Characterization of the nanoparticles formed in aqueous phase of hydrating cement pastes in the presence of PCEs

Two PCEs with varied charge density and one sulfonated polyacrylic acid linear copolymer (PAS) were synthesized for investigation of their influences on aqueous phase of fresh cement pastes (fcps) during early hydration. Aqueous phase was extracted by ordinary centrifugation (11,000 gravity) and subsequent ultracentrifugation (186,000 gravity) to remove the suspending particles. Inductively coupled plasma-optical emission spectrometry (ICP-OES) and total organic carbon (TOC) methods were employed to quantify polymer and elemental concentrations. It is found that the presence of polymers in fcps leads to massive formation of particles with sizes of 200-300 nm dispersed in aqueous, being composed of mainly ettringite and a few C-S-H and polymers. Retardation effect of the polymers on cement hydration and the amount of the formed particles are in order of PCE1 < PCE2 < PAS, the same as the order of their charge density. These findings are important for understanding of retardation mechanism of PCEs and rheological regulation of fcps.