High strength bio-concrete for the production of building components

Abstract

The production of bio-concrete is based on the process of microbially-induced calcium carbonate precipitation (MICP), in which calcium carbonate (CaCO 3 ) is formed as a binder. Bio-concrete is a potentially CO 2 -neutral alternative to conventional Portland-cement-based concrete, since no process-related carbon dioxide emissions are generated during biomineralization. Furthermore, CO 2 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.