Skok, Eugene L., Jr.

This summary report is an illustrated description of a surface condition rating procedure for flexible pavements. A slide tape presentation has also been prepared on this subject. This report and the slide tape can be used together to supplement each other and the report can be used as a reference during field condition surveys. Both documents are intended to be training aids for people who are responsible for evaluating pavement conditions and selecting appropriate maintenance procedure

The purpose of this three month study has been to determine whether it is feasible to simulate an asphalt pavement section using the elastic theory. This has been done by first obtaining samples from Investigation 183, Test Section 102 and determining the stress-strain properties of the various layers using the repeated load triaxial test under various conditions. Appropriate moduli have then been put. into an elastic layered system which is used to calculate stresses and strains within the system. The Benkelman beam deflections measured in the field have been simulated in this manner and the comparison between computed and measured deflections is used to show whether the elastic theory simulates a flexible pavement. The possibility of determining equivalencies between stabilized base courses and granular base courses are explored as are the use of other parameters for design purposes.

This report is the third and final of a series prepared for the Minnesota Local Road Research Board (LRRB) that contains summaries of highway research projects which have been conducted in Minnesota for the last 25 years. These summaries will be valuable references to city and county Engineers and others who are responsible for the construction and management of roads, streets, highways, and other related facilities. Volume III summarizes over 115 research projects which have been sponsored by the State of Minnesota Department of Transportation (earlier Department of Highways) since 1960. These research projects were all state funded by the Minnesota Department of Transportation (Mn/DOT). These projects cover a wide variety of subjects including surface treatment, pavement design and evaluation, materials evaluation, and roadside turf establishment to name a few. Much of the Information resulting from these projects is of value to all city and county engineers, as well as Mn/DOT engineers and the Industry.

This report is the second of a series prepared for the Minnesota Local Road Research Board (LRRB) that contains summaries of highway research projects which have been conducted in Minnesota for the last 25 years. These summaries will be valuable references to city and county Engineers and others who are responsible for the construction and management of roads/ streets/ highways, and other related facilities. Volume II summarizes over 35 research projects which have been sponsored by the State of Minnesota Department of Transportation (earlier Dept. of Highways) since 1960. Some projects received funding assistance through the Federal Highway Administration (FHWA) previously Bureau of Public Roads. These projects cover a wide variety of subjects including surface treatment, pavement design and evaluation, materials evaluation, and roadside turf establishment to name a few. Much of the information resulting from these projects is of value to all city and county engineers; as well as Mn/DOT engineers and the industry.

This report is the first of several volumes prepared for the Minnesota Local Road Research Board (LRRB) which contain summaries of highway research projects which have been conducted in Minnesota. These summaries will be valuable references to City and County Engineers and others who are responsible for the construction and management of roads, streets, highways and other related facilities. Volume I summarizes over 50 research projects which have been sponsored wholly or in part by the Minnesota LRRB since 1959. These projects cover a wide variety of subjects including geometric standards, pavement design and evaluation, materials evaluation, and roadside turf establishment to name a few. Much of the information resulting from these projects is of value to all city and county engineers, as well as Mn/DOT engineers and the industry.

The purpose of this synthesis is to bring together materials and information on the design and maintenance of low volume roads. A literature search has been obtained from HRIS, NTIS and the Engineering Index. Over 1,000 questionnaires were then sent to cities, counties and consultants in the northern tier of states and the Canadian provinces. Interviews were also held with representatives of Minneapolis-St. Paul, Duluth, Hennepin and St. Louis Counties regarding their low volume road design and rehabilitation procedures. These confirmed that much of the engineering for low volume roads is an offshoot of the procedures used for higher volume facilities. Based on the literature search, questionnaire responses and interviews, recommendations are made for thickness design of gravel, asphalt, and concrete pavements, stabilization of subgrade soils with bituminous materials, lime and/or cement. Recommendations are made to construct test sections to monitor special designs and materials. The final consideration in the selection of design and materials is the cost related to anticipated performance.

A revised method for designing flexible pavements in Minnesota has been proposed for use. It has been developed based on the performance of 49 in-service test sections throughout -the state. This method is developed in the Annual Report for Investigation 183 in June, 1969.

Investigation 183 began in April, 1963, with preliminary selection, of flexible pavements in each Construction District of the Minnesota Highway Department. Projects were selected where it was thought that well-defined design occurred and a good traffic history could be obtained. With the aid of the district soils engineers, the areas were checked for uniformity and forty-one test sections were laid out. In 1964 an additional nine test sections were set up, bringing the total to fifty. During the summers of 1963 and 1964 three phases of field work were completed on each test section, These were: (1) fractional plate load testing with in-place moisture and density determination of each layer and with samples of materials taken from each layer for laboratory testing, (2) determination of Benkelman beam deflections, rut depth, and cracking for each section, and (3) determination of the roughness index for each section. A second set of beam deflection tests has been run during the fall periods. Item (1) was conducted only once on each test section, i. e. on the original 41 sections in 1963 and on the nine new sections in 1964. Items (2) and (3) were conducted on all test sections in both 1963 and 1964. It is planned to run deflection and condition tests on each of the test sections on a periodic basis about once a year. The roughometer index is used along with the rut depth and cracking to determine a Present Serviceability Index as shown in Part V of this report. The trend of the PSI with traffic will define the performance of the test section.

The purpose of Investigation 183 is to translate the findings of the AASHO Road Test to Minnesota conditions, and in general to actual highway conditions. At the Road Test, relationships between load and pavement thickness were established for one set of materials and for controlled traffic. In this investigation relationships for other embankment materials and normal highway traffic as found in Minnesota will be developed, starting with the basic relationships obtained from the Road Test

The results of this study indicate that the best criterion for determination of the need for a seal coat on a bituminous surface is an inspection of the surface condition of the pavement. There are certain defects or stages of wear and deterioration which can be corrected or arrested by a seal coat, and others which are not corrected, or which are only temporarily "covered up" by a seal. Some knowledge and differentiation of these defects is needed when making an inspection to properly determine the need for the seal. Almost all statements on the effect of seals apply to sand seals, as with a few exceptions, this was the type observed.