engleski

Hydration study of ordinary Portland cement in the presence of lead(II) oxide

The aim of this work is to investigate the effect of the addition of lead(II) oxide on hydration heat and specific conductivity of a CEM I Portland cement. The measurements were made at 20 oC, defined water/solid ratio, W/S = 0.5 and different contents of lead(II) oxide (0 – 1 wt. %). The heats production during hydration were determined by differential microcalorimetry up to 48 hours of hydration and the specific conductivity by a digital conductometer. Thermal gravimetric analysis (TGA) was employed in the characterization of the cement structure. The hydration heat results show that the addition of lead(II) oxide affect the cement hydration kinetics. Kinetic curves show that higher content of lead(II) oxide slow down the hydration processes and the heat values are lower. Addition of lead(II) oxide significantly delays the time appearance of the maximum conductivity. Setting time is prescribed by standard for a particular type of cement and can be determined based on the appearance of specific conductivity maximum, which occurs at the setting time. Acceptable share of lead(II) oxide is the one at which time the appearance of the conductivity maximum permitted standard limits. It was found that the acceptable amount of lead (II) oxide in cement system is w = 0.25 wt. %.

stabilization/solidification (S/S); hydration heat; specific conductivity; differential microcalorimetry; thermogravimetric analysis (TGA)

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