Many people use the words cement and concrete interchangeably. However, these are actually two, somewhat different things. Cement is the grey powdery stuff that when mixed with sand, rock, gravel and water forms concrete. The concrete is the final product used in buildings, roads, infrastructure, etc.
- You can think of cement as the “glue” that holds the sand and gravel and re-bar (reinforcement bar) together to make concrete.
- Cement manufacturers mine and process raw materials and put them through a chemical reaction process to create cement.
- They need to understand the chemical composition of the raw materials so that the reaction in their process takes place correctly and they make good, high quality cement that will eventually be used to make concrete by contractors and “ready-mix” companies.
You might think of a cement manufacturing facility as an extension to a mining operation, as cement plants are typically located central to the minerals required to make the cement, which saves the transportation costs and reduces the price of the cement.
Limestone is one of the key minerals used in cement making. Limestone is a sedimentary rock composed mostly of the calcium carbonate (CaCO 3 ) and, according to the Mineral Education Coalition, comprises about 15% of the Earth’s sedimentary crust. Surface mining is the general excavation method. There are a few underground limestone mines, but most are pits on the surface.
These limestone mines are found in places you might not think to look. The American Geosciences Institute reports that Iowa – which is usually known for its corn — produces about 35 million tons of raw materials from its pits and quarries where gravel deposits and limestone bedrock are close to the land surface.
- Cement manufacturers depends on these mines, and others that provide additional minerals.
- According to Mine-Engineer.com, “Cement manufacture, like many other manufacturing processes, begins at the mine, where the raw materials like limestone, silica, aluminates, feric minerals and others are obtained.
Some typical materials used for calcium carbonate in cement manufacturing are limestone, chalks, marbles, marls, and oyster shell. Some typical materials used for alumina in the cement manufacturing are shale, clay, slags, fly ash, bauxite, alumina process waste, and granite.
Some typical materials used for silica in cement manufacturing are sand, clay, claystone, shale, slag, and fly ash. Some typical materials used for iron in cement manufacturing are iron ores, blast furnace flue dusts, pyrite clinker, mill scale, and fly ash.” Cement manufacturers must process the selected and prepared mineral raw materials to produce the synthetic mineral mixture (clinker) that can be ground to a powder having the specific chemical composition and physical properties of cement.
There are different types of cements, with differing compositions, depending upon use. As we noted in a previous article, The Cement Manufacturing Process, to ensure quality and correct composition, several laboratory and online systems utilizing sophisticated technologies must be employed.
Online elemental analyzers provide high frequency online elemental analysis of the entire raw material process stream using Prompt Gamma Neutron Activation Analysis (PGNAA) or Pulsed Fast Thermal Neutron Activation (PFTNA). With the option to use either a neutron generator or a radio-isotope for excitation, the system delivers consistent stockpile and raw mix chemistry improving kiln efficiency and minimizing production costs.
Some technologies enable you to achieve excellent process control and save fuel in your cement plant with both chemical and phase analysis in one simple operation. A cement analyzer can combine X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD) technologies for a better and more complete characterization of any given crystalline sample.
Various compounds can be controlled like quartz in raw meal, hot meal, free lime in clinker, clinker phases, additions in cement, e.g. limestone, GBFS or pozzolan or even clinker content in cement. Clinker phase analysis ensures consistent clinker quality, which is the key to high-performance concrete.
Cement quality control laboratories face demanding elemental analysis requirements to determine major and minor oxides in clinker, cement and raw materials such as limestone, sand and bauxite. Some cement analyzers in the lab use dispersive X-ray elemental analysis technology and can be pre-configured for dedicated cement applications that can help ensure high precision, outstanding repeatability and stability.
- You can read more about these technologies in our Cement, Coal & Minerals Learning Center and in the articles listed below.
- It’s obvious that since cement is one of the main ingredients of concrete, it is vital to construction materials.
- The concrete must have high compressive strength, fire resistance, moldability, impermeability and durability, so knowing the composition is essential.
Lives are at stake. If the concrete for houses, hospitals, schools, offices, shops, roads, bridges, and dams fails, it could have catastrophic consequences. Safety starts with quality cement that meets specifications, because it’s the glue that holds everything together.
Read XRF/XRD Combined Instrumentation Can Provide Complete Quality Control of Clinker and Cement to learn more about technology that combines the advantages of both XRF and XRD together. Read Analysis of Clinker and Cement with Thermo Scientific ARL OPTIM’X WDXRF Sequential Spectrometer to learn why XRF is the technique of choice for elemental analysis in cement industry. Read PGNAA Improves Process and Quality Control in Cement Production to learn what makes PGNAA particularly suited for cement analysis.
What are the main materials used in cement production?
The main materials used in cement production are minerals containing calcium oxide, silex, alumina and iron oxide. These components are rarely found in one type of raw material; therefore, for the cement production the raw mix is selected for the following components: CARBONATE COMPONENT (rich in calx) is contained in the raw mix in a quantity of 76-80%:
Limestone. Mohs hardness is 1.8-3.0. The older the geological fraction, the firmer. One of the varieties of lime spar is marble. Unlike limestone, it has a looser, earthy structure; therefore, it refers to specifically designed raw materials for wet production. Chalk is soft raw material, it does not require crushing. Marl is a limestone with admixtures of silex and clay substances, as well as iron oxide.It is a transitional stage to clay. The hardness of marl is lower than the hardness of limestone The more clay substances, the lower its hardness. This is an excellent raw material for cement production.
