Fast Track Concrete
CIMT 210
I.
Examples:
•
•
•
•
•
Tolls roads
Public Streets
Intersections
Airport
Other
II. Specifications
• Planning and Construction
• Materials
• Joint and Sealing
• Curing and Temperature
• Testing
• Opening Traffic
III. Mix Design
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Examples
•Toll Roads
Tollway authorities lose revenue when lane
are shut down and there is much congestion,
forcing drivers to find alternate routes
•Public Street
Residents can gain access to their driveway
within 24 hours if they live on urban streets
•Intersections
Intersection suffer more pavement distress
because they connect 2 or more streets. Fast
track allows intersections to completed
before rush hour
•Airports
Fast track concrete allows contractor to
operate slipform equipment on the initial
paving lanes sooner than normal.
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Examples
•Airports
Initial paving lanes
Interior lanes
Paving interior lanes on an airport facility (note
theuse of initial lanes for construction platform)
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Specifications
•Planning and Construction
• Check access for local traffic
•Evaluate Local Business Interuption
•Check for any utility work.
•Secure access for equipment and operation
•Check pavement edge drop-off requirement
•Check for crossovers that disrupt both
directions of traffic
•Evaluate detour routes for level of
congestion and damage to road due to
prolong construction activity
•By specifying fast track concrete near the
end of the day will facilitate startup for next
day.
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Specifications
Planning and Construction – no special equipment
is required for construction
Well planned construction sequences are
necessary for the accelerated process
Constructing test slabs will help inexperienced
workers to work with the plastic properties of
fast track concrete
Concrete haul distance should be considered
Agencies should not modify their smoothness
specifications for fast track concrete
pavements.
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•Materials
Specifications
There is no specific proportioning necessary for
fast track concrete.
Refer to: ASTM C 150 Type I and III cements
MATERIAL
TYPE
QUANTITY
CEMENT
ASTM C150 700 - 800
TYPE I,III #/cy
FLY ASH
ASTM C618 0 - 80 #/cy
CLASS C
AGG. RATIO Coarse/Fine 1:1 -1.5:1
W/C+FLYASH
AIR
ENTRAINED
WATER REDUCERS
0.37-0.43
ASTM
C260
ASTM
C494
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As
Necessary
As
Necessary
•Materials
Specifications
Cement – ASTM C 150 Type I and III
cements
High levels of tricalcium silicates (C3S) and
finely ground cement particles will generate
strength quickly.
Type III cement, which is finer than other PC,
develops early strengths
The problems with Type III are false sets, and a
demand for excessive water and air entraining
Type I and II require chemical admixtures to
gain early strength.
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•Materials
Specifications
Pozzolanic Materials – Fly Ash or Ground –
Granulated Blast Furnace slag
These pozzalanic materials extend strength
gained, because tricalcium silicates (C3S)
do not extend
Fly Ash Class C and F
Class C will lower water demand, improve
workability and increase long term strength
Class F will not contribute to early strength, but
will extend long term strength, reduce
permeability, and will combat the effects of
deleterious materials, sulfates or alkalis
Flyash can slow down hydration and the final
set, due to the temperature drops in hydration.
(addition of admixtures is required)
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•Materials
Specifications
Air- Entraining Admixtures –are used to
entrain microscopic air bubbles
Entrained air improves concrete durability by
reducing the effects of Freeze/thaw behavior
Fast Track concrete needs the appropriate air
content of 4.5% to 7.5%.
Higher percentages of entrained air can reduce
the early and long-term strength, while lower
percentages will reduce the concrete durability.
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Specifications
•Materials
Water – Reducing Admixtures reduce the
water required for workability
These admixtures can also increase early
strength by lowering the quantity of water
necessary for hydration.
Water reducers lowers the number of cement
particles agglomerations and disperse cement
particles.
Type I is most effective in early strength with
water reducers..
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Specifications
•Materials
Accelerating Admixtures –aids strength
development and reduce initial set times by
increasing the reaction rate of tricalcium
silicates (C3S)
Accelerating admixtures generally consist of
soluble inorganic salts or soluble organic
compounds
Calcium Chloride (CaCl2) is the most common
accelerator, but is a corrosive to the reinforcing
steel.
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•Materials
Specifications
Aggregates – Grading – There is a definite
relationship between aggregate grading
uniformity and concrete strength, workability
and long –term durability
Workability –concrete with a well graded
combined aggregate will often be much
workable at a low slump than a poorly graded
mixture having a higher slump.
Slump- measure consistency between
batches, is affected by a difference of 3.5
inch when comparing a uniform grading
over a similar gap graded mix. The amount
of water in the mix controls. (20-30 lbs
difference)
Particle Shape and Texture – Sharp
particles are less workable than rounded
particles, but add to strength.
