift. Recycled material can be used.
Top lift is relatively thinner and less high quality aggregate
needed; makes it an economical choice.
Challenges of using 2LCP
Required additional equipment and construction requirements,
including a second paver, second batch plant etc.
Construction scheduling and planning is also considered as a major
challenge to adoption of the 2LCP concept in the United States.
While experiences in Europe shows comparable cost (of 2LCP
comparing to traditional one lift paving), for these experimental
projects the cost of 2LCP was twice than the conventional
concrete pavement.
28
29. Task 2: Evaluation of the State-of-the-
Practice of 2LCP
Task 2.1 Surveys and interviews of contractors and
agencies with experience in use of 2LCP.
Task 2.2 Surveys and interviews of contractors and
TxDOT personnel regarding concerns with 2LCP
Task 2.3 2LCP workshop
29
30. Task 3 Summary of construction perspectives
of implementation of 2LCP
30
Properties of each lift
Material requirements, thickness of two lifts, slump, air
content, set time and permeability
Minimum requirements of material
Aggregate gradation, recycled aggregate limits, admixture
requirements, compressive strength, modulus of rupture and
durability
Surface characteristics
Type of aggregate, skid resistance, friction, noise and splash
31. Task 3 Summary of construction perspectives
of implementation of 2LCP
31
Additional equipment, construction, and scheduling
requirements
a second paving machine
a second batch plant (or second mixer and additional
aggregate bins)
a second belt placer/spreader (in place of a second paving
machine)
extra hauling and extra labor for hauling and running the
second batch plant (mixer) and placer/spreader
32. Task 3 Summary of construction perspectives
of implementation of 2LCP
32
Concerns of Implementation of 2LCP
Extra permits and land space for two paving plants
Well organized jobsite and scheduling of operating additional
mixing plant, paving machines and trucks
Clear definition of “stiff” of bottom lift
Pavement vibration system to minimize potential for
segregation
Minimum thickness of the top lift
Maximum/optimum time lag to eliminate potential
debonding (In K-96 project minimum waiting time of 30
minutes was necessary to prevent mixing of the two lifts. In
the same project, low w/c concrete was used in top lift
without any debonding problem)
Durability (In Florida 23 sections out of 33 sections are still
in service.The other ten sections were removed within 2
years of service. )
33. Task 4 Cost effectiveness analysis and best
practice of 2LCP
Task 4.1 Cost effectiveness of 2LCP
Task 4.2 Feasibility study of the most promising
practice of 2LCP
33
34. Task 4.1 Cost effectiveness of 2LCP
34
Changes (increases) of labor and equipment costs
between two-lift pavements and traditional single lift
pavements need to be quantified to effectively
determine if material and/or life-cycle costs can
offset the additional costs on a project specific basis.
Research team will work with PM & PMC to develop
case studies of potential cost benefit (both
construction cost and life cycle cost) in selected
districts facing aggregate shortages to justify cost
effectiveness.
Also included, will be an analysis of potential
economic benefits of surface improvements.
35. Task 4.1 Cost effectiveness of 2LCP
35
Type of Pavement Thickness Cost of
Materials
(CY)
Pavement
Cost-in-
Place (CY)
Cost of
Pavement
(SY)
Standard Mix 12” $57 $99 $33
Durable Mix 12” $102 $144 $48
Two-
Lift
Bottom-Lift 10” $57 $108 $30
Surface Lift 2” $102 $190 $11
Identifies $/SY of 2LCP to be $8 more than a standard mix and $7
lower than a durable mix. (Hoard 2009)
Case Study - Kansas I-70 2008
36. Task 4.1 Cost effectiveness of 2LCP
Rao S., Darter M.I., Composite Pavement Systems – A Sustainable Approach for Long-Lasting
Concrete Pavements, 10th International Conference on Concrete Pavements, 2012.
Case Study - MnRoad SHRP2 2010
36
37. Task 4.1 Cost effectiveness of 2LCP
Krummen S., Constructing a Composite Pavement from Subgrade Up, 91st AnnualTRB
Meeting, January 22, 2012.
Case Study - MnRoad SHRP2 2010
Conventional Concrete Composite Concrete
Mix Production $5,501,000 $4,850,000
Pavement Placement $809,000 $1,325,000
Total Pavement Cost $6,310,000 $6,175,000
Unit Cost $20.38/sy $19.94/sy
$135,000 Net Cost Advantage
$0.44/cy less
(2% Discount)
37
38. Task 4.1 Cost effectiveness of 2LCP
38
One-Lift Paving
(Local Agg.)
One-Lift Paving
(Imported Agg.)
Two-Lift
Paving
Material
Costs
Top Lift -
Bottom Lift NA NA
Constructi
on Costs
Mixing Plants - -
Pavers - -
Extra
Equipment
- -
Extra Labor - -
Current Costs ?() ? () ? ()
Maintenance Costs ?()
LCC ? ? ?
39. Task 4.2 Feasibility study of the most
promising practice of 2LCP
Research team will provideTxDOT with a recommended best practice
protocol for implementing and managing a cost effected 2LCP project.
