都市垃圾焚化熔渣粉體調製環保水泥之卜作嵐反應特性研究; Feasibility Study on Pozzolanic Reactivity of Eco-Cement Incorporating Slags from MSW Incinerator Ashes

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題名:	都市垃圾焚化熔渣粉體調製環保水泥之卜作嵐反應特性研究;Feasibility Study on Pozzolanic Reactivity of Eco-Cement Incorporating Slags from MSW Incinerator Ashes
作者:	林凱隆;Kae-Long Lin
貢獻者:	環境工程研究所
關鍵詞:	卜作嵐反應;熔渣;熔融;焚化灰渣;C-S-H膠體;slag;C-S-H gel;MSWI ash;melting process;pozzolanic activity
日期:	2002-10-08
上傳時間:	2009-09-21 12:13:43 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	本研究針對都市垃圾焚化飛灰進行熔融實驗，並以其熔渣粉體調製不同配比之熔渣水泥，以探討熔渣水泥漿體之卜作嵐反應特性及熔渣粉體取代部份水泥之可行性。本研究之實驗分成四部份，首先探討都市焚化灰渣在1400℃ 下經30分鐘熔融後之熔渣特性；進而以1400℃熔渣粉體備製不同配比(取代量10- 40%)在不同水膠比(0.29-0.55)之飛灰熔渣水泥漿體，分析其於不同養護齡期之卜作嵐反應特性；並以其熔渣粉體備製不同配比之熔渣單礦物漿體，分析其於不同養護齡期之卜作嵐反應行為；最後並探討不同養護齡期下調質熔渣之卜作嵐反應行為與熔渣水泥漿體之工程材料特性。實驗結果顯示，所得之調質熔渣CaO約27?34%，SiO2約29?39%及Al2O3則約8?23%，而非鈣質化物為 47?67%，大致可符合C級飛灰規範之要求，且接近高爐爐石熟料，具有延長水泥澆鑄工作時間之特性。飛灰熔渣水泥漿體之抗壓強度，於養護早期隨著熔渣取代量與水膠比增加而減小，晚期強度則呈明顯上升之趨勢；且低取代量（10%、20%）者超越或接近純水泥，顯示出展現卜作嵐材料提高晚期強度之特性。孔隙結構方面，膠體孔隨著齡期、取代量的增加而增加，熔渣水泥漿體有縮小孔隙之趨勢，另外NMR、XRD分析配合SEM觀察發現，早期漿體即有卜作嵐反應發生，晚期則有消耗Ca(OH)2產生C-S-H膠體的現象，且取代量越大越顯著，顯示熔渣具卜作嵐反應特性，其內部非晶相之活性離子（Si、Al）能消耗水化所形成之Ca(OH)2，而產生C-S-H膠體填充孔隙，將毛細孔轉換成膠孔，進而提高晚期強度。飛灰熔渣可降低矽酸三鈣與鋁酸三鈣漿體之抗壓強度發展，可能係當熔渣添加後，因稀釋效應會減少單礦物之含量。熔渣對矽酸三鈣漿體早期強度有延緩之現象，至晚期則因熔渣之卜作嵐反應而有加速發展之趨勢。而由DTA分析結果顯示，熔渣可延緩鋁酸三鈣由六方相C4AH13轉為立方相C3AH6之時間，且晚期以穩定之立方相C3AH6為主。另外由XRD分析結果顯示，熔渣矽酸三鈣與熔渣矽酸二鈣漿體於養護晚期（60?90天），因卜作嵐反應消耗Ca(OH)2生成CSH膠體與CAH鹽類，且熔渣成分中以Si2+、Al3+對矽酸三鈣之卜作嵐反應影響較大，且熔渣可減緩石膏與鋁酸三鈣形成AFt與AFm之機會，可延緩鋁酸三鈣之初期水化。由NMR分析結果顯示，熔渣矽酸三鈣初期水化程度具延緩之趨勢，而晚期因卜作嵐反應則呈現加速之趨勢，此外，熔渣矽酸三鈣漿體之聚矽陰離子長度隨齡期增而有增加之趨勢，且較純矽酸三鈣漿體為長。對90天齡期抗壓強度發展而言，取代量10、20%之洗滌灰系熔渣水泥漿體可超越OPC 1?7 MPa；而底灰系熔渣水泥漿體則可與OPC之抗壓強度發展相當(差值<0.5MPa)。由MIP與膠體空間比分析結果得知，調質熔渣水泥漿體水化產物隨齡期增加而逐漸生成填充孔隙，使總孔隙體積與毛孔體積均逐漸減少，而膠孔則隨齡期增加，顯示熔渣有助於熔渣水泥漿體之緻密化。由XRD及DTA之物種分析得知，熔渣水泥漿體與OPC之水化產物主要為Ca(OH)2、C-S-H及C-A-H，並無明顯差異。TG分析所得結果顯示，熔渣可與Ca(OH)2進行卜作嵐反應，而形成C-S-H膠體或C-A-H鹽類。由NMR分析發現，熔渣水泥漿體之水化程度增加趨勢較純水泥漿體顯著；而聚矽陰離子長度則隨齡期而增加，至齡期90天其值皆大於純水泥漿體，顯示熔渣晚期因卜作嵐反應有助於熔渣水泥漿體內部矽酸鹽類之聚合。以SEM可觀察得熔渣表面與Ca(OH)2進行卜作嵐反應而形成C-S-H膠體，並逐漸成長相互接觸交織成網狀結構，進而提升熔渣水泥漿體之晚期強度。綜合上述結果，熔融處理可將都市垃圾焚化灰渣無害化，且所得熔渣具有材料化之潛力。 This study investigated the pozzolanic activity and the feasibility of using municipal solid waste incinerator (MSWI) ash slag in blended cement. Different replacement ratios were used. The experiments were divided into four parts: (1) the slag was characterized by melting the MSWI ash at 1400oC for 30 minutes; (2) the blended cement pastes were prepared using 1400oC-MSWI fly ash slag at replacement ratios ranging from 10 ~ 40%, with a W/B ratio ranging from 0.29 ~ 0.55, and then were analyzed for their pozzolanic activity at different ages; (3) an assessment was made of the pozzolanic reactions in C3S, C2S and C3A samples with the incorporation of MSWI fly ash slag, with blend ratio ranging from 20% to 40%, at various curing ages; and (4) the pozzolonic reactions and engineering properties of municipal solid waste incinerator ash modified slag blended cements (SBC) with various replacement ratios were monitored. The results indicated that the slag contained 27~34% CaO, 29~39% SiO2, and 8~23% Al2O3, and approximately 47~67% non-calcium compounds, thus meeting the ASTM C grade for fly ash, which is similar to that of blast furnace slag. The early unconfined compressive strength (UCS) of the SBC pastes decreased with an increasing replacement ratio and water/cement ratio, whereas the later UCS increased, showing the pozzolanic nature of the pulverized fly ash slag. The later