251 , Workability of concrete may be improved by adding
a) air entering agent
b ) foaming agent
c) oily agent
d ) aluminium compound
e) all of the above
252. Workability of concrete is directly proportional to
a ) grading of the aggregate
b ) time of transit
c ) aggregate cement ratio
d ) none of the above
253. Workability of concrete is inversely proportional to
a ) grading of the aggregate
b ) time of transit
c ) aggregate cement ratio
d ) none of the above
254. The shrinkage of concrete
a ) is proportional to water content in the mix
b ) is proportional to cement concrete
c ) increases with age of concrete
d ) all of the above
255. Addition of pozzolana to cement causes
a ) reduction in permeability
b ) loss of heat of hydration
c) reduction in bleeding
d ) increase in curing time
e ) all of the above
256. For a good concrete
a ) aggregates should be hard and durable
b ) cement should be sufficient to produce the required strength
c ) water should be free form organic material
d ) mixing of ingredients should be done thoroughly so as to produce homogeneity
e ) all of the above
257. For the construction of RCC slab , column , beam and walls , the minimum grade of concrete mixed is used for
a ) 1 : 3 : 6
b ) 1 : 1 : 2
c ) 1 : 1.5 : 3
d ) 1 : 2 : 4
258. M100 grade of concrete approximates
a ) 1 : 3 : 6
b ) 1 : 1 : 2
c ) 1 : 2 : 4
d ) 1 : 1.5 : 3
259. M150 grade of concrete approximates
a ) 1 : 3 : 6
b ) 1 : 1 : 2
c ) 1 : 2 : 4
d ) 1 : 1.5 : 3
260. Strength of concrete with passage of time
a ) increases
b ) decreases
c ) fluctuates
d ) remains constants
261. Concrete gains strength due to
a ) chemical reaction of cement with sand and coarse aggregates
b ) evaporation of water from concrete
c ) hydration of cement
d ) all of the above
262. The nature of fresh concrete is
a ) elastic
b ) plastic
c ) rigid
d ) all of the above
263. Too wet concrete may cause
a ) weakness of concrete
b) excessive laitance
c ) segregation
d) lower density
e ) all of the above
264. The process of proper and accurate measurement of concrete ingredients for uniformity of proportion , is known
a ) grading
b ) curing
c ) mixing
d ) batching
265. Proper batching ensures
a ) economy
b ) durability
c ) workability
d ) strength
e ) all of above
266. Batching error means inaccuracy in the quantity of
b ) cement
a ) aggregates
c ) water
d ) all of the above
267. In the batching of materials , the ingredients should be measured to a tolerance ( as a percentage of batch quantity ) of
a ) ± 1.0
b ) ± 2.0
c ) ± 3.0
d ) ± 4.0
268. The process of mixing some mortar in the mixer at the beginning of the first batch concrete mixing is called
a ) buttering
b ) borrowing
c ) initiating
d ) accelerating
269. During manufacture of concrete minimum period for which mixing is done in mixer for manufactured / crushed aggregate is ( IS 456 : 2000 )
a ) 1 min
b) 1.5 min
c ) 2 min
d) 2.5 min
270. The concrete mixers are normally classified on the basis of
a ) the technique of discharging the mixed concrete
b ) capacity of batch handled
c ) the number of drums
d ) all of the above
271. The capacity of concrete mixer is expressed in terms of
a ) total volume of concrete produced per day
b ) total volu me of concrete produced in 8 hrs
c ) total volume of concrete produced per hr
d ) volume of concrete mix handled per batch
272. The objective of mixing concrete materials are the following except
a ) coat the surface of all aggregate particles with cement paste
b ) blend all the ingredients into a uniform mass
c ) obtain concrete of uniform colour and grading
d ) obtain concrete of desired workability
273. Pick up the correct statement from the following :
a ) The weight of ingredients of concrete mix , is taken in kilograms
b ) water and aggregates is measured in liters
c ) the finished concrete is measured in cubic metres
d ) 20 bags of cement make one tonne
e ) all of the above
274. For batching 1 : 3 : 6 and water cement ratio 0.6 both by weight , the quantity of water required per bag , is
a ) 10 kg
b ) 15 kg
c ) 20 kg
d ) 30 kg
275. For batching 1 : 3 : 6 concrete mix by volume , the ingredients required per bag for 50kg cement are
a ) 70 liters of sand 120 liters of aggregates
b ) 70 kg of sand 140 liters of aggregates
c ) 105 liters of sand and 140 liters of aggregates
d ) 105 liters of sand and 210 liters of aggregates