Portland cement chemical composition

Concrete Bridge Protection and Rehabilitation Chemical and Physical Techniques—Corrosion Inhibitors and Polymers. Discusses the improvement of existing non-electrochemical methods for protecting and rehabilitating chloride-contaminated concrete w ith and without concrete removal and the development of new methods. Five corrosion inhibitors were evaluated and service lives were estimated for the two most effective treatments. Asphalt Portland cement concrete composite (APCCC) was designed and evaluated, and compared with hot-mix asphalts and Portland cement concrete for strength properties, resistance to freeze-thaw and resistance to chloride intrusion. 248 pages. SHRP-S-666... 

Portland cement is manufactured by two basic processes, the wet process and the dry process. The dry process uses approximately 25% less energy per ton of Portland cement and is used to produce about 68% of the U.S. Portland cement. Both processes start by mixing selected raw materials, cmshed and/or milled to approximately s in. (1.9 cm) diameter, in the correct ratios to give the final desired chemical composition. 

Cement. Portland cement, a mixture of calcium siUcate and calcium aluminate minerals, is produduced by the calcination of argillaceous limestone or mixtures of limestone and clay (see Cement). Although other clays can be used, ka olin is preferred because of its alumina and siUca content and low level of impurities. It is especially desirable in the manufacture of white cement and other types requiring careful control of chemical composition. Air-floated ka olin, because of its low cost, is usually used. 

The commercial product is actually a blend of different cements. This blending leads to a more constant quality. The chemical composition of Portland cement is typically 60% to 69% CaO, 18% to 24% Si02, 4% to 8%... 

Although low in volume compared with other foundry solid waste, baghouse dust may still be used beneficially in the production of portland cement. This opportunity arises from its attractive mineral composition silica, clay, and metal fines, which are needed in the cement kiln. Also, special efforts may be undertaken to characterize its chemical composition and purity. 

Reports of incompatibility between Portland cement and chemical admixtures have increased over the past 10 years. Rapid set, accelerated stiffening, increase in time of set, lack of water-reduction are some of the reported problems. Such effects produced by the interaction of the composition of the cement and that of the chemical admixtures has been often referred to as cement-admixture incompatibility . This is discussed below. 

Pozzolanic S/S systems use portland cement and pozzolan materials (e.g., fly ash) to produce a strucmrally stronger waste/concrete composite. The waste is contained in the concrete matrix by microencapsulation (physical entrapment). It is a chemical treatment that uses commercially available soluble silicate solutions and various cementious materials such as cement, lime, poz-zolans, and fly ash. By addition of these reagents and rigorous mixing, the waste is fixed or stabilized. Contaminant mobility is reduced through the binding of contaminants within a solid matrix, which reduces permeability and the amount of surface area available for the release of toxic components. 

Supercritical C02 (sc C02) is being used to accelerate the natural aging reactions (i.e., carbonation) of Portland cement. This treatment method alters the bulk properties of cement, producing profound changes in both structure and chemical composition. As a result of these changes, the mechanical and transport properties of these cements are also dramatically affected, and they display reduced porosity, permeability and pH, as well as increased density and compressive strength. 

The chemical composition of Portland cement, the most frequently used cement for concrete and water mortar, can be seen in Table 6. 

Portland cement and Portland cement with 30% fly ash were used as matrix. Chemical composition, physico-chemical and mechanical properties of cements were determined. The samples lx 1x6 cm were prepared by mixing cement with wastewater containing 10,000 mg F1 Pb2+, 30,000 mg F1 Pb2+, and 50,000 mg F1 Cd2+. The next samples were prepared ... 

Both cements (Table 7) compile with the requirements of the Yugoslav standard JUS B.C1.011, concerning chemical composition. Portland fly ash cement PPC has the expected higher insoluble residue and the loss on ignition regarding Portland cement OPC because of the fly ash addition. Other constituents were not significantly changed with the fly ash addition. 

Table 7 Chemical composition of Portland cement and Portland fly ash cement ...

Particulate composites are used in greater volume than any others because concrete is a particular composite. In many ways, concrete is the archetype of this class of composites. It consists of particles or aggregates of various sizes almost always of mineral materials, bonded together by a matrix of an inorganic cement originally mixed with and hardened by its chemical reaction to water. Many types of particles are employed, at least five different types of Portland cements and several other types of inorganic cements act as binders. 

