DEVELOPING THE BIO-GROUT OF REPAIRING CRACKS IN CONCRETE BASED ON MICROBIALLY INDUCED CALCIUM CARBONATE PRECIPITATION USING Sporosarcina pasteurii

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Tác giả: Khanh Son Nguyen, Ngoc Tri Huynh Nguyen, Pham Huong Huyen Nguyen, Thi Nam Phuong Nguyen, Minh Tuan Pham

Ngôn ngữ: eng

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Thông tin xuất bản: Tạp chí Khoa học Công nghệ và Thực phẩm (Tên mới: Tạp chí Khoa học Đại học Công Thương), 2020

Mô tả vật lý: tr.20

Bộ sưu tập: Metadata

ID: 329603

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Gần đây, có nhiều nghiên cứu hơn về việc ứng dụng quá trình tạo tủa calcium carbonate dưới tác động của vi sinh vật (MICP) để sửa chữa các vết nứt bê tông thay vì polymer tổng hợp, chất có thể gây hại cho môi trường. Vi khuẩn mang tính ureolytic, chẳng hạn như Sporosarcina pasteurii, được biết có tiết ra enzyme urease, dẫn đến tạo tủa calcium carbonate trong một môi trường giàu calcium. Dựa trên cơ chế này, các tỷ lệ khác nhau của vật liệu xây dựng và sinh khối S. pasteurii đã được khảo sát để thu được loại vữa tối ưu nhằm giải quyết vấn đề nứt bê tông. Đầu tiên, điều kiện tạo tủa calcium được tối ưu ở pH ban đầu là 6 và nồng độ CaCl2 là 250 mM. Hỗn hợp vữa sinh học tối ưu thu được với cát kích thước 0,1 mm trộn với sinh khối theo tỷ lệ 1:1 với mật độ vi khuẩn là khoảng 108 CFU/mL. Quan sát bằng mắt thường và kiểm tra độ thấm nước cho thấy vữa vi khuẩn có thể sửa chữa các vết nứt và ngăn chặn sự xâm nhập của chất lỏng và khí so sánh với đối chứng âm. Bên cạnh đó, kết quả phân tích SEM và XRD chỉ ra rằng các cấu trúc đa hình carbonate khác nhau được hình thành bên trong các vết nứt. Ngoài ra, phương pháp đổ đĩa cho thấy có các tế bào S. pasteurii sinh dưỡng tồn tại trong các vết nứt ngay cả sau 28 ngày, điều này có nghĩa là vữa vi khuẩn có thể có tác dụng lâu dài trên xi măng.Recently, there is more research on applying microbiologically induced calcium carbonate precipitation (MICP) to repair the concrete cracks instead of synthetic polymers, which may be harmful to the environment. Ureolytic bacteria, such as Sporosarcina pasteurii, have been known to release urease, leading to calcium carbonate precipitation in a calciumrich environment. Based on this mechanism, the different ratios of building materials and S. pasteurii biomass were investigated to obtain the optimized grout to solve the cement cracking problem. Firstly, calcium precipitation condition was optimized at the initial pH of 6 and the concentration of CaCl2 as 250 mM. The optimum bio-grout mixture was obtained with 0.1 mm sand mixed with biomass in ratio of 1:1 with the bacterial density of around 108 CFU/mL. The visual observation and water permeability tests showed that bacterial mortar could repair the cracks and prevent the invasion of liquids and gases compared with the negative control. Besides, SEM and XRD analytical results indicated that the different carbonate polymorphs were formed inside the cracks. Additionally, the plate count method revealed that there were vegetative S. pasteurii cells in cracks even after 28 days, which means the bacterial mortar may have a long-lasting effect on the cement.

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