Characteristics OF GOOD Building Stone PDF

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Lecture Notes in Construction Materials CHARACTERISTICS OF GOOD BUILDING STONE A good building stone should have the following qualities: • • • • • • • • •

• • •

Appearance Structure Strength Weight Hardness Toughness Seasoning Weathering Porosity and Absorption No.

Type of Stone

H2O Absorption

1

Sandstone

10

2

Limestone

10

3

Granite

1

4

Trap

6

5

Shale

10

6

Gneiss

1

7

Slate

1

8

Quartzite

3

Workability Fire Resistance Thermal Movement

TESTING OF STONES Durability Test It is performed to find out the capacity of stone to resist disintegration and decomposition.

•

Smith Test

•

Brard's Test

•

Acid Test

•

Crystallisation Test

Change in weight ¿

W 1−W 2 W1

Crushing Test Compressive Strength Test- to test stone for compressive strength, specimen pieces in the form of cubes or cylinders are made from samples of rock.

CP

C c=

0.778 + 0.222

( bh )

Where: Cc = compressive strength of standard specimen piece Cp = compressive strength of the specimen having a height greater than the diameter or lateral dimension b = diameter or lateral dimension h = height Transverse Strength Test To test stone for transverse strength, specimen pieces are made in the form of blocks 200x50x50 mm. R = transverse strength in N/mm2 W = central breaking load in N L = length of span in mm b = ave. width in mm of the test piece at the mid-section d = ave. depth in mm of the test piece at the mid-section

Tensile Strength Three cylindrical test pieces of diameter not less than 50mm and the ratio of diameter to height 1:2 are used to determine the tensile strength of the stone in each saturated (kept in water for 3 days at 20-30°) and dry condition (dried in an oven at 105 ± 50 C for 24 hours and cooled at room temperature).

S=

2W πdL

Where: S = split tensile strength (N/mm2) W = applied load (N) d = diameter of specimen (mm) L = length of specimen (mm) Shear Strength Test Test piece for use in Jhonson shear tool should be bars 50x50mm in section and not less than 100mm in length and for use of Dutton punching shear device should be slabs 30mm thickness, 100mm in width and not less than 100mm in length. Using Jhonson Shear Tool:

S=

W 2A

Where: S = Shear strength (N/mm2) W = total maximum load (N) A = area of the center cross-section of test piece (mm2) Using Dutton Punching Shear Device:

S=

W t −W i π DT

Where:

S

= Shear strength (N/mm2)

W t = total maximum load (N) W i = initial load (N) required to bring the plunger in contact with the surface of specimen D = diameter (mm) of the plunger T = thickness (mm) of the specimen Absorption Test

The selected test pieces of stone are crushed or broken and the material passing 20mm IS Sieve and retained on 10mm IS Sieve is used for the test.

DETERIORATION OF STONES The various natural agents such as rain, heat, etc. and chemicals deteriorate the stones with time. • • • • • • • •

Rain Frost Wind Temperature Changes Vegetable Growth Mutual Decay Chemical Agents Lichens

DURABILITY OF STONES Stone from top ledges of limestone, granite and slate and from the exposed faces of the rock bed is likely to be less hard and durable. Highly absorbent stone should not be quarried in freezing weather since the rock is likely to split. A porous stone is less durable than a dense stone, since the former is less resistant to freezing.

PRESERVATION OF STONES Due to preventing from these deteriorations on stones, there are some preservations. • • • • • •

Coal Tar Linseed oil Paint Paraffin Solution of Alum and Soap Solution of Baryta

SELECTION OF STONE The conditions which govern the selection of stone for structural purposes are cost, fashion, ornamental value and durability, although the latter property is frequently overlooked or disregarded. Colour- arrangement and shape of mineral constituents greatly influence fashion and ornamental value. One of the first factors influencing the selection of stone for a particular work will be colour.

Resistance to fire and weathering- factors which are largely influenced by the mineral constitution of the rock- are the most important determinators of durability. It is very important to select a stone according to its exposure conditions.

ARTIFICIAL STONES Artificial stone It is made with cement and natural aggregates of the crushed stone and sand with desired surface finish. Suitable coloring pigments may be added. • • • • • •

Concrete Block Ransom Stone Victoria Stone Imperial Stone Artificial Marble Garlic Stone

APPLICATION OF STONES Of the total amount of stone quarried for the building industry, about 75 per cent are used directly for concrete constructions and road making, the balance finds applications in the manufacture of cement and other binding materials, in the chemical industry, as metallurgical fluxes, and for making wall from natural stones. 1. Natural stones materials, possessing high resistance to atmospheric agents, high mechanical strength and pleasant colours are widely used in construction as slabs for walls and foundations of buildings and installations. 2. Foundations and walls of underground parts of buildings are made from quarry, split and sawn stones from igneous, sedimentary and metamorphic rocks. 3. Slabs for floors and facing of walls are rectangular, their dimensions depending on the kind of rock and the face finish. 4. Facing slabs and stones, parts of stairs and landings, parapets and guard rails are made of slabs sawn or split form natural stone and worked by mechanical means. 5. Pedestal slabs and stones for framing doorways, belts of cornices, corner and windowsill slabs fall into the category of profile wall facing elements. 6. The materials and items from natural stones used in road construction are curbstones, paving blocks, bewn stone or cobblestone, crushed stone, sand and mineral powder. 7. Underground structures and bridges are built of slabs and stones form igneous and sedimentary rocks, tunnels and above-water parts of bridges are built of granite, diorite, gabbro, diabase and basalt with compressive strengths not less than 100 MPa.

8.

Hydraulic structures are generally built with natural stones or regular or irregular shape (hewn, rolled, cut, sawn, and also crushed stone) from igneous, metamorphic or sedimentary rocks.

9.

Crushed stone and sand is used for preparing mortars and concretes, for making roadbeds and drainage constructions....