STONES
Stone is a ‘naturally available
building material’ which has been used from the early age of civilization.
It is available in the form of rocks, which is cut to
required size and shape and used as building block. It has been used to
construct small residential buildings to large palaces and temples all over the
world. Red Fort, Taj Mahal, Vidhan Sabha at Bangalore and several palaces of
medieval age all over India are the famous stone buildings.
Type
of Stones
Stones used for civil engineering
works may be classified in the following three ways:
• Geological
• Physical
• Chemical
Geological Classification
Based on their origin of
formation stones are classified into three main groups—Igneous, sedimentary and
metamorphic rocks.
(i) Igneous
Rocks: These rocks are formed by cooling and solidifying of the rock masses
from their molten magmatic condition of the material of the earth. Generally
igneous rocks are strong and durable. Granite, trap and basalt are the rocks
belonging to this category, Granites are formed by slow cooling of the lava
under thick cover on the top. Hence they have crystalline surface. The
cooling of lava at the top surface of
earth results into non-crystalline and glassy texture. Trap and basalt
belong to this category.
(ii) Sedimentary
Rocks: Due to weathering action of water, wind and frost existing rocks
disintegrates. The disintegrated material is carried by wind and water; the
water being most powerful medium. Flowing water deposits its suspended
materials at some points of obstacles to its flow. These deposited layers of
materials get consolidated under pressure and by heat. Chemical agents also
contribute to the cementing of the deposits. The rocks thus formed are more
uniform, fine grained and compact in their nature. They represent a bedded or
stratified structure in general. Sand stones, lime stones, mud stones etc.
belong to this class of rock.
(iii) Metamorphic Rocks:
Previously formed igneous and sedimentary rocks under go changes due to
metamorphic action of pressure and internal heat. For example due to
metamorphic action granite becomes greisses, trap and basalt change to schist
and laterite, lime stone changes to marble, sand stone becomes quartzite and
mud stone becomes slate.
