Cement Production Process

Cement is a fine powder which sets after a few hours when mixed with water, and then hardens in a few days into a solid, strong material. Cement is mainly used to bind fine sand and coarse aggregates together in concrete.

Cement is a hydraulic binder, i.e. it hardens when water is added.

There are 27types of common cement which can be grouped into 5 general categories and 3 strength classes: ordinary, high and very high.

In addition, some special cement exist like sulphate resisting cement, low heat cement and calcium aluminates cement.




The quarry is the starting point
Cement plants are usually located closely either to hot spots in the market or to areas with sufficient quantities of raw materials. The aim is to keep transportation costs low. Basic constituents for cement (limestone and clay) are taken from quarries in these areas.

The raw materials for cement production are quarried using powerful excavators or explosive materials.

The raw materials are crushed by special machinery into pieces usually smaller than 30 millimetres in size.

A two-step process
Basically, cement is produced in two steps:

First, clinker is produced from raw materials.

In the second step cement is produced from cement clinker.

The first step can be a dry, wet, semi-dry or semi-wet process according to the state of the raw material.

Raw Meal Production

The raw materials transported to the Plant undergo crushing with the help of huge crushers and then are either stored separately, or they are directly driven to prehomogenization piles. Next, via a fully automated system, comprising weighing devices of high accuracy and conveyor belts, the crushed raw materials are driven into the mill (roller mill or ball bearing mill) for further fine grinding.

The output, labelled as «raw meal», is stored into special silos for the homogenizing process, which is carried out with the help of blowers installed at the silos' bottoms. Next, the raw meal is taken to the storage silos wherefrom it is driven to the silos for the feeding of the Rotary Kiln, where the intermediate output, called «clinker», is produced.

Making clinker

For the production of one ton of clinker around 1.6 tons of raw materials are utilized (70-85% limestone, 10-20% shale etc.) and over 0.1 ton of coal.

The raw materials are delivered in bulk, crushed and homogenised into a mixture which is fed into a rotary kiln. This is an enormous rotating pipe of 60 to 120 m long and up to 6 m in diameter. This huge kiln is heated by a 2000°C flame inside of it. The kiln is slightly inclined to allow for the materials to slowly reach the other end, where it is quickly cooled to 100-200°C.

With the usage of cyclone system and a limestone grinder, the raw meal, prior to it’s feeding into the Rotary Kiln, undergoes thermal processing at 900 degrees C. The Rotary Kiln temperature is gradually raised up to 1450 degrees C and its final output, which is in granular form, is the result of the chemical decomposition of CaCO3 and of the alumina-silicate compounds and the result of chemical reactions between CaO and the oxides of Si, Al and Fe which are thus produced.

Four basic oxides in the correct proportions make cement clinker: calcium oxide (65%), silicon oxide (20%), alumina oxide (10%) and iron oxide (5%). New compounds are formed: silicates, aluminates and ferrites of calcium. Hydraulic hardening of cement is due to the hydration of these compounds.


The final product of this phase is called “clinker”. These solid grains are then stored in huge silos.


From clinker to cement

The second phase is handled in a cement grinding mill (made of metallic cylinders, containing several tons of grinding media, that are necessary when the grinding process takes place), which may be located in a different place to the clinker plant.

Gypsum (calcium sulphates) and possibly additional cementitious (such as blast furnace slag, coal fly ash, natural pozzolanas, etc.) or inert materials (limestone) are added to the clinker. All constituents are ground leading to a fine and homogenous powder.

Clinker is the basic ingredient of cement, and it largely determines the quality of the end product. Cement, as a finished product is a very fine powder that requires for its manufacture a mix of clinker, gypsum and certain natural or artificial materials (such as pozzolana), which grant beneficial properties to the cement. The cement mills resemble the raw meal mills. The exact mix of materials is strictly specified and continuously monitored. The type of cement and level of compressive strength - which is the most important characteristic - depend on the chemical composition of the clinker, the duration of the grinding and the presence or absence of various additives.

The cement is then stored in silos before being dispatched either in bulk or bagged using special silo trucks or ships.

Engineering on Cement Plants
A cement plant is a group of complicated and complex installations. It is composed by a variety of other “sub-plants”. The sizes involved in cement plant design are over the average corresponding size encountered in usual projects.

