Raw Materials for Portland Cement

Use Railroad ballast, highway construction, cement and concrete aggregate, raw material for Portland cement, mineral wool, and cinder block. 

Plastic natural ceramic raw materials, consisting predominately of kaolinite, illite and/or montmorUlonite, are accompanied by residual quartz, feldspar, mica, and calcite as well as organic residues. In particular, the hmestone content has been used to distinguish between clay (<4 mass% hme), marly day (4—10 mass% lime), clayey marl (10-40 mass% hme), marl (40-75 mass% hme), calcareous marl (75-90 mass% lime), marly hmestone (90-96 mass% hne), and hmestone (>96 mass% hme). Kaolinitic raw materials formed in situ (autochthoneous) are called kadine, while kaolinitic raw materials found in secondary deposits (aUochthone-ous) are called clays. Marl and marly hmestones are important raw materials for Portland cement production (see Section 5.2.1). 

CAC require large industrial facilities, similar to those used to make ordinary Portland cement. The raw materials for CAC are typically bauxite and limestone, which are ball-milled and mixed together to form a feed of appropriate composition, which is fed into rotary kilns to form a calcium aluminate clinker. The clinker is ball-milled to produce the cement. Analysis for composition and mineralogy at various stages of manufacture are essential to ensure a consistent product, see for example Chakraborty and Chattopadhyay [32] for a discussion of the bulk processing of high alumina CAC. 

Where sewage sludge is incinerated, the resulting ash also requires disposal. It has been suggested [28.10] that, as the ash contains Si02, AI2O3 and Fe203, it could be used as a raw material for the production of Portland cement, particularly if the lime-based process were used. 

Presenting the rules of Portland cements classification and derived from them others kind of hydraulic binders, it must be underlined that the basis of this classification are their useful properties. In relation to this that cement is an intermediate product—the raw material for concrete production, these properties will concern the corrverrtiorral rrricro-concrete or the mortar, sometimes paste, and now and again cemerrt itself for example phase composition. Some experts reckon the mortar to some kirrd of concrete, however, it is a subject of controversy. 

A chemical analysis alone cannot describe the form, particle size, or mineralogy of the feed. SiO from a chemical analysis does not necessarily mean quartz, nor does Fe Oj necessarily imply hematite. Analysis by X-ray diffraction (XRD) quite accurately records most of the detectable mineralogical varieties and with calibrated standards allows an estimation of abundance. But XRD cannot elucidate the particle form or size, and virtually misses the occurrence of amorphous materials such as glass or poorly crystalline materials such as limonite, FeO(OH), a major constituent in many iron sources for portland cement. Phases below the detection limit by XRD can easily be seen in the microscope. However, chemical and XRD analyses of each of the raw materials individually, in sieved fractions, and in their blended combination in the feed, are immensely helpful, indeed strongly recommended, for routine... 

The problem of using phosphogypsum as a raw material for comlined sulfuric acid and cement production has drawn the attention of various companies. A cement/ sulfuric installation was proposed in 1990/91 for the Pine Level FVoject at Consolidated Minerals, Inc. [17]. It was to be a part of the integrated complex comprising a 1.0 million tpy P2O5 phosphate fertilizer plant, a 2.35 million tpy portland cement plant, a 660-MW coal-fired power station, and a 4.5 million tpy preconcentrate phosphate mine, with 0.9 millim tpy of sulfur equivalent recycled. 

Solid waste such as tires has been use in cement kilns as fuel supplement for making Portland cement. In an Atlanta, Georgia, plant, the use of tires has decrease the plant s air emissions by up to 30% and allows the company to meet tighter nitrogen oxides (NO c) guidelines [94], The use of carpet waste in cement kilns is also quite attractive and an effort is being made in this direction [95]. The relatively high fuel value of carpet polymers can reduce the need for fuels, and the calcium carbonate in carpet becomes raw material for cement. 

Sodium chloride, gypsum, and potassinm salts are all important minerals that are recovered as evaporites remaining from the evaporation of seawater and from brines pumped from below the ground. Sodium chloride in the form of mineral halite is used as a raw material for the production of industrially important sodium, chlorine, and their compounds. It is used directly to melt ice on roads, in foods, and in other applications. Potassium salts are, of course, essential ingredients of fertilizers and have some industrial applications as well. Gypsum, hydrated calcium sulfate, is used to make plaster and wallboard and is an ingredient in the manufacture of portland cement. 

Table 1 shows the typical chemical composition of municipal wastes incineration ash generated in Japan. It is apparent that the ash is suitable as raw material for cement production because it contains large amounts of Si02, AI2O3, Fe20s, and CaO which are the main components of the ordinary Portland cement. Moreover, the trace components shown at the bottom of Table 1 are considered to affect the clinker formation reaction or product hydration or both. Therefore, it is important to examine the influence of zinc oxide because the ash contains a large amount of zinc oxide compared with the other impurities. 

