Effect of superplasticisers on adsorption, rate of cement hydration, and pore structure of cement pastes

This paper presents an experimental study on the effect of three superplasticisers, polycarboxylate (PCE), naphthalene (SNF) and a newly developed modified lignosulphonate (PLS), on admixture adsorption, rate of cement hydration, and pore structure of cement pastes. The mixtures were designed to achieve similar workability at w/c ratios of 0·34 and 0·40, thus both type and dosage of the admixtures had influence on various properties. The results indicate that the adsorption was strongly dependent on the type of superplasticiser used in the cement paste. The superplasticisers delayed cement hydration at early age, but did not have significant effect on the cement hydration from 7 to 91 days. The retardation of the pastes was in the order of SNF ≤ssthan PCE ≤ssthan PLS. These superplasticisers also had influence on the total porosity and pore size distribution of the cement pastes which would have potential influence on permeability of concrete.