Effect of temperature on the inhibited and accelerated hydration of calcined gypsum

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Abstract
A study has been made of the effect of initial temperature on the kinetics of the inhibited and accelerated hydration of some samples of calcined gypsum. The inhibitors used were borax, calcium acetate, egg albumin and a commercial organic retarder; the accelerators were sodium sulphate, sodium chloride and precipitated gypsum.Acceleration by salts decreased the induction period by the same amount over the range examined, whereas acceleration by precipitated gypsum decreased the induction period more markedly as the temperature increased. Inhibition by calcium acetate, egg albumin and the commercial organic retarder did not greatly increase the dependence of the induction period on initial temperature. Inhibition by borax rendered the induction period strongly dependent upon initial temperature.The results are discussed in terms of theories already advanced to explain the rate of hydration.