CHEMICAL AND PHYSICAL EFFECTS OF SODIUM LIGNOSULFONATE SUPERPLASTICIZER ON THE HYDRATION OF PORTLAND-CEMENT AND SOLIDIFICATION STABILIZATION CONSEQUENCES

The effects of sodium lignosulfonate superplasticizer on the hydration of Portland cement Type V have been investigated by XRD and FTIR tech niques. The results of these studies indicate that the superplasticize r inhibits the hydration reaction as demonstrated by the reduced forma tion of Ca(OH)(2) as well as a lower degree of polymerization of the s ilicate anions. The hydration reaction seems to be controlled by dispe rsions of various charges present in hyperalkaline solution in cement paste. The mechanism of inhibition is discussed and a 'Charge Disperse d Tri-layer Model' is proposed to explain the observed effects on the hydration reactions. According to this charge dispersal model, the Ca2 + ions from initial hydration reactions go into the solution to form a tightly-bound bi-layer of counterions with the negatively charged cal cium-silica-hydrate surface. Consequent to this intrinsic process, a t ri-layer consisting of superplasticizer anions is immediately formed w hich inhibits further reactions. Possible consequences of the presence of superplasticizer on the solidification/stabilization of inorganic and organic pollutants by cementitious materials have also been discus sed.