Wilde, W. James

Many state, county, and municipal highway agencies have experienced the formation of bumps when placing single-lift overlays or the first lift of a multiple lift overlay. These bumps are produced at the location of a previously-existing crack, and even then almost exclusively when the crack has been sealed prior to the overlay. When such bumps are not covered with a subsequent lift, what remains is often a rough ride on a newly-overlaid roadway. This paper describes the effects of crack sealant material type and the geometry (shape) of the routed cracks in the existing surface on the formation of bumps in bituminous overlays. A matrix of four sealant type treatments and six geometries was designed, and implemented in a test section in Jackson County, Minnesota. The overlay on the test section was constructed in September 2007. The results of this investigation indicate that cooler pavement surface temperatures, no overband, hot-poured crumb rubber and hot-poured elastic sealants provided the best resistance to the formation of bumps in overlays. Content Note: This is the author’s version of a work that was accepted for publication in the Transportation Research Record: Journal of the Transportation Research Board, Issue Number: 2108, Publisher: Transportation Research Board ISSN: 0361-1981. The final version can be found at https://doi.org/10.3141/2108-08.

 The Minnesota Department of Transportation (Mn/DOT) is currently evaluating a change from the Profile Index (PI) to the International Roughness Index (IRI) for smoothness specifications for portland cement concrete (PCC) pavements. This change has already occurred for bituminous pavements in Minnesota. The Mn/DOT Office of Materials, as well as paving contractors in Minnesota, is naturally concerned with the effects that this change will have on the quality of pavement surfaces and on the incentives paid for new pavement smoothness. The Office of Materials has funded an “implementation” project to compare the two smoothness statistics and to provide recommendations for implementing the new specification. This paper contains several analyses and comparisons of the relative effects of pavement features in design and construction with regard to the results of pavement surface smoothness and incentive computations. It also contains an analysis of segment length for incentive/disincentive calculations on PCC pavement projects. The information presented in this paper can be useful to those considering changing pavement smoothness specifications from profile index to international roughness index. This paper was submitted to the Transportation Research Board for the 2007 Annual Meeting.

The use of hot mix asphalt (HMA) overlays is common in Minnesota. However, while overlaying pavements with sealed cracks, bumps tend to form in the overlay resulting in decreased overlay smoothness and poorer ride quality. Hypotheses as to why (or how) these bumps are caused include:  Thermal expansion of sealant during overlay  Roller slip or slide as it rolls over sealed crack  Differential melting points of the sealant and asphalt binder  Vertical compression of sealant under roller. Prior research (LRRB Investigation 802) studied the thermal expansion hypothesis. Results showed that sealant materials may soften during overlay placement but not expand. It appears likely that the bumps may be formed during rolling operations; either by compression of the sealant or by slipping or sliding of the HMA material. This project conducted field testing to examine these issues, evaluate the probability of the occurrence of bumps, and look at ways of mitigating any bumps that do occur.

This brochure accompanies Report 2010-31; Predicting the Occurrence of Bumps in Overlays.

This spreadsheet tool pertains to report 2012RIC11, Traffic Generating Development and Roadway Life Consumption.

Mn/DOT awards bonuses to contractors for constructing particularly smooth pavements and assigns penalties for rough pavements. Such incentives and disincentives lead to pavements that provide a smoother ride and last longer. This results in a net taxpayer savings, even with the incentive payouts.

This report describes the implementation of the TONN 2010 analysis method for estimating spring load capacity of roads using pavement structure and traffic data, and results from the falling weight deflectometer. The resulting tool is a spreadsheet which combines the work of two other research projects– the FWD Viewer Tool and the TONN 2010 analysis (developed by Minnesota State University and the University of Minnesota, respectively). This project also included the development of training materials that were presented to county and state aid engineers throughout Minnesota.

This report provides a brief overview of recent research and current usage of various pavement-related topics in Minnesota, including: -Use of RAP in local pavement design, -Implementation of an updated vehicle classification scheme, -Pavement design charts for ten-ton designs, -Revision and update of the FWD Viewer Tool, and -Overlay design method for the FWD Viewer Tool. The review of these topics includes recommendations for further study or for implementation. The two topics related to the FWD Viewer Tool were investigated further, including implementation which was included in this project. Implementation activities included development of spreadsheet tools and statewide training among local transportation engineers for their use.

Several large wind farms have recently been built in Minnesota, producing heavy construction traffic that most county roads were not designed to accommodate. These construction projects can cause severe damage to the roadways, generating truck traffic in one season that can exceed 20-year estimates used in design. County engineers needed a tool to estimate expected roadway damage as closely as possible to help determine costs to be recovered through developer agreements and to prepare realistic road repair budgets for consideration by county boards.

This report describes the development of a tool to estimate the impacts to pavements associated with heavy vehicle traffic related to the construction of large wind turbine developments. In a growing number of areas, large wind farms are constructed in a very short time, often resulting in extreme impacts to the pavements on which the construction traffic must travel. This report attempts to assist the local agency in estimating the damage expected due to the sudden influx of construction traffic and in predicting the associated maintenance and rehabilitation costs to the road network used by the traffic. The Traffic Generators calculation tool for estimating pavement impacts, developed as part of this project, is a spreadsheet based tool that takes user input from the agency as well as the developer, and combines this information into an estimate of pavement damage. This is done in three ways – difference in granular equivalent pavement design, MnDOT overlay design, and percent of pavement life consumed. With guidance in this report, the agency can select which of the three methods is most appropriate for their particular situation. The tool then provides an estimate of cost required to repair the roadway network to its condition prior to the heavy influx of construction traffic.