Each of these materials has different grinding coefficient. The higher grinding coefficient, the more grinding of this material. The grinding factors for base raw materials in cement production are given in table below.
|Rotary kiln clinker
|Shaft furnace clinker
|Granulated blast-furnace slag
CLAY COMPONENT (contains little lime) Clay minerals have a fine-grained structure; the grain size does not exceed 2 microns. CORRECTIVE ADDITIVES Corrective additives are added in cases where the chemical composition of the raw mix does not meet the established requirements.
- For example, sand, tripoli are used to increase silica.
- With a lack of iron oxide to reduce the clinker sintering temperature and increase the saturation coefficient, add pyrites cinder, iron ore.
- This results in saving gas during burning.
- Carbonate and clay components are used to provide the necessary content of CaCO3.
They have different carbonate components of CaCO 3 (titer). The carbonate component contains up to 97% CaCO3, clay contains about 10%. It is necessary to achieve, for example, a titer of 80%. Therefore, there are sludge pools with high and low titer content on cement plants.
The sludge from pools is mixed in certain proportions. In this connection, each cement plant has its own, unique composition of raw materials for production of finished goods. For example, a mixture of materials used by some cement plants in Ukraine. – limestone, clay, slag; – marl, chalk; cinder 2.5%; – limestone, clay + loam, corrective additives; – limestone-coquina; reddish clay; – coal washing, cake, cinder; – marl, loam, pyrite cinder.
The choice of composition of materials mixture with useful components generally is determined by plant’s geographical location and delivery of raw materials. The only common feature in all cement production plants is the difficulty of grinding the source material as the material is hard enough and has high abrasiveness.
Is cement a mineral?
Is Cement a Mineral? – No, cement is not a mineral. Cement fails most of the mineral question, with the exception of the requirement that it be inorganic. Concrete is usually a bunch of materials ground up together, mixed with water, and then allowed to harden.
- The formula for cement varies across the board, and is as unlikely as concrete to be exactly the same anywhere in the world.
- In general, cement is also man-made like concrete, which disqualifies it as a mineral.
- That being said, one could argue that cement could be considered a mineral if only one substance was being used to make it, such as the mineral calcite.
But even then, we think of this as a pretty poor argument, because water must still be added to the powdered mix to make the “glue/paste.” Interested in learning about other common substances, and whether they’d be considered a mineral? Check out our mineral articles about: sand, dirt, hydrogen, seawater, sugar, glass, plastic, air, steel, and gravel,
How many types of minerals are used in the cement industry?
Minerals Used in Cement Industry (Set of 15) – This Collection contains 15 Types of Minerals Specimens Used in Cement Industry. This Kit include Some of the following Minerals Asbestos, Barytes, Bauxite, Calcite, Clay, Feldspar, Flourite, Gypsum, Laterite, Lignite, Lime Stone, Mica, Pumice, Red Ochre & Silica Sand etc.
|Paper Mounted Showcase
What is cement used for?
Cement powder, here conditioned in bag, ready to be mixed with aggregates and water. Dispersing dry cement dust in the air should be avoided to prevent health issues. Cement block construction examples from the Multiplex Manufacturing Company of Toledo, Ohio, in 1905 A cement is a binder, a chemical substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel ( aggregate ) together.
- Cement mixed with fine aggregate produces mortar for masonry, or with sand and gravel, produces concrete,
- Concrete is the most widely used material in existence and is behind only water as the planet’s most-consumed resource.
- Cements used in construction are usually inorganic, often lime or calcium silicate based, which can be characterized as hydraulic or the less common non-hydraulic, depending on the ability of the cement to set in the presence of water (see hydraulic and non-hydraulic lime plaster ).
Hydraulic cements (e.g., Portland cement ) set and become adhesive through a chemical reaction between the dry ingredients and water. The chemical reaction results in mineral hydrates that are not very water-soluble and so are quite durable in water and safe from chemical attack.
- This allows setting in wet conditions or under water and further protects the hardened material from chemical attack.
- The chemical process for hydraulic cement was found by ancient Romans who used volcanic ash ( pozzolana ) with added lime (calcium oxide).
- Non-hydraulic cement (less common) does not set in wet conditions or under water.
Rather, it sets as it dries and reacts with carbon dioxide in the air. It is resistant to attack by chemicals after setting. The word “cement” can be traced back to the Ancient Roman term opus caementicium, used to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder.
- The volcanic ash and pulverized brick supplements that were added to the burnt lime, to obtain a hydraulic binder, were later referred to as cementum, cimentum, cäment, and cement,
- In modern times, organic polymers are sometimes used as cements in concrete.
- World production is about four billion tonnes per year, of which about half is made in China.
If the cement industry were a country, it would be the third largest carbon dioxide emitter in the world with up to 2.8 billion tonnes, surpassed only by China and the United States. The initial calcination reaction in the production of cement is responsible for about 4% of global CO 2 emissions.