A Two-Lift concrete Paving (2LCP) workshop was organized as a part of the Texas Department of Transportation (TxDOT) project 0-6749: Feasibility Study of Two-Lift Concrete Paving (2LCP). This workshop was conducted at the J. J. Pickle Research Campus (PRC), The University of Texas at Austin, Austin, TX on May 23rd, 2013. Dr. Jiong Hu, Texas State University, Research Supervisor, and Dr. David Fowler, The University of Texas at Austin, Co-Research Supervisor, co-chaired the workshop. The workshop offered the option of attending in person or remotely through webinar. Fifty-one attendees were present remotely or in person; 28 in person and 23 persons remotely.

1. Two-lift paving
Design aspects
Luc Rens, C.E.
FEBELCEM – Consulting Engineer
l.rens@febelcem.be
EUPAVE – Managing Director
May 23, 2013, Two-Lift Paving Workshop, Austin, Texas

2. Classic continuous reinforced
concrete in Belgium
Belgian standard design for concrete motorways
1 lift - single run of the slipform paver
Simple and reliable construction method
Exposed aggregate concrete surface
Stones : PSV ≥ 50 - no recycled materials

3. 1996 - Herne : Test
sections of low-noise
surfaces
TWO-LIFT PAVING - BELGIAN EXPERIENCE

4. 2002
N511 – Estaimpuis
Double layered CRCP
with different top layers
TWO-LIFT PAVING - BELGIAN EXPERIENCE

5. E34/N49
Category : main road (at most places transformed into
motorway)
Traffic volume (March 2007):
23 000 vehicles a day in the direction from
Antwerp to Zelzate
25% heavy traffic

Construction in 2 phases:
Direction from Antwerp: 2007
Direction to Antwerp: 2008

6. E34/N49 – Two lift continuously
reinforced concrete
 Construction in two layers: optimum noise reduction at
surface due to fine exposed aggregate concrete in top
layer
 Continuously reinforced concrete
 Recycled aggregates in the lower course – aggregates
from existing concrete road

7. Recycled aggregates: from existing road –
quality controlled by COPRO

8. Concrete mix specifications
Specifications for the top layer:
- aggregate 4/6,3 (PSV  50) – no reclaimed material allowed
- coarse sand – no reclaimed material allowed
- CEM III/A 42,5 N LA  425 kg/m³
- W/C  0,45
- air entrained – air void content  5%
Specifications for the bottom layer:
- aggregate 4/6,3 : no reclaimed material allowed
- aggregate 6,3/20 – 20/32 : reclaimed crushed concrete,60 to
100%
- coarse sand – no reclaimed material allowed
- CEM III/A 42,5 N LA  375 kg/m³
- W/C  0,45
- air entrained – air void content  3 %

9. Structure of two-layered CRCP
Continuous longitudinal
reinforcement at 8 cm
from surface

10. Placing of the concrete “wet on wet” by two slipform
pavers (maximum time interval of 2 hours)
EXECUTION

11.  Surface finishing = fine-grained exposed
aggregate concrete
EXECUTION

12. RECLAIMED AGGREGATES IN PAVEMENT CONCRETE
Experiences in other countries
 Austria
• Double-layered jointed plain concrete since 1990
• 21 cm + 4 cm
• Motorway programme (A1 – A2)
• Reuse in the lower course of 65 % of recycled
crushed concrete from the old pavement
• Asphalt layer between base and concrete pavement
 Germany
• Has taken over the Austrian technique
• Geotextile between base and concrete pavement
• The Netherlands, Belgium…

13. N49 : after 3 years in service…
(May 2011)

14. N49 : after 3 years in service…
(May 2011)

15. N49 : after 3 years in service…
(May 2011)

16. Horizontal cracks at the height of
the reinforcement
Shrinkage crack
Over total
depth
Horizontal
crack
Vertical crack
ends at the
reinforcement

17. What is different?
Older realisations with double layered CRCP:
Herne (1996) – Estampuis (2002)
What is different on the E34/N49?
- Rebars are higher in the concrete layer: 8 cm from
surface at the N49 and 13 cm in Herne?
- Traffic intensity is much higher and the concrete has
been exposed to traffic much sooner
- Time of execution: warm summer for the N49, normal
spring in Herne
- Use of recycled aggregates in the bottom lift

18. Research and investigation
 Inspection of cores
 Bond steel – concrete
 Microscopic examination
 Ultrasonic tomography

19. Ultrasonic tomography :
measurement at a crack

20. Concrete properties determined on bottom layer
(after 4 years in service)
Core Volumic density Compressive
strength
1 2350 kg/m³ 80,32 N/mm²
2 2360 kg/m³ 82,55 N/mm²
3 2360 kg/m³ 88,45 N/mm²

21. We are still looking for the
answers…
How did the horizontal cracks occur?
 Due to the too large opening of the initial transverse cracks?
 Due to the use of reclaimed aggregates in the bottom layer of
the concrete? (because of additional shrinkage and/or lower
strength)
 Due to the two layers? Differential shrinkage?

22. Changes in design for recent
worksites of two-lift CRCP
 Changes in design
– No RCA
– No air entrainer in
bottom layer
– Induced cracking
– Long. steel 1cm
lower

23. Risk for punch-outs

24. What could be the solutions ?
ACTIVE CRACK CONTROL ?
 Short crack inducer
– At the edge of the pavement
– 40 cm wide
– 3 cm deep
– Spaced at 1,20 m (4 ft)

25. Test strips of double layered
concrete (JPCP) for industrial areas
 Wet-in-wet
application –
excellent bond
 Recycled aggregates
in base layer
 TiO2 in top layer

26. Thank you for your
kind attention