• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.793-797
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• 2005

This study was undertaken to examine the feasibility of recycling waste concrete fine aggregate to prepare polymer-modified mortars. The specimens of polymer-modified mortars were prepared by using styrene-butadiene rubber(SBR) latex and polyacrylic ester(PAE) emulsion as a polymer modifier. The formulations for specimens were prepared with various replacing ratios of waste concrete fine aggregates as parts of standard sand and various polymer cement ratios. For the evaluation of the performance of polymer-modified mortars, various physical properties were investigated. As a results, water cement ratio of polymer-modified fresh mortars increased with an increase of recycled fine aggregate, but decreased with an increase of polymer modifiers. The compressive and flexural strengths of polymer-modified mortars decreased with an increase of recycled fine aggregate, but flexural strengths increased with an increase of polymer modifiers.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.81-87
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• 2003

The purpose of this study is the development of a recycling process to recover the hydrated ability of cement hydrate which accounts for a large proportion of cementitious powder by concrete waste in order to recycle cementitious powder by concrete waste as recycle cement. Therefore, after having theoretical consideration based on the properties of high-heated concrete, we consider the properties of hydration of cementitious powder in hardened mortar under various temperature conditions. As a result of experiment, it is revealed that an effective development of recycling cement is possible since the cementitious powder by concrete waste recovers a hydraulic property during burning at $600^{\circ}C$ or $700^{\circ}C$. And it is shown that the fluidity of mortar decreases rapidly as the burning temperature of recycle cement increases. however, the improved effect of fluidity is predominant if adding the additive such as fly-ash or blast furnace slag.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.88-94
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• 2011

To make recycling aggregate, quantity of fine particles increase due to multi-crushing. Though this particles were mixed with recycling aggregate, those have to be disparted from aggregate in the high quality recycling aggregate, because of the cause of low quality. Considering reactivity, fine particles is better than coarse one. Therefore, it needs to develop suitable usage. We try to make cement extruding material by using the fine particles from concrete recycling, as a silicious replacement. Test results are as follows ; 1) Waste concrete powder has major ingredients such as $SiO_2$ and CaO, its density is $2.45g/cm^3$ being similar to silica powder, its diameter is range 13 to $141{\mu}m$. 2) Considering to strength properties according to particle size, specimen was made using small particles is higher strength than large one. 3) Despite of exception in the autoclaved curing, when the replacement of waste fine particle increase, strength of extruding panel shows almost same level.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.3
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• pp.286-293
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• 2020

In this study, we tried to verify the correlation of the amount of combustible industrial by-products, household waste used as fuels on cement sintering process and the amount of NOx, and CO, harmful components in the exhaust gas. The analysis uses coal as natural fuel, soft plastics (plastics with properties that tend to be scattered by wind, such as vinyls), hard plastics (plastics with properties that are not scattered by wind, such as PETs, wate rubbers), and reclaimed oils as alternative fuels. Utilizing the response surface analysis (RSM) technique using the process data of 2019, such as the fuel input and combustion temperature of a domestic A cement manufacturer's sintering facilities as independent variables, and the NOx, and CO emissions to the stack as dependent variables. Correlation was analyzed. As a result, it was confirmed that the impact on the emission material differs for each waste. In particular, it was analyzed that the hard plastics increase the CO emission but have an excellent effect of reducing NOx.

• Journal of the Korea Institute of Building Construction
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• v.8 no.4
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• pp.79-85
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• 2008

The purpose of this study is to evaluate the mix design of pH reducing cement concrete which can be used for environment-friendly concrete. Cement pastes and concretes are prepared with water-binder ratios and various admixtures such as blast-furnace slag, fly ash and recycled cement, and tested for compressive strength and pH. pH is measured through pore solution expressed from hydrated cement paste by special apparatus. From the test results, regardless of water-binder ratio, The pH of expressed pore solution from hydrated cement paste which is made of ordinary portland cement with blast-furnace slag, fly ash is decreased with increasing of admixtures content, and compressive strength is also slightly improved. The compressive strength of cement paste made of recycled cement which is burnt at $1000^{\circ}C$, for 2 hours is considerably increased compared with that of none-burnt recycled cement due to restoration of hydraulic property, but pH is a little higher. Porous concrete with ordinary portland cement has high pH in the range of 12.22 to 12.59, however, that is reduced to the range of 8.95 to 10.39 by carbonation at the surface of porous concrete. The pH reduction of porous concrete is possible by various admixture addition, however their degrees are very slight. Therefore, to reduce the pH considerably, carbonation method of porous concrete is better in pH reduction methods for plant survival condition of pH of 9.0 or less. In this study, it is apparent that pH for the environment-friendly porous concrete products used in the construction field can be suppressed by this carbonation method and various admixtures addition.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.3
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• pp.88-93
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• 2011

