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SPR 734

Premature Asphalt Concrete Pavement Cracking
 
Project Coordinator: Norris Shippen
Research Agency:  Iowa State University
Principal Investigator:  Chris Williams
Start Date for ODOT: June 28, 2011
Completion Date for ODOT:        November 30, 2012
 
OBJECTIVES: 
The objectives of the research are to determine the causes of early cracking on the state highway system. The results of the study will be used to modify our pavement design process including modifications to the Pavement Design Guide and Mix Design Guidelines.
 
OVERVIEW:  
Recently ODOT has constructed pavements that have experienced premature cracking within three years of construction. Early cracking allows moisture to penetrate the pavement structure reducing the section’s design life and significantly increasing the life cycle cost. Also within the last several years, design and material changes occurred that may or may not have contributed to the pavement distress. The changes include an increase in the quantity of recycled asphalt pavement (RAP) allowed in the wearing surface; the use of binder modifications including acid and polymers; and a shift in mix gyration levels. Construction factors like properties of the produced mix (volumetrics) and placement also play a part of the pavement performance.
 
National investigations into cracking have identified areas where the cracking is top down versus bottom up. While both are serious, bottom up cracking typically indicates the pavement structure was under designed indicating a need to change structural design practices. Top down cracking, however, may indicate that the material selection process can be fine-tuned. The only means to differentiate between top down versus bottom up cracking is through coring.
 
The literature has identified several possible causes for early distresses.  For top down cracking, high surface horizontal tensile stress, age hardening and low stiffness upper layer caused by high surface temperatures have been identified as possible causes.  Also for thicker pavements , greater than 6.5 inches, top down cracking can be the dominant form of cracking (1).  For Oregon however, it is unknown which mechanism(s) have contributed to the early cracking distress.


 
PROPOSED ACTIVITIES:
Task 1: Literature Review and State Survey: There is a fair amount of information available that details other early cracking investigations.  A survey would also be developed to collect specific information from transportation agencies about their experience with early cracking.
 
Task 2: Identification of pavements exhibiting early cracking: Use information from the ODOT pavement management databases to identify top performers and early failures. What are the commonalities for good pavements versus poor pavements?  Investigation will include reviewing pavement designs (inlay, inlay/overlay, and overlay), mix designs and construction history.
 
Task 3: Field work and laboratory evaluation: After reviewing the data collected in Task 2, formulate a hypothesis as to the nature of the cracking and develop a field work plan to perform sampling and testing of in-service pavements. It is anticipated that six to ten projects will be investigated. Sampling and testing may include deflection testing, coring and lab testing. The deflection testing will provide an estimate of the overall strength of the pavement section; the coring will provide a visual indication of the quality of the pavement and the location of the cracking (top down, bottom up); and the lab testing will provide an assessment of the in place properties of the mix and oil.
 
Task 4: Analysis and documentation: Compile the results of the information from both the construction history of good and poor pavement performers along with results from the field and lab evaluations to determine the cause(s) of early cracking. Following the analysis, provide a final report documenting the findings and recommend changes to our design process.
 
Task 5: Implementation: The task would provide guidance as to what changes are needed in our pavement design and/or mix design process and/or standard specifications to insure we are getting long lasting pavements. The recommendations would be incorporated into our Pavement Design Guide and/or Mix Design Guidelines and/or specifications.


 
PREMATURE ASPHALT CONCRETE PAVEMENT CRACKING WORK PLAN 
 
 
Quarterly Reports:



 FY 12
 FY 13
FY 14
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qtr. 2
qtr. 3
qtr. 4

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SPR 736

A Corrosion Monitoring System for Existing Reinforced Concrete Structures
 
Project Coordinator: Steve Soltesz
Research Agency:  Western Transportation Institute
Principal Investigator:  Xianming Shi
Start Date for ODOT: March 2011
Completion Date for ODOT:        June 2013
 
OBJECTIVES: 
The goal of this research is to provide a reliable, cost-effective corrosion monitoring system for existing ODOT reinforced concrete structures.
 
OVERVIEW: 
Reinforcement corrosion is a leading cause of premature failure of reinforced concrete and a major concern for concrete structural durability. Concern is greatest in coastal and northern states where these structures are exposed to marine environments or deicing salts respectively, such as in the State of Oregon.
 
ODOT conducts labor-intensive corrosion surveys of its coastal bridges to identify structures that are expected to require future corrosion mitigation. Because of the time and cost required to conduct these surveys, the corrosion information for coastal bridges is not as complete as desired.  A method of obtaining frequent corrosion data would provide better condition assessment at much lower cost than the periodic hands-on surveys.  In addition, a system that measures real-time corrosion behavior could potentially be used with impressed current cathodic protection (ICCP) to adjust the protective current in a way that maximizes anode life.  Unfortunately, available corrosion sensors are not adequate because of operational and data interpretation deficiencies.
 

