KLINIK KONSTRUKSI 8

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KLINIK KONSTRUKSI 8

CLINICS OF CONSTRUCTION 8

PROLOG:

In the market and factory, Type V of Portland Cement or High Sulfat Resistance Portland Cement (HSRPC) and Type II of Portland Cement or Moderate Sulfate Resistance or Heat Hydration Portland Cement (MSRHPC) is difficult to meet. It’s due to the limited production. Type V and Type II of Portland Cement is produced by JOB ORDER not MASS PRODUCTION as produce Type I (OPC), because of the limited of market demand. For this case there’s alternative solution to substitute Type V and Type II by Pozzolan Portland Cement (Type IP)

By : Ratmaya Urip

Modul 29 of Cement & Concrete Technology Series:

SUBSTITUTING TYPE II AND TYPE V PC

BY

POZZOLAN PORTLAND CEMENT

(PPC-TYPE IP)

A. TYPE II PORTLAND CEMENT

1. Type II Portland Cement is used where precaution against moderate sulfate

attack is important. With this moderate sulfate attack, Type II Portland Cement can be used in constructions where sulfate concentrations in groundwaters or sea environment are higher than normal but not unusually severe (Table 1).

2. Type II Portland Cement will usually generate less heat at a slower rate than Type I. With this moderate heat of hydration, Type II Portland Cement can be used in structures of considerables mass, such as large piers, heavy abutments, heavy retaining walls, large dams, and other mass concrete. Its’ use will reduce temperature raising, most importantly when the concrete is placed in warm weather.

Note : In British term, Type II Portland Cement is called as

Moderate Sulfate Resistance and Heat Hydration Portland Cement

(MSRHPC)

Requirements :

C3A Maximum 8% (ASTM C 150)

C3S + C3A Maximum 58%

Max Heat Of Hydration 290 kJ/kg at 7 days, 330 kJ/kg at 28 days (ASTM C 186)

CONCLUSION :

1. Moderate Heat of Hydration can be reached by managing

Heat of Hydration not more than 290 kJ/kg at 7 days and

330 kJ/kg at 28 days (ASTM C 186)

Also can be reached by managing C3A maximum 8%

(ASTM C 150), to reduce heat of hydration

2. Moderate Sulfate Resistance can be reached by managing

C3A content maximum 8% (ASTM C 150), to reduce

reaction between C3A and Gypsum

B. TYPE V PORTLAND CEMENT

Type V Portland Cement is a sulfate-resisting cement used only in concrete exposed to severe sulfate action, principally where soils or groundwaters have a high sulfate content. Table 1 describes sulfate concentrations require the use of Type V Portland Cement. Low Tricalcium Aluminate (C3A) content, generally 5% or less, is required when high sulfate resistance is needed.

Sulfate Resistance can be reached if :

There is no reaction between Tricalcium Aluminate and Gypsum.

The reaction will form tricalcium aluminate tricalcium sulfate hydrate (ettringite). Ettringite causes micro-crack. Low Tricalcium Aluminate can decrease reaction between Gypsum and Tricalcium Aluminate

3CaO.Al2O3 + 3CaSO4 + 31H2O à 3CaO.Al2O3.3CaSO4.31H2O

Note : In British term, Type V Portland Cement is called as

High Sulfate Resistance Portland Cement

Requirements :

C3A Maximum 5% (ASTM C 150)

C4AF + 2(C3A) Maximum 25%

CONCLUSION :

High Sulfate Resistance can be reached by decreasing C3A content until maximum 5% (ASTM C 150), to reduce reaction between C3A and gypsum. Decreasing reaction between C3A and gypsum means reduce ettringite. Ettringite can make concrete swell (expand) and brittle.

C. POZZOLAN PORTLAND CEMENT

Pozzolan Portland Cement (PPC) is produced by PT Semen Gresik (Persero) Tbk to substitude Type II and/or Type V Portland Cement, because Pozzolan PortlandCement is categorized as sulfate resistance and moderate-low heat of
hydration portland cement.

Pozzolan Portland Cement (PPC) produced by PT Semen Gresik (Persero) Tbk is categorised as blended cement Type IP (MS) and has met the requirement of ASTM C 595-03 and/or SNI 15-2049-04.

Pozzolan Portland Cement (PPC) is applicable for constructions in sea water environment with high and medium sulfate attack, and also for construction using mass concrete such as heavy dam or heavy foundation.

PROJECT REFERENCES USING PPC :

1. Sea Water Environment

- Port Of PT Semen Gresik (Persero) Tbk (Tuban, East Java)

- Port of Tanjung Perak (Surabaya, East Java)

- Paiton Steam Power Plant (Situbondo, East Java)

- Tanjung Jati Steam Power Plant (Jepara, Central Java)

- Development of Juanda International Airport (Sidoarjo, East Java)

- Etc.

