No abstract

No abstract

Abstract. Nanotechnology and nanoscience are rapidly creating new possibilities to control and improve material properties. This trend can be also seen in construction materials used for civil infrastructure applications. Special focus in this area is put on Portland cement and gypsum. Together their annual production is by far larger than for any other material worldwide.Nano-engineering and nano-modification of these materials can be done between their dissolution and hardening. Especially the nucleation step and the crystallization period are most suitable to change the material properties by adding active supramolecular components or colloidal (particle) nano-seeding-additives. This chapter summarizes existing technologies for analyzing and changing the nano-structure of cement and gypsum construction materials. It also shows first results in homogeneous seeding the precipitation of calcium silicate hydrates within a real Portland cement composition. All these procedures, when done correctly, will result in improved material properties opening up with new possibilities for civil infrastructure applications.

all the way from natural biomineralization [1] to industrial applications. [2] Steering the course and outcome of a crystallization process is key to the design and production of materials with specific desired properties. [3] A common concept to influence a crystallizing system is the use of soluble (macro)molecules as additives, which interact with the forming solid phase during its nucleation, growth and further ripening. [4] Obviously, any such effects require the additive to exhibit a reasonably strong affinity to bind to or adsorb on the surface of relevant species such as nucleated nanoparticles or growing crystal facets. This is all the more true for crystallization in multicomponent systems, where the ability to address certain surfaces/phases in a more or less selective manner represents both a major challenge and a long-standing goal. In this context, one prominent case is ordinary Portland cement, which comprises a number of different inorganic phases that simultaneously react with water to yield various hydration products providing the resulting concrete with the desired strength and durability. [3,5] The need for selective crystallization control can readily be illustrated in such systems by a simple example: inThe design of additives showing strong and selective interactions with certain target surfaces is key to crystallization control in applied reactive multicomponent systems. While suitable chemical motifs can be found through semiempirical trial-and-error procedures, bioinspired selection techniques offer a more rationally driven approach and explore a much larger space of possible combinations in a single assay. Here, phage display screening is used to characterize the surfaces of crystalline gypsum, a mineral of broad relevance for construction applications. Based on next-generation sequencing of phages enriched during the screening process, a triplet of amino acids, DYH, is identified as the main driver for adsorption on the mineral substrate. Furthermore, oligopeptides containing this motif prove to exert their influence in a strictly selective manner during the hydration of cement, where the sulfate reaction (initial setting) is strongly retarded while the silicate reaction (final hardening) remains unaffected. In the final step, these desired additive characteristics are successfully translated from the level of peptides to that of scalable synthetic copolymers. The approach described in this work demonstrates how modern biotechnological methods can be leveraged for the systematic development of efficient crystallization additives for materials science.

No abstract