raising the quality bar- everyone wins! · – all the presentation slides – class exercises...
TRANSCRIPT
Quality in the Concrete Paving Process
Introduction Introduction - 1
Raising the Quality Bar- Everyone Wins!
Virginia Concrete Conference March 8, 2013 Richmond, VA
Quality in the Concrete Paving Process
Jim Grove, PE Federal Highway Administration/Global Consulting Inc.
Office of Infrastructure
Quality in the Concrete Paving Process
Introduction - 2
What?
• Quality Assurance – We test and inspect to insure pavement meets
specifications – We have quality procedures to insure long life
pavements – These are not the same!
Quality in the Concrete Paving Process
Introduction - 3
Testing vs. Quality
• Testing does not insure quality • Testing is a tool to achieve quality • Testing and inspection allow us to anticipate
and avoid problems • We use test results to
achieve quality
Quality in the Concrete Paving Process
Introduction - 4
Quality in the Concrete Paving Process Workshops
Upcoming Workshops
Alaska Hawaii Workshops to
date
Quality in the Concrete Paving Process
Introduction - 5
Agenda • Workshop Introduction • Module 1: Quality Assurance Concepts • Module 2: Materials and Characteristics for Quality
Pavement • Module 3: Pre-Paving and Mix Production • Module 4: Paving • Module 5: Utilizing Quality Concepts • Module 6: Quality in Field Practice
What
Why
How
Both contractors and agency personnel!
Quality in the Concrete Paving Process
Introduction - 6
Reference Materials
• Participant Workbook – All the presentation slides – Class exercises
Quality in the Concrete Paving Process
Richmond, Virginia 2013
Quality in the Concrete Paving Process
Introduction - 7
Reference Materials
• Testing Guide – Identified concrete tests
for critical concrete properties
– What to test – Purpose – How to test – What does it mean? – Implication
Quality in the Concrete Paving Process
Introduction - 8
Reference Materials
• Quality Manual – What to inspect – How to inspect – Format of the Workshop – QC Plan – Checklists – Both contractors and
agency
Quality in the Concrete Paving Process
Introduction - 9
Reference Materials • Flash Drive
– National Concrete Pavement Technology Center: Integrated Materials and Construction Practices for Concrete Pavement Manual (IMCP Manual)
– ACPA : Concrete Pavement Field Reference: Pre-Paving
– ACPA : Concrete Pavement Field Reference: Paving – NHI Course 134064: Transportation Construction
Quality Assurance – Example QC Plan – Example spreadsheets for control charts
Quality in the Concrete Paving Process
Introduction - 10
Contractor Benefits • Contractors who consistently meet specifications
have an advantage at the bidding table – Reduce Penalties
• Done right the first time • Reduced Re-Work • QC costs are typically a fraction
of re-work costs
– Increase Incentives • Know you will get full incentive • Use incentive to reduce bid amount
• Allows energy for monitoring the process, not wasting it on fixing problems
Quality in the Concrete Paving Process
Introduction - 11
Agency Benefits
• Agency receives improved quality without additional cost
• Finish project sooner – Frees up personnel sooner – Open to the public sooner
• Avoids time needed to assess re-work and determine penalty
• Creates a better working environment
• Public gets a longer lasting pavement
Quality in the Concrete Paving Process
Introduction - 12
Core Elements of a QA Program
Quality Assurance
Quality Control
Agency Acceptance
Independent Assurance Dispute Resolution
Qualified Labs Qualified Personnel
Quality in the Concrete Paving Process
Introduction - 13
Acceptance Plans that Recognize Inherent Variability
• Based on proven mathematical probability (MIL 414)
• Take into account the sources of inherent variability
• Provide a more realistic assessment of degree of conformance
Quality in the Concrete Paving Process
Introduction - 14
Quality Measurement Tools
• Two principal tools used to measure conformance with requirements: – Inspection
– Testing
Quality in the Concrete Paving Process
Introduction - 15
Inspection Components
• Equipment
• Materials
• Workmanship
• Environmental Conditions
Quality in the Concrete Paving Process
Introduction - 16
Measuring Quality with Testing
• Three criteria must be identified to assess Quality through testing: – Quality Characteristics
– Quality Measures
– Quality Limits
Quality in the Concrete Paving Process
Introduction - 17
Sampling
• “The process of selecting one or more samples from a population (Lot).”
