Colored concrete can provide many benefits to pavement, such as improved aesthetics and safety. However, several recently constructed colored concrete pavements in Minnesota have experienced a considerable amount of early joint deterioration. Determining the cause for such deterioration is difficult, as there is very little knowledge in the literature on the performance of the material, especially in relation to its durability. Many different techniques have been used for obtaining colored concrete, such as granular pigments, acid dyes and stains, and dry shake powders. The various materials used to add color are all expected to influence the material properties of concrete differently.
This study resulted in Report 2014-26, "Investigation and Assessment of Colored Concrete Pavement," published in August 2014.
Thin bonded concrete overlays of existing asphalt pavements (BCOA), also known as “whitetoppings”, are becoming increasingly popular as an economical way to extend the life of an in-place pavement. While there had been several procedures developed in the past to structurally design this pavement rehabilitation option, the need for a more rational mechanistic-empirical based procedure still existed. Recognizing this gap in knowledge, the Minnesota Department of Transportation began in 1993 to construct various BCOA test sections designed to develop data for a comprehensive new design procedure for BCOA. By 2007, many other states in the U.S. were also interested in improved design procedures for BCOA. So in 2008, a 5-year long pooled fund research project was initiated and funded by 6 states, including Minnesota, Missouri, Mississippi, New York, Pennsylvania and Texas. By the completion of the project, the states of Iowa, Kansas, North Carolina and South Dakota had also joined the project.
Bonded concrete overlays over existing asphalt pavements, also known as “whitetopping,” are becoming an increasingly popular rehabilitation solution for many agencies. As with any rehabilitation technique, it is important to understand and incorporate cost effective features that will insure long lasting performance. Since the long term performance of thin whitetopping is reliant on a strong bond to the underlying asphalt, it is important to protect that bond for as long as possible. The primary way to reduce bond degradation is by keeping water away from the surface of the underlying asphalt. This is typically done by filling or sealing the contraction and panel edge joints with liquid (“hot-pour”) asphalt sealant. Due to the thin slab designs typically used for whitetoppings, panel sizes need to be smaller, thereby resulting in many more joints than in typical concrete pavements. With today’s restricted budgets, owners and engineers must consider whether the sealing or filling of joints in whitetopping provides an economic benefit.
This specification includes the requirements for the construction of concrete flatwork including pavements, curb and gutter, sidewalks, driveways, and aprons. When using these specifications, designers need to pick one or more of the following as additional bid items for additional quality improvements: concrete field testing, smoothness, maturity testing for strength, and enhanced aggregate qualities. Also the designer needs to decide which testing rate will be used on a project from either Table 5 or 6 of these specifications.
Sustainability in the design of pavements can be accomplished in two different ways. Either a pavement is designed to be more robust, so that it will have a significantly longer service life, or a pavement is optimized and designed to use significantly less materials, with the potential for a shorter service life. This paper examines the design concepts and field performance related to the latter type of concrete pavement systems in a cold climate.
Several thin full-depth concrete and thin unbonded concrete overlay pavements have been recently constructed in Minnesota. These pavements are being intensely studied to examine how truly optimized the design can be and still deliver safe, economical, and reliable performance. This paper summarizes the early and long-term performance of several thin concrete pavement test sections at the MnROAD test facility, as well as early performance observations from a larger scale project in northern Minnesota. Design concepts and details of multilayered concrete pavement test sections utilizing recycled concrete and other low cost materials are also discussed.
Based on the many valuable lessons learned from test sections at the MnROAD facility and throughout the state, local engineers are now comfortable designing and constructing thinner full-depth concrete pavements, as well as thin bonded and unbonded concrete overlays.
One of the best performing solutions for restoring or improving the performance of older concrete pavements in Minnesota has been unbonded concrete overlays. One reason for their good performance may be the inherent conservatism in their design. Since a rational mechanistic-empirical design method has not been adopted yet, their design relies on methods derived for concrete pavement placed on more traditional base layers. Since one of few variables one can change when placing an overlay is slab thickness, optimizing this thickness will ultimately lead to lower overall costs for this effective rehabilitation solution. Determining optimized overlay thickness is best accomplished by monitoring actual field test sections.
After 13 years of live interstate traffic and the extreme climate of Minnesota, the condition of the original concrete pavement test sections at the MnROAD facility was still very good. The introduction of Phase 2 research studies at MnROAD prompted the need to remove or replace several of those test sections. To extract all useful information from the sections before they were reconstructed (or overlaid), a comprehensive forensic investigation was conducted. This investigation focused principally on joint performance, as little panel cracking had occurred.
As jointed concrete pavements age, they typically experience panel cracking, joint or crack faulting, and surface distress. To maintain user satisfaction and safety, the agency or owner must identify the causes of the distress and consider types of feasible repairs, if any. These repairs range from partial to full-depth concrete repairs for spalled or cracked panels, to load-transfer and ride-quality restoration schemes for faulted cracks and joints. Retrofitting dowel bars into a distressed and faulted concrete pavement has become a proven technique for restoring or improving the capacity of jointed concrete pavements. The backfill materials and installation techniques used in retrofitting dowel bars must, however, be carefully designed. Numerous field and laboratory trials have been carried out in Minnesota in the recent past, allowing engineers and contractors to refine the installation techniques and materials necessary to produce long-lasting and effective projects. This paper provides a history of the development of best practices for retrofitting dowel bars into jointed concrete pavements located in the extreme climate of Minnesota. The performance of field test sections, up to 13 years old, are discussed in relation to dowel bar location, long-term load transfer capability, and durability of backfill materials. Implemented design changes based on results from accelerated loading laboratory studies are discussed. An effective installation method and materials testing process, required of contractors before constructing retrofit projects in Minnesota, is described. Retrofit dowel bar installation, in conjunction with restoration of the surface through diamond grinding, has been proven to significantly extend the capacity and serviceable life of many concrete pavements in Minnesota.
The traveling public desire pavements that are smooth, safe and quiet. This has generated research into developing pavements that optimize performance and are durable and affordable. Pavement Surface Characteristics include smoothness, frictional resistance, hydroplaning potential, texture, sound absorption properties, and tire-pavement noise including their effects in overall pavement performance. Pavements like Mn/DOT’s innovative Astro-Turf drag texturing technique, attempt to reduce tire-pavement noise while optimizing other desirable pavement characteristics. While surface characteristics are important, performance of Jointed Plain Concrete Pavements are substantially affected by joints, while the continuously reinforced concrete pavements are affected by the intermittent structural cracks. These features in conjunction with other distress and surface conditions affect performance characteristics of the pavements. This study focuses on fundamental surface characteristics of new Portland Concrete Cement (PCC) pavements, how they interact and how they change over time.
Developed by Magnetic Imaging Tools GmbH (Dresden, Germany), the MIT Scan-2 is a nondestructive testing device that uses magnetic imaging technology to measure the position of metal dowel bars embedded in concrete. It is very quick and easy to use. Less than five minutes are needed to scan each joint and reposition the device for the next joint. The hand held computer that controls the device allows the user to see the positions of the dowel bars in the joints immediately after scanning. It also has a very easy to use analysis program called MagnoProof that uses the specified dowel locations, along with allowable tolerances, to automatically identify misaligned dowels.
