Matakuliah : S0372 – Kimia Teknik Sipil
Tahun
: Ganjil 2007/2008
CHEMISTRY CONCRETE
PERTEMUAN 05
CHEMISTRY CONCRETE
• Cement
• Water
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- CEMENT Cement represent the result of very complex industry, with mixture
and also different formation. Cement can be differentiated to
become two group :
– Non-Hidrolik cement.
– Hydraulic Cement.
1. Non-Hydraulic Cement.
Non-Hydraulic Cement cannot fasten and ossify underwater
however can ossify on the air. Special example of hydraulic
cement is chalk.
Good Chalk type is white chalk, that is consist of high oxide
calcium when still in form of chalk of tohor ( not yet related to
water ) and will contain many hydroxide calcium when have
related to water.
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Chalk yielded by burning carbonate calcium or
limestone with along with materials – its pollutant
materials, that is magnesium, silicate, iron, alkali,
brimstone and alumina. Process combustion executed
in high kiln stove at temperature 800o-1200oC.
CaCO3  CaO + CO2
Formed to be Oxide calcium to be referred by chalk of
tohor, and if relating to water will become hydroxide
calcium and also heat.
CaO + H2O  Ca(OH)2 + heat
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2. Hydraulic Cement.
Hydraulic cement have ability to fasten and ossify in water.
Hydraulic Cement example :
a. Hydraulic chalk
b. Cement of Pozollan
c. Cement of terak
d. Natural cement
e. Cement of Portland
f. Cement portland-pozollan
g. Cement high kiln terak portland
h. Cement of Alumina
i. Expansif cement
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Process Of Hydraulic Chalk.
SEMEN PORTLAND
Cement of Portland is construction materials which at most
used in work of concrete. According to ASTM C-150, 1985,
cement of portland defined as hydraulic cement which yielded
by milling klinker which consist of hydraulic silicate calcium,
which generally contain one or more sulphate calcium form
upon which milled addition with – is equal to materials the core
important.
Special materials cement of portland is chalk (CaO), silika
(SiO3), alumina (Al2O3), a few magnesia (MgO), and
sometimes a few alkali. To control its composition, sometimes
added iron oxide, while gypsum (CaSO4.2H2O) enhanced to
lead the time to fasten cement.
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Making the cement of portland executed to pass some step,
that is :
1. Mining in quarry.
2. Resolving in plant crushing.
3. Blending
4. Mixing of materials.
5. Ciln
6. Hulling return result of combustion.
7. Addition of additional materials.
8. Packing plant
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Marginally, there is four especial chemical compound
which compile cement of portland, that is :
1. Trikalsium Silicate (3CaO.SiO2),shortened to
become C3S.
2. Dikalsium Silicate (2CaO.SiO2), shortened to
become C2S.
3. Trikalsium Aluminat (3CaO.Al2O3) shortened to
become C3A
4. Tertrakalsium aluminoferrit (4CaO.Al2O3.Fe2O3)
shortened to become C4AF.
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Regulation of concrete 1989 (SKBI.1.4.53.1989) in its divide
cement of portland become five type (SK.SNI T-15-1990-03:2)
that is :
– Type of I, cement portland which in its use do not need
special conditions like other type.
– Type of II, cement portland which in its use need resilience
to hydration heat and sulphate.
– Type of III, cement portland which in its use need strength
early high in start phase after cordage happened.
- Type of IV, cement portland which in its use need low
hydration heat.
- Type of V, cement portland which in its use need high
resilience to sulphate.
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Percentage Of Composition Cement Portland.
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WATER
Water needed in the making of concrete to trigger process of
chemical cement, wetting aggregate and give amenity in work
of concrete.
Water able to be drinked generally can be used as concrete
mixture. The consist of water dangerous compound, impure
salt, oil, sugar, or other chemicals, if weared in concrete
mixture will degrade the quality of concrete, even can denature
– nature of yielded concrete.
Because cement pasta represent result of reaction of
chemistry between cement with water, hence non comparison
of amount irrigate to totalizeing important mixture weight, but
exactly comparison of water with cement or which is ordinary
to be conceived of Water cement factor.
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Rule of minimum for the concrete of waterproof.
Type
Concrete
Reinforced
Concrete.
Prestressed
Concrete.
Condition of
Environment
Relate to
Factor
Water
Cement
Maximum
Freshwater
40mm*
20mm*
0.5
260
290
Brackish Water /
Water Sea
0.45
320
360
Freshwater
0.5
300
300
Brackish Water /
Water Sea
0.45
320
360
*) Maximum size Aggregate.
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Rate Cement Minimum.
(Kg/m3)
Conditions to the Condition of Special Environment.
Type Concrete
Reinforced
Prestressed
Condition of
Environment
*
Content cement minimum ( Kg/m3 )
Maximum Aggregate size measure,
mm.
40
20
14
10
Light.
0.65
220
250
270
290
Middle
0.55
260
290
320
340
Heavy.
0.45
320
360
390
410
Light.
0.65
300
300
300
300
Middle
0.55
300
300
320
340
Heavy.
0.45
320
360
390
410
0.65
200
220
250
270
Middle
0.55
220
250
280
300
Heavy.
0.45
270
310
330
360
Non-Reinforced
Light.
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Factor Water
Cement
Maximum,
Normal
Concrete
*) Condition of Environment.
– Light : Covert fully from aggresive condition or
weather, except momentary when open
construction to normal weather.
– Middle : Is covert from torrential rains, planted
concrete and concrete which is under water
forever.
– Heavy : Open to sea water, brackish water, hard
and close rain, commutation among hard and
wet, commutation between dry and wet.
Experiencing of heavy condensation or corrosive
vapour.
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