• Journal of the Korean Recycled Construction Resources Institute
• /
• v.11 no.4
• /
• pp.416-424
• /
• 2023

Concrete emits a large amount of carbon dioxide throughout its life cycle, and due to the societal demand for carbon dioxide reduction, research on storing carbon dioxide in concrete in the form of minerals is ongoing. In this study, cyanobacteria, which absorb carbon dioxide through photosynthesis and fix it as calcium carbonate, were applied to a porous concrete substrate, and the changes in the properties of the concrete substrate due to their special environmental curing condition were analyzed. The results showed that the calcium carbonate precipitation by the microorganisms was concentrated in the light-exposed surface area, and most of the precipitation occurred in the cement paste part, not in the aggregate. This microbially induced calcium carbonate precipitation enhanced the mechanical performance of the paste and improved the overall compressive strength as the curing age progressed. In addition, the increase in microbial biofilm and calcium carbonate improved the pore structure, which influenced the reduction in water permeability.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.19 no.5
• /
• pp.45-55
• /
• 2015

Currently, extreme weather events such as super typhoon, extreme snowfall, and heat wave are frequently occurring all over the world by natural and human caused factors. After industrial growth in the 1970s, earth's temperature has risen sharply. due to greenhouse effect. Global warming can be attributed to gases emitted from using fossil fuel such as average carbon dioxide, perfluorocarbons, nitrous oxide, and methane. Especially, carbon dioxide has the highest composition of about 90%. in the fossile fuel usage emitted gas. Concrete has excellent durability as a building material climate change. However, due to various of physical and chemical environmental effect such as conditions during its curing process, the performance degradation may occur. Carbon dioxide in the atmosphere causes steel corrosion and durability decreases by lowering the alkalinity of concrete. Therefore, in this study, concrete durability performance with respect to carbonation from curing conditions change due to wind speed and sunshine exposure time. Concrete carbonation experiment are performed. using wind speed (0, 2, 4, 6) m/s and sunlight exposure time (2, 4, 6, 8) hrs. Also, performance based evaluation through the satisfaction curve based on the carbonation depth and carbonation rate test results are performed.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2023.11a
• /
• pp.75-76
• /
• 2023

In the cement industry, various research initiatives are underway to achieve carbon neutrality. Mineral carbonation is a technology that converts carbon dioxide into minerals for storage, and CO₂ reactive hardening cement is a type of cement that incorporates mineral carbonation technology. In this study, we aimed to manufacture CO₂ reactive hardening cement for reducing carbon emissions in the cement industry by utilizing waste concrete powder generated in the construction sector.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.11 no.4
• /
• pp.324-331
• /
• 2023

In this study, the hydration and carbonation properties of circulating fluidized bed boiler (CFBC) ash with different free-CaO contents were investigated. In addition, the possibility of utilizing CFBC ash with a high free-CaO content as a cementitious material was investigated by carbonation curing as a pretreatment. The CFBC ash with high free-CaO content exhibited rapid setting behavior and low early compressive strength when mixed with cement. For CFBC ash with high free-CaO content, carbon dioxide capture increased with the duration of carbonization curing. In addition, the free-CaO value decreased together, indicating that the free-CaO reacted with carbon dioxide. When the CFBC ash with high free-CaO content was pretreated by carbonation, no fresh set appeared, and the initial compressive strength was improved. From the results of this study, it is confirmed that CFBC ash with high free-CaO content has a high potential to be utilized as a cementitious material through proper carbonation curing.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.11 no.4
• /
• pp.349-354
• /
• 2023

This study wa s conducted a s pa rt of ma ximizing the use of ca rbon dioxide by a pplying CCU(Ca rbon Ca pture, Utiliza tion) a mong technologies for reducing CO₂ in the cement industry. In a carbon dioxide curing environment, changes in carbonation depth and changes in basic physical properties by age due to the mixing of carbonation reaction accelerators were usually targeted at Portland cement paste. In addition, in order to check the fixed amount of CO₂ in the concrete field, a thermal analysis method was applied to evaluate CaCO₃ decarbonization at high temperatures. As a result of the evaluation, it was confirmed that the carbonation depth in the cured body significantly increased due to the incorporation of CRA in the carbonation depth diffusion performance. In addition, it was confirmed that the weight reduction rate increased by 23.8 % and 40.77 %, respectively, compared to Plain, in the order of curing conditions for constant temperature and humidity and curing conditions for carbonation chambers, so it was confirmed that the amount of excellent CaCO₃ produced by the addition of CRA increased as the concentration of CO₂ increased.

