• Vicat needle is used in determination of(a) initial setting time(b) final setting time(c) consistency(d)both (a) and (b)

• In Vicat test, the final setting is assumed when the attachment of the needle fails to make any impression on the mould but the needle

(a) Penetrates the sample by 5 mm(b) makes just an impression on the sample(c) does not penetrate the sample(d) pierce the sample by 10 mm

Initial setting time of cement should not be less than(a) 15 minutes

(b) 30 minutes(c) 28 minutes(d)1 hour (IES 1992)

Final setting time of cement should not be more than(a) 1 hour(b) 2 hours(c) 5 hours(d) 10 hours

• Which of the following pairs in respect of ordinary Portland cement are correctly matched?

1. Initial setting time……30 min.2. Final setting time…….10 hours3. Normal consistency……..10%

Select the correct answer using the codes given below(a) 1,2 and 3

(b) 2 and 3(c) 1 and 2(d) 1 and 3 (IES 1997)

• The ability of cement to maintain a constant volume is called(a) flashing(b) honeycombing(c) soundness(d)Creep

• Soundness test of cement is done to determine its(a) durability in sea water(b) free lime content(c) iron oxide content(d) alumina content (IES 1994)

Ans- CAns- A

Honeycombs are hollow spaces and cavities left in concrete mass on surface or inside the concrete mass where concrete could not reach. These look like honey bees nest.

Flash set - concrete stiffens quickly and is difficult to place, consolidate, and finish If inadequate amounts of gypsum are added to the cement, flash set can occur

Soundness means the ability to resist volume expansion.

• Soundness of cement is tested by(a) Vicat apparatus(b) Le Chatalier apparatus(c) soundness meter(d)Duff Abrams apparatus

• In the soundness test, the whole assembly is immersed in water at a temperature of

(a) 19 ± 10 degree C(b) 27 ± 10 degree C(c) 37 ± 10 degree C(d)47 ± 10 degree C

• In the soundness test, the whole assembly is immersed in water for(a) 30 minutes(b) 1 hour(c) 24 hours(d) 48 hours

• Sulphate resisting cement is useful in structures(a) in river waters(b) sea waters(c) in cold environment(d)in hot environment

• In white Portland cement manufacturing(a) china clay is used(b) oil is used as a fuel(c) raw material contains very little manganese and iron(d)all these

• Pozzolana contains(a) silica(b) alumina(c) both (a) and (b)(d) neither (a) nor (b)

Ans-bAns-aAns-c

• For given water content, workability decreases if the concrete aggregates contain an excess of

1. Thin particles2. Flat particles3. Elongated particles4. Flaky particles5. All of the above

• For ensuring quality of concrete, use

1. single sized aggregates2. two sized aggregate3. graded aggregates4. Coarse aggregates.

• The maximum size of coarse aggregate for the concrete in a column of size 400 x 400 mm should be

(a) 40 mm(b) 35 mm(c) 25 mm(d)20 mm (AMIE June99)

• As the size of coarse aggregate decreases, the workability of concrete

(a) decreases(b) increases(c) first increases then decreases(d) first decreases then increases

(IES 1992)

Ans- dAns a

• Workability of concrete is inverselyproportional to :

a. time of transit

b. water-cement ratio

c. the air in the mix

d. size of aggregate

Ans- A

Factors affecting workability:1.Water content in the concrete mix2.Amount of cement & its Properties3.Aggregate Grading (Size Distribution)4.Nature of Aggregate Particles (Shape, Surface Texture, Porosity etc.)5.Temperature of the concrete mix

• The property of fresh concrete, in which the water in the mix tends to rise to the surface while placing and compacting, is called:

a) Segregationb) bleedingc) bulkingd) Creep

• The risk of segregation is more for:A. wetter mixB. larger proportion of maximum size aggregateC. coarser gradingD. all the above.

Ans- bAns- d

The volume increase of fine aggregate due to presence of moisture content is known as bulking.

Concrete creep is defined as: deformation of structure under sustained load. It is a long term effect.

• Select the incorrect statementa) Lean mixes bleed more as compared to rich ones.b) Bleeding can be minimized by adding pozzolona finer

aggregate.c) Bleeding can be decreased by addition 'of calcium

chloride.d) none of the above

Ans- d

• To determine the modulus of rupture, the size of test specimen used is

a)150 x150 x500 mmb) 100 x100 x700 mmc) 150 x150 x700 mmd) 100 x100 x500 mm

Ans: c

Modulus of Rupture, frequently abbreviated as MOR, (sometimes referred to as bending strength or FLEXURAL STRENGTH), is a measure of a specimen's strength before rupture.

COMPRESSIVE STRENGTH- Cube (150x150x150mm)

SPLIT TENSILE STRENGTH- Cylinders (300x150mm dia)

FLEXURAL STRENGTH- Beams or Prisms (150x150x700mm)

• The effect of adding calcium chloride in concrete is

i)to increase shrinkageii)to decrease shrinkageiii)to increase setting timeiv)to decrease setting timeThe correct answer isA. (i) and (iii)B. (i)and(iv)C. (ii) and (iii)D. (ii) and (iv)

Ans- b

Addition of calcium chloride• Improves workability• Reduces bleeding...this is due to the early

stiffening produced by acceleration and allows earlier final finishing.

Bulking of sand is directly related toA. Moisture contentB. Air entrainmentC. Both A and BD. None of the above

Ans- b

The bulking of sand is largely depends on• grain size – Small the grain size, larger

will be bulking effect and vice versa.• moisture content – 5 – 8 % moisture can

result in 20-35 % increase in volume

• How many times is each layer of concrete roddedin a slump cone?

a.75b.25c.12 to 15

• How many layers are placed to fill a slump cone?a.5 layersb.3 equal layers by volumec.3 equal layers by height

• Wp and Wf are the weights of a cylinder containing partially compacted and fully compacted concrete. If the compaction factor is 0.95, the workability of concrete is

A. extremely lowB. very lowC. lowD. highE. none of these.

Ans- d

Compaction factor is the ratio of the weight of fresh, partially compacted concrete/ to fully compacted concrete.

Theoretically the maximum value is 1.0, nearer the value higher is the workability

M10 grade of concrete approximates

A. 1 : 3 : 6 mixB. 1 : 1 : 2 mixC. 1 : 2 : 4 mixD. 1 : 1.5 : 3 mixE. none of these.

Ans-aM 5- 1:5:10M7.5- 1:4:8M10- 1:3:6M15- 1:2:4

M20- 1:1.5:3M25- 1:1:2