I.Examples: Tolls roads Public Streets Intersections Airport Other II. Specifications Planning and...

CONCRETE INDUSTRY MANAGEMENT TECHNOLOGY

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

Fast Track Concrete

CIMT 210


Examples•Toll Roads

Tollway authorities lose revenue when lane are shut down and there is much congestion, forcing drivers to find alternate routes

•Public StreetResidents 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

•AirportsFast track concrete allows contractor to operate slipform equipment on the initial paving lanes sooner than normal.


Examples

•Airports

Paving interior lanes on an airport facility (note theuse of initial lanes for construction platform)

Initial paving lanes

Interior lanes


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.


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.


Specifications•MaterialsThere 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 TYPE I,III

700 - 800 #/cy

FLY ASH ASTM C618 CLASS C

0 - 80 #/cy

AGG. RATIO Coarse/Fine 1:1 -1.5:1

W/C+FLYASH 0.37-0.43

AIR ENTRAINED

ASTM C260

As Necessary

WATER -REDUCERS

ASTM C494

As Necessary


Specifications•MaterialsCement – 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.


•MaterialsPozzolanic 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 FClass 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)

Specifications


Specifications•Materials

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.


Specifications

•MaterialsWater – 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..


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.



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.



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.


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


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 fast-track construction using wet-sawing, dry-sawing and ultra – light sawing

•Dry saw cutting can be performed earlier than wet-saw cutting


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.


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


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.


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 nighttimeTo water mist aggregate stockpiles and subbaseTo use evaporative retardant

When evaporation rate exceeds 0.2 #s/sft/hr then plastic shrinkage cracking is likely to occur.


Specifications•Testing – Non- Destructive

Maturity Testing – provides strength evaluation through monitoring of internal concrete temperature in the field.

The Nurse-Saul Method – calculates the time-temperature factor


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.


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.


Specifications•Opening Traffic

• Third –Point Flexural Strength (psi) – required to determine when roads should be open for 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)



Construction Traffic - typical construction vehicles include span saws, haul trucks and water trucks.



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)


Mix Design

Various Mix Designs for Various Projects

Date post:	22-Dec-2015
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