Sulfate Attack on Concrete - Chapter 8

Case histories - Kể từ khi giới thiệu các tiêu chuẩn có liên quan và mã ở các nước công nghiệp, sự xuất hiện của các cuộc tấn công sulfate nội bộ và bên ngoài trong bê tông được thiết kế, chế biến và thực hiện là rất hiếm. Khi thiệt hại xảy ra, nó luôn luôn là hậu quả của việc xây dựng không chính xác cho phép thâm nhập vào cụ thể của các giải pháp dung dịch nước muối cần thiết để bắt đầu và thức ăn tấn công. Hầu hết các khuyến nghị hệ thống. | 8 Case histories Since the introduction of relevant standards and codes in industrialized countries occurrence of internal and external sulfate attack in properly designed processed and executed concrete is rare. When damage occurs it is always the consequence of incorrect construction that enables penetration into concrete of aqueous salt solutions needed to initiate and feed the attack. Most of the codified recommendations are based on prescription of maximum values for water-cement ratio maximum levels of C3A in cement and in some cases of minimum cement content and addition of supplementary materials such as selected pozzolanas or slags or both. As the sulfate-generated distress is largely a function of concrete quality the primary objective of the precautionary measures is to decrease the accessibility of sulfate bearing solutions into concrete by decreasing its permeability. A well-constructed impermeable concrete structure will not suffer from sulfate attack regardless of the prevailing environmental conditions and physico-chemical mechanisms . potential for ettringite thaumasite gypsum or efflorescence formation . According to Mehta and Monteiro 1993 The quality of concrete specifically a low permeability is the best protection against sulfate attack. Adequate concrete thickness high cement content low water cement ratio and proper compaction and curing of fresh concrete are among the important factors that contribute to low permeability. In the event of cracking due to drying shrinkage frost action corrosion of reinforcement or other causes additional safety can be provided by the use of sulfate-resisting In other words properly designed and constructed concrete will be stable under most aggressive conditions unless the concentration of sulfates in the soil or the water in contact with the concrete is extreme. Under such conditions additional measures have to be taken to prevent direct contact between the concrete and the SO2 source. However .