• Title/Summary/Keyword: modified by carbonation

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Performance Evaluation of Recycled Aggregate Concrete Made of Recycled Aggregate Modified by Carbonation (탄산화 개질 순환 골재를 사용한 순환 골재 콘크리트의 성능 평가)

  • Ha, Jung-Soo;Shin, Jin-Hak;Chung, Lan;Kim, Han-Sic
    • Journal of the Korea Concrete Institute
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    • v.28 no.4
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    • pp.445-454
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    • 2016
  • With the increase of decrepit facilities, construction waste increased to a certain level and now the increase is more or less stabilized. Yet construction waste still constitutes the largest portion of the overall wastes. Also, it is inevitable to spend a huge amount of the national budget due to the aggravating shortage of aggregate caused by prohibition on collection of natural aggregates as well as due to the damage to the land and environment caused by development of the sources of aggregates. As a countermeasure to the situation, the Ministry of Land, Infrastructure and Transport promulgated the quality standard for recycled aggregate to manage the usage of recycled aggregate according to its quality. But use of recycled aggregate for the purpose of high added value still remains nominal. Therefore, this research aims to study the applicability of recycled aggregate concrete as structural concrete by evaluating the quality improvement effects and the performance of the recycled aggregate concrete including recycled fine aggregate and recycled coarse aggregate that have undergone carbonation for 4 days and 14 days respectively in the condition of 60% RH, 20% $CO_2$ and $20^{\circ}C$ temperature, suggested for carbonation modifying from the advance research. The result shows carbonation modify contributed to quality improvement with 0.91% decrease in absorption rate for recycled fine aggregate and 0.7% decrease in absorption rate for recycled coarse aggregate. The physical properties and durability of the recycled aggregate made of aggregate modified by carbonation showed results similar to general concrete, which confirmed the possibility of applying the recycled aggregate made of recycled aggregate modified by carbonation to structural concrete.

Evaluation on the Properties of Modified-sulfur Concrete as a Basic Study for Development of Anti-corrosive Concrete (내부식성 콘크리트 개발을 위한 기초연구로서 개질유황 혼합 콘크리트의 물성 평가)

  • Park, Sang-Soon;Na, Ok-Jung
    • Corrosion Science and Technology
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    • v.15 no.1
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    • pp.28-37
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    • 2016
  • Due to the increased construction of offshore concrete structures and the use of de-icing salts for the purpose of snow removal, the needs for the development of anti-corrosive concrete are increasing. To solve these problems, an evaluation of the mechanical and durability properties for concrete were conducted by mixing modified-sulfur as 0 %, 5 %, 10 %, 15 % cement weight ratio. Both strengths and the properties affecting durability such as water absorption coefficient, chloride ion permeability, accelerated carbonation resistance, rapid freezing and thawing, and chemical resistance were evaluated. All evaluations performed were according to the test specifications associated KS. The results indicate that mixing of modified-sulfur lowed chloride ion permeability and improved chemical resistance.

The Mineral Carbonation Using Steelmaking Reduction Slag (제강 환원슬래그의 광물탄산화)

  • Ryu, Kyoung-Won;Choi, Sang-Hoon
    • Economic and Environmental Geology
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    • v.50 no.1
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    • pp.27-34
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    • 2017
  • Mineral carbonation for the storage of carbon dioxide is a CCS option that provides an alternative for the more widely advocated method of geological storage in underground formation. Carbonation of magnesium- or calcium-based minerals, especially the carbonation of waste materials and industrial by-products is expanding, even though total amounts of the industrial waste are too small to substantially reduce the $CO_2$ emissions. The mineral carbonation was performed with steelmaking reduction slag as starting material. The steelmaking reduction slag dissolution experiments were conducted in the $H_2SO_4$ and $NH_4NO_3$ solution with concentration range of 0.3 to 1 M at $100^{\circ}C$ and $150^{\circ}C$. The hydrothermal treatment was performed to the starting material via a modified direct aqueous carbonation process at the same leaching temperature. The initial pH of the solution was adjusted to 12 and $CO_2$ partial pressure was 1MPa for the carbonation. The carbonation rate after extracting $Ca^^{2+}$ under $NH_4NO_3$ was higher than that under $H_2SO_4$ and the carbonation rates in 1M $NH_4NO_3$ solution at $150^{\circ}C$ was dramatically enhanced about 93%. In this condition well-faceted rhombohedral calcite, and rod or flower-shaped aragonite were appeared together in products. As the concentration of $H_2SO_4$ increased, the formation of gypsum was predominant and the carbonation rate decreased sharply. Therefore it is considered that the selection of the leaching solution which does not affect the starting material is important in the carbonation reaction.

