CHEMISTRY CONCRETE PERTEMUAN 05

Matakuliah : S0372 – Kimia Teknik SipilTahun : Ganjil 2007/2008

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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

Bina Nusantara Process Of Hydraulic Chalk.

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SEMEN PORTLANDCement 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.

Bina Nusantara Percentage Of Composition Cement Portland.

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WATERWater 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

Condition of Environment

Relate to

Factor Water

Cement Maximum

Rate Cement Minimum. (Kg/m3)

40mm* 20mm*

Reinforced Concrete.

Freshwater 0.5 260 290

Brackish Water / Water Sea

0.45 320 360

Prestressed Concrete.

Freshwater 0.5 300 300

Brackish Water / Water Sea

0.45 320 360

*) Maximum size Aggregate.

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Conditions to the Condition of Special Environment.

Type ConcreteCondition of Environment

*

Factor Water Cement

Maximum, Normal

Concrete

Content cement minimum ( Kg/m3 )

Maximum Aggregate size measure, mm.

40 20 14 10

Reinforced Light. 0.65 220 250 270 290

  Middle 0.55 260 290 320 340

  Heavy. 0.45 320 360 390 410

Prestressed Light. 0.65 300 300 300 300

  Middle 0.55 300 300 320 340

  Heavy. 0.45 320 360 390 410

Non-ReinforcedLight.

0.65 200 220 250 270

  Middle 0.55 220 250 280 300

  Heavy. 0.45 270 310 330 360

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*) 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.