UCS of the SBC paste samples, with less than a 20% replacement, outperformed that of ordinary Portland cement (OPC), indicating that the pozzolanic nature of the pulverized slag increased the later strength. However, the later strength decreased as the increasing replacement ratio was increased from 20% up to 40%. Moreover, the pore volume (<100 Angstrom) of the calcium silicate hydrate (C-S-H) gel that formed during hydration also increased with curing ages, suggesting that active non-crystalline ions in the slag such as Si and Al, could react with Ca(OH)2 to form C-S-H gel, resulting in the filling in the pore spaces, thus increasing the later strength. The results showed that a lower UCS was observed in C3S and C2S samples with the incorporation of MSWI fly ash slag, possibly due to the partial replacement of the mineral constituents by less active slag. In general, the incorporation of slag into C3S, decreased the initial hydration reaction but increased the pozzolanic reactions in later stages by consuming Ca(OH)2 to form CSH and CAH. This was indicated by the DTA results, which showed a delayed transformation of C3A from C4AH13 to C3AH6. Moreover, the hydration degree and the average length of C-S-H (i.e., the number of Si in linear poly silicate anions in C-S-H gel, the Psi), as determined by applying nuclear magnetic resonance (NMR) techniques, also indicated a delayed initial hydration and an enhanced later pozzolanic reaction. In the C3S-slag paste, the Psi value increased with increasing curing age compared with that of the C3S paste. The results of x-ray powder diffractometer (XRPD) revealed that the pozzolanic reaction in the C3S-slag paste was mainly affected by the Si2+ and Al3+ released by the slag. On the other hand, the incorporation of slag delayed the initial hydration of C3A in C3A-slag paste, and also decreased the formation of ettrigite (AFt) and monosulfoaluminate (AFm) in C3A-gypsum-slag paste. The 90-day compressive strength developed by SBC pastes with a 10% and 20% cement slag replacement generated from the modification of scrubber ash, outperformed that of OPC by 1-7 MPa, whereas the slags generated from the modified bottom ash series were comparable to OPC, with a difference of less than 0.5 MPa. From the pore size distribution, as shown by the MIP results, it was found that, with increasing curing ages, the number of gel pores increased and the total porosity and the number of capillary pores decreased — a result that shows that hydrates had filled the pores. XRPD and DTA species analyses indicated that the hydrates in SBC pastes were mainly Ca(OH)2, the C-S-H gel, and C-A-H salts, like those found in OPC paste. TG analysis also indicated that the slag reacted with Ca(OH)2 to form C-S-H and C-A-H. The average length (in terms of the number of Si molecules) of linear polysilicate anions in C-S-H gel, as determined by NMR, indicated an increase in all SBC pastes with increasing curing age, which outperformed that of OPC at 90 days. The generation of C-S-H gel, with intersections forming a network structure, as observed by SEM, from the surface reaction with Ca(OH)2, also led to the later development of strength in SBC pastes enhanced by the slag. It can be concluded from the study results that MSWI ash can be modified and processed by melting to recover reactive pozzolanic slag, which may then be used in SBC to partially replace cement.
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