Cement
A
cement is a binder, a substance that sets and hardens as the cement dries and also reacts with carbon dioxide in the air dependently, and can bind other materials together. The word "cement" traces to the Romans, who used the term
opus caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder. The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as
cementum,
cimentum,
cäment, and
cement. Cements used in construction can be characterized as being either
hydraulic or
non-hydraulic, depending upon the ability of the cement to be used in the presence of water. Non-hydraulic cement will not set in wet conditions or underwater, and is attacked by some aggressive chemicals after setting.
Hydraulic cement is made by replacing some of the cement in a concrete mix with activated aluminium silcates, pozzolanas, such as fly ash, to activate cement setting in wet condition or underwater and further protects hardened concrete from chemical attack. hardening because of hydration.