The cement and water slurry coming on the top and setting on the surface is called

Crazing: Crazing is development of networks of very fine random cracks or fissures on the surface of concrete due to differences in shrinkage between the surface and the interior. The cracks rarely exceed 12 mm or so in depth, and are therefore not serious, apart from the unsightliness.

Efflorescence: Efflorescence is a whitish coloured powdered deposition of salts (such as sulphates and carbonates of calcium, sodium and potassium) on the concrete surface that is formed due to evaporation of water from the water soluble salts in the concrete.

Sulphate deterioration: Sulphate attack on concrete is a chemical breakdown mechanism where sulphate ions attack components of the cement paste. Due to sulphate attack, ettringite is formed which is very expansive in nature, results in deterioration in concrete in form of cracking and spalling.

Laitance: In case of excess water in concrete mix, the cement along with water slurry comes to the surface by capillary action and formsa thin layer over surface known as laitance. This weakens the bond between the successive lifts of concrete. The excess water may leak through the form work, resulting in honeycombed concrete and on evaporation makes the concrete porous.