Cement in ancient times is not what is used now. In fact, the name did not exist at that time, only building glue and reinforcement. It all started from the time of the Roman Empire which succeeded in making an adhesive called pozzuolana. This mixture of material consists of limestone and volcanic ash, where it will be active after going through the combustion process. After the Roman empire collapsed, this pozziolana mix material was scarce and even almost said to be extinct from the market. The word semen itself is taken from the Latin ” caementum”, which means “to cut into small pieces which are irregular.
Then in the 18th century, this ingredient was rediscovered by a British engineer named John Smeaton. He managed to make an adhesive from limestone mixed with clay. At that time, he used a mixture of adhesives to build a flare tower named Eddystone located near the coast of Cornwall in England. However, the one who patented this miraculous ingredient was not Smeaton, but Joseph Aspidin. This engineer, who was also a British national, first handled his patent rights in 1824. His work was called “Portland cement”. This is because the findings are said to be similar to clay in Portland Island, England. Finally in 1845, Isaac Johnson succeeded in conducting research on cement which would later be useful for the current cement industry.
Cement is made by grinding together with limestone and aluminosilicate sources, such as clay, shale, or sand. Then it is heated to a mixture of up to 1500 ° C in a rotary cement furnace. The first important reaction that occurs in the lower temperature portion of the furnace (900 ° C) is calcination of limestone. This reaction is a process of heating to high temperatures to oxidize or decompose a substance and convert it into powder. When calcium carbonate (lime) breaks down into calcium oxide (lime) and carbon dioxide is turned off. Whereas at higher temperatures calcium oxide reacts with aluminosilicate and silicate to form Ca2SiO 4, Ca3SiO5, and Ca 3Al 2O which are liquid. The relative proportions of these compounds determine the final properties of this material. When the compounds are cold, they freeze into a form called clinker. The clinker is ground into a fine powder and a small amount of calcium sulfate (gypsum) is added to form Portland cement.
Concrete is produced by mixing cement with crushed sand, gravel, or stone and water. Often small amounts of additives are added to achieve certain properties. For example, flow and dispersion are improved by adding polymeric materials such as phenolic resins, and resistance to ice damage is increased by adding surfactants. When water is added to cement, complex hydration reactions that produce hydrates occur such as Ca3Si 2O 7⋅H2O, Ca3Si 2O 7⋅3H2O, and Ca (OH) 2
2 Ca SiO (s) 2H O (l) → Ca Si OHO (s) Ca (OH) (aq)
2 Ca SiO (s) 4 HO (l) → Ca Si O 3H O (s) Ca (OH) (aq)
This hydrate forms a gel or slurry that coats the surface of the sand or aggregate and fills holes to form solid concrete. The properties of concrete are determined by the relative proportions of calcium silicate and calcium aluminosilicate in the cement used, additives, and the amount of water, which determines the level of hydration.
Raw materials for making cement often contain traces of sodium and potassium sulfate, and sodium and potassium hydroxide are formed during the hydration process. This hydroxide is responsible for cracking, swelling, and distortion