This set of Concrete Technology Quiz focuses on “Mix Design of LWC, Aerated Concrete”.
1. What is the amount of mixing water used to make LWC?
Explanation: The general practice for structural light-weight concrete is to mix the aggregate and about 2/3 of the mixing water for a period upto one minute prior to the addition of cement and the balance mixing water.
2. What is the normal time to get uniform mixing?
a) 30 seconds
b) 2 or more minutes
c) 1 minutes
d) 24 hours
Explanation: Mixing is done continuously as required for homogeneity. Usually 2 or more minutes are required to get uniform mixing.
3. The strength of the resulting concrete is _______ % lower than when dry aggregate is used for the same content.
Explanation: It has been seen that the strength of the resulting concrete is about 5 to 10 per cent lower than when dry aggregate is used for the same content and workability.
4. The density of concrete made with saturated aggregate is ___________
c) Very high
d) Very low
Explanation: Moreover, the density of concrete made with saturated aggregate is higher and the durability of such concrete, especially its resistance to frost is lower.
5. The light-weight concrete is prepared by ________
a) Mixing Portland cement with sawdust in specified proportion in the concrete
b) Using coke-breeze, slag as aggregate in the concrete
c) Mixing Al in the concrete
d) Mixing Fe in the concrete
Explanation: The light-weight concrete is prepared by using coke-breeze, cinder or slag as aggregate in the concrete.
6. Light weight cement content for compressive strength 4000 psi is _______ pounds per cubic yard.
Explanation: Light weight cement content for compressive strength 4000 psi is 530-660 pounds per cubic yard and 400-510 is for compressive strength 2500 psi.
7. Light weight cement content for compressive strength 27.58 MPa is _______ kg/m3.
Explanation: Light weight cement content for compressive strength 27.58 MPa is 314-392 kg/m3. 261-332 is the compressive strength of 20.68 MPa.
8. Aerated Concrete is _________
a) Very heavy weight
b) Heavy weight
c) Medium weight
d) Light weight
Explanation: Aerated concrete is also referred to as gas concrete, foam concrete, cellular concrete. In India we have at present a few factories manufacturing aerated concrete.
9. Air contents should be _________ % by volume.
Explanation: This type of cement was first of all developed in U.S.A. It is recommended that air contents should be 03-04 % by volume.
10. Entrainment of air also improves workability and durability.
Explanation: Entrainment of air also improves workability and durability to produce such concrete which would have resistance to weathering actions.
11. Which one is not used as air entraining agents?
b) Natural resins
Explanation: Natural resins, fats, oils are used as air entraining agents not alumina.
12. Entrainment of air while applying cement, increases resistance to frost action.
Explanation: It is found that entrainment of air or gas bubbles while applying cement, increases resistance to frost action.
13. Aerated concrete is made in the density of approx. _________ kg/m3.
Explanation: Aerated concrete is made in the density range from 300 kg/m3 to about 800 kg/m3.
14. No fines concrete is manufactured by _____________
a) By adding no fines materials from normal concrete
b) By eliminating no fines materials from normal concrete
c) By reducing its strength
d) By increasing its strength
Explanation: No fines concrete is one type of light weight concrete. As the name indicates that it is a concrete mix without fine aggregate or sand.
Sanfoundry Global Education & Learning Series – Concrete Technology.
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