Long-Term Self-Healing Efficiency of Bioconcrete Based on Integrated Sulfate- and Nitrate-Reducing Bacterial Granules

This study evaluated the mechanical properties and self-healing performance of freshly casted and 19-month-aged bioconcrete samples with integrated sulfate-reducing bacteria (SRB) and nitrate-reducing bacteria (NRB) granules that were cultivated in an upflow anaerobic sludge blanket (UASB) reactor with synthetic wastewater. The 28-day compressive strength fulfilled the design requirement of 50 MPa. The apparent volume of permeable voids (AVPV) of fresh and aged bioconcrete met the limit of 13%. The self-healing ability was determined by exposing cracked bioconcrete to water media such as glucose, calcium acetate, tap water, and wastewater, which have shown calcite deposition in fresh and aged samples. The highest amount of calcite deposition was seen on fresh samples after glucose exposure (420 μm) and on aged bioconcrete after calcium acetate exposure (320 μm). Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS/XRD) results demonstrated that SRB/NRB granules survived mortar integration and deposition of calcite in both fresh and aged samples. The water permeability and acid resistance of bioconcrete samples were correlated to the amount of deposited calcite.