Influence of cellulose ether on hydration and carbonation kinetics of mortars

• The delaying effect of CE was found to be proportional to its contents in mortar.
• The proportion of CE does not affect the time required for the total carbonation.
• The increase of the CE proportion results in slowing down the carbonation kinetics.
• The carbonation of mortar with CE modifies the microstructure and the pores size.

The hydration process of Portland cement and retarding effect of cellulose ether (CE) on hydration and carbonation were studied. The degree of CE-substitution is a major parameter which plays an important role in terms of retardation of both hydration and carbonation. For the hydration process, this CE-effect was highlighted through the results of an experimental campaign based on thermogravimetric analysis (TGA) performed on mortar samples conserved in an ambient air in which the atmospheric CO2 was absorbed by whitewash solution. This type of conservation is chosen in order to make precise the measurement of dehydration rate by TGA tests. While for the carbonation mechanism, the CE-effect was identified by the measurement of carbonation depth with phenolphthalein spraying.This paper aims to determinate a coefficient of retardation of hydration according to the CE-rate used in the manufacturing of mortars. This coefficient may be taken into account in the calculation of the reaction rate of anhydrous constituents of cement in order to determine a precise hydration degree of mortars. Consequently, this delay in cement hydration delays the carbonation processes because of the lack of hydrates to react with CO2.