What is the defining property of the material known as asphalt?

The defining property of asphalt is that it is a dark brown to black cementitious material. This characteristic is crucial because it highlights asphalt's composition and appearance, which directly relate to its functionality in various applications, particularly in paving and roofing. Asphalt is primarily made from bitumen, a viscous, sticky liquid derived from the distillation of crude oil, contributing to its dark color and viscous nature.

In civil engineering and materials science, understanding the properties of asphalt is vital since its physical behavior—such as elasticity, ductility, and stability under different temperature conditions—affects how it performs as a binding agent in mixtures like asphalt concrete. This enables its widespread use in road construction and industry, where the properties of the material must meet specific performance and durability criteria.