High strength bio-concrete for the production of building components

The production of bio-concrete is based on the process of microbially-induced calcium carbonate precipitation (MICP), in which calcium carbonate (CaCO3) is formed as a binder. Bio-concrete is a potentially CO2-neutral alternative to conventional Portland-cement-based concrete, since no process-related carbon dioxide emissions are generated during biomineralization. Furthermore, CO2 is bound in the form of carbonate. However, achieving compressive strength values comparable to conventional concrete, in combination with sufficient component depth, has been a significant challenge in the MICP research. In the present study, a combination of methods was implemented, including the use of urease-active calcium carbonate powder (UACP) instead of free bacterial cells, optimization of aggregate packing density, and the implementation of an automated stop-flow pressure injection method. A variety of cementation parameters were tested to determine the optimal conditions for the production of homogeneously cemented high strength bio-concrete. Additionally, reproducibility and optimization studies have been conducted with selected parameter combinations. It was found that achieving homogeneous compaction with sufficient aggregate packing density played a crucial role in obtaining consistent and high-quality cementation results. A combination of a very high compressive strength of 52.5 MPa and a cementation depth of 140 mm has been reached, which has not been reported in previous publications. These findings might unveil new possibilities for bio-concrete to be used in the production of prefabricated load-bearing building components, where it could partially replace traditional concrete.