39
40. Findings from Tasks 2
Mr. Michael Grams (Texas State University)
Mr. Md Sarwar Siddiqui (CTR, University of Texas)
40
41. Task 2.1 Surveys and interviews of contractors
and agencies experience with 2LCP
Mr. Michael Grams (Texas State University)
41
42. Task 2: Evaluation of the State-of-the-
Practice of 2LCP
Task 2.1 Surveys and interviews of contractors and
agencies with experience in use of 2LCP.
Task 2.2 Surveys and interviews of contractors and
TxDOT personnel regarding concerns with 2LCP
Task 2.3 2LCP workshop
42
43. Task 2.1 Surveys and interviews of contractors
and agencies experience with 2LCP
A detailed sixteen question survey was issued
through Survey Monkey to both domestic and
European contractors, suppliers, researchers, and
Department of Transportation personnel who were
identified through a literature review as having
experience with 2LCP.
The survey was divided into 5 categories that
covered: general information of the respondent, mix
design and material properties, construction, cost, and
overall experience of 2LCP.
Over 100 invitations were sent out. A total of 26
individuals responded and took the survey, including 9
through phone interviews.
43
44. Task 2.1 Personnel Participated Surveys
44
Name Affrications Project
Peter Schöller Österreichische Betondecken Arge Europe
Ronald Blab Vienna University of Technology Austria, Germany and Slowenia
Luc Rens FEBELCEM - EUPAVE Belgium
Thomas Sorel MnDOT MnROAD
Thomas Kazmierowski Ontario Ministry of Transportation Highway 407,Toronto
José Tadeu BALBO USP NA
ArjanVenmans provincie Noord-Brabant The Netherlands Veghel,The Netherlands, secondary road N279
Jussara Tanesi
FHWA-TFHRC-HRDI Aggregate/Petrographic Lab
(APL) Kansas I-70
Ben Worel Minnesota Department of Transportation MnROAD (Interstate - 94)
James Crites Parsons Corp (on behalf of DFW Airport) NA
Richard Abell Highways Agency Kessignland, Suffolk
Mark B Snyder ACPA - PA Chapter Pennsylvania Turnpike - Mon-Fayette Expwy
Mark Watson Minnesota Department of Transportation MnROAD I-94
Suneel N.Vanikar FHWA Several demonstration projects in USA
Denis Thebeau Ministere des transports du Quebec Hwy 15 Mirabel Northboun Quebec Canada
John Donegan Aggregate Industries UK A449 - South Wales, UK
Alfred Weninger-Vycudil PMS-Consult GmbH, Naglergasse 7,Vienna,Austria Austria and Germany
Steven Gillen Illinois Tollway I-88 Illinois Tollway
Robert Rasmussen Transtec I-70, Europe
Jim Grove FHWA Kansas I-70
Tom Cackler CP Tech Kansas I-70
James Cable Cable Construction NA
Gary Fick Trinity Construction Kansas I-70
Tim Gerhardt Koss Construction Kansas I-70
Ron Meskis Gunter & Zimmerman NA
45. Task 2.1 Surveys and interviews of contractors
and agencies experience with 2LCP
45
46. Task 2.1 Survey – General Information
46
Question2: How many years do
you have with paving experience?
Question3: Which of the following
best describe your field of
experience in paving?
Results from 25 valid responses Results from 25 valid responses
4%
0%
8%
88%
0 to 5
6 to 10
11 to 15
Over16
24%
32%
40%
4%
Design
Construction
Research
Equipment
47. Task 2.1 Survey A – General Information/Cost
47
Question5: Major reason for using
2LCP vs. traditional paving??
Results from 22 valid responses
Question11:Which of the
following attributed to the
greatest impact to overall 2LCP
project cost?
Results from 19 valid responses
6%
28%
13%
44%
9%
Agg. Availability
Surface Char.
Economic
Experimentation
Others
0%
66%
3%
8%
13%
10%
Extra Supervision
Extra Equipment
Extra Manpower
Unexpected Expenditures
Preplanning
Others
48. Task 2.1 – General Information/Mix Design &
Materials Properties
48
Lane Mile ADT Top LiftThickness Bottom LiftThickness
Count 8 7 11 10
Max 7450 140000 6.0 8.3
Min 0.19 4000 1.6 6.0
Avg 954 47214 3.0 6.9
Stdev 2625 45170 1.2 1.0
AggregateType
Top – Coarse Aggregate Basalt rocks and diabase rocks, Porphyry, Dolomitic
sandstone, Granite, Flint gravel, whinstone, limestone
Top – Fine Aggregate River sand, manufacture sand, natural sand
Bottom – Coarse
Aggregate
Old pavement, RCA, Porphyry - Limestone - Recycled
concrete , Flint Gravel
Bottom – Fine Aggregate River sand, natural sand
49. Task 2.1 Survey A – Construction
49
Question 9: Please rate the
following aspects of 2LCP vs.
traditional paving methods
Question10: Please identify the
way(s) that challenges of 2LCP
were overcome most.
