Supersulphated cement

Any attempt to understand the expansive process must thus consider the manner in which the deposition of the products affects the microstructure. The production of ettringite can cause expansion, but does not necessarily do so in a supersulphated cement (Section 9.2.9), much ettringite is formed, but there is no marked expansion. Comparable amounts of ettringite are reported to be formed when ordinary or sulphate-resisting Portland cements... 

In most of the cements described in this section, ettringite is an important hydration product, but, as in supersulphated cements, its formation does not... 

The importance of supersulphated cements decrease during the last fifty years and their production on a large scale was abandoned. In some countries, for example in France, a significant amount of granulated blastfurnace slag with low lime addition is used in road construction [89]. For example in 1974 almost a half of annual blastfurnace slag output was used for this purpose [90]. 

Examples are friction compounds (for brakes), based on phosphogypsum and butadiene rubber [12], sound-proofing panels based on phosphogypsum and mineral wool [13] and wood products modified with phosphogypsum and urea formaldehyde resins [14]. Use in supersulphate cements and as a paper filler has also been considered. There has also been limited use as a soil conditioner. 

Supersulphate cement, normally made from blast furnace slag, portland cement and anhydrite (CaS04), is resistant to seawater attack. Substitution of phosphogypsum for the anhydrite component is, however, reported to render the product unsatisfactory for the latter application [31]. 

Supersulphated cement is obtained from blast-furnace slag (80-85%), calcium sulphate (10-15%) and lime or Portland cement klinker (approximately 5%). After hardening, the strength comparable to that of ordinary Portland cement may be obtained with a considerably lower heat of hydration. Supersulphated cement may be used in various special concrete structures, particularly in situations where the action of acid fluids, sea water and oils should be expected e.g. for foundations and harbour structures. Mixing supersulphated cement with Portland cements and special treatment, such as accelerated hardening, is not possible. 

Bijen J., Niel E., Supersulphated cement from blastfurnace slag and chemical gypsum available in the Netherlands and neighbouring countries, Cem. Cone. Res. 11 (3) (1981) 307-322. 

E. Erdem, H. Olmez, The mechanical properties of supersulphated cement containing phosphogypsum. Cement and Concrete Research, 23 [1] 115-121 (1993). 

Supersulphated cement Supersulphated cement is a mixture of granulated blast furnace slag, calcium sulphate and a small content of activator (Portland cement or lime). It is a low pH material without CH, thus making it a potentially... 

The carbonation of this matrix leads to the decomposition of ettringite into gypsum and CaCOa. It was suggested [124] that the ettringite in this system bonds together the other components of the matrix (CSFI and unreacted slag) and therefore this phase, even when present in small quantities, exerts a considerable influence on the mechanical properties. Various methods have been considered to overcome the carbonation problem in the supersulphated cement GRC, including surface compaction and the application of a protective layer [123]. 

A.J. Majumdar, B. Singh and T.J. Evans, Glass fibre-reinforced supersulphated cement . Composites. 12,1981,177-183. 

B. Singh and A.J. Majumdar, GRC made from supersulphated cement 10 year results . Composites. 18,1987, 329-333. 

A.J. Majumdar and M.S. Stucke, Microstructure of glass fibre reinforced supersulphated cement , Cem. Conor. Res. 11,1981, 781-788. 

---