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

Correct option is C

When concreting in sub-zero temperatures, the following precautions are essential to ensure the
proper setting and strength development of the concrete:
(i) Pre-heating of materials of concrete: This prevents the water in the mix from freezing and helps in
maintaining the proper temperature for hydration.
(ii) Economical heating of materials of concrete: This ensures the materials are brought to a suitable
temperature without incurring excessive costs.
(iii) Admixtures of anti-freezing materials: These admixtures lower the freezing point of water in the
concrete mix, allowing hydration to continue at lower temperatures.
(iv) Electrical heating of concrete mass: This method provides a controlled way to keep the concrete warm during curing, preventing freezing and ensuring proper strength development.
All these precautions collectively help in achieving the desired concrete quality and strength in sub-zero temperatures.