The approximate value of shrinkage strain for concrete is taken as
A. 0.0003
B. 3e-05
C. 0.0004
D. 4e-05
The minimum grade of RCC concrete to be used when it is exposed to sea water is
A. M20
B. M25
C. M30
D. M35
Nominal Mix of concrete is used upto which grade?
A. M15
B. M20
C. M25
D. M30
The stripping of formwork form the vertical faces of beam is done after
A. 16-24 hrs
B. 2 days
C. 7 days
D. 14 days
The cube strength of concrete is
A. More by 1.25 times that of cylinder for same grade
B. Equal to the cylinder strength
C. Less by 1.25 times that of cylinder for same grade
D. None of above
In the zone of anchorages in prestressed concrete the material preferred to minimize costs is __________
A. High strength steel
B. High strength bar
C. High strength tendons
D. High strength concrete
In order to obtain the best workability of concrete, the preferred shape of the aggregate is:
A. oblong
B. rounded
C. angular
D. elongated
The concrete strength decreases with increase in
A. moisture content
B. water cement ratio
C. aggregate size
Note: The supplied key identifies C, but increasing the water-cement ratio also generally reduces concrete strength when other conditions are comparable.
D. aggregate cement ratio
The aggregate which pass through 4.75 mm IS sieve and entirely retain on 75 micron IS sieve is known as:
A. coarse aggregate
B. all in aggregate
C. fine aggregate
D. cyclopean aggregate
A form of segregation of concrete in which some of the water scum size to the surface of freshly placed concrete
A. creeping
B. bleeding
C. bulking
D. water absorption
In a pre-stressed member it is advisable to use
A. low strength concrete only
B. high strength concrete only
C. low strength concrete but high tensile steel
D. high strength concrete and high tensile steel
Most common method of prestressing used in factory production is
A. Long line method
B. Freyssinet system
C. Magnel-Blaton System
D. Lee-Macall System
Use of rounded stones instead of angular stones druing slump test would result in
A. greater slump
B. equal slump
C. lesser slump
D. no specific result
The process of mixing, tranportating, placing and compacting concrete using ordinary portland cement should not take kore than
A. 30 minutes
B. 40 minutes
C. 60 minutes
D. 75 minutes
Which of the following chemical should be added to reduce the curing time of concrete?
A. sodium chloride
B. calcium chloride
C. potassium
D. magnesium
The purpose of reinforcement in prestressed concrete is
A. to provide adequate bond stress
B. to resist tensile tsress
C. to impart initial compressive stress in concrete
D. all of above
The sand that required higher water content lies in
A. Zone I
B. Zone II
C. Zone III
D. Zone IV
The modulus of elasticity of concrete improved with
A. decreasing in curing period
B. better compaction
C. higher water cement ratio
D. age
The standard specimen used for testing the compressive strength of concrete in most codes is a cube of size
A. 100 x 100 x 100 mm
B. 150 x 150 x 150 mm
C. 200 x 200 x 200 mm
D. 300 x 300 x 300 mm
Curing of concrete is carried out mainly to
A. reduce its self-weight
B. provide adequate moisture for continued hydration of cement
C. increase its workability
D. reduce the cement content required
As per common RCC design practice, the minimum grade of concrete recommended for reinforced concrete work is
A. M10
B. M15
C. M20
D. M25
The slump test on fresh concrete is used to assess its
A. compressive strength
B. workability
C. setting time
D. long-term durability
Segregation in concrete refers to
A. uniform distribution of aggregates throughout the mix
B. separation of coarse aggregate from the mortar matrix
C. proper compaction of the mix
D. excess entrainment of air
The curing of concrete means:
A. spraying of air over concrete
B. spraying of sand over concrete
C. spraying of water over concrete
D. all of the above
Dropping of concrete would cause:
A. disintegration
B. splitting
C. segregation
D. bleeding
Curing of concrete at high temperature results in:
A. increase in ultimate strength
B. decrease in ultimate strength
C. cracking of concrete
D. early development of ultimate strength
Disadvantage of very high strength concrete are:
A. low compressive strength
B. uneconomical
C. low shear strength
D. low shear strength along with increased creep and shrinkage
The maximum quantity of aggregate per 50 kg of cement should not exceed:
A. 100 kg
B. 200 kg
C. 350 kg
D. 450 kg
The workability of concrete can be improved by:
A. more sand
B. more cement
C. more fine aggregate
D. fineness of coarse aggregate
Curing time for concrete can be reduced by the use of:
A. aluminium
B. calcium chloride
C. common salt
D. sugar
The flexural strength of concrete is determined by means of a
A. beam test
B. cube test
C. slump test
D. shear test
The separation of coarse aggregate from the mortar matrix in fresh concrete is termed:
A. bleeding
B. segregation
C. laitance
D. honeycombing
For good quality structural concrete, the water-cement ratio is generally kept within the range of:
A. 0.2 - 0.3
B. 0.4 - 0.6
C. 0.7 - 0.9
D. 1.0 - 1.2
Which of the following admixtures is used to accelerate the setting of concrete?
A. calcium chloride
B. fly ash
C. air-entraining agent
D. retarder
The standard age of curing at which the characteristic compressive strength of concrete is normally tested is:
A. 3 days
B. 7 days
C. 28 days
D. 56 days
Honeycombing in a concrete member is mainly caused due to:
A. excess cement content
B. improper compaction
C. use of coarse sand
D. low water content
A 'cold joint' in a concrete member forms when:
A. fresh concrete is placed against already-set concrete after an undue delay
B. concrete is vibrated excessively
C. a low-temperature admixture is used
D. concrete is cast during cold weather
An over-reinforced concrete beam typically fails by:
A. ductile yielding of steel followed by gradual failure
B. shear failure only
C. bond failure only
D. sudden, brittle crushing of concrete before steel yields
Self-compacting concrete achieves compaction mainly through:
A. heat curing
B. manual tamping
C. its own high flowability under gravity, without vibration
D. external mechanical vibration
The durability of concrete structures in a marine environment is governed mainly by:
A. permeability of concrete and adequate cover to reinforcement
B. colour of the aggregate used
C. compressive strength alone
D. fineness of the sand used
'Autogenous healing' of concrete refers to:
A. gradual self-sealing of minor cracks over time due to continued hydration
B. self-compaction of fresh concrete
C. self-destruction of concrete due to shrinkage
D. automatic curing without the use of water
The cube strength of concrete used for prestressed member should not be less than
A. 10Mpa
B. 25Mpa
C. 35Mpa
D. 40Mpa
Modulus of elasticity of concrete improves by
A. age
B. High water cement ratio
C. shorter curing period
D. all of above
Higher workability of concrete is required if the structure is
A. made with cement concrete
B. thick reinforced
C. thin and heavily reinforced
D. thick and heavily reinforced
For the same design load, the weight of concrete in pre stressed concrete as compared to ordinary concrete can be reduced by
A. 0.1
B. 0.2
C. 0.3
D. 0.5