Calcium lignosulfonate effect

Fig. 1.16 Effect of hydration time on the adsorption of calcium lignosulfonate on C3A hydrates (Rossington).

Table 1.10 Effect of calcium lignosulfonate on C3A reaction (after Chatterji)... 

Commercially available calcium lignosulfonate can be readily and effectively grafted with methyl acrylate, methyl methacry-... 

Oil-Well Cement Retarders. Sodium and calcium lignosulfonates are the most commonly used retarders for oil-well cements (98). They are effective with all Portland cements and are generally added in concentrations from 0.1 to 2%. Depending on their structure and purity and on the nature of the cement, they... 

Ramachandran, V. S., and Feldman, R. F., Effect of Calcium Lignosulfonate on the Tricalcium Aluminate and Its Hydration Products, Mater. Const, 5 67-76(1972)... 

The data presented in this section illustrate that, with the exception of those accelerating water-reducing admixtures containing calcium chloride, there is an abundance of evidence to support the conclusion that water-reducing admixtures of lignosulfonate chemical form certainly will not accelerate any kind of corrosion with reinforcement and, when used to reduce the water-cement ratio, will form a more permeable and durable protective cover for the reinforcement. In view of the chemical nature of the other types of materials such as the hydroxycarboxylic acids and hydroxylated polymers, it seems most likely that these materials too would have no deleterious effect in this respect. 

The addition of an alkali carbonate+lignosulfonate combination to ordinary Portland cement containing calcium srrlfate also causes a liquefying effect. This effect is greater than that of the lignosulfate alone, yet less pronoimced than that existing in sitUate-free cements (Odler et al., 1978 Skvara, 1996). Under these condition an initial liquefaction is followed by a rapid increase of paste viscosity. 

Ramachandran and LoweryP l applied conduction calorimetry to the study of the relative effects of various retarders on the hydration of cement. The retarders used were calcium gluconate, glucose, glycolic acid, molasses, sodium borate, sodium citrate, sodium heptonate, sodium hexametaphosphate, sodium pyrophosphate, sugar-free lignosulfonate, and sucrose. The dosage of the chemicals varied between 0.025 and 1.2%. 

The relative effects of superplasticizers on the hydration of C3S has been compared in the presence of 1% SMF, 1% SNF, and 0.25% LS (lignosulfonate). The rate of hydration was determined by TG technique (Fig. The amount of calcium hydroxide formed in pastes with these admixtures was distinctly lower than those in reference samples, indicating significant retardation effects. It was also found that the C-S-H formed in the presence of the admixtures had a higher C/S ratio. It is evident from the figure that the retardation effect of even 0.25% LS is significant. 

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