| 摘要: | 放射性廢棄物處置場混凝土涵蓋範圍很廣，在水泥材料的使用非常重要，當地下水滲透到處置坑道封塞之混凝土時，普通卜特蘭水泥會釋放高鹼性之孔隙溶液其pH值約在12~13，孔隙水滲出後遭遇緩衝材料，將使緩衝材料中具回脹能力的主要成分蒙脫石溶解，蒙脫石溶解速率隨pH提高而漸增。因此使用低鹼性膠結材經由卜作嵐反應消耗水泥水化產生之氫氧化鈣(CH)，藉以降低pH值，以確保緩衝材料之安全功能。
本研究以低鹼性膠結材矽灰及飛灰取代部分水泥進行膠結漿體、砂漿及混凝土等相同膠結配比之微觀特性、工程性質及耐久性等試驗，並藉由文獻回顧找出水泥混凝土pH值的標準檢測方法，建立實驗室中檢測水泥混凝土pH值的標準方法與能力，同時也探討使用不同礦物摻料矽灰及飛灰取代水泥，對降低水泥漿體孔隙溶液pH值之成效。
結果顯示，在水泥中加入卜作嵐材料透過低鹼性膠結材的摻配，會進行卜作嵐反應消耗氫氧化鈣，並形成C-S-H膠體將有效降低孔隙溶液pH值。水泥混凝土的pH值量測方法選用移地進出法(ESL)，經由不同環境檢測後，顯示ESL法具有穩定性及重複性。本研究發現要達到低鹼性封塞混凝土性質的要求，需藉由調整膠結性材料的用量，當矽灰取代量達到40 %以上時，砂漿及混凝土試體在90天齡期的pH值可降至11以下，且抗壓強度亦可符合封塞混凝土的要求。耐久性方面，矽灰取代水泥重量越多時，抵抗氯離子穿透能力越佳。但矽灰比表面積極大，容易吸水，加入過多矽灰對工作性影響甚大，需添加少量強塑劑以改善其新拌性質。另一方面，因矽灰之材料成本較高，如以飛灰取代部分水泥可降低成本並改善工作性，因此在工程性質及經濟性考量下，以矽灰及飛灰分別取代水泥重量達35%及20%的膠結材料配比，可達到低鹼性混凝土封塞的品質需求。
;Due to the wide range of concrete in radioactive waste disposal sites, the use of cement materials is very important, especially when the groundwater penetrates into the concrete. The Ordinary Portland Cement (OPC) releases the pore fluids of the pH 12-13. In the high pH environment, the pore water leakage after the encounter buffer material, it will make the buffer material with the expansion of the main components of montmorillonite dissolution rate which increases the pH. Therefore, the use of low-alkali cement material after the pozzolanic reaction, the consumption of calcium hydroxide solution (CH), will reduce the pH value that ensure the buffer material are safety.
In this study, the micro-characteristics, engineering properties and durability of the same cementing ratio of cement paste, mortar and concrete were replaced by low pH cement silica and fly ash. According to the references, the measurement of pH method are found that Ex-Situ leaching method is established for laboratory testing whichis easily and capabilities. To explore the use of different mineral admixture of silica fume and fly ash replace of cement, it will reduce the pore fluids of the pH value effectively.
The results show that the addition of Pozzolan material to the cement can reduce the pH value of the pore solution by adding silica fume. To achieve the requirements of the concrete plug sealing, it needs to control the amount of cementitious materials, when 40% silica fume replace of cement, the pH of mortar and concrete samples in the 90-day is lower than 11. Because of the silica fume is more expensive than fly ash and when the more silica fume is added, the workability is in bad condition, it needs add some plasticizer to improve the workability. Therefore, the silica fume and fly ash were replaced by cement weight 35 % and 20% respectively, it can achieve the requirements of quality of low pH concrete plug sealing. |
