Of course, there are other types of cement apart from Portland cement. Important examples include:
Calcium aluminate cements
Calcium aluminate cements (CACs)
These may also be termed 'Ciment Fondu' and used to be called 'high alumina cements.' They are made from lime or limestone mixed with bauxite (aluminium ore) or other high-alumina material.
Concretes made with CACs develop strength quickly and are resistant to chemical attack. CACs have a wide range of compositions, mainly with different ratios of lime to alumina; strictly, ‘Ciment Fondu’ is only one part of this compositional range. CACs are generally brown or grey-black, but can be white if made from pure alumina.
As well as being used in concrete, CACs are also used in grouts and other specialised applications, often mixed with Portland cement and other materials such as gypsum.
Lime concrete and mortar - the most basic cementitious material
Lime mortar and concrete have been used for thousands of years (see history of cement) so, historically, lime is probably the most basic cementitious material of all. Today, lime mortar and concrete are used mainly in the rebuilding or repair of historic or ancient buildings, although in the UK there has been some recent use of lime mortar in the construction of new buildings. There are several advantages in using lime mortar:
Cracks that develop in lime mortar tend to heal themselves, unlike conventional mortar made with Portland Cement.
Lime mortar is usually weaker than mortars made with Portland Cement and so can be removed from the brick or stone at the end of the useful life of the building. Particularly in the case of bricks, this means that they can be recycled, saving a lot of energy otherwise needed to make new bricks. Bricks used with mortar made with Portland Cement generally can’t be re-used as it is difficult to detach the mortar from the brick without damaging it.
Lime is produced at a lower temperature than Portland Cement, so other things being equal, it takes less energy to produce a lime mortar compared with a mortar containing Portla