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Synthetic Fibers in Precast. Agenda What’s new Engineering & fiber performance Synthetic Fiber benefits Rework reduction Green strength Crack control Steel replacement Reduced cycle time Financial payoff Summary. Synthetic Fibers in Precast. What’s New

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slide1
Synthetic Fibers in Precast

Agenda

What’s new

Engineering & fiber performance

Synthetic Fiber benefits

Rework reduction

Green strength

Crack control

Steel replacement

Reduced cycle time

Financial payoff

Summary

slide2
Synthetic Fibers in Precast

What’s New

  • Steel price - greater need for a fiber alternate
  • Flexural reinforcement design - much wider uses
  • Macrofiber technology - new fiber capabilities
  • SCC technology - wider range of workability
  • Synthetic fiber - proven to reduce production cost
slide3
Synthetic Fibers in Precast

What’s new

graph: Engineering News Record 20-City average rebar price

Reinforcing steel price up sharply

  • Increase by 70% in 2004, additional increases forecast
  • Significant price reduction seems unlikely

Precast producers will probably benefit!

  • Contractors are seeking alternates to steel construction
  • Architects & engineers are changing designs to precast

Producers can get steel out of their product

  • Microfiber alternate to temperature/shrinkage steel
  • Macrofiber alternate to flexural steel
slide4
Synthetic Fibers in Precast

What’s new

Why use fibers in precast?

  • Steel replacement - lower production cost: labor & materials
  • Faster cycle time - lower plant overhead per unit
  • Green strength - faster cycle time, lower cost, higher production
  • Crack control - reduce rework costs, reduced rejects
  • Reduced spalls - reduced rework costs, faster cycle time
  • Appearance - reduced plant rework, reduced field cost
slide5
Synthetic Fibers in Precast

What’s new

  • Microfiber
    • Fine, fibrillated
    • Temp/Shrinkage steel alternate
  • Macrofiber
    • Coarse, monofilament, deformed
    • Flexural steel alternate
synthetic fibers in precast engineering advances
Synthetic Fibers in Precast Engineering advances

Three levels of concrete reinforcement based on area of steel ratio (AS)

  • Temperature/Shrinkage reinforcement AS = 0.1%
  • Flexural reinforcement AS < 0.4%
  • Structural reinforcement AS > 0.4%
synthetic fibers in precast engineering advances1
Synthetic Fibers in Precast Engineering advances

Reinforcement measured by area of steel ratio (As)

  • Example: #4 rebar cage @ 12” each way, 6” thick wall
    • #4 rebar = 0.20 sq. in.
    • Section = 6” x 12” = 72 sq inches
    • Ratio.0.20/72 x 100= 0.27%
  • Requirements for precast
    • 0.1% = ACI 318 Temperature/shrinkage minimum steel
    • 0.4% = Modulus of flexural rupture of concrete
synthetic fibers in precast engineering advances2
Synthetic Fibers in Precast Engineering advances

Fiber use by area of steel ratio (As)

  • Temperature/Shrinkage As=0.1%: Fibers clearly accepted
  • Flexural reinforcement: Fibers have proven effective
  • Structural reinforcement As>0.4%: Steel required
synthetic fibers in precast engineering advances illustration shows vacuum testing apparatus
Synthetic Fibers in Precast Engineering advancesIllustration shows vacuum testing apparatus

Septic Tanks – A flexural reinforcement test

    • Alabama tests - Vacuum tests per ASTM C 1227
      • (3) 1000 gal tanks- fiber reinforced – Failed at 9.5-10.5” Hg
      • Control tanks reinforced WWF - Failed at 4.2” Hg
    • California tests - Vacuum tests per ASTM C 1227
      • (3) 1000 gal tanks- fiber reinforced – sustained 10.0” Hg w/o failure
  • 10” hg is greater than 700 lbs/SF
      • Substantially exceeds typical earth loads
      • Provides confidence in design calcs.
synthetic fibers in precast engineering advances3
Synthetic Fibers in Precast Engineering advances

Septic Tanks – IAPMO Spec PS 1-2003

  • Establishes the standard of quality for septic tanks
    • Concrete & reinforced plastic
    • Includes design requirements for fiber reinforcement
    • Accepted in many jurisdictions
  • Design Calculations are provided
    • As by wall thickness requirement
    • As converted to ASTM C-1399 flexural moment of resistance
    • (Standard Test Method for Determining Average Residual Strength in Fiber Reinforced Concrete)
    • Procedure for establishing fiber ASTM C-1399 values (ARS)
synthetic fibers in precast engineering advances4
Synthetic Fibers in Precast Engineering advances

Septic Tanks – IAPMO Spec PS 1-2003

synthetic fibers in precast engineering advances5
Synthetic Fibers in Precast Engineering advances

