The second industrial age also saw the reemergence of concrete and higher-strength artificial cements.
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Lime mortar—made of lime, sand, and water—has been known since ancient times. It was improved in the late 18th century by British engineer John Smeaton, who added powdered brick to the mix and made the first modern concrete, known as Hydraulic Concrete.
William Aspdin patented the first true artificial cement, which he called Portland Cement, in 1824. The name was intended to recall the same high quality of Portland stone.
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To make Portland cement, Aspdin burned limestone and clay together in a furnace; the clay provided silicon compounds, which when combined with water formed stronger bonds than the calcium compounds of limestone.
Nowadays a Portland cement cylinder is made by heating a mixture of raw materials to a calcination temperature above 600 °C (1,112 °F) and then a melting temperature, which is around 1,450 °C (2,640 °F) for modern cement, to sinter clinker materials.
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This compound is made from unprocessed common natural materials. Consequently, the characteristics of Portland cement clinker can vary from one cement factory to another. To limit variations in the technological properties of Portland cement, acceptance standards have now been developed.
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