A lab study highlighted a new twist on microbially induced calcite precipitation, a process that uses bacteria to form calcium carbonate that binds granular materials together. Instead of adding free-floating bacteria to an aggregate bed, the researchers grew ureolytic bacterial biofilms directly on aggregate particles first. That change boosted how much bacteria stayed on the particles during flushing and improved how evenly carbonate minerals formed at particle-to-particle contact points.
The team tested two aggregates: silica sand sourced from Giza, Egypt, and recycled fired clay brick fines from a local brick manufacturing facility. Both materials were crushed and sieved to 150 to 300 micrometers, then washed, dried, and sterilized before inoculation with Sporosarcina pasteurii.
On sand grains, biofilm-coated particles showed about 78% surface biomass coverage after washing, versus 9.8% for planktonic dosing. In the biocemented columns, the difference showed up in the microstructure. Planktonic treatments produced more isolated mineral deposits, while biofilm treatments produced more continuous calcite-like bridges between grains. Compressive strength for sand rose from 1.6 plus or minus 0.5 MPa to 4.3 plus or minus 1.0 MPa. For recycled brick fines, compressive strength rose from 1.0 plus or minus 0.7 MPa to 8.5 plus or minus 0.6 MPa.
For mason contractors tracking material trends, the recycled brick result stands out. It links circular construction goals with performance data, and it points toward future precast, non-structural masonry units that use reclaimed brick feedstocks. The study also flags jobsite realities that need answers first, including long-term durability testing for moisture exposure, freeze-thaw, and dimensional stability.
The authors also noted hurdles before field use, including the need to prove biofilm growth in non-sterile industrial settings, find lower-cost nutrient sources, and manage ammonium byproducts from urea hydrolysis.
Read the full, original article from Bioengineer.org here.