Belitic cement

The results of investigations of the second group of belite cements properties, allowed to choose of the most advantageous compositions, given in Table 9.5. Beside... 

Fig. 9.30 a Effect of the three main phases proportions on the physical properties of cements (according to [132]) 1 rapid hardening cements field, II slightly expansive cements field. III field of expansive cements and cements applied in the self prestiessed concretes production the number correspond to the approximate 3C2S/C4A3S ratio, b Three-components system showing the composition of sulphate-belite cements, (according to [138])... 

Stalk et al. [141-143] studied the possibility of belite cement activity improvement by qnenehing. A great impact of the cooling rate on the strength of mortar was proved, of elinker lime saturation factor below 90% (Fig. 9.31). 

Some Portland cements may contain elevated amounts of belite (C2S), at the expertse of alite (C3S). To produce such clinkers, the lime satiuntion factor of the raw meal must be reduced, typically to values between about LSF=80 and LSF=90, instead of the LSF>90 that exists in ordirrary Portland cement. (Cements made from clinkers with even lower lime saturation factors, which contain no or only very limited amounts of ahte, are called belite cements, and are discussed in section 3.2.)... 

Reactive forms of dicalcium silicate and belite cements 51... 

Belite (or belitic) cements are produced by grinding belitic clinkers with limited amounts of calcium sulfate (gypsum or anhydrite). Such clinkers contain belite (dicalcium silicate) as their sole or main calcium silicate phase. In addition, they contain tricalcium aluminate and the ferritic phase. Alite (tricalcium silicate) may also be present in some belitic clinkers, but only in very limited amounts. They differ both from ordinary Portland clinker and from Portland clinker with an elevated C2S content (see section 2.4) by having a lower CaO content, which results in a lime saturation factor of not more than LSF=80. 

Research on belite cements was spurred by efforts to reduce energy consumption in the manufacture of cement, as clinker of this type may be produced from raw meals with reduced calcium carbonate contents and at a reduced burning temperature. Typically, a reduction of the lime saturation factor from LSF=100 to LSF—80 will reduce the amourrt of CaCOj in the raw meal by about 120 kg per tonne of chnker, which corresporrds to a reduction of the chentical enthalpy of clinker formation by about 220 kJ/t. 

In addition to the C3S/C2S ratio, the compressive strength of belite cements also depends on the Al203/Fc203 ratio in the interstitial phase (Ikabata, 1997), though to a lesser extent. Up to about 28 days the strength of the cement tends to increase with an increasing value of this ratio. 

Belite cements may be used in applications in which high early strength is not essential. They also meet the requirements for cements with low hydration temperature. 

Activated belite (or belitic) cements differ from normal belite cements by the presence of a belite phase whose reactivity has been enhanced by specific measures. The main purpose of such activation is to improve the strength development of the resultant cement, especially at shorter hydration times. 

Another dopant that may be considered for increasing the reactivity of belite cements is S04 ions (Gies and Knofel, 1987 Stark et al, 1987). Under these conditions the final clinker contains the rather than the a -CjS phase, even if high cooling rates have been employed however, the SO -doped form of yff-dicalcium silicate is much more reactive than its SO -free counterpart. The doped C S typically contains about 3% each of SO3 and AI2O3 in its crystalline lattice. If an SO3-doped belitic clinker that also contains some alite is to be produced, the amoimt of SO3 in the raw meal must not exceed... 

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. 

A typical activated belite cement meets the requirements of specifications for ordinary and low-heat Portland cements, and appears to be suitable for appUcations in which moderate early strength development may be acceptable. A white belite cement may be produced by lowering the Fc203 content in the raw meal to near-zero values (Mimtean et al, 1992). 

Chatteijee, A.K. (1996) High belite cements— present status and future technological options Parts I+II. Cement and Concrete Research 26, 1213-1237. 

Ikabata, T., and Takemura, H. (1997) Influence of the composition of interstitial phases on the hydration properties of belite cements, in Proceedings 10th ICCC, Goteborg, paper 2ii007. 

Kurdowski, W., and Wieja, K. (1992) Belite cement with increased browmnillerite (in Polish). Cement-Wapno-Gips 45,45-50. 

Rajczyk, K., and Nocun-WczeUk, W. (1992) Studies of belite cement from barium containing by-products, in Proceedings 9th ICCC, New Delhi, Vol. 2, pp. 250-254. 

Sulfoaluminate-belite cement (SAB) cement in which belite is the main constituent ... 

Sulfoferroaluminate-belite cement (SFAB) cement similar in composition to SAB, but with a significant replacement of A1 by Fe. 

Portland cement Belite cement Sulfobelite cement Sulfoalite cement Phase composition of clinker (%)... 

Jano a, L, and Krajci, L. (1999) An experimental study on the upgrade of sulfoaluminate-belite cement systems by blending with Portland cement. Advances in Cement Research 11, 35-41. 

Palon, M.T., and Majling, J. (1995) Preparation of the high iron sulfoaluminate belite cements from raw mixtures incorporating industrial waste. Ceramics Silikaty (Prague) 39,63-67. 

Sahu, S., and Majling, J. (1994) Preparation of sulfoaluminate belite cement from fly ash. Cement and Concrete Research 24,1065-1072. 

Strigac, J., and Majling, J. (1997) Phase composition development of calcium sulfoaluminate belite cement in the SO atmosphere. World Cement 28,82-86. 

In addition to polyvinyl alcohol/acetate and polyacrylamide, some other polymers have also been employed as the orgarric constituents of MDF cement, including polypropylene glycol (Hsu and Juaang, 1992) and hydroxypropyl-methyl cellulose (Drabik et al., 1992, 1998). As well as Portland and calcium aluminate cements, sulfoaluminate-ferrite-belite cement (in combination with hydroxypropyl-methyl cellulose) has also been employed as constituent of an MDF material (Drabik ei a/., 1992, 1997, 1998). 

Belite-aluminate cement or aluminate-belite cement, also called porsal cement, contains -C2S (belite) and the calcium aluminate phases CA and its main constituents. It... 

Zakharov, L.A. (1974) Alumino-belite cement, in Proceedings 5th ICCC, Moscow, Supplementary paper Section III. 

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