下水污泥灰發泡混凝土之輕質化與隔熱特性研究; Investigating the lightweight characterization and heat-insulating efficiency of foaming concrete made of sewage sludge ash

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题名:	下水污泥灰發泡混凝土之輕質化與隔熱特性研究;Investigating the lightweight characterization and heat-insulating efficiency of foaming concrete made of sewage sludge ash
作者:	鄭欽仁;Chin-Jen Chang
贡献者:	環境工程研究所
关键词:	下水污泥灰;金屬發泡劑;發泡混凝土;熱傳導率;lightweight concrete;metallic foaming agent;sewage sludge ash;heat transfer
日期:	2002-05-07
上传时间:	2009-09-21 12:14:53 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	摘要台灣地區因衛生下水道平均普及率僅6.5%，政府乃積極提出「污水下水道發展方案」，預計2003年將日產180,000m3污泥，如此龐大污泥的處理與處置，將形成環保上棘手且迫切的問題。本研究基於廢棄物資源化之目的，以八里初級污水處理廠與台北市民生二級污水處理廠之下水污泥焚化灰渣為主體材料，添加水泥及金屬發泡劑產生發泡反應，以拌製污泥灰發泡混凝土。針對材料之物理性質及化學組成，探討污泥灰料源對於發泡混凝土之產製配比、輕質化與熱傳等工程性能，以及微觀組織之影響；並以鋁粉與廢五金粉做為金屬發泡劑，比較二者對發泡特性之影響。最後，綜合評估污泥灰發泡混凝土之反應機制、輕質化與隔熱性能受配比變數之影響程度與關聯性，並提出使用策略與建議。由研究結果顯示，就高分子系污泥而言，初級廠污泥之灰份高於二級廠污泥，而其含水率則呈相反，故初級廠污泥的灰渣製備較具經濟性；而初級廠及二級廠之污泥灰比表面積分別為4,657 m2/kg及10,193 m2/kg，污泥灰細度對漿體之工作性產生顯著影響；就污泥灰之化學組成而言，初級廠污泥灰之SiO2含量高於二級廠約19.82%，而P2O5含量前者低於後者約11.78%，其餘化學成分相近；初級廠污泥灰之卜作嵐活性高於二級廠污泥灰；污泥灰發泡混凝土之體比重低於1.2以下，符合輕質化之要求；而污泥灰發泡混凝土藉金屬發泡劑之發泡產氫反應，形成以大於1μm為主之多孔結構體，初級廠與二級廠之孔隙率分別為51.28 ~71.17%及53.62 ~72.54%，高孔隙率造成低熱傳導率，其熱傳導率分別為0.0880 ~0.2507 W/m-oK及0.0763 ~0.1510 W/m-oK。因此，就輕質化與隔熱性能而言，初級廠污泥灰劣於二級廠；但就經濟性而言，初級廠污泥灰優於二級廠。 Abstract As the current percentage of the national population served by a sewer system in Taiwan is as low as 6.5%, a "National Development Sewer System Plan" has been launched, aimed at pushing forward sewer system development on the island. Pursuant to this development plan, it is estimated that by the years 2003 and 2009, the national average served by sewer systems should reach 15% and 33%, respectively, generating an estimated 180,000 m3/day and 400,000 m3/day of sewage sludge to be disposed of, which is expected to have significant impact on the environment. From the viewpoint of substantial waste management, zero-discharge for MSW incinerators, and the add value of the recovery of waste for green products, the resource and recovery of sewage sludge ash, for producing lightweight foaming concrete,should be a feasible and novel alternative. This study investigates the feasibility of producing foaming concrete as an insulator, using sewage sludge ash as a main component, and evaluates its heat-insulating efficiency. The work focuses on the characterization of the sewage sludge ash, the mix design, the bloating mechanism, and the heat-transfer properties of the sludge-ash-based insulator. Sewage sludge cakes were collected from the Bali and Minsheng sewage treatment plants (STPs) respectively, representing a typical primary and a secondary STP. The sludge cake was first incinerated at 900℃ to produce ash. Aluminum powder was used as a foaming agent, combined with pulverized scrap ( more than 90% Aluminum) small amount of OPC was used as a binder. The characterization of the main components of the sludge ash indicate that, for sludge cakes with polymers, the ash content of the primary sludge ash(PSA) was higher than that of the secondary sludge ash(SSA), whereas the relationship was reversed for the water content. The specific surface areas of the PSA and SSA were 4,657 m2/kg and 10,193 m2/kg respectively, showing the greater fineness of the effect of sludge ash on the workability of the pastes. In general, the PSA has higher SiO2 content but lower P2O5 content than the SSA, whereas the other components were about equal to each other. Furthermore, the PSA had higher pozzolanic activity than did the SSA. These results suggest the greater economic feasibility of recycling PSA rather than SSA. Various mix designs were tested showing that the sludge-ash-based foaming concrete had a specific gravity of less than 1.2, meeting the ASTM for lightweight concrete(LC). The foaming mechanism was mainly due to hydrogen gas being by the reaction of aluminum with hydroxyl radicals, generated by the hydration of the cement. The cellular structure was solely composed of micro pores about 1μm in diameter. LC samples prepared according to the mix design adopted in this study showed a porosity distribution ranging from 51% to 71% for PSA-based LC, and 54% to 63% for SSA-based LC. The higher porosity of the latter resulted in a lower heat transfer(0.0880-0.2507 W/m-oK) compared to that of the former(0.0763-0.1510 W/m-oK). Therefore it is suggested that the SSA-based LC should outperform PSA-based LC in heat-insulating efficiency. It can be concluded, from the results of this study, that PSA is more economically feasible than SSA, whereas the SSA based LC showed better heat-insulating performance than did PSA- based LC.
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