Application of isothermal and isoperibolic calorimetry to assess the effect of zinc on cement hydration

Possibilities of Use of Isothermal and Isoperibolic Calorimetry to Study the Effect of Zinc on Hydration of Cement Blended with Fly Ash

“…Due to this acceleration the sample with 1 % of ZnCl2 reaches the main hydration peak before the sample with 0.5 % of ZnCl2, contrary to Zn(NO3)2 in which, due to high inhibitory effect in the 1 wt% zinc sample, lower maximum temperature development and therefore slower hydration reactions occur (lower and wider peak). In samples with ZnCl2 lower values of heat flow maxima were observed, which is consistent with the results given in literature for pure cement [13] and for cement with slag [14]. The values of total released heat are similar for both soluble compounds; however for ZnCl2 the differences for various concentrations are very small.…”

“…Isoperibolic calorimetry Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 12 October 2020 doi:10.20944/preprints202010.0233.v1 In samples containing 1 % of zinc in the form of ZnCl2 a noticeable effect on the acceleration of hydration caused by Clions was observed. The acceleration occurred under both, isothermal as well as real conditions, compared to pure cement [13], where this effect was observed only under real conditions during isoperibolic measurement -contrary to data introduced in literature [13], where no peak was found on the calorimetry curve for 1 wt % of zinc in the mixture, probably due to a low temperature in a calorimeter (25 °C). This effect was observed in pure cement, but not in samples with slag [14].…”

“…While the reactivity at lower temperature in isothermal calorimeter is lower also lower heat evolution occurs, which is due to the substitution of In samples with zinc concentration of 0.05 and 0.1 wt. % a small sulfate depletion peak was recorded on the hydration curve together with the main hydration peak [22] same as in reference samples in literature [13,14]. As the zinc content rises, the first peak rises too and the second peak decreases up to the zinc concentration of 0. it can be assumed that zinc does not significantly affect total evolved heat.…”

“…Due to exactly defined conditions this method can be used for long lasting measurements. By the change of temperature the reaction rate can be changed and hence particular reactions can be studied in more detail, especialy during early stage of hydration where the heat rate is relatively high [13].…”

“…Šiler et al [13] dealt with the effect of zinc in the form of ZnO, Zn(NO3)2 and ZnCl2 on cement pastes and in [14] they doped cement with slag in the same experiments. They discovered that ZnO is the strongest retarder due to low solubility.…”