“ I n t h e n a m e o f A l l a h , t h e B en en ef ef i c en en t , t h e M er c i f u l ”
A TO TO Z IN CEMENT INDUSTRY UNI T ONE UNI ONE Sourc our ce of of Raw Raw Mat M ater erii al 1.0 Source of of Raw Raw Mater Mat erial ial The basis for all business in cement industry is adequate supplies of raw material. This raw material is found in nature in form of rock formations. In order to find and secure sufficient reserves of such rock formations exploration work is conducted. The actual production is gained from open cast mining of a raw material deposit (any volume of rock can represent a raw material deposit) in most cases. It becomes very evident that the meaning of a quarry is to dig a hole into the landscape. Considering the fact that for the production of clinker certain qualities of rock are needed, it is of paramount interest to the plant to know beforehand what type of rock and what quality will be encountered within the mountain behind the quarry faces. This need for information before mining starts is the classical problem of exploration. Two main aspects are to be considered: 1) Geometry of the raw material deposit that means geological boundaries like interfaces of formations, faults and also topography. 2) Quality of the rocks in terms of chemical and mineralogical composition, physical characteristics like hardness, abrasiveness, and pozzolanic activity. Obviously this task of exploration is not a simple one. Our means of acquiring data is limited compared to the large size of rock volumes to be investigated. Exploration drillings provide precise but also very spotty information on the rock volumes. In order to fill the gaps between drill holes and also in order to interpret results of drillings, we need a model of the raw material deposit. This model is developed with the help of the natural science (Geology). Within this science, all aspects with respect to rock formation, deformation and transformation are studied and general rules are established. These concepts of geology are absolutely instrumental for the interpretation of any raw material deposit deposit .
1.1 Str Struc uctur tur e of the Eart Earth h There is enough scientific evidence to assume that the earth consists of a series of zones (fig-1.1) which differ distinctly from one to other in their chemical and physical characteristics. The earth's center is a solid core of nickel and iron, surrounded by a zone of liquid material (liquid core). The mant mant le lying l ying betw betwee een n the t he core and and the th e c crust rust is divided into int o two t wo sect sect ions: ions: t he mantl mantl e as as suc such h and the th e "upper" mantle. Both are chemically characterized by the abundantly present sulphur-oxygen compounds combined with heavy metals. The crust itself can be divided into two portions, the oceanic oceanic crust (S ( Si licon, li con, Magnesium Magnesium and Iron as ma maii n elements) element s) and and the t he continental conti nental crust crust (Silicon il icon and Alumina).
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Figure-1.1: Structure of the Earth
Compared with the other structural elements of the earth, the crust is a very thin layer of an average thickness of only 30 km (fig-1.2). The crust and the upper mantle together form the lithosphere, which forms a solid plate of rock of about 100 km thickness.
Figure-1.2: Crust
1.2 Composition of the Lithosphere Only approx. 10-15 km of the lithosphere has been sufficiently investigated to permit characterization (fig-1.3). It is astonishing that the predominant components in that portion of the lithosphere which are accessible for industrial processing are oxygen (50 %) and silicon (25 %), (table-1.1a, table-1.1b). The remaining 25 % are formed by eight other elements and a mere 0.8 % by the remaining 82 naturally occurring elements, many of which are technically and industrially important.
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Figure-1.3: Lithosphere
Component O i Al Fe a Na K Mg
% 46,6 27,7 8,1 5,0 3,6 2,8 2,6 2,1
Table-1.1a: Composition of t he lit hosphere
Component Oxygen O Silicon Si Aluminium Al Iron Fe Calcium Ca Magnesium Mg Potassium K Sodium Na Hydrogen H Nickel Ne Titanium Ti
Earth 22.0 11.0 0.6 50.0 1.0 9.0 6.0 -
Lithosphere 46.6 27.7 8.1 5.0 3.6 2.1 2.6 2.8 0.9 0.6
Portland Cement 37.0 9.5 3.2 2.0 45.3 1.2 0.5 0.1 -
Table-1.1b: Chemical composit ion of t he earth, lithosphere & Port land cement
1.3 Global Plate Tectonics Plate tectonics is the study of the structure of the Earth and how the Earth's surface changes according to the movement of t ectonic plates. Plate t ectonics is responsible for t he formation of the most spectacular natural features on Earth such as mountain belts, volcanoes, rift valleys, hot springs and mid-ocean ridges (fig-1.4).
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Figure-1.4: Global Plate Tectonics Model
Figure-1.5: Plates Boundary
Three types of plate boundaries exist, characterized by the way the plates move relative to each other (fig-1.4, fid-1.5). They are associated with different types of surface phenomena. The different types of plate boundaries are: 1.3.1 Convergent Boundaries Places where plates crash or crunch together are called convergent boundaries. Plates only move a few centimetres each year so collisions are very slow and last millions of years. The edge of the continental plate in the drawing (fig-1.4, fig-1.5) has folded into a huge mountain range while the edge of the oceanic plate has bent downward and dug deep into the Earth. A trench has formed at the bend. All that folding and bending makes rock in both plates break and slip causing earthquakes.
