Strength, Dressing, ROUGHNESS, Porosity and Absorption, Hardness, Seasoning, Durability, Fire Resistance, Specific Gravity
Almost all natural building stones are having good strength value. Also normally stones are used for decorative cladding and non load bearing structures e.g. compound wall. Hence strength property is not major concern unless the stone is used to withstand loads such as road pavement, load bearing walls, bridge piers etc. The values of strength of building stones varies from 60 – 2000 N/mm2
Giving required shape to the stone is known dressing. It should be simple to dress so that the cost of dressing is reduced. Yet the care should be taken so that, It is not be at the cost of the required strength and the durability.
Building stones should be tough sufficient to sustain stresses developed due to vibrations. The vibrations can be raised due to the machinery mounted over them or loads moving over them.Stone aggregates used in the road constructions should be tough.
Porosity and Absorption
Porosity of building stones depend upon the mineral constituent and structural formation of the parent rock. If stones used in building construction are porous then rain water can easily enter into the pore spaces and cause damage to the stones. Therefore building stone should not be porous.Water absorption of stone is directly proportional to the porosity of rock. If a stone is more porous then it will absorb more water and cause more damage to stone.In higher altitudes, the freezing of water in pores takes place and it results into the disintegration of the stone.
When stones are used in floors, pavements or aprons of bridges, they become subjected to wearing and abrasive forces caused by movement of men or machine over them. Hardness test should be done when stones are used in flooring, pavement etc. Mohs scale is used to determine hardness of stone.
Good stones should be free from the quarry sap. Lateritic stones should not be used for 6 to 12 months after quarrying. They are allowed to get rid of quarry sap by the action of nature. This process of removing quarry sap is called seasoning.
Building stones should be capable to resist the adverse effects of natural forces like wind, rain and heat. It must be durable and should not deteriorate due to the adverse effects of the above natural forces.
Stones should be free from calcium carbonate, oxides of iron, and minerals having different coefficients of thermal expansion. Igneous rock show marked disintegration principally because of quartz which disintegrates into small particles at a temperature of about 575°C. Limestone, however, can withstand a little higher temperature; i.e. up to 800°C after which they disintegrate.
The stone is more stronger and heavier with increasing value of specific gravity. Therefore for the construction of heavy structures such as dams, docks, bridges the stones having higher specific gravity should be used.