• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.32 no.4
• /
• pp.151-158
• /
• 2022

In this study, the waste concrete sample obtained as various particle size (0~2.36 mm) was carried out the basic measurements and carbonation for analyzing the possibility of its carbonation. It was then investigated some analysis such as crystallization (XRD pattern), microstructure (SEM), and the production of CaCO₃ through the ignition loss (TG-DTA). The content of CaCO₃ in the waste concrete sample before carbonation was found in 14.51 % and 28.52 % after carbonation in 24 hours. Moreover, the content of CaCO₃ carbonated in 24 hours with fine grinded waste concrete sample was 32.73 %. The carbonation of the waste concrete sample was rapidly performed up to 6 hours, but gradually increased from 12 to 24 hours. Especially, the amount of CaCO₃ between 12 and 24 hours was only produced 2.32 %. The calcite-shaped CaCO₃ crystals after carbonation of the waste concrete sample were found in microstructure and their peaks were strongly detected on XRD pattern.

• Journal of the Korean Ceramic Society
• /
• v.52 no.2
• /
• pp.154-158
• /
• 2015

This paper investigates the reaction rates of $CO_2$ that stores carbonation through comparing the carbonation behavior between $Ca(OH)_2$ and fly ash with circulating fluidized bed combustion (CFBC) containing a large amount of free CaO. Because fly ash with CFBC contains abundant free CaO, it cannot be used as a raw material for concrete admixtures; hence, its usage is limited. Thus, it has been buried until now. In order to consider its reuse, we conduct carbonation reactions and investigate its rates. X-ray diffraction (XRD), thermogravimetric/differential thermal analysis (TG/DTA), and X-ray fluorescence (XRF) are conducted for the physical and chemical analyses of the raw materials. Furthermore, we use a PH meter and thermometer to verify the carbonization rates. We set the content of the fly ash of CFBC, $Ca(OH)_2$, $CO_2$ flow rate, and water to 100 ~ 400 g, 30 ~ 120 g, 700 cc/min, and 300 ~ 1200 g, respectively, based on the content of the free CaO determined through the TG/DTA analyses. As a result, the carbonization rate of the fly ash with CFBC is the same as that of $Ca(OH)_2$, and it tends to increase linearly. Based on these results, we investigate the carbonization behavior as a function of the free CaO content contained in the raw material.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.23 no.6
• /
• pp.45-52
• /
• 2019

Steel corrosion due to carbonation in RC (Reinforced Concrete) structures easily occurs in urban cities with high CO₂ concentration. RC structures are always subjected to external loading with various boundary conditions. The induced stress level causes changes in diffusion of harmful ion like CO₂. In this work, a quantification of carbonation progress with stress level is carried out and carbonation prediction is derived through the relations. Determining the design parameters like cover depth, CO₂ diffusion coefficient, carbonatable materials, and exterior CO₂ concentration as random variables, service lifes under carbonation with design parameter's variation are obtained through MCS(Monte Carlo Simulation). Additionally the service life with different stress level is derived and the results are compared with those from deterministic method. Cover depth and cement hydrates are evaluated to be very effective to resist carbonation, and the proposed method which can consider the effect of stress on service life can be applied to maintenance priority determination.

• Journal of the Korean Applied Science and Technology
• /
• v.30 no.4
• /
• pp.770-778
• /
• 2013

In this study, a liquid carbonation method was applied for producing precipitate calcium carbonate by liquid-liquid reaction. We recycled the recycling water of ready-mixed concrete, one of construction waste for use source of carbonate ion. A supernatant separated from the recycling water of ready-mixed concrete, as a result of ICP analysis of a cation, $Ca^{2+}$ was contained up to 1100 ppm. We used MEA as a $CO_2$ absorbent for the liquid carbonation. A precipitate $CaCO_3$ was produced at more than MEA 20 wt%. The precipitate $CaCO_3$ as a final product was separated and dried. The result of XRD was confirmed the generation of $CaCO_3$ to calcite structure.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2020.06a
• /
• pp.71-72
• /
• 2020

γ-dicalcium silicate (γ-C2S) is characterized by its strong carbonation reactivity and has the prospect to be utilized as a building material with the added benefit of CO2 capture. This paper aims to point out the impact of γ-C2S on the microstructure characteristics and mechanical properties of GGBFS paste, and mortar samples. Three curing conditions including un-carbonation, natural carbonation, and accelerated carbonation were applied to the research. Besides, hydration products after the carbonation process are also detected. What's more, the carbonation treatment method also meets the requirement of capture more greenhouse gas and recycles the waste products of metallurgy.