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•Materials
Specifications
Water – Hydration is an exothermic process
Raising the Heat of Water can accelerate the
process of hydration. (i.e. small projects, and
intersections reconstruction)
Hot water is a catalyst for early hydration but it
only good for short term. Several hours of heat
containment require insulation for rapid
strength gain.
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Specifications
•Joint and Sealing
• Sawing – the time for sawing (sawing window) is
reduced with Fast Track concrete.
•Light saws which handle easy and are more
versatile are more effective in Fast Track Concrete
•Curing blanket is normally in place during the
sawing operation and have to be removed
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Specifications
•Joint and Sealing
• Mixes with softer limestone aggregate require
less strength for sawing than do mixes with harder
coarse aggregate
•Contractors have successfully cut joints in fasttrack construction using wet-sawing, dry-sawing
and ultra – light sawing
•Dry saw cutting can be performed earlier than
wet-saw cutting
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Specifications
•Joint and Sealing
• Liquid sealant - Cleaning is the most important
aspect of joint
•Reservoir faces require a thorough cleaning to be
sure of good sealant adhesion
•Proper cleaning after wet sawing requires
mechanical action and pure water flushing to
remove contaminants
•Dry Sawing requires only an air blowing operation
to remove particulate residue from the joint
reservoir. (excessive dust is produced)
•Preformed seals are not sensitive to dirt or
moisture on side walls and may allow sealing
earlier than any liquid seal.
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Specifications
•Curing and Temperature Maintenance – is
important for the hydration within the concrete and
also to prevent thermal cracking.
Monitoring of heat is required, so that
contractors can adjust curing measures
Maturity testing allows for the field
measurements of the concrete temperature to
correlate with the gained strength
(see non-destructive testing)
Curing Compounds are liquid – membranes
meeting ASTM C309. The materials create a
seal that limits evaporation of mix water. The
white color also reflects solar radiation
Class A liquid curing compounds are sufficient
for fast track concrete
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Specifications
•Curing and Temperature Maintenance –
(Continued)
Blanket Insulation – provide a uniform
temperature environment for the concrete. It
keeps the area dampened and reduce heat loss.
Contractor will usually place blankets soon
after applying curing compound
It is recommended that blankets should be
applied after joint sawing is completed
Sawing Window – The sawing window is a
short period after placement when the concrete
can be cut successfully before it cracks.
The window ends when significant concrete
shrinkage occurs and induces uncontrolled
cracking.
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Specifications
•Curing and Temperature Maintenance –
(Continued)
Plastic Shrinkage – forms after concrete
placement due to rapid evaporation of water at
the surface of the slab.
•Ways to prevent evaporation conditions:
To pave during the evening or nighttime
To water mist aggregate stockpiles and subbase
To use evaporative retardant
When evaporation rate exceeds 0.2 #s/sft/hr
then plastic shrinkage cracking is likely to
occur.
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Specifications
•Testing – Non- Destructive
Maturity Testing – provides strength
evaluation through monitoring of internal
concrete temperature in the field.
The Nurse-Saul Method – calculates the timetemperature factor
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Specifications
•Testing – Non- Destructive (Maturity Test)
•Arrhenius Maturity Equation –
See ASTM C 1074
•Field maturity begins with embedment of
thermocouples or temperature probes and then
compared to the laboratory study.
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Specifications
•Testing – Non- Destructive (Pulse Velocity)
•Pulse-Velocity – measured the time required
for an ultrasonic wave to pass through concrete
from one transducer to another.
•The velocity of the wave correlates to
concrete strength or stiffness.
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Specifications
•Opening Traffic
• Third –Point Flexural Strength (psi) –
required to determine when roads should be
open for traffic.
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Specifications
•Opening Traffic
The strength necessary to allow vehicles onto a
new pavement will depend on the following
factors:
•Type, weight, and number of anticipated loads
during early-age period
•Location of loads on slab
•Concrete Modulus of Elasticity
•Pavement Design (new construction,
unbonded overlay, bonded overlay, or overlay
on asphalt)
•Slab Thickness
•Foundation Support (Modulus of Subgrade
Reaction, K)
•Edge support condition (widened lane or tied
curb & gutter or tied concrete shoulder)
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Specifications
•Opening Traffic
Construction Traffic - typical construction
vehicles include span saws, haul trucks and
water trucks.
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Specifications
•Opening Traffic
Public Traffic - Flexural strength requirement
for opening concrete pavements to use by
public traffic. Traffic is an estimate of the total
one-way ESAL’s that will use the pavement
truck lane between time of opening and the
time concrete reaches design strength (28 days)
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Mix Design
Various Mix Designs for
Various Projects
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