Modares Journal of Biotechnology

Improving the performance of concrete bioremediation with a hybrid method of nanosilica and encapsulated spores of Bacillus subtilis bacteria

Document Type : Original Article

Authors

sara Mohseni 1
Nastaran Riahinoori 2
Hossein Koohani 3
Ashkan Zolriasatein 4
Majid Mirzaei 5
Fatemeh Dabir 6

1 Non-Metallic Materials Research Group & Center of Nanotechnology Development, Niroo Research Institute (NRI)

2 Assistant Professor of Nonmetallic Materials Department and Director of the Office of the Director of the Energy Research Institute

3 Director of the Non-Metallic Materials Research Group, Niroo Research Institute

4 Assistant Professor, Department of Non-Metallic Materials and Head of the Educational Complex of the Niroo Research Institute

5 Assistant Professor, Department of Non-Metallic Materials and Deputy Director of Nano Center, Niroo Research Institute

6 Assistant Professor of Non-metallic Materials Research Group

10.48311/biot.2026.116802.82874
Abstract
Introduction: Traditional methods of crack repair in concrete structures are costly and temporary. Bacterial self-healing concrete is proposed as a sustainable solution; however, challenges remain, including the survival of bacteria in concrete's alkaline environment and environmental concerns associated with urea use.
Methods: First, the optimal amount of silica nanoparticles was determined based on compressive strength using experimental design and Statgraphics Centurion software. Bacillus subtilis spores (at a concentration of 3.6 × 109 cells/mL) were encapsulated with nutrients in a sodium silicate gel matrix. Four groups of concrete samples, including a control, a sample containing encapsulated bacteria, a sample containing nanosilica, and a hybrid sample (a combination of bacteria and nanosilica), were prepared in accordance with ASTM C150.
Results: The hybrid sample achieved the highest compressive strength (258 kg/cm²) and modulus of rupture (0.3772 MPa), showing improvements of 8.4% and 4.1% over the control sample, respectively. SEM images showed better structural integrity and the simultaneous presence of nanosilica and bacterial calcium carbonate crystals in the hybrid sample. XRD analysis revealed an increase in the peak intensity of calcium carbonate (at 29.4°) and changes in the peak width at half-height in the hybrid sample, indicating increased crystallinity and enhanced bioremediation activity. Conclusion: The proposed hybrid approach successfully improved bacterial survival, bioremediation efficiency, and mechanical strength of concrete simultaneously. The combination of non-urea resistant spores with microencapsulation in sodium silicate and synergism with nanosilica offers a practical and cost-effective solution for the development of next-generation self-healing concretes

Keywords

Self-healing concrete
bioremediation
Bacillus subtilis
sodium silicate microcapsules
silica nanoparticles
calcium carbonate
Subjects
Modares Journal of Biotechnology
Volume 17, Issue 1
Winter 2026
Pages 77-91

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