Limestone's most common use is as a crushed construction material, serving as a base for roads and ballast in railroads, but it also combines with crushed shale in a kiln to make cement and serves as an aggregate material in concrete. Limestone's usefulness stems from its strength and density.
Limestone also is used as roofing granules, a coating that helps shingles resist the heat and weathering. Floor tiles, window sills, facing stone and stair treads are commonly made from limestone blocks. Crushing limestone to the size of sand particles creates a useful material for reducing soil acidity.
Some animal feed manufacturers include limestone as a filler because chickens require calcium carbonate (found in limestone) to make sturdy egg shells. Dairy cattle also receive limestone as a feed filler when the milking process causes them to have a calcium deficiency. Finally, pulverized limestone makes an effective safety dust in mines. Spraying it onto coal surfaces in a mine increases the amount of light and cuts down on coal dust.
Limestone's sturdiness makes it hold up through the cycling between freezing and thawing, as well as to other forms of abrasion. Limestone is easier to mine and causes less damage to mining equipment and transport vehicles than harder silicates.