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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 MeasuresQC 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 yd3 and
consists of sublots. Sublot has maximum of 100 yd3 and at least one sublot for each day’s placement.
8
Differences in Specifications
Item Current ERS
Mix Design Prescriptive Performance measures
Testing VDOT Contractor and
VDOT
Basis of Pay Minimum PWL (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
Material Amount (lb/yd3)
Cement Type I/II 318
Fly ash Class F 159
Slag 159
Fine aggregate 1101
Coarse aggregate 1755
w/cm 0.45
12
Salem Strength and Permeability at 28 days
Property Average Std Dev
Strength (psi) 5016 305
Permeability (coul)
391 72
N=31Minimum 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 SelectionRoute 624 over Cat Point Creek
In the same mixture• Crushed stone and
gravel• Water reducing
admixture and retarding admixture
15
Combined AggregatesRoute 5 over Chickahominy River
Quality coarse aggregate did not meet #57
16
Combined AggregatesRoute 5 over Chickahominy River
0
5
10
15
20
25
30
35
1 1/
23/
43/
8 #8 #30
#100 Pan
Sieve Size
Pe
rce
nt R
eta
ine
d
Noncompliant #57 with sand
Noncompliant #57 with #78 and sand
17
Curing BoxesRoute 95 Widening Project
Curing Box with continuous recording (printout)
18
Mixture ProportionsChincoteague Bridge Bascule Footing
83.5 ft by 51 ft and 7 ft deep
19
Mixture ProportionsChincoteague Bridge Bascule Footing
• In A3 Mass Concrete minimum cementitious material content is 588 lb/yd3.
• In this project used 539 lb/cy3 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
Ingredient A3 Concrete A4 Concrete
Portland cement 385 438
Fly ash 165 188
Total cementitious 550 626
Coarse agg #57 1340 1340
Coarse agg #78 460 460
Fine aggregate 1208 1137
w/cm 0.44 0.39
23
Strength and Permeability – Route 5
Value
A3 Str.(psi)
A3 Perm.(coul)
A4 Str.(psi)
A4 Perm.(coul)
Average 4570 456 4820 430
Std dev = SD 560 140 680 1155
Sublots 46 46 161 160
Over tidal water: USL=1700 coulombs
24
Control Charts Fresh Concrete
Slump Results
01234567
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Test Number
Inch
es
Air Content
0
2
4
6
8
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Test Number
Air
Co
nte
nt
Unit Weight
134
136
138
140
142
144
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Test Number
Un
it W
eig
ht
Temperature
0
20
40
60
80
100
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Test Number
Tem
per
atu
re
Compressive Strength (Avg)
0
1000
2000
3000
4000
5000
6000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Test Number
psi
(A
vera
ge)
Slump
Air content
Unit weight
Temperature
25
Control Charts Hardened Concrete
Compressive Strength (Avg)
0
1000
20003000
4000
5000
6000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Test Number
psi
(A
vera
ge)
Coulombs (Avg)
200300400500600700800900
1000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Test Number
Co
ulo
mb
e (A
vg)
Compressive Strength Moving Average (psi)
41004200430044004500460047004800
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Test Number
psi
(A
vera
ge)
Coulombs Moving Average
200300400500600700800900
1000
1 2 3 4 5 6 7 8 9 10 11 12 13 14Test Number
Co
ulo
mb
e (
Av
g)
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• QL = (Average – LSL)/s• Permeability
QU = (USL – Average)/s Q is the Quality Index, used to estimate
PWL (percent within limits) from TablesLSL: lower specification limitUSL: upper specification limits: sample standard deviation
29
Pay FactorPWL for strength and permeability:
• PF = 82 + 0.2 (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 StrengthDistrict Mean Std Dev n sublots AVG PF
Richmond 4570 560 46 100.2
Fredericksburg 3850 600 19 92.40
Fredericksburg 4700 530 18 101.20
Lynchburg 4010 460 7 95.40
Culpeper 4870 570 9 101.90
Bristol 4890 460 24 102.00
Staunton 4940 630 15 101.90
Hampton Roads 4760 550 82 101.20
NoVa 5230 800 54 101.30
Weighted average 4759 100.42
LSL = 3800 psi
31
A3 PermeabilityDistrict Mean Std Dev n USL AVG PF
Richmond 456 140 46 1700 102.00
Fredericksburg 1953 670 19 3200 101.00
Fredericksburg 1236 335 18 3200 102.00
Lynchburg 2670 1150 7 3200 95.40
Culpeper 1388 475 9 3200 102.00
Bristol 742 215 24 3200 102.00
Staunton 2080 430 15 3200 102.00
Hampton Roads 460 173 82 1700 102.00
NoVa 1075 345 26 3200 102.00
Wt avg USL1700 459 102.00
Wt avg USL 3200 1419 101.45
32
A4 StrengthDistrict Mean Std Dev n AVG PF
Richmond 4820 680 161 94.90
Fredericksburg 6210 645 6 102.00
Fredericksburg 6100 510 4 102.00
Fredericksburg 5580 575 24 101.90
Culpeper 5540 810 6 99.90
Bristol 5080 860 10 82.57
Staunton 6790 1400 8 101.60
Staunton 5030 535 16 97.40
Salem 5010 300 29 101.30
Hampton Roads 5670 743 80 101.00
NoVa 5660 680 23 100.60
NoVa 6000 760 30 101.70
Wt average 5288 98.04
LSL = 4500 psi
33
A4 PermeabilityDistrict Mean Std Dev n USL AVG PF
Richmond 430 155 160 1700 102.00
Fredericksburg 1090 160 6 2200 102.00
Fredericksburg 1060 48 4 2200 102.00
Fredericksburg 870 180 24 2200 102.00
Bristol 1080 300 7 2200 102.00
Staunton 1695 190 8 2200 102.00
Staunton 3150 1020 16 2200 84.80
Salem 390 72 29 2200 102.00
Hampton Roads 440 174 57 1700 102.00
NoVa 940 200 19 2200 102.00
NoVa 840 200 6 2200 102.00
Wt avg USL 1700 433 102.00
Wt avg USL 2200 1155 99.69
34
Summary
Class Property Average Mean n PF
A3 Strength Weighted (Wt) 4759 274 100.42
Perm Wt (USL 1700) 459 128 102.00
Wt (USL 3200) 1419 118 101.45
A4 Strength Wt 5288 98.04
Perm Wt (USL 1700) 433 217 102.00
Wt (USL 2200) 1155 119 99.69
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.