• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.514-519
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• 2001

Converter has been slag produced 10 million tons per year in Japan. It is a steel making by product produced in the same way as the blast-furnace slag. Though blast-furnace slag is being used effectively as a concrete admixture, the converter stag has never been used effectively because of the expansion action of contained free lime and iron oxide. This is an important environmental problem in the steel industry. Beta-2CaOSiO$_2$(beta-C$_2$S) is contained 40 percent in converter slag, therefore it is very promising as a concrete admixture. We proposed an accelerated aging processes capable of stabilizing the converter slag in a short time. The converter slag is dipped into alkali aqueous solution after heating at low temperature. It was subsequently ground to a grain size of 75 ${\mu}{\textrm}{m}$ , inner 30 percent of OPC. The properties of mortar and concrete using the blended cement were determined. As a result, it has become apparent that the expansion was reduced and long term compressive strength was increased while that at early ages was not so remarkable. The hydration exotherm rate was lower than that of the OPC.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.122-123
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• 2015

Demands for the replacement materials of cement have been increasing due to social problems such as CO₂ reduction and exhaustion of resource. Recently industrial by-products, for example GGBFS and fly ash, have been used as an admixture. However Studies on POFA have been insufficient. POFA, which is used in this study, was obtained from burning of palm oil shell and husk from a southern part of Malaysia. In this study, early compressive strength and porosity of cement mortar with POFA are measured, and appropriate fraction of POFA is 10%. In terms of porosity, POFA is used as a filer in mortar. Later, activity index of POFA and long-term experiments are needed.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.228-231
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• 2004

The purpose of this study evaluates possibilities of waste phosphogypsum into concrete by steam curing admixture. The waste phosphogypsums were classified into 4 forms(Dihydrate, $\beta-Hemihydrate$, III-Anhydrite and II-Anhydrite) which were changed to in low temperature of calcination. Also, various admixtures were made of waste phosphogypsum(PG) and pozollanic fine powderers (Fly-ash, Blast Furnace Slag), and the basic properties of the cement mortars incorporating with these admixtures were examined and analyzed under a verity of experimental conditions. As a result, III-Anhydrite, these is similar to II-Anhydrite from compressive strength and are great in the effect of strength improvement. also, it was proved that specimens made on type III-Anhydrite of waste phosphogypsum and blast furnace slag increased on the compressive strength of cement mortar. Therefore, III-Anhydrite phosphogypsum calcined at lower temperature could be used as steam curing admixture for concrete 2th production.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.144-149
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• 2000

Porous cement concrete was developed to prevent hydroplaning of airway pavement or to reduce noise emission in highway. In has been introduced in domestic since early 1980' and applied to a pedestrian road or bike way. The concrete, however, has problems such as lack of optimized mix design, low strength and deterioration, etc. The purpose of this study is to manufacture porous cement concrete using blast-furnace slag to enhance mechanical properties. The results of this study are as follows; the compressive strength range is 102∼247kgf/㎠, the tensile strength range is 16∼70kgf/㎠, the bending strength range is 43∼70kgf/㎠, and the coefficient permeability range is 6.79 ×10-2∼1.17∼10-1cm/sec. To develope high-performance porous concrete, further studies are needed on optimum mixture of fineness modulus and admixture.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.781-786
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• 2003

This study has focused on the possibility for recycling tailings from the Sangdong tungsten mine as admixture for concrete. The XRD(X-ray diffraction analysis) and PSA(Particle size analysis) were performed to find mineralogical characteristics. As a result of XRD analysis, the tailings were composed of quartz, feldspars and muscovites, and C-S-H and quartz were found in cement mortar. As a result of KSLT for cement mortar mixed with tailings, most of heavy metals were determined as below the guide line for waste material. In addition, the setting time and compressive strength of cement mortar mixed with tailings were investigated. It was indicated that the initial and final set were retarded according to increasing replacement. The compressive strength of mortar was decreased with increasing replacement.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.10a
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• pp.26-27
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• 2016

