Abstract
In order to know the reaction between cement and naphthalenesulfonate type superplasticizer (NSNa) quantitatively, Ca(OH)2 and ethyl silicate or aluminum isopropoxide were reacted in the presence of NSH (sulfonic acid form of NSNa). The hydrates obtained were investigated by chemical analysis, XRD and SEM. The effect of the addition of hydrates containing NS on the drying shrinkage of cement mortar was also measured. The results obtained were as follows.
(1) NS reacted with silicate and Ca(OH)2. The mole ratio of NS:Ca:Si in the hydrates depended on the mole ratio of Ca/Si in the initial composition.
(2) NS also reacted with aluminate and Ca(OH)2. Calcium aluminate hydrates containing NS formed at the mole ratio of approximately NS:Ca:Al=2:2:1 in the absence of gypsum. Ettringite mainly formed in the presence of gypsum.
(3) Hydrates containing NS consisted of fine particles (approximately 0.2μm). The addition of hydrates containing NS to cement mortar, in which NS content was kept in a normal dosage, did not influence much on the drying shrinkage of mortar.
The hydration of calcium silicate or calcium aluminate under the presence of NS was explained on the basis of the reaction between polyelectrolyte and polybasic acids under the presence of Ca(OH)2.
