CFBC飛灰作為鹼激發劑與標準之符合度及混凝土性質研究

Abstract

隨著人類環保意識之增強與材料技術之進步，對社會經濟的快速發展帶來相當大的影響，本研究之CFBC飛灰係由煉油廠進行高溫氧化循環式流體化床(Circulating Fluidized Bed，簡稱CFB)製程時，以石油膠為燃料，混合石灰石進行排煙脫硫所產生之資源化產物，具優異之材料特性，國內外已開出許多資源化產品，但在混凝土材料上之研究與應用較不成熟，過度的f-CaO與SO3在水化反應下會造成體積膨脹，不利於耐久性。然而，若能使用適量並且符合標準之要求，則具有應用於混凝土材料上之潛力。 然而CFBC飛灰之添加量存在其最佳使用範圍。由於目前國家標準15286已有類似之規定可資參考，故本研究以CNS 15286為主軸，第一部分為ASTM C821符合度測試與CNS 15286符合度測試兩階段，指在針對控制CFBC飛灰添加於卜特蘭高爐水泥配比中是否可作為鹼激發劑使用，並找出其適當添加量。第二部分為應用於混凝土材料上，於不同相對濕度養護環境下進行工作性質、力學性質、體積穩定性與耐久性質等研究。 由符合度測試結果得知CFBC飛灰具有鹼激發劑之能力，並適用於混合水泥-卜特蘭高爐水泥配比中，最佳添加量為10~20%，因具有膨脹與緩凝等材料特性，故水泥添加量建議需至少10 %。由混凝土試驗得知，添加CFBC飛灰之配比因材料特性導致工作性較差，在力學性質上皆與CC控制組相差不遠，體積穩定性不存在膨脹所造成之耐久性問題，且在較低相對濕度養護環境下亦有抑制收縮之效果，耐久性質試驗更發現添加CFBC飛灰之配比表現皆優於CC控制組甚多，且由經濟性分析得知CFBC飛灰之配比水泥添加量至多為20 %，材料成本僅約為CC控制組的70~75%，由此可見若能適當的控制添加量，並針對材料特性找合適之使用環境，充分合理的利用CFBC飛灰不僅能為社會帶來經濟性亦能達到節能減碳、永續發展之目標。

CFBC is a by-product of circulating fluidized bed to de-sulfurize the petroleum coke. There are already many applications of CFBC but not in concrete. Excessive amount of f-CaO will react with SO3 and cause expansion, which is not sustainable. However, if a suitable amount of CFBC can be used if relevant standard requirements are met. CNS 15286 Blended cement is the standard used to justify the suitability of CFBC and ASTM C 821 conformity test is also used. The CFBC to be used as alkali activator is therefore tested to find the optimum amount. In addition, the curing regime, such as RH, is also investigated to determine the mechanical properties, volume stability and durability. From the conformity test, it is justified that CFBC can be used as alkali activator in blended cement. The optimum amount is 10-20% of total cementitious material. CFBC also exhibits expansion and set retarding, it is recommended to use at least 10% Portland cement. From the test results, it can be found that when CFBC is used, the workability is reduced, the mechanical properties are comparable to the conventional concrete with same w/c but without CFBC, and better durability. From cost analysis, if 20% Portland cement is used with slag and CFBC, the cost can be reduced by 25-30% than conventional concrete. The CFBC can be used to replace cement economically, safely, and more sustainability.