Incineration bottom ash is generated by the incineration of solid waste. Household solid waste is increasing every year and so is incineration bottom ash. This is a problem to treat the incineration bottom ash because the ash has many toxic components. Cement composites can solve this problem and there are many studies for using the bottom ash as fine aggregate. To evaluate the usage of incineration bottom ash, compressive strength, mercury intrusion porosimetry, scanning electron microscopy-backscatter electron, X-ray diffraction, and toxicity characteristic leaching processes were performed. When using incineration bottom ash up to 20% of substitution, the compressive strength in all cases was increased. This study showed how the filler effect appeared well in the cement composites through the scanning electron microscopy-backscatter electron, and mercury intrusion porosimetry. X-ray diffraction indicated the possibility of an alkali-silica reaction of the aggregate with the components of incineration bottom ash. This problem is an obstacle to applying the incineration bottom ash as a fine aggregate. In addition, the toxicity characteristic leaching process was shown to be under the threshold of the Korean standard, however, this should nuanced by the consideration of amorphity. Comprehensively, incineration bottom ash could be used as a fine aggregate of up to 20% of substitution. However, the pre-treatment would need to eliminate or reduce alkali reactive components and heavy metals.

No abstract

No abstract

Currently the control of prestressing force and cracks on concrete structures is designed deterministically. However, the statistical variations of materials could make additional error in the prediction and the control of errors. Therefore, to develop a probabilistic risk assessment technique in Prestressed Concrete (PSC) box girder railway bridges, the important random variables are determined by an Analytical Hierarchy Process (AHP) method for the risk assessment of the target PSC box girder bridge constructed by a Movable Scaffolding System (MSS) method. The limit state functions are determined to investigate the risk of tensile cracks in upper and lower flange concrete, just after the moving of scaffolding, and the risks of the prestressing loss at each construction stage. In order to compose the implicit limit state function of the target PSC railway bridge, the developed linear adaptive weighted response surface method combined with a first order second moment method is applied for the evaluation of reliabilities of the considered limit states.