Limestone Vs. Crushed Concrete

Builders use numerous types of stone and aggregate materials in projects ranging from basement walls and home foundations to roads and bridges. Crushed concrete and limestone constitute two of these materials. Understanding the differences between the two requires examining the interconnectedness between them as they maintain a complex relationship. Though they ultimately qualify as different material types, the two can occur simultaneously.

The Ancient Romans invented concrete, which at the time consisted of a mixture of volcanic sand, water and a rudimentary form of cement composed of small stones, lime mortar and water. In its wet, claylike form, concrete assumes the shape of any mold you pour it into. When it hardens, it forms a strong stone surface. Numerous types of modern concrete exist, including those made from natural cement and Portland cement, both of which contain ground limestone as a primary ingredient.

Limestone is any type of rock composed primarily – 50 percent or more by weight – of calcium carbonate. It forms largely in aquatic environments by the accumulation of debris from shells, algae, coral and the fecal matter of marine animals. Types of limestone include chalk, coquina, tufa and travertine. Limestone contains few pores, making it strong and an attractive material for the construction industry. Powdered limestone appears in paper, paint, rubber and plastic. It also appears as one of the minerals commonly found in marble.

Crushed concrete is exactly what it sounds, concrete ground into small pieces. After significant aging and use, concrete loses its value due to cracking, weakening and other problems. Companies acquire old concrete, crush it into small pieces and reuse it in numerous applications. Also called recycled concrete, it has many uses including bedding material for pipes and drainage systems, compositional material for stone embankments and surface material for temporary or dirt roads and sidewalks. It also appears as a mixing material in new concrete. The Texas Department of Transportation builds some roads entirely from recycled concrete.

In its pure form, limestone differs significantly from crushed concrete in that the former constitutes a naturally formed rock found in marine environments and the other a manmade construction material. Limestone may appear in crushed concrete as a material found in the cement used to mix concrete. Some builders use crushed concrete as a material for new concrete, in which it takes the place of a crushed mixing stone like limestone. Crushed limestone appears in some of the same applications as crushed concrete.