Influence of Polymers on Nucleation and Assembly of Calcium Silicate Hydrates

Abstract

Calcium silicate hydrates (C-S-H), the main components of hydrated cement, are known for being responsible of its cohesion. In this respect, they act as "glue" for the other solid components of mortar or concrete and thus strongly influence the mechanical properties of the outcoming material. One major disadvantage of cementitious materials though are their poor tensile strengths which can lead to crack formation. Inspired by Nature, which demonstrates in a huge variety of different biomaterials like bone or nacre the highly advantageous implementation of soft organics into brittle minerals to overcome this drawback, we provide here a route for the formation of inorganic-organic mesocrystalline C-S-H.Given the scarce knowledge about the formation mechanisms and the influence of polymers on the growth and nucleation of C-S-H, a first part of this work focuses on the investigation of ongoing processes in the pre- and postnucleation stage of C-S-H precipitation and how these processes can be tuned by polymers. Although a huge panoply of additives were tested and proven to alter the nucleation outcome of C-S-H at various conditions, a phage display assay was performed to identify highly selective binding motifs on C-S-H to get closer to perfectly structured additives for C-S-H adsorption. With proper co-polymers that mimic the desired features that were proposed from the phage display, colloidal stabilization of C-S-H in solution could be achieved. Subsequent destabilization resulted in the formation of ordered inorganic-organic hybrid superstructures in three dimensions. Regarding mechanical properties, these so-called mesocrystals were proven to exhibit much more flexibility than pure C-S-H which is highly desired in construction materials. Thus, the outcome of this work can be seen as a first step towards the formation of new construction hybrid materials using bio-inspired approaches.