增進混凝土碳封存技術之研究

Abstract

隨著科技日新月異，世界各國的二氧化碳排放量也跟著急速上升，所造成的全球暖化問題也成為大家關注的焦點，而二氧化碳排放來源主要是由工業、能源及運輸占大多數，世界各地的科學家都在努力減少大氣中的二氧化碳濃度，因此近幾十年出現了許多二氧化碳封存技術，其中混凝土中有許多成分是可以跟二氧化碳產生反應，若能利用混凝土將二氧化碳封存，並在不對力學性能造成負面影響情況下，或許可以成為一個有潛力的碳封存方式。 本研究主要是利用二氧化碳養護的方式來封存二氧化碳，將齡期一天的水泥砂漿試體置入高壓的二氧化碳環境進行碳化反應，但是早齡期水泥砂漿試體中的孔隙都充滿水分，孔隙中的水分會阻礙二氧化碳進入試體中，因此在進行碳化反應前，會先將試體放在相對濕度50%左右的環境，主要目的就是要將孔隙中水分散失，本研究將此步驟稱為預處理(pre-conditioning)。在整個二氧化碳養護過程中，將設計不同水灰比、不同預處理時間、不同碳化時間和不同的二氧化碳壓力，在二氧化碳養護結束後，進行單軸抗壓試驗，比較碳化反應對硬固試體的力學性質影響，另外，還會進行二氧化碳吸收量的計算，比較不同參數對水泥吸收二氧化碳的影響，根據二氧化碳養護結束當下試體的抗壓強度及二氧化碳吸收量，得出最佳的二氧化碳養護流程，最後會在經過二氧化碳養護的試體到達齡期7天、28天時，會進行抗壓試驗，來觀察經過二氧化碳養護的試體後續強度的發展。 根據試驗結果，可以計算出二氧化碳養護的碳封存效果及對抗壓強度的影響，並找出最佳的二氧化碳養護方法，最後針對二氧化碳跟水泥反應時的化學機理進行探討。

With the advance of technology, the global carbon dioxide emission increase rapidly, and global warning has grabbed the public’s attentions. As for source of carbon dioxide emission, industry, energy and transportation are the majority. In order to solve the issue, scientists work hard to reduce the concentration of carbon dioxide in the atmosphere. Therefore, the presence of carbon capture and storage technology has evoked within the decades where many elements in the concrete can react with carbon dioxide. The method of storing carbon dioxide in the concrete could be promising if it can maintain good compression. This research looks into how carbon curing stores carbon dioxide, putting cement mortar specimen in the high-pressure environment for one-day age. However, pores in cement mortar specimen are fully filled with water in the early age, which blocks the diffusion of carbon dioxide into the specimen. Therefore, a process, namely pre-conditioning, will be adopted by placing specimen in the environment with RH 50% before exercising carbonization reaction to get rid of water in pores. During the process of carbon curing, several conditions will be set. For instance, different water cement ratio, pre-conditioning duration, carbonization duration and pressure. After carbon curing, compression test will be conducted. Additionally, the amount of carbon dioxide absorbed by specimen under different conditions will be calculated and find out the optimal carbon curing according to experiment results. Finally, specimen after carbon curing will be conducted compression tests to observe the compression strength development of post carbon curing specimen in 7-day and 28-day age. Based on the experiment results, the effectiveness for compression and carbon storage can be calculated, and find out the optimal carbon curing method. Lastly, reaction mechanism of carbon dioxide and cement will be discussed.