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Design and Construction of
Concrete Parking Areas
Session W59, CONEXPO – CON/AGG 2014
Wednesday, March 5, 2013, 1:00 – 2:30 pm
Tim Cost, PE, FACI Holcim (US) Inc.
Amy Miller, PE National Ready Mixed Concrete Association
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• Upkeep & maintenance
• Aesthetics
• Lighting & safety
• Construction scheduling
• Site soils, environmental
considerations
• Economics of alternate
designs
– Construction costs
– “Life cycle” costs
Concrete vs. asphalt considerations
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Pavement selection trends, economics
• Concrete is no longer more expensive to construct
• Life cycle considerations further enhance this value
for the owner
• Other facility costs and
operating expenses can
be reduced when
pavements are concrete
• Sustainability and
environmental concerns
favor concrete
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Pavement economics have changed!
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Topics for discussion
• Pavement Design
• Jointing & Reinforcement
• Planning & Construction
• What goes wrong & how can
it be avoided?
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• Design loads are truck numbers and frequencies
• Required input: – Strength of subgrade / subbase
– Concrete strength
– Traffic (truck loads and frequencies)
– Design life
• Preferred references: – ACI 330 documents
– ACPA documents
• Caution is advised:
– AASHTO documents – oriented toward highway pavements, not generally appropriate
– Don’t address most details and options for parking lots
Design resources & considerations
Not Recommended!
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ACI committee 330 documents
330R-01, Guide for Design and Construction of Concrete
Parking Lots
330.1-03, Specification for Unreinforced Concrete Parking Lots
Under development:
330.X, Guide for Design and Construction of Concrete
Site Paving for Heavy Industrial and Trucking Facilities
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General Scope of 330R: Traffic, 0 to 700 trucks/day
Pavement thickness, 4” to 9”
Load transfer requirements, moderate
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Load
Load
Without load transfer: Excessive deflections and flexure, performs like free edge loading
With load transfer: Deflections and flexural stresses are reduced
Definition – load transfer
• Shear strength provided at joints (or cracks) by dowels or other features, aggregate interlock, or contact friction
• Significantly reduces load-related deflection
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Concrete pavement design
• Thickness determination, based on: – Design life
– Traffic loads & frequencies
– Subgrade (or subbase) support capacity
– Concrete strength
• Jointing / reinforcement – Load transfer considerations
– Prevention of uncontrolled crack issues
• Other design questions – Grades & drainage
– Edge effects
– Panel sliding
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ACI 330R-08 thickness table (Table 3.4)
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Type of soil Support k, psi/in. CBR R SSV
Fine-grained soils in
which silt and clay-
size particles
predominate
Low
75 to 120
2.5 to 3.5
10 to 22
2.3 to 3.1
Sands and sand-gravel
mixtures with
moderate amounts of
silt and clay
Medium
130 to 170
4.5 to 7.5
29 to 41
3.5 to 4.9
Sand and sand-gravel
mixtures relatively
free of plastic fines
High
180 to 220
8.5 to 12
45 to 52
5.3 to 6.1
Table 3.1 – Subgrade soil types and approximate support values
Estimating k value (ACI 330R-08)
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Table B.2—Soil characteristics pertinent to parking lot pavements
Typical Design
Values
Major Divisions Letter Name
Compressi-
bility and
Expansion
Drainage
character-
istics
Compaction
EquipmentCBR Subgrade
Modulus
k, pci
GW Well-graded gravels orgravel-sand mixtures, littleor no fines
Almostnone
Excellent
Crawler-type tractor,
vibratory compactor,rubber-tired roller,steel-wheeled roller
40-80 300-500
GP Poorly graded gravels orgravel-sand mixtures, littleor no fines
Almostnone
ExcellentCrawler-type tractor,vibratory compactor,rubber-tired roller,steel-wheeled roller
30-60 300-500
d Very slight Fair to poorRubber-tired roller,sheepsfoot roller; closecontrol of moisture
40-60 300-500GM
u
Silty gravels, gravel-sand-silt mixtures
