Cement

Types of Cement
– Cement materials can be classified into hydraulic cements and non-hydraulic cements.
– Hydraulic cements require water for setting and hardening, while non-hydraulic cements can set under air.
– Hydraulic cements, such as Portland cement, consist of silicates and oxides.
– The main mineral phases of hydraulic cements are alite, belite, tricalcium aluminate, and brownmillerite.
– Non-hydraulic cement sets as it dries and reacts with carbon dioxide in the air.
– Non-hydraulic cement does not require water for setting and hardening.
– Non-hydraulic cement is resistant to chemical attack after setting.

Chemistry of Cement
– Hydraulic cement hardens through hydration of clinker minerals when water is added.
– The main mineral phases of hydraulic cement are responsible for its mechanical properties.
– The limestone is burned to produce lime in a calcination reaction.
– Lime reacts with silicon dioxide to form dicalcium silicate and tricalcium silicate.
– Lime also reacts with aluminum oxide to form tricalcium aluminate.
– Calcium oxide is obtained by thermal decomposition of calcium carbonate.
– The chemistry of these reactions is still the subject of research.

Ancient Alternatives to Cement
– Bitumen was used by the Babylonians and Assyrians to bind burnt brick or alabaster slabs.
– Ancient Egyptians used sand and burnt gypsum mortar for cementation.
– Ancient Greeks used crushed potsherds as a pozzolan for hydraulic cement.
– Roman engineers used volcanic ash and lime for hydraulic cement.
– Crushed brick or pottery was used as a substitute for pozzolanic ash.

Historical Use of Cement
– Lime was used by the Ancient Greeks and Minoans for cementation.
– The Greeks used volcanic tuff from Thera as a pozzolan.
– Roman engineers used crushed volcanic ash with lime for hydraulic cement.
– The material was called pozzolana and was extracted from Pozzuoli.
– Roman concrete was extensively used in structures like the Pantheon and Baths of Caracalla.
– Hydraulic cement actively used by medieval masons and military engineers in the Middle Ages.
– Structures such as canals, fortresses, harbors, and shipbuilding facilities were constructed.
– Lime mortar and aggregate with brick or stone facing material used in the Eastern Roman Empire and Gothic period.
– German Rhineland utilized hydraulic mortar with local pozzolana deposits.

Development of Cement Techniques
– Tabby, a building material made from oyster shell lime, sand, and whole oyster shells, introduced in the 16th century.
– Concrete formed using tabby.
– French and British engineers formalized technical knowledge for making hydraulic cement in the 18th century.
– John Smeaton’s contribution to cement development for Eddystone Lighthouse construction.
– Parkers Roman cement developed by James Parker in the 1780s.
– Louis Vicat identified the principle of combining chalk and clay for cement production in the 19th century.
– Vicat devised a method for intimate mixture of chalk and clay.
– Burning process used in cement production.
– Roman cement replaced by Portland cement in the 1850s.
– Smeaton’s work on hydraulic cement apparently unknown to Vicat.https://en.wikipedia.org/wiki/Cement