No single stone can meet all of the quality requirements listed below. For example, the need for strength and durability is in contrast to the ease of dressing requirement. It is therefore essential that the site engineer looks at the properties required for the intended job and selects the stone accordingly.

Following are the quality requirements of good building stones:

1. Strength

Generally most of the building stones have high strength to resist the load coming on it. So it is not a major concern when it comes to checking the quality of stones. But when stones are used in large structures, it becomes necessary to check the compressive strength of stones.

The compressive strength of building stones generally falls in the range of 60 to 200N/mm2.

2. Tolerance

Building stones should be able to resist the adverse effects of natural forces such as wind, rain and heat. It should be durable and should not deteriorate due to the adverse effects of the above natural forces.

3. hardness

When stones are used in the aprons of floors, sidewalks or bridges, they become subject to wear and friction forces due to the movement of men or machines on them. Therefore it is necessary to test the hardness of the stone.

The hardness of a stone is determined by the Mohs scale.

4. toughness

The hardness of stones means the ability to resist impact forces. Forming stones must be hard enough to sustain the stress developed due to vibration. Vibrations can be caused by machinery mounted on them or by increased load on them. The aggregates of stone used in road construction should be hard.

5. specific gravity

The higher the specific gravity of the stone, the heavier and stronger the stone.

Therefore stones with high specific gravity values ​​should be used for construction of dams, retaining walls, docks and harbors. The specific gravity of a good building stone is between 2.4 and 2.8.

6. porosity and absorption

The porosity of stone formation depends on the mineral component and structural formation of the parent rock. If the stones used in building construction are porous then rain water can easily enter the pores and damage the stones. Therefore the stone of the building should not be porous.

The water absorption of a stone is directly proportional to the porosity of the rock. If a stone is more porous it will absorb more water and cause more damage to the stone.

At higher altitudes, water freezes in the pores and results in dissolution of the stone.

The permissible limits of water absorption for some commonly used stones are as follows.

stone type Maximum limit of water absorption (%)
sandstone 10
Limestone 10
granite 1
shale 10
slate 1
quartzite 3

7. dressing

Giving the stone the required shape is called dressing. The clothes should be easy to wear so that the cost of dressing is low. However, care should be taken that this is not at the cost of required strength and durability.

8. appearance

In the case of stones used for face work, where appearance is a primary requirement, its color and ability to achieve polish is an important factor.

Light colored stones are preferred over dark colored stones as there is a possibility of discoloration of the color over time.

9. Spices

Good stones should be free from quarry juice. Lateritic stones should not be used for 6 to 12 months after excavation. They are allowed to get rid of mine sap by the action of nature. This process of removing the juice from the mine is called seasoning.

10. feasibility

The stone must be workable. Stone is said to be workable when the work involved in stone working (such as cutting, dressing and shaping) is economical and easy to operate.

1 1 Cost

Cost is an important consideration in the selection of building materials. The proximity of the mine to the construction site reduces the cost of transportation and hence the cost of stones.

12. Retardant

The stones must be free of calcium carbonate, iron oxide and minerals, which have different coefficients of thermal expansion. Igneous rock shows dissolution mainly due to quartz which decomposes into smaller particles at a temperature of about 575 °C. Limestone, however, can withstand slightly higher temperatures; That is, up to 800 ° C, after which they disintegrate.

Er. Mukesh Kumar

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Er. Mukesh Kumar is Editor in Chief and Co-Funder at ProCivilEngineer.com Civil Engineering Website. Mukesh Kumar is a Bachelor in Civil Engineering From MIT. He has work experience in Highway Construction, Bridge Construction, Railway Steel Girder work, Under box culvert construction, Retaining wall construction. He was a lecturer in a Engineering college for more than 6 years.