Here are the Answers to the Questions (1-51) in Previous Blog (for Site Supervisors and Site Engineers):

1. Types of Cement

1. Ordinary Portland Cement (OPC) : This is the most widely used type of Cement, which is suitable for most general concrete constructions. OPC is available in 3 grades. 33,43 & 53 Grade. The Grade represents the strength of cement at 28 days - Eg: For 33 Grade- 33N/mm2

2. Porland Pozzalano Cement (PPC) : PPC is manufactured by mixing 30% of Pozzalano to ordinary Portland Cement clinkers. This is used in marine structures, sewage works (Dams and weirs).

3.Rapid Hardening Cement

4.Quick setting Cement

5. White Cement

6. Rapid Hardening Cement

7. Coloured Cement

8. Low heat Cement

9. Sulfates resisting Cement

10. Blast Furnace Slag Cement

11.High Alumina Cement

12. Air-entraining Cement

13. Hydro phobic Cement

14. Expansive Cement

2. Why do we use Steel Reinforcement in Concrete?

Concrete is only strong against forces of compression and has low tensile strength and ductility. The steel provides tensile strength and extra shear strength. Steel bonds well with concrete and expands and contracts due to temperature at similar rates.

3.Unit weight of Concrete

As per IS 456-200, unit weight of PCC is 24KN/m3 and RCC is 25KN/m3

4.Unit weight of Steel

The unit weight of Steel is 78.5KN/m3

5. What is M25 Concrete?

As per IS 456-2000, M- refers Mix and 25- refers Characteristic compressive strength of concrete (Concrete cube of 150mm x 150mm x150mm tested at the end of 28 days after casting should be minimum 25 KN/Sq.mm

6. Different ratios of Grades of Concrete

M5 - 1:5:10

M7.5 - 1:4:8

M10 - 1:3:6

M15 - 1:2:4

M20 - 1:1.5:3

M25 - 1:1:2

M30, M35, M40 - Design mix followed.

7.Bearing Capacity of Soil 

Bearing Capacity of the soil is the capacity to support the loads applied to the ground by foundation of the structure.

8.Minimum Curing Period

Is 456-2000 recommends that curing duration of concrete must be atleast 7 days, atleast 10 days for concrete with mineral admixtures. It also recommends that the curing duration should not be less than 10 days for concrete of OPC exposed to dry and hot weather conditions and 14 days for concrete with mineral admixtures in hot and dry weather.

9. Bending Moment (B.M) & Shear Force (S.F)

A bending moment is the reaction induced in a structural element when an external force or moment is applied to the element causing the element to bend. The most common or simplest structural element subjected to bending moments is the beam.

Shear force is the force in the beam acting perpendiculat to its longitudinal (x) axis. For design purposes, the beams ability to resist shear force is more important than ita ability to resist an axial force. Axial force is the force in the beam acting parellel to tha longitudinal axis.

10. How to find out wt of steel bar used for reinforcement

Weight of bar in Kg/m should be calculated as D² / 162. D - Diameter of rod in mm.

11. Two storeyed buildings

The building which has two floors is called two storeyed building

12. What is the standard height of each floor?

The standard height of each floor should be 3m.

13.Standard slope for staircases

As per IS 456, the slope or pitch of stair should be between 25 degrees to 40 degrees. (the preferred slope will be 30-35 degrees usually).

14. Standard height of Rise and width of Tread in Staircase

Rise - 150 -200 mm; Tread - 250-300 mm

15.Crank length in Slab

The Crank length of  bars in slab is 0.42D. D= Depth of slab-Top cover-Bottom Cover.

16.Moment of Inertia

The moment of Inertia is a geometrical property of a beam and depends on a reference axis. The Area of Moment of Inertia of a beam's cross sectional area measures the beam's ability to resist bending.The larger the Moment of Inertia, the less beam will bend.

17 Types of Slump

a) True Slump: The concrete mass after the test - when slumps evenly all around without disintegration is called the true slump.

b) Shear Slump: When one-half of the concrete mass slide down the other is called the shear slump. This type of slump obtained in a lean concrete mix.

c) Collapse slump: When the sample is collapsed due to excessive water, it is known as collapse slump.

d) Zero Slump: For very stiff and dry mixes, it does not show any changes of the slump after removing the slump cone.

18. Retaining wall

A wall constructed to resist the pressure of an earth filling is known as Retaining wall.

19.One-way / Two-way slabs

One-way slab: Ratio of Longer span / Shorter span >2

Two-way slab: Ratio of Longer span / Shorter span < / = 2

20. Recommended slumps

As per IS 456, Mass concrete, Lightly reinforced walls, slabs, beams, columns, canal lining, strip footing - 25 -75 mm

Heavily Reinforced slabs, beams, columns - 50-100 mm

21. Checking Levels at site

Levels can be checked with Sprit level, Dumpy level and leveling pipe at sites.

