Concrete Technology: Properties and Effect on Concrete Properties Unit 2 Part 2

Que2.15. Explain the  goods of silica cloud on concrete  parcels.  Answer  Effect of Silica Cloud on the parcels of Fresh Concrete 

1. Plasticity  Reduced plasticity. 

ii. Water demand increases in proportion to silica cloud added. Water  demand is 1 for every 1  relief of cement. 

iii. Lower depression and  further cohesive  blend. 

2. Bleeding and isolation  Bleeding is reduced as silica cloud  patches find their way in between  two cement grains. 

ii. isolation is reduced has the concrete  blend is more cohesive due to  increase in number of solid to solid contact points. 

3. Time of Setting The  original setting time and final setting time is not  greatly  told . The increase may be 30 min or so. 

4. Plastic loss Since silica cloud concrete show no bleeding, fresh  concrete is  subordinated to plastic  loss.  goods of Silica Cloud on the parcels of Hardened Concrete 

1. Drying loss Long term  loss of concrete isn’t affected  significantly by the addition of silica cloud. 

2. Creep The creep of concrete containing silica cloud will be lower than  corresponding Portland cement concrete. 

3. Chemical Resistance A major reason for the  bettered resistance of  concrete to acidic and sulphate waters is the reduction in the Ca( OH) 2  content of the cement paste, which decreases linearly with the  quantum  of silica cloud added. 

4. Alkali Aggregate response lower than 10 of silica cloud is  set up  acceptable for reducing the alkali  total expansion as compared to fly  ash which requires 30-40  relief. 

5. Strength Strength of 62- 80 MPa can be  fluently achieved.

6. Permeability Silica cloud reduce the size of voids in doused  cement  paste,  therefore making them  nearly impermeable indeed at early  periods with  addition of silica cloud by weight of cement. 

7. snap and thaw Effect The effect of silica cloud concrete on freezethaw  affect isn’t  veritably significant. 

Que2.16. What are the advantages, disadvantages and uses of  silica cloud?  

Answer  Advantages of Silica Cloud Following are the advantages of silica  cloud 

1. Lowers concrete permeability. 

2. Significantly increases concrete  continuity. 

3. Increases ultimate strength gain. 

4. salutary in all types of high strength concrete  operations. 

5. Improves bond strength to  sword. 

6. Significantly reduces alkali- silica reactivity. 

7. Provides excellent resistance to sulphate or seawater attack. 

8. Reduces  sword  erosion. 

9. Improves  snap/ thaw  continuity of concrete. 

Disadvantages of Silica Cloud Following are the disadvantages of  silica cloud 

1. Silica cloud concrete  loss rate is a large. 

2. Silica cloud concrete plasticity is poor. 

3. It’s easy to produce temperature cracks. 

Uses of Silica Cloud 

1. For  product of high strength concrete,  erosion- resistant concrete,  bruise- resistant concrete, and low permeability concrete. 

2. Used to make seamster and manhole  form products. Reduces answer in  shotcrete  operation. 

Que2.17. What’s ground granulated blast furnace sediment( GGBS)?  What are its benefits and also write down the chemical composition  of the sediment GGBS. 

Answer  Ground Granulated Blast Furnace Sediment( GGBS) 

1. The blast furnace sediment is a derivate of the iron manufacturing assiduity.  Iron ore, coke and limestone are fed into the furnace and the performing  molten sediment floats above the molten iron at a temperature of about  1500 °C to 1600 °C. 

2. The molten sediment has a composition of about 30 to 40 SiO2 and about  40 CaO, which is close to the chemical composition of Portland cement.  Benefits of GGBS in Concrete 

1. Heat of Hydration Gradational hydration of GGBS with cement generates  lower heat than Portland cement. This reduces thermal  slants in the  concrete. 

2. Water Demand GGBS is a glassy material and its smoother  face  requires  lower water to adequately cover the  patches. 

