Sedimentary Rocks| Definition, Formation, Examples, & Characteristics

Sedimentary Rocks

What are sedimentary rocks?

Pre-existing rocks or pieces of once-living organisms are used to create sedimentary rocks. They’re made up of deposits that build up on the surface of the Earth. Layering or bedding in sedimentary rocks is frequently visible. Mesas and arches made of layered sedimentary rock appear in many of the scenic views of the desert southwest.

Common Sedimentary Rocks

Sandstone, limestone, and shale are examples of sedimentary rocks. These rocks are frequently formed from river sediments that are deposited in lakes and oceans. When sediments are buried, they lose water and become cemented, forming rock. Volcanic ash is found in tufffaceous sandstones.

Clastic Sedimentary Rocks

When most people think of sedimentary rocks, they picture clastic sedimentary rocks. Clastic sedimentary rocks are composed of pre-existing rock fragments (clasts).


Weathering loosens rock fragments, which are then transported to a basin or depression where sediment is trapped. Sedimentary rock is formed when sediment is buried deeply and compacted and cemented.

Clastic sedimentary rocks can contain particles as small as microscopic clay to as large as huge boulders. Their names are derived from the size of their clasts, or grains. Clay is the smallest grain, followed by silt, and finally sand.

Pebbles are grains with a diameter of more than 2 millimetres. Shale is primarily composed of clay, siltstone is composed of silt-sized grains, sandstone is composed of sand-sized clasts, and conglomerate is composed of pebbles encased in a sand or mud matrix.

Biologic Sedimentary Rocks

When a large number of living things die, biological sedimentary rocks form. This type of rock is known as chert, and it is one of the ways limestone can form. Limestone can also form as a result of water precipitation.

Uses of Sedimentary Rocks in Civil Engineering

Sedimentary rock can be found in almost all structures, both private and public. As a result, it is an extremely important building material in civil engineering projects.

Sedimentary rock is formed when mineral or organic particles settle and cement together on the bottom of oceans or other bodies of water. Sedimentary rock’s application in civil engineering is discussed.

Types of Sedimentary Rocks

Sedimentary rocks come in a variety of shapes and sizes. These are provided in order to discuss the various applications of sedimentary rocks based on their types.

  1. Clastic sedimentary rocks
    1. Conglomerates and breccias
    2. Sandstones includes Quartz , Feldspathic, Lithic, ”Clean” sandstones, Muddy sandstones
  2. Biochemical sedimentary rocks
    1. Limestone; corrals, mollusks, foraminifera, and coal
  3. Chemical sedimentary rocks
    1. Pyroclastic flows, impact breccias, and volcanic breccias

Uses of Sedimentary Rocks

Sedimentary rocks have a wide range of applications in civil engineering. The following are the most common uses for this type of rock:

Architectural and Monumental Stone

  • Certain types of sedimentary rock, such as Portland stone, can be used as architectural and monumental stones (a white -grey limestone).
  • It can withstand the effects of weathering well. More importantly, masons can easily cut and crave Portland stone, which is a significant advantage. As a result, it is regarded as one of the most popular architectural and monumental stones.
  • St. Paul’s Cathedral, Buckingham Palace, Westminster Palace, the British Museum, and the Bank of England were all built with Portland stone.

Structural Wall Construction

Sandstone and limestone are both suitable for building structural walls. Sandstone, on the other hand, must be carefully considered because it may be excessively porous and fragile for load-bearing structures.

Concrete Production

To withstand pressure, sedimentary rock is used as aggregate in concrete production.

Pavement and Road Construction

  • Pavement and road stone have traditionally been made of sandstone and limestone.
  • In road construction, shale is used as an aggregate.
  • The highway roadbed is made of sedimentary rocks.

Brick and Tile Manufacturing

Shale is used in the construction of bricks and tiles as one of the materials.

Building Interior Decoration

Marble is recrystallized and then used to decorate the interiors of buildings. It’s also used to make statues, table tops, and decorative objects.

Cement Production

  • Limestone is the primary raw material used to make Portland cement.
  • Cement manufacturers use shale as a raw material.

Filler in Paint

Shale is a sedimentary rock that can be used as a filler in a variety of paints.

Sheetrock and Plaster

Sheetrock and plaster use gypsum as a major component.


  • Sandstone, particularly thick bedded, well cemented, and siliceous or ferruginous sandstone, is an excellent choice for tunnelling.
  • It’s sturdy and simple to work with.
  • There is no need for lining.
  • Sandstone has no negative impact on geological structures or ground conditions.
  • Because of the softness of shale, tunnelling is relatively easy, but proper lining must be provided.
About the Author
Er. Mukesh Kumar
Er. Mukesh Kumar is Editor in Chief and Co-Funder at Civil Engineering Website. Mukesh Kumar is a Bachelor in Civil Engineering From MIT. He has work experience in Highway Construction, Bridge Construction, Railway Steel Girder work, Under box culvert construction, Retaining wall construction. He was a lecturer in a Engineering college for more than 6 years.