Heavy Civil Exam 2 Practice 2026 – Comprehensive All-in-One Guide for Exam Success!

In soil behavior, moisture content controls how the soil feels and acts. As water content decreases, soil goes from liquid to plastic to semi-solid, and finally to a rigid solid. The point at which it still behaves plastically but just starts to crumble when dried a bit more is the plastic limit. In the standard test, you roll a thread of soil until it crumbles at about 1/8 inch in diameter; the moisture content at that moment is the plastic limit—the lowest water content at which the soil remains plastic. The other terms refer to different boundaries: the liquid limit is the higher boundary where it becomes liquid, the plasticity index is the range between liquid and plastic limits, and the shrinkage limit is where further drying no longer reduces volume.