 
PROPOSED ACTIVITIES:
Task 1:  Optimize an Integrated Corrosion Sensor  This task will optimize a prototype embeddable corrosion sensor developed by Southwest Research Institute (SwRI).  The SwRI sensor is a Φ35mm ´ 20 mm cylindrical device that measures chloride concentration, pH, corrosion rate, and concrete conductivity. The sensor can be easily embedded into an existing concrete structure to monitor key parameters of interest. Particular effort will be focused on two aspects of the sensor: 1) optimizing the reliability, durability, and sensitivity of each sensing component to achieve good performance for at least ten years and 2) devising an embedment method that allows the sensor to evaluate an existing structure with minimum disruptive effect. The research team has conceptual ideas on how to address these issues and will conduct the sensor optimization using bench-scale concrete slabs.  In addition, the team plans to add temperature and moisture sensing elements to the sensor package.
Task 2:  Build Data Communication and Collection System  This task will integrate the sensing components with a low-powered wireless system for data acquisition, initial processing, and transmission.  The platform for data handling and communication (motes) was developed at UC Berkeley and implemented by SwRI in other sensor systems.
Task 3:  Develop Methodology for Corrosion Diagnosis and Prognosis Western Transportation Institute (WTI)). Data interpretation (e.g. statistical process control methods and/or artificial neural networks) coupled with sensor signals is powerful in recognizing corrosion patterns as they unfold in real time. This task will develop the method to interrogate the collected sensor data (after normalization and cleansing) to assess the corrosion risk and status of the rebar via pattern recognition and to predict future deterioration states of the concrete and rebar. The actionable information will be presented through an intuitive interface to facilitate asset management and decision-making.
Task 4: Test Pilot-Scale System  This task will test and validate the performance of the overall corrosion monitoring system (including both hardware and software). The sensors will be deployed in a reinforced concrete bridge column to simulate an aging ODOT concrete structure. The column will be seated in a chamber with simulated marine environment, including underwater, splash and atmosphere exposure zones. Concurrently, a sensor system will be deployed on an ODOT bridge to test the system under actual conditions. Tests will also be performed to determine whether impressed current cathodic protection (ICCP) zones interfere with the performance of the sensor.  If the sensor is compatible with ICCP, recommendations will be made on how the sensor can be used to control ICCP systems.
Task 5: Final Report The report will incorporate all aspects of the research including a cost estimate and deployment recommendations for ODOT. 
 
A CORROSION MONITORING SYSTEM FOR EXISTING REINFORCED CONCRETE STRUCTURES WORK PLAN


 
Quarterly Reports:



 FY 11
 FY 12
FY 13 FY 14 FY 15
 
qtr. 1 qtr. 1 qtr. 1​
 
qtr. 2 qtr. 2
 
qtr. 3 qtr. 3
qtr. 4 qtr. 4

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SPR 741

Bridge Seismic Retrofit Measures Considering Subduction Earthquakes
 

Project Coordinator: Joe Li
Research Agency:  Portland State University
Principal Investigator:  Peter Dusicka
Start Date for ODOT: November 2011
Completion Date for ODOT:        September 2014
 
OBJECTIVES: 
The goal of the research is for ODOT to have validated effective seismic retrofit measures that
consider the uniqueness of Oregon bridges and the effects of subduction earthquakes.
 
OVERVIEW:  


The majority of Oregon’s bridges were built prior to the current understanding of the regional
seismic risk and did not incorporate design details to withstand a significant earthquake. A
seismic hazard assessment model for Oregon highway routes has shown serious vulnerability to
the transportation network. Seismic retrofits in the state have been limited to Phase 1 retrofits
that provide restrainers for keeping the superstructure in place on the bents. Such retrofit
measures are effective for their intended purpose, but shift the displacement demands onto the
supporting substructure. Effective retrofit measures for the substructure have been developed
based on research for California bridges and seismic events. However, bridges in Oregon were
built differently from those in California, and Oregon is likely to experience a subduction
earthquake whereas earthquakes in California are crustal earthquakes.
The M8.8 subduction earthquake in Chile in 2010 highlighted the differences between a
subduction earthquake and a crustal earthquake. The duration of a subduction earthquake is
longer. Subduction earthquakes may entail significant aftershocks for months. Finally, the
frequency content of the shaking that affects the response of structures can span a wider range
than crustal earthquakes.
The effectiveness of conventional retrofit measures applied to Oregon bridges is uncertain due to
the differences in bridge construction, the underlying assumptions for retrofit design and
Oregon’s situation. Similarly, fragility, which relates the probability of damage to shaking
intensity, is also uncertain. Current research at PSU is investigating the seismic performance of
a representative column and of a single retrofit measure for a crustal earthquake. Results for
additional retrofit designs exposed to subduction earthquakes are needed in order to achieve
accurate output from transportation network models and to have reliable retrofit designs.
 
PROPOSED ACTIVITIES:
Task 1: Analyze records from subduction earthquakes
Task 2: Identify seismic retrofit for bridge bent
Task 3: Validate the effectiveness of the retrofit measures
Task 4: Calibrate numerical model of bridge bent retrofit
Task 5: Develop seismic fragility functions
Task 6: Final Report and Design Recommendations
 
BRIDGE SEISMIC RETROFIT MEASURES CONSIDERING SUBDUCTION EARTHQUAKES WORK PLAN


 
Quarterly Reports:




 FY 12
 FY 13
FY 14 FY 15
 
​qtr. 1 qtr.1​
qtr. 2 qtr. 2​
qtr. 3 qtr. 3
 qtr. 4 
qtr. 4

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