Quarry Southern Africa November 2017 - Page 23

BENEFICIATION 2 1 & 2. Founded in 1892 as De Eerste Cement Fabrieken Beperkt, PPC’s Hercules factory outside of Pretoria is still operating today. F or well over a century, PPC has tracked the growth and the development of South Africa and Zimbabwe, producing cement for many iconic landmarks, including the Union Buildings, the Kariba Dam, the Gautrain, the Huguenot Tunnel, and Medupi Power Station, as well as much of southern Africa’s infrastructure. Cementing materials have been widely used since ancient times, with Egyptians using calcined gypsum as cement, and the Greeks and Romans using lime and sand for mortar, adding coarser stones to make concrete. The Romans also discovered that adding crushed volcanic ash to lime created a cement that would set under water — perfect for constructing harbours. But it wasn’t until 1824 that the precursor of modern Portland cement was created by British stone mason Joseph Aspdin, who took out a patent for ‘Portland cement’: a mixture of finely-ground clay and limestone fired until the limestone was calcined. The first significant use of this proto-Portland cement was in a tunnel under the Thames River in 1828. Two decades after Aspdin patented his cement, the first truly modern Portland cement was produced by Isaac Johnson, who fired a mix of chalk and clay at much higher temperatures than Aspdin did (1 400– 1 500°C), forming minerals that are very reactive and more strongly cementitious. Just under half a century later, in 1892, South Africa’s first cement plant was established on the outskirts of Pretoria by Edouard Lippert under the name De Eerste Cement Fabrieken Beperkt, to counter the exorbitant cost of importing cement from Europe. This same facility, today known as QUARRY SA | NOVEMBER 2017 _ 21