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<p>The development of self-healing materials offers concrete structures increased durability and lowered maintenance costs. This strategy has drawn extensive research focus as a self-sustaining approach to resource preservation. This research analyzes the mechanical, microstructural, and self-healing characteristics of geopolymer concrete containing bacteria, referred to as self-healing geopolymer concrete (SHGC). Bacillus sphaericus (B2) and Bacillus subtilis (B1) served as biological healing agents while eggshell powder (ESP) functioned as a calcium and carbohydrate-rich nutrient medium to foster bacterial activity. With strains B1 and B2, twelve SHGC mixtures were prepared with varying concentrations of ESP at 5%, 10%, and 15% by weight of fly ash. The compressive, flexural, and split tensile strength tests conducted after 28 days of curing assessed the mechanical performance. Microstructural examination was accomplished with scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The visual observation on the 1st, 3rd, and 7th day after cracking presents the skeletal structure with gaps filled, which corresponds to the healing process of the cracks. These results illustrated marked changes to the mechanical properties, with strength increasing by 5.5–15.1% for different bacteria cases and with nutrient variations. The B2 + 5% ESP mixture showed the highest compressive strength of 60.9&#xa0;MPa, while the B2 + 10% ESP mixture exhibited better performance in crack healing. These results further emphasize that bacterial supplementation along with organic nutrients can be utilized in geopolymers systems to optimally increase not only the strength, but also the durability of environmentally friendly concrete materials.</p>

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Effect of eggshell powder as fly ash replacement and nutrient source for bacteria on the properties and self-healing of geopolymer concrete

  • 期刊论文

  • 发表日期：

    2025年8月20日

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  • Nour Bassim Frahat,
  • Omar Mohamed Omar Ibrahim,
  • Ibrahim Saad Agwa,
  • Mohamed M. Attia,
  • Abdullah M. Zeyad,
  • Salha G. Desouky

摘要

The development of self-healing materials offers concrete structures increased durability and lowered maintenance costs. This strategy has drawn extensive research focus as a self-sustaining approach to resource preservation. This research analyzes the mechanical, microstructural, and self-healing characteristics of geopolymer concrete containing bacteria, referred to as self-healing geopolymer concrete (SHGC). Bacillus sphaericus (B2) and Bacillus subtilis (B1) served as biological healing agents while eggshell powder (ESP) functioned as a calcium and carbohydrate-rich nutrient medium to foster bacterial activity. With strains B1 and B2, twelve SHGC mixtures were prepared with varying concentrations of ESP at 5%, 10%, and 15% by weight of fly ash. The compressive, flexural, and split tensile strength tests conducted after 28 days of curing assessed the mechanical performance. Microstructural examination was accomplished with scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The visual observation on the 1st, 3rd, and 7th day after cracking presents the skeletal structure with gaps filled, which corresponds to the healing process of the cracks. These results illustrated marked changes to the mechanical properties, with strength increasing by 5.5–15.1% for different bacteria cases and with nutrient variations. The B2 + 5% ESP mixture showed the highest compressive strength of 60.9 MPa, while the B2 + 10% ESP mixture exhibited better performance in crack healing. These results further emphasize that bacterial supplementation along with organic nutrients can be utilized in geopolymers systems to optimally increase not only the strength, but also the durability of environmentally friendly concrete materials.