Regularities of adsorption of the polymethylene naphthalene sulfonates individual fractions on cement hydrates and some mineral phases

Abstract

This paper studied the regularities of monomeric and individual oligomeric polymethylene naphthalene sulfonate fraction (n=2-10) adsorption on hydrated cements (PC 500-D0-N and CEM II/A-S 42.5 N) and hydrolytically stable phases (very fine ground calcium carbonate and simulated CSH-phase) by HPLC. It was revealed, that the rate and the extent of oligomeric substances adsorption are significantly lower compared that on Portland cement hydrates. The regular adsorption increase on calcium carbonate was noticeable with PNS polycondensation degrees growth.

It was shown that PNS sorption on hydratable phases arise not only by electrostatic interaction with active positive sites on hydrates surface (calcium cations predominantly), but by intercalation also. As a consequence, in the early stage (up to 30 min) adsorption degree of monomer components (salts of naphthalene mono- and disulfonic acid) on ground calcium carbonate is very low (0-2.4%) compared to hydrated Portland cements (1-6%). While increasing adsorption duration or decreasing in two and more times superplasticizer dosage (in other words, when active components were adsorbed almost completely and competitive sorption disappears) adsorption degree of monomer components begin to rise. The same conclusions were drown from the analysis of data for adsorption on CSH-phase. Onwards tetramer, PNS adsorption kinetic on high active sorbents (hydrated Portland cements, CSH-phases) scarcely depends on molecular mass. PNS dimer adsorption behavior falls in between monomers and oligomers of higher molecular mass. The research confirmed the reliability and informativity of HPLC in the studying of the regularities of monomeric and oligomeric PNS components sorption on cement hydrates and other mineral phases.