Self-Healing Bio-Concrete Using Bacillus subtilis Encapsulated in Iron Oxide Nanoparticles

Faisal Mahmood; Sardar Kashif Ur Rehman; Mohammed Jameel; Nadia Riaz; Muhammad Faisal Javed; Abdelatif Salmi; Youssef Ahmed Awad

doi:10.3390/ma15217731

Self-Healing Bio-Concrete Using Bacillus subtilis Encapsulated in Iron Oxide Nanoparticles

Materials (Basel). 2022 Nov 3;15(21):7731. doi: 10.3390/ma15217731.

Authors

Faisal Mahmood¹, Sardar Kashif Ur Rehman¹, Mohammed Jameel², Nadia Riaz³, Muhammad Faisal Javed¹, Abdelatif Salmi⁴, Youssef Ahmed Awad⁵

Affiliations

¹ Department of Civil Engineering, COMSATS University Islamabad, Abbottabad Campus, Abbottabad 22060, Pakistan.
² Department of Civil Engineering, King Khalid University, Abha 61421, Saudi Arabia.
³ Department of Environmental Sciences, COMSATS University Islamabad, Abbottabad Campus, Abbottabad 22060, Pakistan.
⁴ Department of Civil Engineering, College of Engineering in Alkharj, Prince Sattam bin Abdulaziz University, Alkharj 16273, Saudi Arabia.
⁵ Structural Engineering Department, Faculty of Engineering and Technology, Future University in Egypt, New Cairo 11835, Egypt.

Abstract

For the creation of healable cement concrete matrix, microbial self-healing solutions are significantly more creative and potentially successful. The current study investigates whether gram-positive "Bacillus subtilis" (B. subtilis) microorganisms can effectively repair structural and non-structural cracks caused at the nano- and microscale. By creating an effective immobilization strategy in a coherent manner, the primary challenge regarding the viability of such microbes in a concrete mixture atmosphere has been successfully fulfilled. The iron oxide nanoparticles were synthesized. The examined immobilizing medium was the iron oxide nanoparticles, confirmed using different techniques (XRD, SEM, EDX, TGA, and FTIR). By measuring the average compressive strength of the samples (ASTM C109) and evaluating healing, the impact of triggered B. subtilis bacteria immobilized on iron oxide nanoparticles was examined. The compressive strength recovery of cracked samples following a therapeutic interval of 28 days served as a mechanical indicator of the healing process. In order to accurately correlate the recovery performance as a measure of crack healing duration, the pre-cracking load was set at 80% of the ultimate compressive stress, or "f c," and the period of crack healing was maintained at 28 days. According to the findings, B. subtilis bacteria greatly enhanced the compressive strength and speed up the healing process in cracked cement concrete mixture. The iron oxide nanoparticles were proven to be the best immobilizer for keeping B. subtilis germs alive until the formation of fractures. The bacterial activity-driven calcite deposition in the generated nano-/micro-cracks was supported by micrographic and chemical investigations (XRD, FTIR, SEM, and EDX).

Keywords: Bacillus subtilis; bio-concrete; crack healing; iron oxide nanoparticles; microbially induced calcium carbonate.

Grants and funding

The authors extend their appreciation to the Deanship of Scientific Research at King Khalid University for funding this work through the Large Groups Project under grant number (RGP. 2/93/43).