Calcium sulfoaluminate

ASTM C845 Type E-I (K) expansive cement manufactured ia the United States usually depends on aluminate and sulfate phases that result ia more ettriagite formation duriag hydration than ia normal Portland cements. Type K contains an anhydrous calcium sulfoaluminate, C A SI. This cement can be made either by iategraHy burning to produce the desired phase composition, or by intergrinding a special component with ordinary Portland cement clinkers and calcium sulfate. 

The most widely used single component, calcium sulfoaluminate admixture, is composed of 30% C4A3S, 50%... 

Anhydrous calcium sulfoaluminate is formed by calcination of lime, gypsum and bauxite. The active expansive ingredient, C4A3S is formed by solid-state reaction from mixtures of compounds composed of calcium oxide,... 

The most widely used single component, calcium sulfoaluminate admixture, is composed of 30% CAS, 50% CaSO and 20% CaO with small amounts of glassy phase. Particle s3ize is coarser than that of Portland cement. Larger particle size ensures that the potential expansion due to hydration is extended over a period of time. Chemical and physical properties of the most widely used proprietary product, Denka CSA, are given in Table 6.10 [74], Other CSAs include mixtures of C ASH and 2 CS (monosulfate and gypsum) and mixtures of Type I cement, liigh-aiumina cement, CaSO, 2H O, Ca(OH) and CaO [75], 4 2... 

Anhy2drous calcium sulfoaluminate is formed by calcination of lime, gypsum and bauxite. The active expansive ingredient, C A S is formed by solid-state reaction from mixtures of compounds composed of calcium oxide, aluminum oxide, sulfur trioxide gas formed during the calcination of gypsum, and bauxite. Crystal growth of CSAs is encouraged to proceed at a slow rate to preserve the potential force of expansion for extended periods [76],... 

Mehta, P.K. Effect of Lime on Hydration of Pastes Containing Gypsum and Calcium Alu-minates or Calcium Sulfoaluminate. J. Am. Ceram. Soc. 56, 315 (1973). (published by John Wiley Sons Ltd, reproduced with the permission of Wiley Sons)... 

Two temaiy compounds exist in the system C-S-A-S calcium sulfoaluminate and calcium sulfosilicate. 

Tetracaldum trialuminate sulfate (calcium sulfoaluminate, C4A3S) is the phase that is mainly responsible for the early strength development of the cement. For best performance the C4A3S content in non-expansive suhbbehte cements should he between 30% and 40% (Beietka et al, 1996). In the presence of iron oxide in the raw meal, a small amount of this oxide may enter into solid soluhon with the sulfoaluminate phase,... 

Calcium sulfoaluminate modified Portland cements may be produced by combining ordinary Portland clinker with limited amoimts of calcium sulfoaluminate, produced separately (see section 21.3), and calcium sulfate. 

Lau, W., and Glasser, F.P. (1996) Hydration of calcium sulfoaluminate cements. Advances in Cement Research 8, 127-134. 

Mudbhatkal, G.A. et al. (1986) Non-alitic cement from calcium sulfoaluminate clinker— optimization for high strength and low temperature applications, in Proceedings 8th ICCC, Rio de Janeiro, Vol. 4, pp. 364-370. 

Park, C.-K. et al. (1997) Microstructural changes of calcium sulfoaluminate cement paste due to temperature, in Proceedings 10th ICCC, Goteborg, paper 41v068. 

Sharp, J.H., Lawrence, C.D., and Yang, R. (1999) Calcium sulfoaluminate cements — low-energy cements, special cements or what. Advances in Cement Research 11,3-13. 

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

Type K expansive cement is the expansive cement used worldwide in the largest amounts. It contains calcium sulfoaluminate (C4A3S) in combination with calcium sulfate as the expansive component and Portland clinker as the component producing the cementitious matrix. The expansive component is burnt separately in the form of a calcium sulfoaluminate clinker, which is subsequently interground with Portland clinker and additional calcium sulfate in the form of gypsum or anhydrite. Alternatively, the sulfoaluminate clinker may be ground separately and added to Portland cement in amounts that may vary depending in the intended use of the final expansive cement. 

---