Characteristics of good building stones:-
3(S)TRAP 2(HD)
Strength:
Must be good in compression stress. Closed-grained and uniform textured stones are generally good in compressive strength.
Structure:
A good stone if broken in the direction of cleavage should not give a dull appearance. These should be either closed-grained or crystalline and show uniformity of texture. Stones should be free from cavities and cracks. If the stones are obtained from sedimentary rocks, their stratification should not be visible to the naked eye.
Seasoning:
The stone should be free from quarry sap. The stones after quarrying and dressing should be left for at least for 6-12 months before being used for construction.
Toughness:
Should be tough enough to withstand the stress developed due to the vibration of pieces of machinery and moving loads.
Resistance to fire:
Should be able to resist high temperatures. Should not have minerals that are decomposable under heating such as calcium carbonate and iron oxide. Also, stones should not be composed of minerals with different coefficient of thermal expansion. Quartz expands at low temperatures, and an argillaceous variety of stones resist high temperatures.
Appearance:
The stones used in construction should be of uniform colour, lighter colours are more favourable than darker ones as the latter are less durable. Also, stones should be able to receive good polish.
Porosity and absorption:
They should not be porous and should not absorb water when immersed. Porous stones are unsuitable for construction work as rainwater may be absorbed through chemical reactions with minerals and possibly weather. In cold climatic regions, water may ingress into the pores and freeze leading to the disintegration of stones.
Hardness:
A good stone depending upon its site of implementation should possess enough abrasive resistance. The hardness of a stone is tested by Mohr’s scale of hardness however in the field it can be tested by knife scratching. Hard stones do not show any mark of scratching.
Heaviness:
The stones used in the construction of dams, weirs, barrages, and docks should be of heavy varieties. The stones used for roof coverings should be lighter. A stone should have a specific gravity between 2.4 and 2.8.
Durability:
Good stones should resist the action of the atmosphere such as wind, rain and temperature. Durable stones are compact and crystalline in structure.
Dressing:
The stone used in making statue structures should be good enough to be converted into a certain shape. Marble is one of the examples but it should be noted that these stones are weak and less durable.
Suitability of Stones for Various Types of Construction:-
S.N.
|
Type of structure
|
Type of stone
|
1
|
Piers, bridge abutments, light houses, and wires.
|
Good quality granite, good or stratified granite.
|
2
|
Road Pavements and railway ballast
|
Inferior quality of granite and Gneiss.
|
3
|
Road metalling, Paving
|
Basalt and Trap.
|
4
|
Cement concrete
|
Basalt and Trap.
|
5
|
Ornamental work in building
|
Red and yellow types of basalt and trap.
|
6
|
Roof Covering and Flooring
|
Slate
|
7
|
Damp proofing and sills of windows
|
Slate
|
8
|
Partitions in urinals and bath rooms
|
Slate
|
9
|
Monuments, Statues and carved work
|
Marble
|
10
|
Building Construction
|
Laterite
|
11
|
Interior decoration in superior buildings
|
Serpentine
|
Stones
|
Specific gravity
|
Crushing strength(kg/cm2)
|
Granite
|
2.63-2.65
|
1000-1400
|
Basalt
|
3.00
|
700-850
|
Sandstone
|
2.3-2.6
|
400-650
|
Limestone
|
2.3-2.4
|
400-650
|
Marble
|
2.72
|
500-600
|
Slate
|
2.89
|
750-2100
|
Quartz
|
2.65
|
750
|
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