Bioconcrete based on sulfate-reducing bacteria granules: cultivation, mechanical properties, and self-healing performance

Using waste-activated sludge as a source for non-axenic sulfate-reducing bacterial (SRB) granules, this study developed an innovative bioconcrete with 1% and 2% SRB granules. The mechanical properties (AS 1012.9 and AS 1012.21) and self-healing performance of bioconcrete was systematically examined. The 28-d compressive strength of bioconcrete samples met the design requirement of 50 MPa and the general limit of 13% for average volume of permeable voids (AVPV). Within 3–4 weeks, both 1% and 2% bioconcrete samples precipitated 300–400 µm of calcite in different water media such as glucose, calcium acetate, tap water, and real wastewater. The SEM analysis revealed that SRB granules survived mortar incorporation and precipitated calcium carbonate in the form of calcite which were further confirmed by EDS and XRD analysis. The tap water healed 1% and 2% bioconcrete samples had water permeabilities 64.2% and 69.9% lower than the control, respectively. The mass loss in 5% sulfuric acid was 3.8% and 3.2% less, respectively, for 1% and 2% bioconcrete specimens with surface calcite deposition after 120 d.