• International Journal of Concrete Structures and Materials
• /
• v.18 no.1E
• /
• pp.17-22
• /
• 2006

Artificial cracks were made in the cover concrete of specimens embedding ten types of steel rebars of different Cr contents. The research aims for developing Cr-bearing steel rebars resistant to macrocell corrosion environments induced by cracking in cover concrete. The cracks were subjected to intensive penetration of carbon dioxide (carbonation specimens) to form macrocells. The carbonation specimens were then treated with accelerated corrosion curing, during which current macrocell corrosion density was measured. The corrosion area and loss from corrosion were also measured at the end of 105 cycles of this accelerated curing. The results of the study showed that Cr-bearing steel with Cr content of 5% or more suppressed corrosion in a macrocell corrosion environment induced by the differences in the pH values due to carbonation of cracked parts. Cr-bearing steels with Cr content of 7% or more are proven to possess excellent corrosion resistance.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2014.05a
• /
• pp.100-101
• /
• 2014

The global warming because of the CO₂ emission and solution about this emerge as the international enviroment problem. Particularly, it is the absolutely it is needed for reducing the CO₂ in the cement industry and harmful material actual condition. And the construction of home and abroad and material manufacturers tries for the technology development for the carbon dioxide and harmful material reduction which the portland cement in manufacture is usually emitted along with the increase of concerns about the environment-friendly concrete and panel. Therefore, in this research, the compressive strength of the inorganic binder and flexural strength tries to be measured in order to draw the inappropriate high temperature cure time of the ternary system inorganic binder using the blast furnace slag, red mud, silica fumewhich is the industrial byproduct with the cement substitute material, and etc.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.4
• /
• pp.766-771
• /
• 2016

This study examined the long-term durability of PC boxes, which was manufactured by low-carbon eco-friendly concrete using an alternative binder to cement and alternative fine aggregate to sand and microwave heat curing system to reduce the construction cost of a near-surface transit system. Based on the test results, the initial compressive strength of microwave heat cured concrete was higher than that of the steam cured concrete, but those were similar in the long-term age. In addition, there was no significant difference between the two curing conditions in the chemical resistance and the freeze-thawing resistance, and the chloride ion penetration level of the concrete cured by two methods was very low. Therefore, low-carbon eco-friendly concrete and microwave heat curing technology are expected to contribute to the economic construction of a near-surface transit system, and reduce carbon dioxide emissions and environmental impact.

• Korean Journal of Materials Research
• /
• v.22 no.2
• /
• pp.71-77
• /
• 2012

When a new bonding agent using coal ash is utilized as a substitute for cement, it has the advantages of offering a reduction in the generation of carbon dioxide and securing the initial mechanical strength such that the agent has attracted strong interest from recycling and eco-friendly construction industries. This study aims to establish the production conditions of new hardening materials using clean bottom ash and an alkali activation process to evaluate the characteristics of newly manufactured hardening materials. The alkali activator for the compression process uses a NaOH solution. This study concentrated on strength development according to the concentration of the NaOH solution, the curing temperature, and the curing time. The highest compressive strength of a compressed body appeared at 61.24MPa after curing at $60^{\circ}C$ for 28 days. This result indicates that a higher curing temperature is required to obtain a higher strength body. Also, the degree of geopolymerization was examined using a scanning electron microscope, revealing a micro-structure consisting of a glass-like matrix and crystalized grains. The microstructures generated from the activation reaction of sodium hydroxide were widely distributed in terms of the factors that exercise an effect on the compressive strength of the geopolymer hardening bodies. The Si/Al ratio of the geopolymer having the maximum strength was about 2.41.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.8
• /
• pp.338-343
• /
• 2017

In this study, blast furnace slag powder was used in concrete to help reduce carbon dioxide emissions and to recycle industrial waste. Blast furnace slag powder is a byproduct of smelting pig iron and is obtained by rapidly cooling molten high-temperature blast furnace slag. The powder has been used as an admixture for cement and concrete because of its high reactivity. Using fine blast furnace slag powders in concrete can reduce hydration heat, suppress temperature increases, improve long-term strength, improve durability by increasing watertightness, and inhibit corrosion of reinforcing bars by limiting chloride ion penetration. However, it has not been used much due to its low compressive strength at an early age. Therefore, this study evaluates the effects of steam curing for increasing the initial strength development of concrete made using slag powder. The relationship between compressive strength, SEM observations, and XRD measurements was also investigated. The concrete made with 30% powder showed the best performance. The steam curing seems to affect the compressive strength by destroying the coating on the powder and by producing hydrates such as ettringite and Calcium-Silicate-Hydrate gel.