급속탄산화 시험기에 의한 플라이애시 콘크리트의 탄산화 특성 연구

유성원(Yoo Sung Won),방기성(Bang Gi Sung),정상화(Jung Sang-Hwa),장승필(Chang Sung Pil) 대한토목학회 2007 대한토목학회논문집 A Vol.27 No.4A

콘크리트의 탄산화 과정은 철근의 부식을 유발하는 주요 요인이지만 탄산화 과정이 시간을 두고 느리게 진행되기 때문에 이에 대한 실험적인 연구 자료는 부족한 실정이다. 이에 따라 본 연구에서는 최근 개발된 진공용기를 활용 급속촉진탄산화 실험 장치를 이용하여 기존의 실험장치보다 실험기간을 단축시킨 포틀랜드시멘트 및 플라이애시 콘크리트에 대한 촉진탄산화 실험을 수행하였다. 실험결과 물-시멘트비가 40%인 경우와 비교하여 물-시멘트비가 45%에서 60%까지 증가할 때 탄산화깊이도 103%에서 138%까지 증가하였다. 예측모델에 의한 탄산화깊이 예측값은 실험에 의한 결과보다 크게 나타났으며, 물-시멘트비가 증가할수록 차이가 커지는 결과를 나타냈다. 또한, 기존의 연구결과와 유사하게 플라이애시 혼입량이 증가할수록 탄산화깊이가 급격히 증가하는 결과를 나타내었다. 급속촉진탄산화 실험체계를 통해서 기존 촉진탄산화 실험과 비교하여 짧은 기간에 유용한 실험결과를 얻을 수 있었으며, 본 연구에서 수행한 실험자료와 향후 지속적인 데이터의 축적을 통해 국내 콘크리트 구조물에서의 탄산화 과정을 밝히는데 많은 기여를 할 수 있을 것으로 기대된다. Carbonation is one of the most important factors of the concrete deterioration resulting in the steel corrosion in concrete. Nevertheless, the experimental data for the study of the concrete carbonation have not been sufficiently accumulated because the carbonation of concrete is a long-term phenomenon. In this study, the newly-developed rapid carbonation test by the usage of the vacuum equipment has been used to observe the carbonation behaviors of concretes made of portland cement and of fly-ash cement. Experimental results showed that concretes with 0.45 and 0.6 w/c had the carbonation depth of 103% and 138%, respectively, comparing to that of 0.4 w/c. The carbonation depths calculated by an analytical model were deeper than the experimental results and the deviations increased with the increase of the water to cement ratio. It was also observed that the carbonation depth rapidly increased with the increase of fly-ash replacement. Consequently, the rapid carbonation test provided experimental results in a shorter time than the conventional carbonation tests, and it is expected that these experimental data and the further study by the new rapid carbonation test will contribute to the future studies of concrete carbonation.

광물탄산화 핵심기술과 상용화 전략

이승우 한국에너지기후변화학회 2023 에너지기후변화학회지 Vol.18 No.2

Carbon Capture & Utilization (CCU) is a technology that has the effect of reducing CO2 by producing the conversion products of carbon dioxide and replacing commercial products used in existing industries with the conversion products. CCU technology can be largely divided into chemical conversion, biological conversion, and mineral carbonation. Mineral carbonation starts with the weathering of natural minerals, and recently, alkaline industrial by-products are used as a source of cations. Mineral carbonation can be largely divided into a direct carbonation method in which carbon dioxide and industrial by-products are reacted together, and an indirect carbonation method using an extraction solvent on calcium or magnesium. In this paper, the efforts of the international community, including Republic of Korea, on climate change and greenhouse gas reduction, and the concepts and differences between CCU and CCS (Carbon Capture & Storage) were examined. In addition, the concept and method of mineral carbonation technology was explained and the domestic and foreign trends for each key technology were examined. In addition, the requirements for commercialization of mineral carbonation technology were reviewed from technical and institutional aspects.

