Cường độ và độ bén hóa học của bê tông sử dụng pozzolan tự nhiên và bột đá vôi

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Tác giả: Thị Ly Phạm, Văn Toàn Phạm

Ngôn ngữ: Vie

Ký hiệu phân loại: 691 Building materials

Thông tin xuất bản: Giao thông vận tải 2023

Mô tả vật lý: 124-127

Bộ sưu tập: Metadata

ID: 406532

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Nghiên cứu đánh giá ảnh hưởng của pozzolan tự nhiên và bột đá vôi đối với sự phát triển cường độ và sức kháng của bê tông trong môi trường hóa chất chứa axit. Trong nghiên cứu này, 4 mẫu cấp phối bê tông được sử dụng: bê tông chỉ sử dụng cốt liệu mịn thông thường, bê tông sử dụng pozzolan tự nhiên, sử dụng bột đá vôi thay thế một phần cốt liệu mịn và bê tông sử dụng cả hai thay thế một phần cốt liệu mịn. Tỉ lệ thay thế cốt liệu mịn của pozzolan tự nhiên và bột đá vôi lần lượt là 55% và 5% thể tích cốt liệu mịn. Sau khi đúc, các mẫu bê tông được bọc kín lớp băng dính nhôm tránh thoát hơi nước và bảo quản ở nhiệt độ 2O°C cho đến ngày tiến hành thí nghiệm kiểm tra. Đối với thí nghiệm ngâm mẫu trong môi trường hóa chất, các mẫu bê tông sau khi bảo dưỡng 56 ngày được ngâm trong hỗn hợp dung dịch chứa 3% H2SO4 and 5% MgCI2, được sử dụng để làm mô hình cho môi trường hóa chất mạnh chứa các lon H+, SO42", Mgz* và Cl". Kết quả thí nghiệm chỉ ra rằng cường độ của bê tông chứa pozzolan tự nhiên cao hơn cường độ của bê tông không chứa pozzolan tự nhiên ở 28 và 91 ngày tuổi. Thêm vào đó, sau 12 tuần ngâm trong hỗn hợp dung dịch, mức giảm cường độ, chiều sâu trung hòa và chiều sâu thấm chloride của bê tông chứa pozzolan tự nhiên có giá trị thấp hơn so với bê tông không chứa pozzolan tự nhiên. Ngược lai, vai trò của bột đá vôi trong quá trình cải thiện cường độ nén và độ bền hóa chất của bê tông là không đáng kể. Hơn nữa, thí nghiệm xác định hàm lượng porlandite Ca(OH)2 trong bê tông chứa pozzolan tự nhiên thấp hơn so với bê tông không chứa pozzolan tự nhiên ở các tuổi bê tông muộn đã chỉ ra rằng, hoạt tính của pozzolan tự nhiên đã góp phần cải thiện cường độ và độ bền của bê tông., Tóm tắt tiếng anh, This study investigates the effect of limestone powder and natural pozzolan as fine aggregate replacement on the strength development and the resistance of concrete to aggressive chemical. In this study, ordinary Portland cement and crushed stone were used as cement and coarse aggregate, respectively, and a water-to-cement ratio of 40% was used in all concrete mixture proportions. Four mixture proportions were designed: concrete using only general fine aggregate and concrete with partial fine aggregate replacement by limestone powder, by natural pozzolan, and by both of them. The replacement ratios of fine aggregate by limestone powder and natural pozzolan were 5% and 55% by volume, respectively. After casting, the specimens were sealed with aluminum adhesive tape and stored at 2O°C until the designated test days. For immersion test, specimens cured until the age of 56 days were immersed in mixed solution containing 3% H2SO4 and 5% MgCI2, which is intended to simulate an aggressive environment containing H+, SO42', Mg2+ and Cl" ions. The results show that the compressive strength of concrete containing natural pozzolan was higher than that of concrete without natural pozzolan at the ages of 28 and 91 days. Furthermore, after 12 weeks of immersion in mixed solution, the compressive strength loss, neutralization depth and chloride penetration depth of concrete containing natural pozzolan were lower than those of concretes without natural pozzolan. On the other hand, the role of limestone powder in improvement of compressive strength and resistance of concrete was not prominent. In addition, considering that Ca(OH)2 content in concrete with natural pozzolan were lower than that in concretes without natural pozzolan at later age, the pozzolanic reactivity of natural pozzolan could enhance the compressive strength and the resistance of concrete to aggressive chemical environment.

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