Concrete Technology
Cement
Which chemical compostion has highest content in OPC?
a) Alumina
b) Silica
c) Lime
d) Iron Oxide
Explanation: Lime forms nearly two-third (2/3) of the cement. Therefore sufficient quantity of the lime must be in the raw materials for the manufacturing of cement.
Excess in lime causes _______
a) The cement to shrink and integrate
b) The cement to shrink and disintegrate
c) The cement to expand and integrate
d) The cement to expand and disintegrate
Explanation: Sufficient quantity of lime forms di-calcium silicate (C2SiO2) and tri-calcium silicate in the manufacturing of cement.
Silica in excess causes ________
a) The cement to set slowly
b) The cement to set quickly
c) The cement to expand
d) The cement to disintegrate
Explanation: Silica gives strength to the cement. Silica in excess causes the cement to set slowly.
Alumina in excess causes _________
a) Reduces the strength of the cement
b) Inceases the strength of the cement
c) No change
d) Sometimes increase or decrease the strength of the cement
Explanation: Alumina supports to set quickly to the cement. It also lowers the clinkering temperature. Alumina in excess reduces the strength of the cement.
Which compound gives the colour to the cement?
a) Lime
b) Silica
c) Iron Oxide
d) Alumina
Explanation: Iron oxide pigments are in the form of particles ranging approximately from 0.1 to 1.0 micron. The difference in color between one pigment and another is due to the shape and surface structure of the particle.
Which cement contains high percentage of C3S and less percentage of C2S?
a) Rapid Hardening Cement
b) Ordinary Portland Cement
c) Quick Setting Cement
d) Low Heat Cement
Explanation: This cement contains high percentage of C3S and less percentage of C3S. This is infact high early strength cement.
When concrete is to be laid under water ___________ is to used.
a) Rapid Hardening Cement
b) Ordinary Portland Cement
c) Quick Setting Cement
d) Low Heat Cement
Explanation: When concrete is to be laid under water, quick setting cement is to used. This cement is manufactured by adding small percentage of aluminum sulphate (Al2SO4) which accelerates the setting action.
Which of the following is correct for Low Heat Cement?
a) Suitable for use in cold weather areas
b) Heat of hydration is reduced by tri calcium aluminate content
c) This cement requires longer period of curing
d) This cement contains high aluminate %age usually between 35-55%.
Explanation: In this cement the heat of hydration is reduced by tri calcium aluminate content. It contains less percentage of lime than ordinary port land cement. It is used for mass concrete works such as dams etc.
Which cement is used in sewage and water treatment plants?
a) Rapid Hardening Cement
b) Low Heat Cement
c) Sulphate Resisting Cement
d) Quick Setting Cement
Explanation: Cement with composition has very good resistance to sulphate attack. This type of cement is used in the construction of foundation in soil where subsoil contains very high proportions of sulphate.
Which cement is used for mainly building construction where strength required with age?
a) Rapid Hardening Cement
b) Low Heat Cement
c) Portland Pozzolana Cement
d) Quick Setting Cement
Explanation: It gains very high compressive strength with age unlike other cement and it is very cheap and affordable.
Which cement is used for artificial marble?
a) Rapid Hardening Cement
b) Sulphate Resisting Cement
c) Coloured Cement
d) Quick Setting Cement
Explanation: As the name suggests, it is used where coloured cement required for any aesthetic purposes.
Which cement is used to create bond with old concrete surface?
a) Rapid Hardening Cement
b) Expansive Cement
c) Sulphate Resisting Cement
d) Low Heat Cement
Explanation: As the name suggests, it expands and increases in volume while settled. It is used to avoid shrinkage of concrete.
Which cement is used to store for longer duration in wet climatic conditions?
a) Expansive Cement
b) Ordinary Portland cement
c) Hydrophobic Cement
d) Quick Setting Cement
Explanation: This type of cement is manufactured by mixing admixtures like petrolatum, napthalene soap which forms layer and act as water repellent.
Which cement used in frost resistance concrete?
a) OPC
b) PPC
c) AEC
d) QSC
Explanation: It is used to fill up the gap in concrete which are produced by excessive amount of water during casting (later evaporated and leave the gap).
