326. If the average compressive strength is 4000 kg / cm² and standard deviation is 500 , the co – efficient of variation is
a ) 10 %
b ) 12.5 %
c ) 15 %
d ) 18.5 %
327. The risk of segregation is more for
a ) water mix
b ) larger proportion of maximum size
c ) coarser grading
d ) all of the above
328. The process by which fresh cement concrete is compacted to remove the air bubbles is known as
a ) compaction
b) wetting
c ) placing
d) consolidation
329. Maturity of concrete means
a ) oldness of concrete
b ) strength of concrete
c ) sum of product of temperature & time
d ) none of the above
330. Gypsum is used as admixture in concrete to increase the property of concrete
a ) accelerator
b ) retarder
c ) water proofer
d ) none of the above
331. Calcium chloride is used as admixture in concret e to increase the property , of concrete
a ) accelerator
b) retarder
c ) water proofer
d ) none of the above
332. Calcium chloride as an recommended for use with
a ) ordinary portland cement
b) high alumina cement
c ) rapid hardening cement
d) none of the above
333. To improve the certain properties of concrete , admixture is used in concrete at the time of
a) grading of cement
b ) mixing of concrete
c) after pouring of concrete
d) none of the above
334. An admixture
a ) is a basic ingredient of concrete
b ) offers improvement not economically attained by adjusting mix proportions
c ) is a substitute for good concreting practice
d ) is beneficial to the properties of concrete when used in large quantities
335. An admixture could be used to
a ) accelerate initial setting of concrete
b ) increase strength of concrete
c ) improve workability
d ) all of the above
336. An accelerator shortens all of the following except
a ) setting time
b ) period of curing
c ) strength of concrete
d ) period of removal of formwork
337. Addition of retarder to concrete decreases all of the following except
a ) rate of hydration
b ) water – cement ratio
c ) workability and compressive strength
d ) rate of development of strength
338. Pick up the incorrect statement from the following :
a ) admixtures accelerate hydration
b ) admixtures make concrete water proof
c ) admixtures make concrete acid proof
d ) admixtures give high strength
e ) none of the above
339. Gel space ratio is defined as the ratio of
a ) volume of hydrated cement to the sum of volume of hydrated cement and capillary pores
b ) the sum of volume of hydrated ceme nt and capillary pores to volume of hydrated cement
c ) both (a ) and (b ) of above
d ) none of the above
340. Find the gel space ratio of concrete with following data : cement = 50 kg , Weight of water = 20 kg
a ) 0.85
b ) 0.91
c ) 0.96
d ) 0.99
341. The minimum grade of high strength concrete is
a ) M25
b ) M40
c ) M50
d ) M60
342. The type of aggregates not suitable for high strength concrete and for pavements subjected to tension , is
a ) rounded aggregate
b ) irregular aggregate
c ) angular aggregate
d ) flaky aggregate
343. The aggregate used for high strength concrete is
a ) round aggregate
b ) irregular aggregate
c ) angular aggregate
d ) all of the above
344. To obtain a very high strength concrete , use very fine grained
a ) granite
b ) magnetite
c ) barite
d ) pumice
345. Prestress is imparted to concrete by bearing in
a ) pre tensioning
b ) post tensioning
c ) both ( a ) and ( b ) of above
d ) none of the above
346. The minimum grade of concrete for pre – tensioned member is
a ) M15
b ) M20
c ) M25
d ) M40
347. The mix proportion of cement mortar to be used in the joints in the precast prestressed member is
a ) 1 : 1
b) 1:1.5
c ) 1 : 2
d) 1:2.5
348. The diameter of high tensile steel tendons used is
a ) 3 mm to 5 mm
b ) 5 mm to 8 mm
c ) 6 mm to 9 mm
d ) 8 mm to 12 mm
349. The minimum clear spacing for single wires used in pre tension system is
a ) 2 times the diameter of the wire and max . size of aggregate whichever is greater.
b ) 3 times the diameter of the wire and max . size of aggregate whichever is greater
c ) 2 times the diameter of the wire and 1.5 times max . size of aggregate whichever is greater
d ) 3 times the diameter of the wire and 1.5 times max . size of aggregate whichever is greater
350. The minimum clear spacing of non – grouped cables or large bars shall be
a ) 40 mm
b ) maximum size of cable or bar
c ) 5 mm plus maximum size of aggregate
d ) greater of ( a ) , ( b ) and ( c ) of above