2. Mass Concrete

- Sampean Baru Dam (Bondowoso, East Java)

- Wonorejo Dam (Malang, East Java)

- Foundation of Westin Hotel (Surabaya, East Java)

- Etc

Sulfate resistance can be reached by pozzolanic reaction as shown in the FLOWCHART-1 ( page 9 ) above or :

2(3CaO.SiO2) + 6H2O à 3CaO.2SiO2.3H2O + 3Ca(OH)2 ...... 1)

( 2C3S + 6H à C3S2H3 + 3 CH )

2(2CaO.SiO2) + 4H2O à 3CaO.2SiO2.3H2O + Ca(OH)2 .. ..... 2)

(2C2S + 4H à C3S2H3 + CH)

3Cao.Al2O3 + 6H2O à 3CaO.Al2O3.6H2O ...................... 3)

(C3A + 6H à C3AH6)

4CaO.Al2O3.Fe2O3 + 2Ca(OH)2 + 10H2O à 3CaO.Al2O36H2O + 3CaO.Fe2O3.6H2O

(C4AF + 2CH + 10H à C3AH6 + C3FH6) ........... 4)

Sulfate will attack concrete in sulfate environment such as sea environment.

Sulfate attack can be explaned as follows :

1. Sulphat will attack calcium hydroxyde-Ca(OH)2, form gypsum-CaSO42H2O

3MSO4 + 3Ca(OH)2 + 6H2O à 3CaSO4.2H2O + 3M(OH)2 .... 5)
Volume of concrete will swell (expand) 2,2 X

2. Gypsum from 5) will react with calcium aluminat hydrat from 3) form Calcium sulfoaluminat hydrat or ettringite (C3A.3CaSO4.31H2O).

3CaSO4.2H2O + C3AH6 + 19 H2O à C3A.3CaSO4.3H2O ...... 6)

Total of reaction 5) and reaction 6) will accumulate sulfate attack as follows :

3MSO4 + 3Ca(OH)2 + C3AH6 + 25H2O à C3A.3CaSO4.31H2O + 3M(OH)2

……. 7)

Volume of concrete will swell (expand) 2,86 X

Portland Pozzolan Cement (PPC) will reduce sulfate attack, because the content of SiO2 and Al2O3 (pozzolan) in PPC will react with Ca(OH)2 resulted from reaction 1) and reaction 2). So reaction 5), 6), and 7) do not occur.

Ca(OH)2 + SiO2 à CSH

Ca(OH)2 + Al2O3 à CAH

CSH & CAH à

1. Reduce permeability of concrete (reduce porosity)

2. Make concrete solid
3. Make concrete more waterproof
4. Etc.

2. Moderate-low heat of hydration can be reached by using of pozzolan (especially SiO2 and Al2O3) from PPC

Ca(OH)2 resulted by the above reactions (reaction 1 and reaction 2) will react with pozzolan (SiO2 and Al2O3) from Pozzolan Portland Cement (PPC).

Reaction is slower. Due to the pozzolanic reaction, heat of hydration will be reduced. It will make concrete more solid (increase density). So it will reduce micro crack.

CONCLUSION : Sulfat Attack

Ca(OH)2 produced by reaction 1) and reaction 2) shown in page 15, will react with pozzolan (SiO2 and Al2O3) from PPC. It means reaction 5), reaction 6) and reaction 7) shown in page 16 not happened. So there’s no sulfate attack. Because sulfate can not react with Ca(OH)2 due to the pozzolanic reactivity between Ca(OH)2 with pozzolan (SiO2 and Al2O3) from PPC, form CSH.

Forming CSH will reduce porosity and/or permeability and increase density of concrete. Instead of resistance from sulfate attack, new formed CSH is also resistance from chloride attack. Chloride always attack steel bar in concrete through micro-crack formed due to the sulfate attack and/or through pore of concrete, if there’s no reaction between Ca(OH)2 with pozzolan.

CONCLUSION : Heat Of Hydration

Pozzolanic reactivity will decrease heat of hydration. Reaction between Ca(OH)2 with pozzolan (SiO2 and Al2O3) from PPC make the reaction gets slower.

This will reduce micro crack which make concrete more solid, or increase density, increase chloride attack resistance, decrease porosity and/or permeability and increase workability, etc.

The Advantages of Using PPC :

1. Improve workability
2. Lowering heat of hydration
3. Increase watertightness
4. Decrease porosity and/or permeability
5. Increase density
6. Improve resistance to sulfate attack and sea water
7. Improve resistance to chloride attack
8. Reduce alkali-aggregate reaction
9. Lower susceptibility to dissolution and leaching
10. Longer time bigger strength
11. Increase durability

Special information :

Sulfat resistance and decreasing of heat of hydration could reach not only by Pozzolan Portland Cement (PPC) or Type IP, but also by using

SPECIAL BLENDED CEMENT (SBC Type)

Note : For further information and presentation in detail, please contact :

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Ratmaya Urip

E-mail: ratmayaurip@yahoo.com