Seminario Internacional Construcción y Rehabilitación con Pavimentos de Hormigón Pre Paving Considerations
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Seminario Internacional Construcción y Rehabilitación con Pavimentos de Hormigón Pre Paving Considerations
- 1. SEMINARIO INTERNACIONAL CONSTRUCCIÓN Y REHABILITACIÓN CON PAVIMENTOS DE HORMIGÓN SANTIAGO 25 DE MAYO DE 2015
- 3. Lafarge Research Center (LCR) www.lafarge.com @LafargeGroup Robert Rodden, P.E. www.robertrodden.com Infrastructure Solutions – Roads 5/25/2015 3 ConstructionandRehabilitationof ConcretePavements International Society for Concrete Pavements (ISCP) www.concretepavements.org @ConcPaveSociety Executive Director
- 4. 5/25/2015 4 ConstructionandRehabilitationof ConcretePavements ISCP’s Mission “The mission of ISCP is to facilitate the advancement of knowledge and technology related to concrete pavements through education, technology transfer and research at an international level.”
- 5. 5/25/2015 5 ConstructionandRehabilitationof ConcretePavements ISCP is Online @ www.concretepavements.org
- 6. ALL OF TODAY’S PRESENTATIONS • Can be downloaded at any time at: http://bit.ly/1PO7ixS 5/25/2015 ConstructionandRehabilitationof ConcretePavements 6
- 7. Countries with the Largest Paved Roadway Networks 5/25/2015 ConstructionandRehabilitationof ConcretePavements 7Source: USA CIA’s World Factbook KilometersofPavedRoadway
- 8. 5/25/2015 ConstructionandRehabilitationof ConcretePavements 8 Available in ACPA’s online bookstore: http://www.acpa.org/publications-for-purchase/ EB237 Primary Reference For This Presentation
- 9. Joint Layout Pre-Paving Considerations 5/25/2015 9 ConstructionandRehabilitationof ConcretePavements
- 10. Why Joint Concrete Pavement? • Historical Reason: control natural cracking 5/25/2015 10 ConstructionandRehabilitationof ConcretePavements 40-80 ft (12-24 m) 15-20 ft (4.5-6 m) Sawcut @ 15 ft (4.5 m) or less
- 11. Why Joint Concrete Pavement? • Other reasons we joint concrete pavements: Divide pavement into construction lanes or increments. Accommodate slab movements. Provide load transfer via placed dowels. Provide uniform sealant reservoir. To leverage joint spacing in design! 5/25/2015 ConstructionandRehabilitationof ConcretePavements 11
- 12. Why Joint Concrete Pavement? • Not for lane delineation! 5/25/2015 ConstructionandRehabilitationof ConcretePavements 12
- 13. Types of Concrete Pavement Steel Reinforcing, Joint Spacing, and Crack Spacing Differentiate Between the JPCP, JRCP, and CRCP 5/25/2015 13 ConstructionandRehabilitationof ConcretePavements Jointed Plain Concrete Pavement (JPCP) Steel 0% Joints 12-20 ft (3.6-6 m) Cracks N/A Jointed Reinforced Concrete Pavement (JRCP) Steel 0.06-0.25% Joints 40-100 ft (12-30 m) Cracks 15-20 ft (4.5-6 m) Continuously Reinforced Concrete Pavement (CRCP) Steel 0.6-0.85% Joints N/A Cracks 2-6 ft (0.6-1.8 m)
- 14. Joint Layout • Critical to crack control • Typically decided by engineer and included in project plans – No knowledge of contractor, equipment, processes – Hard to precisely place things like utilities • Contractor may be allowed to develop plans but, even if not, field adjustments can and should be made 5/25/2015 ConstructionandRehabilitationof ConcretePavements 14
- 15. The ACPA 10 Step Method of Joint Layout for Intersections 5/25/2015 15 ConstructionandRehabilitationof ConcretePavements
- 16. Field Adjustments are Necessary • Adjust joints that are within 5 ft (1.5 m) of a utility! • Must isolate utilities as shown on plans 5/25/2015 ConstructionandRehabilitationof ConcretePavements 16 Contractor must also consider impact of moving joints!!!
