1979 Volume 87 Issue 1006 Pages 301-307
The influence of sodium aliphatic carboxylic acids, having different hydrophobic chains, on the hydration of alite and portland cement was studied by means of conduction calorimeter (see Fig. 3, Table 3). And the wettabillty of cement with sodium carboxylic acid was discussed by means of the rate of capillary rise (see Fig. 4, 5). Amount of compound adsorbed on cement was determined by Total Organic Carbon analyser (see Table 5).
Sodium aliphatic carboxylic acids consisting of long hydrophobic chains slightly retarded the very early stage of hydration (see Fig. 3) but the hydration of alite or the main hydration of cement was less affected as compared with sodium aromatic sulfonate addition (see Table 3).
The hydrophilic properties of -COONa and -SO3Na were different each other. -COONa was less hydrophilic than -SO3Na. Sodium aliphatic carboxylic acids having long hydrophobic chains formed insoluble calcium salts. The very early hydration of cement was retarded and the wettability of cement decreased due to the precipitation of these calcium salts on cement particle (see Fig. 5). But as the time proceeded, these precipitates separated out from cement to form scum. Therefore, sodium carboxylic acids having long hydrophobic chains unappreciably retarded t1.
Consequently, the balance between hydrophobic and hydrophilic properties plays an important role in the retarding mechanism by organic compounds.