In the manufacture of Portland cement, many otherwise-waste materials can be used either as a substitute for the traditional raw material, or as a secondary fuel (e.g., used tires) [334,1577]. In particular, drilling wastes can be introduced in the clinker burning process [878]. For both waste disposal and cement manufacturers, a mutual benefit will emerge. The cement manufacturing companies reduce their demand for traditional raw materials and save the limited capacity of landfills and other waste-treatment industries. 

In order to obtain the desired selling qualities in Ihc finished cement, there is added to the clinker about 2% of gypsum (calcium sulfate. CaSOj 2H2O), and ihe mixture is pulverized very finely. For every ton of Portland cement shipped, over two and one-half tons of raw materials and cement clinker must be ground very finely. See Table I. 

Two types of materials are necessary for the production of portland cement one rich in calcium (calcareous), such as limestone or chalk, and one rich in silica (argillaceous) such as clay. These raw materials are finely ground, mixed, and heated (burned) in a rotary kiln to form cement clinker. 

Because of the large supply of sulfur, there is increased interest in its possible use in the construction industry (7-13). This chapter reviews research at The University of Calgary concerned with sulfur in civil engineering applications. Large volumes of materials are required for construction. The amount of sulfur which is available may be compared with the consumption of some of the principal construction materials (Table I). In Canada the annual production of sulfur is already a sizeable fraction of the yearly consumption of some of these materials. For example the annual sulfur production is about half that of raw steel and about three quarters that of portland cement. Elsewhere sulfur production is much smaller than that of presently used construction materials, but there are indications that sulfur production will be increasingly important. 

The enthalpy change on formation of Portland cement clinker cannot be calculated with high precision, mainly because of uncertainties associated with the clay minerals in the raw material. Table 3.1 gives data for the main thermochemical components of the reaction, almost all of which have been calculated from a self-consistent set of standard enthalpies of formation, and which are therefore likely to be more reliable than other values in the literature. The conversion of the clay minerals into oxides is an imaginary reaction, but valid as a component in a Hess s law calculation. Few reliable thermochemical data exist for clay minerals those for pyrophyllite and kaolinite can probably be used with sufficient accuracy, on a weight basis. 

Phosphate bonded ceramics have several advantages over their cements. Unlike polyalkenoate cements, phosphate based ceramics are entirely inorganic and nontoxic. Unlike Portland cement, which is formed entirely in an alkaline solution, these are acid-base cements, and are neutral. They are stable in a wider range of pH, and since they are made from natural minerals, the raw materials needed for their manufacture are readily available. For the same reason, they are also less expensive compared to other acid-base cements. They are self-bonding, i.e., a second layer will bond intimately to a first set layer. These attributes motivated further research into phosphate bonded materials for... 

XRD (Cu Ka) data for (A) raw Portland cement clinker, (B) Residue 1 from which most of the C3S has been removed and (C) Residue 2 from which C3S and C2S have been removed. Silicate phase extraction was conducted using a salicylic acid methanol (SAM) mixture using the method described by Taylor." In Residue 2 the presence of the alkali sulfate phases [denoted Arc for arcanite K2SO4 and Ap for aphthitalite K3Na(S04)2] is clearly evident. Notably, the material used in these plots was derived from a different cement plant to the one illustrated in Figure 10. 

Portland cement was invented in 1824. The raw materials used in its manufacture are limestone, quartz sand, clay and iron ore. These supply the necessary ingredients lime, silica, alumina, and iron. Properly proportioned quantities of the raw materials are pulverized and fired to result in cement clinkers. These are finely ground and mixed with up to five percent gypsum to make the finished product. Thousands of tons are produced annually in the USA. A small percentage of this total is used for grouting. 

The most widely used form of calcium sulfate is the dihydrate, gypsum, which is an important raw material in the construction industry. It is used in the manufacture of Portland cement, in specialized plasters (known as gypsum plasters) for walls, in the production of wallboard, and in cement blocks and mortars. Gypsum is also used extensively in agriculture as a conditioning agent that adds both calcium ions (Ca2+) and sulfate ions (S042-) to the soil. The compound is also used as a raw material in the synthesis of other calcium compounds and in the production of plaster of Paris. 

The high purity of some limestones has been exploited for many centuries by the lime-burning, glass-production, and metals-refining industries. The development of Portland cement in the 19th century caused a major expansion in the demand for limestone, both as a raw material and as an aggregate. This expansion permitted the exploitation of some of the softer and/or less pure deposits such as chalk and marl. 

In many countries, cement production represents the second largest outlet for limestone and is exceeded only by the use of limestone for aggregate in construction and building. The world production of Portland cement is in the order of 1420 million tonnes per year [9.1]. The amount of limestone required varies with the grade of cement and the raw materials used, but is estimated to be approximately 1.0 tonne per tonne of cement. Thus the global cement industry uses roughly 1,400 million tonnes per year of limestone, or about 32 % of the extracted limestone. 

---