- 17. Joint Layout Design… References: • EB237 – Concrete Pavement Field Reference: Pre-Paving • IS006, Intersection Joint Layout • IS061 – Design and Construction of Joints for Concrete Streets • R&T Update 6.03 – Concrete Roundabouts • TB010 – Design and Construction of Joints for Concrete Highways • TB017 – Airfield Joints, Jointing Arrangements and Steel • TB019 – Concrete Intersections: A Guide for Design and Construction 5/25/2015 ConstructionandRehabilitationof ConcretePavements 17
- 20. It Starts from the Ground Up • Roadbed (subgrade and subbase) design and construction are key to: – Long-term performance – Smoothness (initial and long-term) 5/25/2015 ConstructionandRehabilitationof ConcretePavements 20
- 21. What is Good Support? • Roadbeds for a concrete pavement structure should: – Be free from abrupt changes in character of the materials (should be uniform and constructed of a material that will provide requisite stability over the life of the pavement) – Resist erosion – Be engineered to control subgrade soil expansion/frost heave • Above all other concerns, uniformity is of utmost importance 5/25/2015 ConstructionandRehabilitationof ConcretePavements 21
- 22. Subgrades • Obtain uniform support by controlling: – Expansive soils – Frost-susceptible soils (frost heave) – Pumping – Wet Soils 5/25/2015 ConstructionandRehabilitationof ConcretePavements 22
- 23. Controlling Wet Soils • Enhancement • Reinforcement/Separation • Substitution 5/25/2015 ConstructionandRehabilitationof ConcretePavements 23
- 24. Unstabilized Subgrades 1. Grade to match roadway plans 2. Cross haul to avoid abrupt changes 3. Compact at optimum moisture content 4. Identify soft spots and fix 5. Protect from rain by “tight blading” and finishing with smooth drum roller 6. Fine grade to plan elevations within tolerances 5/25/2015 ConstructionandRehabilitationof ConcretePavements 24
- 25. Stabilized Subgrades 1. Trim to match roadway plans but finish the grade below the final grade elevation 2. Spread stabilized agent as evenly as possible 3. Mix, add water and compact 4. Finish grade 5. Cure the subgrade 5/25/2015 ConstructionandRehabilitationof ConcretePavements 25
- 26. Step 3 for Cement-Treated Soils • Mix, add water, and compact (within 2 hours) in one continuous operation • Moisture content within 2% of optimum • Min of 60% passing #4 (4.75 mm) sieve • Special attention to longitudinal overlap • Strictly adhere to 2hr working period 5/25/2015 ConstructionandRehabilitationof ConcretePavements 26
- 27. Step 3 for Lime-Stabilized Soils • Mix and add water simultaneously • Moisture content of optimum to +5% of optimum • Lightly compact and grade to drain excess water • Let soil sit idle for 24 to 72 hours • Re-mix, adding water as necessary to target moisture content of optimum +3%; recompact • Min of 60% passing #4 (4.75 mm) 5/25/2015 ConstructionandRehabilitationof ConcretePavements 27
- 29. General Notes on Subbases • Thick subbases (greater than 6 in. [150 mm]) are typically not beneficial, and therefore are not recommended • The width of the subbase should accommodate the paving equipment by extending approximately 3 ft (1 m) beyond the width of the pavement on each side • Recommended minimum thickness: – Unstabilized: 4 in. (100 mm) – CTB or LCB: 4 in. (100 mm) – ATB: 2 in. (50 mm) • Recycled materials are commonly used 5/25/2015 ConstructionandRehabilitationof ConcretePavements 29
- 30. Unstabilized Subbases 1. Mix a uniformly moist, homogeneous material 2. Place using preferred method 3. Compact to required density w/min effort 4. Trim to plan elevation and tolerances 5. Moisture content key during construction of subbase AND immediately before paving 5/25/2015 ConstructionandRehabilitationof ConcretePavements 30
- 31. Cement-Treated Subbases (CTB) 1. Central-mix and place material or road-mix 2. Compact with rollers and trim to specified grade a) Must place and trim within 4 hrs of mixing! 3. Cure the subbase 4. If trimmed after curing, curing compound must be reapplied 5/25/2015 ConstructionandRehabilitationof ConcretePavements 31