22.Size of Concrete cube

150mm x 150mm x 150mm

23. Fe-415 Steel Grade

 415 indicates that the Yield strength (Tensile strength when it is sunjected to elongation) of steel is 415N/mm2

24. Volume of 50 Kg Bag of Cement

Volume of 50 Kg bag of cement is 0.035 Cum

25. Minimum Dia. of steel in Columns

 12mm 

26. Maximum Reinforcement in beams

0.04bD (4% of total gross area)

27. Minimum reinforcement in slabs

0.12% of gross area

28. Minimum reinforcement in beams

Minimum area of tension reinforcement shall not be less than Ast/bd =0.85fy

 Ast - Min. area, B-breadth, D-Depth of Beam, fy-Charcateristic strength of reinforcement in N/mm2

29. Maximum Reinforcement in Columns

Max. reinforcement ratio will be 0.04 times the Columns's gross area (4%) 

30. AAC Blocks

Autoclaved Aerated Concrete Blocks

31. Min. no. of rods provided in Rectangular Columns

       4

32. Min. no. of rods provided in Circular Columns

       6

33.Flat Slab

The Two way reinforced slab which is supported on Columns (Don't have beams)

34. Compressive strength of Brick

For First class bricks - 10.3 N/mm2 (105 Kg/cm2)

35. Water absorption of First Class Brick

Max. 20%

36. Different types of slabs

One-way slabs on Beams, One-way Joist slab (Ribbed slab), Two way slabs on beams, Waffle slab, Flat slab, Hollow core slab, hardy slab, Bubble deck slab, Composite slab, Precast slab, Grade slab(on Ground)

37. Initial and Final setting time of Cement

Initial setting time is 30 minutes and Final setting time is 10 Hours.

38. Methods of Curing of concrete?

1. Sprinkling of water 2.Wet Covering with gunny bags 3. Ponding 4.Steam curing 5 Membrane curing 6.Using curing chemicals

39. Types of Foundations

Two types of foundations - Shallow and Deep foundation. Again Shallow foundations can be classified as Spread Footing, Combine footing, Strap or Cantilever footing and Mat or Raft footing. Deep Foundations can be classified as Pile footing, Pier footing, caissons footing and well foundation.

40. Construction Equipments

1. Earth moving equipment - Excavators, Backhoe, Loaders, Bulldozers, Graders, Trenchers, etc.

2. Construction Vehicles - Dumpers, Tippers, Trailers

3. Material handling Equipment - Cranes, Conveyors, Forklifts, Hoists, etc.

4. Construction Equipment - Tunneling and Handling, Concrete Mixers, 

5. Road making machines - Road Rollers, Hot mix Plants, Stone Crushers, Slurry seal machines, Slurry pumps

41. Concrete Cover

The concrete cover in renforced concrete is the least distance between the surface of embedded steel

reinforcement and the outer surface of the concrete.

42. Minimum Covers required 

In footings - 50mm, Columns - 40mm, Beams -25mm and slabs -20mm.

43. TMT Bars

TMT - "Thermo Mechanically Treated" Bars. TMT bars are used in Construction, since they have high strength and corrosion resistance.

44.Steps involved in Concreting Process

1. Batching (Process of measuring Cement, Sand and aggregates) 2.Mixing 3. Transportation, 4. Pumping, 5. Compaction 6. Curing

45. Formwork

Formwork is a type of temporary mould in which concrete is poured to cast the required shape of concrete.

46. Different types of Form work

1. Timber Form work, 2.Steel Form work, 3. Aluminium Form work, 4.Plywood Form work, 5.Plastic Form work and 6. Fabric Form work

47. Difference between Lap length, Development Length and Anchorage Length

Lap length is the length that is provided in excess over the another bar to lap one bar over another.

Itmainly depends on steel dia. used in reinforcement, grade of concrete to be used and zone it is used. 

As per IS 456:2000, For direct Tension, the lap length shall be 2Ld that is development length or 30d whichever is greater is considered. (d- diameter of the bar). In Compression, lap length should not be less than 24D. The straight length of lapping bar shall not be less than 15d or 20 cm.

 Development Length (Ld) is the length of bar required to transfer load or stress from steel to concrete.Generally Development length is 41d.

Anchorage Length is provided if sufficient development length can not be able to be provided inside the support/fixed end.

48. Guniting

It is a process in which mixture of cement & sand in proportion of 1:3 is shot on concrete surface with the help of cement gun uder pressure of 2 to 3 kg/cm2. It is a highly effective process for repairing concrete walls or damaged surfaces.

49. Grouting

It is the process of injecting the Grout into cavities or cracks in concrete, masonry, soil and rocks.      Different materials of Grout are Cement Grouting, Chemicals Grouting, Bentonite Grouting, Resin?Epoxy Grouting and Bituminous Grouting.

50. Flashing

Flashing is an extended construction that is done to seal and protects joints in a building from water penetration. Flashing is installed at the intersecting roofs, walls and parapets.

51. Expansion Joint

In buildings, an expansion joint is a mid-structure seperation designed to relieve stress on building materials caused by building movement induced by thermal expansion and contraction caused by temperature changes, sway caused by wind, seismic events.

As per IS 3414, which is specific code for joints, structures exceeding 30m length are designed with one or more expansion joints.