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The 1969 Legislature of the State of Minnesota under Minnesota Statutes, Chapter 169.72, directed the Commissioner of Highways to conduct an in-depth study on the safety and pavement-wear effects of studded tires. This, the final report of that study, summarizes the research efforts and the results. The report is prepared for the specific use of the 1971 Legislature. The Commissioner of Highways is indebted to the many organizations that cooperated in providing information: The American Oil Company for conducting the pavement-wear tests; Kennametal Corporation for furnishing and installing studs in test tires; Cornell Aeronautical Laboratories for the accident study and analyses; the Minnesota Highway Patrol and other offices of the Department of Public Safety for accident reporting and survey coordination; and the many city police departments for supplementing accident reports with data required for the study. Participating cities were Brooklyn Center, Duluth, Edina, Grand Rapids, Mankato, Minneapolis, , Richfield, Rochester, Roseville, St. Cloud and St. Paul. Special thanks are due those states that contributed funds for defraying part of the project costs: Illinois, Iowa, Michigan, New York, North Dakota, Pennsylvania, Utah and Wisconsin. The content, findings, and conclusions expressed or implied in this report are those of the Minnesota Department of Highways. They do not necessarily represent the views of the organizations providing data for the report or the cooperating states.

On highway construction projects it is necessary to determine moisture contents of soils and aggregates in connection with earthwork, subbase, base, concrete, and bituminous construction. This determination by the present conventional methods is time consuming, and there has been increasing criticism by contractors that tests of this type are causing delays in the progress of their work. Consequently more rapid methods have been sought for making reliable moisture control tests particularly on base materials and embankment soils. The purpose of this investigation was to determine the accuracy and time saving possibilities of the Calcium Carbide Gas Pressure (CCGP) Moisture Tester when used as a field testing device in comparison with conventional field methods for moisture content determination. This report presents the results of extensive field tests with the instrument. A previous study (Investigation No. 122) had established that moisture contents can be accurately determined with this device under the ideal working conditions of the laboratory. Moisture testers were placed on 14 field projects selected so that the widest possible range of soil types could be tested. Some base and subbase materials were also tested.

This study was undertaken to determine the comparative effectiveness of chloride salts and abrasive-chloride salt mixtures for ice removal. It was also desired to study the storage characteristics of sodium chloride, calcium chloride and mixtures of these materials. Controlled field ice removal tests were run on 15 combinations of materials within three temperature ranges. Data were collected on thickness of ice; actual quantity and location of chemical or abrasive applied; and periodic condition of the ice with regard to amount of ice removed. The outdoor storage characteristics of seven bulk materials and one packaged material under a light polyethylene sheeting were studied. The materials were sampled for moisture, crusting and caking for a period of 10 months.

Engineers who are associated with trenching in public thoroughfares have been striving for many years to find better construction methods and procedures for backfilling these trenches. We cannot expect the public to tolerate detrimental settlement if it can be avoided with a reasonable expenditure of funds. In this study the presently used procedures of backfilling and compaction were observed. It was found that these procedures can definitely be improved. The major conclusions which can be drawn from the study are listed below. The layered system is the most reliable compaction procedure for limiting settlement to a minimum. With one compactor type, the Hydra-Hammer, the entire trench backfill can be compacted in one lift irrespective of soil type or traffic volume on the street. Adequate stability, to prevent detrimental settlement, can be attained with many compactor types if the lift height is adjusted to soil type and condition, and the trench loading conditions. All vibratory type trench compactors should be used strictly on the granular soils and the lift height must be chosen with respect to the particular compactor and the traffic volume. The Pneumatic Button Head compactor can effectively compact all soil types in lifts up to 0.5 feet in thickness. The Plate Tampers are excellent compactors for all soil types and they are capable of compacting soil lifts between 1.0 and 1.5 feet depending upon the traffic load. Heavy construction equipment should be used to compact only the upper lift in a trench and this lift should be restricted to the range of 1.0 to 2.5 feet in thickness depending upon the soil type and the traffic load. Further research under more controlled field conditions is planned for 1963.

This report contains the results of experiments performed to discover the suitability of the concrete retarder Plasitment for Minnesota Department of Highways construction projects.

The thermoplastic pavement marking project, S.P. 2785-101 (T.H. 494), was let in 1963 as an experimental project under the Federal-aid highway program, with full Federal-aid participation in the cost of the work. This report covers application of the marking materials under this project and observations on performance during the first three months service.

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 as well as to Engineers of the Minnesota Highway Department. The project was conducted as a part of the Highway Planning Research Program financed jointly with Federal-Aid funds provided through the United States Department of Commerce, Bureau of Public Roads together with State funds and County and Municipal State-Aid funds. A laboratory study such as this generally does not provide all the information necessary to determine whether a particular method will prove satisfactory as a construction procedure or to accurately predict field performance. This laboratory study does show that lime has some possibilities as an effective treatment for certain Minnesota soils. However, an experimental field project is needed to establish the suitability of the various laboratory tests as a means for evaluating the adequacy of the soil-lime mixtures for use in road structures.

A limited supply of high quality base aggregates in several parts of Minnesota has resulted in a search for a means of improving the physical and strength characteristics of locally available soils and poor quality granular materials. Other states faced with a similar problem have attempted to use soil stabilization as a solution. Common stabilization agents include cement, bituminous materials, sodium and calcium chloride, and sulfite liquor. More recently, several southern states have successfully used lime for stabilization of roadbed materials. The purpose of this study is to determine the effect of hydrated lime on the physical and strength properties of typical Minnesota soils and aggregates. This first progress report presents the findings of tests conducted during 1961 using hydrated lime and five secondary chemical additives with five fine grained soils

The establishment of good vegetative cover and the control of erosion are two continuing problems being amplified by the expanding and changing highway program. Present methods of seeding, mulching and control of erosion have not kept pace with the advancing roadbuilding technology. Consequently, Maintenance Engineers are inheriting miles of new roadway annually many of which contain serious erosion problems. Six glaring examples of poor vegetative establishment and detrimental erosion became extremely serious in Minnesota during the summer of 1961. A pilot study was set up on these six problem areas to comparatively evaluate various methods of controlling the flow of water, slope preparation and topsoiling, seeding and fertilizing, and to evaluate a number of commercial mulches and erosion control products such as fiberglass, jute and paper fiber nettings, and plastic resin spray material. The major conclusion of the report is that present methods of establishment of vegetation and erosion control can be improved. Recommended improvements to present methods are: (1) sodded or lined ditches, dikes, and flumes should be used more freely where water flow is concentrated; (2) the seedbed should be prepared with agricultural equipment and operated on the contour to provide shallow ridges or furrows; (3) seed should be selected for maximum compatibility with the fertility level of the available topsoil and should be sown with equipment that will not damage or nullify the preparatory work; (4) asphalt emulsion should be used as a binder for hay and straw mulches; (5) jute netting should be used primarily in high discharge ditches; (6) bituminous treated fiberglass blankets may be used in high velocity, high discharge ditches; and (7) mowings should be made to a 4 inch height or greater to make the turf more resistant to drought and weed infestation. Further research is recommended on many of the items included in the pilot study.

Concrete pavements, particularly In the northern states, are subjected to stresses from climatic changes which not. only affect the load carrying capacity of the slab, but also the life expectancy or the durability of the structure. It was for the purpose of securing additional data to use in computing total stresses under load, and to determine durability that this investigation was started. Measurements have been taken over a twelve-month period. The method of taking measurements, and a summary of the data obtained are shown graphically.