- 32. Lean Concrete Subbases (LCB) 1. Central-mix the concrete 2. Place to plan elevation and tolerances a) No additional finishing b) No texturing 3. Cure (if necessary) 4. Joint (If necessary) 5/25/2015 ConstructionandRehabilitationof ConcretePavements 32
- 33. Asphalt-Treated Subbases (ATB) 1. Mixed and placed with conventional asphalt paving equipment 2. Dense-graded mixtures require compaction 5/25/2015 ConstructionandRehabilitationof ConcretePavements 33
- 35. Safety • Ride quality is pointless if someone is hurt • Plan out truck routes • Use of highway patrol • Daily safety meetings • Employees get bold • Teach employees to watch traffic 5/25/2015 35 ConstructionandRehabilitationof ConcretePavements
- 36. Safety • Pay attention to broom handles, saws and protrusions in traffic • Watch for backing trucks and make sure alarms are functional • Be aware of surroundings 5/25/2015 ConstructionandRehabilitationof ConcretePavements 36
- 37. FREE Safety Training! • Available around the clock, 365 days per year. • No cost to par;cipants. • Cer;ficates of comple;on may count toward a total of 11.0 professional development hours (PDHs). 5/25/2015 ConstructionandRehabilitationof ConcretePavements 37 www.acpa.org/self-paced-online-courses/
- 39. Stringline Considerations • Can be wire, cable, woven nylon, polyethylene rope, or similar material • Continuously check tension • Clean and tight splices • Stakes must be long enough • Maximum stake spacing of 25 ft (7.6 m) • See Staking Interval Calculator at apps.acpa.org for recommendations on curves 5/25/2015 ConstructionandRehabilitationof ConcretePavements 39
- 40. Stringline Considerations (con’t) • Place winches at ≤ 1,000 ft (305 m) • Beneficial to have stringlines on both sides of paving • Some situations require cantilever or trusses for sensors to reach stringline 5/25/2015 ConstructionandRehabilitationof ConcretePavements 40
- 41. Setting the Stringline 1. Set reference hubs at proper interval and place a stringline support stake outside of each hub 2. Set stake arm to the proper elevation 3. Install stringline 4. Tighten stringline 5. Check installation 5/25/2015 ConstructionandRehabilitationof ConcretePavements 41
- 42. Stringline Setup 5/25/2015 ConstructionandRehabilitationof ConcretePavements 42 Benchmark Control Points (Paving Hubs–Pins) 25 ft (7.6) typ. Survey Reference Point
- 45. Notes on Setting Reference Hubs • Reference hubs are set using a variety of methods • Contractor determines offset • Grade info on identifier next to where hubs will be set • Proper communication is KEY to a successful operation!! 5/25/2015 ConstructionandRehabilitationof ConcretePavements 45
- 46. Once Set, the Paver Does the Rest Uniform Slope in a Superelevation into and though a Horizontal Curve 5/25/2015 46 ConstructionandRehabilitationof ConcretePavements
- 47. Once Set, the Paver Does the Rest Rooftop Slope in a Straight Section to Encourage Drainage to Each Edge of Pavement 5/25/2015 47 ConstructionandRehabilitationof ConcretePavements
- 48. Once Set, the Paver Does the Rest Transition from Rooftop Slope to Uniform Slope into a Horizontal Curve 5/25/2015 48 ConstructionandRehabilitationof ConcretePavements
- 54. Placing Embedded Steel Pre-Placed in Baskets • Requires support system • Requires placement ahead of paving or at the same time as paving is occurring • Increased transport cost • Increased labor in placement Placed with Insertion • No support system needed • Dowels or tiebars are inserted after concrete is placed • Lower transport cost • Decreased labor in placement 5/25/2015 54 ConstructionandRehabilitationof ConcretePavements … both methods can place dowel bars and tiebars within typical specifications, though the concrete mixture characteristics are more important with insertion.
