Pre-XVIII CAVyT - Peter Taylor

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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 –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



-

-

-

-



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 • Workability – Need to know the response to vibration

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Testing • Uniformity via calorimetry – 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 • Uniformity via unit weight – Did the right amounts of materials go in the truck?

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Testing • Air void system via SAM

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Testing • Potential Durability via resistivity

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Testing • 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 • The basics are still valid • Complexity is increasing


So? • • • •

Bigger better brighter More cost effective More sustainable Safer

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