Concrete Technology Questions and Answers for Experienced people on “Hot Weather Concreting, Prepacked and Vacuum Cement”.
1. Concrete is not recommended to be placed at a temperature above _________oC.
a) 20
b) 30
c) 40
d) 50
Answer: c
Clarification: Any operation of concreting done at atmospheric temperature above 40 oC may be put under hot weather concreting.
2. IS: 7861 part-1 deals with ___________
a) Hot weathering concrete
b) Cold weathering concrete
c) Air entertained concrete
d) OPC
Answer: a
Clarification: IS: 7861 part-1 deals with hot weather concreting and Part-2 deals with cold weather concreting.
3. A higher temperature of fresh concrete results in a __________ hydration of cement.
a) More rapid
b) Rapid
c) Low
d) Very low
Answer: a
Clarification: A higher temperature of fresh concrete results in a more rapid hydration of cement and leads to reduced workability/ accelerated setting.
4. Does this reduce handling time?
a) True
b) False
Answer: a
Clarification: A higher temperature of fresh concrete results in a more rapid hydration of cement and leads to reduced workability/ accelerated setting. This reduces the handling time of concrete.
5. Rapid evaporation may cause plastic shrinkage __________
a) Elastic shrinkage
b) Plastic shrinkage
c) High workability
d) Good strength
Answer: b
Clarification: Rapid evaporation may cause plastic shrinkage and cracking and subsequent cooling of hardened concrete would introduce tensile stresses.
6. It is difficult to retain moisture for hydration for RAPID EVAPORATION OF WATER DURING CURING PERIOD.
a) True
b) False
Answer: a
Clarification: It is difficult to retain moisture for hydration and maintain reasonably uniform temperature conditions during the curing period.
7. Prepacked concrete _________ water proofing concrete.
a) Is
b) Is not
c) May be
d) Is but depends on temperature
Answer: a
Clarification: Prepacked concrete is water proofing concrete with quality plaster which prevents water seepage.
8. Cement has ________ % volumetric shrinkage after curing.
a) 5
b) 6
c) 7
d) 8
Answer: a
Clarification: Option a is the correct one because cement has 3-5% volumetric shrinkage after curing.
9. After vacuum mixing, the volumetric shrinkage can be raised from 3–5% to __________ % in different cements.
a) 1-2
b) 3-5
c) 5-7
d) 6-8
Answer: c
Clarification: The volumetric shrinkage can be raised from 3–5 % to 5-7 % in different cements after mixing vacuum into it.
10. Vacuum mixing systems reduce the exposure by _________ %.
a) 20
b) 40
c) 50
d) 10
Answer: c
Clarification: Vacuum mixing system decreases the exposure by 50 % to 70% and eliminates the contact with the bone cement while delivery.
11. The exposure of conventional mixing in open bowl is about ___________ ppm in the breathing zone.
a) 20
b) 40
c) 50
d) 10
Answer: d
Clarification: 10 ppm is the exposure value of conventional mixing in open bowl in the breathing zone. And the exposure limit lies in the range of 50-100 ppm in Europe.
Concrete Technology for Experienced people,