Transportation Research Record: Journal of the Transportation Research Board

A large performance data set from in-service pavements was used in conducting a reliability-based analysis to determine the life expectancy (performance) of several preventive maintenance (PM) fixes. The distress index (DI)—the main pavement performance indicator used by the Michigan Department of Transportation—was used in the analysis. Probability distributions of DI values were developed at successive years after the PM application for five fixes: nonstructural bituminous overlay, surface milling with a nonstructural bituminous overlay, single chip seal, multiple-course microsurfacing, and bituminous crack seal. Reliability tables were then developed to express the probability that a given PM treatment would reach the performance threshold after n years; these tables therefore provide the pavement life expectancy for a given PM treatment at various reliability levels. A highway agency can use these tables to select PM strategies on the basis of expected life extensions.

Various transportation agencies have begun to consider implementing preventive maintenance (PM) strategies as part of their regular pavement management programs. To determine whether a PM strategy is more cost-effective than a conventional maintenance strategy, various technical and economic analyses were carried out. Currently, most agencies have limited information on the cost-effectiveness (CE) and long-term performance of PM strategies, so it is difficult to determine when and where these treatments should be used. The use of PM treatments based on a CE calculation and analysis is examined, and a decision tree (including treatments and strategies) is developed for each functional pavement class of the Ontario road network. Pavement data from the Ministry of Transportation of Ontario are used to perform a CE calculation for each suggested PM treatment and strategy. On the basis of a comparison and analysis of CE calculation results, guidance is provided on the right treatment, time, and strategy cost level for each functional pavement PM program within the Ontario environment. The results are summarized in the form of a decision tree.

Thin maintenance surfaces (TMSs) provide an economical method of extending pavement life for asphaltic concrete or bituminous roads. Two phases of research were undertaken to demonstrate TMSs and establish guidelines for their use in Iowa. The project involved the construction and observation of multiple test sections on four rural U.S. highways in Iowa over a 3-year period. Average annual daily traffic on these highways ranged from approximately 1,000 to 5,000. Test sections included single and double chip seals with various types and sizes of aggregates and two types of binder: cationic emulsion and high-float emulsion. Test sections of microsurfacing, microsurfacing cape seal, and thin-lift hot-mix overlay were also placed. These TMS treatments were compared with control sections. Researchers designed the chip seal test sections, monitored the construction process, and collected quality-control information on materials. The pavement condition index (PCI) and skid resistance were measured and compared for each test section before and after construction. TMSs improved PCI when materials were selected properly and quality construction techniques were used. Success was achieved with chip seal that used graded cover aggregates and small cover aggregates and also with various thin-lift overlays. Difficulties were experienced with microsurfacing aggregates that had few fines. The results of the study reinforce the importance of selecting the right type of TMS, ensuring construction quality, and having favorable weather during and after construction.

The performance of joint sealants and the structural condition of the pavement at the Ohio Route 50 test site after 3 years in service are reported. The project involved 10 different sealant compounds (4 silicone, 2 hot-applied, and 4 compression seals) and 4 unsealed sections. A total of 15 different sealant-joint configuration combinations are examined. Compression seals generally outperformed the other sealants, and sealants in the westbound lanes were more effective than those in the east-bound lanes. These observations suggest that crew experience in sealant installation is a critical factor. Nonetheless, structural performance and surface profile smoothness appeared to be unrelated to sealant condition. Many of the sealant sections with high effectiveness values also exhibited high percentages of structural distresses and decreases in pavement surface smoothness. Flooding after intense rainfall may have softened the subgrade and caused transverse cracking and corner breaks. Implementing a drainage outlet maintenance program that includes cleaning silt and debris from the outlets annually is recommended. Unraveling the complex interactions of all these factors calls for long-term monitoring of both sealant and structural performance.

A bridge management system (BMS) needs an analytic tool that can predict preservation needs based on the deterioration process of bridges and answer what-if questions. Pontis software was developed to serve this purpose. Because of its intensive data requirement, Pontis has not been fully implemented by the Louisiana Department of Transportation and Development (LaDOTD). Although LaDOTD has initiated a project to collect the Pontis element data, the project will take several years to complete. An innovative approach was developed using readily available National Bridge Inventory (NBI) data in Pontis to evaluate the long-term performance of the bridge system under various BMS alternatives. The deterioration process of three NBI elements was studied, and element deterioration models were developed. Bridge preservation plans and associated cost schemes were defined according to current LaDOTD practice and available information. Findings indicate that using NBI data for BMS analysis with Pontis is not only feasible but also practical. While waiting for the completion of the Pontis database, LaDOTD can use readily available NBI data to analyze and evaluate the long-term performance of the bridge system under various budgetary and operating scenarios. Initial results indicate that LaDOTD's current annual budget of $70 million is sufficient to meet the needs of only bridge preservation, not functional improvement. If implemented successfully, the bridge preservation plan can maintain the system in good operating condition for a long time with a limited annual budget.