SlightPoor to
practically
impervious
Rubber-tired roller,sheepsfoot roller
20-30 200-500
GravelandGravelly
Soils
GC Clayey gravels, gravel-sand-clay mixtures
SlightPoor to
practicallyimpervious
Rubber-tired roller,sheepsfoot roller
20-40 200-500
SWWell-graded sands orgravelly sands, little or nofines
Almostnone Excellent
Crawler-type tractor,vibratory compactor,rubber-tired roller
20-40 200-400
SPPoorly graded sands orgravelly sands, little or nofines
Almostnone Excellent
Crawler-type tractor,vibratory compactor,rubber-tired roller
10-40 150-400
d Very slight Fair to poorRubber-tired roller,sheepsfoot roller; closecontrol of moisture
15-40 150-400
SM
u
Silty sands, sand-siltmixtures Slight to
medium
Poor to
practicallyimpervious
Rubber-tired roller,
sheepsfoot roller
10-20 100-300
Coarse-grained
soils
Sand and
SandySoils
SCClayey sands, sand-claymixtures
Slight tomedium
Poor topracticallyimpervious
Rubber-tired roller,sheepsfoot roller
5-20 100-300
ML
Inorganic silts and veryfine sands, rock flour, siltyor clayey fine sands orclayey silts with slightplasticity
Slight tomedium Fair to poor
Rubber-tired roller,sheepsfoot roller; closecontrol of moisture
15 orless
100-200
CL
Inorganic clays of low tomedium plasticity,gravelly clays, sandyclays, silty clays, leanclays
MediumPracticallyimpervious
Rubber-tired roller,sheepsfoot roller
15 orless
50-150Silts andClays
LL<50
OL Organic silts and organicsilt-clays of low plasticity
Medium tohigh
Poor Rubber-tired roller,sheepsfoot roller
5 orless
50-100
MHInorganic silts, micaceousor diatomaceous finesandy or silty soils, elasticsilts
High Fair to poor Sheepsfoot roller,rubber-tired roller
10 orless
50-100
CH Inorganic clays of highplasticity, fat clays
High Practicallyimpervious
Sheepsfoot roller,rubber-tired roller
15 orless
50-150
Fine-GradedSoils
Silts andClaysLL>50
OHOrganic clays of mediumto high plasticity, organicsilts
HighPracticallyimpervious
Sheepsfoot roller,rubber-tired roller
5 orless
25-100
Highly Organic Soils Pt Peat and other highlyorganic soils
Very high Fair to poor Compaction notpractical
- -
Estimating
k value
Additional
guidance: ACI 330R-08, Appendix B
Table B.1 - Soil
characteristics pertinent to
parking lot pavements
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Is a subbase layer needed?
• “Subbase” is a layer of imported or improved
material between the natural site material
(subgrade) and the concrete
• Can result in higher k value for design and
slightly thinner section
– Probably can’t be justified on this basis
• May warrant consideration if:
– Construction platform is needed
– Subgrade is very poor quality
– Heavy truck traffic & load transfer concerns
– Pumping of subgrade is likely
• If used, k value for design can be adjusted
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Concrete strength – MOR vs. f’c
• Compressive strength (f’c) recommended for
acceptance & QC
• Modulus of rupture (MOR, as per ASTM C78)
used in design
• Relationship can be documented for any mix via
lab testing or can be estimated:
• Use Eq. 3-1 with smooth, rounded aggregates or
when no data exists (4000 psi f’c ≈ 505 psi MOR)
• Use Eq. 3-2 when materials data supports higher
MOR’s – usually with crushed, angular
aggregates (4000 psi f’c ≈ 630 psi MOR)
MOR (psi) = cf '8 (in.-lb units) (3-1) 1
MOR (psi) = cf '10 (in.-lb units) (3-2) 1
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Traffic categories used in the thickness table
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Axle-load
distributions used for
preparing Tables 3.3
and 3.4
ACI 330R-08
Appendix A, Table A.1
Axles per 1000 trucks Axle
load, kips Category A-1 Category B Category C Category D
Single axles
4 1693.31 1693.31 — —
6 732.28 732.28 — —
8 483.10 483.10 233.60 —
10 204.96 204.96 142.70 —
12 124.00 124.00 116.76 —
14 56.11 56.11 47.76 —
16 38.02 38.02 23.88 1000
18 — 15.81 16.61 —
20 — 4.23 6.63 —
22 — 0.96 2.60 —
24 — — 1.60 —
26 — — 0.07 —
Tandem axles
4 31.90 31.90 — —
8 85.59 85.59 47.01 —
12 139.30 139.30 91.15 —
16 75.02 75.02 59.25 —
20 57.10 57.10 45.00 —
24 39.18 39.18 30.74 —
28 68.48 68.48 44.43 —
32 69.59 69.59 54.76 2000
36 — 4.19 38.79 —
40 — — 7.76 —
44 — — 1.16 —
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Using the thickness table
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Keeping thickness in perspective…
• “Rules of thumb” work fine for many small projects.
