This document provides information about pavement materials engineering. It discusses the relationships between different phases in soil, including solid particles, water, and air. Key terms discussed include density, unit weight, specific gravity, voids ratio, porosity, degree of saturation, bulk unit weight, dry unit weight, and saturated unit weight. Examples are provided to demonstrate how to calculate volumes, weights, moisture content, and other properties for soil samples. Relationships between these various properties are also examined.