Stones are naturally available building materials that have been used since early civilization. Type of stones used in civil/ building construction works are igneous, sedimentary or metamorphic in origin. Stones required for building/civil engineering construction must be strong, durable, hard, tough,  and cost effective.

Uses of stones in building/civil engineering construction

• For construction of foundations, walls, columns and arches
• For flooring and damp proof courses
• Facework of buildings, paving of roads and base courses
• Abutment and bridges, dams and retaining walls
• Common building stones

The following are some commonly used building stones

Basalt:

An igneous rock. Colour varies from dark grey to black. Used in road construction and as aggregates for making concrete.

Granite:

An igneous rock. Crystalline in structure. Particles sizes ranges from fine to coarse grained. They are used for dams, river walls and bridge piers. Also used as coarse aggregates in concrete.

Sandstone:

Sand-stones are stratified rocks consisting of quartz and feldspar. They come in many colours including white, grey, red, yellow, brown and dark grey. Sandstone is not as strong as granite and balsalt. They are used for masonry work, dams, bridge piers and river walls.

Slates:

Slates are metamorphic rocks composed of quarz, mica and clay. Their colour varies from dark grey to black. They are used for roofing tiles, pavements etc.

Laterite:

This is also a type of metamorphic rock with porous structure. Its colour varies, i.e. brown, red, yellow, grey etc.  laterite is commonly used as filling material.

Marble.

Another type of metamorphic rock. Marble is available in different colours such as pink and white. Used for facing and ornamental works.

Plain concrete is known as concrete without steel reinforcement. It is an intimate mixture of cement, fine aggregates, coarse aggregates and water. It can be easily molded to desired shape and size before it hardens. Plain concrete is strong in compression but weak in tension.

Major ingredients of plain concrete are;

• Binding materials such as cement, lime, polymer.
• Fine aggregate material such as sand.
• Coarse aggregate materials like crushed stone, gravel, and granite.
• Clean water.

Common cement, sand and coarse aggregate ratios are;

1:1:2, 1:2:4, 1:3:6, 1:4:8

Constituents of plain concrete.

Cement:

Cement is the binding material. It binds and hardens when water is added. Generally a concrete mix with more cement gives more strength.

Coarse aggregate:

Coarse aggregates consists of crushed stones of igneous origin. They should be clean, hard, angular and sharp. They give mass to the concrete and prevent shrinkage of cement.

Fine aggregates:

River sand is the common fine aggregate for plain concrete. Its gives mass to concrete and fills voids created by coarse aggregates.it adds density to concrete. A denser concrete is higher in strength.

Water:

Water used for making concrete should be clean. It hydrates the cement to form a plastic mass which hardens gradually. Water makes it possible to mix the concrete with ease and place it in final position. The more water the better, however, excess water reduces the strength of concrete. A water – cement ratio of 0.5-0.6 is used to achieve desired concrete strength when hand mixed.

Preparing and placing of concrete.

Batching:

Batching by volume or weight are the 2 common methods of measurement.

Mixing: 

Thorough mixing to produce good quality concrete. Cement, sand and coarse aggregates is mixed in dry condition, then in wet condition after adding water. Hand and machine mixing are 2 common methods of mixing of concrete mixing

Transport and placing:

Fresh concrete is transported on site using head pans, wheel barrow on small scale work while concreting chutes, bell conveyors or pumps are used in large scale construction.

Compaction:

Compaction of concrete is necessary to remove entrapped air during placement of concrete. Compaction can be carried out by hand or with help of  concrete vibrators