A Risk-Based Framework for Optimizing Inspection Tests of Concrete Pavement Materials
Mamdouh Mohamed, University of KansasShow Abstract
Daniel Tran, University of Kansas
State departments of transportation (DOTs) have been facing a challenge of shrinking budgets and reductions in the size of experienced inspection staff with increased number of construction projects over the last decade. For Portland cement concrete pavement (PCCP) construction projects, a large number of quality assurance (QA) tests typically are necessitated to ensure quality of highway construction is met. Yet relatively little research has focused on prioritizing these tests and frequency of testing. To address this gap, a risk-based approach was developed to refine PCCP material tests. A core list of 10 PCCP material tests was identified through literature and survey. These tests were then evaluated to determine the risk levels and sampling frequency. The risk levels were determined using the four-point scale of both probability and consequence. Based on the risk rating system, four tiers of material tests were proposed. Finally, a case study example was presented to validate the approach. The result showed that there is one test in Tier 1, three tests in Tier 2, five tests in Tier 3, and one test in Tier 4. QA tests with high risk levels require more sampling and testing frequency than those with lower risk levels. This study adds to construction engineering literature by providing with new risk-based guidance on evaluating and determining QA test frequencies for PCCP projects. The findings from this study may help DOTs determine a sample size and prioritize QA tests to save time and cost and improve the safety and quality of PCCP projects.
INSPECTION WORKLOAD REDUCTION APPROACHES TO HIGHWAY CONSTRUCTION PROJECTS
Mamdouh Mohamed, University of KansasShow Abstract
Daniel Tran, University of Kansas
State departments of transportation (DOTs) have been struggled with performing construction inspections with reduced resources of funding and inspection staff. Migration to private sectors and retirement of experienced inspectors have eroded the ranks of qualified professionals. As a result, DOTs are facing an increased challenge to ensure that quality requirements such as safety and service level are met for construction projects. To overcome such challenge, DOTs have applied various workload reduction approaches to offset the shortage of quality assurance (QA) inspection resources in their construction projects. This study evaluates and synthesizes these approaches by conducting a comprehensive literature review and a national survey. The result revealed that most DOTs have a shortage of in-house staff. Six approaches were found to be used by DOTs to reduce inspection workload, including four conventional and two emerging approaches. The conventional approaches involve outsourcing to consultant, reducing the number of inspections and tests, using contractor’s test results for acceptance, and other techniques such as inspecting some work items after installation. The two emerging approaches include prioritizing QA inspections based on material criticality and using new technology and tools for inspection. The study found that emerging approaches potentially increase the value of inspection given the resource constraints. The findings from this study may provide guidance for DOTs to identify different inspection workload reduction approaches to meet their specific needs for construction inspection. DOTs also may benefit from this study by adopting one or more of these approaches when there is a shortage of inspection resources
A Review of the State of the Practice in Pavement Data Quality Management
Bahar Bazargani (email@example.com), SRF Consulting GroupShow Abstract
Omar Smadi, Iowa State University
Pavement management, planning ahead for the maintenance and repair of the roadway, is developing with 2 technology. To maintain a certain level of pavement quality, the Federal Highway Administration (FHWA) 3 has asked state departments of transportation (DOT) to report all the data processes they follow in their 4 pavement management practices in a document called a data quality management plan (DQMP). A DQMP 5 must contain information regarding the following sections: (i) data collection equipment calibration, (ii) 6 certification, (iii) data quality control measures, (iv) data sampling, review and checking processes, and (v) 7 error resolution procedures and acceptance. This paper is a review of the state of practice in pavement data 8 quality management. A survey was sent out to DOT pavement management engineers requesting 9 information about their pavement data collection procedures, quality management (QM), and quality 10 assurance (QA) processes. From the 31 states that responded, 28 DQPMs were collected and studied. The 11 best practices based on coverage of the FHWA requirements and how the information can contribute to 12 pavement QM are identified, and the needs to improve overall QM procedures and ways to enhance DQMPs 13 are explained. The majority of the states addressed quality control (QC) and acceptance in their DQMP. 14 Few states discussed QA and sampling. 75% of the reports discuss acceptance procedures but do not explain 15 the errors underlying the acceptance criteria. Lastly, most of the practices that are being done are by 16 experience, and therefore adding theoretical and statistical background to the DQMP can improve the 17 quality of pavement condition data.
HMA Quality Management Program in Illinois: Statistical Assessment of Pay for Performance versus Quality Control for Performance.
Jose Julian Rivera-Perez (firstname.lastname@example.org), University of Illinois, Urbana-ChampaignShow Abstract
Seunggu Kang, Merrimack College
Watheq Sayeh, University of Illinois, Urbana-Champaign
Javier García Mainieri, University of Illinois, Urbana-Champaign
Imad Al-Qadi, University of Illinois, Urbana-Champaign
Hasan Ozer, Arizona State University
The Illinois Department of Transportation developed two quality assurance specifications for hot-mix asphalt: quality control for performance (QCP) and pay for performance (PFP). Both specifications feature pay disincentives associated with air voids (AV), voids in mineral aggregate (VMA), and in-place density limits, while PFP projects also feature incentives. Inherent variability exists in test results, however. During 2015 and 2016, approximately 44% and 55% of QCP and PFP tonnages, respectively, received disincentives, averaging $20,000 per project, based on 710 projects analyzed from six districts in Illinois. After a decade of implementation, there was a need to understand contractors’ pay distribution and test results to identify possible issues that may hinder contractors achieving full pay. Test results obtained for the 2015–2017 construction seasons, along with QCP and PFP data, were statistically analyzed. The percentage of projects receiving a disincentive was greater under QCP specifications than those under PFP. However, the monetary amount of the disincentives was greater in PFP. More than 80% of the test results from districts and contractors were not significantly different. Density was the major factor driving contractor disincentives in both specifications, followed by AV. From the quality control tests, the bulk specific gravity test was the most variable, which was the main cause of differences between both laboratories. Although testing issues need to be addressed by districts and contractors, disincentives appear to be mainly associated with mix production and/or construction. Recommendations have been made to improve the projects receiving incentives.
Non-Destructive Testing for Strength Gain Monitoring of Concrete in Quality Assurance
Setare G Saremi (email@example.com), University of MarylandShow Abstract
Dimitrios Goulias, University of Maryland, College Park
Non-destructive tests (NDTs) provide the ability to test a large portion of cast-in-place concrete, which may be particularly beneficial since they are not involved with significant increase in quality assurance (QA) cost. Furthermore, NDTs can provide real time monitoring of construction quality. In regards to concrete strength, predicting the time for formwork removal is possible through maturity predictive models. NDTs can also provide early warnings in meeting strength requirements at early ages as well as long term strength. The objective of this study was to assess whether easy to use, fast, and inexpensive NDTs can be used for strength gain monitoring in QA and assess whether their accuracy and repeatability is acceptable enough for their adoption in an NDT-based QA plan. Therefore, a variety of well accepted non-destructive methods were selected to monitor strength gain of concrete during the first 28 days. Infrared thermography (IRT), ultrasonic pulse velocity (UPV), resonant test gauge (RTG), and rebound hammer were used in combination with wireless temperature sensors (iButtons) for relating concrete heat of hydration to concrete strength and assessing testing variability and accuracy. The results indicated that UPV and RTG provided good relationship with strength predictions and acceptable repeatability and accuracy. The approach presented herein can be used to assess the potential adoption of other NDTs in a QA plan and expand the findings of this study with other concrete mixtures.
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