block 26 acceptance 13
TRANSCRIPT
Construction QC/QA Acceptance 1
Quality control/quality assurance
Acceptance
Senior/GraduateHMA Course
Construction QC/QA Acceptance 2
What you will learn….
• The acceptance and compliance procedures used for hot mix asphalt
Construction QC/QA Acceptance 3
ACCEPTANCE AND COMPLIANCE
Did We Get What We Ordered?
Construction QC/QA Acceptance 4
How do we set the spec limits
• They are set using typical industry standard deviations
• Then allowing three standard deviations from the target
• When setting the limits – the number of tests to be included in the lot are considered
• The more tests – the tighter the specification
Construction QC/QA Acceptance 5
Typical Industry Standard Deviations
• Based on extraction• Asphalt binder content: + 0.25 %• % Passing 4.75 mm (No. 4) and larger
sieves: + 3 %• % Passing 2.36 (No 8) to .150 mm (No 100)
sieves: + 2 % • Passing the 0.075 mm (No 200) sieve: + 0.7
%
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Typical Industry Standard Deviations (cont.)
• Compacted mix
• Air voids: + 1.0 %
• Voids in Mineral Aggregate (VMA): + 1.5 %
• Voids filled with asphalt (VFA): + 5 %
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Equation
• The following equation is used to set limits.
• S(n) = s / n ½
• Where– S(n) = standard deviation based on
sample size n– S = standard deviation for material– n = sample size
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Example
• Thus for asphalt binder content where 4 samples will make up the lot size the spec limits would be:
• S = 0.25 and n = 4• S(n) = 0.25 / square root (4)• S(n) = 0.125• For three standard deviations the spec limits would
be plus/minus 0.375 %.
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Percent Within Limits
Construction QC/QA Acceptance 10
PWL Concept
% AC
PWL
PU
PL
USL
LSL
PWL = (PU + PL) - 100
In Terms of Area of the Distribution
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Percent Within Limits
Lot X s PWL
1 5.0 0.20 96
2 5.0 0.40 68
Target Value 5.0
Limits ± 0.4
Lot 1
Lot 2
Asphalt Binder Content4.2 4.6 5.0 5.4 5.8
Upper limit
Lower limit
target
Spec Data
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Percent Within Limits
Lot X s PWL
1 5.0 0.20 96
2 4.8 0.20 84
Lot 1Lot 2
Asphalt Binder Content4.2 4.6 5.0 5.4 5.8
Target Value 5.0
Limits ± 0.4 target
Upper limitsLower limit
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PWL Approach
To get 100 % pay you need to pay attention to
both accuracy and precision
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Steps
• Sample the material using an appropriate random number system
• Determine the average for the lot• Determine the standard deviation “s” for each lot• For Air voids, VMA and binder content calculate the
upper and lower quality indices and the associated PWL
• For in-place density, calculate the lower quality index and associated PWL
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Percent Within Limits Using Standard Deviation
EXERCISE
Calculation of
PWL and PD
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Equations
Q(u) =
Q(L) =
USL - x
x - LSL s
s
-
-
1. Determine Random Sample Location Within Lot
2. Make Measurements at Locations or on Material Samples
3. Determine Average of Samples:
4. Determine Standard Deviation of Samples:
Acceptance Plan:Percent Within Limits (PWL) Approach
x = xi
nn
i=1
s = (xi - x)2
n-1ni=1
Acceptance Plan:Percent Within Limits (PWL) Approach
5. Determine Upper Quality Index, Qu:
6. Determine Lower Quality Index, QL:
7. Estimate PU and PL From Table Using Calculated QU and QL
8. Total Percent Within Limits = (PU + PL) - 100
QL = (x - L)
s
QU = (U - x)
s
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Example Problem
• Percent passing 0.075 sieve– Test 1 : 4.1– Test 2: 4.5– Test 3: 4.8– Test 4: 5.0– Test 5: 5.1
• Specification Target: 5.0 %• Allowable tolerance: See next slide
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Set Spec Limits
• The typical standard deviation from industry is 0.7 %; therefore:– S = 0.7 and n = 5– S(n) = 0.7 / square root (5)– S(n) = 0.7/2.236 = 0.313
• For three standard deviations the spec limits would be + 0.94 %.
• Therefore:– Upper spec limit = 5.94 %– Lower spec limit = 4.06 %
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Compute values
• The average is: – 4.72 %
• Standard deviation for data is:– 0.43
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Compute QU
Q(u) = USL - x s
-
Q(u) =
Q(u) = 2.83
5.94 - 4.72 0.43
P(u) = > 1.00
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Compute QL
Q(L) =
Q(L) =
x - LSL
4.72 - 4.06 0.43
s
-
Q(L) = 1.53
P(L) = 0.97
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Percent Within Limits Using
Conformal Index
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Equations
Q(u) =
Q(L) =
USL - x
x - LSL
CI
CI
-
-
1. Determine Random Sample Location Within Lot
2. Make Measurements at Locations or on Material Samples
3. Determine Average of Samples:
4. Determine Standard Deviation of Samples:
Acceptance Plan:Percent Within Limits (PWL) Approach
x = xi
nn
i=1
Sci = (xi – spec requirement)2
n-1ni=1
Acceptance Plan:Percent Within Limits (PWL) Approach
5. Determine Upper Quality Index, Qu:
6. Determine Lower Quality Index, QL:
7. Estimate PU and PL From Table Using Calculated QU and QL
8. Total Percent Within Limits = (PU + PL) - 100
QL = (x - L)
S ci
QU = (U - x)
S ci
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Example Problem
• Percent passing 0.075 sieve– Test 1 : 4.1– Test 2: 4.5– Test 3: 4.8– Test 4: 5.0– Test 5: 5.1
• Specification Target: 5.0 %• Allowable tolerance: See next slide
Construction QC/QA Acceptance 30
Set Spec Limits
• The typical standard deviation from industry is 0.7 %; therefore:– S = 0.7 and n = 5– S(n) = 0.7 / square root (5)– S(n) = 0.7/2.236 = 0.313
• For three standard deviations the spec limits would be + 0.94 %.
• Therefore:– Upper spec limit = 5.94 %– Lower spec limit = 4.06 %
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Compute values
• The average is: – 4.72 %
• Conformal Index for data is:– 0.533
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Compute QU
Q(u) = USL - x Sci
-
Q(u) =
Q(u) = 2.30
5.94 - 4.72 0.53
P(u) = > 1.00
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Compute QL
Q(L) =
Q(L) =
x - LSL
4.72 - 4.06 0.53
s
-
Q(L) = 1.24
P(L) = 0.90
Construction QC/QA Acceptance 34
Questions?