All About Cement
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Manufacturing Process

 

Although cement is one of the oldest building materials around, its production process is a mix of traditional chemistry and hi-tech equipment to make the cement used to construct homes and buildings around the world.

From the raw materials obtained from the quarry to the delivery of the end products to customers, we invite you to follow every step in the cement manufacturing process.

 

Step 1: Raw Materials Preparation

The raw materials needed to produce cement (calcium carbonate, silica, alumina and iron ore) are generally extracted from limestone rock, chalk, shale or clay. These raw materials are won from the quarry either by extraction or through blasting. These naturally occuring minerals are then crushed through a milling process.  At this stage, additional minerals are added to ensure the correct chemical composition to make cement is in place.  It is then dried and ground to the correct chemical composition and stored in silos for the next process.  Lafarge recognised that such raw materials are non-renewable resources and as such, the mining and processes are fully in line with Lafarge's sustainability actions and commitments.   Wherever possible, we would substitute natural resources with by-products from other industries. 

Step 2: Raw Grinding and Burning

Grinding produces a fine powder, known as raw meal, which is preheated and then sent to the kiln. The kiln is at the heart of the manufacturing process.    Once inside the kiln, the raw meal is heated to around 1,500°C - it is of a similar temperature to molten lava.  At this temperature, chemical reactions take place to form cement clinker, containing hydraulic calcium silicates.

 

In order to heat the materials to this very high temperature, a 2,000°C flame is required, which can be produced through the use of fossil and waste-derived fuels.  The kiln itself is angled by 3° to the horizontal to allow the material to pass through it, over a period of between 20-30 minutes.

 

Upon exiting, the clinker is cooled and stored ready for grinding to produce cement.

 

Step 3: Cement Grinding and Shipping

A small amount of gypsum (3-5%) is added to the clinker to regulate how the cement will set. The mixture is then very finely ground to obtain ‘pure cement'. During this phase, different mineral materials, called ‘additions', may be added alongside the gypsum. Used in varying proportions, these additions, which are of natural or industrial origin, give the cement specific properties such as reduced permeability, greater resistance to sulfates and aggressive environments, improved workability, or higher-quality finishes. 

 

Finally, the cement is stored in silos before being shipped in bulk or in bags to the sites where it will be used.

 

Recycling

One of the main ways of recycling materials is through the use of additions to make cements with a lower carbon footprint.  Cements manufactured by Lafarge have an average addition content of 23%.  As well as incorporating additions from natural origin (such as limestone and volcanic rock), they can also come from industrial origin, for example pulverised fuel ash (from coal-fired power plants).  The use of additions:

  • enhances certain cement properties,
  • recycles materials that would otherwise have been sent to landfill,
  • reduces the consumption of natural raw materials,
  • reduces CO2 emissions

The company also recycles the use of wastes and by-products of other industries as raw materials and fuels.

 

Kiln Reliability

Ensuring a good yield

The reliability of a kiln can be calculated by comparing the number of hours it has been operating, with the amount of manufacturing time which may have been lost (for example, if the supply of raw materials to the kiln has been temporarily halted due to an issue with the refractory inside the kiln itself).  Improving this indicator is key to achieving higher yield and productivity targets set in the Group's Excellence programmes. 

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 Kanthan Plant, Perak

 

Langkawi Plant, Kedah

 

Pasir Gudang Plant, Johor

 

 Rawang Plant, Selangor

LafargeHolcim. Cement, aggregates, Concrete.