A Mechanistic Explanation of The Physical Properties of Undisturbed Loess, February, 1968

The relation between the properties and the water content of an undisturbed loess were investigated to provide insight into the mechanical behavior of the natural soil. Hand-carved samples from a single deposit, at their natural water contents, and at water contents modified in the laboratory to provide a range from 870 to 3270, were subjected to unconsolidated-undrained triaxial compression tests, consolidation tests, and initial negative pore water pressure tests. In addition, the clay-size fraction was separated from the remainder of the loess for a separate series of tests to establish its properties. The natural water content of the deposit in the field was measured at regular intervals for one year to provide an example of the range in properties that would be encountered. at this site. The test results are presented and their interpretation leads to conclusions regarding the volumetric relations that exist as the water content varies. The significance of the water content in relation to the properties of the natural soil is explored and the concept of a critical water content for loess is introduced.

Frictional Properties of Asphalt Concrete Pavements in Iowa, MLR-87-5, 1987

Friction testing of pavements has been a continuing effort by the Iowa Department of Transportation since 1969. This report details results of tests of asphaltic concrete pavements on the primary and interstate road systems. Both sprinkle treated and non-sprinkle treated pavements placed between 1975 - 1985 are included. A total of 1785 miles representing 216 separate paving projects were examined. The effect of fog sealing sprinkle treated pavements was studied by testing friction levels before and after the application of the fog seals. Conclusions of the report are: 1. Current aggregate selection criteria for a.c. pavement surface courses provides adequate friction levels through 10 years and should remain effective through a 15 year design life. 2. Sprinkle treatment of pavements has, for the most part, provided macrotexture in the pavement surface as evidenced by smooth tire testing. 3. Fog sealing sprinkle treated pavements does not significantly alter the friction properties.