Mechanical Properties and Durability of Asphalt Emulsion-Modified Cement Mortars

  • Song Hun;Do Jeong-Yun;Soh Yang-Seob
    • Journal of the Korea Concrete Institute
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    • v.17 no.3 s.87
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    • pp.467-472
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    • 2005
  • Asphalt emulsion is manufactured by the emulsification of asphalt, and is considered as an energy-saving, ecologically safe material because it does not need any heating processes with gas emission and fire hazard in its use. This study is concerned with evaluating the feasibility of the use of an asphalt emulsion as a poly-meric admixture. Asphalt-modified mortars using an experimentally manufactured asphalt emulsion were prepared with various polymer-cement ratios, and tested far the mechanical properties such as strengths and adhesion and the properties related to durability such as water absorption, permeation, carbonation and chloride ion penetration. As a result, the waterproofness, carbonation resistance and chloride ion penetration resistance of the asphalt-modified mortars were markedly improved with an increase in the polymer-cement ratio, but their compressive strength and adhesion to mortar substrates were reduced with increasing polymer-cement ratio. Therefore, it is recommended to control their polymer-cement ratio to be $10\%$ or lower in their practical applications. Further study to improve their compressive strength and adhesion is needed.

A Study on the Optimization of Recycled Aggregate Alkalinity Reducing Facility in the Field (순환골재 알카리 저감장치의 현장 최적화에 관한 연구)

  • Lee, Jong-Chan;Song, Tae-Hyeob;Lee, Sae-Hyun;Kim, Jong-Bok
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.6 no.3
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    • pp.53-60
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    • 2011
  • As Construction & Demolition(C&D) debris increase every year, a system has enforced for recycled aggregate made out of C&D debris, then recycled aggregate usage increased in construction field. But as environmental problem by alkalinity of recycled aggregate occurred, the study for lowering alkalinity of recycled aggregate is needed. In this study we made alkalinity reducing facility and installed in the C&D debris midterm-treat field. Then we certified effect of lowering alkalinity and quality of recycled aggregates before and after carbonation. As a result, the most effective carbonation condition is 30seconds in carbonation time, -50~100 kPa of reaction pressure with change of 3cycles. This condition made pH 9.33~9.8 of recycled aggregate possible. The quality of recycled aggregate after carbonation was better than before carbonation in terms of plasticity index, modified CBR, abrasion loss, sand equivalent, liquid limit, size distribution, density and water absorption.

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Prediction of Carbonation Progress for Concrete Structures Considering Change of Atmospheric Environment (대기환경변화를 고려한 콘크리트 구조물의 중성화 예측)

  • Lee, Chang-Soo;Yoon, In-Seok
    • Journal of the Korea Concrete Institute
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    • v.15 no.4
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    • pp.574-584
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    • 2003
  • The most common deterioration cause of concrete structures in urban environment is carbonation. Recently, the $CO_2$ concentration and temperature at atmosphere is sharply increased with time due to global warming phenomena. In this study, the climate scenario IS92a, which was suggested by the IPCC, is used to consider temperature and atmospheric $CO_2$ concentration change in the model of service life prediction. The modified mathematical solution, which was based on the Fick's 1st law of diffusion, was used to reflect concrete materials properties such as the degree of hydration of concrete with elapsed time, and important parameters, which associated with deterioration rate. The techniques of service life prediction are developed introducing the method of reliability and stochastic concept to consider microclimatic condition in Seoul, South Korea. From the result of service life prediction, concrete containing high W/C ratio is shown fast carbonation rate due to $CO_2$ concentration increase. It is concluded that the deterioration of concrete structures due to carbonation is insignificant problem on the conditions that below W/C 55%, well curing concrete.

Corrosion-Inhibition and Durability of Polymer-Modified Mortars Using Bisphenol A and F Type Epoxy Resin with Calumite (비스페놀 A 및 F형 에폭시수지와 칼루마이트를 병용한 폴리머 시멘트 모르타르의 방청성 및 내구성)

  • Kim, Joo-Young;Kim, Wan-Ki
    • Journal of the Korea Concrete Institute
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    • v.26 no.4
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    • pp.517-524
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    • 2014
  • Nitrite-Type hydrocalumite (calumite) is a material that can adsorb chloride ions ($Cl^-$) that cause corrosion of reinforce bars and liberate the nitrite ions ($NO_2{^-}$) that inhibit corrosion in reinforced concrete. In this study, polymer-modified mortars using two types of epoxy resin with calumite are prepared with various polymer binder-ratios of 0, 5, 10, 15, 20% and calumite contents of 0, 5%. The specimens are tested for chloride ion penetration, carbonation, drying shrinkage and corrosion inhibition. As a result, the chloride ion penetration and carbonation depth of PMM using epoxy resin somewhat increases with increasing calumite contents, but those remarkably decreases depending on the polymer-binder ratios. The 28-d drying shrinkage shows a tendency to decrease with increasing polymer-binder ratio and calumite content. Unmodified mortars with calumite content of 5% did not satisfy quality requirement by KS. However, it was satisfied with KS requirement by the modification of epoxy resin in cement mortar. On the whole, the carbonation and chloride ion penetration depth of epoxy-modified mortars with calumite is considerably improved with an increase in the polymer-binder ratio regardless of the calumite content, and is remarkably improved over unmodified mortar. And, the replacement of the portland cement with the calumite has a marked effect in the corrosion-inhibiting property of the epoxy-modified mortars.

