engleski

Stabilization of chromium salt in ordinary portland cement

Ordinary Portland cement (OPC) samples containing the chromium salt have been investigated using differential microcalorimetry, conductometry and Fourier transform infrared spectroscopic analysis. The effect of chromium on OPC hydration was evaluated by continuous observing of early hydration. The microcalorimetrical results show that with increasing the share of chromium salt, heat maximums assume lower values and the occurrence of the maximum registered in the earlier hydration times. Conductometrical measurements show that with increasing addition of chromium salt, curve no longer has a specific shape, specific conductivity immediately drop and the maximum is reached earlier. This coincides with microcalorimetrical results. It can be concluded that the addition of chromium does not affect the mechanism of the hydration process, but it does affect the kinetic parameters and dynamics of the cement hydration process. It was found that chromium salt addition to the cement-water system is acceptable up to 2 wt. %. According to standard EN 196-3 for OPC, the beginning of binding time should occur after 60 minutes. Increased amount of chromium over 2 wt. % significantly accelerate the beginning of binding time and for the system is not acceptable.

stabilization/solidification; ordinary portland cement; ammonium dichromate; differential microcalorimetry; conductometry; Fourier transform infrared spectroscopy

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