High quality aggregates for bituminous surface mixtures are becoming scarce in some parts of Minnesota. Some counties are using lower quality aggregates in wearing courses for their low traffic volume roads to reduce construction costs and to conserve the higher quality aggregates in their areas for other purposes. It should be mentioned that most areas of Minnesota have large quantities of sand and that these sands or finer aggregates are allowed in bituminous base courses and are performing adequately.
The purpose of this study is to determine if bituminous surfaces constructed with aggregate outside present MHD specification limits will perform adequately on low traffic, secondary roads. Wear resistance is the primary measure of acceptability for wearing courses constructed with finer aggregates for this study.
Projects were constructed in three counties with appropriate modifications in the MHD 2331 bituminous surfacing specification. Each of these projects was evaluated by visual observations. This report describes trial-mix laboratory tests, description of surfaced roadways prior to and after overlay, and performance observations.
This revised test. method covers the procedures for determining the Resistance value of untreated embankment soils and aggregates for use as base and sub-base, The last revision of this test method was in December of 1960. The major change in the procedure as documented in this
report is in the selection of 240 psi as the exudation pressure to use to select the design R-value.
This study compares the performance of a conventional flexible pavement (bituminous surface with granular base and subbase over untreated soil) with the performance of pavement designs incorporating lime stabilized soils. Included in the project were seven experimental sections each 1/4 mile long having various thicknesses of base and subbase and percentages of lime incorporated into the embankment soil. The report describes the soils, testing, design, construction and performance of the project. The lime stabilized test
sections cost more and had more cracking and lower present serviceability indexes than the control sections.