3. Setting Time Increased setting time may be  profitable in extending  the time for which the concrete remains workable and, may reduce the   threat of cold joints. 

4. Appearance  GGBS cement also produces a smoother, more  disfigurement free  face, due  to the fineness of the GGBS  patches.  ii. GGBS is effective in  precluding efflorescence when used at  relief   situations of 50 to 60. 

5. Bleeding GGBS reduce bleeding than that of Portland cement and   thus reduces  threat of delaminations. 

6. Workability GGBS  patches are less water absorptive than Portland  cement  patches and  therefore GGBS concrete is more workable than  Portland cement concrete.

For original plasticity, a reduction in  water content of over to 10 is possible. 

7. Sulphate Resistance GGBS is a sulphate-  defying, specifying GGBS  at 50-70 content gives optimum protection against sulphate attack. 

8. Alkali Aggregate response( AAR) GGBS reduce the  injurious  effect of AAR due to its low reactive alkali content and its capability to  inhibit AAR. 

Que2.18. What are the  goods of using GGBS in concrete? 

Answer  goods of GGBS on the parcels of Fresh Concrete 

1. The cementitious material containing GGBS displayed lesser  plasticity due to the increased paste content and increased cohesiveness  of the paste. 

2. generally, an increase in time of setting can be anticipated when GGBS is  used as  relief for part of the Portland cement in concrete  fusions. 

3. GGBS is finer than the Portland cement and is substituted on an equalmass  base, bleeding is reduced; . When the GGBS is coarser, the rate and  quantum of bleeding may  increase.  goods of GGBS on the parcels of Hardened Concrete 

1. drop strength and rate of strength gain. 

2. Increase the resistance to freezing and thawing. 

3. Increase the resistance to deicing chemicals. 

4. Increase the resistance to the  erosion of  underpinning. 

5. Reduction of expansion due to alkali- silica  response( ASR). 

6. Increase the resistance to sulfate attack. 

7. Reduce the permeability. 

Que2.19. What’s the use of GGBS in concrete? 

Answer  Following are the uses of GGBS in concrete 

1. GGBS is used to make durable concrete structures in combination with  ordinary Portland cement and/ or other pozzolanic accoutrements . 

2. Two major uses of GGBS are in the  product of quality-  bettered sediment  cement,  videlicet Portland Blast Furnace Cement( PBFC) and High- Sediment  Blast- Furnace Cement( HSBFC), with GGBS content ranging  generally  from 30 to 70; and in the  product of ready-mixed or  point- batched  durable concrete. 

Que2.20. Describe the metakaolin. bandy the advantages and  disadvantages of metakaolin. 

Answer  Metakaolin 

1. Metakaolin is an  amalgamation used as an partial  relief of cement in  HSC( high strength concrete). 

2. A concrete is said to be high strength concrete if its compressive strength  is  further than 40MPa. 

3. Metakaolin is prepared by calcination of humus(  complexion mineral) at an  temperature of 650- 800ºC. It has pozzolanic  parcels. 

4. Chemical formula of Metakaolin is Al2O3.2 SiO2.2 H2O 

5. It reacts with Ca( OH) 2 one of the by- products of hydration  response of  cement and results in  fresh C- S- H gel which results in increased  strength.  Advantages of Metakaolin Following are the advantages of  metakaolin 

1. Strength and  continuity of concrete increases. 

2. Accelerates  original setting time of concrete.  3. Compressive strength of concrete increases by 20. 

4. Cross section of structure can be reduced safely i.e.,  quantum of concrete  used can be reduced. 

5. Reduces  loss in concrete. 

6. Eco-friendly by reducing  quantum of CO2 emigration. 

7. Reduces heat of hydration leading to loss and crack control.  Disadvantages of Metakaolin Following are the disadvantages of met kaolin 

1. Increased cost price. 

2. Advanced water  rate. 

3. Plasticity. 

4. fresh raw material. 

5. At low addition rate increase  loss.

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