Pavements

This report reviews the asphalt pavements in northern Minnesota on the criteria of density, smoothness, and mixture and gives recommendations for improvements.

The 2022 construction season at the MnROAD facility saw construction of 39 new and unique pavement test sections and the repairs of 6 existing test sections. These sections were planned and designed by the National Road Research Alliance (NRRA) teams to address high-priority research needs. This report details development, design, and construction of each test section supporting the associated research studies developed by the teams. Individual study details are left to future reports generated by the individual research contracts and their respective NRRA teams. As a multi-state, pooled-fund program, the National Road Research Alliance (NRRA) provides strategic implementation of pavement engineering solutions through cooperative research. For Phase II, NRRA focused on improving sustainability and resiliency of our national pavement system and studying and promoting intelligent construction technologies. Based on these goals, some test sections were rehabilitated to extend their life by recycling in-situ material and applying preventive maintenance techniques. Newly constructed tests sections used innovative materials such as plastic, rubber and fibers for asphalt pavements and alternative cementitious, alternative supplementary cementitious, and carbon injection for concrete pavements. Two test sections served perpetual pavement and wicking geotextile research projects. Both were designed and constructed as perpetual pavements one of them with a wicking geotextile on top of the subgrade for improving drainage and stiffness of road foundation and quantifying its long-term benefits. Six test sections were repaired using performance engineered mixes on the replacement panels and finished with diamond grinding to eliminate faulting.

This research summary pertains to Report 2023-35, "BMP For Issues with Asphalt Centerline Joint and Intelligent Compaction for Local Agencies," published November 2023

It is well-known that longitudinal joint construction quality is critical to flexible pavement life. The maintenance activities caused by longitudinal joint deterioration's direct or indirect effects and raveling problems along the centerline paving joint of asphalt roadways have become challenging for many highway agencies. A poorly constructed joint can lead to premature deterioration of an otherwise sound pavement. Thus, improving the joint’s construction can improve density and decrease permeability. It is probably the single most crucial remedy to enhance pavement performance. A density profiling system (DPS) provides continuous, instead of limited, coverage provided by conventional joint quality evaluation methods. Statistical, probabilistic, and percent-within-limits (PWL) analysis of DPS data suggests avoiding the construction of an unconfined joint. Tapered joints, confined butt joints employing the Maryland method or otherwise, echelon paved, and unconfined butt joints with cut back can produce adequate compaction at the joint.

A 5-year study of newly constructed pavements showed that a reduction in in situ air voids occurred both within and between wheelpaths for highways with an average daily traffic (ADT) load of less than 10,000 vehicles. Regardless of the level of voids immediately after construction, mixtures in the upper 65 mm (2.5 in.) within the wheelpath indicated a reduction in voids by 3 to 5 percent (e.g., from 10 to 6 percent voids), and by between 2 to 4 percent between the wheelpaths. Because only limited densification occurred below this depth for lower–traffic-volume facilities, reducing the mix design level of air voids from 4 percent to 2 percent for the lower lifts was suggested so that lower initial voids could be obtained during construction. An evaluation of older pavements indicated that moisture damage to the lower pavement layers was typical; thus, a change in mix design procedures might also help improve durability by increasing the film thickness. Pavements with high traffic volumes (>50,000 ADT) consistently indicated an increase in voids over time in the upper lift [40 mm (1.5 in.)], little change in the middle 65 mm (2.5 in.), and a decrease in the bottom 65 mm (2.5 in.). The hypothesis suggested to explain these findings was that a loss of material in the upper lifts was occurring, most probably due to moisture damage as the upper, more permeable wear course, commonly used in Minnesota, allowed water trapping at the wear and binder course (i.e., less permeable) interface. A further investigation of in situ void changes on an interstate indicated that for a pavement constructed with the same fine gradation in all lifts, traffic compacted the mixtures in a manner similar to that in low-volume roads. When the initial in situ voids increased from around 7 percent to nearly 10 percent, the influence of traffic on the densification was substantially increased. 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: 1575, Publisher: Transportation Research Board ISSN: 0361-1981. The final version can be found at https://doi.org/10.3141/1575-01.

This is a summary of the traffic phase at the above mentioned project based on data collected from Clay, Washington and Wright Counties. This project was initiated by the Minnesota Local Road Research Board in August 1975 and coordinated by the Physical Research Section of Mn/DOT. The project was started because of insufficient data available to set realistic spring load restrictions or design bituminous and other road structure improvements. The report covers the field data collected and the methods used in processing the data. The appendix contains specific data from individual locations in each county.

The new turbulent-mass process for mixing asphaltic concrete paving mixtures has been under study since its recent introduction in 1970. It is increasing in popularity with contractors because of two reasons: the mixing plant requires less equipment; and the process itself appears to result in a significant reduction in polluting emissions. All of this should reduce the cost of production. Field and laboratory tests and observations indicate that a satisfactory product can be produced by this process, one that is at least equal to conventional plant-mix

Beginning in 1968, Benkelman beam deflection tests were run on 25 bituminous roadways located throughout the state. Tests were run before overlay, just after these projects were overlayed, one year after, and two years after. The results were analyzed to determine the strengthening effect of the bituminous overlay. In conjunction with this study, Benkelman beam tests were run at various short intervals on a number of randomly selected flexible pavements. These results were used to develop a testing schedule (number and location of test points required) in order to assess the deflection characteristics of a flexible pavement within a given degree of accuracy.

This investigation was included in the research program of the Minnesota Local Road Research Board as a project of special interest to County and Municipal Engineers in addition to Engineers of the Minnesota Department of Highways. The purpose of this study was to develop criteria for determining the need for seal coating bituminous surfaces. This investigation basically consisted of a review of current local practices made during the initial stages of the project, followed by field evaluations of a number of seal coat projects from the 1966 and 1967 seal program.

This study was initiated to evaluate the performance of a continuously reinforced concrete pavement under the influence of concrete shrinkage, temperature change and traffic. During September and October, 1963, the Minnesota Department of Highways, in co-operation with the Bureau of Public Roads, paved its first continuously reinforced concrete pavement on S.P. 6680-29 (T.H. 35 between the north junction of T.H. 65 at Faribault and 0.2 mile north of junction T.H. 19). The entire project was 10.7 miles in length, with a section of standard jointed pavement adjoining each end of the 5.8 miles of continuously reinforced pavement.