Clinker minerals, 1.25

Sintering 2 to 50 High to very high Up to 100 ton/hr Strongest bonding Ferrous non-ferrous ores, cement clinker, minerals, ceramics... 

Ono, Y. Kawamura, S. and Fujimura, A., "Microscopic Study on the Texture of Clinker Through the Cement Burning and the Development of Clinker Mineral," Journal of Research, Onoda Cement Co., Vol. 16, No. 61, 1964, pp. 73-83. 

Tomita, K. Hayashi, R. and Nagase, T., "Relationship Between Modification of Clinker Mineral such as Alpha-Form Belite and Strength of Cement," Reviews, 24th General Meeting of the Cement Association of Japan, 1970, pp. 15-20. 

Morphology changes taking place during hydration reactions of Portland cement clinker mineral - tricalcium silicate 3 CaO Si02 and various cements were monitored by DSA [35,36]. 

In the course of clinker burning, magnesitrm oxide—originally present in the raw meal constituents—is incorporated irrto the crystalline lattices of the clinker rttinerals formed. In all clinker minerals, distinct but lirrrited amorrrrts of Ca rrray be replaced by Mg ions. In addition, in the ferrite phase some Al may be substituted by Mg in combination with Si" or Tf ions ... 

In the hydration of cement, Mg ions present in the crystalline lattices of clinker minerals are incorporated into the stmcture of the formed hydrate phases. Free MgO, present as periclase, also hydrates, yielding hexagonal magnesium hydroxide [Mg(OH)2], called brucite ... 

Alkali metals are present in clinker preferentially in the form of sulfates. The rest are incorporated into the crystalline lattices of clinker minerals. Sodium tends to be preferentially taken up by the calcium aluminate phase, whereas potassium is mainly incorporated into the crystalline lattice of dicalcium silicate, which becomes stabilized in its form. In either case, in the cotrrse of hydration Na and iorts enter the liquid phase together with the balancing aniorts, which eventrrally become incorporated into the hydration products, being replaced with eqirivalent quantities of OH ions ... 

Kuznetsova et al. (1992) produced activated belite cements by introducing into the raw meal industrial waste products containing phosphoras, chromium, and titaniiun, and by employing cooling rates of up to 5000 K/min, Such clinkers contained dicalcium silicate mainly in its form, but a and a modifications were also present. By adding carbon to the raw mix, regions with local temperatures above 2100 °C were obtained before the bulk of limestone present was decarbonated. This resulted in a non-stoi-chiometry of the produced clinker minerals and along with it an increase of reactivity. 

Cement type Designation Notation Clinker Mineral addition ... 

The Portland clinker used should contain a high amount of tricaldum silicate, preferably more than 45%. This is necessary as the hydration of this phase produces the calcium hydroxide needed for a pozzolanic reaction of the ash. The hydration of the clinker minerals is mainly responsible for the setting and initial strength development of the cement, as the reaction rate of the fly ash is rather slow. The lydration of the ash contributes to strength only at longer hydration times, but also affects other properties of the hardened material. The calcium sulfate added in the form of gypsum or anhydrite serves to control the setting of the fresh paste in a similar way as in plain Portland cement. 

Scharf, H., and Odler, 1. (1992) Intrinsic bond properties of hydrates formed in the hydration of pnre clinker minerals, in Proceedings 9th ICCC, New Delhi, Vol. 4, pp. 265-270. 

The amount of CaO chemically bound within the individual phases of Portland clinker varies significantly, and along with it the amount of CaCOj required to synthesize one weight unit of the particular clinker mineral. The CaO content of pure compounds is as... 

Table 19.1 Heat of hydration of pure clinker minerals.

Table 20.1 Relative rate of expansion of clinker mineral blends in different sulfate solutions (equivalent SO contentFl.2%).

Clinker mineral—a phase constitnting a (Portland) cement clinker. 

Table 5.3 Sequence of formation of clinker minerals (see also Figure 5.2).

Figure 5.9 summarizes the processes that occur during the hydration of anhydrous clinker minerals (left-hand column) to form the products shown in the right-hand column. The rectangular areas occupied by the individual phases correspond approximately to their volumetric proportions in Portland cement. 

Popular models of hydration of clinker minerals can be divided into the delayed nucleation model and the protective layer model. 

During the setting of a cement, a large amount of added water will be used to form hydrate phases such as C-S-H, portlandite, and AFt and AFm phases. Yet, even after complete hydration some free water will remain confined within the porous C-S-H gel and the capillary pore spaces. Notably, this occurs when surplus water is added so that the water/cement (W/C) ratio exceeds 0.6. A lack of water (W/C raho <0.2) results in an incomplete hydration of clinker minerals. The optimum W/C raho for Portland cement, leading to maximum strength, is 0.3 < W/C < 0.5. 

The most widely used cement is Portland cement (OPC). Its principal components, listed in Table 8-1, are calcium silicates (C3S and C2S), calcium aluminates (C3A), calcium-iron aluminates (C4AF) and alkali oxides (Na20, K2O). The composition varies depending on the site and the clinker minerals used to prepare the Portland cement. In order to slow down the rapid reaction of C3A with water, small proportions of gypsum are added. 

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