- 56. Placing & Staking Dowel Baskets 5/25/2015 ConstructionandRehabilitationof ConcretePavements 56
- 59. Slipform Paver Equipment Setup 5/25/2015 59 ConstructionandRehabilitationof ConcretePavements Like extrusion processes but we pull the form.
- 60. Slipform Mold (Pan) Setup • Preliminary leveling of paving machine’s frame and then slipform mold • Check joints in the pan • Adjust center to account for cross slope • Check alignment • Adjust edges for edge slump 5/25/2015 ConstructionandRehabilitationof ConcretePavements 60
- 65. Final Grade and Cross Slope Check 5/25/2015 ConstructionandRehabilitationof ConcretePavements 65
- 66. Concrete Mixture Analysis and Approval Pre-Paving Considerations 5/25/2015 66 ConstructionandRehabilitationof ConcretePavements
- 67. Concrete Mix Proportioner App apps.acpa.org 5/25/2015 ConstructionandRehabilitationof ConcretePavements 67
- 70. Cement • The “glue” that hold concrete together • Increase cement content = increase strength, but: – Need more air entraining admixture for desired air – Need more water, resulting in more drying shrinkage – Increased risk of segregation with more paste – More bleed water, increasing permeability – Earlier sawing required – Stiffer mixture – Less fatigue capacity 5/25/2015 ConstructionandRehabilitationof ConcretePavements 70
- 71. Cementitious Materials Content • Use least amount of cementitious materials necessary to meet strength and workability – Typical minimum is about 500 lb/yd3 (300 kg/m3) for slipform • Dosage typically reported as cement replacement: • SCMs may retard strength gain 5/25/2015 ConstructionandRehabilitationof ConcretePavements 71
- 72. Water-Cementitious Mataerial Ratio • Lower w/cm = higher strength – Slipform paving - maximum: 0.45; typical = 0.40 – Fixed-form paving/hand pours - max: 0.50; typ = 0.45 • For w/cm below about 0.40, autogenous shrinkage becomes a concern 5/25/2015 ConstructionandRehabilitationof ConcretePavements 72
- 73. Aggregates • 60-75% of mixture • Provide volume stability! • Coarse to fine ≈ 60/40 • Selection in critical – All aggregate should be prequalified for durability to freeze- thaw, ASR, alkali-carbonate, D-cracking • Coarse agg is major driver in concrete CTE • Agg hardness impacts sawing operations • Cleanliness and surface moisture important 5/25/2015 ConstructionandRehabilitationof ConcretePavements 73
- 74. Aggregate Gradation • CONTROLS workability!! • Well-graded combined aggregate gradation will: – Reduce water demand – Lower drying shrinkage – Increase workability – Improve strength 5/25/2015 ConstructionandRehabilitationof ConcretePavements 74
- 75. Gradation Analyzer App apps.acpa.org 5/25/2015 ConstructionandRehabilitationof ConcretePavements 75
- 76. Gradation Analyzer App apps.acpa.org 5/25/2015 ConstructionandRehabilitationof ConcretePavements 76
- 77. Testing – Temperature • ASTM C1064 • EASY, just place thermometer in concrete • Results help verify conformance to requirements 5/25/2015 ConstructionandRehabilitationof ConcretePavements 77
- 78. Testing – Slump • ASTM C143 / AASHTO T119 • Measures consistency; NOT QUALITY! • Typical values: – Slipform: 0.5-1.5 in. (13-38 mm) – Fixed form: 3-4 in. (75-100 mm) • Slump is dependent on mixture and also on time of testing 5/25/2015 ConstructionandRehabilitationof ConcretePavements 78
