Jong-Kyu Lee

Image and Phase Analysis of Low Carbon Type Recycled Cement Using Waste Concrete Powder

, recycling waste concrete to manufacture recycled aggregate or recycling waste concrete powder, which is the material for cement can be considered optimally environment-friendly practices. This study contributes to the aim of manufa cturinghigh value added materials that exploits the chemical properties of the waste concrete powder. From the research results, waste concrete powder is feasible to use to produce low carbon type recycled cement.키워드 : 저탄소형 시멘트, 콘크리트 미분말, 콘크리트 리사이클 Keywords : Low carbon type cement, Waste concrete powder, Recycled concrete* Corresponding author E-mail: songhun@kicet.re.kr

Physical Properties of Lightweight Materials According to the Replacement Ratios of the Admixture

Lightweight materials were fabricated using glass abrasive sludge, bottom ash and slag powder in this study. This study tried to draw the correlation between physical properties and internal pore of lightweight material. The content of bottom ash and slag powder was from 10% to 50% and firing temperature from 760℃ to 800℃ in rotary kiln. The lightweight material containing bottom ash or slag powder had a specific gravity of 0.21~0.70 at particle size 2~4 ㎜. Replacement ratio of the admixture increasing with specific gravity increased. Fracture strength of panel made with various lightweight materials was 32~55 ㎏f/㎠ and flexural strength was 11~18 ㎏f/㎠. Fracture strength increased by 72% and flexural strength was 63% compared with reference. Thermal conductivities of panel was 0.07~0.11W/m· k. The water absorption ratios of panel with lightweight materials containing bottom ash were 1.8~2.8% and slag powder were 2.65~2.8%. Excellent results on resistant of water absorption.

Leaching Properties of Water-Soluble Hexavalent Chromium in Manufacturing Cement Clinker Using Industrial By-Products

Since it was developed by Joseph Aspdin, cement has been a common construction materials up to the present time. However, there are trace constituents in cement clinker. One of the trace constituents included in cement clinker, chromium, has become prominent and highly noticed lately as a social issue both inside and outside of this country because it affects the human body negatively. The aim of the present study was to investigate the concentration of water-soluble hexavalent chromium in cement clinker by using industrial by-products. For that reason, raw materials were prepared to add different , , and sources. After the raw materials such as the limestone, the sand and the clay, iron ore was pulverized and mixed, and the raw meal was burnt at about in a furnace with an oxidizing atmosphere. The part in the raw materials of the clinker was substituted with slag, sludge, etc. and this was used to manufacturing cement clinker. To investigate the water-soluble hexavalent chromium content in clinker, raw meal was prepared by changing the modulus, the type, and the content of clinker materials and tested concentrations of hexavalent chromium in the clinkers. To determine formation of the clinker, tests were done with raw meals adding chromium by using different industrial by-products. Consequently because the chromium was to be included in the raw materials of the clinker, production of Portland cement clinker was included with the chromium. Also, the chromium was converted into hexavalent chromium in the burning process.

Hygroscopic Characteristic of Gypsum Boards Using Porous Materials

Active clays, Diatomite, bentonite and zeolite were used as porous materials for fabricating hygroscopic gypsum boards. Pohang active clay and Cheolwon diatomite showed excellent characteristics of moisture adsorption and desorption. These characteristics were caused by higher surface area and pore volume of porous materials. Moisture adsorption content of gypsum board with 10% active clay(P1) was 62.0 g/m, and moisture desorption content was 50.2 g/m. Moisture adsorption content of gypsum board with 10% diatomite(P) was 59.5 g/m, and moisture desorption content was 49.0 g/m. Moisture adsorption contents of gypsum boards with porous materials were higher than that moisture desorption contents of gypsum board without porous materials. Correlation coefficient between surface area and moisture adsorption content of gypsum boards was 0.98. Also, correlation coefficient between surface area and moisture desorption content of gypsum boards was 0.97. Moisture adsorption and desorption contents were influenced by surface area and pore volume of the gypsum boards, and surface area had a larger effect on moisture adsorption and desorption.

Property of Concrete Surface layer Using Self-Cleaning Silicate Concrete Impregnant

This study is interested in manufacturing the self-cleaning silicate concrete surface impregnant including tetra ethyl ortho silicate, lithium silicate for the repair of the exposed concrete surface and the color concrete requiring the advanced function in view of the concrete appearance. The concrete surface layer change and static contact angel was tested for the review of application. The result of this study shows that the effective silicate is tetra ethyl ortho silicate and lithium silicate. The adhesion in tension is satisfied with performance requirement of KS standard but the reinforcement of concrete substrate is slight. So, The self-cleaning silicate concrete impregnant of this study is more desirable for the improvement of durability rather than the reinforcement.

A Study on Fabrication and Characterization of Inorganic Insulation Material by Hydrothermal Synthesis Method (1)

In this study, the inorganic insulating material was fabricated with quartzite, ordinary portland cement(OPC), lime and anhydrous gypsum. After characteristic analysis of slurry, the optimum mixing ratio was derived with different CaO/SiO2 mole ratio. Based on derived mixing ratio, the inorganic insulating material was fabricated at different water content and hydrothermal synthesis conditions. Specific gravity was 0.26 g/cm 3 , compressive strength was 0.4 MPa, and thermal conductivity was 0.064 W/mK. This properties were enhanced performance of conventional ALC (Autoclaved Lightweight Concrete). And it can replace organic insulation with harmless inorganic insulation through continues research and development.

Leaching Properties of Water-Soluble Hexavalent Chromium by Manufacturing Condition of Cement Clinker

One of the trace constituents included in cement clinker, chromium, has become prominent and highly noticed lately as a social issue both inside and outside of this country because it affects the human body negatively. The purpose of the present study was to investigate leaching properties of water-soluble hexavalent chromium by different manufacturing conditions of cement clinker. Raw materials were prepared to add different , and sources. After the raw materials, such as limestone, sand and clay, iron ore was pulverized and mixed, and the raw meal was burnt at in a furnace with an oxidizing atmosphere. Leaching of soluble hexavalent chromium showed a tendency to decrease with an increasing LSF and IM. However, leaching of soluble hexavalent chromium increased with an increasing S.M. Alkali contents of iron source minerals is closely related to the leaching properties of soluble hexavalent chromium. Green sludge has the highest content of alkali added; leaching of water-soluble hexavalent chromium was mostly high. In order to reduce the water-soluble hexavalent chromium in cement, reducing the alkali content in raw materials is important.

Physical Properties of ALC with Various Fineness of Quartzite

ALC was fabricated using cement, lime and quartzite by hydrothermal reaction. ALC has low strength and brittleness on account of inner pores. The studies for resolving these problems were driven by many researchers. Among these researches, the controls of quartzite fineness have been studied for unsuitable properties of ALC. This study experimented with variation of 90 ㎛ residue for obtain good physical properties. It was found that 90 ㎛ residue influenced on physical properties of ALC. The lower amount of 90 ㎛ residue, the higher compressive and bending strength. But the continuing decrease of 90 ㎛ residue did not cause the increase of strength. In order to application of these results in process, the states of process and hydrothermal products will be considered.