A Users Guide to Performance Engineered Mixtures

Performance Engineered Mixtures is an initiative, spearheaded by the Federal Highway Administration and the National Concrete Pavement Technology Center, in cooperation with state Departments of Transportation and the concrete paving industry, to develop a comprehensive approach to modernizing the way concrete is specified, tested, and accepted. It focusses on three components: testing of six critical concrete properties, a robust approach to quality control, and the replacement of prescriptive specifications. Many new tests have been recently developed that provide the ability to test concrete properties more easily and quicker than in the past. This paper provides background of how this initiative began. It elaborates on each of the six properties of concrete that are the focus of PEM. The new tests that are integral to the PEM process are described. The effects PEM will have on the acceptance process and the quality control responsibilities are outlined. Finally, tables are included which list the properties and the tests that are associated with each property, as well as how each is applied to each step of the paving process.

Implementation of Visualization and Modeling Technologies for Transportation Construction

State departments of transportation (DOTs) increasingly use visualization and modeling technologies for delivering transportation projects across the United States. Advanced and innovative technologies have the ability to improve various construction processes and tasks while making the construction process more efficient and productive. Visualization and modeling technologies, which include building information modeling for infrastructure, light detection and ranging, virtual reality, and augmented reality, are becoming more commonplace in transportation construction. Yet, the use of these technologies varies among state DOTs. The intent of this study is to investigate the use of visualization and modeling technologies for transportation construction. This study employed a triangulation research methodology including an extensive literature review, survey questionnaire of DOTs, and seven case studies. Results of the study show that 92% of state DOTs use visualization and modeling technologies for construction. Then, 81% of DOTs use visualization and modeling technologies for constructability reviews, 38% use them for documentation of as-builts and simulating bridge and structure construction, and 35% use them for quality management, inspections, and monitoring progress of work. The main barriers to using visualization and modeling technologies include legal concerns with using digital models as contract documents, incompatibilities in software and hardware between the DOTs and contracted parties, and the appropriate knowledge, skills, and abilities required to use visualization and modeling technologies for construction. The findings from this study provides valuable information for state DOTs to approach their implementation and use of visualization and modeling technologies for transportation construction delivery.

Benefits and Challenges Associated with the Implementation of Lean in Transportation Agencies

The highway construction industry constantly looks to increase productivity while public transportation agencies face challenges of shrinking budgets and staff numbers, even as the work continues to increase in size and demand. As a paradigm to maximize value and minimize waste with the resources available, Lean offers promise to enhance productivity, quality, and service. This study investigates the implementation of Lean by evaluating Lean conditions, practices, benefits, and challenges as expressed by U.S. and UK public transportation highway agencies as well as comparing the implementation of Lean between these agencies. Using a comprehensive literature review and formal interviews with six state departments of transportation along with Highways England from the UK, the findings show that Lean is intended to make process improvements to boost products and services to consumers. By creating a culture of continuous improvement, transportation agencies can improve their processes and increase their efficiencies and performance. Conversely, transportation agencies struggle to educate their employees and stakeholders in their understanding and practices of Lean, which causes confusion and ineffectiveness. Comparing the U.S. and UK transportation agencies, the approach to Lean implementation differs from a top-down approach for U.S. agencies to a bottom-up approach for Highways England. Furthermore, Highways England has an established tool for measuring Lean while development of quantifiable Lean measures is in its infancy in U.S. agencies. Overall, while the sample is limited, this exploratory study provides information for transportation agencies to use in consideration of implementing Lean.