• Economic and Environmental Geology
• /
• v.50 no.1
• /
• pp.27-34
• /
• 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.

• Computers and Concrete
• /
• v.10 no.3
• /
• pp.219-229
• /
• 2012

Carbonation is a widespread degradation of concrete and may be coupled with more severe degradations. An experimental investigation was carried out to study the effect of carbonation on chloride ion diffusion of concrete. The characteristic of concrete after carbonation was measured, such as carbonation depth, strength and pore structure. Results indicated that carbonation depth has a good linear relation with square root of carbonate time, and carbonation can improve compressive strength, but lower flexural strength. Results about pore structure of concrete before and after carbonation have shown that carbonation could cause a redistribution of the pore sizes and increase the proportion of small pores. It also can decrease porosities, most probable pore size and average pore diameters. Chloride ion diffusion of concrete after carbonation was studied through natural diffusion method and steady state migration testing method respectively. It is supposed that the chloride ion concentration of carbonation region is higher than that of the sound region because of the separation of fixed salts, and chloride ion diffusion coefficient was increased due to carbonation action evidently.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.1 no.1
• /
• pp.42-48
• /
• 2013

The present study assessed the amount of $CO_2$ uptake owing to concrete carbonation through a case study for an apartment building with a principal wall system and an office building with Rahmen system under different exposed environments during use phase and recycling application. The $CO_2$ uptake assessment owing to concrete carbonation followed the procedure established by Yang et al. As input data necessary for the case study, actual surveys conducted in 2012 in Korea, which included data about the climate environments, $CO_2$ concentration, lifecycle inventory database, life expectancy of structures, and recycling activity scenario, were used. From the comparisons with the $CO_2$ emissions from concrete production, the $CO_2$ uptake during the lifetime of structures was estimated to be 5.5~5.7% and that during recycling activity after demolition was 10~12%; as a result, the amount of $CO_2$ uptake owing to concrete carbonation can be estimated to be 15.5~17% of the $CO_2$ emissions from concrete production, which roughly corresponds to 18-21% of the $CO_2$emissions from cement production as well.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.9 no.1
• /
• pp.33-40
• /
• 2021

The objective of this work is to prove a possibility of void f illing through a carbonation f or the purpose of improving the quality of recycled aggregate. Carbonation can permanently immobilize CO2, which is a greenhouse gas, and thus provides additional benefit on environment. In this work, recycled fine aggregate was reacted using gaseous CO2 and supercritical CO2(scCO2) in a closed chamber, and the changes in physical properties of the recycled f ine aggregate bef ore and af ter carbonation were analyzed using the apparent density, skeletal density, pH, and FE-SEM measurements. Thereafter, a mortar specimen was prepared and a compressive strength was measured. According to the experimental results, it was found that the increase in the apparent density and the true density was higher by the reaction with scCO2, which was conducted at high temperature and high pressure compared to the reaction with gaseous CO2. In addition, the pH of the eluted water was found to have a larger initial decrease than that observed with samples from reaction by gaseous CO2. The shape and amount of calcium carbonate crystals were also found to be larger than that from gaseous CO2. The increase in compressive strength was the largest when using recycled fine aggregate reacted with scCO2. It was clear that quality improvement of recycled fine aggregate was higher with scCO2 than with gaseous CO2.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.11 no.4
• /
• pp.373-380
• /
• 2023

This study investigated the carbonation of concrete brick cured in a CO₂ environment for the utilization of CO₂ captured in power plants. Concrete brick specimens were produced with electric arc furnace reducing slag (ERS) and electric arc furnace oxidizing slag (EOS), and cured for 3 days in a CO₂ chamber with a concentration of 20 % or in a constant temperature and humidity chamber. The weight change, compressive strength, flexural strength and carbonation depth of concrete bricks were measured. From the results, it was found that when subjected to CO₂ curing, CO₂ was absorbed at the level of 2.4 % of the weight of the specimen. The specimen incorporating ERS showed the highest carbonation depth, and satisfied KS F4004 standards for the concrete brick. Therefore, it is expected that the captured CO₂ can be utilized in the CO₂ curing process of concrete brick.