Effluent Recycling of Liquid Carbonation with Carbon Dioxide Fixation using Industrial by-products

( Cheol Jin Jeong ),( Bumui Hong ),( Jin-won Park ),( Changsik Choi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2015 한국폐기물자원순환학회 춘계학술발표논문집 Vol.2015 No.-

Mineral carbonation, the return technology of Carbon dioxide into the Nature as a generating source, has been studied by advanced countries. Industrial by-products can be used as economical resource for mineral carbonation. This study is intended as an investigation of effluent recycling of liquid carbonation with carbon dioxide fixation using industrial by-products. The nitrogen and carbon dioxide was used by mixing the same as the exhaust gas concentration 15vol%. Carbon dioxide absorbent was used as Mono Ethanol Amine (MEA) concentration of 5~30wt% and then concentration of carbon dioxide absorption were analyzed. After carbonation reaction, Concentration of dissolved inorganic cations and conversion of carbonation were analyzed by ion chromatography, thermogravimetric, x-ray diffraction, scanning electron microscope(SEM). Effluent was recycled MEA and water using RO system. These results Confirmed potential of CO2 reduction and Utilization of carbonation using industrial by-products.

Novel carbon capture and utilization (CCUS) method using electrolysis of concentrated seawater and accelerated mineral carbonation

( Sangmin Lee ),( Soobin Joo ),( Jihyun Chae ),( Heeseong Hwang ) 한국폐기물자원순환학회 2022 ISSE 초록집 Vol.2022 No.-

According to the IPCC (IPCC Special Report, 2018), atmospheric warming should be <2°C to avoid the most severe consequences associated with climate change. The obligation to reduce carbon by the 2050 Carbon Neutrality Declaration, added worldwide, is urgent. The Korean government is making efforts to achieve carbon neutrality by converting to eco-friendly energy and using various carbon capture methods. Among the current CO₂ sequestration methods, a mineral carbonation process requires less area than ocean storage or deep saline aquifer. However, mineral carbonation needs immense energy for mining and crushing ore to provide stable metal sources and alkaline solutions for fixing CO₂. On the other hand, concentrated seawater has various cations like Mg²⁺, Ca²⁺, and Na⁺, and it is not necessary for the pretreatment of ore or industry waste like waste concrete, slag, and asbestos. In this study, the concentrated seawater is electrolyzed by membrane electrolysis at low voltage to generate a strong alkali solution and hydrogen gas. The mineral carbonation reactor was supplied by the alkali byproduct of the electrolyzed seawater and a high concentration of alkaline earth metals. To find out operation conditions for optimum mineral carbonation, the types of electrode materials, the strength of applied current density, and the flow rate of an electrolyte were investigated. The pH behavior and CO₂ concentration were continuously monitored by a CO₂ sensor and the amount of CO₂ reduction was calculated by integrating the time-CO₂ graph. In addition, precipitated metal carbonates which are formed by Mg²⁺, Ca²⁺, and Na⁺ were analyzed by FE-SEM and EDAX for their crystal structure and morphology. An unexpected result is that precipitation occurred while electrolyzing the concentrated seawater without a CO₂ supply. This might be presumed to be Mg(OH)₂ according to FE-SEM and EDAX results. Thus, an additional step is necessary to solve the consumption of magnesium and alkalinity before mineral carbonation. This method can provide an economical carbon sequestration method that can overcome the drawbacks of classical mineral carbonation. This study proved the potential of CO₂ reduction and valuable precipitated metal carbonates like MgCO₃, CaCO₃, and NaHCO₃ by accelerated mineral carbonation.

