CEMENT FROM CLINKER

Cement is a material that binds together solid bodies (aggregate) by hardening from a plastic state. Many materials act as adhesives or cement according to this definition. The cement referred to above, which is used for civil engineering and the construction industry, is portland cement. Portland cement is hydraulic and develops strength primarily by the hydration of the di- and tri-calcium silicates it contains. Hydraulic means that the paste of cement and water will harden under water. Lime, on the other hand, will harden due to the reaction with carbon dioxide from the air.

Clinker is a nodular material produced in the kilning stage during the production of cement and is used as the binder in many cement products. The lumps or nodules of clinker are usually of diameter 3-25 mm and dark grey in color. It is produced by heating limestone and clay to the point of liquefaction at about 1400°C-1500°C in the rotary kiln. Clinker, when added with gypsum (to control the setting properties of cement and ensure compressive strength) and ground finely, produces cement. Clinker can be stored for long periods of time in a dry condition without degradation of quality, hence it is traded internationally and used by cement manufacturers when raw materials are found to be scarce or unavailable.

Since the cement industry requires high investment capital, high quality (tenor) and reserves are needed to start the necessary investment in the sector. The chemical properties of the ore beds used in cement production, as well as their chemical properties, closeness to the plant, their removability, fragility, grindability and burnability, low moisture content and homogeneity are the most important factors affecting the production cost. In addition, the use of alternative raw materials can further enhance the existing mine life and mineral quality.

The realization of high quality targets placed on cement in large quantities with a high potential for substitution and future cement depends on the availability of alternative raw materials or industrial by products. Turkey stone, cement and ceramics industry, depending on the demand for primary and secondary raw materials, is expected to increase until 2030, raw material requirements. The raw materials required for cement production are limestone, clay and iron ore. In addition, some gypsum is added to the cement. All these materials are supplied from mines. Energy and fuel are consumed during production and transportation. Another important issue is the rapid depletion of resources. In addition to cement raw materials for the reduction of natural resources; sludge, gypsum, gypsum waste, bleaching waste, sludge waste, casting sand, iron dust, tufal, gypsum, fly ash, iron slag and excavation soil sludge land etc. materials are used as an alternative to cement raw materials. These alternative raw materials are added to the raw mixture of cement at a certain rate to form the composition of the cement.

Mudstone is a fine-grained, degradable sedimentary rock composed of clay and mud. Shales, also called mudstone or claystone, were formed millions of years ago by the deposition and accumulation of very small clay particles that broke off from an old rock mass that had been eroded by rainwater and rivers. Over time, the deposits on the bottom of the new deposits accumulated on top of the pressure have become a solid rock. The density of the sludge ore in the land is assumed to be 2.0?g / cm3 on average. Since the clay mineralization is in a hard structure, production can be carried out by performing drilling-blasting and size reduction processes in stages during the production activities by using open operation method in quarries.

In the study area, the thickness of the mudstone ore is around 60?m on average. The reserve amount was set at approximately 11.987.760?tonnes considering the field work and the area planned to be studied with ore propagation.

The mudstone consists mostly of shafts (4–62 microns) and clay (4 microns) in size. Claystone is generally very fine-grained and homogeneous, separated from the shaft stone (siltstone). Shales are characterized by the ability to separate the leaves along stratigrafi parallel to the bedding. Many shales are laminal. The mud stones do not show lamination, and when broken, the crust is broken and massive. Marn is a limy mud stone.

The formation consists of red-burgundy micritic limestone and limestone mudstone alternations. Inözü anticline and Kavak County, located in the NW section of the study area, are located on the wings of anticlines and synclines between Sarialan and Belalan villages (figure below). The formation is a typical example of the Kapikaya Summit. The unit is a thin-medium bedded red-burgundy biomicrit and pelagic limy mudstone alternation. Within the limestones, pink-beige colored chert ovules and thin-bedded volcanic intermediate bands are seen. The thickness varies between 53–106?m. The Kapan Throat formation was identified as Santonian-Campanian based on the Globotruncana fauna. The formation was precipitated in a calm and deep sea environment.

Portland cement is the basic ingredient of concrete. Concrete is formed when portland cement creates a paste with water that binds with sand and rock to harden. Cement is manufactured through a closely controlled chemical combination of calcium, silicon, aluminum, iron and other ingredients.