ASTM C 1399 Average Residual Strength

  • Crack the beam with spring-steel plate under
  • Remove the steel plate
  • Measure deflection under load (w/o PL)
  • Average residual strength formula
    • Section (sq.in.)
    • Span length
  • Test 5 beams
  • ARS is a measure of post-crack strength (the level of load sustained by fibers in a concrete beam after the beam is cracked)
synthetic fibers in precast engineering advances6
Synthetic Fibers in Precast Engineering advances

ASTM C 1399 - 5 pcy

Average Residual Strength (ARS): 215 psi

synthetic fibers in precast engineering advances7
Synthetic Fibers in Precast Engineering advances

Area of steel = ARS values for synthetic fibers

slide15
Synthetic Fibers in Precast

Agenda

What’s new

Engineering & fiber performance

Synthetic Fiber benefits

Rework reduction

Green strength

Crack control

Steel replacement

Reduced cycle time

Dosage

Financial payoff

Summary

slide16
Synthetic Fibers in PrecastRework Reduction

Rework Reduction

Extra cost to repair out of spec product.

The cost of not doing it right the first time.

Often not well recorded, can exceed 5% of total costs

The rule of 10

  • It costs 10x as much to fix it in the yard as doing it right in the plant
  • It costs 10x as much to fix it on the job as does in the yard
slide17
Synthetic Fibers in Precast Rework Reduction

Green Strength

Improved early age handling strength (Green Strength)

  • Allows faster cycle times
  • Provides assurance against stripping/handling damage
slide18
Synthetic Fibers in Precast Rework Reduction

Cracked or spalled product

  • Shrinkage cracks during initial cure
  • Handling cracks when product is relatively green
  • Stripping shear or impact damage
slide20
Synthetic Fibers in PrecastSteel reinforcement alternate

Area of steel determination

  • Determined by producer’s engineer
  • Measured at a vulnerable section
slide21
Synthetic Fibers in PrecastSteel reinforcement alternate

Dosage Determination

  • Per IAPMO PS 1-2003
  • Partial steel replacement above AS = 0.4%
slide22
Synthetic Fibers in PrecastSteel reinforcement alternateIllustration shows vacuum testing utility vault, 20” Hg (1400 PSF)

Application to Underground 6-sided Products

  • Septic tanks
  • Utility vaults
  • Catch basins
  • Weirs
  • Drop inlets
  • Grease traps
  • Burial vaults

Underground round products

  • Manhole risers
  • Dry wells
  • RCP
synthetic fibers in precast cycle time reduction
Synthetic Fibers in PrecastCycle time reduction

Cycle time

The time to set, cast, cure and strip 1 piece

The basis of labor cost and plant burden.

Use of fiber reduces cycle time

  • Green strength can mean stripping 2 hours earlier
  • Eliminate steel means no cage to reset
  • Reduced rework means rework product does not clutter plant
  • Reduced rework means less supervisory burden
slide24
Synthetic Fibers in PrecastDosage

Exceed the minimum dose

Alternate to Temp/Shrinkage steel

  • Temp steel .10%, come up to the full design
  • Allows for manufacturing & handling variation

Alternate to flexural steel

  • Allows for manufacturing & handling variation
  • Reject pile – why take a chance?
slide25
Synthetic Fibers in Precast

Agenda

What’s new

Engineering & fiber performance

Synthetic Fiber benefits

Rework reduction

Green strength

Crack control

Steel replacement

Reduced cycle time

Dosage

Financial payoff

Summary

slide26
Synthetic Fibers in PrecastFinancial Payoff

Payoff for fiber use – Septic Tank Example

slide27
Synthetic Fibers in PrecastSummary

Fiber reduces production cost

Rework reduction

  • Green strength
  • Crack control

Steel replacement

  • Steel savings and fiber costs are similar
  • Reduced labor costs

Reduced cycle time

  • Increased production
  • Lower burden
slide28
Synthetic Fibers in PrecastSummary

There is a lot that’s new in synthetic fibers

  • Steel price – renewed need for a fiber alternate
  • New engineering - flexural reinforcement design
  • New fibers - macro fiber technology
  • New admixtures - SCC workability

Engineering

  • IAPMO septic tank spec and vacuum testing shows the way
  • Fibers are becoming accepted in underground products
  • Pipe & manholes must overcome ASTM requirement

Producers are using fibers and gaining confidence

  • Fiber manufacturers are responsive
  • Operational problems are being overcome
  • Financial results are encouraging
slide29
Synthetic Fibers in PrecastSummary

Who is Bill Ray

  • Principal at Precast Consulting
  • Background
    • Business owner PCI certified producer
    • General manager Sales exceeding $15 million
    • Project manager Projects exceeding $ 10 million
    • Chief fin. Officer Sales exceeding $150 million
    • Education
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