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.