• Actual overload failures due to insufficient thickness are rare.
• Most thickness design is conservative for assumed loads.
• More critical issues: – Is heavier traffic channelized?
– Subgrade / subbase uniformity
– Drainage & maintenance
So what’s really important here?
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Other design considerations
• Interior vs. edge loadings:
– Thickness table assumes interior loadings with moderate load transfer at joints
– Pavement edges or isolation joint sections may need thickening (or integral curbs) if they will receive wheel loads
– Thicken sections abutting flexible pavement (asphalt)
• Load transfer conditions:
– Higher levels of load transfer recommended for heavier design loads and higher truck volumes
• In-plane (sliding) forces:
– Special details suggested in areas of high vehicle turning or braking forces to prevent panel sliding
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Jointing and Reinforcement
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Joint design and layout affects performance
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Specimen stored in water
Drying Wetting / Drying, Heating / Cooling Shrinkage
S
welli
ng
Time
Typical concrete volume changes
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Shrinkage + Restraint = Cracking
Cracking results from combined effects of restraint and
shrinkage (drying and/or thermal)…
…whenever resulting tensile stresses exceed tensile strength.
Drying shrinkage and cracking
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Dry Wet
Differential shrinkage, warping / curling of slabs
• Can result from differential moisture created by
surface drying while the slab bottom remains wet
• Can also result from differential temperature
• Can cause loss of support near panel edges,
movement and faulting at joints, mid-panel cracking
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• Control the location, width,
and appearance of expected
cracks
• Facilitate construction
• Accommodate normal slab
movements
• Provide load transfer where needed
• Minimize performance
implications of any random
(unexpected) cracks
Objectives of jointing
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The extent of cracking due to key
influences is somewhat predictable;
joints can be spaced accordingly. RECOMMENDED
SPACING of JOINTS
FOR CRACK CONTROL
THICKNESS, IN. SPACING, FT.
4 8-10
5 10-12
6 12-15
7 14-15
8+ 15
Exception: good design may call for even closer
joint spacings due to load transfer considerations.
Spacing of joints based on cracking tendency
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Types of joints in concrete pavement
Control joint
Construction joint
Isolation joint
formed or slipped face
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Aggregate Interlock
Keyways Dowels
TIEBARS ≠ DOWELS! (not used for load transfer)
Load transfer joint details
Not Recommended!
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Round dowels – generally for 8”+ thickness
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Plate dowel systems
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When used, the purpose of secondary steel reinforcement is to keep cracks from opening. To do this, it must be located above the mid-thickness.
Steel reinforcement
Not Recommended!
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It is almost impossible to place
rolled wire mesh in the upper
thickness where it can function.
Rebar on chairs or welded rigid
mats perform better if steel is
called for.
Secondary steel reinforcement
is often misunderstood and can
rarely be justified in flatwork that
is properly jointed.
If steel is used, it should
generally be cut at all joints!
Steel reinforcement
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Today, unreinforced concrete is the most common design
for the majority of concrete pavements. Even heavy traffic
highways are built without steel reinforcement.
Unreinforced concrete pavement
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Control joint options
Control joints can be made by tooling a groove or pushing an
insert into plastic concrete, or by sawing a slot in hardened
concrete. The depth of the void must be at least 1/4 of the
slab thickness to weaken the section enough to make it crack.
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Tooled control joints
Advantages: • Simplest to make
• Most reliable crack initiation
Disadvantages: • Most noticeable joint
• Not smoothest for rolling wheels
• Not designed for sealers / fillers
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Saw-cut control joints
Advantages:
• Makes best sealant reservoir
• Not as noticeable
• Smooth ride
Disadvantages:
• Timing critical to success
• Least reliable crack initiation with gravel aggregates
• More expensive to make
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Saw-cut joints must be
made within 4-12 hours
after final finishing
This joint was sawed soon enough
This one was sawed too late
Timing of joint sawing – a critical factor
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Early entry “dry cut” saws
• Designed to initiate cracks
with a shallow cut made
much earlier than with
wet-cut saws
• Timing - the “window of
opportunity” is 1 to 2 hours
if shallow cuts are used
• Also used to cut t/4 or t/3
in normal timing windows
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Construction joints are used between separate concrete
placements, typically along placement lane edges. They may
use keyways or other features designed for load transfer.
