Materials of Construction-Building Stones 1

BUILDING STONES

Chapter 4

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Materials of Construction-Building Stones 2

What is Stone?

Stone is a concretion of mineral matter.

Used either as a;

Construction material,

Manufacture of other construction materials.

Stone has high strength, durability and nice

appearance.

Materials of Construction-Building Stones 3

Uses in Construction

Building walls, bridges, dams,

Road surfacing, (blocks or crushed rock)

Aggregate in concrete.

Materials of Construction-Building Stones 4

Stone / Rock

These are often used synonymously. However;

Rocks are made up of one or more minerals which have definite chemical compounds. These minerals usually have crystalline structures, but some consist of a natural non-crystalline structure.

Stone is used to define quarried or small pieces of rock for a specified function such as a building block, a paving block, etc.

Materials of Construction-Building Stones 5

Geological Classification of Rocks

• Igneous,

• Sedimentary,

•Metamorphic.

Materials of Construction-Building Stones 6

Igneous Rocks

Formed by cooling and solidification from a molten state

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Materials of Construction-Building Stones 7

Materials of Construction-Building Stones 8

Igneous Rocks

1. Intrusive Rocks: Slowly crystallized within the earth

2. Extrusive (volcanic) Rocks: Rapidly crystallized due to fast cooling on the surface of the earth

3. Pyroclastic Rocks: Formed after sudden eruption, include volcanic ash composed of fine amorphous particles.

Materials of Construction-Building Stones 9

Sedimentary Rocks

Sediments are transported, deposited and solidified through pressure exerted by overlying material or by the action of natural agents.

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Materials of Construction-Building Stones 10

Metamorphic Rocks

Formed by gradual changes

in the structures of either

igneous or sedimentary

rocks caused by the action

of heat, pressure, water

etc.

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Materials of Construction-Building Stones 11

Important Rock Types used as

Construction Material

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Materials of Construction-Building Stones 12

Granite

Coarsely crystalline intrusive rock.

Contains silica in the form of quartz, feldspar and mica

Red, pink, gray, brown

Strong, hard, non- porous

Used in flooring, interior or exterior wall facing, column facing, stair treads.

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Materials of Construction-Building Stones 13

Basalt

Finely crystalline

extrusive rock which

occurs as lava sheets.

Dark colored,

Basalt is also a hard

and strong rock, but it

is likely to somewhat

porous and fractured.

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Materials of Construction-Building Stones 14

Limestone

Sedimentary rock

composed mainly of CaCO3

Limestones containing

considerable amount of

magnesium carbonate are

dolomitic limestones.

Used as: concrete

aggregate, raw material in

cement production, flux in

the produciton of pig iron..

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Materials of Construction-Building Stones 15

Travertine

Sedimentary rock,

composed mainly of

calcium carbonate

Off-white, gray, light

to dark tan

Used as: interior

decorative stone,

due to its pleasing

texture

Materials of Construction-Building Stones 16

Sandstone

Sedimentary rock made of grains of sand cemented and compacted to form a solid rock.

SiO2 & Al2O3; cementing material may either be calcium carbonate or clayey matter.

Used as facing material

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Materials of Construction-Building Stones 17

Marble

Metamorphosed limestone, more

crystalline and harder than

limestone.

Great range of colors

Hard and strong rock which can

hold polish well.

May weather easily, used for

interior work such as wall,

column facing, flooring

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Materials of Construction-Building Stones 18

Slate

Metamorphosed clay

SiO2, Al2O3, Fe2O3, K2O, MgO

Black, green, gray, red and purple. .

Can be separated into thin sheets with smooth surfaces.

Tough, strong and non-absorptive.

Used for flooring, interior or exterior wall facing, window sills, and roofing.

Materials of Construction-Building Stones 19

Production of Building Stones

Quarrying: Overburden of soil or inferior stone is first removed from the surface. Large blocks of stone (1X1.5X3 m) are cut, loosened at the bottom by wedging and removed by cranes.

Shaping and finishing: Large blocks of stone are cut to desired shape and given whatever degree of finishing is desired.

Materials of Construction-Building Stones 20

Selection of Building Stones

Durability, appearance and cost are

important parameters.

Durability, temperature changes, average

humidity of the atmosphere, fire and

abrasion resistance (related to hardness)

are important.

Materials of Construction-Building Stones 21

Durability

The durability of a stone is its ability to resist weathering action, chemical attack, abrasion, frost, heat and other service conditions.