In many clinkers, the ferrite phase is closely mixed with aluminate due to a similarity in cell parameters, oriented intergrowth can occur (MIS). The close admixture often renders X-ray microanalysis difficult or unreliable. For ordinary Portland cement clinkers, the compositions found in dilferent laboratories are nevertheless remarkably consistent. Table 1.2 includes an average value based on the results of investigations using X-ray microanalysis (H8,K1,B2,U1,H3,B4) or chemical analysis of separated material (Yl). Table 1.3 includes suggested site occupancies corresponding to these data. 

Regulated-set cement and jet cement are modified Portland cements in which the normal aluminate phase is replaced by CuA CaF, through the use of a raw mix containing CaF,. Uchikawa and Tsukiyama (U2I) gave chemical (Table 10.4) and phase compositions of two jet cements. Botli contained approximately 60% of alite, 20% of C, i A CaF,. 1% of belite and 5% of ferrite. Admixtures are required to control the rate of reaction of the C, 1 A CaFj and the nature of the products. One of the cements included a proprietary retarder based on citric acid, togetlier with 2"/o of CaC O, . The other contained 2.5% of hemihydrale. In each case, Na,S04 (T o) and anhydrite were also present. The specific surface areas were around 550 m kg . 

Calcium Silicates Hydrates (CSH) is the major hydration product of Portland Cement. It has been intensively studied for several decades. CSH can be obtained by hydration of C3S and P-C2S or by precipitation fi om aqueous solutions containing a Ca salt and silicate ions. CSH has a wide range of chemical composition. Many studies [1-5] indicate that its molar ratio Ca/Si can vary fixrm 0.7 to 2 (or more) [6] and is in most cases near to 1.7 [7]. There has been indirect evidence that CSH (obtained by reaction between CaO and Silica) has a layered structure similar to that of natural Tobermorite and/or Jennite [8]. Recent solid state NMR [9-10], intfared spectroscopy [11], EXAFS [12] and thermogravimetry works [14] have... 

Table 5.3-8. Typical chemical compositions ol a Portland cement clinker.

Material Ordinary Portland cement was used in the experiment. Chemical composition and physical properties of the cement are given in Table 1 and Table 2 respectively. Aggregates used in the experiment was standard sand satisfying Korean Standard L 5100. Ash from incineration of paper sludge was investigated in this study especially. Chemical composition of the ash is given in Table 3. From the composition of the ash, it can be... 

Table 1. Chemical composition of the Portland cement used in the experiment...

Indirect methods - these are usually based on the measurement of total chemistry which is then apportioned according to an assumed composition for each phase. A very widely used form of this normative calculation is the Bogue method for the estimation of Portland cement phases. The limitations in this approach arise when the actual compositions of individual phases vary from those assumed in the calculation. This frequently occurs in the cement industry, where variance in local materials and production conditions can affect detailed phase compositions. In addition, normative calculation has the potential to be unstable when several phases in the mixture have similar chemical composition. 

Aluminate compositions include calcium aluminate cements, which have high chemical resistance, especially to sulfate, and is also used in refractory applications where ordinary Portland cements would be unsuitable. These same cements are used in bioceramic applications. The bioceramic applications reflect both the high mechanical strength of the calcium aluminate cements and also the biocompatibility of Ca-bearing phases, which bond well with, for example, bone. 

It was concluded that the amount of resin and filler in the chemical composition of the fabricated epoxy PCs had a great influence on identification of the maximum physical strength. The PC specimen with 15% resin and 200% filler resulted in maximum compressive and flexural strength. The tensile strength was maximized with 20% resin and 200% filler. The mechanical strength of fabricated PCs was 4- to 5-fold higher than Portland cement concrete [5],... 

Portland cement powder contains live major constituents. These are complex minerals and are known by their chemical names, mineral names and by a shorthand notation, listed in Table 6.6. There are also traces of other impurities in ordinary cement powder, which may have a large effect on the final strength and durability of the concrete. The composition of typical Portland cement is included in Table 6.6. 

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