Sulfate Attack on Concrete - Chapter 6

Prevention of sulfate attack - Bê tông phục vụ thường tiếp xúc với môi trường tích cực. Mặc dù điều kiện phơi nhiễm nghiêm trọng đôi khi có thể có nguồn gốc suy thoái sớm của các vấn đề cụ thể, độ bền thường bắt nguồn từ một sản xuất không phù hợp và sử dụng của vật liệu. Như đã đề cập trong chương đầu tiên của chuyên khảo này, người đàn ông lạm dụng cụ thể trong nhiều cách khác nhau, hầu hết trong số họ dựa trên một kiến thức không đủ của vật liệu. Tuy. | 6 Prevention of sulfate attack INTRODUCTION Concrete in service is often exposed to aggressive environments. Although severe exposure conditions may sometime be at the origin the premature degradation of concrete durability problems often originate from an improper production and use of the material. As mentioned in the first chapter of this monograph man abuses concrete in various ways most of them based on an insufficient knowledge of the material. It should however be emphasized that it is relatively simple and economical to produce durable concrete. We have numerous examples of durable concrete structures that have performed as expected for decades while being exposed to severe conditions. In all cases concrete had been produced and handled with care. As discussed in Chapters 4 and 5 the widespread occurrence and destructiveness of sulfate attack led to many investigations over the years into the mechanism of deterioration. Many of these studies have also allowed identification of practical solutions to protect concrete against sulfate attack. These prevention methods are briefly reviewed in the following paragraphs. MEASURES TO PROTECT CONCRETE AGAINST COMPOSITION-INDUCED INTERNAL SULFATE ATTACK As previously mentioned in Chapter 4 cement itself may be a source of excessive sulfate in concrete. This is the reason why requirements of CEN ASTM see ASTM C150 ASTM C1157 BS 5328 and other standards on cement and clinker composition should be closely followed this will assure proper concentrations and ratios of the relevant clinker minerals to give sulfate levels that will not lead to excessive expansion. Aggregates and mineral additives are other potential sources of excessive sulfate. Selected aggregates and intermixed mineral admixtures should not contain 2002 Jan Skalny Jacques Marchand and Ivan Odler sulfate-bearing compounds that may later become available for reaction with cement components of the concrete mixture. Quality Control is clearly one key .