## Design & Technology of Concrete Structures Civil Engineering Questions and Answers Part-4

This is the civil engineering questions and answers section on Concrete Structures Design with explanation for various interview questions…

## Design & Technology of Concrete Structures

151. Prestressing losses in post-tensioned and pre-tensioned beams are respectively
a) 15% and 20%
b) 20% and 15%
c) 15% and 15%
d) 20% and 20%

152. In concrete, use of angular crushed aggregate in place of natural rounded gravel affects
a) direct tensile strength
b) split tensile strength
c) flexural tensile strength
d) compressive strength

153. Ratio of compressive strength to tensile strength of concrete
a) increases with age
b) decreases with age
c) remains constant
d) none of the above

154. According to Indian Standards, the grad¬ing of fine aggregates is divided into
a) two zones
b) three zones
c) four zones
d) five zones

155. Assertion A : Lightweight concrete exhi¬bits higher shrinkage than normal weight concrete.
Reason R : Modulus of elasticity of light-weight concrete is lower, than that of normal weight concrete. Select your answer according to the coding system given below :
a) Both A and R are true and R is the correct explanation of A
b) Both A.and R are true but R is not the correct explanation of A
c) A is true but R is false
d) A is false but R is true

156. Endurance limit of mild steel is approximately equal to,
a) 0.3
b) 0.5
c) 0.7
d) 0.8
Endurance limit is defined as the maxi-mum value of the ratio of maximum stress to short time static strength, below which no failure occurs.

157. With the increase in rate of loading during testing, compressive strength of concrete
a) increases
b) decreases
c) remains same
d) none of the above

158. For a given aggregate content, increasing the water-cement ratio in concrete
a) increases shrinkage
b) decreases shrinkage
c) does not change shrinkage
d) none of the above

159. Assertion A : The net loss of strength due to air entrainment of a richer mix is higher than that of a leaner mix. Reason R : Effect of air entrainment on improving workability is smaller in richer mix than in a leaner mix. Select your answer based on the coding system given below
a) Both A and R are true and R is the correct explanation of A
b) Both A and R are true but R is not the correct explanation of A
c) A is true but R is false
d) A is false but R is true

160. The bond strength between steel rein-forcement and concrete is affected by i) steel properties ii) concrete properties iii) shrinkage of concrete The correct answer is
a) (i) and (ii)
b) (ii) and (iii)
c) (i) and (iii)
d) (i), (ii) and (iii)

161. The bond strength between steel and concrete is due to
a) friction
d) none of the above

162. Impact strength of concrete increases by using
i) smaller maximum size of aggregate
ii) aggregate with high modulus of elasticity
iii) aggregate with low poisson’s ratio The correct answer is
a) (i) and (ii)
b) (ii) and (iii)
c) (i) and (iii)
d) (i), (ii) and (iii)

163. Impact strength of concrete is greater for
i) water stored concrete than for dry concrete
ii) angular crushed aggregates
iii) rounded aggregates The correct answer is
a) (i) and (ii)
b) (i) and (iii)
c) only (i)
d) only (ii)

164. If the contributions of tricalcium silicate, dicalcium silicate, tricalcium aluminate
and terra calcium alumino ferrite to the 28 days strength of hydrated ordinary Portland
cement are respectively W, X, Y
and Z, then
a) W>.X>Y>Z
b) X>W>Y>Z
c) W>X>Z>Y
d) W>Y>X>Z

165. The initial and final setting times for ordinary portland cement are approxi¬
mately related as
a) T = 530 + t
b) T = 270 + t
c) T = 90+1.2t
d) T = 600-1.2t
where T and t are respectively final and initial setting times in minutes.

166 Assertion A : The presence of tricalcium aluminate in cement is undesirable. Reason R : Tricalcium aluminate in cement contributes very little to strength of cement.
a) Both A and R are true and R is the correct explanation of A
b) Both A and R are true but R is not the correct explanation of A
c) A is true but R is false
d) A is false but R is true

167. Amount of gypsum required to be added to the clinker depends on the following contents of cement i) tricalcium silicate ii) dicalcium silicate iii) tricalcium aluminate iv) alkali The correct answer is
a) (i) and (ii)
b) (ii) and (iii)
c) (iii) and (iv)
d) (i)and(iv)

168. The diameter of needle used in Vicat’s apparatus for the determination of initial
setting time is prescribed as
a) 0.5 mm
b) 1 mm
c) 5 mm
d) 10mm

169. The heat of hydration of cement can be reduced by
a) reducing the proportions of C3A and C3S
b) increasing the proportions of C3A and C3S
c) increasing the fineness of cement
d) both (a) and (c)

171. Assertion A : Rapid hardening cement is generally not used in mass concrete construction.
Reason R : The rate of heat development is low in rapid hardening cement. Select your answer based on the coding system given below
a) Both A and R are true and R is the correct explanation of A.
b) Both A and R are true but R is not the correct explanation of A.
c) A is true but R is false.
d) A is false but R is true.

172. If the angularity number of an aggregate is increased, then the workability of the concrete using this aggregate will
a) increase
b) decrease
c) not change
d) none of the above

173. If W,, W2, W3 and W4 are the weights of sand in oven dry, air dry, saturated but
surface dry and moist conditions respectively, then the moisture content of sand is
a) W3 – W,
b) W4-W2
c) W4-W3
d) W3-W2

174. The ordinate of grading curve of an aggregate represents
a) cumulative percentage passing each sieve plotted on normal scale
b) cumulative percentage passing each sieve plotted on logarithmic scale
c) sieve size plotted on normal scale
d) sieve size plotted on logarithmic scale

175. Increase in fineness modulus of aggregate indicates
d) none of the above

176. Weight of an oven dry sand and air dry sand are 500 gm and 520 gm respectively.
If the weight of the same sand under saturated but surface dry condition is 525 gms, then the water absorption of sand is
a) 1%
b) 4%
c) 4.76%
d) 5%

177. Soundness test of cement by Le-Chatelier’s apparatus gives unsoundness due to
a) free lime only
b) magnesia only
c) both free lime and magnesia
d) none of the above

178. Maximum permissible limit of magnesia content in ordinary Portland cement is
a) 4%
b) 6%
c) 8%
d) 10%

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