CONCRETE TECHNOLOGY & Structural analysis QUESTIONS:

1- Purpose of concrete curing:

To avoid the evaporation of the water from concrete and to keep moisture inside to

maintain the durability of the concrete

2- What is concrete workability:

The ease of fresh concrete which can be Mixed, placed, and compacted fully over the

formwork

3- What is the core test of concrete and when it is applied?

Core test is a destructive test done for concrete after 28 days usually done if there is any doubt of the compressive strength of concrete

4- What is the density of water?

1000 kg/m3

5- Why are admixtures added to the concrete?

To increase the durability & strength of concrete and some time for increasing the

workability

6- When we remove the shutter of columns?

After minimum 2 days

7- When we remove the shutter of sides beam or foundation?

It can be removed after 1 day

8- When we remove the shutter of normal slab?

After minimum 14 days

9- How many cubes required for 110 m3 of concrete in one day?

Total of 9 cubes: 3 to do compressive strength after 7 days

3 after 28 days

3 extra cubes

10- Definition of hydration:

It is the reaction between water and cement

11- What is the length of the CG of compression and CG of a tension member?

Effective depth

12- Definition of water cement ratio:

Weight of water over the weight of Cementous components or cement

13- What is the minimum thickness of a structural member?

15 cm

14- Techniques used for beam repair.

Steel plate; carbo fiber cover; fiber road; shipping, cleaning of steel and casting microconcrete high strength

15- Most used of slabs.

a- Hollow slab

b- Solid slab

c- Post tension slab

d- Flat slab

e- Prestressed slab

16- When is shotcrete used?

a- Difficulty of placing a shutter for members

b- Pool walls

c- Tunnels

d- Curve member

17- When OPC & SRC are used?

OPC for superstructure

SRC for substructure or for member exposed to soil

18- Density of cement.

1440 kg/m3

19- Density of concrete

2500 kg/m3

20- Definition of concrete durability.

Capability of concrete to resist weathering condition like chloride, chemical attack, and

abrasion

21- Till when the curing should continue?

Till minimum 7 days till the concrete reach 70% of its strength

22- Refer to sampling test in BS 12350-1;2009. Standard term “increment” Is

defined as:

Quantity of concrete taken by single operation of a scoop or similar devices

23- After demolding of cubes, cubes shall be cured immediately before testing in

water at temperature of chamber:

20+- 2 at humidity larger than 95%

24- The minimum allowable capacity of the measuring container used in air content

test is:

5 liters

25- Refer to flow table test, leveling each layer by tamping lightly done for how

many times?

10 times

26- The flow table test values results are reported to the nearest.

10 mm

27- Slump test is used to measure.

Consistency of concrete

28- Refer to density test, the standard specifies the method for determining the

density of compacted fresh concrete is.

BS-EN-12350-1;2009

29- For temperature Test, concrete containing aggregate size larger than 75mm may

require how much time for transfer of heat from aggregate to mortar?

20 mins

30- What is the maximum % of reinforcement of beam?

4%

31- What is the minimum % of reinforcement for beam as BS 8110-97?

0.8 %

32-Wind load test taken from wind for regular building if height more than?

120 meters

33- Modification factor of PT Slab:

0.5

34- the deflection for beam span is:

5Wl4/384 EI

35- Nominal tensile strength for post tension tendons is:

1860 MPa

36- Density of light weight concrete:

Between 800 to 1800 kg/m3

37- What is the poison ratio of concrete?

0.2

38- what is the poison ration of steel structure

0.3

39- Es of steel structure is:

205000 MPa

40- Es of concrete

30000 Mpa

41- Minimum vertical reinforcement in walls is:

0.04 %

42- Minimum vertical reinforcement of columns is:

1%

43- Mechanical splice (min 50 diameter) may be used after demonstrating that splice

can develop:

125% of the specified yield strength of the bar

44- the maximum deflection for cantilever beam under uniform load is:

Wl4/ 8 EI

46- As per DIN 1048 Standard, water penetration at 28 days test should not exceed

maximum of:

10 mm

47- As per ASTM C 1202 the rapid chloride penetration test at 28 days for RC pile

should not exceed:

1200 Columbus

48- As per ACI 318-4 the maximum allowable elongation in post tension tendons is:

7%

49- maximum spacing for PT tendons as per ACI 318-05 IS:

8 THICKNESS OF SLAB or 5 ft

50- Maximum acceptable settlement for the piles under working load:

8mm

51- the normal consistency of Portland cement is

25.35 %

52- the Modulus of elasticity of normal concrete is

4700 √f’c N/mm2

53- in post tension the maximum number of strands used per tendons is

5

54- For external walls of building whose U value should be 0.52 w/m2*k, the

thickness of polystyrene should be:

60 mm

55- cover for structural members:

a- Columns & beams 30 mm

b- Foundation 50 mm

c- Pile and exposed to soil 70 mm

56- maximum settlement of raft foundation is

50 mm

57- maximum settlement of isolated footing is

30 mm

58- maximum steel in strap footing is located at?

Top

59- overlap of steel of continues beam done at:

Mid third span at bottom and middle span for top

60- The concrete used for structural purpose shall have compressive strength not

less than:

Minimum Fcu 35 N.mm2 for post tension minimum Fcu 40 N/mm2

61- shear & moment diagram

62- design lifetime of structure:

63- Concrete combination design:

64- Reinforcement details for PT slabs

65- precast slab connection details:

66- deflection of beam and slabs

67- crack width limit:

Wk= Hd/Hw = hydro static pressure of water / wall thickness

For structure exposed to water:

If Hd/Hw> 5 wk= 0.2 mm

If Hd/Hw>35 wk= 0.05 mm

For structure not exposed to water:

Wk= 0.3 mm

For pile

Wk=0.1 mm

68- Combo waterproof detail: