This research aimed to find an eco-friendly way to neutralize water recovered from ready-mixed concrete by dissolving carbon dioxide in it, and to verify the potential use of such water for mixing concrete. Carbon dioxide was injected using nanobubble technology into recovered water, and the optimized conditions for dissolution were established by analyzing the carbon dioxide concentration in the water and measuring pH over time. Mortar was manufactured using this recovered water following carbon dioxide nanobubbles treatment, and measurements of compressive strength and thermogravimetric analysis (TGA) were conducted to verify the formation of calcium carbonate. 2,464 mg/L of carbon dioxide was dissolved in the recovered water, and the pH was measured to be 6.34. The compressive strength of the manufactured mortar was found to be 32.02 % stronger than mortar manufactured with normal tap water. According to the thermogravimetric analysis results, the amount of calcium hydroxide produced in the mortar manufactured with recovered water from ready-mixed concrete was 8.10 %, and the production amount of calcium carbonate was 6.49 %. This means that the amount of calcium carbonate produced was greater than that in mortar manufactured with normal tap water, as well as tap water containing nanobubble carbon dioxide. The carbon dioxide was stably dissolved in water recovered from ready-mixed concrete using nanobubbles, enabling environmentally friendly neutralization without the use of chemicals. Also, when the recovered water from ready-mixed concrete containing dissolved carbon dioxide was used for mixing concrete, it was determined that the carbonation reaction influenced the formation of calcium carbonate, which contributed to the improvement in concrete strength.

Abstract
1. 서 론
2. 실험 방법
    2.1. 실험 재료 및 장치
    2.2. 레미콘 회수수 내 나노버블 기술을 활용한 이산화탄소 용해 방법
    2.3. 이산화탄소가 용해된 레미콘 회수수의 콘크리트배합수 활용
3. 결과 및 고찰
    3.1. 레미콘 회수수 내 이산화탄소 농도 결과
    3.2. 압축강도 측정 결과
    3.3. 열중량 분석 결과
4. 결 론
Acknowledgement
References
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• 김종규(신한대학교 에너지공학과) | Jong Kyu Kim (Department of Energy Engineering, Shinhan University, Uijeongbu 11644, Republic of Korea) Corresponding author