Must-know: Cement preparation
The company takes a sample of the limestone at various levels in the form of steps. The steps are called benches. The benches determine the quality assurance. Since quality varies, the bench compares it with the standard that’s required. This is called limestone benching.
Aug. 18 2014, Updated 9:00 a.m. ET
Cement preparation
The essential raw materials used to manufacture cement are limestone and chalk. The raw materials are used to produce clinker. Clinker, the intermediate product, is the key ingredient of cement. It’s used with additives such as bauxite, iron ore, and gypsum.
Depending on the grade of the limestone, additives such as silica, alumina, and iron ore are added to achieve the product’s quality. The required grade of limestone should be 40%–41%. Then the additives are added accordingly.
Fuels like coal, pet coke, natural gas, lignite, or oil can be used. The industry has been considering the use of alternate fuels such as agriculture wastes, waste oils, animal meal, and rice husk. Alternate fuels are needed because of the fuel shortage and rising fuel prices.
The choice of fuel for various manufacturers, like CRH plc (CRH), Cemex, SAB de CV (CX), Eagle Materials Inc. (EXP), and James Hardie Industries SE (JHX), depends on its availability, cost, efficiency level, and the process employed.
The process of manufacturing cement from mining limestone to the final product involves the limestone being benched, drilled, blasted, and crushed.
Benching, drilling, and blasting
To make cement, there are minimum constituents required in the limestone. The company takes a sample of the limestone at various levels in the form of steps. The steps are called benches. The benches determine the quality assurance. Since quality varies, the bench compares it with the standard that’s required. This is called limestone benching.
Once the limestone is benched, it’s drilled and broken into small pieces. This is called blasting.
After blasting, the excavation process takes place. This is called limestone raising. Then the limestone is taken from the quarry to the factory for crushing.
Crushing
Limestone is crushed and reduced to a size that’s suitable for storaging and blending. Then the raw materials are crushed in a grinder. The size of the crushed material required depends on the type of the grinding mill.
Crushed limestone is packed and transported to the reclaimer stage. This is the pre-homogeneous stage where additives like silica, alumina, and iron ore are added. It’s spread to make the quality uniform. This helps reduce the variations in the limestone’s chemical characteristics.
Investors can access the cement industry through the Vanguard FTSE Emerging Markets ETF (VWO).
Continue reading the next part of the series to learn about cement’s final manufacturing process.