To resolve the problem which is demand and supply imbalance of fine aggregate by the shortage of natural fine aggregate and the environment regulations, the studies for the application of recycled fine aggregate made from waste concrete have been recently carried out. The objective of this study is to shed light on the mechanical properties and durability performance of concrete using recycle fine aggregate with various water to cement ratios and unit water contents. And it is intend to propose the fundamental data for structural application of recycled concrete. In particular, the effects according to the variations of water to cement ratios and unit water contents in recycled concrete with recycled fine aggregate replacement of 100 percent are discussed by the test results, such as air content, slump, time of set, compressive strength, tensile strength, carbonation, chloride penetration.

• Journal of the Korea Institute of Building Construction
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• v.15 no.1
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• pp.9-16
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• 2015

The goal of this research was evaluating and suggesting the solution of preventing carbonation of concrete replaced high-volume of slag. The concrete mixtures were prepared with high-volume slag and recycled aggregate, and the concrete samples were evaluated the carbonation depth with various surface treatment methods. For various surface treatment methods and surface protecting sheets, bonding strength and carbonation depth were measured. Basically, from the results, the carbonation of concrete was completely prevented with any type of surface treatment method and surface protecting sheet as far as the surface treatment materials were remained. Therefore, in this research, it was known and suggested that the easiness of handling and sufficient bonding performance was much important than the quality of surface protecting sheets.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.3
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• pp.152-159
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• 2010

Recently, the public interest in eco-friendly material and structure has been increasing and many Hwang-toh researches are being actively performed. Hwang-toh is one of the traditional environment friendly construction materials used as a construction and plastering material. Hwang-toh has many advantages as construction material due to its high heat storage capacity, auto-purification, antibiotic ability, and infrared ray emission characteristics. But, currently it has not been developed into construction material and used in modern construction due to its low strength and dry shrinkage cracking prone characteristics. According to the recent researches and study results, Hwang-toh can be used as a natural pozzolanic material like fly-ash or pozzolan. In this study, mechanical properties and structural flexure behavior experiments of slag, recycled PET fiber, and Hwang-toh added concrete are carried out. The test results showed that drying shrinkage of concrete mixed with Hwang-toh has lower compressive strength and elastic modulus than those of control cement concrete specimen, but it has the similar flexural behavior in reinforced concrete beams.

• Journal of the Korean Ceramic Society
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• v.40 no.8
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• pp.804-810
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• 2003

The fine powder produced by heating and grinding of the waste concrete in the waste construction was investigated whether utilize as substitution raw material of SiO$_2$, CaO, and Al$_2$O$_3$ source for OPC clinker manufacture is possible or not. In order to synthesize OPC clinker, limestone, shale, converter slag and fly ash were used as main raw materials, and modulus was fixed LSF 91.0, SM 2.60, IM 1.60. The synthesized clinkers were characterized. The Main products of synthesized clinker were C$_3$S, ${\beta}$-C$_2$S, C$_3$A, C$_4$AF as OPC clinker at 1,43$^{\circ}C$. As a result of TG-DTA and burnability index(B.U) analysis of each raw mixtures, the formation temperature of clinker phases was similar and B.I was showed easy burning as 48.6∼51.4.

• Journal of the Korea Institute of Building Construction
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• v.5 no.3 s.17
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• pp.109-116
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• 2005

Recently, there have been many studies seeking towards the utilization of cementitious powder from concrete waste as recycled cement. However, most of the studies actually have been researches about the reuse of mortar or paste, not concrete waste. In fact, either mortar or paste is quite different from a real concrete waste in terms of age and mixture. Thus the purpose of this study is to examine basic physical properties of recycled cement, manufactured with cementitious powder from concrete waste, and analyze differences in chemical and hydraulic properties of the cement and its tested model. As a result of the chemical analysis, recycle cement is composed mainly of CaO and $SiO_2$, and that it is even lower in the content of CaO than Portland cement, which is also supported by previous studies. But, Differently from previous studies, calcining temperature of 650 was found an optimal condition under which cementitious powder from concrete waste could restore its hydraulic properties.