| 摘要: | 本研究目的係利用廢棄污泥做為水泥生料及卜作嵐材料，探討製造水泥系材料之可行性。利用大理石污泥、下水污泥、淨水污泥及轉爐礦泥等材料，替代水泥原料的實驗結果發現，大理石污泥可以替代50%的石灰石，並且其他三種污泥可以完全取代其他傳統的水泥原料，用以製造環保水泥。各環保水泥中都可以發現波特蘭水泥的主要成份。經過28天的養護，由抗壓強度 (Sc) 及微孔隙結構試驗結果，證實水化反應的產生與驗證環保水泥之實用性。研究並發現環保水泥之抗壓強度與微孔隙體積(Pv)存在著一線性關係，關係式為Sc = 178−461Pv (相關係數，R2 = 0.96)。 將有卜作嵐特性之廢棄污泥，如下水污泥灰渣、爐石及飛灰，透過不同比例之組合，並摻拌取代50%水泥，經過56天養護期，水泥砂漿之抗壓強度可以達到傳統水泥砂漿的93.7%，因為爐石有較高的強度活性指數(SAI)且含有大量氧化鈣，與下水污泥灰渣和飛灰組合摻拌時，可以增加下水污泥灰渣和飛灰的卜作嵐活性，並且形成可填充砂漿中毛細孔隙的矽酸鈣水合物膠體，可增加砂漿的抗壓強度。另一方面，實驗結果發現添加鈣離子改良的下水污泥灰渣與爐石取代70%水泥時，在56天養護期之下，其砂漿的抗壓強度可以達到傳統水泥砂漿的92.4%，證實可利用添加鈣離子來增進下水污泥灰渣的卜作嵐反應特性。 環保水泥是利用廢棄污泥做為水泥原料，如果不考慮處置廢棄污泥所帶來的環境益處，由於在水泥窯煅燒過程中，其能源消耗及污染排放上並未減少，且其燒失量大於普通水泥，比較相同重量水泥的情境下，其環境衝擊高於傳統水泥及混合水泥。而混合水泥由於加入廢棄污泥作為卜作嵐材料，其環境衝擊只有傳統水泥的52.7%。而LCA結果顯示，水泥製造基本上是一個高耗資源及能源的產業。因為水泥製造會使用大量的礦產資源及開採的能源，IMPCAT 2002+衝擊評估方法將資源開採所產生的衝擊納入進行評估，相較於Eco-indicator 95方法，應是較適合水泥製造業之環境衝擊評估方法。 In this study, waste sludges were used as raw cement materials or pozzolans to produce the cementitious materials. The usage of marble sludge, sewage sludge, drinking water treatment plant sludge, and basic oxygen furnace sludge as replacements for the raw cement materials was feasible. The results were also found that marble sludge could replace up to 50% of the limestone and other materials could serve as entire substitutions for the traditional raw materials in cement production. The major components of Portland cement were all found in eco-cement (EC) clinkers. The compressive strength (Sc) and microstructural evaluations conducted at 28 days revealed the hydration reaction and usefulness of EC. It was observed that the Sc data correlated linearly with the pore volume (Pv) data at 28 days. The proposed model equation could be represented as Sc = 178−461Pv (correlation coefficient, R2 = 0.96). Waste materials with pozzolanic characteristics, such as sewage sludge ash (SSA), coal combustion fly ash (FA), and granulated blast furnace slag (GBS), were reused partially as cement replacements for making blended cement mortars. The results revealed that with dual replacement of cement by SSA and GBS and triple replacement by SSA, FA, and GBS at 50% of total cement replacement, the Sc of the blended cement mortars at 56 days was 93.7% and 92.9% of the control cement mortar, respectively. GBS had the highest strength activity index value and could produce large amounts of CaO to enhance the pozzolanic activity of SSA/FA, and form calcium silicate hydrate gels to fill the capillary pores of the cement mortar. In the cement mortar with modified SSA and GBS at 70% of total cement replacement, the Sc at 56 days was 92.4% of the control mortar. These results confirm the assumption that modifying the content of calcium in SSA further increased its pozzolanic reaction. Due to the fact that EC was used waste sludges in the kiln feed, there was no real reduction in emissions and energy consumption in calcination, and the ignition loss was greater than ordinary cement. Therefore, the impact score generated by the EC was higher than ordinary and blended cement at the equal amount as a result of excluding the environmental benefit of reusing the waste sludges that have the need for final disposal. Incidentally, blended cement could effectively reduce the total environment impact score and the score was 52.7% of that of ordinary cement. Results from life cycle assessment (LCA) methods also indicated that cement manufacturing in Taiwan was high-resource-consumption and energy-depletion industry. However, Eco-indicator 95 method excluded the impact assessment of consumption of energy and resource, but the impact of mineral extraction was taken into consideration by IMPACT 2002+ method. Consequently, IMPACT 2002+ should be a more applicable LCA method for the cement industry because the manufacture of cement always consumes a massive amount of raw material and energy for mineral extraction. |
