TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 346: State Construction Quality Assurance Programs examines current quality assurance practices of state and federal departments of transportation with regard to highway materials and construction. The report focuses on the strategies and practices used by agencies to ensure quality.

This report describes a project in which approximately 6,200 tons (5,630 Mg) of asphaltic concrete were recycled through a conventional asphalt batch plant. During the construction of the project, a buildup of asphalt-coated fines occurred in the dryer and the dust collector. The buildup is thought to have been associated with the fineness and/or the high asphalt content of the recycled mix. To solve the problem, a change was made in the recycling process. The project was completed using a heat transfer method with mix proportions as high as 50% recycled material added to 50% virgin aggregate.

Fabric reinforcement was used in an attempt to prevent reflection cracking of two bituminous concrete layers overlying an 8-inch plain (unreinforced, unjointed) concrete base that was underlain by a portland cement stabilized subbase material. On these pavements it was expected that the extremely rigid base and subbase layers would reduce vertical motion to a minimum. Similar pavements constructed with no overlay reinforcement readily showed reflection cracking in the bituminous layers, presumably because of horizontal, thermally induced movements of shrinkage cracks in the concrete base.

This synthesis will be of interest to state DOT construction, materials, statistical, specification, and inspection engineers; DOT research staff; pavement construction material suppliers; highway construction contractors; and civil engineering consulting firms, including field and laboratory materials testing personnel. The synthesis describes the state of the practice for defining and measuring variability in highway pavement construction. Data obtained from a review of the literature, a survey of state departments of transportation (DOTs), and discussions with selected state DOT personnel and private materials producers are presented. This report of the Transportation Research Board defines several measures of variability but concentrates on the use of standard deviation as the usual measure of variability. The synthesis updates reported typical variabilities found in materials and construction specifications. Also included are discussions of current research activities as related to variability, how variability can be used in the development of specification limits, the use of incentives and disincentives in specifications, and the need for additional information on the variability of several materials and construction processes.

This report traces the development of and explains the operation of a Construction Manpower Management System (CMMS) developed for the Virginia Department of Transportation (VDOT). Initial direction for this project was received from the Construction Engineering Manpower Management System Pooled Fund Study and a study performed for VDOT by Price Waterhouse and Roy Jorgensen Associates, Inc. Technical input was received from a project steering committee consisting of VDOT engineers, inspectors, and administrators. This system has been tailored to the specific needs of VDOT and provides projections of construction inspection staffing needs for both the short-term (the next 18 to 24 months) and the long-term (the next 6 years). The short-term projections are very accurate and appear quite adequate for use as a manpower staffing tool and for VDOT presentations to the General Assembly. As anticipated, the long-term projections, which are based on less certain project schedules in years 4 to 6, are not as accurate as those in the short-term. Thus, little use of long-term estimates are anticipated for planning purposes at this time.

This report describes the materials, mix properties, and early pavement cross sections of two mixes placed on Route 50, Fairfax County, in August 1988. The difference in the two mixes was that one contained a natural and the other a manufactured sand. Because the natural sand used was similar in surface characteristics to the manufactured sand, no significant differences in mix characteristics or performance were discerned. Measurements will be made periodically to determine if rutting is occurring.

In 2000, the Virginia Department of Transportation's (VDOT) Chief Engineer asked the Virginia Transportation Research Council to develop a vision of how and when VDOT would have a working end-result specification for hot-mix asphalt. The response to that question was that it would take several years and many steps to achieve. This report discusses the next step in that ongoing effort, which includes the development and simulated application of two statistical quality assurance (SQA) special provisions, one for asphalt concrete material and the other for asphalt concrete pavement. The criteria for these prototype SQA provisions included the application of standard national terminology and approach, a firm basis in existing VDOT specifications, and quality characteristics that represent the best practical performance measures. This report describes the outcome of a "shadow" application of the proposed SQA specifications to a subset of Virginia's annual maintenance-resurfacing projects. Although the involved production and placement activities were not subject to the requirements of the SQA specifications, the sampling and testing were designed to represent what would have been required had the special provisions been in effect. The study further determined the likely acceptance outcome for each shadow project and explored future modifications to specification limits and pay adjustment criteria. The most desirable benefit from effective end-result specifications stems from the ability to rededicate available inspection to those key production and placement processes (e.g., joint tacking and surface preparation) that cannot be measured upon delivery to the owner/agency. A less desirable, but more tangible, financial benefit results when these specifications permit a reduction in the overall inspection force. One conservative estimate suggests that VDOT could save more than $2 million per year in inspector salaries through an end-result specification for acceptance of hot-mix asphalt pavements

This report summarizes the design and field installation of an asphalt mix containing up to 3.0% closed cell rubber by weight of the mix. The performance is discussed as well as possible reasons for the early failure of the mix. Suggestions are made for avoiding failures if it is decided to use rubber modified mixes in the future.

This synthesis will be of interest to construction and materials engineers, paving contractors, equipment manufacturers, and others who are involved in assessing the performance of asphalt pavements. Information is presented on various issues related to compaction of asphalt pavements. Compaction is one of the most important factors affecting the performance of asphalt pavements. This report of the Transportation Research Board describes the theory, methods, equipment, and specifications related to the compaction of asphalt pavements. A brief history of, the importance of, and factors affecting compaction are also discussed. Construction influences, density measurements, and trends are also considered.