Effects of molecular structure of polycarboxylate-type superplasticizer on the hydration properties of C₃S

Abstract

Effects of polycarboxylate-type superplasticizer (PC) molecular structure on the hydration heat of tricalcium silicate (C₃S) paste and polymerization degree of hydration products (C-S-H gel) were researched by using TAM AIR isothermal microcalorimetry (TA) and ²⁹Si nuclear magnetic resonance (NMR). Methoxy polyethylene glycol-methacrylates-based polycarboxylate superplasticizers with different side chain lengths and main chain lengths were employed. PC molecules with shorter main chain or longer side chains caused stronger retardation of C₃S early hydration and lesser increase of C₃S 3 d hydration degree. NMR measurement indicated that the incorporation of PC increased the hydration degree of C₃S paste and the polymerization degree of silicon-oxygen tetrahedron of C-S-H gel. The tendency for C₃S 7 d hydration degree to improve was more pronounced while PC molecules with longer main chain or shorter side chain were added. Whereas, PC molecules with longer main chains or longer side chains increased the 7 d polymerization degree of C-S-H gel.

Keywords

tricalcium silicate / polycarboxylate superplasticizer / C-S-H gel / hydration / NMR

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