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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/3446

    Title: 飛灰調質熔渣成份對卜作嵐反應特性之影響;Characteristic study on the pozzolanic reactivity of slag derived from component modification of MSW fly ash
    Authors: 林家宏;Chia-Hung Lin
    Contributors: 環境工程研究所
    Keywords: 焚化飛灰;熔融處理;鹽基度;熔渣;卜作嵐反應;slag;MSW fly ash;melting process;basicity;pozzolanic characteristics
    Date: 2004-06-05
    Issue Date: 2009-09-21 12:16:16 (UTC+8)
    Publisher: 國立中央大學圖書館
    Abstract: 摘 要 本研究係針對都市垃圾焚化飛灰(旋風集塵灰與洗滌灰的混合物)難以單獨熔融之特性,利用SiO2、Al2O3及P2O5等進行鹽基度調整以降低其熔流溫度,主要分為三種系列(S系、A系及P系)以不同配比混合進行調質熔融處理,將調質熔渣製成不同取代量之熔渣水泥漿體。本研究除建立都市垃圾焚化飛灰物化特性與調質熔渣之基本特性外,亦探討不同養護齡期下熔渣水泥漿體之工程材料特性及卜作嵐反應行為,包括抗壓強度、卜作嵐活性指數、水化程度、水化產物種類及微結構觀察等。 實驗結果顯示,各系調質熔渣CaO、SiO2、Al2O3及P2O5,其含量分別為29?35%、36?45%、9?20%及2?13%,大致符合ASTM C989 高爐熟料規範之要求,具有延長水泥澆鑄工作時間之特性。對90天齡期抗壓強度發展而言,取代量10、20%之A系熔渣水泥漿體可超越OPC 1?14 MPa;而P系熔渣水泥漿體則可與OPC之抗壓強度發展相當(差值<5 MPa)。而卜作嵐活性指數分佈於78-106%之範圍內,其中P系熔渣之活性指數為98-106%,具有較佳之反應性,而A系為81-95%次之,最低為S系熔渣79-80%,其卜作嵐活性發展較不明顯。由XRD、 DTA及FTIR之物種分析得知,熔渣水泥漿體與OPC之主要水化產物皆為CH、C-S-H及C-A-H。由NMR分析發現,隨齡期之增加,單矽酸根逐漸轉變為高濃縮矽結構的C-S-H 膠體,聚矽陰離子長度至齡期90天皆大於純水泥漿體,顯示水化晚期熔渣之卜作嵐反應有助於漿體內部矽酸鹽類之聚合。由SEM觀察得知,熔渣漿體會產生六角層片狀CH水化物、球形針狀 C-S-H 膠體及部分鈣釩石與單硫型鋁酸鹽,同時隨卜作嵐反應持續進行而逐漸成長相互接觸交織成網狀結構,能有效減少孔隙並使孔隙緻密化,進而提升漿體強度。綜合上述結果,調整鹽基度後進行熔融處理可將都市垃圾焚化飛灰無害化,且所得熔渣具有材料化之潛力。 Abstract MSW incinerator fly ash, comprisedof mixed cyclone ash and lime-reactant ash is characterized by its high melting point and is thus difficult to melt effectively and economically, without modification of its components. This study investigated the effects of the modification of the fly ash's basicity on the pozzolanic characteristics of the resultant melts. The modification was made by adding SiO2 to bring the basicity closer to unity; subsequent additions of Al2O3 and P2O5 to the previous modifications were also evaluated. These modifications resulted in three types of fly ash, referred to as the S-, A-, and P- modified series, respectively. All the resultant slag samples were pulverized to prepare cement pastes with various portions of the cement being replaced. The pozzolanic characteristics were evaluated at various curing ages by examining the pozzolanic activity, hydration degree,the hydration products and their microstructure, as well as the engineering properties of the pastes. The results indicate that all the slag samples resulted from the modified fly ash contained CaO(9~35w/w%), SiO2(36~45w/w%), Al2O3(9~20w/w%), and P2O5(2~13w/w%), respectively; all met the specification of ASTM C989 for blast furnace slag, and showed properties that would delay the setting time of the resultant mortars. The pozzolanic activity for all the tested slag samples ranged from 78% to 106%.The P-modified series slag showed a greater activity (98~106%) than did the A-modified series slag(81~95%), whereas the activity developed in the S-modified series samples was less distinctive(79~80%), as compared to that of OPC.As to the compressive strength at 90-days, the A-modified series samples ,with a 10% and 20% cement-replacement, outperformed the OPC samples by 1~14 MPa, whereas the P-modified series exhibited compressive strength development close to that of OPC, by less than 5 MPa. XRD, DTA, and FTIR speciation analyses indicated that the main hydrated products of all tested samples included calcium hydroxide(CH), calcium silicate hydrate (C-S-H), and calcium aluminate hydrates(C-A-H). Moreover, the NMR results indicate that the number of Si linear polysilicate anions in the C-S-H gel increased with increasing age, and outperformed that of OPC at 90 days, suggesting that pozzolanic reactions in the slag contributed to the later formation of calcium silicate hydrate (C-S-H). This was also indicated by the SEM analysis, from the formation of hexagonal sheets of CH hydrates, round and needle-surfaced C-S-H gels, ettringite (Ca6Al2(SO4)3.32H2O), and monosulfate. These products grew to intersecting to form a network structure, which increased the distribution of the finer pores, eliminated the porosity, and thus increased the compressive strength of the pastes.The results of this study demonstrated that MSW fly ash could be melted at a lower temperature when its basicity was modified, thus producing the targeted type of slag, with pozzolanic characteristics close to or outperforming those of OPC.
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