This study analyzes the engineering characteristics of mortar according to admixture replacement ratios in cement mortar in a high-intensity ternary system, and changes in FA and BS combination ratios, in order to deduce the optimal combination ratio of FA and BS. Results showed that due to the characteristics of unhardened mortar, flow rate increased with the increase in admixture replacement and FA combination ratios, whereas air quantity decreased and setting time was delayed. Due to the characteristics of light mortar, compression strength decreased at early material ages as the overall combination ratio of FA increased. The FA : BS combination ratio was 2 : 3 on day 28 of material age, proving the best and potentially optimal combination ratio.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.261-262
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• 2023

Nanomaterials are being actively studied in the fields of cement and concrete. However, research on other nanomaterials is insufficient because much of the carbon-based nanomaterials are made up of carbon nanotubes. Therefore, in this study, carbon-based water-soluble graphene oxide was mixed into mortar according to the cement replacement rate to conduct a characteristic evaluation. As a result, as the substitution rate of graphene oxide increased, workability decreased, and there was no effect of enhancing compressive strength. In addition, it was confirmed that the compressive strength decreased due to a large amount of air bubbles when the mixture was mixed for the purpose of improving workability.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.2
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• pp.90-96
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• 2009

The high rising building construction makes increasing the requirement of high strength concrete. Especially, the workability analysis is related with dispersion of admixture such as SF for improving strength and FA, BS for reducing construction cost and improving durability of Ultra High Strength Concrete which has over 100 MPa of compressive strength is very important. Precisely, decreases dispersion because of lumping situation of each admixture and it causes the workability of admixture is decreased. Therefore, the workability of cement paste is tested for analyze effects of pre-mixed cement for solving those problems with it to this research. The summary of the results are like below. First of all, OBS is increasing workability more than OFS. This result causes that the glassy surface of BS in the OBS is increasing workability and the absorption of admixture of FA in the OFS is decreasing workability. In the case of mixing methods, pre-mixing method is increasing workability more than normal one. This result shows that the normal mixing method is bad dispersion of binders. The other side, the pre-mixing method is good. Furthermore, depending on the mixing time, according to the increasing mixing time such as 30, 60, and 120 seconds, the dispersion of binders and workability turns better.

• Journal of the Korean Ceramic Society
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• v.44 no.1 s.296
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• pp.43-51
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• 2007

Fluidity, setting time, hydration heat, bond water ratio, compressive strength, SEM and BET of OPC were measured by adding 1.0 wt% KCl and replacing 20 wt% mineral admixture in order to examine effects of blast furnace slag (BFS), limestone powder (LSP), and fly ash (FA) on fluidity and strength development of the cement contained much chloride. In general, the cement contained much chloride was high in heat of hydration, short in its setting time, low in its fluidity and low in its strength at 28 days due to the rapid hydration in its initial stage. As a result of the experiment, it has been demonstrated that fluidity became improved but the compressive strength at 28 days was decreased as replaced LSP to the cement contained much chloride. the fluidity and compressive strength at 28 days was improved as replaced BFS, the initial compressive strength development was improved due to the activation of initial reaction by KCl. Fluidity, initial compressive strength and late compressive strength at 28 days of cement contained much chloride replaced 5 wt% LSP and 15 wt% BFS concurrently was better than OPC, but the hydration heat was lower.

• Journal of the Korea Institute of Building Construction
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• v.21 no.1
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• pp.1-10
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• 2021

The purpose of this study is to evaluate the improvement of flow, compressive and flexural strengths of polymer cement mortar(PCM) using SBR latex mixed with blast-furnace slag and fly ash. The test specimens were prepared with SBR polymer dispersion, two types of admixture (blast-furnace slag and fly ash), five polymer-cement ratios (P/C; 0, 5, 10, 15 and 20%), and six admixture contents (0, 3, 5, 10, 15 and 20%), plain cement mortar was also made for comparison. From the test results, the flow of PCM was significantly improved compared to ordinary cement mortar, but the flow was slightly reduced when mixed with blast-furnace slag, and the flow was similar to PCM when mixed with fly ash. In addition, the compressive strength of PCM mixed with admixtures was significantly improved, but the flexural strength did not improve except for some mortars. It can be stated that the optimum mix proportions of PCM using SBR with admixture contents 10 to 15% and P/C 10% for the compressive strength improvement, and P/C 20% for flexural strength improvement are recommended respectively in this study.