Bridge management systems can be classified as one of two types: network level or project level. The former type is concerned with the prioritization of bridges for inclusion in an upcoming maintenance, repair, and rehabilitation program, and the latter focuses on the repairs that suit the components of a selected bridge. Even though these types are interrelated, most bridge management research treats them as separate aspects. A comprehensive framework is presented for a bridge deck management system that aims at integrating project-and network-level decisions into a unified model to optimize costs at both levels. The novelty of the proposed approach stems from three main aspects: incorporating project-level repair options along with their performance improvements and cost implications; incorporating many flexible and practical features such as variable yearly budget limits, variable yearly discount rates, and optional methods for handling project-level repairs (e.g., single or multiple visits); and using a powerful genetic algorithm-based optimization to consider both project- and network-level variables into bridge life-cycle cost optimization. The proposed model and its implementation are described, and an example application is presented. Although this research focuses on bridge decks, details on future improvements to incorporate all bridge components are outlined.

The discipline of bridge life-cycle costing is at a turning point: it could soon become far more useful and used than ever before for a range of decisions about bridge engineering and management and for broader asset management. Several important new research-and-development studies have provided essential tools and resources previously unavailable, and many agencies are starting to amass valuable databases of information about inventory, structures, and condition. A vision of how these diverse products of numerous researchers and sponsors can be brought together to greatly increase the practicality and value of bridge life-cycle cost analysis at the project level is presented.

Magnesium chloride (MgCl₂) use for snow and ice control is becoming a well-established practice but has been limited to the past 10 years. Impacts associated with sodium chloride (NaCl) use are well documented, but concerns have been raised regarding the potential effects of MgCl₂ use on concrete and steel reinforcement. The British Columbia Ministry of Transportation intended to establish guidelines for MgCl₂ use by highway maintenance contractors. Information was gathered from available literature and interviews with academia and industry. Generally, few studies directly and comprehensively address the topic, and although significant research efforts are currently under way, results are not expected for several years. Past laboratory studies suggest that MgCl₂ reacts with cement paste to reduce concrete strength and degrade concrete. Studies also suggest that chloride ions associated with MgCl₂ have higher diffusion coefficients than those associated with NaCl. Field studies are limited, but laboratory coefficients for chloride ion diffusion correlate with results of a field study conducted in Montana. Higher chloride diffusion coefficients can reduce the initiation time for chloride-induced corrosion of reinforcing steel. No evidence to date directly links the increased deterioration of a structure to MgCl₂ use; however, the history of use is short, and caution is recommended until additional studies can establish more evidence.

A novel performance evaluation system for main reinforced concrete girders of existing bridges evaluates durability and load-carrying capability by using technical specifications and results of simple visual inspections. Three features of the system are described. The first feature is the application of an expert system. Because the purpose of this study is to develop a novel system to evaluate the performance of a bridge element with limited information provided from simple visual inspections, it is necessary to embed into the system the knowledge of bridge experts. The second feature is a neuro-fuzzy hybrid inference. The system performs a fuzzy inference to simulate the inference mechanism used by experts for evaluating bridges. This process is integrated into a computer as a neural network; therefore, the system improves the knowledge base by using the back-propagation method. The third feature is the visualization of the inference process. The system must clearly explain how the outputs are calculated because the road networks, including bridges, represent important investments that must be carefully monitored. The learning capability of the system is demonstrated on an existing bridge in Japan. The effectiveness is verified by comparing the diagnostic results provided by a bridge expert and those proposed by the system.

Of all the components that compose a highway bridge, the bridge deck usually deteriorates the most quickly and requires the most maintenance and repair because of its exposure to detrimental conditions. Several preventive maintenance techniques are available to retard bridge deck deterioration and thus prolong service lives. Of these techniques, types of bridge deck overlays are investigated. As preventive maintenance, an overlay provides a protective layer between the bridge deck and the detrimental conditions that promote deterioration. In general, this protection enhances the material properties of the overlay, which may include low permeability and resistance to chemical attack as well as added thickness. The overlay procedures used for bridge decks in Tennessee are investigated from information about overlay types and their usage obtained through several sources, including interviews with Tennessee Department of Transportation personnel who are experienced in bridge maintenance. Four types are identified: asphalt, reinforced portland cement concrete, nonreinforced polymer-modified concrete, and thin bonded overlays. Each overlay is described and typical applications, bridge deck preparation, general construction techniques, special considerations, expected service lives, and average costs are discussed. Expected service lives ranged from 15 to more than 30 years, and average costs ranged from $30 to more than $100 per square yard. All overlay types are useful and appropriate under different situations.

An inventory system for retaining walls and sound barriers includes information about location, age, service, type, dimensions, and appraisals of a structure together with element-level models and element-level condition reports. Many of the inventory items and appraisals are adapted from the U.S. National Bridge Inventory record. Elements for walls and barriers indicate structural form and material, much like Commonly Recognized (CoRe) bridge elements. Potential uses of the inventory system in maintenance management and asset preservation are noted.