High molecular weight anionic polymers have been incorporated into the calcium silicate hydrate (C-S-H) structure during precipitation of quasicrystalline C-S-H from aqueous solution. The anionic polymers studied were poly(methacrylic acid), poly(acrylic acid), and the sodium salt of poly(vinyl sulfonic acid). Expansion of the interlayer spacing coupled with high-carbon contents confirmed that the polymers intercalated between the layers. D-gluconic acid behaves similarly. Intercalation characteristics strongly depended on both the type of polymer and Ca/Si molar ratio of C-S-H; intercalation reached a maximum at an initial Ca/Si ‫ס‬ 1.3 in all cases. Poly(vinyl alcohol) was the only nonionic polymer among those studied that was incorporated into C-S-H. Evidence for interlayer intercalation is less definite. The C-S-H/polymer complexes were examined by Fourier transform infrared spectroscopy, 29 Si nuclear magnetic resonance magic angle spinning, and 13 C cross-polarization, magic angle spinning nuclear magnetic resonance spectroscopy.

Polyelectrolyte species, known as superplasticizers, dramatically affect the rheological properties of dense cement suspensions. We have studied the influence of sulfonated naphthalene formaldehyde condensate (SNF) and carboxylated acrylic ester (CAE) grafted copolymers of varying molecular architecture on the surface (e.g., adsorption behavior and zeta potential) and rheological properties of concentrated cement suspensions of white portland cement and two model compounds, ␤-Ca 2 SiO 4 and ␥-Ca 2 SiO 4 . The adsorption of SNF species was strongly dependent on cement chemistry, whereas CAE species exhibited little sensitivity. The respective critical concentrations (⌽*) in suspension required to promote the transition from strongly shear thinning to Newtonian flow (flocculated 3 stable) behavior were determined from stress viscometry and yield stress measurements. Theoretical analysis of interparticle interactions suggested that only colloidal particles in the size range of <1 m are fully stabilized by adsorbed polyelectrolyte species. Our observations provide guidelines for tailoring the molecular architecture and functionality of superplasticizers for optimal performance.

C-S-H samples were precipitated from aqueous solution containing Ca(NO3)2 and Na2SiO3 with an initial Ca/Si molar ratio of 1·3, when the pH value in the solution was varied by adding HNO3 or NaOH. A pH > 10·9 was required to obtain quasi-crystalline C-S-H, and the CaO/SiO2 ratio of the precipitate was increased with increasing pH, reaching a maximum close to the initial ratio at pH > 13. C-S-H was also precipitated with varying initial Ca/Si molar ratios at pH > 13. It was shown that the CaO/SiO2 ratios can be controlled by either varying the pH value at given initial Ca/Si ratios, or by varying the initial Ca/Si ratios at pH > 13. The C-S-H samples were investigated using X-ray diffraction and 29Si nuclear magnetic resonance spectroscopy, which identifies the connectivity of silica tetrahedra (Qx). The interlayer spacing decreased linearly, and Q1/(Q1 + Q2 + Q3) ratios increased with increasing CaO/SiO2 ratios. A good correlation between Q1/(Q1 + Q2 + Q3) ratios and interlayer spacing was observed.

Some high molecular weight cationic polymers, poly(diallyldimethylammonium chloride) (PDC) and poly(4-vinylbenzyltrimethylammonium chloride) (PVC), have been incorporated into the calcium silicate hydrate (C-S-H) structure during precipitation of quasicrystalline C-S-H from aqueous solution. Expansion of the interlayer spacing [0.9 nm (PDC), 1.5 nm (PVC)] and a high-carbon content provided evidence that these polymers were intercalated between layers of C-S-H when Ca/Si <1.0. Intercalation characteristic properties strongly depended on both of the type of polymer and Ca/Si ratio in C-S-H. Poly(4-vinyl-1-methylpyridinium bromide) and methyl glycol chitosan (iodide) also interacted with C-S-H, probably by surface adsorption. The C-S-H/polymer complexes were examined by Fourier transform infrared spectroscopy, 29 Si nuclear magnetic resonance magic angle spinning, and 13 C cross-polarization, magic angle spinning nuclear magnetic resonance spectroscopy. Mechanisms of intercalation of different kinds of polymers between the C-S-H layers are discussed.

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