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1 Synthetic Fibers in Precast Agenda What’s new Engineering & fiber performance Synthetic Fiber benefits –Rework reduction Green strength Crack control.

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Presentation on theme: "1 Synthetic Fibers in Precast Agenda What’s new Engineering & fiber performance Synthetic Fiber benefits –Rework reduction Green strength Crack control."— Presentation transcript:

1 1 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

2 2 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 Synthetic Fibers in Precast

3 3 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 Synthetic Fibers in Precast What’s new graph: Engineering News Record 20-City average rebar price

4 4 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 Synthetic Fibers in Precast What’s new

5 5 Synthetic Fibers in Precast What’s new Microfiber –Fine, fibrillated –Temp/Shrinkage steel alternate Macrofiber –Coarse, monofilament, deformed –Flexural steel alternate

6 6 Synthetic Fibers in Precast Engineering advances Three levels of concrete reinforcement based on area of steel ratio (A S ) Temperature/Shrinkage reinforcement A S = 0.1% Flexural reinforcement A S < 0.4% Structural reinforcement A S > 0.4%

7 7 Synthetic Fibers in Precast Engineering advances Reinforcement measured by area of steel ratio (A s ) –Example: #4 rebar 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

8 8 Synthetic Fibers in Precast Engineering advances Fiber use by area of steel ratio (A s ) –Temperature/Shrinkage A s =0.1%: Fibers clearly accepted –Flexural reinforcement: Fibers have proven effective –Structural reinforcement A s >0.4%: Steel required

9 9 Synthetic Fibers in Precast Engineering advances Illustration 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 ” 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.

10 10 Synthetic Fibers in Precast Engineering advances Septic Tanks – IAPMO Spec PS 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 –A s by wall thickness requirement –A s 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)

11 11 Synthetic Fibers in Precast Engineering advances Septic Tanks – IAPMO Spec PS

12 12 Synthetic Fibers in Precast Engineering advances ASTM C 1399 Average Residual Strength 1.Crack the beam with spring-steel plate under 2.Remove the steel plate 3.Measure deflection under load (w/o PL) 4.Average residual strength formula Section (sq.in.) Span length 5.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)

13 13 Synthetic Fibers in Precast Engineering advances ASTM C pcy Average Residual Strength (ARS):215 psi

14 14 Synthetic Fibers in Precast Engineering advances Area of steel = ARS values for synthetic fibers

15 15 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

16 16 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 Synthetic Fibers in Precast Rework Reduction

17 17 Green Strength Improved early age handling strength (Green Strength)  Allows faster cycle times  Provides assurance against stripping/handling damage Synthetic Fibers in Precast Rework Reduction

18 18 Cracked or spalled product  Shrinkage cracks during initial cure  Handling cracks when product is relatively green  Stripping shear or impact damage Synthetic Fibers in Precast Rework Reduction

19 19 Steel Costs – stated $/yard Synthetic Fibers in Precast Steel reinforcement alternate

20 20 Area of steel determination –Determined by producer’s engineer –Measured at a vulnerable section Synthetic Fibers in Precast Steel reinforcement alternate

21 21 Dosage Determination –Per IAPMO PS –Partial steel replacement above A S = 0.4% Synthetic Fibers in Precast Steel reinforcement alternate

22 22 Synthetic Fibers in Precast Steel reinforcement alternate Illustration 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

23 23 Synthetic Fibers in Precast Cycle 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

24 24 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? Synthetic Fibers in Precast Dosage

25 25 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

26 26 Payoff for fiber use – Septic Tank Example Synthetic Fibers in Precast Financial Payoff

27 27 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 Synthetic Fibers in Precast Summary

28 28 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 Synthetic Fibers in Precast Summary

29 29 Who is Bill Ray Principal at Precast Consulting Background –Business ownerPCI certified producer –General managerSales exceeding $15 million –Project managerProjects exceeding $ 10 million –Chief fin. OfficerSales exceeding $150 million –Education MBA University of Chicago BS Florida state Contact info: Synthetic Fibers in Precast Summary


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