• Key elements of sampling system: – Lots
– Statistical Samples
Minimum of 3 samples
Ideally 8 to 20 random samples
– Sublots
– Samples
Quality in the Concrete Paving Process
Introduction - 18
Random Sampling • Removes bias • All materials have an equal probability of being
sampled • Appropriate for acceptance testing • Appropriate for statistical
process control
Quality in the Concrete Paving Process
Introduction - 19
Material Process Sampling Testing
Composite Variability
Sources of Variability
Quality in the Concrete Paving Process
Introduction - 20
Validity of Sampling Data
• The principles associated with Normal Distribution can be applied to determine the Quality of a Lot of Material, assuming:
1) “Multiple” (n > 3) samples are used 2) All samples are “Randomly” obtained 3) Samples are obtained from the same Lot under “Controlled Conditions”
Quality in the Concrete Paving Process
Introduction - 21 II - 21
Re-Sampling vs. Re-Testing
• Re-sampling – Take a new material sample – Replace the original sample with the new
• Re-testing – Perform another, separate test – Perform the test on the split from the original sample
Quality in the Concrete Paving Process
Introduction - 22
Analysis and Application of QC Test Results
• Control charts – Used to plot and monitor consecutive QC test results
– Results can be tracked against a process target/limits
– Can help to identify whether the process is in control
– May indicate that adjustments process is necessary
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1-1 1-2 2-1 2-2 2-3 3-1 3-2 3-3 4-1 5-1 5-2 6-1 6-2 7-1 7-2
Uni
t Wei
ght,
pcf
Unit Weight Mixture Design Upper Limit Lower Limit
Quality in the Concrete Paving Process
Introduction - 23
Control Charts
• Control charts do not – Eliminate variability
– Tell you where your problem lies
– Tell you how to correct the problem
• Some control charts – Help distinguish between the inherent
chance causes of variability and assignable causes
Quality in the Concrete Paving Process
Introduction - 24
Acceptance Function
• Acceptance is not focused on directing the methods used to achieve conformance
• The primary objectives of agency acceptance are: – Measure the Quality of all materials produced
and placed by the contractor
– Determine the corresponding payment the contractor should receive
Quality in the Concrete Paving Process
Introduction - 25
Acceptance Function
• Quality measurement is achieved through three general acceptance activities: – Monitoring the adequacy of contractor QC activity
– Performing acceptance inspection to identify visually deficient work
– Performing Acceptance sampling and testing for key quality characteristics
• Agency is obtaining information to confirm that all products meet the specified quality level
Quality in the Concrete Paving Process
Introduction Introduction - 26
Module 2: Materials and Characteristics for
Quality Pavement
Quality in the Concrete Paving Process
Introduction - 27
Concrete Materials
• Cements / Supplementary cementitious materials • Aggregates • Water • (Admixtures)
Quality in the Concrete Paving Process
Introduction - 28
How SCM’s Work
Supplemental Cementitious
Material CSH CH +
Secondary Reaction
Water +
Calcium Silicates + Water CSH CH +
Calcium Hydroxide Cement
Fly Ash / Slag Begins after the cement reaction
Calcium Silicate Hydrate
Causes Stuff to Harden =>
Calcium Carbonate
Quality in the Concrete Paving Process
Introduction - 29
Chemical Admixtures • Air entraining admixtures (AEA)
• Water reducers
• Set modifying admixtures
To make good concrete better, not to fix bad concrete!!
Quality in the Concrete Paving Process
Introduction - 30
Strength
• Affects fatigue cycles • Controlled by w/cm
– Other factors are indirect – Strength and durability are not the same
Quality in the Concrete Paving Process
Introduction - 31
Permeability
– Rapid Chloride Permeability Test (Indirectly)
– Wenner Probe/Surface Resistivity Test
(Indirectly)
Rapid Chloride Permeability Test Surface Resistivity Test
• Test (Surrogate tests for durability)
Quality in the Concrete Paving Process
Introduction - 32
Unit Weight
• Test – Unit Weight
• Quality Indicator for: – Uniformity
• Batching tolerances – Air Content
Quality in the Concrete Paving Process
Introduction - 33
Calorimetry
• Test – Calorimetry (heat signature)
• Quality Indicator for: – Cementitious system – Strength development – Time of set – Sawing window – Uniformity
Quality in the Concrete Paving Process
Introduction - 34
Air Content
• Test – Air Content
• Quality Indicator for: – Freeze-thaw damage – Strength
Air 1% Strength 5%
Quality in the Concrete Paving Process
Introduction - 35
Air Void System
• Why? – Water expands when it freezes
• What are we looking for? – Small bubbles close together – Air void system is more important than total air content
Expansion of 9%
Quality in the Concrete Paving Process
Introduction - 36
Quality Control Stage
• Monitor mixture quality during production and react to changes – Gradation – Slump – Unit weight – Air content – Microwave water content – Strength – Permeability
Quality in the Concrete Paving Process
Introduction - 37
Incompatibility
• All materials meet specification, yet the mixture is unsatisfactory – Early stiffening – Air entrainment – Strength development
• Due to chemical reactions between materials • Change mix temperature, SCM dose and/or
admixture type • Refer to page 9 of the “Testing Guide”
Quality in the Concrete Paving Process
Introduction - 38
Volume Shrinkage
Quality in the Concrete Paving Process
Introduction Introduction - 39
Pre-Paving Activities
Quality in the Concrete Paving Process
Introduction - 40
Dowel Basket Placement • Load transfer • Why?
