副產石灰配合再生粒料製作無水泥混凝土可行性評估; Use of CFB bed ash and recycled aggregates in making non-portland cement concrete

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Title:	副產石灰配合再生粒料製作無水泥混凝土可行性評估;Use of CFB bed ash and recycled aggregates in making non-portland cement concrete
Authors:	蕭定群;Ting-chun Shaw
Contributors:	土木工程研究所
Keywords:	CFB副產石灰;抗壓強度;凝結時間;CFB ash;compressive strength;setting time
Date:	2010-07-14
Issue Date:	2010-12-08 13:33:12 (UTC+8)
Publisher:	國立中央大學
Abstract:	副產石灰為循環式流體化床發電鍋爐(Circulating Fluidized Bed Boiler，簡稱CFB)脫硫製程下，所產生之副產物，業經證實為一可行之新興混凝土膠結材料。本研究係利用副產石灰中之鹼性物質，激發水淬爐石粉，使其進行卜作嵐反應，一方面製作砂漿塊及砂漿棒試體，進行抗壓強度、體積穩定性及耐久性試驗；另一方面，搭配經資源化處理之營建廢棄物廢棄混凝土石與工業廢棄物爐碴砂，分別取代天然粗、細粒料，進行混凝土拌合試驗，最後嘗試加入化學摻料以加速其凝結時間，藉以評估副產石灰配合再生粒料製做無水泥綠色混凝土之可行性。實驗結果顯示，抗壓強度試驗中，使用膠結材重量20%之副產石灰與80 %之爐石粉，抗壓強度最佳，且均可符合ASTM C150對水泥墁料之強度要求；乾縮試驗方面，使用適量之副產石灰，可降低大量使用爐石粉所產生之乾縮；而針對高含硫量可能引致之膨脹問題，則應限制副產石灰使用量(≦17%)，使試體膨脹量符合規範要求；耐久性試驗結果則顯示副產石灰-爐石膠結系統具有抵抗硫酸鹽侵蝕之能力，維持試體體積穩定。混凝土配合設計試驗結果顯示，在良好之工作性下，使用爐碴砂部分取代天然細粒料抗壓效果良好；使用廢棄混凝土塊取代粗粒料之配比，對混凝土強度則會產生一定程度的影響。凝結時間試驗中，運用鹼活化技術，加入矽酸鈉與氫氧化鈉，可有效改善副產石灰-爐石之漿體時間，但在良好工作性下，使用大量拌合水，使得混凝土凝結時間不如預期。評估各項實驗結果，副產石灰配合再生粒料製作無水泥混凝土係可行的。 Circulating Fluidized Bed boiler (CFB) bed ash is the by-product of the CFB desulfurization process, and has been proved to be a potential material for replacement of portland cement as a cementitious material. In this study, CFB bed ash was used as an alkali substances to activate the pozzolanic reaction of blast furnace slag such that the activated slag can be used as cementitious materials in making concrete. Mortar specimens made with various proportions of CFB bed ash and slag were tested for their compressive strength, volume stability and durability. Also, recycled concrete aggregate (RCA) and industrial waste slag sand were evaluated to replace natural coarse and fine aggregates, respectively, for the possibility of producing a non-portland cement concrete. Test results indicate that the combination of 20% CFB ash and 80% slag produces adequate compressive strength satisfying the ASTM C 150 requirements on strength of Portland cement. On the other hand, it is suggested that the amount of CFB used be less than 20%, so as to avoid generating over-expansion due to the high content of SO3 in CFB bed ash. In addition, it was found that the incorporation of CFB ash helps reducing the shrinkage resulting from the high amount of slag as cementing material. And the combination exhibits excellent sulfate-resisting capability also. Concrete mixes proportioned using 25% electric-arc furnace slag in replacement of fine aggregates showed increases in compressive strength, while the use of 50% RCA in replacement of natural coarse aggregate showed reduced compressive strength. The shortcoming of using CFB ash in activating slag as cementitious material is that it caused delayed setting time. Various chemical admixtures were tested for improving the setting time of the mixes in question. It was found that, at an appropriate amount, the use of alkali activator would speed up the setting time of slag-CFB bed ash cementing system. To conclude, the combination of slag-CFB bed ash along with recycled aggregates shows great potential of non-portland cement green concrete.
Appears in Collections:	[Graduate Institute of Civil Engineering] Electronic Thesis & Dissertation

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