State four (4) precautions to be taken when laying screed to an old concrete floor. – NABTEB QUESTION

ANSWER

Precautions to be taken before laying screed to an old concrete floor.

(i) Clean off the surface of the concrete floor thoroughly
(ii) Remove only laitance or scum on top of the concrete floor.
(iii) Hack the surface of the concrete to ensure good bondage either manually or mechanically with a hack hammer.
(iv) Wet the surface with water to ensure hardening and shrinkage of screed and slab
simultaneously. This also prevents detachment of screed from the concrete base.