Space bricks: From LSS to machinable structures via MICP

Abstract

In this work, we show that Microbial Induced Calcite Precipitation (MICP) can be used for making consolidated structures – space bricks – using lunar soil simulant (LSS). Sporosarcina pasteurii was used as a bacterial strain to initiate MICP process via ureolytic pathway. An admixture of a naturally occurring biopolymer (guar gum) and a structural reinforcement material (glass fibre) was used to enhance the mechanical properties of the bio-consolidated bricks. When supplemented with guar gum, the compressive strength of the resulting bricks was found to be significantly higher – by nearly six-fold – making them comparable to commercially used mud bricks. The addition of glass fibre reduced this strength a little, but had the benefit of making the space bricks machinable on a conventional lathe. This latter fact enabled the fabrication of precise and free-form shapes post-consolidation, without the need for specialized casting molds or dies. Details of the MICP process were investigated using field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analyses. The route demonstrated here holds great potential for making strong structures in extra-terrestrial habitats, while adhering to the principles of in situ resource utilization.