Update on End Result Specifications Celik Ozyildirim, Ph.D., P.E.

2 ACKNOWLEDGMENTS Close cooperation between Research Council Materials Division Structure and Bridge Division Districts FHWA Industry

3 ERS Shared responsibility Contractor/producer has the authority to prepare concrete mixtures and are expected to take responsibility for performance. Agency accepts, rejects, or applies a pay adjustment depending on the degree of compliance.

4 ERS Special Provision has three parts: 1.Process control measures QC Plan by the contractor applicable to preconstruction and during construction 2.Mix design approval 3.Acceptance

5 1.Process Control Measures QC Plan by the Contractor Personnel, equipment, supplies and facilities Ingredients Mix designs Sampling, type of test and frequency Certified technicians Complete record of tests

6 2. Mix Design Approval Contractor submits mix designs for various classes of concrete Documentation showing requirements are met –past experience –trial batches Mix designs, ingredients, target w/cm, target fresh and hardened concrete properties

7 3. Acceptance Screening tests, contractor Pay factor tests, VDOT For structural, paving, and miscellaneous concrete Accepted on a lot-by-lot basis Lot is limited to 500 yd 3 and consists of sublots. Sublot has maximum of 100 yd 3 and at least one sublot for each day’s placement.

8 Differences in Specifications ItemCurrentERS Mix DesignPrescriptivePerformance measures TestingVDOTContractor and VDOT Basis of PayMinimumPWL (percent within limits)

9 First Phase Pilot Projects Salem: Route 11 over the New River and Norfolk Southern Railroad tracks near Radford University, deck concrete Culpeper: Route 28 near Manassas, deck and substructure

10 Salem

11 Salem Mix Proportions MaterialAmount (lb/yd 3 ) Cement Type I/II318 Fly ash Class F159 Slag159 Fine aggregate1101 Coarse aggregate1755 w/cm0.45

12 Salem Strength and Permeability at 28 days PropertyAverageStd Dev Strength (psi) Permeability (coul) N=31 Minimum strength = 4,000 psi, Maximum permeability = 2,500 coulombs

13 Second Phase Pilot Projects Aggregate and admixture selection Combined aggregates Curing boxes Mixture proportions Control charts

14 Aggregate and Admixture Selection Route 624 over Cat Point Creek In the same mixture Crushed stone and gravel Water reducing admixture and retarding admixture

15 Combined Aggregates Route 5 over Chickahominy River Quality coarse aggregate did not meet #57

16 Combined Aggregates Route 5 over Chickahominy River

17 Curing Boxes Route 95 Widening Project Curing Box with continuous recording (printout)

18 Mixture Proportions Chincoteague Bridge Bascule Footing 83.5 ft by 51 ft and 7 ft deep

19 Mixture Proportions Chincoteague Bridge Bascule Footing In A3 Mass Concrete minimum cementitious material content is 588 lb/yd 3. In this project used 539 lb/cy 3 of cementitious material content with 30% Class F fly ash.

20 Mixture Proportions Route 5 over Chickahominy River

21 Mixture Proportions Route 5 over Chickahominy River Three trial batches with different cementitious material and w/cm

22 Mixture proportions – Route 5 IngredientA3 ConcreteA4 Concrete Portland cement Fly ash Total cementitious Coarse agg # Coarse agg #78460 Fine aggregate w/cm

23 Strength and Permeability – Route 5 Value A3 Str. (psi) A3 Perm. (coul) A4 Str. (psi) A4 Perm. (coul) Average Std dev = SD Sublots Over tidal water: USL=1700 coulombs

24 Control Charts Fresh Concrete Slump Air content Unit weight Temperature

25 Control Charts Hardened Concrete Compressive strength Permeability Str. moving average of 3 Perm. moving average of 3

26 Control Charts

27 Pay Factor Pay factor based on PWL Compressive strength Permeability Pay as in the current spec Rideability Thickness (pavements)

28 Estimating PWL Compressive strength Q L = (Average – LSL)/s Permeability Q U = (USL – Average)/s Q is the Quality Index, used to estimate PWL (percent within limits) from Tables LSL: lower specification limit USL: upper specification limit s: sample standard deviation

29 Pay Factor PWL for strength and permeability: PF = (PWL) PF IS NOT ENFORCED IN PILOT PROJECTS. 100% pay for PWL = 90% Average pay factor: C1(Perm)+C2(Str)/(C1+C2) C is a weighting factor Total pay factor = Average pay factor times unit bid price plus the additional price adjustment for deficient thickness (pavement) and incentive or disincentive for the ride quality.

30 A3 Strength DistrictMeanStd Devn sublotsAVG PF Richmond Fredericksburg Fredericksburg Lynchburg Culpeper Bristol Staunton Hampton Roads NoVa Weighted average LSL = 3800 psi

31 A3 Permeability DistrictMeanStd DevnUSLAVG PF Richmond Fredericksburg Fredericksburg Lynchburg Culpeper Bristol Staunton Hampton Roads NoVa Wt avg USL Wt avg USL

32 A4 Strength DistrictMeanStd DevnAVG PF Richmond Fredericksburg Fredericksburg Fredericksburg Culpeper Bristol Staunton Staunton Salem Hampton Roads NoVa NoVa Wt average LSL = 4500 psi

33 A4 Permeability DistrictMeanStd DevnUSLAVG PF Richmond Fredericksburg Fredericksburg Fredericksburg Bristol Staunton Staunton Salem Hampton Roads NoVa NoVa Wt avg USL Wt avg USL

34 Summary ClassPropertyAverage MeannPF A3StrengthWeighted (Wt) PermWt (USL 1700) Wt (USL 3200) A4StrengthWt Perm Wt (USL 1700) Wt (USL 2200)

35 INDUSTRY CONCERNS Pay adjustment: Bonus is for the contractor, penalty for the producer. Sublot’s include day’s production, which is usually a small amount of concrete. Small amounts: not economical and affects analysis Concrete classes: not enough samples Introduce one class concrete for the bridge structures: high quality concrete is needed throughout the structure No bonus if any lot has less than 90% PWL (“death clause”). Ensure no major maintenance to any section during service life.

36 DISCUSSION AND CONCLUSIONS Innovation possible: contractors/producers design mixtures Performance parameters specified Emphasize QC testing by the contractor Prequalification Cement reduction possible Includes standard deviation: reduced variability Allow mix design approval process from ERS as an option

Thank you. Celik Ozyildirim, Ph.D., P.E.