midwest geotechnical conference indianapolis, indiana september 22, 2015 bob arndorfer
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WisDOT Base Aggregate Density Program
Midwest Geotechnical ConferenceIndianapolis, IndianaSeptember 22, 2015
Bob Arndorfer
Historical Practice Research Study/Findings Goals/Benefits Development and Highlights of New
Specification Pilot Projects Issues/Modifications Necessary Moving Forward
WisDOT Base Density Outline
2
Where we were 3 years ago Observational Method
Compact “until there is no appreciable displacement either laterally or longitudinally, under the compaction equipment.”
Somewhat Vague Have Been Attempts to Reduce Subjectivity – Limited Success
History of WisDOT Base Density
3
Subjective – No Consistent Method of Acceptance
No Documentation During Construction Non-uniform Compaction Results Issues Raised by Paving Contractors Other States Using More Advanced Means
Issues With Old Method
4
Department Goal - Move to Performance Specs For Material Acceptance Qual Mgmt Program (QMP) - Contractor tests/monitorReduces Departmental oversight and staff timeGive contractor more control of their operations
Ultimate Goal: Increase Pvmt. Performance
Based on all this – Department Decided toHave Some Research Done on This Topic
Issues Cont’d.
5
Many National Studies Using Different DevicesDynamic Cone Penetrometer (DCP)Lightweight Deflectometer (LWD) Intelligent CompactionGeogaugeNuclear GaugeSand ConeOther
Other Base Density Methods
6
Investigate the Effectiveness of Our Current Methods, Survey Other States, Layout Future
Titled: ‘Feasibility Analysis of Base Compaction Specification’
Completed in 2012 by University of Wisconsin- Milwaukee (PI was Professor Hani Titi)
Investigated 11 Existing, and 10 New, HMA Pavement Projects
Look at Current, and Long-term, Base Performance
WisDOT Research Study
7
Projects Located in Various Geographic and Geologic Regions of the State
ME Sensitivity Analysis Using DARWin-ME Investigate Density-based and Modulus-based
Methods Look at Cost Implications of Differing
Compaction Methods
Research Study – Cont’d.
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Investigate Project Material Records Investigative Methods on Existing Projects
FWDVisual Pavement Distress Surveys
Investigative Methods on Current ProjectsLightweight DeflectometerDynamic Cone PenetrometerSand ConeGeogaugeLab Tests including Resilient Modulus
Research Study – Methods
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Out of 49 States and 13 Canadian Ministries, Only 4 Use Subjective Observation Methods for Acceptance – WI Was One of Four
Over 90% of the 63 Contacted Highway Agencies Used Density-Based Methods for Quality Control of Aggregate Bases
Major Findings of Research
10
71% of Highway Agencies Follow ASTM or AASHTO Test Methods
63% Use Nuclear Density Test Measurements 44% Use Standard Proctor for Max Density -
Target Density: 95-100% 27% Use Modified Proctor for Max Density -
Target Density: 90-100%
Major Findings – Cont’d.
11
High Variability of WI Bases Being PlacedField DensityMoisture
HMA Pavement Performance Was Related to Spatial Variability and Non-uniform Density of Base Course
Well Performing HMA Pavements Exhibited Low Levels of Spatial Variability and Good Uniformity in Aggregate Base Courses
Major Findings – Cont’d.
12
The Uniformity of Base Density Appears to be More Critical Than Level of Compaction
Mechanistic-Empirical (ME) Sensitivity Analysis Showed Reduced Life (Increased distress levels) in Pavements With Lower Base Modulii
Base Density Work on 63% of Projects Had No Significant Impact on Project Schedules
53% of Responding Agencies Reported Density Implementation Has No Cost Impacts on Projects
.
Major Findings – Cont’d.
13
42% of Highway Agencies are Looking for New Methodologies to Replace/Complement Their Current Density-Based Specifications
Recommend Quantitative Method of Acceptance Based on Testing
Suggest Investigating Continuous Compaction Control Techniques
Recommend Transitioning to Modulus-based Testing (More research needed to fully implement this.)
Major Findings – Cont’d.
14
Better Bases Facilitate Better HMA Compaction, Resulting in Longer Pavement Life
Measurements Will Increase Consistency of Base Placement Operations and Results
Measurement Will Provide Consistent/Defined Method of Base Acceptance – Not Subjective
Reduce Long-term HMA Pavement Maintenance Costs
Benefits of Base Course Density
15
Reduce Contractor Risk at Time of Bidding and Provide More Equity
Provide Project Documentation of Compactive Levels Achieved
Any Construction Cost Increases Will Still Result in Reduced LCCA Costs
Move WisDOT/Contractor to QMP – Allow Contractor More Control of Their Operations
Transition From Method Spec. to Performance Specification
Benefits Cont’d.
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Based on Study Results – Need New Spec Aggregate Responsibility at WisDOT - ?? WisDOT and Industry Meetings Application Issues to Address
What Types of ProjectsDefine Size of ProjectsWhere Used on Projects
Base Compaction Methods Already Being Used for WisDOT Airport Construction
WisDOT Moves to Develop Spec.
