Which of the following precautions need to be adopted for concreting in sub-zero temperature?
(i) Pre-heating of materials of concrete
(ii) Economical heating of materials of concrete
(iii) Admixtures of anti-freezing materials
(iv) Electrical heating of concrete mass
1
Only (i) and (ii)
2
Only (i), (ii), (iii)
3
(i), (ii), (iii), and (iv)
4
Only (i)
5
Question Not Attempted