ACTION OF ADMIXTURES ON FONDU CEMENT .2. EFFECT OF LITHIUM-SALTS ON THE ANOMALOUS SETTING TIME OBSERVED FOR TEMPERATURES RANGING FROM 18-DEGREES-C TO 35-DEGREES-C

Measurement of the conductivity of stirred and diluted suspensions of fondu cement hydrated in water at different temperatures indicates tha t the duration of the induction period that occurs before the massive precipitation of hydrates passes through a maximum at 27 degrees C. Th e temperature at which the maximum occurs depends upon the nucleation rates of CAH(10) and AH(3): the CAH(10) nucleation rate is expected to decrease with temperature whereas the AH(3) nucleation rate is expect ed to increase. Thus, one passes from an induction period controlled b y the CAH(10) nucleation rate to an induction period controlled by AH( 3) at the temperature that induces the maximum retardation of the hydr ation. This mechanism explains why lithium salts can reduce or even re move this maximum of retardation.