• Journal of the Korean Ceramic Society
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• v.44 no.9
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• pp.502-509
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• 2007

This paper investigated how Fine Fly Ash (FFA) with $14,000\;cm^2/g$ of Fineness affects the micro structure and material properties of High-Performance Concrete (HPC) before and after hardening from Material Test of HPC and Cement Paste. FFA is applied as a substitute of Silica Fume which is used necessarily in producing HPC. As a Material Test results, 5% FFA series specimen shows the lower fluidity than SF series specimen. When, however, the Fluidity of 10% FFA series specimen is increased reversely to the similar value of SF series specimen. The Porosity of FFA series specimen of 3 day age is displayed to $21{\sim}24%$, which is higher than $19{\sim}20%$ porosity of SF series specimen, while that of 28 day age is reached to $8{\sim}9%$, which is improved compared with 10% fo SF series specimen. It can be thought that FFA has better influence on the porosity of HPC in case of long term age. The Compressive strength of FFA series specimen shows the similar result with the property of porosity. The compressive strength of 28 day age FFA series specimen is $98{\sim}106%$ of SF series specimen and 107% of plain specimen to reveal better strength development.

• Resources Recycling
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• v.26 no.3
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• pp.32-38
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• 2017

For the massive recycling of mine tailings, which are an inorganic by-product of mining process, in the field of civil engineering, pretreatments to extract heavy metals are required. This study focuses on the use of pre-treated tailings as substitute fillers for controlled low-strength material (CLSM). As a comparative study, untreated tailing, microwave-treated tailing and magnetic separated with microwaved tailing were used in this study. Cement contents amounting to 10%, 20% and 30% by the weight of the tailings were designed. Both compressive strength and flowability for all types of mixture were satisfied with the requirements of the American Concrete Institute (ACI) Committee 229, i.e., 0.3-8.3 MPa of compressive strength and longer than 200 mm flowability. Furthermore, all mixtures showed settlements less than 1% by volume of the mix.

• Journal of the Korea Institute of Building Construction
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• v.9 no.2
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• pp.77-83
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• 2009

In this study, a test has been carried out to solve the problem with ground granulated blast-furnace slag, low early strength & lack of supply and to find out a way to use as concrete admixture of the ultrafine blaine air cooling slag which is all disposed as the by product of air cooling slag and its test was conducted to the replacement rate of ultrafine blaine air cooling slag & mixing condition of every concrete admixtures by type for the purpose of obtaining later a basic data for practical use of the cement that used ultrafine blaine air cooling slag by conducting comparative analysis. If ultrafine-blaine air cooling slag is used to the concrete following the results, a high efficiency water reducing agent won't be needed much for flow acquisition due to a high increase in flow, and the stripping time of concrete form will be shortened thanks to the acquisition of early strength, And though, it has the problems with long term strength which is similar or a little lower than the 3 types of ground granulated blast-furnace slag, it's still applicable as the substitute materials for 3 types of ground granulated blast-furnace slag at 10, 15% replacement rate of ultrafine-blaine air cooling slag, at which it shows higher activation index than 3 types of ground granulated blast-furnace slag.

• KIEAE Journal
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• v.7 no.5
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• pp.135-142
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• 2007

This is an experimental study on the structural characteristics of reinforced concrete beams using of the oyster shells as a substitute fine aggregate of concrete. In this study, the main factors consist of the grain sizes and the percentage of substitution of oyster shells to fine aggregate in the equal water cement ratio. The results of the study showed as followed. The initial load value of them represented similar constant within 10% of the maximum load value in each test beam. But the maximum load value and the ultimate load value decreased with increased grain size and the rate of substitution. As the grain size of oyster shells became smaller, the load values of them were somewhat higher. The deflection among deformation properties of reinforced concrete beams with oyster shells represented typical curves like that of normal reinforced concrete. In the deformation of steel and concrete, the deformation was proportionated to the load till yield point and from yield point until approaching the ultimate load point. One type was typical curve of the load and the deformation and the other type irregularly was changed to very small deformation for the load increase centering around load axis. After the analyzing structural behaviors and the properties of reinforced concrete test beams with oyster shells, the most excellent grain size of oyster shells represented 1.0mm and less or 5.0mm and less with taking uniformly, and the percentage of practicable substitution of them to fine aggregate was about 30%.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.1
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• pp.48-55
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• 2022

