| Summary: | 碩士 === 國立中央大學 === 土木工程研究所 === 100 === This paper presents the determination of concrete deterioration, which is contributed by delayed ettringite formation (DEF) and alkali-silica reaction (ASR). The deterioration process of either DEF or ASR is associated with expansion. This paper employed “self-designed expansionary test”, Scanning Electron Microscopy (SEM), and Energy Dispersive Spectrometer (EDS) to observe DEF, ASR, and coupled DEF-ASR reactions mechanisms. The mortar
bars were used in the proposed expansionary test. One kind of mortar bar consisted of standard sand and cement; the other consisted of andesite and cement. Parametric study is also introduced in this paper, all of mortar bars were
placed at different sulfur contents (0% and 5.2%) and various curing temperatures (20℃, 70℃, and 85℃) in experimental conditions. The results show that the curing temperature and sulfur content play important roles for DEF,
which will induce great expansion by many micro-cracks surrounding aggregates at the latter period of mortar age. ASR is based upon the environments of alkali content, water content, and reactive aggregates in mortar bars. Moreover,micro-features and chemical compositions of delayed ettringite crystal and alkali-silica gel can be precisely observed by using SEM and EDS.
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