Stones

Bahram Nawabi 2012UCE1790

2nd Year 1st Sem

Construction Materials “ST211”

Contents:• Stones• - Rocks• - Quarrying of stones• - Uses of stones (1-2)• - Characteristic of good building stones

• Tests of stones• - Different types of stones tests• - Why should we test and …• Preservation of stones

STONES

Stone has been defined as the natural, hard substance formed from minerals and earth material

which are present in rocks.

Rocks

Rock may be defined as the portion of the earth’s crust having no definite

shape and structure.

Quarrying of stones

The only operation involved in the production of natural stone is the

quarrying process.

The open part of the natural rock from which useful stone is

obtained is known as quarry.

Uses of stones-1

Use of stone as building material depends upon the:Nature of the work Type of the structural elementQualityAvailability Transportation cost

Uses of stones-2For structural purposes:

Granite

Gneiss

Trap

Sandstone

Limestone

Marble

Quartzite

Slate

are most useful.

Valley National Bank building, Arizona

B.L. Stone Building, Portland

Characteristics of good building stonesA good building stone should have:

Appearance

Structure strength

Weight

Hardness

Toughness

Seasoning

Weathering

Workability

Fire resistance

Specific gravity

Thermal movement

Testing of stones

To choose and utilize stones and for their satisfactory performance, it is necessary to test them for its strength properties, durability and quality.

Different types of test• Acid test

• Attrition test

• Absorption test

• Brad’s test

• Crushing strength test

• Crystallization test

• Freezing and thawing test

• Hardness test

• Impact test

• Microscopic test

• Smith’s test

• Specific gravity test

• Durability test

• Acid test:This test is carried out on stone to

check the weathering resistance.

• Attrition test:The aim of this test is to determine the resistance

of the stone to abrasion, specially for those stones which are to be used for path ways, pavements and roads subjected to the grinding action of the traffic.

percent wear=(M1-M2)/M1*100

Where;

M1= Initial mass of stone ballast.

M2= Final mass of stone ballast

Deval’s Attriton Machine;

• Water absorption test:

The water absorption test is carried out to determine the quality of stone.

% Absorption= (M1-M2)/M1*100

• Brad’s test:

This test is conducted for frost resistance.

• Crushing strength test:

This test is conducted on a compression testing machine.

The test samples are dressed from all sides. The diameter of the test pieces known as specimen, is not less than 40 mm.

• Hardness test:

The hardness test is conducted on Dory's testing machine.

Coefficient of hardness= 20-loss of mass in gm/3

Alternatively the hardness test may be performed by scratching the stone with a knife on Mohr’s scale.

• Impact test:

Is carried out on an impact machine to determine the toughness of stone.

• Microscopic examination:

This is basically a geologists test. Thin sections of stone are taken and placed under a microscope to study the following properties:

i. Average grain size

ii. Texture of the stone

iii. Mineral constituents

iv. Type of cementing material

v. Presence of pores, fissures, veins, shakes etc.

vi. Presence of harmful constituents

vii. Condition of fractured surfaces.

• Smith’s test:

This test is conducted to find out the presence of water soluble matter present in the stone. It is only a qualitative test.

• Weathering resistance (Crystallization)test:

This test is conducted as per Indian Standard Specific

a1= 100*(M3-M1)/M1

V1= (M3-M2)/µ

a2= 100*(M4-M1)/M1

V2= (M4-M5)/µ

Where;a1= original absorption of the specimen at the end of 24

hr immersion

a2= final absorption of the specimen after 30 cycles

V1= original volume of the specimen at the end of 24 hr immersion

V2= final volume of the specimen after 30 cycles of test

µ= density of water

a1= 100*(M3-M1)/M1

V1= (M3-M2)/µ

a2= 100*(M4-M1)/M1

V2= (M4-M5)/µ

Where;a1= original absorption of the specimen at the end of

24 hr immersion

a2= final absorption of the specimen after 30 cycles

V1= original volume of the specimen at the end of 24 hr immersion

V2= final volume of the specimen after 30 cycles of test

µ= density of water

Increase in absorption due to weathering= 100*(a2-

a1)/a1

• Specific gravity test:

This procedure is adopted for determination of specific gravity of stone, as per IS : 1121-1974

Gt=(M2-M1)/((M4-M2)-M3-M2)

• Durability test:

The durability (soundness) test is performed to find out the capacity of stone to resist disintegration and decomposition.

Durability value= change in the mass= (M1-M2)*100

Why should we test and which tests are appropriate?• • Failure mode effect analysis

• – What can go wrong?

• – What can we test for this?

• – How can we manage the risk?

• • Is it safe?

• • Will it last?

• • Is it strong enough?

Different types of test -flexural

Different types of test -flexural

Different types of test - compressive

Different types of test – porosity

Different types of test – slip

Different types of test – salt

Preservation of stonesThe various natural agents, Like:• Rain• - Physical action• - Chemical action• Frost• Wind• Temperature changes• Vegetable growth• Mutual decay• Chemical agents• Lichensare deteriorate the stones with time.

Due to preventing from these deteriorations on stones there are some preservations.

1) Coal tar:

If coal tar is applied on stone surface, it preserves stone.

But the colour of coal tar produces objectionable appearance and surface coated with coal tar absorbs heat of the sun. Hence this preservative is not generally adopted because it spoils the beauty of stones.

2) Linseed oil:This preservative may be used either as raw

linseed oil or boiled linseed oil. The raw linseed oil does not disturb the original shade of stone. But it requires frequent renewal usually one in a year. The boiled linseed oil lasts for along period, but it makes the stone surface dark.

3) Paint:

An application of paint on stone surface serves as a preservative. The paint changes the original colour of stone. It is applied under pressure, if deep penetration is required.

4) Paraffin:

This preservative may be used alone or it may be dissolved and naphtha and then applied on stone surface. It changes the original colour of stone.

5) Solution of alum and soap:

The alum and soft soap are taken in proportion of about 0.75N and 0.50N respectively and they are dissolved in a liter of water. This solution, when applied on stone surface, acts as preservative.

6) Solution of baryta:

A solution of barium hydroxide Ba(OH)2, when applied on stone surface, acts as a preservative. This preservative is used when the decay of stone is mainly due to calcium sulphate, CaSO4. Following chemical reaction takes place:

Ba(OH)2+CaSO4 = BaSO4+Ca(OH)2

The barium sulphate is insoluble and it is least affected by atmospheric agencies. The calcium hydroxide absorbs Carbon-di-Oxide from atmosphere and forms Calcium Carbonate CaCO3 which adds to the strength of stone.

Sources

1. ) Engineering materials, By Rangwala.

2. ) Basic Civil Engineering, By Dr.B.C. Punmia

3. ) Internet, (Wikipedia.com, Google image)