This study uses the recovered water as mixing water and artificial lightweight aggregate pre-wetting water as part of a study to increase the recycling rate and reduce greenhouse gas of the ready-mixed concrete recovered during the concrete transport process, and cement fine powder of blast furnace slag(BFS) and fly ash(FA). The engineering characteristics of the three-component lightweight aggregate mortar used as a substitute were reviewed. For this purpose, the flow, dry unit mass, compressive strength, drying shrinkage, neutralization depth, and chloride ion penetration resistance of the three-component lightweight aggregate mortar were measured. When used together with the formulation, when 15 % of BFS and 5 % of FA were used, it was found to be positive in improving the compressive strength and durability of the mortar.

• Korean Journal of Materials Research
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• v.34 no.3
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• pp.175-183
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• 2024

Geopolymer, also known as alkali aluminum silicate, is used as a substitute for Portland cement, and it is also used as a binder because of its good adhesive properties and heat resistance. Since Davidovits developed Geopolymer matrix composites (GMCs) based on the binder properties of geopolymer, they have been utilized as flame exhaust ducts and aircraft fire protection materials. Geopolymer structures are formed through hydrolysis and dehydration reactions, and their physical properties can be influenced by reaction conditions such as concentration, reaction time, and temperature. The aim of this study is to examine the effects of silica size and aging time on the mechanical properties of composites. Commercial water glass and kaolin were used to synthesize geopolymers, and two types of silica powder were added to increase the silicon content. Using carbon fiber mats, a fiber-reinforced composite material was fabricated using the hand lay-up method. Spectroscopy was used to confirm polymerization, aging effects, and heat treatment, and composite materials were used to measure flexural strength. As a result, it was confirmed that the longer time aging and use of nano-sized silica particles were helpful in improving the mechanical properties of the geopolymer matrix composite.

• Advances in concrete construction
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• v.17 no.5
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• pp.293-310
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• 2024

Ultra-high-performance fiber-reinforced concrete (UHPFRC) is a form of cement-based material that has a compressive strength above 150 MPa, excellent ductility, and superior durability. This composite material demonstrates innovation and has the potential to serve as a viable substitute for concrete constructions that are subjected to harsh environmental conditions. Over many decades, extensive research and progressive efforts have introduced several commercial UHPFRC compositions globally. These compositions have been specifically designed to cater to an increasing variety of applications and meet the rising need for building materials of superior quality. However, the effective manufacturing of UHPFRC relies on the composition of its materials, especially the inclusion of fiber content and the proportions in the mixture, resulting in a more compact and comparatively uniform packing of particles. UHPFRC has notable benefits in comparison to conventional concrete, yet its use is constrained by the dearth of design codes and the prohibitive expenses associated with its implementation. The study demonstrates that UHPFRC presents a viable, long-lasting option for improving sustainable construction. This is attributed to its outstanding strength properties and superior durability in resisting water and chloride ion permeability, freeze-thaw cycles, and carbonation. The analysis found that a rheology-based mixture design technique may be employed in the production of UHPFRC to provide enough flowability. The study also revealed that the use of deformed steel fibers has shown enhanced mechanical qualities in comparison to straight steel fibers. However, obstacles such as higher initial costs, the requirement for highly specialized personnel, and the absence of comprehensive literature on global UHPFRC standards that establish minimum strength criteria and testing requirements can hinder the widespread implication of UHPFRC. Finally, this review attempts to deepen our foundational conception of UHPFRC, encourages additional study and applications, and recommends an in-depth investigation of the mechanical and durability properties of UHPFRC to maximize its practicality.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.1
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• pp.73-82
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• 2009

