2. 2.1:INTRODUCTION
Stone is a natural substance, which form the earth’s
crust. Stones are mixture of two or more minerals.
Minerals are substances that are formed naturally in
the Earth.
Following are some important uses of stones in civil
engineering
I. Construction of residential and public building,
dams, weirs , harbors and supports for bridges.
II. Used in the form of veneers for decorative front and
interior building
III. Used as aggregate for concrete and railway ballast
3. 2.2:CLASSIFICATION
OF ROCKS
The rocks from which stones are obtained are
classified in the following four ways
1. Geological
2. Physical
3. Chemical
4. Practical
1. Geological classification
i. Igneous rock is a rock that has formed from the
cooling and solidification of magma or lava.
4. ii. Sedimentary rocks Generally form from the
compaction and cementation of sediments
,sediment are fragments of rock that have been
broken down as a result of weathering .
iii. Metamorphic rocks are rocks that are changed
as result of exposure to intense heat and/or
pressure.
2. Physical classification
i. Stratified rocks are those which exhibit distinct
layers which can be separated.
ii. Unstratified rocks are rocks do not show any
sign of starta and can not easily split into slap.
5. 3. Chemical classification
i. Siliceous rocks are sedimentary rocks that have
silica (SiO2) as the principal constituent.
ii. Agrillaceous are rocks that have clay and
alumina as the main constituent.
iii. Calcarious rocks have calcium carbonate or
lime as their leading constituent.
4. Practical classification
Practical classification is based on the usage and
stones are practically classified as :Granites ,
Basalts, Marbles , Limestone , Sandstones, Slates.
6.
7. 2.3:COMMON ROCK-
FORMING MINERALS
Silica:quartz is pure or nearly pure silica and is
hard and classy mineral.it occurs in granite and
has a specific gravity of 2.66 and hardness of 7
Felsper are the silicate of alumina with alkaline
substances.it also occurs in both good granite and
bad ones.the good ones mainly in the form of grey
or radish brown bright crystalline and in the bad
ones as eartly apearence. It specific gravity 2.5-
2.7 and hardness of 6
8. Mica:it contains silicate of aluminum with
potassium it is of dark grey black or brown clour.it
is very soft and easily effects by atmosphere and
chemicals.it has hardness of 2.5 and specific
gravity of 3
Hornblende:it is very complex silicate and it`s
clour varies from dark green to black.it has
hardness of 5.5 and specific gravity 3.2
9. Calcite:it is the leading constituent of the
limestone and marbles.it`s clour varies from white
to grey hardness 3 and specific gravity2.7
Dolomite:it is magnesium carbonate.it is
commonly found in dolomitic limestones and
dolomitic marbles.it`s stability and weither resisting
property is better than pure calcium carbonate
10. 2.4:CHARACTERISTICS
OF GOOD BUILDING
STONE
To find the suitability of stones under different
conditions the following charectristics should
be considered:
Apearence and clour:the stones to be
employed for decoration works should have
uniform and appealing clour and free from clay
holes and flaws
Weight:Aheavy stone possesses more
compactness and less porosity
11. porosity and absorption
fineness of grain
compactness
Resistance to fire
Electrical resistance
Hardness and toughness
Strength
Durability
12. 2.5:USES OF STONE AND
THEIR SELECTION
Sand stone:
Sandstone :is used for general building such as walls
, foundations and supper structure. this we can say it
most abundant stone in Somalia and it easy for find
out. the
reason we use these fields is it has property hard and
durable.
Compact stone: is commonly used for exposed fire
because of fire resistance property.
Marble and slate :are commonly used electrical
switch boards because it is non-absorbent of water
that why it posses electrical resistance. also marble
can use decoration of inside home.
13. GRANITE: is mostly commonly used these fields:
1. Construction of building exposed to high wind
blowing particles. This means when we use granite
in these fields we can use external and internal . I f
we take when we commonly used is floor or
staircase and mantel pieces.
2. Heavy construction such as bridges docks, road
metals. the properties of granite enables when we
work these heavy construction we should use
granite .
The best selection of granite of these is because of it is
hard due to presence of silica
14. Limestone: this stone is used for two areas
mostly, when we manufacturing the lime and
when we manufacturing the iron as a flux.
When we decompose limestone we can
converted into lime by using a process of
heating the limestone by industrial process.
Limestone is also used for paving of roads
and it raw of material cement
15. Gneiss: it is strong , durable and capable
and that is why we use heavy construction
such as bridges.
Basalt: is hard and tough and often used
road metals and railways like granite. The
reason to select this stone to work these
area is it has abrasion resistance means the
rate of wear is long or how it takes to wear
take more hundreds years if we construct
correctly.
16. 2.6:DETERIORATION
OF STONES
1. Rain: stone get wet due to rain and
becomes dry due to sun. The harmful acids
and gases contained rain water also
exercise a damaging effect on the stone
2. Temperature: the stone also gets
deteriorated due to frequent changes of
temperature
3. Wind: strong wind carrying with dust strikes
the stones and brings the weir of the stones
17. 4. Frost: when the stone is used in the climatic
conditions, the water in the pores freezes. It
expands and splits the stone
5. Atmospheric impurities: in an industrial
towns the presence of acid affect the stone
6. Vegetable growth
7. Living organisms
8. Movements of chemicals
18. 2.7:PRESERVATION OF
STONES
The permanence of stones can be increased if we
preserve them properly.
Preservation is to make stone strong enough to resist
the deterioration
Methods of preservation
T Fill up the stone pores
To Coat the stone using preservatives
Different types of stones should not be laid close to
each other(limestone and sandstone)
To check the growth of plants and trees on the stone
