• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2015.11a
• /
• pp.47-48
• /
• 2015

Recycled aggregate used in a site is strong alkali due to calcium hydroxide attached on its surface. Accordingly, many environmental problems arise. Therefore, as basic research to reduce pH of recycled aggregate, this study tries to reduce the strong alkalinity of recycled aggregate by using mixture solution based on sodium phosphate and ammonium chloride. As a result, original aggregate has the strong alkalinity of pH 11.23, whereas pH of recycled aggregate immersed in mixture solution decreased as more mixture rate increased, and mostly pH 9.8 or less was found.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2016.10a
• /
• pp.106-107
• /
• 2016

Construction waste is recycled and used for the efficient and eco-friendly disposal of construction waste increasing due to reconstruction and redevelopment project and so on. There is recycled aggregate as a typical case. And this recycled aggregate shows strong alkalinity due to calcium hydroxide, and causes many environmental problems. Therefore, this is a study on reduction in the strong alkalinity of recycled aggregate by using phosphate of ammonium in order to reduce the pH of recycled aggregate. Besides, a possibility that a pH reducing agent of recycled aggregate could be applied to a site was evaluated. As a result, it was possible to verify that pH decreased as the percentage of pH reducing agent increased. It is thought that the pH reducing agent can be applied to a site by methods such as immersion and spray using the pH reducing agent in the process of producing recycled aggregates.

• Journal of Korean Society on Water Environment
• /
• v.32 no.6
• /
• pp.546-551
• /
• 2016

In this study, capping with recycled aggregate and natural zeolite in marine sediment was performed to investigate its inhibitory effect on pollutants released from sediment to seawater. An experiment was performed by capping with amendments for 60 days, and concentrations of organic matter (COD), nitrate, phosphate and metallic elements (Ni, Zn, Cu, Pb, Cd, As, and Cr) were measured. Two capping materials effectively suppressed pollutant release. Recycled aggregate showed better effectiveness for organic pollutant, nitrate and phosphate release. Meanwhile, natural zeolite was effective for metallic elements. As a result, recycled aggregate and natural zeolite can be considered as cost-effective/inexpensive capping material candidates. Also, the capping material can be selected according to the target pollutant.

• Restorative Dentistry and Endodontics
• /
• v.37 no.4
• /
• pp.188-193
• /
• 2012

Mineral trioxide aggregate (MTA) was developed in early 1990s and has been successfully used for root perforation repair, root end filling, and one-visit apexification. MTA is composed mainly of tricalcium silicate and dicalcium silicate. When MTA is hydrated, calcium silicate hydrate (CSH) and calcium hydroxide is formed. Formed calcium hydroxide interacts with the phosphate ion in body fluid and form amorphous calcium phosphate (ACP) which finally transforms into calcium deficient hydroxyapatite (CDHA). These mineral precipitate were reported to form the MTA-dentin interfacial layer which enhances the sealing ability of MTA. Clinically, the use of zinc oxide euginol (ZOE) based materials may retard the setting of MTA. Also, the use of acids or contact with excessive blood should be avoided before complete set of MTA, because these conditions could adversely affect the hydration reaction of MTA. Further studies on the chemical nature of MTA hydration reaction are needed.

• Journal of the Korea Institute of Building Construction
• /
• v.17 no.1
• /
• pp.23-30
• /
• 2017

The aim of the research is to suggest an economical and sustainable method of reducing pH of recycled aggregate as an embanking and a covering materials. Because of the unhydrated cement based materials on the surface of the recycled aggregate, it causes a severe problem on environment with leaked high alkali water from embankment and covering by using recycled aggregate. In this research, to reduce the pH of recycled aggregate, regarding the recycled fine aggregate, eight different methods were tested and analyzed with three different categorized: natural treatment, artificial treatment, and chemical treatment. From the results of experiment, it was considered that the most efficient method of reducing pH of recycled aggregate was the chemical treatment using acid such as $CO_2$ acceleration or monoammonium phosphate (MAP), and diammonium phosphate (DAP). Especially, using MAP and DAP, fertilizers, is the most efficient method of reducing pH with its time duration and performance.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.3 no.4
• /
• pp.366-373
• /
• 2015

