Sulfate Attack on Concrete - Chapter 9

Assessment of cement and concrete performance under sulfate attack - Đánh giá việc thực hiện dự kiến của xi măng và bê tông để được tiếp xúc với sunfat có thể dựa trên thử nghiệm hoặc dự đoán hoặc cả hai. Mục đích của đánh giá là để tránh thiệt hại cụ thể, rút ngắn tuổi thọ do việc sử dụng một chất kết dính không phù hợp hoặc hỗn hợp bê tông. Một thử nghiệm lý tưởng nên được đơn giản như có thể, kết quả năng suất trong một khoảng thời gian ngắn, và thông tin đáng. | 9 Assessment of cement and concrete performance under sulfate attack The assessment of the expected performance of cement and concrete to be exposed to sulfates may be based on tests or predictions or both. The purpose of assessment is to avoid concrete damage or shortened life due to the use of an inappropriate binder or concrete mixture. An ideal test should be as simple as possible yield results within a short period of time and present reliable information about the concrete performance that may be expected under field conditions. Basically for convenience two different types of sulfate attack may be defined with the testing procedure and method of evaluation of the test results being different for each In internal sulfate attack the deleterious action of sulfates is brought about by an excessive SO3 content in the binder or less often in the aggregate used. Under these conditions the whole volume of the material is affected more-or-less uniformly. The extent of damage depends on the composition of the mixture the curing conditions and the environment to which the object of concern is exposed. In external sulfate attack the sulfates responsible for the damage migrate into the concrete from an outside source. Under this condition an altered layer resulting from the action of sulfates develops on the surface in contact with the sulfate-containing water or soil while as the material in deeper regions stays unaffected. The performance of the concrete will depend not only on the binder employed but to a great degree also on the mixture proportions and the resultant permeability to the sulfate solution. The following facts have to be considered in assessing the expected performance under sulfate attack A cement may perform differently if exposed to different forms of sulfate . alkali sulfates magnesium sulfate sulfuric acid etc. . 2002 Jan Skalny Jacques Marchand and Ivan Odler The results obtained will depend not only on the binder employed but also on the .