Bridge-Level Optimization Module for Planning and Programming

The paper briefly introduces an element-based multi-objective optimization (EB-MOO) methodology to support state departments of transportation with their decision-making process, asset management, and performance-based transportation planning and programming. The methodology focuses on the bridge asset class and consists of five modules: (i) data processing, (ii) improvement, (iii) element-level optimization (ELO), (iv) bridge-level optimization (BLO), and (v) network-level optimization (NLO) modules. These five modules jointly produce short- and long-term intervention strategies detailed at the bridge element level for planning and programming. The paper focuses on the BLO module, specifically: the basic framework of underlying processes and concepts, the optimization problem types and mathematical formulations, and the heuristic algorithm to solve the BLO problems. A prototyping tool is developed to implement these five modules of the EB-MOO methodology, test concepts, prove effectiveness, and demonstrate potential benefits. The paper also includes an illustrative example using the prototyping tool. The example consists of the BLO problems under different budget and/or performance scenarios. The implementation proves the module’s capability in producing a diverse set of Pareto optimal or near-optimal solutions, recommending set of element intervention actions and timings, predicting performance, and determining budget requirements for the entire program period. The BLO results associated with the recommended solutions serve as the fundamental inputs for the NLO module. Nevertheless, the BLO module can be used independently, providing a systematic process for the development of bridge improvement/preservation programs detailed at the element level.

Development, Crash Testing, and Evaluation of Steel-Post Trailing-End Guardrail Anchorage System

Trailing-end guardrail anchorage systems are widely used by most state departments of transportation (DOTs) and generally consist of simple adaptations of crashworthy end terminals. The safety performance and structural capacity of these trailing-end anchorage systems, when reverse-direction impacts occur near the end, is imperative in crashworthiness of guardrail systems. In 2013, a non-proprietary trailing-end anchorage system with a modified breakaway cable terminal (BCT) was developed by the Midwest Roadside Safety Facility (MwRSF) for the Midwest Guardrail System (MGS). Although this trailing-end guardrail anchorage system adequately met the Manual for Assessing Safety Hardware (MASH) TL-3 safety requirements, the use of two breakaway wood posts was deemed by some users to have several drawbacks. Thus, there was a critical need to develop a non-wood option to anchor the downstream end of the W-beam guardrail system, which led to the need to develop a steel-post trailing-end guardrail anchorage system for use with the MGS. Following the design and component testing of such a system, two full-scale crash tests were performed according to the MASH 2016 test designation nos. 3-37a and 3-37b. In the first test, a 2270P pickup truck struck the guardrail system and was adequately contained and redirected. In the second test, an 1100C small car struck the barrier and safely gated through the barrier. Both tests were deemed acceptable according to TL-3 safety criteria in MASH 2016. Recommendations are provided for the installation of a steel-post trailing-end guardrail anchorage system when used in combination with MGS.

Achieving Asphalt Pavement Density with Minimal Mat Defects

It is well established that in-place density significantly influences asphalt pavement performance and service life. This paper discusses solutions to challenges that agencies and contractors often face when trying to achieve density requirements, or increase density, while eliminating compaction-related mat defects during the construction process. The basics of the asphalt pavement compaction processes, equipment, operations, and asphalt mixture densification are first presented, followed by information collected on a series of FHWA sponsored departments of transportation (DOTs) density demonstration projects. The authors then summarize the root causes associated with challenges in obtaining the desired density without compaction-related mat defects in a series of categories based on the DOT demonstration projects and experience assisting contractors with obtaining density on hundreds of projects. Examples are described for each category along with potential opportunities for improvements to overcome them. The demonstration projects illustrated that it is possible to make improvements when agencies and contractors embrace the idea of increasing density and reducing mat defects.

Cable Median Barrier Effect on Commercial Vehicle Crossover Crashes

In the United States (U.S.) the annual number of commercial motor vehicle (CMV) crashes has been on an upward trajectory since 2009. In 2016, CMV crashes accounted for 11.8% of all fatal crashes in the U.S., and in Kentucky, between 2009 and 2016, the number of CMV crashes rose 27%. Of particular concern to state departments of transportation have been crossover crashes involving CMVs. These occur when a vehicle leaves its intended path and veers into the path of oncoming traffic, typically resulting in head-on or sideswipe opposite direction collisions. While some researchers have found that installing cable median barriers can mitigate crossover crashes involving CMVs, no definitive conclusions have been reached. To move toward a resolution of this question, this study leveraged analysis by a panel of experts and the development of safety performance functions and crash modification factors to gauge how cable median barriers can influence the number and severity of crossover CMV crashes on Kentucky interstate routes. Expert panelists contended that cable median barriers will improve safety, a conclusion substantiated by statistical modeling. Despite the study’s limited scope, it appears that installing cable median barriers can prevent or mitigate CMV crashes.

