Innovations in Concrete Pavements Dr Peter Taylor
Outline • Innovations in – Materials – Paving systems – Design – Construction – Specifications – Maintenance
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Materials • • • • • •
Cementitious materials Aggregates Admixtures Fibers Dowels Geotextiles
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Early Cements • Lime cements – Mortar – Stucco
CaCO3 Heat
Carbonation
Ca(OH)2
CaO Water
Early Cements • Pozzolana – Glassy, fine, silica – Reacts with water, underwater
Early Cements • Portland Cement – Patented by Joseph Aspdin 1824 – “Artificial Stone” • • • •
Limestone Clay Heat Grind
Cements • Improving Efficiency – Rotary kilns (wet process) – Rotary kilns (dry process) with heat exchange towers
Cement is Changing
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• Fly ash
Supplementary Cementitious Materials
• Slag • Natural pozzolan
• Silica fume • Others? 9
The new wrinkle • Portland limestone cements – Up to 15% limestone added at the grinding mill – Small effects on performance
– Synergy with fly ash – Cuts CO2 footprint
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Other Cements • Calcium Sulfoaluminate (CSA) Cement • High alumina cement
• Geopolymers • Alkali activated fly ash • Magnesium phosphate systems
Where next? • Reclaimed fly ash • SCMs from other industries
• …
Aggregates • Gravels vs crushed rock • Dealing with ASR and D-Cracking
• Recycled concrete aggregates
Admixtures • Workability • Setting • Air • Viscosity or rheology modifiers • Corrosion inhibitors • Waterproofers • …
Fibers •
Micro – Synthetic, natural or glass fibers – Length < 0.5 inch – Plastic shrinkage cracking
•
Macro – Synthetic or steel – Length 0.5 to 2.5 inches – Keep cracks closed
Evolution of Coated Dowels
Greased or Painted
ASTM A775 “Flexible” Green
FRP over Steel Core (CRT)
Mark Snyder
ASTM A 934 “Nonbendable” Purple or Grey
Multi-layer ARO over A934 (Simplex)
Alternate Dowel Materials
GFRP/FRP (Master Dowel and others)
Zinc Alloy Strip over Steel (Jarden)
Mark Snyder
Stainless Steel
Microcomposite Alloy (MMFX)
Stainless Steel-Clad or â&#x20AC;&#x201C;Sleeved (CMI)
Alternate Dowel Shapes
Elliptical (steel or FRP)
Plate Dowels – Covex (PNA)
Mark Snyder
Plate Dowels – Diamond-Shape (GreenStreak)
Tubular (stainless steel or FRP, filled or capped)
Plate Dowels – Tapered (PNA)
Tubular (galvanized or epoxy+galvanized – O=Dowel)
Internal Curing • Curing is promoting hydration by – Providing water – Keeping it warm
• Trick is get the water to the cement • Without affecting w/cm
Weiss
Internal Curing • Lightweight fine aggregate • Super Absorbent Polymers
Bridge Deck Cracking - OH
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Geotextile Interlayers • Isolate overlay from existing pavement
• Provide level surface for construction • Provide a cushion
Proportioning Approaches: Past • Structural concrete • Other concrete • Waterproof concrete • • • •
1:2:4 1:3:6 Add salt
No chemicals No SCMs Precision was ugly Bulking made it worse EB001 - 1916 23
Proportioning Approaches: Present • ACI 211-1991 – Choose workability – Calculate water to get that workability – Choose w/c to get performance – Calculate cement content – Calculate SCM content – Calculate rock content based on sand fineness – Calculate sand content to fill the space 24
Void Ratio Proportioning Filler Gradation
Glue What sort How much
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Proportioning to achieve design goals Aggregate System Type, gradation
Workability
Transport
Strength
Cold weather
Shrinkage
Aggregate stability
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-
-
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Paste quality
Air, w/cm, SCM type and dose
Paste quantity
Vp/Vv
-
-
-
-
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Before and after
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Paving systems • • • • •
Formed Slipformed RCC Precast Repairs
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Slipformed • Fast • Familiar
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RCC – – – – – –
Zero slump No forms needed No reinforcing steel No finishing
Consolidated with vibratory rollers Can take light traffic immediately
Precast • Quality controlled at the plant • Early opening to traffic • Insensitive to excursions
Design • Rule of Thumb • AASHTO 93 (ACPA Winpas) • • • •
AASHTOWare Pavement ME Pavement Designer.org BCOA Thin Concrete Pavement (TCP) 32
Handling Then
Handling Now
Early Pavers • First slipform paver was in Iowa 1950’s
Current Machines • • • • •
Wide and heavy Controlled vibrators Adjustable pans Stringless Real time smoothness
Curing
Specifications • Slump • Strength • Air • • • •
Transport Workability Salts Shrinkage 38
Testing â&#x20AC;˘ Workability â&#x20AC;&#x201C; Need to know the response to vibration
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Testing â&#x20AC;˘ Uniformity via calorimetry â&#x20AC;&#x201C; Were the right reactive materials delivered? Hydration Profile 15.00
Sample "5P" Sample "5C" Sample "5F" Sample "5S"
12.00
J/gh
9.00
6.00
3.00
0.00 0:00:00
6:00:00
12:00:00
18:00:00
24:00:00
Tim e of Hydration (hrs)
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Testing â&#x20AC;˘ Uniformity via unit weight â&#x20AC;&#x201C; Did the right amounts of materials go in the truck?
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Testing â&#x20AC;¢ Air void system via SAM
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Testing â&#x20AC;˘ Potential Durability via resistivity
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Testing â&#x20AC;˘ UPV to assess setting and when to cut
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Preservation • Extend pavement life and restore functional condition – Slab stabilization – Partial-depth repairs – Full-depth repairs – Retrofitted edge drains – Load transfer restoration – Diamond grinding and grooving – Joint resealing
Future • Smart concrete • E-ticketing
• Measuring the fresh concrete – vibration…
Closing â&#x20AC;˘ The basics are still valid â&#x20AC;˘ Complexity is increasing
So? • • • •
Bigger better brighter More cost effective More sustainable Safer
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