| Summary: | 碩士 === 國立成功大學 === 土木工程學系 === 105 === Steel slag is an inevitable by-product from the process of steelmaking. According to the method we used for the process of steelmaking, steel slag can be divided into four groups: desulfurization slag, BOF slag, recovered arc furnace slag and oxidated arc furnace slag. Most of the four steel slags normally contain free calcium oxide, which can react with water and then typically lead to volume expansion and deterioration. In order to reutilize steel slag as a gravel grade ingredient in pavement and construction, steel slag is usually stabilized using a thermal and chemical process to avoid its volume expansion in service. However, in some construction companies, steel slag is reused as a pavement material and mixed directly with gravel aggregates to lower their construction cost. Steel slag could be misused by ready-used concrete plants as fine aggregate in concrete, resulting in the occurrence of damage cracking and possibly catastrophic failure of concrete construction and buildings. The existing test methods, used to determine if steel slags are contained in aggregate samples, often take a long time to conduct all required experiments. At the same time, the existing test methods are unable to measure the steel slag contents of aggregate samples and to determine the existence of steel slag in fresh slurry and hardened concrete samples. In this study, a rapid test procedure for the measurements of steel slag contents either in an aggregate, fresh slurry or hardened concrete sample will be first developed and then verified. The rapid test procedure consists of three major test methods including gravity separation, pH value measurement and magnetic attraction. As a result, the type of steel slag and its content in a sample of either aggregate, fresh slurry or hardened concrete can be easily, directly and quickly determined.
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