Prashant Ram

Field Study of Air Content Stability in the Slipform Paving Process

This study evaluated the impacts of construction on the air content and air void system structure of portland cement concrete pavements. The primary intent was to quantify the air content of fresh concrete before and after it had gone through the slipform paver. The air void system parameters of hardened concrete were then assessed with cast cylinders and extracted core specimens. The results of the air content testing on fresh concrete and the concrete cylinder specimens cast in the field suggested that some loss of air (approximately 1%) occurred as the concrete passed through the paver. Laboratory testing performed on cores extracted from the pavement did not provide conclusive evidence that entrained air was lost during the slipform paving process. In fact, many extracted cores had measured air content values that were much higher than those measured in the fresh concrete and even higher than the specification requirement. If excessive, such values could result in increased permeability and low-strength-related issues. The results suggested that the air content testing on fresh concrete did not capture the true air content of the concrete as it was placed with a slipform paver. The fresh concrete air content in general was lower than was the air content measured in the cores.

Performance and Benefits of Michigan Department of Transportation's Capital Preventive Maintenance Program

The Michigan Department of Transportations (DOT) pavement preservation program dates back to 1992. In Michigan, pavement preservation is implemented primarily through the Michigan DOTs capital preventive maintenance (CPM) program, in which preventive maintenance treatments are used to protect existing pavement surfaces, to slow deterioration, and to correct surface deficiencies. An overall objective of the CPM program is to postpone major rehabilitation and reconstruction activities by extending the service life of pavements. Results of a study performed to calculate the benefits and costs of various preventive maintenance treatments used in the Michigan DOTs CPM program are presented. With benefit defined as the percentage increase in performance over a do-nothing or untreated pavement performance curve where data were available, benefits were calculated for preventive maintenance treatments. Benefit–cost ratios were calculated by unit cost, and permitted the comparison of the cost-effectiveness of similar treatments. The overall performance of the Michigan DOTs CPM program was also examined by comparing the life-cycle costs of a rehabilitation strategy to a preservation strategy with the use of a simplified approach. The outcome showed that the preservation strategy resulted in agency cost savings of approximately 25% per lane mile over a rehabilitation-only strategy. Findings from this study can be used to help the Michigan DOT improve its CPM project selection, treatment selection, and performance monitoring and modeling practices.

Developing a Correlation Between the Pavement Condition Ratings Used by Five Federal Lands Management Agencies

The Federal Highway Administration’s Office of Federal Lands Highway works closely with its federal and tribal transportation partners, collectively called Federal Lands Management Agencies (FLMAs). A review of the various pavement condition assessment methods used by five of the FLMAs showed that each one was different and that there was no uniform basis to compare pavement conditions on a national basis. This paper presents the results of a study performed to develop statistical models to crosswalk the paved road condition ratings of the National Park Service, the U.S. Forest Service, the U.S. Fish and Wildlife Service, the U.S. Army Corps of Engineers, and the Bureau of Land Management. To achieve this objective, two major field studies involving independent condition assessments of several federal lands roads by the FLMA representatives were conducted. The results of the field studies and the subsequent analyses of data demonstrated that the individual rating procedures used by each FLMA could be reasonably crosswalked to the pavement condition index (as specified by the ASTM D6433 standard), allowing for a consistent method of reporting FLMA pavement conditions nationally.

Durability of Concrete. Second Edition

This circular is an update to Transportation Research Circular 494: Durability of Concrete, published in 1999. This revised publication is intended to provide the latest information for consideration by practitioners on producing durable concrete for transportation structures and pavements. Considering the number of facilities that have required repairs and reconstruction before reaching their intended service life, as well as the cost of the rehabilitation and the inconveniences to the traveling public, the importance of constructing long-lasting bridges and pavements continues to capture national attention and remains a high-priority item. This document is divided into sections introducing each topic and discussing the production of durable concrete through materials selection, proportioning, construction practices, specifications, and testing. Also included is a section of case studies, providing examples of problems encountered in the field that involve concrete pavement and bridges, along with the proposed solutions by the authors of the studies.