Injectable calcium phosphate cement (CPC) has been used as bone substitute successfully due to good biocompatibility and osteoconductivity. One of the important mechanical characteristics of CPC is flowablility, which can be evaluated by measuring rheological parameters. However, there have been few studies that measured rheological properties of CPC. The purpose of this study was to evaluate the effects of temperature and concentrations of 2 kinds of setting solutions, hydroxyprophyl methylcellulose (HPMC) and polyacrylic acid (PAA), on rheological properties of CPC. The CPC used was dicalcium phosphate dihydrate (DCPD). Rheological properties of CPC paste were measured using rheometer. The effect of concentrations of each solution (2% and 1% HPMC and 35% and 17.5% PAA) was evaluated. The effect of temperature ($25^{\circ}C$ and $37^{\circ}C$) on the rheological properties of CPC was also investigated. The statistical analysis was carried out with Mann-whitney test with Bonferronis collection. CPC with both setting solutions showed shear thinning behavior. Higher concentrations of setting solution (2% HPMC and 35% PAA) produced significantly higher viscosity than lower concentrations of setting solution (1% HPMC and 17.5% PAA). CPC with HPMC showed significantly higher viscosity at $37^{\circ}C$ that at $25^{\circ}C$. CPC with PAA showed lower viscosity at $37^{\circ}C$ than at $25^{\circ}C$, although the difference was not statistically significant. The results showed that CPC with HPMC or PAA solutions are pseudoplastic and the concentrations of setting solutions and temperature may have an effect on the rheological properties of CPC paste. These results showed that the flowability of injectable CPC could be improved by use of increasing frequency of oscillation. In clinical practice, the use of ultrasonic vibration would be helpful in application of injectable CPC. CPC with HPMC could be more easily applicated at $25^{\circ}C$ than $37^{\circ}C$. The use of lower concentrations of HPMC and PAA solution would be beneficial in terms of flowability.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.4
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• pp.71-78
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• 2012

Recycled aggregates are made from construction wastes, and they have many national and social benefits by saving energy, developing substitute resources, and protecting environment. However, low-quality recycled aggregate with low density and high absorption rate cannot be used for structural concrete aggregate but is used mainly for low added value. Therefore, this study aims to identify the characteristics of the materials of recycled aggregates made after crashing and pulverizing waste concrete. For this, their major physical characteristics of cement content, absolute dry density, absorption rate, etc. were reviewed to make a mix design (draft) for the production of the secondary product and performance evaluation was done on the bending strength, absorption rate, bending strength after freezing and thawing, compressive strength, air-dried gravity, etc. of the test products produced by applying the mix design to compare the results with the quality standards of GR mark. The results of the tests showed that the substitution rate of recycled aggregate increased to 50~90 %, which is of superior quality than the performance standards of GR F 4007. Therefore, it is thought that they can be used for various construction works with certain physical characteristics applicable to the production of secondary concrete products using recycled aggregates.

• Journal of the Korea Institute of Building Construction
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• v.18 no.4
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• pp.321-327
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• 2018

Blast furnace slag has been actively used as a substitute for cement in the construction field with high value-added through resource recycling research. However, most of the slag cannot find a clear recycling purpose. This is because some slags contain unstable materials and are used for road-use asphalt and embankment, which are low value-added materials. Electric arc furnace reduction slag(ERS) has been reported to contain a large amount of unstable free CaO due to deoxidation and component adjustment. In this study, free CaO of ERS which is generated in Korean steelmakers is quantitatively evaluated by using ethylene glycol method. As a result of free CaO quantitative evaluation of ERS, it was confirmed that there is a big difference according to the location of each field. In addition, ERS generally existed in powder form as undifferentiated characteristics, but it was confirmed that free CaO content was different due to hydration product in aggregate form due to water treatment. In addition, free CaO is an amorphous material and its crystallization characteristics are different due to the influence of temperature when it is cooled. ERS requires a long-term aging period as it contains a lot of free CaO.