• Journal of the Korea Institute of Building Construction
• /
• v.16 no.5
• /
• pp.405-412
• /
• 2016

In order to examine the possibility of practical use of concrete at low-temperature environment using high early strength cement with cold resistance admixture, an experimental study on workability, freezing temperature and compressive strength of the mortar with different types of anti-freezer, water reducing agent and accelerator for freeze protection at low-temperature were evaluated. Compressive strength was increased in use of anti-freezer, especially SN anti-freezer was higher than CN anti-freezer. 0min flow was increased, the 20min flow was decreased. And 20min flow was improved in use of FR, RT water reducing agent. CF, LS accelerator for freeze protection, regardless of the type of water reducing agent, compressive strength was increased.

• Journal of the Korean GEO-environmental Society
• /
• v.22 no.3
• /
• pp.5-13
• /
• 2021

Due to population growth and industrial development, the amount of industrial waste is increasing every year. In particular, in a thermal power plant using finely divided coal, a large amount of coal ash is generated after combustion of the coal. Among them, fly ash is recycled as a raw material for cement production and concrete admixture, but about 20% is not utilized and is landfilled. Due to the continuous reclamation of such a large amount of coal ash, it is required to find a correct treatment and recycling plan for the coal ash due to problems of saturation of the landfill site and environmental damage such as soil and water pollution. In recent years, the use of a fluid embankment material that can exhibit an appropriate strength without requiring a compaction operation is increasing. The fluid embankment material is a stable treated soil formed by mixing solidifying materials such as water and cement with soil, which is the main material, and has high fluidity before hardening, so compaction work is not required. In addition, after hardening, it is used for backfilling or filling in places where compaction is difficult because higher strength and earth pressure reduction effect can be obtained compared to general soil. In this study, the possibility of use of fluidized soil using high water content cohesive soil and coal ash is considered. And it is intended to examine the flow characteristics, strength, and bearing capacity characteristics of the material, and to investigate the effect of reducing the earth pressure when applied to an underground burial.

• Korean Journal of Agricultural Science
• /
• v.11 no.1
• /
• pp.146-159
• /
• 1984

This study was the contrast of the compressive strength, the tensile strength, the reducing ratio and the flow of mortar using dispersing agent and high fluid admix. 1. The admix ratio of chemical admixtures espressing maximum strength appeared the same result high fluid admix SP was 0.6%, the dispersing agents LG and C211 were 0.2%, SK was 0.3%, C376 was 0.5%. But two or three times more than standard quantity made the strength's fast lowness, which influenced bad to wateriness and retard the soli-dification. 2. When proper quantity of chemical admixture was used, the increment of compressive strength was as follows. High fluid admix SP was 40.7% and the average increasing rate of dispersing agents(C211 was 19.5%, LG was 19.1%, C376 was 17.9%) was 18.7% more than normal mortar in the codition of 7 days. Also, in the condition of 28 days, high fluid admix SP was about 24.4% and the average of dispersing agents(LG was 21.1%, C211 was 16.4%, SK was 11.1%, C376 was 7.6%) was 14.1%. 3. When proper quantity of chemical admixture was used, the increment of tensile strength was as follows. High fluid admixture SP was 26.6% and the average increasing agents(SK was 16.0%, C376 was 14.7%, LG was 10%, C211 was 5.8%) was 11.6%. Also, in the condition of 28 days, high fluid admix SP was 16.5% and the average increasing rate of dispersing agents(LG was 19.1%, SK was 10.6%, C211 was 10.1%, C376 was 8.7%) was 12.1%. 4. As for the reducing ratio of each dispersing agent, he flow of mortar was less than the slump of concrete. That is; the reducing ratio of concrete was 15% adding each dispersing agent, but the reducing ratio of mortar was in the range of from 5.8% to 13.5% in 1 : 1 mixture, from 7.6% to 14.2% in 1 : 2, from 9.5% to 18.8% in 1 : 3. 5. The fluidity of each chemical admixture was as follows. High fluid admix SP in the condition of 1: 1 and 1 : 2 showed the best result than other dispersing agent and 1 : 3 showed the same result like other agents. Therefore these good dispersing agents were suitable in the prepact concrete construction using intrusion mortar.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.5 no.3
• /
• pp.275-281
• /
• 2017

