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A Hallmark of good
concrete pavements
50-year-old (and
- lder) PCC
pavements are common
- CA, TX, NY, IA, MN,
Mark B. Snyder, Ph.D., P.E., Pavement Engineering and Research - - PowerPoint PPT Presentation
Mark B. Snyder, Ph.D., P.E., Pavement Engineering and Research - - PowerPoint PPT Presentation
Mark B. Snyder, Ph.D., P.E., Pavement Engineering and Research Consultants, LLC (PERC) Bridgeville, Pennsylvania ACPA Mid-Year Meeting Workshop June 13, 2017 A Hallmark of good concrete pavements 50-year-old (and TH10 near St, Cloud,
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Service life of original PCC surface = 50+ years
(SHRP2 Definition)
No premature failures or materials-related distress Reduced potential for cracking, faulting, spalling, etc. Maintain desirable ride and surface texture
characteristics with minimal M&R Design and Build it Right & Stay Out As Long As Possible
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A combination of materials, mix design, structural
design, and construction activities selected and implemented to ensure acceptable long-term pavement performance. It’s A System!
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Concrete durability problems
- “D”-cracking, ASR, freeze-thaw damage, deicing
chemical attack, etc.
Joint failures
- Dowel corrosion or misalignment
- Faulting and Spalling
- Mid-panel crack deterioration
Construction issues
- Foundation settlement, sawing errors, over-finishing,
etc.
Fatigue failures are rare …
SLIDE 6
Address each potential failure mechanism in design
and/or construction specifications.
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Address each potential failure mechanism in design
and/or construction specifications
- Structural (layer materials and thicknesses, panel
dimensions, dowel size and spacing, etc.)
- Materials
Concrete (mix proportions, air void system, permeability, aggregate durability, etc.) Steel (corrosion protection) Foundation (drainage, erosion-resistance, etc.)
- Construction (compaction, curing techniques/materials
and timing, sawing, surface texture design/construction, dowel alignment, etc.)
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10 20 30 40 50 60 70 80
Slab Thickness Dowel Corrosion Resist Concrete Aggregate Dur. Concrete Matrix Dur. Construction Parameters Foundation Support Drainage Parameters
Expected Performance LIfe, Years
Std Design
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- Match performance potential for design components
(strengthen “weak links”)
- “Cafeteria” approach may not produce LLCP
LLCP requirements are project-specific!
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10 20 30 40 50 60 70 80
Slab Thickness Dowel Corrosion Resist Concrete Aggregate Dur. Concrete Matrix Dur. Construction Parameters Foundation Support Drainage Parameters
Expected Performance Life, Years
Std Design Improved Design and Construction Specs Improved Materials Improved Des, Matls & Const
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Increased Slab Thickness
- Old “rule of thumb”: 1 add’l inch PCC doubles ESAL capacity
- But … PCC thickness may not be controlling design life!
PavementME analyses indicate no added structural benefit above 13 – 13.5 inch pavement thickness for current design loads
Control Panel Dimensions
- Curl/warp stresses increase with panel size
- Old “rules of thumb”:
Max panel dimension = 18-24*thickness Max aspect ratio (L/W or W/L) = 1.5
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Thickness: 10 inches PCC Slabs: 14.8 ft x 11.8 Thickness: 6.3 inches PCC Slabs: 5.9 ft x 5.9 ft
Slab sizes and thicknesses for same top stress (350 psi)
Source: TCPavements
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DURABILITY
- Concrete aggregate (quality and grading)
- Cement paste (reduced permeability)
w/(c+p) Use of SCMs Increased air content Corrosion-resistant dowel bars
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Must be highly durable
- DF > 90 (AASHTO T161 Proc A)
- ASTM C1260 dilation < 0.8 percent
Angular, rough-textured,
abrasion-resistant
- Improved interlock, enhanced paste
bond, durable in construction
Graded (with fine aggregate) to
minimize paste content
- Reduced permeability and shrinkage
Low absorption, low CTE
preferred
- e.g., basalt, granite, some limestones,
etc.