항만콘크리트 구조물의 탄산화에 미치는 온도의 미세구조적 영향

한상훈(Han, Sang-Hun) 한국해안해양공학회 2010 한국해안해양공학회 논문집 Vol.22 No.4

탄산화에 미치는 온도의 영향에 대해서는 매우 상반된 2가지의 주장이 존재하는데, 온도증가는 탄산화 반응을 가속화시켜 탄산화 깊이를 증가시킨다는 주장과 탄산화 반응을 일으키는 최적의 온도조건이 있으며, 탄산화 깊이는 이러한 최적의 온도조건에서 가장 큰 값을 가진다는 주장이다. 일반적으로 탄산화는 시멘트 수화물 중 수산화칼슘과 이산화탄소의 화학반응으로 생성되는 것으로 알려져 왔고 많은 탄산화 연구들도 이에 집중되어 왔다. 그러나, 최근의 몇몇 연구에서는 수산화칼슘을 제외한 다른 시멘트 수화물도 탄산화 반응이 일어난다는 결과를 발표하고 있다. 본 연구에서는 온도의 탄산화에 미치는 영향을 파악하기 위하여 탄산화 온도에 따른 탄산화 깊이와 탄산화 반응물과 생성물에 대한 실험을 수행한다. 또한, 실험결과의 분석을 통하여 수산화칼슘이외의 수화생성물이 탄산화에 미치는 영향을 파악하고자 하였다. 탄산화 깊이는 페놀프탈레인 용액법으로 측정하였고, 탄산화 전후의 반응물과 생성물은 열중량분석기(Thermogravimetric analyzer)를 이용하여 측정하였다. 탄산화 온도가 20?C에서 30?C로 증가하면 탄산화 깊이가 크게 증가하였지만 온도가 30?C에서 40?C로 증가하면 탄산화 깊이가 거의 증가하지 않았다. 이것은 탄산화 반응에 대한 최적의 온도조건이 존재할 수 있다는 증거일 수 있다. 페놀프탈레인 용액법에 의한 탄산화 깊이는 수산화칼슘과 탄산칼슘의 양이 변화하여 교차하는 영역에 존재한다. 탄산화 온도 30?C와 40?C에서의 수산화칼슘 이외의 시멘트 수화물에 의해 생성된 탄산칼슘양은 온도가 증가하면 감소함을 관찰할 수 있었다. Some recent researches reported that high temperature rising decreases the carbonation depth of concrete, which is contrary to the previous research results. Carbonation has been known as a reaction between calcium hydroxide and carbon dioxide. But a few researches showed that the other cement hydrates as well as calcium hydroxide react with carbon dioxide. This paper investigates the influence of temperature on carbonation and the variation of Ca(OH)₂ and CaCO₃ by carbonation. In order to estimate the carbonation depth and the quantities of reactant and product of carbonation reaction, phenolphthalein testing and thermagravimetric analyzer test were conducted. The measurement of carbonation depth with temperature showed that the temperature increase from 20?C to 30?CC in carbonation environment makes the carbonation depth larger, but the increase from 30?C to 40?C has a small influence on the carbonation depth. Comparing calcium hydroxide and calcium carbonate with temperature, the quantity of CaCO₃ of specimen carbonated at 30?C is greater than that of specimen carbonated at 40?C and the quantity of Ca(OH)₂ of specimen carbonated at 30?C is similar to that of specimen carbonated at 40?C. This observation shows that there is the optimum temperature increasing carbonation depth and the optimum temperature is close to 30?C.

시멘트 풀을 이용한 CO₂ 포집과 탄산염광물의 생성에 관한 연구

최영훈 ( Young Hun Choi ),황진연 ( Jin Yeon Hwang ),이효민 ( Hyo Min Lee ),오지호 ( Ji Ho Oh ),이진현 ( Jin Hyun Lee ) 한국광물학회 2014 광물과 암석 (J.Miner.Soc.Korea) Vol.27 No.1

폐콘크리트 처리 시 발생하는 시멘트 미분은 CO₂ 포집을 위한 광물탄산화 재료로 활용할 수 있다. 이번 연구에서는 폐콘크리트를 활용한 CO2 포집을 위한 기초연구로 수화시멘트의 수성탄산화 방안과 탄산염광물 형성 특성에 대한 자료를 확보하고자 하였다. 실험을 위해 물 : 시멘트 비를 6 : 4로 하여 28일간 수중 경화하여 시멘트 풀을 제작하고, 첨가제(NaCl과 MgCl₂)를 활용한 용출실험과 두 종류의 수성탄산화(직접수성탄산화와 간접수성탄산화)실험을 수행하였다. 용출실험 결과, Ca₂+ 이온의 용출은 시험된 최대 농도에서 보다 0.1 M NaCl과 0.5 M MgCl₂에서 최대로 나타났으며, MgCl₂는 NaCl에 비해 10배 이상의 Ca₂+ 이온을 용출력을 보였다. 미분(< 0.15 mm)의 시멘트 풀은 직접수성탄산화에 의해 1시간 이내에 탄산화에 의해 포트랜다이트가 거의 모두 탄산염 광물로 변화하고, CSH(calcium silicate hydrate)의 분해에 의한 탄산화도 진행되는 것으로 나타났다. 그러나 직접수성탄산화에는 NaCl과 MgCl₂와 같은 첨가제가 크게 효율적이지 못하였다. NaCl과 MgCl₂를 첨가제로 사용한 용출액에 대한 간접수성탄산화로 100% 순수한 방해석을 생성되었다. MgCl₂에 의한 용출액의 경우 탄산화를 위해 알칼리용액 의한 pH의 조절이 필요하였으며, Mg²+ 이온의 영향으로 탄산화가 느리게 진행되었다. 수성탄산화 방법과 첨가제의 종류가 생성되는 탄산칼슘광물의 종류와 결정도 영향을 미치는 것으로 나타났다. Waste cement generated from recycling processes of waste concrete is a potential raw material for mineral carbonation. For the CO2 sequestration utilizing waste cement, this study was conducted to obtain basic information on the aqueous carbonation methods and the characteristics of carbonate mineral formation. Cement paste was made with W:C= 6:4 and stored for 28 days in water bath. Leaching tests using two additives (NaCl and MgCl2) and two aqueous carbonation experiments (direct and indirect aqueous carbonation) were conducted. The maximum leaching of Ca2+ ion was occurred at 1.0 M NaCl and 0.5 M MgCl2 solution rather than higher tested concentration. The concentration of extracted Ca2+ ion in MgCl2 solution was more than 10 times greater than in NaCl solution. Portlandite (Ca(OH)2) was completely changed to carbonate minerals in the fine cement paste (< 0.15 mm) within one hour and the carbonation of CSH (calcium silicate hydrate) was also progressed by direct aqueous carbonation method. The both additives, however, were not highly effective in direct aqueous carbonation method. 100% pure calcite minerals were formed by indirect carbonation method with NaCl and MgCl2 additives. pH control using alkaline solution was important for the carbonation in the leaching solution produced from MgCl2 additive and carbonation rate was slow due to the effect of Mg2+ ions in solution. The type and crystallinity of calcium carbonate mineral were affected by aqueous carbonation method and additive type.

