• Journal of the Korean Society of Hazard Mitigation
• /
• v.7 no.2 s.25
• /
• pp.7-12
• /
• 2007

This study has been conducted to present reform recommendations for Standardization of Construction Materials, based on a study on the Investigation of Demander's Consciousness for Construction Materials Quality and Information Standardization in Korea. Upon investigation, it was found that the quality of Korea Industrial Standards (KS) was given 67 points (out of 100) by respondents. In addition, 38% of the respondents showed that they had problems with a lack of Standardized Information. Good examples were found to be non-standardized materials, e.g. admixtures, waterproof agents, reinforcing fibers, concrete, aggregates, adhesives, wood, temporary materials, thermal-insulating materials, etc. Upon results from the investigation of demander's consciousness for infrastructure of standardization of information, 71.2% of respondents thought that it is necessary to informatize construction materials. They made following demands on the informatization to be, in order: Quality, Standard, Price (Cost), Operation, Drawing, Law, and Information.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.12 no.1
• /
• pp.33-39
• /
• 2024

In this study, the basic properties of cement paste with varying replacement ratio of micro-silica and fumed silica were analyzed to determine the suitability of nanomaterials for use as concrete admixtures. Referring to the ultra-high strength mix, the fluidity of cement paste was evaluated according to the nanomaterial replacement rate and the compressive strength characteristics were compared and analyzed. The related properties of the reactive nanomaterials to the cement hydrate were analyzed using SEM and EDS to observe the microstructure and identify the components of the hydration product. The reactive nanomaterials used in this study had tap densities between 0.061 and 0.264 g/cm³, which were lower than SF. Micro silica exhibited excellent compressive strength properties with increasing replacement ratio, but fumed silica, unlike micro white, obtained excellent compressive strength at replacement ratio of 0.01~0.1 %. The same trend was observed in the hydration characterization.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.12 no.1
• /
• pp.82-93
• /
• 2024

Since the cement industry generates more than 60 % of CO₂ during the clinker production process, supplementary cementitious materials are used worldwide to reduce CO₂ efficiently. Mainly used supplementary cementitious materials such as blast furnace slag and fly ash, which are used in various industries including the cement industry, concrete admixtures, and ground solidification materials. However, since their availability is expected to decrease in the future according to the carbon neutrality strategy of each industry, new supplementary cementitious materials should be used to achieve the cement industry's goal for increasing the additive content of Portland cement. Limestone is a material that already has a large amount in the cement industry and has the advantage of high grinding efficiency, so overseas developed countries established Portland limestone cement standards and succeeded in commercialization. This study was an experimental study conducted to evaluate the possibility of utilizing domestic PLC, the effect of fineness and replacement ratio on the physical properties of cement was investigated, and the environmental impact of cement was evaluated by analyzing CO₂ emissions.

• Geotechnical Engineering
• /
• v.14 no.6
• /
• pp.113-125
• /
• 1998

At the end of 1997 about 3 million tons of coal ash was produced as byproducts from the coal fired electrical power plants in Korea. Only about 27% of that byproducts was utilized as the admixtures of cement and concrete industry. But the large quantity of coal fired fly-ash has been used as the soil improvement materials in other countries. So the aim of this study is the estimation of the applicability of the coal fired fly-ash as microfine grouting materials by admixing the superfine particles which were separated from the coal fired fly-ash for the higher values. The 6 types of specimens were manufactured in the laboratory for the purpose of estimating the chemical and physical properties of cement and grouts. These specimens consisted of 2 specific surfaces of 6, 000 and 8, 000$cm^2$/g in Elaine method. And these specimens are devide into 3 ratios (30%, 50%, 70%) of fly-ash by weight. From the estimated properties of the coal fired fly-ash microflne cements and grouts, 50% fly-ash is the most suitable ratio for grouting materials. However, further study of durability is necessary for using fly-ash grouts practically at the field projects. The higher content of the unburned carbon of fly-ash increases the thinner layer of carbon on the surface of solution of grouts, and requires more quantity of surface active agent. As a results of this study, it is found that the microfine fly-ash is very useful as a good grouting material if 50% of fly-ash is added with the microfine portland cement. So, in the near future, if the coal fired fly-ash is able to be used as grouting material in Korea, the demand of fly-ash will increase rapidly.

• Journal of the Korean Ceramic Society
• /
• v.39 no.5
• /
• pp.452-459
• /
• 2002

This paper addresses the hydrothermal reactivity of blast furnace slag and fly ash with lime, respectively. The test conditions were CaO-to-$SiO_2$ ratio (C/S), autoclaving temperature ($140{\circ}C$ and $180{\circ}C$) and time (20 to 60h). The study was carried out in terms of the hydrothermal reactivity between $SiO_2$ contained in each hydraulic material and (pure) lime and the compressive strength of autoclaved specimens. Porosity measurement and the XRD analysis were also made in order to ascertain the hydraulicity of the siliceous materials. Compressive strength of the specimens was interpreted in terms of porosity and the reactivity of CaO and $SiO_2$. And the XRD analysis showed the C/S change of the hydrates in the course of autoclaving process. $SiO_2$ in the blast furnace slag was more reactive with CaO than that in the fly ash and consequently the blast furnace slag specimens resulted in much higher compressive strength. A maximum compressive strength of $807kg/cm^2$ was obtained for the blast furnace slag at the autoclaving condition of $180{\circ}C$ and 40 h, while only $397kg/cm^2$ was maximally to achieve with fly ash.

• Journal of the Korea Institute of Building Construction
• /
• v.11 no.6
• /
• pp.587-596
• /
• 2011

Ultra rapid-hardening cement is widely used for latex-modified mortar and concrete as repair and finishing material during urgent work. The purpose of this study is to evaluate the improvements in strength made to SBR cement mortars by the adding of various admixtures and by the use of different curing methods. SBR cement mortar was prepared with various polymer-cement ratios, curing conditions and admixture contents, and tested for flow, flexural and compressive strengths. From the test results, it was determined that the flow of SBR cement mortar increased with an increase in the polymer-cement ratio, and the water reducing ratio also increased. The strength of cement mortar is improved by using SBR emulsion, and is strengthened by adding metakaoline. The strength of SBR cement mortar cured in standard conditions was increased with an increase in the polymer-cement ratio, and attained the maximum strengths at polymer-cement ratios of 15 % and 10 %, respectively. The maximum strengths of SBR cement mortar are about 1.8 and 1.3 times the strengths of plain mortar, respectively. In this study, it is confirmed that the polymer-cement ratio and curing method are important factors for improving the strengths of rapid-hardening SBR cement mortar.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.8 no.2
• /
• pp.190-197
• /
• 2020

This paper evaluates the mechanical properties and durability of cement matrix blended with mineral admixtures and ferronickel slag(FNS) powder which is an industrial b y-product during ferronickel smelting process. The hydration heat, pore structure, compressive strength, length change, rapid chloride penetration test(RCPT), and freezing and thawing resistance of ternary blended cement matrix were investigated and compared with ordinary portland cement matrix. The result showed that the compressive strength of ternary blended cement matrix using ferronickel slag powder and mineral mixture was low in strength compared to the reference concrete, but recovered to a certain extent by using alkali activator. Length change of cement mortar using FNS powder have shown less shrinkage occurs than the reference specimen. In addition, irrespective of using the alkali-activators, all ternary mix are indicative of the 'very low' range for chloride ion penetrability according to the ASTM C 1202, and the freeze-thaw resistance also showed excellent results.

• 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 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.