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