Construction waste is recycled and used for the efficient and eco-friendly disposal of construction waste increasing due to reconstruction and redevelopment project and so on. There is recycled aggregate as a typical case. And this recycled aggregate shows strong alkalinity due to calcium hydroxide, and causes many environmental problems. Therefore, this is a study on reduction in the strong alkalinity of recycled aggregate by using sodium phosphate based ammonium in order to reduce the pH of recycled aggregate. Besides, a possibility that a pH reducing agent of recycled aggregate could be applied to a site was evaluated. As a result, it was possible to verify that pH decreased as the percentage of pH reducing agent increased. It is thought that the pH reducing agent can be applied to a site by methods such as immersion and spray using the pH reducing agent in the process of producing recycled aggregates.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1998.10b
• /
• pp.912-915
• /
• 1998

As a fundamental study on the development of porous concrete for planting, this study is designed to present the properties of porous concrete by varying the kinds of cement, paste to aggregate ratio and dosage of AE admixture. As the results of experiment, the void volumes show 30~33%, 25~ 28% and 17~22% respectively, with paste to aggregate ratio of 20%, 30% and 40%. And unit weight is 1700~1900kg/㎥ while compressive strengths 40~60, 8 0~100 and 120~150kg/$\textrm{cm}^2$. pH of concrete shows a sufficient value at which the plant could grow, when the concrete is permeated in Ammonium Phosphate Dibasic for more than 1 hour. In brief, it shows a possibility of development of porous concrete if the concrete is permeated with permeating in Ammonium Phosphate Dibasic for more than 1 hour when the blast furnace slag cement is used.

• KSBB Journal
• /
• v.5 no.4
• /
• pp.347-353
• /
• 1990

The effects of nutrients and cell aggregate size on the cell growth of D. carota and the biosynthesi of carotenoid were investigated. Highest carotenoid content was obtained with sucrose as a carbon source and the equal ratio of ammonium to nitrate. High phosphate concentration stimulated the carotenoid biosynthesis in D. corota. 2,4-D inhibited the cell growth but stimulated the specific carotenoid content at high concentration. By modifying the medium composition based on these findings, three times higher specific carotenoid content and 2.5 times higher total carotenoid content were obtained as compared with the results obtained with basic MS media. Biosynthesis of carotenoid was found to be affected by cell aggregate size; high carotenoid production was obtained from the large aggregated cells resulted from high sucrose concentration.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2017.11a
• /
• pp.105-106
• /
• 2017

Previous studies have confirmed the performance of pH reduction agents using liquid sodium phosphate based ammonium chloride as a pH reduction agent. In this study, the pH reduction performance considering economical and applicability as a practical stage and the property change analysis for the identification of the reaction mechanism of the pH reduction agent were carried out. As a result, the pH reduction performance at a low rate of the pH reducing agent was confirmed. The specific gravity of CaO decreased significantly after XRF analysis. It is also believed that this reduces the amount of Ca(OH)₂ produced and contributes to pH reduction.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.26 no.1
• /
• pp.29-37
• /
• 2018

In this study, optimum extraction conditions for phosphorus recovery from sewage sludge ash(SSA) were investigated. For this purpose, an experiment was conducted to determine optimal recovery conditions for Ca-P type phosphorus by using calcium component in the recycled aggregate residue. The phosphorus content of sewage sludge ash was confirmed to be 5.0 %. When $H_2SO_4$ was used as an extract, concentration of 1 N $H_2SO_4$, L/S ratio of 10, and extraction time of 30 min were found to be the optimal extraction conditions. Phosphorus was extracted by using optimal extraction conditions, and then the heavy metals eluted with phosphorus were removed using 1~20 g of cation exchange resin. In 20 g of cation exchange resin, Fe 71.3%, Cu 82.4%, Zn 79.9%, and Cr 15% were removed. After that, the mixing ratio of the calcium extract obtained from the recycled aggregate residue (RAR) was changed to 1:1, 1:5, 1:10. The pH of the SSA to RAR mixture was adjusted to 2, 4, 8 and 12 by the addition of 5 N NaOH to the mixture of 1:5, and the phosphorus was recovered as Ca-P type precipitate. The optimum pH was 8. When recycled aggregate residues were used, the weight of calcium phosphate increased, but the amount of wastewater generated also increased. Therefore, it was concluded that the use of recycled aggregate residue was not economically feasible.