Ferdowsi Civil Engineering

Ferdowsi Civil Engineering

Investigation of the Self-Healing Performance and Microstructural Evolution of Concrete Produced with Dredged Sand and Persian Gulf Water Using Bacillus subtilis Bacteria and Silica Fume.

Articles in Press

Document Type : Original Article

Authors
Seyed Mohammad Mehdi Asadzadeh 1
Mohammadreza Baradaran 2
Gholamreza Atefatdoost 3
1 Department of Civil Engineering, Es.C., Islamic Azad University, Estahban, Iran. Email: mehdi.asadzadeh@iau.ac.ir
2 Department of Civil Engineering, Fir.C., Islamic Azad University, Firoozabad, Iran
3 Department of Civil Engineering, Es.C., Islamic Azad University, Estahban, Iran
10.22067/jfcei.2026.98292.1402
Abstract
Despite the potential of seawater and dredged marine sand as sustainable alternatives in concrete production, the presence of ions such as Cl⁻, SO₄²⁻, Mg²⁺, and Ca²⁺ may promote microcrack propagation and reduce long-term durability. In this study, the interaction between microbial-induced calcium carbonate precipitation (MICP) mediated by Bacillus subtilis and silica fume (SF) in seawater sea-sand concrete (SWC) was investigated. The results indicate that the self-healing mechanism is governed by multi-ionic equilibrium, and the efficiency of the MICP pathway strongly depends on ionic ratios, particularly Ca²⁺. The reduction of the Ca/Si ratio in the presence of SF, due to the consumption of Ca(OH)₂ and formation of C–S–H phases, limited the availability of Ca²⁺ for MICP activity and reduced precipitation uniformity. In contrast, maintaining an effective Ca²⁺ concentration facilitated continuous nucleation and growth of CaCO₃ crystals along crack surfaces. Moreover, Mg²⁺ altered the precipitation pathway toward less stable polymorphs such as aragonite, while SO₄²⁻ ions reduced the healing capacity by promoting ettringite formation. Overall, although SF improves pore structure and reduces permeability, its synergistic efficiency with MICP is highly dependent on precise control of pore solution chemistry, particularly Ca²⁺ balance.
Keywords
Self-healing concrete
calcium carbonate precipitation
silica fume
durability
Persian Gulf seawater and sand
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Ferdowsi Civil Engineering

Articles in Press, Accepted Manuscript
Available Online from 23 June 2026