Application of Alkali-Activated Ternary Blended Cement in Manufacture of Ready-Mixed Concrete (알칼리 활성화 3성분계 혼합시멘트의 레미콘 적용 시험)

  • Yang, Wan-Hee;Hwang, Ji-Soon;Lee, Sea-Hyun
    • Journal of the Korea Institute of Building Construction
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    • v.17 no.1
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    • pp.47-54
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    • 2017
  • Cement industry is typical carbon-emission industry. If the industrial by-products(granulated blast-furnace slag (GGBFS), fly ash, etc.) are used a large amount, it might be able to reduce cement consumption and mitigate carbon emissions. In this case, however, decrease of early strength is relatively large. Therefore, there is a limitation in increase of the amount of substitute. Considering these circumstances, it would be a good solution to reduce carbon emissions in cement industry to improve the performances of mixed cement through proper alkali-activation in Portland blended cement using GGBFS or fly ash. Therefore, this study prepared concrete in ready-mixed concrete manufacturing facilities with an addition of a binder which used 2.0% modified alkali sulfate activator after mixing Portland cement, GGBFS and fly ash in the ratio of 4:4:2 and assessed its basic properties. The results found the followings: The use of modified alkali-sulfate activator slightly reduced slump and shortened setting time. As a result, bleeding capacity decreased while early strength improved. In addition, there is no big difference in carbonation resistance. It appears that there should be continued experiments and analyses on the related long-term aged specimens.

Durability of Polymer-Modified Mortars Using Acrylic Latexes with Methyl Methacrylate (MMA계 아크릴 라텍스를 혼입한 폴리머시멘트 모르타르의 내구성)

  • Hyung Won-Gil;Kim Wan-Ki;Soh Yang-Seob
    • Journal of the Korea Concrete Institute
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    • v.17 no.3 s.87
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    • pp.411-418
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    • 2005
  • Polymer-modified mortar and concrete are prepared by mixing either a polymer or monomer in a dispersed, or liquid form with fresh cement mortar and concrete mixtures, and subsequently curing, and if necessary, the monomer contained in the mortar or concrete is polymerized in situ. Although polymers and monomers in any form such as latexes, water-soluble polymers, liquid resins, and monomers are used in cement composites such as mortar and concrete, it is very important that both cement hydration and polymer phase formation proceed well the yield a monolithic matrix phase with a network structure in which the hydrated cement phase and polymer phase interpenetrate. In the polymer-modified mortar and concrete structures, aggregates are bound by such a co-matrix phase, resulting in the superior properties of polymer-modified mortar and concrete compared to conventional mortar and concrete. The purpose of this study is to obtain the necessary basic data to develope appropriate latexes as cement modifiers, and to clarify the effects of the monomer ratios and amount of emulsifier on the properties of the polymer-modified mortars using methyl methacrylate-butyl acrylate(MMA/BA) and methyl methacrylate-ethyl acrylate(MMA/EA) latexes. The results of this study are as follows, the water absorption, chloride ion penetration depth and carbonation depth of MMA/BA-modified mortar are lowest. However, they are greatly affected by the polymer-cement ratio rather than the bound MMA content and type of polymer.

The Effects of Silica Sol and Modified Latex on the Concrete Surface Protection Cement Mortar for Improvement of Durability of Concrete (콘크리트 내구성 향상을 위한 표면 보호용 시멘트 모르타르에서 실리카 및 개질 라텍스의 영향)

  • Kim, Yong-Hoon;Jeaong, Cheol-Soo;Song, Myong-Shin;Lee, Woong-Geol
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.12
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    • pp.715-722
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    • 2019
  • The durability of concrete structures deteriorates due to the corrosion of rebars and concrete deterioration by harmful ions (CO32-, Cl-, SO42-) penetrating and diffusing from the outside into concrete. Therefore, the use of surface-protection finishing mortar is very important for preventing or delaying the deterioration of concrete. In this study, the possibility of the prevention of deterioration or delay of deterioration of concrete was investigated using natural latex modified with silica sol and calcium ions for cement mortar, which can be used to repair the mortar of deteriorated concrete or for finishing the mortar of concrete. As a result, fine calcium silicate hydrate was formed in the pores of the cement material due to the calcium ions and silica sol components contained in the modified latex component that reduce the pore distribution of the cement mortar, thereby reducing the penetration and diffusion of harmful ions (CO32-, Cl-, and SO42-). Furthermore, the latex component was found to be present in the pores of the cement to improve the alkali resistance and carbonation resistance.