Results from 22 valid responses
Results from 24 valid responses
13%
0%
73%
14%
Extra Supervision
Unexpected Expenditures
Preplanning
Others
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Scheduling
Additional equipment
Aggregate selection
Mixing
Placing
Consolidation
Curing
QA/AC
5=substaintial
4
3=extra effort required
2
1=the same
50. Task 2.1 Survey A – Overall Experience
50
Question12: On a scale of 1-5
(1=worse and 5=best), please rate
your overall experience with 2LCP
Question13:Would you like to
participate on another 2LCP
project?
Results from 22 valid responsesResults from 22 valid responses
0% 0%
41%
45%
14%
1=worse
2
3
4
5=best
91%
9%
Yes
No
51. Task 2.1 Survey A – Overall Experience
51
Question14: On a scale of 1-5
(1=immediate need and 5 = no
need at all), please rate your
opinion on need for a 2LCP at this
time
Question15: If you chose there is
not a need for 2LCP at this time,
when do you think there will be a
need?
Results from 11 valid responsesResults from 22 valid responses
9%
14%
36%
23%
18%
1=immediate need
2
3
4
5=no need at all
37%
27%
18%
9%
9%
In 1 to 2 years
In 3 to 5 years
In 6 to 10 years
In 11 to 20 years
More than 30 years
52. Task 2.1 Survey A - Comments regarding
needs for 2LCP
52
Comments
Pros
With the 2LCP it is possible to create a higher-quality concrete surfaces and the opportunity to recycle old
concrete pavements.With the two layer you can use different consistencies between the upper and lower
concrete. In Austria, we are convinced of this 2LCP method since decades.
Higher priority needs at this time, but technology has technique has interest due to potential for sustainability
benefits.
Better utilization of local aggregates or recycled aggregates; friction; reduced noise. Decrease in supply of high
quality aggregate and higher transportation (trucking) costs
Desirable to ensure most economic use of aggregate
Contractor unable to achieve required ride quality with single layer
Depends on location and aggregate availability - its something new that must also be accepted as an option
Choice is ultimately left to the owner
Main reason is reduced noise level of fine exposed aggregate concrete. However, comparable noise levels
have recently been met with a single layer concept of exposed aggregate concrete. So, the question is if it is
worth facing the extra efforts and risks.
Cons
XXX is fortunate to have very good quality aggregate available across most of the state. We have not felt the
need for 2LCP.
Original reason is traffic noise nowadays we would make a concrete road with a silent asphalt topping
Experience was mainly for skid resistance issue but up to now, we are disappointed even if we used hard
aggregates. Need 2 sets of paving machine or special piece of kit. Since resistance asked of 35 MPa is pretty
low, powerful brushing equipment for exposed aggregate cannot be used within 24 hrs so we have problems
of uniformity of texture.
Method is new and therefore higher bids are received and should be accepted as an option
53. Task 2.2 Surveys and interviews of
contractors and TxDOT personnel regarding
concerns on 2LCP
Mr. Md Sarwar Siddiqui (CTR, University of Texas)
53
54. Task 2.2 Surveys and interviews of contractors
and TxDOT personnel regarding concerns on 2LCP
Contact contractors and TxDOT personnel from the
larger urban districts and the Construction Division’s
Pavements and Materials and Tests for their initial inputs
regarding concerns with 2LCP.
Prepare survey for this focused group and summarize
those survey and obtain specific information.
54
55. Survey for Potential Two-Lift Paving (2LCP)
Users
Target audience is TxDOT personnel and pavement
contractors.
Online survey was the primary method of response.
Total of 12 responses were received.
55
58. Field of Experience in Paving
23%
54%
23%
0%
Design
Construction
Research
Equipment
Manufacturer/Designer
58
59. Experience with Two Lift Concrete Paving
39%
31%
15%
15% have heard
not familiar
participate in a project
like the opportunity to
participate
59
60. Major Issues to Implement 2LCP
90.9%
81.8%
0.0%
18.2%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Constructability Increased cost Maintenance Material
compatibility
60
61. Major Concern with 2LCP
53.8%
69.2%
0.0%
23.1%
15.4%
0%
10%
20%
30%
40%
50%
60%
70%
80%
Constructability Increased cost Maintenance Material
compatibility
I do not have
any major
concerns with
2LCP
Responders also selected additional labor and
equipment and coordination of two plant
batching as other potential concerns.61
65. Summary
More than 50% of the respondents have over 16 years
of experience.
Approximately half of the respondents are experienced
in construction followed by design and research. No
equipment manufacturers participated in the survey.
About 30% of the participants had never heard of 2LCP.
About 40% had heard and 15% had participated in 2LCP
projects.
65
66. Summary
Constructability and increased cost are the two major
concerns in implementing 2LCP.
Most of the survey takers have low to moderate
likelihood of implementing 2LCP.
76% of the participants indicated strong to very strong
need for 2LCP.
66