延遲性鈣礬石形成與鹼-骨材反應引致劣化機制;The effect of delayed ettringite formation and alkali-silica reaction in concrete

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题名:	延遲性鈣礬石形成與鹼-骨材反應引致劣化機制;The effect of delayed ettringite formation and alkali-silica reaction in concrete
作者:	郭偉民;Kuo,Wei-min
贡献者:	土木工程研究所
关键词:	延遲性鈣礬石鹼-骨材反應;高溫養護;掃描式電子顯微鏡;High Temperature Curing;DEF;ASR;SEM
日期:	2012-07-28
上传时间:	2012-09-11 18:04:27 (UTC+8)
出版者:	國立中央大學
摘要:	本文探討混凝土產生延遲性鈣礬石形成與鹼-骨材反應的劣化機制，不論延遲性鈣礬石形成或鹼-骨材反應都會使混凝土產生明顯膨脹，自行設計膨脹量試驗，並使用掃描式電子顯微鏡與維區元素分析儀觀察延遲性鈣礬石形成、鹼-骨材反應與兩者並存之試體反應機制。膨脹量試驗使用砂漿棒試體，砂漿棒分別使用標準砂與水泥製作，另一組砂漿棒使用安山岩與水泥製作，並使用不同的實驗條件，如硫含量(0%和5%)與養護溫度(20℃、70℃和85℃)。結果顯示硫含量與養護溫度對於延遲性鈣礬石形成有重大影響，砂漿棒試體在晚期會產生包圍骨材的裂縫引致明顯膨脹，砂漿棒試體同時存在鹼含量、水及反應性骨材會產生鹼-骨材反應。此外，延遲性鈣礬石形成晶體與鹼-骨材反應膠體可以使用掃描式電子顯微鏡與維區元素分析儀進行微觀形貌與化學成分的觀測。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 mortarbars 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 wereplaced 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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