순환 유동층 보일러 애시의 촉진탄산화에 의한 탄소포집 특성

최영철 ( Young-cheol Choi ),유성원 ( Sung-won Yoo ) 한국구조물진단유지관리공학회 2021 한국구조물진단유지관리공학회 논문집 Vol.25 No.5

이 연구는 건설재료로 활용 가능성이 높은 다양한 무기계 재료의 탄소포집에 대한 성능 평가를 목적으로 한다. 이러한 목적을 위해 광물탄산화가 가능한 보통포틀랜드 시멘트(OPC), 고로슬래그 미분말(GGBS), 순환유동층 보일러 애시(CFBC)의 탄산화 반응에 대한 특성 변화를 분석하였다. 촉진 탄산화 실험을 통해 모든 재료에 대한 탄산화 양생을 수행하였으며, 탄산화 재령에 따라 열중량 분석에 의해 탄소포집량을 정량분석하였다. 모든 재료에서 탄소포집 효과가 확인되었고, 실험결과 탄소포집량은 CFBC, OPC, GGBS 순으로 나타났다. CFBC, OPC, GGBS의 28일 탄소포집량은 각각 9.4 wt.%, 3.9 wt.%, wt.1.3 %이다. 탄소포집은 탄산화 초기에 빠르게 발생하였으며, 재령이 증가함에 따라 느리게 발생하였다. SEM 이미지 분석을 통해, 모든 실험체에서 탄산화 양생에 의해 발생된 추가적인 생성물은 탄산칼슘(CaCO3)으로 나타났다. The purpose of this study is to investigate the carbon capture capacity of various inorganic materials. For this purpose, the change in property of ordinary Portland cement (OPC), blast furnace slag fine powder (GGBS), and circulating fluidized bed boiler ash (CFBC) due to carbonation were analyzed. Carbonation curing was performed on all specimens through the accelerated carbonation experiment, and the amount of carbon capture was quantitatively analyzed by thermogravimetric analysis according to the age of carbonation. From the results, it is confirmed that the carbon capture capacity was shown in all specimens. The carbon capture amount was shown in the order of CFBC, OPC, and GGBS. The 28-day carbon capture of CFBC, OPC, and GGBS was 3.9%, 1.3%, and 9.4%, respectively. Carbon capture reaction occurred rapidly at the beginning of carbonation, and occurred slowly with increasing age. SEM image analysis revealed that an additional product generated by carbonation curing in all specimens was calcium carbonate.

