Que5.1. What do you understand by high strength concrete? Write down its advantages and disadvantages.
Answer High Strength Concrete For fusions made with normal- weight summations, high- strength concretes are considered to be those which have compressive strengths in excess of 40 MPa.
Advantages of HSC
1. High compressive strength.
2. Increases rental space.
3. Reduces space enthralled by columns.
4. Reduces dead cargo.
5. Reduces quantum of sword.
6. High rise structures can be make by reduced columns.
7. To use the concrete service at early age,e.g., pavement in 3 days
C. Disadvantages of HSC
1. Must be moxie in selection of constituents.
2. Damaged at high temperature i.e., lower resistance to fire.
Que5.2. bandy the guidelines to selection of accoutrements for HSC.
Answer 1. For the advanced target compressive strength of concrete, the outside size of concrete named should be small, so that the concrete can come more thick and compact and less void rate.
2. Up to 70 MPa compressive strength can be produced with a good coarse total of a maximum size ranging from 20 to 28 mm.
3. To produce 100 MPa compressive strength total with a maximum size of 10 to 20 mm should be used.
4. Concretes with compressive strengths of over 125 MPa have been produced with 10 to 14 mm outside size coarse total.
5. Using supplementary cementitious accoutrements , similar as blast- furnace sediment, fly ash and natural pozzolanas, not only reduces the product cost of concrete, but also addresses the depression loss problem.
6. The optimum negotiation position is frequently determined by the loss in 12 or 24 hour strength that’s considered respectable, given climatic conditions or the minimal strength needed.
7. While silica cloud is generally not really necessary for compressive strengths under 70 MPa, utmost concrete fusions contain it when advanced strengths are specified.
Que5.3. What are the colorful styles to achieve high strength in concrete? Also bandy their operations.
Answer styles to Achieve High Strength in Concrete Following are the special styles to achieve high strength in concrete
1. sowing This involves adding a small chance of finely ground, completely doused Portland cement to the fresh concrete blend. This system may not hold important pledge.
2. Revibration Controlled revibration removes all the blights like bleeding, water accumulates, plastic loss, nonstop capillary channels and increases the strength of concrete.
3. High Speed Slurry Mixing This process involves the advance medication of cement- water admixture which is also blended with total to produce concrete.
4. Use of cocktails Use of water reducing agents are known to produce increased compressive strength.
5. Sulphur Impregnation Satisfactory high strength concrete have been produced by macerating low strength pervious concrete by sulphur.
6. Inhibition of Cracks If the propagation of cracks is inhibited, the strength will be advanced. Concrete cells made this way have yielded strength up to 105MPa.
Applications of High Strength Concrete
1. High strength concrete is needed in engineering systems that have concrete factors that must repel high compressive loads.
2. High strength concrete is generally used in the construction of high- rise structures.
3. It has been used in factors similar as columns( especially on lower bottoms where the loads will be topmost), shear walls, and foundations.
4. High strengths are also sometimes used in ground operations as well.
5. High strength concrete is sometimes used in the construction of trace islands.
6. Use of HSC in column section decreases the column size.
7. Use of HSC in column decreases quantum of sword needed for same column.
8. In high rise structure, use of HSC increases the bottom area for rental purpose.
9. In islands, use of HSC reduces the number of shafts supporting the arbor.
Que5.4. What’s tone compacting concrete? What are the parcels, advantages and disadvantages of tone compacting concrete?
Answer tone Compacting Concrete It’s defined as “ a concrete that’s suitable to inflow under its own weight and fully fill the formwork, while maintaining unity indeed in the presence of congested underpinning, and also consolidate without the need for wobbling contraction ”. Properties of SCC In fresh state, SCC have the following parcels .
Filling Capability Flows fluently at certain speed into formwork.
2. Passing Capability Passes through underpinning without blocking.
3. isolation Resistance The distribution of aggregate patches remains homogeneous in both perpendicular and vertical direction.
Advantages of SCC Following are the advantages of SCC
1. A faster rate of placing, without vibration.
2. bettered pumpability.
3. bettered connection around underpinning.
4. Reduced permeability.
5. Reduced wear and tear and gash on forms from vibration.
6. Improves the quality, continuity, and trustability of concrete structures due to better contraction and unity of concrete.
7. Ease of placement results in cost savings through reduced outfit and labour demand.
8. lower noise from vibrators and reduced peril from hand- arm vibration pattern( HAVS).
9. Improves working conditions and productivity in construction assiduity.
10. Reduced construction period.
11. Elimination of problems associated with vibration. Disadvantages of SCC Following are the disadvantages of SCC
1. More strict conditions on the selection of accoutrements .
2. Lack of encyclopedically accepted test norms and mix designs.
3. premium than conventional concrete grounded on concrete material cost exception to placement cost).
4. Requires further trial batches at laboratory as well as at ready-mixed concrete shops.
5. More precise dimension and monitoring of the element accoutrements .
Que5.5. Explain the accoutrements used for tone compacting concrete. Also give its operations.
Answer Material needed for SCC Following are the colorful material needed for making SCC
1. Cement Ordinary Portland cement of 43 or 53 grade can be used.
2. summations Well canted boxy or rounded summations are desirable.
3. Water Quality Maintained same as corroborated concrete.
4. Chemical cocktails Super plasticizers particularly polycarboxylated ethers are used in SCC.
5. Mineral cocktails Following are the mineral cocktails used is SCC Fly Ash It improves the quality and continuity of concrete.
ii. GGBFS It improves rheological parcels(semi-solid and liquid state).
iii. Silica Cloud It improves mechanical parcels.
iv. Stone Powder Finely crushed limestone, dolomite, determinedness may be added to increase greasepaint content.
Application of SCC Self compacting concrete is ideal to be used in the following operations
1. It has been used in islands and indeed onpre-cast sections.
2. Drilled shafts.
4. Earth retaining systems.
5. Areas with high attention of rebar and pipes conduits,etc.