Which cement is used for the construction of water-retaining structure like tanks, reservoirs, retaining walls, swimming pools, dams, bridges, piers etc?
a) Waterproof Portland cement
b) Colored Cement
c) High Alumina Cement
d) Low Heat Cement
Explanation: This cement is prepared by mixing with OPC or rapid hardening cement with a small percentage of some metal stearates at the time of mixing.
____ cement is used for formwork that can be removed earlier and reused in other areas which save the cost of formwork.
a) Rapid Hardening Cement
b) Colored Cement
c) High Alumina Cement
d) Low Heat Cement
Explanation: Rapid hardening cement is used where the formwork can be removed earlier and reused in other areas which save the cost of formwork. This cement can be used in prefabricated concrete construction, road works, etc.
Which cement is mainly used for interior and exterior decorative works?
a) Rapid Hardening Cement
b) Colored Cement
c) High Alumina Cement
d) Low Heat Cement
Explanation: This Cement is produced by adding 5- 10% mineral pigments with Portland cement during the time of grinding.
Which cement is used for works economic where considerations is predominant?
Reservoirs, retaining walls, swimming pools, dams, bridges, piers etc.
a) Waterproof Portland Cement
b) Colored Cement
c) High Alumina Cement
d) Blast Furnace Slag Cement
Explanation: It is obtained by grinding the clinkers with about 60% slag and resembles more or less in properties of Portland cement.
How many times in each layer of concrete rodded in a slump cone?
a) 75
b) 25
c) 12 to 15
d) 35 to 65
Explanation: Each time, each layer is tamped 25 times with a 2 ft (600 mm)-long bullet-nosed metal rod measuring 5/8 in (16 mm) in diameter.
How many layers of concrete are placed to fill a slump cone?
a) 5 layers
b) 3 equal layers by volume
c) 3 equal layers by height
d) 5 layers by volume
Explanation: Fill the mold 12 inches high in the shape of the frustum of a cone that is 8 inches in diameter at the bottom and 4 inches in diameter at the top. Then fill it in three equal layers by volume, not by height.
To measure the concrete temperature, the stem of the thermometer must be kept by at least ___ inches of concrete.
a) 1
b) 2
c) 3
d) 4
Explanation: The stem of the thermometer should be surrounded by at least 3 inches of the concrete for better reading.
In the soundness test a specimen of hardened cement paste is ___ for a fixed time.
a) Freeze
b) Dry
c) Boiled
d) Dipped in water
Explanation: A specimen of hardened cement paste is boiled for a fixed time so that if there is any tendency of increase or decrease in size can be detected.
If L1=Measurement taken after 24 hours of immersion in water at a temp. of 27 ± 20oC and L2=Measurement taken after 3 hours of immersion in water at boiling temperature. Then what is soundness of cement?
a) L1+L2
b) L1/L2
c) L1-L2
d) L1*L2
Explanation: L1-L2 is the formula to calculate the soundness of cement. First take the reading after immersion in water then measure it after 3 hours of immersion in boiling water.
To determine the fineness of cement ____
a) Grain size is smaller than specified mesh size
b) Grain size is larger than specified mesh size
c) Grain size is equal to specified mesh size
d) Grain size is 1mm
Explanation: To determine the fineness of cement by dry sieving as per IS: 4031 (Part 1) – 1996. The principle of this is that we determine the proportion of cement whose grain size is larger than the specified mesh size.
The apparatus used are ___ IS Sieve, Balance capable of weighing 10g to the nearest 10mg.
a) 90μm
b) 45μm
c) 22.5μm
d) 14μm
Explanation: The apparatus used are 90μm IS Sieve, Balance capable of weighing 10g to the nearest 10mg, A nylon or pure bristle brush, preferably with 25 to 40mm, bristle, for cleaning the sieve.
What is the amount of water required to give the paste normal consistency for consistency test?
a) .78 times
b) .79 times
c) .77 times
d) .76 times
Explanation: Prepare a paste by adding 0.78 times the water required to give a paste of standard consistency (i.e. 0.78P).
Which apparatus is generally used to measure the soundness of the cement?
a) Vicat Apparatus
b) Le-Chatelier apparatus
c) Soundness meter
d) Duff Abrams apparatus
Explanation: The apparatus for conducting the Le-Chatelier test should conform to IS: 5514 – 1969. Balance, whose permissible variation at a load of 1000g should be +1.0g and Water bath.