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1.3.2 Divergent Boundaries Places where plates are coming apart are called divergent boundaries. As shown in the drawing (fig1.4, fig-1.5) when Earth's brittle surface layer (the lithosphere) is pulled apart, it typically breaks along parallel faults that tilt slightly outward from each other. When the plates separate along the boundary the block between the faults crack and drops down into the soft plastic interior (the asthenosphere). The sinking of the block forms a central valley called a rift. Magma (liquid rock) seeps upward to fill the cracks. In this way, new crust is formed along the boundary. Earthquakes occur along the faults and volcanoes form where the magma reaches the surface. 1.3.3 Transform Boundaries Places where plates slide past each other are called t ransform boundaries. Since the plates on either side of a transform boundary are merely sliding past each other and not tearing or crunching each other, transform boundaries lack the spectacular features found at convergent and divergent boundaries (fig-1.4, fig-1.5). Instead, transform boundaries are marked in some places by linear valleys along the boundary where rock has been ground up by the sliding. In other places, transform boundaries are marked by features like stream beds that have been split in half and the two halves have moved in opposite directions.
1.4 Rock Classification Rocks are classified according to these three crit eria; mineral content, genesisand place of formation, and age. Accordingly, three large groups (each of them divided into several subdivisions) can be established: igneous rocks, sedimentary rocks, and metamorphic rocks. Igneous rock can change into sedimentary rock or into metamorphic rock. Sedimentary rock can change into metamorphic rock or into igneous rock. Metamorphic rock can change into igneous or sedimentary rock. The rock cycle is an illustration that is used to explain how the three rock types are related to each other and how Earth processes change a rock from one type to another through geologic time. Plate tectonic movement is responsible for the recycling of rock materials and is the driving force of the rock cycle (fig-1.6).
Figure-1.6: Rock Cycle
1.4.1 Igneous Rocks (or Fire Rocks) The magma which originates from the deeper part of the globe (mostly the upper mantle) rises towards the surface and forms different types of rocks depending on its cooling history and its differentiation process. The magma can change its chemical composition by fractional crystallization and by assimilation of rock fragments of the formations it penetrates. Slow cooling of the magma leads to the development of large crystals, rapid cooling e.g. in a volcano eruption leads to very small crystals or even amorphous matter in form of volcanic glass (fig-1.7).
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Figure-1.7: Formation of Igneous Rocks
Rocks of this type (table-1.2) are often used in cement and aggregate industry, e.g. as Pozzolana or crushed rock (granite, basalt). Volcanics Plutonics Intrusive
Tuff, Ash, Lava, Perlite, Agglomerate Granite, Diorite Andesit e, Basalt
Table-1.2: Igneous Rocks in Cement & Aggregate Industries
1.4.2 Sedimentary Rocks Sedimentary rocks form if rocks of any kind are exposed to weathering and erosion caused by temperature changes, atmospheric conditions, etc. on the surface of the earth (fig-1.8). Basically, weathering includes two phenomena, weathering with undissolved product s & weathering with dissolved products. The formation of sediments includes the following stages: 1) Disintegration of the solid rock 2) Transport of dissolved and undissolved products 3) Deposition and precipitation 4) Compaction According to these stages; three types of sedimentary rocks are distinguished: 1) Mechanical (Classics) Sedimentary Rocks: Only mechanical action 2) Chemical Sedimentary Rocks: Precipitation of dissolved matt er 3) Organic Sedimentary Rocks: Remains of living beings precipitation by organisms
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Figure-1.8: Formation of Igneous Rocks
Sedimentary rocks tell us what the Earth's surface was like in the geologic past. They can contain fossils that tell us about the animals and plants or show the climate in an area. Sedimentary rocks are also important because they may contain water for drinking or oil and gas to run our cars and heat our homes. Sedimentary rocks are also the most significant resource for the cement and aggregate industry (table-1.3). Chemical Mechanical Organic
Limestone, Gypsum anhydrite, Ironoxihydrate, Aluminiumoxihydrate, Rock salt Sandstone, Sand, Marl, Clay, Claystone shale Limestone, coal, Oil
Table-1.3: Sedimentary Rocks in the Cement Industr y
1.4.3 Metamorphic Rocks During rock formation, every mineral and rock is in equilibrium with its environment at a distinct pressure (P) and the temperature (T). Metamorphosis (transformation) of rocks is mostly caused by disturbance to this equilibrium. If one or both of these parameters change, metamorphosis takes place. Metamorphic rocks may therefore be formed from igneous as well as from sedimentary rocks, whereby the chemistry of the metamorphic rock may be virtually identical with the composit ion of the original rock. Metamorphic limestone (marble) is often used as a raw material in cement industries (table-1.4). Other metamorphic rocks are suitable as aggregates, even for special applications (e.g. Amphibolites) as aggregates. Metamorphic Rock Amphibolite Marble Phyllite Quartzite
Original Rock Basalt Limestone Shale Sandstone
Table-1.4: Metamorphic Rocks in the Cement Industry
Note that a rock cannot only be classified according to its mineral content and the place of its formation, but also according to its age. The determination of t he age of a rock is normally accomplished by Paleontological methods (investigation of the remainders of fossils) or by physical methods (radiocarbon, radio-active decay).
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