17
Developed Two Specifications/Test MethodsMilled/Pulverized and OverlayBase Aggregate – Different testing based on
percentage of RAP/RCA (Cut-off at 20% RAP/RCA) Contractor to Provide QMP Plan Required Certified Testers QC and QV Requirements Set Dispute Resolution – Third-party Lab (Vague) How to Address Failures – Contractor to Take
Corrective Actions Until Spec is Met
Highlights of Specification
18
Target Density Limit: 95% T-180 Modified Proctor
Additional Proctor if Gradation Varies ≥ 10% on Any One Sieve
Departmental QV Testing at Frequency of 30% of Contractor QC Testing
Payment Based on Ton or SY Basis
Highlights of Specification – Cont’d.
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Base Aggregate Density Testing Frequency – Every 1000 tonsGradation and Proctor – Every 3000 tonsPayment based on Tons
Mill/Pulverize and OverlayDensity Testing Frequency – Every 3000 SYGradation – Every 9000 SYAdditional Proctor if AC content changes by ≥ 1.5%
by visual observationPayment based on SY
Highlights of Specification – Cont’d.
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WisDOT Generally Works Closely With Industry When Developing Specifications
Different PerceptionsPaving industries in favor of itGrading industry less enthusedAggregate producers opposedWI Transportation Builders Association has concerns
FHWA – Supports Movement to Density Department – Favors Measurement
Industry Reactions
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Difficult to Bid - Unknowns Increased Contractor Workload Perceived Increased Contractor Risk Potential For Project Delays if Issues May Require More Compactive Effort by
Contractor Subgrade (Lower Layers) May Not Have
Required Density
Industry Concerns
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Multiple Sources May be Used - Complications Frequency of Testing – How Much? Consider a Density Incentive? Concerns Over Failed Tests and Remediation Potential Project Delays Due to Required
Testing Concern Over Timing of Base Acceptance –
(Delays in acceptance or Changes due to environmental conditions.)
Industry Concerns – Cont’d.
23
HMA Projects Only – Pvmt. Design Process Travel Lanes and Shoulders Only Pay Quantity Based on Total Material (Ton/SY) Include Payment for Compaction Water Base Aggregate 1¼”
Quantity ≥ 30,000 tonsSubgrade Improvement or QMP Subgrade, or Both
Mill/Pulverize and RelayQuantity ≥ 40,000 SY
Project Application Guidelines
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Final Specification Language Developed Various Geographic and Geologic Areas Different Contractors Density Results Used In One of Two Ways
Project ControlFor Information Only
Incorporate Into Pilot Projects - 2013
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Pilot Specification Used on 11 Projects8 Base Aggregate3 Mill/Pulverize and Relay
Generally Went Well, Some Issues Meeting Density Requirements
At End of Construction Season - Department Met With Industry to Discuss Improvements and Implement Revisions
2013 Pilot Projects
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2013 Project Results
2013 Pilot Project Results
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0 2 4 6 8 10 12 14 16 18 2080
85
90
95
100
105
110
Percent Moisture
Perc
ent M
axim
um D
ensi
ty
95% Target
95% of T180 Difficult to Consistently Achieve Issues With Density Measurements When
RAP/RCA >20% More Definition Needed on Corrective Actions
and Acceptance Methods for Material Not Meeting Density
Findings of 2013 Projects Used to Modify Spec for 2014 Pilot Projects
Findings From 2013 Pilots
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Pilot Specification Used on 9 Projects 8 Projects Base Aggregate, 1 Project Mill 576k tons Base Agg, 41k SY Mill/Relayed HMA Revised Specifications
Base - Require 93% T180Base - Testing frequency increased to 1500 tonsBase - In addition to dry density, can determine target
density by wet density or control strip method (>20%)Mill/Overlay – Only use control strip for target densityCorrective Actions Clarified
2014 Pilot Projects
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2014 Pilot Project Results
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0 2 4 6 8 10 12 1489
91
93
95
97
99
101
103
105Density Results
Target Percent Max. Density (93%)
Linear (Target Percent Max. Density (93%) )
Percent Moisture
Perc
ent M
axim
um D
ensi
ty Pass Percentages
95% Max Density: 50%94% Max Density: 72%93% Max Density: 97%
Variation of QC and QV Proctor Values Issues With Proctor Test Requirement When
Gradation Changes by ≥ 10% on Any Sieve Desire to Use Family of Curves Timing of Density Testing and Acceptance Need For Pre-placement Meeting Need to Establish Dry-back Moisture Test
Frequency
Concerns From 2014 Pilots
31
Use QC Proctor Value for All Testing Once Verified by QV Tests (Require ≤3 pcf difference)
New Proctor Necessary When Moving Average of Four Gradation Tests Differs by ≥10% on Any Sieve
QC Can Use Family of Proctor Curves Dry-back Moisture Content Required Every
9000 tons Base
Revisions Based on 2014 Results
32
Contractor to Provide Description of Placement Methods, Staging, Equipment, Etc. in QMP
Require Pre-placement Meeting Clarification on Retesting and Documentation
of Corrected Lots
2014 Revisions – Cont’d.
33
Will be Standard Special Provision for 2016 Construction Season
Apply to all HMA Projects That Meet Criteria Monitor to See if Additional Updates Necessary Incorporate Into PCC Pavement ? Lead to Water Bid Item on All Base Projects ? Contractors Not Complaining Much - Improving Contractors Realizing Importance of
Water for Compaction
Future Directions
34
Base Agg. Research Report Can Be Found At: http://wisdotresearch.wi.gov/whrp/flexible-pavements
Questions?
Questions
35
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