The stability of Supersulphated Cement (SSC) is investigated at 95°C when subjected to relative humidities of 100, 53 and
11% of water vapour. Previously  investigations at 25, 50, 75°C under the same conditions of humidity reported the stability
of ettringite, one of the initial hydration products. At 95°C, decomposition of ettringite, is found at all humidities and
is rapid at 100% relative humidity. The hydration products of cement pastes at a water cement ratio of 0.27 were determined
by thermogravimetry (TG) and X-ray diffraction (XRD).
The formation of the hydragarnet, plazolite is recorded during the decomposition/dehydration process enhanced by possible
carbonation. Rehydration studies on the products after storage for up to 9 months were carried out using distilled water and
the samples tested for ettringite content. It is concluded that ettringite in SSC is inherently unstable at 95°C.
The stability of supersulphated cement (SSC) is investigated. The hydration products of cement pastes prepared at a water
cement ratio of 0.27 were determined by thermogravimetry (TG) and X-ray diffraction (XRD). Ettringite, one of the initial
hydration products, is shown to be stable under conditions of storage at 25, 50 and 75°C and when subject to relative humidities
of 100, 53 and 11% of water vapour in each case. The effect of drying on ettringite stability at the higher temperatures is
discussed in relation to the relative humidity.
One of the principal uses of supersulfated cement has been for structures exposed to sea water and sulfate bearing ground
waters. The resistance to such environments has been related to the absence of calcium hydroxide and the combination of much
of the free alumina into ettringite during hydration. This paper reports the resistance of SSC to sulfate solutions in which
ettringite has been decomposed. Prism samples were subjected to initial water storage at 25°C for both 28 days and 6 months.
Samples were also cured for 6 months at 95°C and at both 11% and 100% R.H. The control samples of 28 days were compared with
the 6 months samples of a more mature undecomposed SSC paste. After curing the prisms were measured and all the samples were
immersed in three sulfate solutions (0.7M Na2SO4 , 0.7M MgSO4 and saturated CaSO4), and water at the same time. Measurements of linear expansion over 6 months were carried out. Core and surface material
following immersion was examined by DTG and XRD. The study indicated that SSC is resistant to sodium and calcium sulfate solutions.
Strong magnesium sulfate solutions decomposed the samples under all conditions. A possible mechanism for this attack is suggested.