Alinite Cements

Locher (LSI) reviewed ways of decreasing the energy consumption in cement manufacture to values substantially below those characteristic of modern Portland cement production. They included the use of fluxes to lower the burning temperature, the production of cements containing more reactive forms of belite or based on belite together with highly reactive phases, replacement of alite by the chloride-containing phase, alinite, and the use of composite cements. 

The hydration reactions of alinite cements do not appear to have been reported, but it may be surmised that they are similar to those of Portland cements, with the probable addition to the products of CjA CaCK-lOHjO and possibly also of Ca2Cl2(0H)2 H20. The Cl is, however, not wholly and permanently combined in these or other hydration products. In tests on reinforced concrete, serious corrosion had occurred within 5 years, showing the cement to be unsuitable for such use (L51). 

Disposal of the solid residues from the treatment of waste gases is an issue that needs to be addressed, particularly when they contain heavy metals and toxic organic compounds. One possibility is to convert the residues into an alinite cement, composed mainly of calcium silicates and calcium chloride [29.14]. When set, the concrete effectively locks up the toxic components (see also section 28.4.6). 

R. Oberste-Padtberg et al., Alinite cement, a Hydraulic Binder Made from Refuse Incineration Residues , Zement Kalk Gips 9,1992, 451-455 (English 11,1992, E278-E290). 

The production of alinite clinker, which has the properties of rapid hardening cement, due to high hydraulic activity of alinite, is, however, linked with two problems. The first one is the HCl emission from the rotary kiln HCl is formed in reaction of chlorine with water vapour, contained in the kiln gases. Nudelman [154] proposed the closed chlorine cycle with the calcittm chloride recovery, in reaction between HCl and CaCOj. However, it wottld complicate seriously the functioning of kiln installation. Another problem relates to the very high chlorine content in alinite clinker and consequently in cement, which will cause the corrosion of reinforcement in concrete. These questions are discussed in Chap. 6. However, the alinite cement can be applied in special cases, in the concreting works at lowered temperature, principally in permafrost area. 

Alinite is a caldum oxy-chloro-aluminosilicate that is related to alite, the main constituent of Portland cement. Whereas in ahte (tricalcium silicate) Ca cations are balanced by SiO " and 0 anions, the stmcture of alinite consists of Ca (and Mg ) cations balanced by AlO ", 0 , and Cr anions. Crystallographic studies have... 

Another sihcate phase containing chlorine that may also be present in alinite cements in limited amormts is calcium chloride orthosilicate, Ca3Si04Cl2 (Agarwal et al, 1986 Miskiewicz and Pyzalski, 1988). 

Alinite cement was developed in the former Soviet Union, and was patented by Noudelman in 1977. It is characterized by the presence of the alinite phase in chnker... 

Table 6.2 gives the chemical composition of alinite clinker/cement as published by different investigators. The key parameter in raw meal design of alinite cement is the... 

Table 6.2 Chemical composition of alinite cement as published by various investigators (in wt. %).

To produce alinite cement, the clinker does not need to be interground with calcium sulfate to control setting however, both the short-term and long-term strengths increase with increasing additions of gypsum (Pradip and Kapur, 1990). 

Alinite cement exhibits a fast initial hydration, which exceeds that of Portland cement. Table 6.3 summarizes the progress of hydration of this cement and its main constituents. The hydration is associated with a distinct heat evolution, with peaks immediately after mixing and after about 6 hours (Ji et al, 1997). The products of hydration are (Ji et al., 1997) ... 

The alkalinity of the pore solution in hardened alinite cement pastes lies at around pH=ll (Kostogloudis et al, 1998), and thus is distinctly lower than that common in ordinary Portland cement pastes (pH 12.5-13.5). 

Data on the corrosion of steel reinforcement embedded in concrete made from alinite cement are not uniform. In most investi tions an intensified corrosion of steel was observed under such conditions however, in a recently published study (Kostogloudis et al, 1998) no significant corrosion was observed in test specimens that were stored continuously or in interrapted fashion under water for up to 12 months. 

The use of alinite cement in steel-reinforced constmctions must be discouraged because of possible corrosion of the reinforcement. The cement may serve well in applications in which reinforcement is not used. 

Because of their distinct chlorine content, most but not all ecocements may be considered special forms of alinite cement Their typical chemical composition lies in the following range (Moriya et al, 1996 Tsuchida et al 1996 Uchikawa and Obana, 1996 Takumae/a/., 1997) ... 

Ftikos, Ch., and Kiatos, D. (1994) The effect of chlorides on the formation of belite and alinite phase. Cement and Concrete Research 24,49-54. 

Ftikos, Ch., Georgiades, A., and Philipou, Th. (1991) Preparation and hydration study of alinite cement. Cement and Concrete Research 21, 1129-1136. 

Ftikos, Ch., Philippou, Th., and Marinos, J. (1993) A study of the effect of some factors influencing alinite clinker formation. Cement and Concrete Research 23,1268-1272. 

Ji, L., Ren, X., and Sn, H. (1997) Effect of chloride on hydration properties of alinite cement, in Proceedings 10th ICCC, Goteborg, paper 2ii030. 

Kostogloudis, G.C. et al. (1998) Comparative investigation of corrosion resistance of steel reinforcement of alinite and Portland cement mortars. Cement and Concrete Research 28,995-1010. 

Kurdowski, W, and Moric, U. (1989) Once more about bromine alinite. Cement and Concrete Research, 19,657-661. 

Neubauer, J., and Pollmann, H. (1994) Alinite—chemical composition, solid solution and hydration behaviom. Cement and Concrete Research 24,1413-1422. 

Oberste-Parberg R. et al (1992) Alinite cement a hydraulic binder made from refuse... 

Pradip, A., and Kapm, P.C. (1990) Production and properties of alinite cements from steel plant waste. Cement and Concrete Research 20,15-24... 

Yoshiaki et al. (1996) Hydration characteristics of alinite rich clinker burnt at different temperatures (in Japanese). Journal of Research of the Chichibu Onoda Cement Corporation 47,62-72. 

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