Which type of soil is known to expand the most?

The type of soil known to expand the most is clay. Clay has unique properties that cause it to swell when moisture is added and shrink when it dries out. This characteristic is due to the structure of clay particles, which are small and have a large surface area that holds water. When water is absorbed, the particles repel each other, leading to expansion. This is especially significant in construction, as expansive clay can negatively impact foundations and structures if not properly managed.

In contrast, sand is a coarse soil that tends to drain quickly and does not expand or contract significantly with changes in moisture. Loam, which is a mixture of sand, silt, and clay, provides good drainage and has a balanced texture that makes it stable and not prone to excessive swelling. Stone, particularly blast rock, is a solid material that does not exhibit expansion characteristics associated with soil. Therefore, while clay is the correct answer due to its significant expansion and contraction behavior, the other options do not possess these properties.