Composition of Cements

The composition ranges of particular cement types and cement additives in the three component system Ca0-Si02-AI2O3 are given in Fig. 5,3-1, 

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Dense composites of cemented carbide containing SiC-coated diamond particles can be fabricated without conversion of diamond to graphite. The fracture toughness of the composite is double that of cemented carbide due to the deflection and blocking effects against crack propagation by the dispersed diamond particles. 

Applications of IR and Raman spectroscopy to the study of clinkers and unhydrated cements have been reviewed (B39,B40). The laser Raman microprobe, with which regions of micrometre dimensions on a polished surface may be examined, has been used to investigate structure and crystallinity, especially of the alite and belite (Cl9). Spectroscopic methods for studying the surface structures and compositions of cements are considered in Section 5.6.2. 

There are probably no effective direct methods at present for determining either C-S-H or AFm phases in cement pastes in both cases, this is probably attributable to the low degree of crystallinity. Odler and Abdul-Maula (015) found that determination of AFm phase by QXDA was only semiquantitative. Postulated quantitative phase compositions of cement pastes may, however, be tested by comparing observed and calculated TG curves (Section 7.3.3). 

This section presents a brief account of the concrete-producing materials, namely cement, fine and coarse aggregate, water, air and admixtures. The cement manufacturing process, the composition of cement, type and gradation of fine and coarse aggregate, and the function and importance of the water and air are reviewed. The reader can refer to books and papers on concrete such as the selected references at the end of this section. 

The distinct difference between the carbon isotopic composition of cements and modem formation waters suggests that either the formation waters were completely exchanged after precipitation of... 

TABLE 5.1 Chemical composition of cement and rice husk ash. 

The kinetic hydration of cement is widely studied in the literature and some of these papers reported the chemical, physical and mechanical behaviour [2-5], Simplified models were used by Knudsen[6], Basma et al [7], Schindler and Folliard [8], Bentz [9]. The majority of these models are empirical, based on experimental observations of macroscopic phenomena, and they take into account the effects of curing temperature, water-cement ratio, fineness, particle size distribution and chemical composition of cement [5]. 

Bogue potential cement phase composition of cements... 

Table 1.2 Requirements eonceming the ehemieal composition of cements. (Content of Cr(VI) cannot exceed 2 mg/kg in the case of higher chromium content it must be redueed by addition for example iron(ll) sulphate)...

Phase Composition of Cement Hydrated in Hydrothermal Conditions... 

It is convenient in practice to separate the two temperature ranges, when the phase composition of cement paste subjected to the thermal treatment is discussed up to 100 °C in water vapor under the atmospherie pressure, and at higher temperatures and pressures, corresponding to the pressure of saturated water vapor. 

Fig. 4.60 The rate of heat evolution of Portland cement hardening at temperatures 10, 20 and 40 °C (according to [194]). Composition of cement CjS—57 %, CjS 17%, C3A—7%,...

The phase composition of cement mixture with quartz of variable fineness and mix proportions, autoclaved at temperature 177°C during 8 h was investigated by Dyczek [178]. The C-S-H (I) was found as a main component apart of this phase, the 1.1 nm tobermorite was detected and at 20% quartz addition—o-CjSH. Basing upon the phase composition of the autoclaved 2 n xture... 

Contraction depends on the phase composition of cement. CjA has the highest contraction and C2S— the lowest one. Contraction can be calculated from the molecirlar mass and densities of the substrates and of hydration products of cement corrstituents reactions with water. At simplified assumption that the tobermorite C3S2H3, with derrsity 2.44 g/cm is the product of C3S and C2S reaction with water we have ... 

The autogenous shrinkage depends on the composition of cement and will decrease in the case of cement with mineral additions and this effect will increase with the rise of the share of these additions. It is obvious, because the Itydration or poz-zolanic reaction of these additions occurs more slowly and hence they will remain much longer as the anhydrous paste cotrrponerrL The similar effect is observed in... 

Moreover, the effect of mineral and chemical composition of cement on setting and stiffening of concrete is known, as well as on its strength. 

There is a cormnon opinion that corrosion of concrete needs the liquid environment or at least an atmosphere of high hmnidity. The transport of liquid through the concrete causes the sequence of processes, includiug at first the concrete components of the highest reactivity calcium hydroxide and calcium aluminate hydrates. One can thus conclude that the phase composition of cement has a great impact on the behavior of concrete in any aggressive environment. 

There is a relatively good accordance as the chemical and phase composition, as well as the fineness of cement is concerned. Very well documented results in this field have been presented by Kelham [149,150]. Expansion increases with rise of alite and tricalcium aluminate content. The chemical composition of cement is of... 

This method reflects well the practical conditions becanse the pozzolanie reaction depends on the mineral composition of cement. 

The reaction of ettringite formation is the most important because it is very easy influence on the rate of this phase formation, by changing the composition of cement and thereby the liquid phase compositioa... 

CETIC (Chemical Commission of the Technical Studies Committee of the Cement Industry), "Determining the Mineralogical Composition of Cement Clinker by Microscopic Analysis and Selective Dissolution of the Phases," Revue des Materiaux de Construction, 4/78 (713), 1978, pp. 205-211. 

The main difference in the composition of cement pastes made from cements with increased belite and reduced alite contents is their lower calcium hydroxide content. This may affect positively the resistance of such hardened pastes to chemical corrosion. At the same time the depth of carbonation increases with declining C3S content in cement (Kelham and Moir, 1992). 

The phase composition of cement-containing catalysts is described by general equations, based on the reaction between MHC and CaAl204 (CaAl407). 

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