Periodic Reporting for period 2 - Biocrete (Biocrete – Bio-inspired bacteria-based stress-responsive concrete.)
Okres sprawozdawczy: 2019-11-01 do 2020-10-31
Concrete is the construction material of choice. Deterioration of concrete infrastructure, however, represents a huge societal burden. Bacteria-based self-healing concrete offers a promising solution to this problem; even so, the calcium carbonate healing material formed by this technology is weak and brittle, making the concrete susceptible to further damage. The Biocrete project aims to develop a biologically inspired bacteria-based stress-responsive concrete. The project cross-pollinates knowledge and competences of bio-inspired materials synthesis and cementitious materials technology; via the partnering of groups at the Delft University of Technology (TUD), The Netherlands and Cornell University (CU), United States of America. This cross-pollination has resulted in fundamental understanding and novel strategies for controllably forming calcite crystal composite materials in hydrogel systems. This work not only adds to our understanding of how Nature forms her mineralized tissues; it also provides the first promising platform for rationally controlling bacteria-induced mineral precipitates for self-healing concrete applications. The next phase of the project will seek to gain such control over bacteria-induced mineral precipitation and incorporate this technology into cementitious materials. It is envisaged that the resulting Biocrete will have a superior crack healing action over conventional concrete, resulting in better functional performance and more durable, sustainable concrete construction.
The Biocrete project was split into two distinct phases. Phase 1 (0-24 months, and subject of the 1st Periodic Report) of the project was conducted at Cornell University (CU), United States of America (USA) and Phase 2 (24-36 months, and the subject of this the 2nd Periodic Report) was conducted at the Delft University of Technology (TUD), the Netherlands (NL). Phase 1 and 2 had distinct research and career objectives, which were to be achieved in line with Annex 1 of the Grant Agreement (GA). In Phase 1, a series of novel biologically inspired crystal-polymer composite materials were developed. Specific career objectives were also achieved, including the development of a course module titled BioForm, which was delivered at the National College of Art and Design (NCAD), Dublin, Ireland (IRE). In Phase 2, the bio-inspired crystal-composites developed during Phase 1 were analysed, and detailed mechanistic models are being developed describing their formation, and a review paper has been prepared on crystal composite formation. Specific career objectives have also been achieved, including the applicant extending his scientific knowledge and competences, mentoring and leadership skills, research network and grant writing skills.
The Biocrete project has seen a series of novel approaches developed for physico-chemically controlling calcite crystal form in hydrogel systems. Mechanical control was exerted over calcite crystals within structured hydrogels (void of chemical functionality). Drying and rehydration of agarose gel films result in their affine deformation parallel to the drying plane. Precipitation of calcium carbonate in the film results in the formation of calcite composite discs oriented perpendicular to the drying plane. Nano computer tomography analysis of the crystallites reveals a shape evolution. This shape evolution can be described by linear-elastic fracture mechanics theory, which is dependent on the ratio between the width of the crystallites and the elasto-adhesive length scale of the gel. Further, precipitation of calcium carbonate in uniaxially deformed agarose fibers results in the formation of rice-grain shaped crystallites. Building on the work, physico-chemically control was exerted over the morphology and polymorph of calcium carbonate-based phases via the addition of magnesium and amino acids to gel systems. This work not only adds to our understanding of how Nature forms her mineralized tissues; it also provides the first promising bio-inspired platform for rationally controlling bacteria-induced mineral precipitates for self-healing concrete applications.