Stone As a Building

Material

Stone:

a natural, hard substance formed from minerals and earth material which are present in rocks.

Rocks:

the portion of the earth’s crust having no definite shape and structure.

Classification of Rocks(Stones)Chemical classification: Argillaceous Rocks:

Argillaceous or clay stones are those stones which contain (alumina Al2O3) (clay) as principal constituent. These stones are less durable stones. Eg. Clay.

Silicious Rocks:The stones which contain (Silica SiO2) as principal constituent are called silicious rocks. These stones are durable stones. Eg Granite Sandstone etc.

Calcareous Rocks: The stones which contain calcareous material

(CaCO3) as principal constituent are called calcareous rocks. Eg Marble Stone, Lime Stone.

PHYSICAL CLASSIFICATION:Stratified Rocks: The rocks which are split into thin slabs or layers easily are called stratified rocks. Eg Slate,Sand Stone.

Unstratified Rocks: These rocks do not show sign of stratification and can not be easily split into thin slabs or layers are called unstratified rocks. Eg Basalt, Granite.

GEOLOGICAL CLASSIFICATION: Igneous or Primary Rocks: These are primary rocks which are formed

from molten magma. They represent different structural features depending upon the condition of solidification and composition Eg. basalt, trap

Sedimentary or Secondary Rocks: These are secondary rocks and are formed by

the denudation and deposition of previously existing rocks due to weathering actions.

Metamorphic or Tertiary Rocks: Rocks which are formed due to metamorphic

action of pressure or internal heat or by both (or) alteration of original structure due to heat and excessive. Eg. Marble.

To qualify as a construction material, stone should have the

following qualities:

Strength: It is power of stone to

sustain pressure or resistance to crushing force.Average crushing strength of stone is 3 tons per square inch. Most types of stone have more than adequate compressive strength. The shear strength of stone, however, is usually about 1/10 of its compressive strength.

Hardness: Hardness denotes several qualities of stones such as resistance to cutting and resistance to abrasion Hardness is important when stone is used for flooring, paving, and stair treads.

Durability: Resistance to the

weathering effects of rain, wind, heat, and frost action is necessary for exterior stonework. It depends upon:Chemical composition,Physical structure,Resistance to weathering effects,Place where it is used

Workability: A stone’s hardness

and grain texture must allow it to be quarried, cut and shaped.

Appearance: Appearance factors include color, grain, and texture. Highly colorful stones are preferred for architectural purpose but those are soft and thus less durable. Therefore, lighter stones are preferred than to darker ones.

Fire resistance:A good building stone should be fire resistant. Some stones such as basalt and trap resist fire very well but some varieties of igneous and metamorphic stones are very weak against fire.

It is used in foundations of buildings.It is used in construction of dams, barrages, etcIn its crushed (powdered form) it is used as artificial sand.It is used as raw material for manufacturing of cement.It is used as decorative material in buildings.It is also used as parts of buildings such as lintels and arches, etcIt is also used as thin slabs for building roofing.It is also used for ornamental works in buildings.In its broken form it is in the manufacturing of concrete.

Uses of Stone

Limitation of Stones1. Dressing of stones is tedious,

laborious and time consuming job.2. Desired strength and quality not

available at moderate rates especially in plain areas.

3. RCC, Steel are alternatives to stones and gives more strength and flexibility.

4. Stone structure design can’t give freeness and flexibility to the designer.

Deterioration of stones:

1. Alternate wetness and drying.

2. Frost.3. Impurities in

atmosphere.4. Living

organisms.5. Nature of mortar.6. Rain water.7. Temperature

variations.8. Vegetable

growth.

Stone MasonryThe construction of stones bonded together

with mortar is termed as stone masonry where the stones are available in a abundance in nature, on cutting and dressing to the proper shape.

• Rubble masonry:

Uncoursed rubble masonry:This is the cheapest, roughest and poorest form of stone masonry. The stones used in this type of masonry very much vary in their shape and size and are directly obtained from quarry. Uncoursed rubble masonry can be divided into the following.

a) Uncoursed random rubbleb) Uncoursed squared rubble

Uncoursed rubble masonry

a) Uncoursed random rubble masonry: The

weak corners and edges are removed with

mason’s hammer. Generally, bigger stone

blocks are employed at quoins and jambs to

increase the strength of masonry.

b) Uncoursed squared rubble:

In this type the stone blocks are made roughly square with hammer. Generally the facing stones are given hammer-dressed finish. Large stones are used as quoins. As far as possible the use of chips in bedding is avoided.

Uncoursed rubble masonry

Regular Course

Built to regular course: In this type of stone masonry the uniform height stones are used in horizontal layers not less than 13cm in height. Generally, the stone beds are hammered or chisel dressed to a depth of at least 10cm from the face. The stones are arranged in such a manner so that the vertical joints of two consecutive curse do not coincide with each other as shown in figure below.

Polygonal rubble masonry: In this type of masonry the stones are roughly dressed to an irregular polygonal shape. The stones should be so arranged as to avoid long vertical joints in face work and to break joints as much as possible. Small stone chips should not be used to support the stones on the facing as shown in the figure below.

Flint rubble masonryFlint rubble masonry: This type of masonry

is used in the areas where the flint is available in plenty.

The flint stones varying in thickness from 8 to 15cm and in length from 15 to 30cm are arranged in the facing in the form of coursed or uncoursed masonry as shown below.

Ashlar fine Ashlar rough

Ashlar Masonry

Ashlar facing Ashlar chamfered

Ashlar Masonry

SILLS

Stone SILL

Sloped Outer REVEAL