Curing:
Curing means to cover the concrete with a layer of water, so it stays moist. By keeping concrete moist, the bond between the paste and the aggregates gets stronger. Concrete doesn't harden properly if it is left to dry out. Curing is done just after finishing the concrete surface, as soon as it will not be damaged. The longer concrete is cured, the closer it will be to its best possible strength and durability. Concrete that is cured sufficiently is less likely to crack.
The specimens are removed from the molds 24 hours after casting. Specimens are placed immediately in water after removal from the molds to prevent loss of moisture from specimens.
Cylinders Capping:
Capping a concrete cylinder means placing a smooth uniform cap/layer at the end of a concrete cylinder to provide for a uniform load distribution when testing. Since the concrete sample will contain voids and aggregate particles at the upper surface that is left open, it is necessary to prepare a smooth uniform surface for the testing machine to press against.
Plaster of Paris (Gypsum) is used as capping material nowadays. Capping of all the concrete cylinders is carried out carefully with the help of capping machine for concrete cylinders, as shown in the figure.
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