Dowel Basket Placement
Quality in the Concrete Paving Process
Introduction - 41
Paver Preparation • Extrusion process
• Check slab dimensions and cross-slopes
Quality in the Concrete Paving Process
Introduction - 42
Aggregate Stockpile Management • Minimize segregation
– Build long and wide-NOT high! – Build stockpiles in tiers to avoid
segregation
Fines at the top
Coarse at the bottom
Picture courtesy of Martin Marietta Materials
Quality in the Concrete Paving Process
Introduction - 43
Aggregate Stockpile Management • Uniform Moisture
– Stable and well drained foundation underneath stockpiles – Place a separation layer on top of soil – Draw from areas of known moisture content
Quality in the Concrete Paving Process
Introduction - 44
Aggregate Stockpile Management • Mud balls
Quality in the Concrete Paving Process
Introduction - 45
Recommended Practices • Adequate mixing time
– Uniformity – Air entrainment – Strength – Workability
Quality in the Concrete Paving Process
Introduction - 46
Transporting Concrete • Maintain haul route
Quality in the Concrete Paving Process
Introduction Introduction - 47
Paving Activities Refer to the “Field Reference Manual for Quality Concrete
Pavements” for details on steps shown in italics
Quality in the Concrete Paving Process
Introduction Introduction - 48
Spreading Concrete • Continuous supply of concrete to the paver • Consistent head => smoothness
Quality in the Concrete Paving Process
Introduction Introduction - 49
Consolidation • Match vibrator frequency to workability and paver speed • Electronic vibrator monitor
Quality in the Concrete Paving Process
Introduction Introduction - 50
Key Inspection Items • One contactor example • Tape QC Inspection list on the paver
• Stringline – constant • Edge slump – every 50’ • Offset alignment – every 50’ • Slab width – every 50’
Quality in the Concrete Paving Process
Introduction Introduction - 51
Key Inspection Items • Check dowel location
• Real-time • NDT
• Core verification after first day − Depth − Alignment − Position relative to sawn joint
Quality in the Concrete Paving Process
Introduction Introduction - 52
QC Measurements • Verify dowel bar location behind the paver
Quality in the Concrete Paving Process
Introduction - 53
Key Inspection Items • Periodically verify steel location behind the paver
– Cover meter (pachometer) – GPR after hardened – MIT-SCAN-2
Pachometer
GPR
Quality in the Concrete Paving Process
Introduction - 54
Key Inspection Items • MIT-SCAN-2
• Cut the tie wires
Quality in the Concrete Paving Process
Introduction Introduction - 55
Recommended Practices • Identify bumps and dips – overlap straightedge by 1/2 • Correct bumps and dips
Quality in the Concrete Paving Process
Introduction - 56
Texturing • Macro Texture
– Wet weather skid resistance – Reduce hydroplaning
Quality in the Concrete Paving Process
Introduction - 57
Group Activity
Why do we Cure?
Quality in the Concrete Paving Process
Introduction Introduction - 58
Recommended Practices • Adequate number of saws on the project
Quality in the Concrete Paving Process
Introduction Introduction - 59
Module 6: Quality in Field Practice
Quality in the Concrete Paving Process
Introduction - 60
Slump • Measure of consistency • Quick and easy
Quality in the Concrete Paving Process
Introduction - 61
Air Void Analyzer • Air void system • Initially to verify a good air void system • For QC, not for specification compliance • Higher total air => lower spacing factor
0.000
0.004
0.008
0.012
0.016
0.020
3-1 3-2 3-3 4-1 5-1 6-1
Spac
ing
Fact
or, i
n
Spacing Factor, in 0.01 in Limit 0.015 in Limit
5.2% 6.5% 6.0% 6.5% 5.0% 5.3% Total Air
At the plant
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Introduction - 62
Heat Signature • Cementitious system • Strength development
– Time of set – Sawing window
• Incompatibilities • Uniformity
Quality in the Concrete Paving Process
Introduction - 63
Permeability • Surface Resistivity Test
– Easy and quick test
• Rapid Chloride Permeability Test – Takes more time and effort- old stand by
0
5
10
15
20
25
2-1 2-2 2-3 3-1 3-2 4-1 5-1 5-2 6-1 6-2 7-1 7-2
Surf
ace
Resi
stiv
ity, K
Ohm
-cm
Sample ID
56 DaysLow
Moderate
High
Quality in the Concrete Paving Process
Introduction - 64
Heat Signature vs. Surface Resistivity
y = 1351.9e-0.046x
R² = 0.9141
5.0
7.0
9.0
11.0
13.0
15.0
17.0
19.0
21.0
23.0
25.0
90 92 94 96 98 100 102 104 106
56 D
ay S
urfa
ce R
esis
tivity
, Ohm
-cm
Maximum Temperature of the Heat Signature Curve, F
Quality in the Concrete Paving Process
Introduction - 65
HIPERPAV [Example]
• Software tool for assessing cracking risk
Tensile Strength
Critical Tensile Stresses - Top
Critical Tensile Stresses - Bottom
Quality in the Concrete Paving Process
Introduction - 66
@ 9:00 P.M.
