Fredrickson, Fredrick C.

The purpose of this study was to evaluate the effect of formed polystyrene concrete cylinder molds on concrete strength. This report describes the various treatments given to cylinders, which were cast in steel, fiber, and polystyrene molds and the statistical analysis which was made on the 28 day compressive strength results. A recommendation is made concerning the use of polystyrene concrete cylinder molds.

The project was constructed by Wadena County in 1962 to evaluate the effectiveness of stabilizing the upper portion of a sandy subgrade with bituminous materials. It was also hoped to correlate the performance of the test section's with results of laboratory tests conducted in accordance with the recommendations of Investigation No. 608, "Bituminous Stabilization -Laboratory Study", recently published by the Minnesota Highway Department. The stabilized subgrade performed satisfactorily as base material on this project. However, similar results should not necessarily be expected on projects which have a different type of embankment soil or different traffic conditions.

This study was originated in 1960 at the request of the Minnesota Local Road Research Board. Its basic objective is to determine a means of backfilling slit-type trenches so that little or no settlement results. In the first four years personnel from the Research Section, Office of Materials, Minnesota Highway Department, collected data by observing trench backfilling during regular construction operations and then measuring the subsequent settlements. In 1964, 1965, and 1966 dummy trenches were excavated and backfilled under more controlled conditions. This work was done by the City of St. Paul and Minnesota Highway Department maintenance forces. All testing was done by Research Section personnel. In 1963, a progress report titled BACKFILLING TRENCH EXCAVATIONS was published by the Materials and Research Section, Minnesota Department of Highways. Included were general recommendations for street preparation, backfilling, and patching. Also, the effectiveness of various types of compactors was discussed and specific compaction procedures for given soils and traffic conditions were recommended. The results of the controlled backfill studies reported herein have confirmed certain of those recommendations for compaction procedures but have contradicted others. The investigation to date has not satisfied its objective and is being continued.

The project was initiated in an attempt to develop a procedure using standard laboratory tests for designing soil-bituminous mixtures for use on highway construction projects. The Hveem stabilometer and cohesiometer and the unconfined compression tests were evaluated for this purpose using several types of soils and bituminous materials. Procedures were developed for molding the specimens, determining their desired moisture content and conditioning them prior to testing. The design method developed in this study appears to be more applicable to plastic soils, but probably has merit in designing some types of granular soil-bituminous mixtures also. The recommended design procedures given in this report were used in designing an experimental field stabilization project in Wadena County in north central Minnesota. The soils stabilized were fine sand, loamy sand and loamy fine sand. Results of this study will be described in the final report on Investigation No. 612 "Experimental Bituminous Stabilization Project - Wadena County" soon to be published.

This investigation was initiated to determine the practicality of using preformed neoprene in lieu of the presently used hot rubber asphalt for resealing transverse joints in old concrete pavements. The transverse joints on two short sections of pavement in the Twin City area were resealed with neoprene to determine the most effective methods for removing the old seal from the joint, repairing spalls where required, and placing the neoprene joint sealer. On the basis of other studies it was assumed that preformed neoprene would perform better than hot rubber asphalt as a joint sealer. Therefore, the only basis for evaluation in this study is a comparison of the cost of resealing with the new materials. As a result of this cost comparison it is concluded that it is not economically practical to reseal joints in concrete pavements with pre- formed neoprene. Preformed neoprene has been used almost exclusively during the past. two years to seal transverse joints on new concrete pavement, construction. This use of neoprene in new construction is also being studied and it is anticipated that a progress report on its performance will be completed during 1968

This study was initiated to evaluate the effect of foamed polystyrene concrete cylinder molds on concrete strength. The objective of the research was to determine if polystyrene molds: 1) significantly protect concrete cylinders against extremes in temperatures during casting and the initial 24 hour cure period, and 2) eliminate the possible effects of rough handling of specimens which is sometimes encountered in stripping and shipping.

This report is a summary of "Minnesota Department of Highways Flexible Pavement Design - 1969."

The method presently used for flexible pavement design in Minnesota utilizes either average daily traffic (ADT) or heavy commercial average daily traffic (HCADT), along with a designation of 5-ton, 7-ton or 9-ton spring axle loads to categorize traffic. The AASHO soil system is used to classify the subgrade soil in order to vary the required base thickness from sections designated for an A-6 soil. The relative strengths of the layers in the pavement section are indicated by granular equivalent factors. The procedures and levels of thickness required have been established based on experience and performance evaluation on Minnesota Highway pavements for the past 30 years.