Embankment construction is an important part of the highway construction process, and soils from borrow pits are often used to construct these structures. The soil from these borrow pits is often characterized as needed, on a project by project basis, and is tested for the properties necessary for embankment design. As the upstate of South Carolina is underlain by the Piedmont residual soil formation, unweathered mica is present in the soil. Current practice calls for Loss on Ignition testing when needed, but the studies looking at the effects of mica content on the other soil properties has been centered mostly in Georgia.

Borrow pits were sampled across the state, both with and without mica. The laboratory testing program included the following. Tests for physical properties include visual manual identification, moisture content, specific gravity, particle size distribution, liquid limit, plastic limit, and soil classification. Tests for mechanical properties include standard Proctor compaction, direct shear, and triaxial compression. Tests for chemical properties include soil pH, soil resistivity, chloride content and sulfate content.

Test methods were performed according to AASHTO standard specifications unless otherwise indicated. There were 12 micaceous samples tested and 27 non micaceous samples. The testing focused on parameters used in embankment design. It was found that mica testing is difficult, and that there is a need for a better method. The soil properties for micaceous and non micaceous samples were compared and a correlation was found between mica and compaction characteristics, which are paramount to embankment construction. The micaceous soils were also found to have a low sulfate content, although this does not seem to be cause by the mica content, but rather a characteristic of Piedmont residual soils. It was also found that soil plasticity tends to decrease with loss on ignition.