Use of construction joints
Butt joints are
recommended for
most parking lots
where load transfer
needs are minimal.
Keyways are now only
recommended for entrance
drive / street longitudinal
construction joints ≥ 10”
thick and should be tied.
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Keyways as detailed in earlier documents
D
0.1D
0.2D
1:4 Slope
0.2D
Trapezoidal Half-round
This detail is no longer included in
ACI 330R or any ACPA references!
Not Recommended!
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Typical keyway joint performance issues
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…are sometimes called expansion joints but should generally not be used to provide for expansion. They provide no load transfer and should not be used as regularly spaced joints in a joint layout. Their proper use is to isolate fixed objects, providing for slight differential settlement without damaging the pavement.
Isolation joints
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Improper use of isolation joints
• If isolation joints are used as routine joints: – Slabs “crawl” as isolation
joints compress
– Adjacent control joints open
and fill with debris
– No load transfer
– Failure of sealants
– Water intrusion
• Common issue in construction practice
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Common details for isolation of fixtures
Diagonal
Isolation joint
Inlet
Isolation joint
Circular
Isolation joint
Square with Fillets
Isolation joint
Inlet - Round
Isolation joint
Telescoping Manhole
No boxout or isolation joint necessary
None
Isolation joint around perimeter
Square
Isolation joint
Reinforcing bars recommended to hold cracks tight
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Examples - isolation of fixtures
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• In many cases, control joints
and construction joints may
be used interchangeably,
depending on the preferred
direction of paving lanes.
• Load transfer requirements
must be considered.
• Isolation joints should be
avoided in traffic areas
except where differential
movement or settlement must
be accommodated (use
thickened edges).
The designer should prepare the jointing plan!
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Joint layout guidelines
• Things to Do
– Match existing joints or cracks
– Cut at the proper time
– Place joints to meet in-
pavement structures
– Adjust spacings to avoid
small panels or angles
– Intersect curves radially,
edges perpendicular
– Keep panels square
• Things to Avoid
– Slabs < 1 ft. wide
– Slabs > 15 ft. wide
– Angles < 60º (90º is best)
– Creating interior corners
– Odd Shapes (keep slabs
square)
– Offset (staggered) joints
– Isolation (unthickened) joints
in traffic areas
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Jointing layout – dealing with corners, acute angles, edges with extreme curvature
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Sealing of joints
• Topic of some debate
• Sealants must be maintained and drainage
design must be effective
• Low cost poured sealants not durable
• Some joint types difficult to seal
• Factors to consider in whether or not to
seal joints:
– Traffic level
– Soil types & local performance
– Subbase use
– Presence of wind blown debris
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Concrete Materials
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Concrete materials – what to specify / order
• Strength – Consistent with design
– More is not necessarily better
• Durability – Entrained air for freeze/thaw
– Sulfates, AAR considerations if applicable
• Other performance requirements – Economy
– Workability
– Lowest shrinkage potential
• Water content, slump • Aggregate size & grading
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Entrained air • Used to provide freeze-
thaw durability
• Requires extra QC attention, testing
Freeze-thaw
severity
zones severe
moderate
negligible
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• Pozzolanic benefits – Lower heat of hydration, reduced slump loss – Consumption of COH, less efflorescence – Higher ultimate strengths – Greater overall cementitious efficiency
• Improved concrete rheology and paste density – Lower water demand – Improved pumping & finishing – Reduced porosity & improved pore character – Improved consolidation & formed finishes
• Other chemistry interactions, durability benefits – Lower permeability – Sulfate resistance – Mitigation of aggregate reactivity
• Environmental benefits – Recycled materials – LEED, etc. – Reduced consumed energy to produce – Lower related CO2 emissions – Enhanced reflectivity with GGBFS
Supplemental cementitious materials – “SCMs”
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Construction best practices, options
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Pre-construction conference
• Indispensable in avoiding
problems and making the
project go smoothly
• Should cover all functions
and responsibilities
• Improves project quality
• Saves time and money
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• Compact with proper moisture content
• Check density with testing or proof rolling
• Fine grading
• Remove and replace soft or unsuitable soils
• Consider subgrade stabilization when
extremely poor soils are encountered
• Insure adequate surface drainage
• Water table depth - well below subgrade
• Uniformity is the key!