Review of Post-Fire Inspection Procedures for Concrete Tunnels

It is well known that concrete structures can lose strength and long-term durability after a fire. The literature on the remaining capacity of tunnel structures after fire is quite scattered, however, and few published post-fire inspection guides exist. This paper reviews the available literature on the post-fire inspection and evaluation of concrete tunnels. The effects of fire on concrete and steel are discussed, including loss of strength, thermal spalling of concrete, and loss of strength in the bond between concrete and steel. In addition, studies on the residual strength of concrete members are presented. Available post-fire inspection strategies and methods are also discussed. Finally, the results of a survey of post-fire tunnel inspection practices at state Departments of Transportation and transit organizations across the United States are presented. Several models available in both structural building codes and experimental studies allow for the estimation of residual concrete compressive and steel tensile strength after heating and cooling from a given temperature. Furthermore, a variety of post-fire assessment methods are available, which include methods to assess the general post-fire condition of concrete tunnels, as well as methods to more directly assess the residual condition of concrete. Lastly, the review of literature and the survey of United States transit organizations revealed a lack of existing post-fire inspection procedures for concrete tunnels, and a need for further research on the subject.

Determination of Sample Size and Influencing Factors to Characterize Faulting in Jointed Concrete Pavements

The objective of this study is to evaluate the field variability of jointed concrete pavement (JCP) faulting and its effects on pavement performance. The standard deviation of faulting along both the longitudinal and transverse directions are calculated. Based on these, the overall variability is determined, and the required sample sizes needed for a given precision at a certain confidence level are calculated and presented. This calculation is very important as state departments of transportation are required to report faulting every 0.1 mi to the Federal Highway Administration as required by the 2015 FAST Act. On average, twice the number of measurements are needed on jointed reinforced concrete pavements (JRCP) to achieve the same confidence and precision as on jointed plain concrete pavements (JPCP). For example, a sample size of 13 is needed to achieve a 95% confidence interval with a precision of 1.0 mm for average faulting of JPCP, while 26 measurements are required for JRCP ones. Average faulting was found to correlate with several climatic, structural, and traffic variables, while no significant difference was found between edge and outer wheelpath measurements. The application of Portland cement concrete overlay and the use of dowel bars (rather than aggregate interlock) are found to significantly reduce faulting. Older sections located on higher functional classes, and in regions of high precipitation or where the daily temperature change is larger, tend to have higher faulting, and might require larger samples sizes as compared with the rest when faulting surveys are to be conducted.

Time Delay Effects on Compactability of Soil-Cement Materials during Proctor Testing

The Proctor test method, as specified in AASHTO T134 and ASTM D558, continues to play a vital role in design and construction quality control for soil-cement materials. However, neither test method establishes a methodology or standardized protocols to characterize the effects of time delay between cement addition and compaction, also known as compaction delay. Compaction delay has been well documented to have a notably negative effect on compactability, compressive strength, and overall performance of soil-cement materials, but specification tools to address this behavior are not prevalent. This paper aims to demonstrate the extent of compaction delay effects on several soil-cement mixtures used in Mississippi and to present recommended new test method protocols for AASHTO T134 to characterize compaction delay effects. Data presented showed that not all soil-cement mixtures are sensitive to compaction delay, but some mixtures can be very sensitive and lead to a meaningful decrease in specimen dry density. Recommended test method protocols were presented for AASHTO T134 and commentary was presented to provide state Departments of Transportation and other specifying agencies a few examples of how the new compaction delay protocols could be implemented.