This study is to investigate experimentally the effect of refining of fly ash (FA) on the engineering properties of the cement mortar. Five different FAs are used including raw fly ash, refined fly ash, reject ash and their two different combinations. The cement mortars are fabricated with 1:1(binder to fine aggregate), 1 : 3 and 1 : 5 respectively, which are replaced 30% of FA by cement. Test results, indicated that, the flow of Ra showed lower flowability than Rf at all mixing ratios. Also in the case of Rj, it was expected to show low fluidity, but it showed flowability equal to or higher than Rf. Air contents are all formulations except Rf and Rj did not satisfy the target range. Using Ra, the refining process shows an air amount about 41% lower than Rf, in the case of Rj, it showed about 19% higher air content than Rf due to porous foreign matters inside the mortar. Compressive strength was in the early days 3 and 7, the strength was lower than that of Plain's OPC, after 28 days Rf exerts higher strength than other FAs, it was confirmed that higher strength than OPC can be secured at a mixing ratio of 1: 1 and 1: 3. For frost resistance, the use of unrefined FA resulted in decrease of frost resistance sharply due to loss of air content by the use of unrefined FA. Therefore, it is considered that the use of high quality FA through refining process will contribute positively to the economical formulation of concrete and the stability of the structure.

• Journal of the Korea Institute of Building Construction
• /
• v.18 no.5
• /
• pp.429-437
• /
• 2018

The aim of the research is to analyze a feasibility of rapid evaluation method for cement fineness by the relation analysis between density measurement using hydrometer and fineness of ordinary Portland cement. Additionally, based on the commercially available cement product, relation between a series of fundamental properties of cement mortar and fineness of cement powder was analyzed. As an experimental result, the actually measured fineness value of cement powder showed a good correlation with the fineness value obtained by hydrometer while there was poor correlation with the fineness value on specification. Especially, the density measurement in three minutes showed the closest relation with cement powder fineness, thus rapid quality evaluation of cement powder can be possible by using the regression equation obtained from the three minutes density measurement. Additionally, there was a high relation between cement powder fineness with a fundamental properties of the cement mortar such as fluidity, air content, setting time, and strength development.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.11 no.1
• /
• pp.55-61
• /
• 2023

This study aims to develop CLSM fill material for emergency restoration using landfill coal ash. As a result of examining physical properties such as particle size distribution and fines content of landfill coal ash, bottom ash, fly ash, and general soil were mixed, and SP was found to have a density of 2.03 and a residual particle pass rate of 7.8 %. CLSM materials that secure fluidity in unit quantities without using chemical admixtures such as glidants and water reducing agents have a high risk of material separation due to bleeding. As a result of this experiment, it was found that the bleeding ratio did not satisfy the standard in the case of the specimen with a large amount of fly ash and a lot of addition of mixing water. As a result of the compressive strength test, the strength development of 0.5 MPa or more for 4 hours was found to be satisfactory for the specimens using hemihydrate gypsum with a unit binder amount of 200 or more, and the remaining gypsum showed poor strength development. Although it is judged that landfill coal ash can be used as a CLSM material, it is necessary to identify and apply the physical and chemical characteristics of coal ash buried in the ash treatment plant of each power generation company.

• Korean Journal of Heritage: History & Science
• /
• v.40
• /
• pp.357-386
• /
• 2007

At present, thirteen Buddhist bells of Unified Silla are known to the world: Six in Korea, five in Japan and two other bells, and three out of them are impossible to make out its original form. Therefore, we divided the form of Unified Silla Buddhist bells based on the ten other bells, and we tried out to prove the manufacturing technology by the comparison of the research material of Uncheon-dong bell and existing research materials of other bells, in other to find their linkage based on the alloy elemental composition. We divided Unified Silla Buddhist bell into two types: Type I has symmetric apsaras and regular patterns on its face and it was made in early Silla period; type II has asymmetric apsaras and irregular pattern arrangement and made in late Silla period. In particular, Uncheon-dong Buddhist bells is very similar to Komyoji[光明寺] temple bell from ninth century in Japan. It is peculiar that the apsaras on Uncheon-dong bell play vertical music instruments that are never seen in Unified Silla Buddhist bell. Most of Unified Silla Buddhist bell are compounded with Cu-Sn or Cu-Sn-Pb system. From eighth and ninth century, bells were cast with even composition of copper, tin and lead, and the bronze alloy ratio was similar to the record in Gogonggi[考工記], Jurye[周禮], a book from ancient China. Particularly, Uncheon-dong bell is in a rare case of Cu-Sn-Pb-As system. As had been rarely used in Unified Silla Buddhist bells, so we presented the relative research materials. As has the same nature as Pb. Because As easily volatilize at high temperature, it is hard to use. But it has its merit of solidity and durability. Pb enhances fluidity and thereby expresses the patterns more distinct; As makes the bell stronger. The result of lead isotope ratio could not exactly reveal a concrete producing center. However, over the analysis of our samples, hereby we suggest Uncheon-dong bell was made of materials from just one ore deposit.