Tailoring cementitious materials with genetically, engineered microbial exopolysaccharides, a biologically inspired approach towards high-performance construction materials

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Biomineralizing organisms exert vast control on their inorganic components by secerning evolutionary optimized biopolymers during mineral formation. This often leads to multifunctional materials, some of which show superior combinations of technically relevant properties, such as a concomitant high hardness and toughness, while employing “inexpensive” bulk materials (CaCO3, apatite or silica). Although in the past, the potential technological link between (load-bearing) biominerals (e.g. bone, teeth, shells) and high-performance construction materials had been realized by numerous investigators, the knowledge transfer gleaned from biological mineralization principles into the scientific field of cementitious construction materials as yet has remained elusive. The reasons for this failure are manyfold, ranging from the problem of cost pressure, which is immanent to construction materials, to the incomplete mechanistic understanding of mineralisation processes under biological control as well as the complex mineralogy and setting behaviour of cementitious materials (i.e. concrete).This proposal aims at bridging the gap between the two scientific disciplines. In a collaborative effort we propose to study the formation of hybrid materials that are composed of polysaccharides and major mineral phases that constitute components of cement mixtures. Microbial exopolysaccharides are being produced in suspension cell cultures, which represents a cost-efficient means to produce complex biopolymers that can be genetically tailored in terms of molecular weight distribution, branching degree and charge density. The interactions of these polymers with inorganic phases relevant to construction materials (calcium carbonate, sulphate, and calcium aluminate hydrate) shall be explored with the focus laid upon the polymers’ influence exerted on the particular polymorph, individual crystal morphology and the texture of polycrystalline materials. For the latter hybrid materials, mechanical tests should serve as benchmark for deriving construction materials that show improved mechanical properties. As a long-term perspective, this biologically inspired approach might pave the way towards economic light-construction materials that will dispense with steel reinforcements.