Non-destructive assessment of carbonation in concrete using the ultrasonic test: Influenced parameters

Javad Royaei,Fatemeh Nouban,Kabir Sadeghi 국제구조공학회 2024 Structural Engineering and Mechanics, An Int'l Jou Vol.89 No.3

Concrete carbonation is a continuous and slow process from the outside to the inside, in which its penetration slows down with the increased depth of carbonation. In this paper, the results of the evaluation of the measurement of concrete carbonation depth using a non-destructive ultrasonic testing method are presented. According to the results, the relative nonlinear parameter caused more sensitivity in carbonation changes compared to Rayleigh’s fuzzy velocity. Thus, the acoustic nonlinear parameter is expected to be applied as a quantitative index to recognize carbonation effects. In this research, combo diagrams were developed based on the results of ultrasonic testing and the experiment to determine carbonation depth using a phenolphthalein solution, which could be considered as instructions in the projects involving non-destructive ultrasonic test methods. The minimum and maximum accuracy of this method were 89% and 97%, respectively, which is a reasonable range for operational projects. From the analysis performed, some useful expressions are found by applying the regression analysis for the nonlinearity index and the carbonation penetration depth values as a guideline.

Efficiency Enhancement by pH Swing in Indirect Carbonation using Paper Sludge Ash and Acid

Dami Kim,Myoung-Jin Kim 한국폐기물자원순환학회 2015 한국폐기물자원순환학회 학술대회 Vol.2015 No.05

Carbon dioxide has steadily increased in atmosphere since the industrial revolution, and it is the main cause of the global warming. In this study, carbon dioxide is stored in the form of insoluble calcium carbonate through indirect carbonation using paper sludge ash (PSA) as a raw material and acids (acetic acid and hydrochloric acid) as solvents. Acid is very efficient to extract calcium from PSA, which is as high as 55%. However, since the pH of calcium extractant obtained using acid is as low as 6 and carbon dioxide is not present in the form of CO32- at the low pH, carbonation reaction does not occur to form calcium carbonate. Sodium hydroxide, therefore, is added into the calcium extractant to increase pH up to 13. The amount of sodium hydroxide is calculated based on the equivalent of calcium in the extractant. Then, carbon dioxide is injected into the calcium extractant for 30 minutes at a flow rate of 0.05 L/min. The calcium extractant is prepared in advance using 40 g of PSA and 1L of 0.7 M acid, and 35mL of 50% sodium hydroxide is added into the extractant to adjust pH. During carbonation, liquid samples are taken at designated intervals to measure pH and calcium concentration. After the carbonation is completed, white solids are collected to dry at 105℃ for 12 hours, which weigh 30.0 g and 33.1 g from the extractants using acetic acid and hydrochloric acid, respectively. The white solids are found to be highly pure calcite by XRD analysis. Based on the solid mass, the amounts of carbon dioxide sequestrated in PSA are calculated to be 330.4 kg CO2/ton PSA and 363.7 kg CO2/ton PSA using acetic acid and hydrochloric acid as solvents, respectively.

Service life evaluation of RC T-girder under carbonation considering cold joint and loading effects

Koh, Tae-Ho,Kim, Moon-Kyum,Yang, Keun-Hyeok,Yoon, Yong-Sik,Kwon, Seung-Jun Elsevier 2019 Construction and Building Materials Vol.226 No.-

<P><B>Abstract</B></P> <P>Carbon dioxide concentration is steadily increasing in large cities. Consequently, durability evaluation of RC (Reinforced Concrete) structures considering carbonation is becoming a serious issue. Construction joints are used for the effective construction of concrete structures. However, cold joints which are caused by delayed placing and poor surface treatment are vulnerable to shear force and the inflow of carbon dioxide. In this study, an accelerated carbonation test was performed for normal-strength concrete using NPC (Normal Portland Cement) and slag after applying tensile and compressive stresses. The carbonation characteristics were quantified considering the effects of cold joint and the induced stress, and structural analysis was performed using the section laminae approach for a 2-span continuous reinforced concrete T-beam bridge. The service life of top and bottom concretes was evaluated considering the calculated stress, existing carbonation velocity equation, and carbonation function according to the stress. The service life showed a similar trend to that of the applied moment. Changes of 103.6%–64.7% (NPC) and 78.0%–108.8% (slag) were observed on the top surface, whereas changes of 103.8%–65.9% (NPC) and 112.9%–79.6% (slag) were observed on the bottom surface. The service life significantly decreased owing to the increasing carbonation depth for the cold joint in the tension part. This suggests that special care should be taken for cold joints during maintenance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Quantitative evaluation of cold joint effect on carbonation. </LI> <LI> Combined effect of cold joint and induced stress on carbonation velocity. </LI> <LI> Evaluation of varying service life of T-Girder considering stress level and cold joint. </LI> <LI> Greatly reduced service life in tensile zone with cold joint regardless of crack initiation. </LI> <LI> Effective maintenance plan through cold joint and loading level. </LI> </UL> </P>