HIPERPAV • Software tool for assessing cracking risk
@ 1:00 A.M. @ 5:00 A.M. Placement on the night of 5/21/12
Quality in the Concrete Paving Process
Introduction - 67
HIPERPAV • Software tool for assessing cracking risk
@ 8:00 P.M. @ 12:00 A.M. @ 4:00 A.M. Placement on the night of 5/22/12
Quality in the Concrete Paving Process
Introduction - 68
Maturity • Maturity curve
– Temperature and time factor can be used to determine in-place pavement strength
Opening strength= 550 psi MOR
0
100
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0 500 1000 1500 2000 2500 3000 3500 4000
Flex
ural
Str
engt
h, P
SI
Maturity, °C-Hrs
Maturity Curve - Standard Cured Beams
Specimens Caston 5/16/12
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0 500 1000 1500 2000 2500 3000 3500 4000
Flex
ural
Str
engt
h, P
SI
Maturity, °C-Hrs
Maturity Curve - Standard Cured Beams
Specimens Caston 5/16/12
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Flex
ural
Str
engt
h, P
SI
Maturity, °C-Hrs
Maturity Curve - Standard Cured Beams
Specimens Caston 5/16/12
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100
200
300
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0 500 1000 1500 2000 2500 3000 3500 4000
Flex
ural
Str
engt
h, P
SI
Maturity, °C-Hrs
Maturity Curve - Standard Cured Beams
Specimens Caston 5/16/12
0
100
200
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0 500 1000 1500 2000 2500 3000 3500 4000
Flex
ural
Str
engt
h, P
SI
Maturity, °C-Hrs
Maturity Curve - Standard Cured Beams
Specimens Caston 5/16/12
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100
200
300
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0 500 1000 1500 2000 2500 3000 3500 4000
Flex
ural
Str
engt
h, P
SI
Maturity, °C-Hrs
Maturity Curve - Standard Cured Beams
Specimens Caston 5/16/12
820 C-Hrs
Quality in the Concrete Paving Process
Introduction - 69
Maturity • Maturity curve
– Temperature and time factor can be used to determine in-place pavement strength
Maturity number = 820 ○C-Hrs
Opening strength= 550 psi MOR
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200
300
400
500
600
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1000
0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48
Mat
urity
(°C-
Hrs)
Time(hrs)
Field Maturity (5/18/12)Field Maturity (5/21/12)
22 hrs
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Introduction - 70
MIT-SCAN-T2 • Thickness example
– Design thickness = 11” – Average thickness (T2)= 12.3”
10.010.511.011.512.012.513.013.514.0
294+
05
296+
00
297+
00
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00
301+
00
697+
16
698+
10
700+
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08
706+
00
708+
00
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00
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00
715+
00
T2 P
avem
ent T
hick
ness
, in
Thickness Design Average
Quality in the Concrete Paving Process
Introduction - 71
Air/Unit Weight • Normally they will run parallel
– Unit weight changes if air content changes – Unit weight changes if water (slump) changes
• When they diverge – Change in materials or proportions
5%
6%
7%
8%
9%
10%137
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1-1 2-1 2-2 2-3 3-1 3-2 3-3 3-4
Air C
onte
nt, %
Uni
t Wei
ght,
pcf
Sample ID
Unit WeightAir Content
??
Quality in the Concrete Paving Process
Introduction - 72
Agenda • Workshop Introduction • Module 1: Quality Assurance Concepts • Module 2: Materials and Characteristics for Quality
Pavement • Module 3: Pre-Paving and Mix Production • Module 4: Paving • Module 5: Utilizing Quality Concepts • Module 6: Quality in Field Practice
What
Why
How
Both contractors and agency personnel!
Quality in the Concrete Paving Process
Introduction - 73
Jim Grove Federal Highway Administration/Global Consulting Inc.
Office of Infrastructure
2711 South Loop Drive Suite 4502
Ames, Iowa 50010 Phone: 515-294-5988 Mobile: 515-450-3399