Oriented aggregation of calcium silicate hydrate platelets by the use of comb-like copolymers

Abstract

We present an in-depth study of the formation of stable suspensions of low density aggregates of calcium silicate hydrate (C–S–H) particles stabilized by comb-like copolymers. These suspensions exhibit fundamentally interesting properties such as gel formation at 1.4 vol% of particles. Furthermore, they constitute a novel class of hardening accelerators for cementitious systems. Stabilization of C–S–H particles by polyelectrolytes is essential for the synthesis of stable and active C–S–H suspensions. Comb-polymers consisting of charged monomers (acrylic acid or 2-(phosphonooxy)-ethyl-methacrylate) and poly(ethylene glycol) monomers direct C–S–H particle aggregation into fractal structures. The fractal nature of the aggregates has been characterized by TEM and SAXS. Based upon (U)SAXS data of different C–S–H suspensions, it is demonstrated that two-dimensional initial C–S–H particle aggregation favours the creation of structures with a high specific surface area which are particularly active as cement hardening accelerators.