C T: Self-Compacting Concrete Unit 5 Part 2

Que5.6. Compare the hardened  parcels of normal concrete  and  tone compacting concrete. 

Answer  Following are the comparison of  parcels between normal concrete  and  tone compacting concrete 

1. Compressive Strength The compressive strength of SCC when  compared with normal concrete made for a particular strength is  nearly  the same. The  tone- compacting property of SCC has  veritably little effect on  the strength of concrete. 

2. Tensile Strength A comparison between cylinders made of SCC  and normal concrete of the same grade shows that there’s no major  difference between them. 

3. Bond Strength The pull- out test carried out to determine the bond  strength of SCC indicates superior bond strength of SCC. 

4. Modulus of Pliantness The modulus of pliantness for SCC and for  normal concrete is the same. 

5. snap- thaw Resistance The low- strength of SCC has  lower resistance  to  snap and thaw conditions as compared with low- strength normal  concrete. 

6. Creep SCC  typically is more  doughy as compared with normal concrete.  So its creep is slightly advanced. 

7. continuity continuity is slightly advanced in SCC because of the  elimination of  crimes which may  do during placing and  contraction  of normal concrete. SCC is likely to have  lower voids. 

8. Exposure to Fire SCC has a more compact microstructure. This can  lead to high vapour pressure. So SCC has a advanced  threat of spalling  when exposed to fire. 

Que5.7. Explain the tests used for inflow  parcels of  tone  compacting concrete. 

Answer  Following are the  colorful test that carried out on  tone compacting concrete  is fresh state 

1. Depression Flow and T50 Test  Depression inflow test is used to find the  stuffing capability of the SCC. 

ii. The SCC sample is poured in to the depression cone  also the depression inflow  periphery is measured.  iii. The inflow time is measured and is known as T50 depression time.  iv. The advanced the depression inflow value, the lesser its capability to fill formwork  under its own weight. 

2. L- Box Test  i. The L- box test is used to find the  end capability of SCC.  ii. The SCC sample is poured in to the L- box  outfit, now the plate is  removed to allow inflow.  iii. The L- box  rate is calculated as H2/ H1.  iv. When the  rate of H2 to H1 is larger than0.8,  tone compacting concrete  has good passing capability. 

3. V- Funnel Test and V- Funnel Test at T- 5 twinkles  i. The V-  channel test is used to find the  isolation resistance of SCC.

ii. The SCC sample is poured in to the V-  channel  outfit, now it’s allowed  to inflow by its weight.  iii. The  evacuating time of V-  channel is noted.  iv. This test measured the ease of inflow of the concrete, shorter inflow times  indicate lesser inflow capability.

After 5  twinkles of setting,  isolation of  concrete will show a  lower  nonstop inflow with an increase in inflow time. 

Que5.8. What’s the necessity fibre  corroborated concrete and  explain compactly the factors affecting  parcels of fibre  corroborated  concrete. 

Answer  Necessity of Fiber Reinforced Concrete 

1. It increases the tensile strength of the concrete. 

2. It reduces the air voids and water voids the  essential porosity of gel. 

3. It increases the  continuity of the concrete. 

4. filaments  similar as graphite and glass have excellent resistance to creep,  while the same isn’t true for  utmost resins. 

5. The  discriminational  distortions of concrete and the  underpinning are  minimized. 

6. It has been  honored that the addition of small,  nearly spaced and  slightly dispersed  filaments to concrete would act as crack arrestor and  would  mainly ameliorate its static and dynamic  parcels. 

Factors Affecting the parcels of FRC Following are the factors  affecting the  parcels of fibre  corroborated concrete 

1. Volume of Fiber  Low volume bit(< 1) Used in arbor and pavement that have large  exposed  face leading to high  loss cracking.  ii. Moderate volume bit( between 1 and 2) Used in construction   system  similar as shotcrete and in structures which requires  bettered  capacity against delamination, spalling and fatigue.  iii. High volume bit(> 2) Used in making high performance fiber   corroborated  mixes. 

2. Aspect rate of Fiber  It’s defined as  rate of length of fiber to its periphery( L/ d).  ii. Increase in the aspect  rate upto 75, there’s increase in relative strength  and durability.  iii. Beyond 75 of aspect  rate, there’s  drop in strength and durability. 

3. exposure of filaments filaments aligned  resemblant to applied  cargo offered  more tensile strength and durability than aimlessly distributed or   vertical  filaments. 

4. Relative Fiber Matrix  Modulus of pliantness of matrix must be  lower than of  filaments for effective  stress transfer.  ii. Low modulus  filaments like Nylons and Polypropylene imparts  further energy   immersion while high modulus  filaments( Steel, Glass, and Carbon) imparts  strength and stiffness. 

5. Plasticity and contraction of Concrete objectification of  sword  fiber decreases the plasticity  vastly. This situation negatively  affects the  connection of fresh  blend. Indeed prolonged external vibration  fails to compact the concrete. 

6. Size of Coarse Aggregate filaments also act as aggregate maximum size  of the coarse  total should be  confined to 10 mm, to avoid  perceptible  reduction in strength of the  compound. 

7. Mixing Mixing of fiber  corroborated concrete  requirements careful conditions to  avoid balling of  filaments,  isolation and in general the difficulty of mixing  the accoutrements  slightly. 

Que5.9. Explain the  colorful types of fiber used in fiber   underpinning concrete. 

Answer  Types of Fiber Following are the  colorful types of  filaments used in fiber   corroborated concrete 

1. Steel Fiber  Steel fiber is one of the most generally used fiber. They’re generally  round. The periphery may vary from0.25 mm to0.75 mm.  ii. The  sword fiber is likely to get rusted and lose some of its strength.  iii. Use of  sword fiber makes significant advancements in flexural impact  and fatigue strength of concrete.  iv. Steel  filaments have been  considerably used in overlays or roads pavements,  air fields, ground balconies, thin shells and floorings  subordinated to wear and tear and  gash and chemical attack. 

2. Glass Fiber  i. These are produced in three  introductory forms  Rovings.  Beaches.  Woven or diced  beachfront mat.  ii. Major problems in their use are breakage of fiber and the  face   declination of glass by high alkalinity of the doused  cement paste.  iii. Glass fiber  corroborated concrete( GFRC) is  substantially used for  ornamental   operation rather than structural purposes.  iv. With the addition of just 5 glass  filaments, an  enhancement in the impact  strength of over to 1500 can be  attained as compared to plain concrete.  With the addition of 2  filaments the flexural strength is  nearly doubled. 

3. Plastic Fiber  filaments  similar as polypropylene, nylon, tempera, aramid and polyethylene  have high tensile strength  therefore inhibiting  buttressing effect.  ii. Polypropylene and nylon  filaments are  set up to be suitable to increase the  impact strength.  iii. Their addition to concrete has shown better distribute cracking and  reduced crack size. 

4. Carbon Fiber  Carbon  filaments  retain high tensile strength and high  youthful’s modulus.  ii. The use of carbon fiber in concrete is promising but is  expensive and  vacuity of carbon fiber in India is limited. 

5. Asbestos Fiber  Asbestos is a mineral fiber and has proved to be most successful fiber,  which can be mixed with OPC.  ii. The maximum length of asbestos fiber is 10 mm but generally  filaments are  shorter than this

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