Subgrade preparation
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Drainage and subgrade issues: #1 cause of failures
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Compact granular
materials near
optimum moisture,
plastic soils slightly
above optimum.
106
103
94
97
100
109
8 10 12 14 16 18 20 22
Max. Density
Opt. Moisture
Density,
lb
/ft3
Moisture Content, %
95% Density
3% 1%
Compaction and moisture-density relationship
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• Major projects – use a
qualified testing firm
• Small projects & quick
checks – proof rolling
– Use if testing is
unavailable or
impractical, or to
supplement testing
– Use a loaded truck
– Establish and enforce a
criteria
– Can help to locate soft
spots, stump holes
Monitoring density
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Grading tolerances for the subgrade / subbase
• Deviations contribute to variations in concrete thickness
and influence drag restraint & cracking
• Suggested tolerances: within + ¼”, - ½” of design grade
• Tight tolerances are more critical for thin slabs
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Forming & placement sequencing
Of the different
sequencing options
used, the method of
paving in alternate
lanes (lower photo)
has been found most
efficient and also
helps minimize the
adverse effects of
shrinkage.
Not Recommended!
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Alternate lane slip-formed placement
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Should the subgrade be dampened prior to
concrete placement?
• No longer recommended
• Drier subgrades help to
equalize concrete
moisture loss, minimizing
slab curling
• ACI 330R-08:
“normally dry” subgrade
• Consider circumstances
Not Recommended!
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• Good strikeoff / screeding critical for surface tolerances
• Select slump based on paving equipment
• Avoid too much vibration in one place
• Limit use of bull float; straight-edging is preferred where vehicle speed > 5 mph
• Avoid: troweling, use of jitterbugs, any finishing steps while bleedwater is rising
• Jointing - saw within critical time window; make cuts / grooves at least 1/4 of thickness
• Texturing - use plenty!
• Curing - timing and effectiveness are critical
Concrete placement & finishing precautions
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Simple strikeoff equipment
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Basic vibrating screeds
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More sophisticated placement equipment
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Construction of “roll-over” integral curbs
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Bull floats vs. straight edges
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Residential finishing methods – not for paving!
Not Recommended!
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No power trowels!
Not Recommended!
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Thickened edges
Concrete at pavement edges or along isolation
joints that will support wheel loads should be
thickened to provide extra support.
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Example – thickened edge
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Providing surface texture
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Avoiding excessive cracking influences
• Monitor evaporation rate & take
appropriate steps when extreme
• Effective curing
• Repair subgrade ruts, minimize
other subgrade drag influences
• Effective curing
• Extra precautions in cool
weather or with slow strength-
gain mixes: apply curing sooner
and longer…
• Adequate strength before
opening to traffic
• Effective curing
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Curing effects on performance
• Reduces cracking
– Delay of drying
shinkage
– Minimizes warping
• Improves durability and
lowers permeability
• Facilitates most rapid
strength gain
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• Spray membrane curing
compound - ASTM C 309,
white pigmented preferred
• Timing is critical - spray
immediately after finishing
• Suggested application rate: – Maximum coverage: 200 ft2 / gal
– Higher rate (less coverage) for windy
or dry conditions
Curing compound – most common method
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• Rules of thumb:
– Automobile traffic in 3 days
– Truck traffic in 7 days
• Opening can be earlier if adequate strength has developed (2500+ psi)
• Fast track techniques can be used to open to traffic in just a few hours
Opening to traffic
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Too soon.
Opening to traffic
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Other information contained in ACI 330R
• Inspection and testing
• Maintenance and repair
• Suggested joint details
• Concrete overlays
– Over existing concrete
– Over asphalt
• Parking lot geometrics
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Parking lot geometrics
Small cars
Angle
Interlock
reduction Overhang
Vehicle
projection Aisle width Module widths
θ i o VP AW W1 W2 W3 W4 W5
45 deg 2 ft, 0 in. 1 ft, 5 in. 15 ft, 3 in. 11 ft, 6 in. 26 ft, 9 in. 42 ft, 0 in. 40 ft, 0 in. 38 ft, 0 in. 39 ft, 2 in.
50 deg 1 ft, 10 in. 1 ft, 6 in. 15 ft, 9 in. 12 ft, 0 in. 27 ft, 9 in. 43 ft, 6 in. 41 ft, 8 in. 39 ft, 10 in. 40 ft, 6 in.