Both durability and the strength of a stone are affected by the texture, mineral composition, chemical and physical characteristics.

Materials of Construction-Building Stones 22

Strength

(a) the mineral composition

(b) the rate of cooling (grain size) of the igneous rocks

(c) the manner of formation and the size of the component crystals of sedimentary rocks

(d) the type and degree of metamorphism of metamorphic rocks.

Therefore, the strengths of stones show great variations. (from low values up to 3500 kgf/cm2)

Materials of Construction-Building Stones 23

Materials of Construction-Building Stones 24

Strength

The compressive strength of stone is important to support foundations or in stone masonry. However, the compressive strength of most stones is sufficiently high to be used in structures.

The strength of stone masonry is much less than the strength of stone itself, the exact strength depending on the width of the joint and the type of mortar used.

The tensile and the flexural strength of stone are much lower than its compressive strength.

Materials of Construction-Building Stones 25

Porosity & Water Absorption

The water absorption capacity of stone is related to its

porosity (amount of permeable pores)

The presence of permeable pores also affects the frost

resistance of stones. When water gets in the pores and

freezes, the ice exerts some internal pressure. Alternate

freezing and thawing processes cause cracking of stones.

total

poresof

V

VPorosity

100%, xstoneofweightDry

absorbedwaterofWeightAbsorption

Materials of Construction-Building Stones 26

Strength vs Absorption of Stone

Materials of Construction-Building Stones 27

Coefficient of Expansion

Stones expand upon being heated.

However, unlike most materials, they do not

return to their original volume when cooled

after heating. They show a small amount (0.02

to 0.04%) of permanent swelling.

The coefficient of expansion of a stone affects its

expansion upon being heated, and contraction

when cooled.

Materials of Construction-Building Stones 28

Physical Properties of Dry

Building Stones

Ultimate

Compressive

Str. (MPa)

Weight

(g/cm3)

Porosity

(%)

Coeff. Of

Expansion

(10-6/OC)

Granite 100-210 2.50-2.83 0-1 5.58-7.56

Marble 70-180 2.56-2.72 0.2-0.6 3.6-10.08

Limestone 30-140 2.23-2.69 0.3-2.0 1.8-8.46

Sandstone 50-140 2.13-2.56 5-28 0.4-4.5

Slate 50-210 2.75-2.83 0.1-0.7 12.6-18

Materials of Construction-Building Stones 29

Fire Resistance

The cause of damage in stone under high temperatures is the disintegration that occurs because of the internal stresses due to unequal expansion of unequally heated portions of the stone.

Limestone suffers little until a temperature of somewhat above 700°C is reached, at this point it decomposes (CO2 is driving off).

Sandstones suffer least from fire if they are dense and non-porous

Granites and marbles suffer great from fire.

Materials of Construction-Building Stones 30

Cast or artificial stone is a masonry product made of concrete. The surface may include granite, quartz, marble, etc. The textures may be smooth, polished, colored or uncolored.

Synthetic stone is made from minerals and a polyester plastic binder. For example, synthetic granite is produced using approximately 50% fine grained granite, 30% fine silica sand and 20% polyester resin. Synthetic marble is produced by combining approximately 80% fine silica sand, 2-3% pigment and 17-18% polyester resin (no marble!).

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Materials of Construction-Building Stones 31

Example

Two rock samples A and B have the following characteristics

Calculate the capillary porosity, permeable and impermeable pore percentages of the two rocks. Which rock is more permeable?

For Rock A

V=875/2.5=350 cm3

a) capillary porosity=12 cm3/350=0.0344=3.44%

b) permeable porosity=41/350=0.117=11.7%

c) total porosity=1-(2.5 g/cm3/2.9x1 g/cm3)=0.14=14%

Since total porosity=permeable porosity+impermeable porosity

d) impermeable porosity=0.14-0.117=0.023 (2.3%)

For Rock B

V=800/2.3=348 cm3

a) capillary porosity=10 cm3/348=0.0286

b) permeable porosity=35/348=0.100=10%

c) total porosity=1-(2.3/2.85)=0.2=20%

d) impermeable porosity=0.2-0.1=0.1 (10%)

Permeabilty of rock is controlled by its permeable porosity since A rock has a higher permeable porosity, it is expected that it will have higher permeability.

Dry weight of

sample (g)

Water absorption

by capillarity (g)

Absorption

capacity (g)

Unit weight

(g/cm3)

Specific

gravity

Rock A 875 12 41 2.5 2.9

Rock B 800 10 35 2.3 2.85