A cement production plant requires:

  • A great variety of raw materials in large quantities

  • Large storage spaces

  • Great internal and external dispatching abilities

  • Heavy mechanical equipment

  • Special storages appropriate for the fuel (coal) handling

  • Special industrial building structures

  • Large energy consumption

  • High and qualitative productivity

  • Best available techniques (BAT) for environmental protection

  • An excellent system of personnel safety and installations protection and care

  • Value added

  • Social contribution

  • Low operation cost

The plant’s installation design is fully dictated by the operational production process in combination with the above requirements.

As an example, during the pre-calcining process, the meal should be previously submitted to thermal elaboration in an environment of 900oC temperature. This is reached through the conveyance of the material into a vertical cyclone system. The meal crosses, due to gravity, the cyclone system, to reach the entrance of the rotary kiln. Simultaneously, through the cyclones and having the opposite direction, ascend the hot gases from the kiln, producing the thermal elaboration. For the achievement of the best, desirable outcome of the thermal procedure, the described cyclone system should include at least five (5) stages (five cyclones in vertical order). Taking into consideration the required material quantities and the above mentioned best available practice, the total estimated height of the cyclone system is between 70 and 100m. As a result, a steel or

reinforced concrete tower of appropriate height is needed.

This tower should be equipped with additional machinery (due to low cost requirements) as well as big fans for hot gas flow from the rotary kiln burner, as described above. These special fans beside their heavy loads, enforce vibrations to the structure.

This makes the design of such structures absolutely specialized, in order to achieve the above mentioned best available practices. The same practice is applied to the design and study of all the installations that constitute a cement production plant.


A brief description of the main design prerequisites follows below:

-      Long spans
-      Closed for environmental reasons
-      Large surfaces – Heavy wind loads
-      Optimization for economic solution
-      Big heights – Adequate capacity
-      Special requirement material storage
-      High temperature differences between inside and outside
-      Special foundations
-      Optimization for economic solution
-      Heavy duty mechanical equipment
-      Huge operating machinery
-      Heavy dynamic loads
-      Special foundations
-      Noise
-      Optimization for economic solution
-      Special steel structures
-      Heavy dynamic loads – Machinery in operation
-      Covering – Environmental protection – Safety
-      Optimization for economic solution
-      Very high buildings (up to 100m)
-      High temperature
-      Special foundation for stability (earthquake – wind)
-      Optimization for economic solution
-      Full overview and easy collision and fitting checks
-      Operational control
-      Automatic production of cutting drawings
-      Exact bill of quantities
-      Easy pre-fabrication of construction groups and quick erection
-      Enables perfect organization and facilitates management activities
-      Easy evaluation of critical paths and delays
-      Programming of resources (machinery, human, cost)
-      Control and easy presentation of the program
The analysis and design of all the above special structures requires:
  • Specialized knowledge and experience

  • Appropriate software for static and dynamic analysis, earthquake resistant

  • design, geotechnical problems and foundation engineering and CAD – tools for analytical drawings for application (rebar lists, cutting drawings for steel structures, e.t.c.)

  • Major parts of the software consist of inhouse products, specially developed or customized for the above requirements

The engineering Team of Cubus Cement has been involved for over two decades in the  design and supervision of the following cement industry projects:

Project List

Raw Material Crushers


300 - 1.300


Raw Material Silos


3.000 - 40.000


Pre-homo Storages




Raw Mill Installation


250 - 400


Raw Meal Silos


8.000 - 12.000


Preheater Towers



m height

Kiln Line Bases

3 lines



Cooler Buildings




Clinker Silos-Storages


10.000 - 70.000


Cement Mill Buildings


105 - 140


Cement Mill Feeding Silos




Cement Additive Storages




Cement Silos


500 - 28.000


Fly Ash Silos




Paking Plants/Paletizers




Coal Yards




Coal Mills




Belt Conveyors, Bridges, Towers, Pylons, Pipes, Air Slides, Drag Chains, Bucket Elevators, Trippers e.t.c.




Piers and Docks for Shipping


Length up to 400 m Width up to 40 m   Depth up to 19 m    Ships up to 140.000TDW


General Layout of Cement Plants







Push over analysis accor-ding to the structural inter-ventions regulations

STATIK-5P continues to lead the static inelastic analysis of space frames, according to the specifications of the new Greek regulations for stru-ctural interventions (Nove-mber 2005 issue).




Static inelastic aseismic analysis of buildings (push over analysis) with STATIK-5H according to the new Greek structural interventi-ons regulations

Athens, June , 21 & 22, 2007.

Applications to participate up to May 25, 2007.


Static and aseismic analysis of steel structures with STATIK-5-STAHL and detail-ing with Prosteel-3D 17

Athens, May, 24 & 25.
Applications to participate up to April 30.



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