Zeta potential, rheology and nature of the sorbent phases

4 Zeta potential, rheology and nature of the sorbent phases 

Ernsberger and France (E7) showed that addition of calcium lignosulpho-nate causes cement grains to develop a negative -potential. Daimon and 

and thus to place more of its negative charges into the diffuse double layer. 

The fact tliat both conventional water reducers and superplasticizers are more efTective if added some time after mixing provides a strong indication that adsorption probably occurs at least in part on the hydrated phases, as the anhydrous surfaces have by that time become covered with hydration products. Chiocehio cl al. (C57) found that the optimum time for addition was at the start of the induction period. More of the admixture seems to be taken up by the early hydration products, especially of the aluminate phase, if it is added before the early reaction has subsided. 

Costa cl al. (C58) showed that superplasticizers increase the fluidity of C,S pastes much as they do that of cement pastes. Studies on individual anhydrous and hydrated compounds in aqueous and non-aqueous media indicate that calcium lignosulphonate and superplasticizers are adsorbed by C -S-H, AFm phases or CH but not by C,S, C,A or C,AH (R54, R55,R56,C58,M 105), though they appear to be taken up by unhydrated P-CiS (C59). The admixtures also enter interlayer sites of C4AF1. and perhaps also of C -S--H (R55). Intercalation of organic molecules in C4AH, is a well-established effect (Section 6.1.1), 

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