Photo Credits: PCA
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Resistant to AAR (ASTM C1260 dilation < 0.8%) Graded (with coarse aggregate) to minimize paste
content
- Reduced permeability, shrinkage
>30 percent siliceous sand for microtexture Low absorption preferred
Photo Credit: PCA
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Maximum 500 lb/c.y.
cementitious content (with properly - graded aggregate blend)
- Volumetric stability
- Reduced potential for
chemical attack
Consider GGBFS for ASR mitigation, early strength gain Fly ash to reduce permeability and water bleeding,
increase long-term strength
- Typically 15 – 25 percent replacement of cement
- Class F for ASR mitigation
Source: Peter Taylor/National Concrete Pavement Technology Center
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Reduce allowable w/(c+p)
for higher strength, lower permeability
- PennDOT: 0.40 target, 0.42
max
- MnDOT: 0.40 max with
incentives down to 0.37
Use Supplemental
Cementitious Materials (SCMs) to densify paste
- Higher strength
- Reduced permeability
Source: Portland Cement Association
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Ceme Cement nt Wate ter + SCM + SCM + + Wate ter + C-S-H + CH CH = more C-S-H =
Ho How SCMs w SCMs Wor
- rk
Source: National Concrete Pavement Technology Center
1000 2000 3000 4000 5000 6000 7000 8000 9000 Class F Class C1 Class C2 GGBFS All fly ash 25% replacement, GGBFS 35% RCP (Coulombs)
(w/c = 0.365, RCP: @ 28 days)
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Increase plastic air content
- Standard: 6.5% +/- 1.5%
- HPCP: 8.5% +/- 1.5%.
Require 28-day RCP of <2500 coulombs. W/(C + P) < 0.40 (incentive to 0.35) Require minimum 30 percent siliceous fine
aggregate (microtexture/friction)
Optimize total aggregate grading
- “Shilstone” approach
- 0.45 Power gradation
- 8-18 /7-18 grading bands
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Must be highly corrosion-resistant Structural design must provide:
- Good load transfer
- Sufficiently low bearing stress
- Sufficiently low overall and differential deflection
Many possibilities:
- 316L stainless steel (solid, clad, sleeved or tubes)
- Zinc alloy-clad or –sleeved steel
- FRP-clad steel
- Low carbon, high-chrome composite
- Special epoxy-coated steel
- FRP (requires larger bars and/or closer spacing for equivalent
behavior)
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Minnesota’s program includes all areas of construction Program applies to the entire industry (agency,
contractors and consultants alike)
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Certification of batching
equipment
Pre-qualification of
contractor
INSPECT, INSPECT, INSPECT
- Flexural strength
- Air Content
- Unit Weight
- Water/cementitious ratio
- Thickness
- Smoothness
- Dowel alignment
- Field operations
Photo credit: ACPA Photo credit: PCA
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Certified batch plants and
- perators
- Stockpile moisture
management
Adequate number of
trucks to ensure concrete is fed to paver at consistent and useful rate.
- Avoid paver stops/starts.
Control delivery time, mix
temperature.
Never allow retempering!
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Adding 1 gal. of water to 1 yd3 of concrete:
- Increases slump 1 in.
- Decreases compressive strength by 200 psi
- Wastes the effect of 1/4 sack of cement
- Increases shrinkage by 10%
- Increases permeability by up to 50%
- Increases risk of air void
problems
Don’t Add Excess Water
Cons Constr truc uction tion
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Microwave Oven Testing of Water Content in Freshly Mixed Concrete – AASHTO T 318
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Need proper and timely curing with effective process PAMS curing compounds were developed to be used in
applications requiring extremely durable concrete
- Originally developed to replace the old chlorinated rubber
curing compounds, which are no longer manufactured
Offers better water retention than current resin and
wax technologies (Minnesota Study: up to 5x more effective!)
Offers improved sealing characteristics for additional
protection
Concrete cured with PAMS has increased abrasion
resistance, hardness, resistance to de-icing chemicals
Source: W.R. Meadows
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- Timeliness is essential
- Consider use of HIPERPAVIII)
- Proper depth (consider section
thickness variance)
Photo credit: PCA
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Benefits:
- Significant extension of service life
- Reduction of maintenance/rehabilitation frequency
- Reduced LCC
Initial Costs
- 3 – 16 percent of paving costs
- Much lower percentage of project costs (considering
R.O.W., noise walls, adjacenet structures, traffic control, etc.)
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Total project cost ~ $18.4M Total paving cost ~ $3.7M (20.1% of project cost) Incremental cost of HPCP ~ $610,000
- 16.5 percent of paving costs
- Only 3.4 percent of project costs!
Mn/DOT economic analysis:
- LCCA of HPCP = 5% lower than conventional concrete
pavement
- This doesn’t include user cost savings – potentially huge!
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LLCP design and construction can be accomplished
with the knowledge and tools that we already have!
Structural design for desired traffic loading over
performance period
Materials design for durability (resistance to
exposure)
All design components must meet performance
requirements (no “weak links”)
QA/QC is essential (more intense effort required) Examples: MN, WI, PA, CA (and more …)
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