55 deg 1 ft, 8 in. 1 ft, 8 in. 16 ft, 1 in. 12 ft, 10 in. 28 ft, 11 in. 45 ft, 0 in. 43 ft, 4 in. 41 ft, 8 in. 41 ft, 8 in.
60 deg 1 ft, 5 in. 1 ft, 9 in. 16 ft, 4 in. 13 ft, 4 in. 29 ft, 8 in. 46 ft, 0 in. 44 ft, 7 in. 43 ft, 2 in. 42 ft, 6 in.
65 deg 1 ft, 2 in. 1 ft, 10 in. 16 ft, 6 in. 14 ft, 0 in. 30 ft, 6 in. 47 ft, 0 in. 45 ft, 10 in. 44 ft, 8 in. 43 ft. 4 in.
70 deg 1 ft, 0 in. 1 ft, 11 in. 16 ft, 7 in. 14 ft, 10 in. 31 ft, 5 in. 48 ft, 0 in. 47 ft, 0 in. 46 ft, 0 in. 44 ft, 2 in.
75 deg 0 ft, 9 in. 1 ft, 11 in. 16 ft, 6 in. 16 ft, 0 in. 32 ft, 6 in. 49 ft, 0 in. 48 ft, 3 in. 47 ft, 6 in. 45 ft, 2 in.
90 deg 0 ft, 0 in. 2 ft, 0 in. 15 ft, 6 in. 20 ft, 0 in. 35 ft, 6 in. 51 ft, 0 in. 51 ft, 0 in. 51 ft, 0 in. 47 ft, 0 in.
Large cars
Angle
Interlock
reduction Overhang
Vehicle
projection Aisle width Module widths
θ i o VP AW W1 W2 W3 W4 W5
45 deg 2 ft, 4 in. 2 ft, 1 in. 18 ft, 0 in. 13 ft, 0 in. 31 ft, 0 in. 49 ft, 0 in. 46 ft, 8 in. 44 ft, 4 in. 44 ft, 10 in.
50 deg 2ft, 1 in. 2 ft, 4 in. 18 ft, 8 in. 13 ft, 8 in. 32 ft, 4 in. 51 ft, 0 in. 48 ft, 11 in. 46 ft, 10 in. 46 ft, 4 in.
55 deg 1 ft, 10 in. 2 ft, 5 in. 19 ft, 2 in. 14 ft, 8 in. 33 ft, 10 in. 53 ft, 0 in. 51 ft, 2 in. 49 ft, 4 in. 48 ft, 2 in.
60 deg 1 ft, 8 in. 2 ft, 7 in. 19 ft, 6 in. 16 ft, 0 in. 35 ft, 6 in. 55 ft, 0 in. 53 ft, 4 in. 51 ft, 8 in. 49 ft, 10 in.
65 deg 1 ft, 4 in. 2 ft, 9 in. 19 ft, 9 in. 17 ft, 0 in. 36 ft, 9 in. 56 ft, 6 in. 55 ft, 2 in. 53 ft, 10 in. 51 ft, 0 in.
70 deg 1 ft, 1 in. 2 ft, 10 in. 19 ft, 10 in. 18 ft, 4 in. 38 ft, 2 in. 58 ft, 0 in. 56 ft, 11 in. 55 ft, 10 in. 52 ft, 4 in.
75 deg 0 ft, 10 in. 2 ft, 11 in. 19 ft, 9 in. 20 ft, 0 in. 39 ft, 9 in. 59 ft, 6 in. 58 ft, 8 in. 57 ft, 10 in. 53 ft, 8 in.
90 deg 0 ft, 0 in. 3 ft, 0 in. 18 ft, 8 in. 24 ft, 8 in. 43 ft, 4 in. 62 ft, 0 in. 62 ft, 0 in. 62 ft, 0 in. 56 ft, 0 in.
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Summary – so what all is really important here?
• Subgrade support, subbase
• Proper thickness
• Jointing for crack control
• Load transfer design
• Pavement drainage design
• Materials & methods refined
to minimize shrinkage and
warping
• Special attention to curing
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Questions?
Tim Cost, PE, FACI Holcim (US) Inc.
Amy Miller, PE National Ready Mixed Concrete Association
Design and Construction of Concrete Parking Areas