- 79. Testing – Density (Unit Weight) • ASTM C138 / AASHTO T121 • Measures known volume • Typically 130 to 150 lb/ft3 (2,000 – 2,400 kg/m3) • Indicates batch-to-batch variability • Reduction in density may indicate: – Higher air content, higher water content, lower cement content, change in proportions of ingredients, or change in aggregate specific gravity or moisture • One of the most valuable tests for process control 5/25/2015 ConstructionandRehabilitationof ConcretePavements 79
- 80. Testing – Air Content • ASTM C231 / AASHTO T152 • Target air depends on agg size • Testing at plant or in front of paver doesn’t account for air loss of up to 2% in paver • Quality critical to durability • AVA and petrography are other means to measure • Super Air Meter latest tool! 5/25/2015 ConstructionandRehabilitationof ConcretePavements 80 Max Agg Size Target Air 3/8 in. (9.5 mm) 7 ½% ½ in. (13 mm) 7% ¾ in. (19 mm) 6% 1 in. (25 mm) 6% 1 ½ in. (38 mm) 5 ½%
- 81. Testing – Air Content (continued) • Affected in the field by: – Cement – SCMs – Chemical admixtures – Gradation of aggregates – w/cm ratio – Temperature – Delays – Placement/consolidation 5/25/2015 ConstructionandRehabilitationof ConcretePavements 81
- 82. Testing – Compressive & Flexural Strength • ASTM C39 / AASHTO T22 for cylinders • ASTM C78 / AASHTO T97 for beams • Typical strength requirements (low / avg / high) – Compressive: 3,000 psi (20 MPa) / 3,500 (24) / 4,000 (28) – Flexural 550 psi (3.8 MPa) / 600 (4.1) / 650 (4.5) 5/25/2015 ConstructionandRehabilitationof ConcretePavements 82
- 83. Testing – Maturity to Estimate Strength • ASTM C1074 / AASHTO T325 5/25/2015 ConstructionandRehabilitationof ConcretePavements 83
- 84. Testing – Maturity to Estimate Strength 5/25/2015 ConstructionandRehabilitationof ConcretePavements 84
- 86. Maturity Calculator apps.acpa.org 5/25/2015 ConstructionandRehabilitationof ConcretePavements 86
- 89. Specifications • Address concrete materials durability and what needs to be measured to control critical elements of construction and design • All specifications act to assign risk. – Method specifications assign risk to the owner. – End result specifications assign risk to the contractor. • Alternative types of specifications and contracting methods are being used on an ever increasing number of projects: – Performance based specifications, design/build, warranties and others 5/25/2015 ConstructionandRehabilitationof ConcretePavements 89
- 91. Quality Control (QC) versus Quality Assurance (QA) • QA is responsibility of owner – ensure the end product is of proper quality and motivates QC • QC is responsibility of contractor – makes the product of proper quality and motivated by QA and acceptance 5/25/2015 91 ConstructionandRehabilitationof ConcretePavements
- 96. Coordination • QC plan must be discussed at pre-paving meeting • Communication between owner, project engineer, inspector, plant manager, etc. is crucial to project success! • Hot/cold weather contingencies • Who conducts QA tests? • Communicate necessary mix adjustments based on QC results!!!!! 5/25/2015 ConstructionandRehabilitationof ConcretePavements 96
- 97. Test Specimens • Hardened tests (e.g., strength, hardened air, etc.) are more susceptible to ambient conditions and handling than fresh tests (e.g., air content, unit weight, etc.) • Cylinders typically preferred over beams – Less sensitive to handling and curing of specimen – Smaller and easier to transport • Portable containers available to control both moisture and temp in transport 5/25/2015 ConstructionandRehabilitationof ConcretePavements 97