Two-Lift Paving - Design Viewpoints
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The document discusses the design and construction of two-lift paving, particularly focusing on continuously reinforced concrete used in Belgian road projects. It highlights experiences, specifications, and challenges faced, including the use of recycled aggregates and issues with cracking over time. Additionally, it outlines changes and potential solutions for enhancing pavement performance based on observed problems.
Two-Lift Paving - Design Viewpoints
- 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
- 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