Common materials used to manufacture cement include limestone, shells, and chalk or marl combined with shale, clay, slate, blast furnace slag, silica sand, and iron ore. These ingredients, when heated at high temperatures form a rock-like substance that is ground into the fine powder that we commonly think of as cement.

Cement plant laboratories check each step in the manufacture of portland cement by frequent chemical and physical tests. The labs also analyze and test the finished product to ensure that it complies with all industry specifications.

The most common way to manufacture portland cement is through a dry method. The first step is to quarry the principal raw materials, mainly limestone, clay, and other materials. After quarrying the rock is crushed. This involves several stages. The first crushing reduces the rock to a maximum size of about 6?in. The rock then goes to secondary crushers or hammer mills for reduction to about 3?in. or smaller.

The crushed rock is combined with other ingredients such as iron ore or fly ash and ground, mixed, and fed to a cement kiln.

The cement kiln heats all the ingredients to about 2700 degrees Fahrenheit in huge cylindrical steel rotary kilns lined with special irebrick. Kilns are frequently as much as 12 feet in diameter large. The large kilns are mounted with the axis inclined slightly from the horizontal.

The finely ground raw material or the slurry is fed into the higher end. At the lower end is a roaring blast of flame, produced by precisely controlled burning of powdered coal, oil, alternative fuels, or gas under forced draft.

As the material moves through the kiln, certain elements are driven off in the form of gases. The remaining elements unite to form a new substance called clinker. Clinker comes out of the kiln as grey balls, about the size of marbles.

Clinker is discharged red-hot from the lower end of the kiln and generally is brought down to handling temperature in various types of coolers. The heated air from the coolers is returned to the kilns, a process that saves fuel and increases burning efficiency.

After the clinker is cooled, cement plants grind it and mix it with small amounts of gypsum and limestone. The cement is now ready for transport to ready-mix concrete companies to be used in a variety of construction projects (Fig. below).

Clinker quality depends on raw material composition, which has to be closely monitored to ensure the quality of the cement. Excess free lime, for example, results in undesirable effects such as volume expansion, increased setting time or reduced strength. Several laboratory and online systems can be employed to ensure process control in each step of the cement manufacturing process, including clinker formation.

Cement is a material with adhesive and cohesive properties which make it capable of bonding minerals fragments into a compact whole. For constructional purposes, the meaning of the term “cement” is restricted to the bonding materials used with stones, sand, bricks, building stones, etc.

TYPES OF CEMENTS:

Cement may be hydraulic or non-hydraulic: 1) Non-hydraulic cements (e.g. gypsum plaster) must be kept dry in order to retain their strength. 2) Hydraulic cements harden because of hydration, chemical reactions that occur independently of the mixture’s water content; they can harden even underwater or when constantly exposed to wet weather. The chemical reaction that results when the anhydrous cement powder is mixed with water produces hydrates that are not water-soluble. Hydraulic cement may be: i) Portland cements ii) Natural cements iii) Expansive cements iv) High-alumina cements.

PORTLAND CEMENT:

It is hydraulic cement that hardens in water to form a water-resistant compound. Made by finely clinker.

The cements of interest in the making of concrete have the property of setting and hardening under water by virtue of a chemical reaction with it and are, therefore, called hydraulic cement.The name “Portland cement” given originally due to the resemblance of the color and quality of the hardened cement to Portland stone – Portland island in England.

Portland cement is the most common type of cement in general usage in many parts of the world, as it is a basic ingredient of concrete, mortar, stucco and most non-specialty grout. It is a fine powder produced by grinding Portland cement clinker (the solid material produced by the cement kiln stage that has sintered into lumps or nodules, typically of diameter 1-25 mm) (more than 90%), a maximum of about 5% gypsum which controls the set time, and up to 5% minor constituents (as allowed by various standards). As defined by the European Standard EN197.1, “Portland cement clinker is a hydraulic material which shall consist of at least two-thirds by mass of calcium silicates (3CaO.SiO2 and 2CaO.SiO2), the remainder consisting of aluminium- and iron-containing clinker phases and other compounds. The ratio of CaO to SiO2 shall not be less than 2.0. The magnesium content (MgO) shall not exceed 5.0% by mass.”