141. Alkali-Silica reactivity is a potential cause of distress in

1. sludge treatment plant
2. hydraulic jump
3. concrete
4. drinking water

142. Which of the following is present in the highest percentage in coal fly ash suitable to be used in concrete?

1. Aluminium oxide
2. Silicon oxide
3. Calcium oxide
4. Magnesium oxide

143. Which of the following parameters is critical in designing cement concrete mix exposed to repeated freeze-thaw?

1. Water reducer
2. Accelerator
3. Entrained air
4. Excess cement

144. A concrete pour of 1080 m³ is planned with a 120 m³/hr capacity. If the efficiency of the plant is assumed to 75%, what will be approximate time taken for completing the pour?

1. 8
2. 9
3. 7.5
4. 12

145. The batching accuracy (in %) of water used for mixing concrete should be within

1. ± 2
2. ± 1
3. ± 5
4. ± 3

146. In shotcreting, what is the purpose of accelerating chemical?

1. to adjust the workability of shotcrete
2. to accelerate the initial strength gain
3. to provide better finish to shotcrete
4. to improve the bonding between substrate and shotcrete

147. The strength and quality of concrete depends on

1. aggregate shape
2. aggregate grading
3. surface area of the aggregate
4. all of the above

148. The lower water cement-ratio in concrete produces

1. more density
2. small creep and shrinkage
3. more bond
4. all of the above

149. The strength of concrete is directly proportional to

1. water cement ratio
2. cement water ratio
3. sand cement ratio
4. water aggregate ratio

150. Identify the corresponds to accelerator : retarder.

1. NaOH : KOH
2. CaCl₂ : CaSO₄
3. KOH : NaOH
4. NaCl : CaCl₂