• Journal of the Korea Institute of Building Construction
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• v.14 no.2
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• pp.187-194
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• 2014

With environmental regulations continuously being strengthened internationally the need to control environmental pollution and environmental load is emerging in Korea. The purpose of this study is to seek methods or using waste cementitious powder as an alternative raw material for limestone through the optimization of raw material and to quantitatively analyze the resulting reduction of $CO_2$ emission in order to contribute to solving the issue of waste, which is the biggest issue in relation to construction and global warming. The results of the study, show that waste cementitious powder can be used as an alternative raw material for limestone at OPC level, but it was also found that mixing fine aggregate cementitious powder into waste cementitious powder significantly affected the substitution rate for limestone with waste cementitious powder and the reduction of greenhouse gas. In particular, when fine aggregate cementitious powder was used at a rate of 0~20%, the substitution rate for limestone and the reduction in the rate of greenhouse gas emission was significantly reduced. It is thought that a technique to efficiently separate and discharge the fine aggregate cementitious powder mixed in waste cementitious powder needs to be developed in the future.

• Journal of the Korea Institute of Building Construction
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• v.14 no.1
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• pp.54-60
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• 2014

The purpose of this study is to examine whether cementitious powder separated from waste concrete can be used as an alternative raw material to limestone and reduce the usage of natural resource (limestone) and $CO_2$ emission based on recycling cementitious powder from waste concrete. Experiments actually analyzed the chemical composition of cementitious powder and performed hyperthermia analysis, measurement of free CaO and XRD analysis to measure the degree of recovery of hydration in the model of cementitious powder manufactured based on chemical composition. These were performed in each cementitious powder model at different calcination temperatures such as $900^{\circ}C$, $1200^{\circ}C$, $1300^{\circ}C$, $1400^{\circ}C$ and $1450^{\circ}C$. Through the experiments, it was found that the recovery of hydration was at a level which can be used as the alternative raw material for limestone, but the replacement ratio was directly affected by the degree of mixing of fine aggregate in less than $150{\mu}m$, which cannot be separated from cementitious powder. It was shown that there was no difference in the production of compounds involved in hydration at calcination temperatures of $1200^{\circ}C$ or higher. Therefore, to pursue the replacement of limestone and reduction of greenhouse gas by recycling cementitious powder, the development of technology to efficiently separate aggregate fine powder is required.

• 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.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.47-48
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• 2014

This study is to hydration property of low carbon type recycled cement from waste cementitious powder and cement raw materials. Waste cementitious powder possible to low carbon type recycled cement in small part of additive materials. Also, low carbon type recycled cement using waste cementitious powder is suitable for low heat type cement.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.11a
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• pp.77-82
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• 2003

The purpose of this study is development of technique to use cementitious powder as recycle cement produced from deteriorated Concrete waste which has a large quantity of calcium carbonate. Therefore, after having theoretical consideration based on the properties of high-heated concrete and concerning about neutralization of Concrete, we analysis chemical properties of ingredients of cementitious powder. After making origin cement paste, then processing the accelarated carbonation, we consider the properties of hydration and chemical properties of cementitious powder under various temperature conditions. As a result of the thermal analysis, the CaCo3 content of cementitious powder would affect decision of heat temperature to recover its hydrated ability because CaCo3 content is increased when neutralization is progressed. And as a result of XRD analysis, in case of origin powder of non-neutralized paste, CaO peak is found at 700℃. but, heat temperature to generate CaO would increase when the content of neutralized ingredients is increased. Finally, recycle cement heated at 700℃ shows the best compressive strength when the content of neutralized ingredients in recycle cement is less then 50%. However, it would be quite difficult to manage quality of recycle cement according to recycling points of various concrete waste.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.77-82
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• 2003

The purpose of this study is development of technique to use cementitious powder as recycle cement produced from deteriorated Concrete waste which has a large quantity of calcium carbonate. Therefore, after having theoretical consideration based on the properties of hish-heated concrete and concerning about neutralization of Concrete, we analysis chemical properties of ingredients of cementitious powder After making origin cement paste, then processing the accelerated carbonation, we consider the properties of hydration and chemical properties of cementitious powder under various temperature conditions As a result of the thermal analysis, the CacO3 content of cementitious powder would affect decision of heat temperature to recover its hydrated ability because CacO3 content is increased when neutraliTation is preBlessed. And as a result of XRD analysis. in case of origin powder of non-neutralized paste, CaO peak is found at $700^{\circ}C$. but, heat temperature to generate CaO would increase when the content of neutralized ingredients is increased. Finally, recycle cement heated at $700^{\circ}C$ shows the best compressive strength when the content of neutralized ingredients in recycle cement is less then 50%. However, it would be quite difficult to manage quality of recycle cement according to recycling points of various concrete waste.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.11a
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• pp.39-40
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• 2011

This study is to analyse possibility cementitious powder from waste concrete as row material of recycled cement. From the results, we ascertained possibility as recycled cement through XRF & XRD of cementitious powder & recycled cement. As a result of the experiment, cementitious powder from waste concrete, which appeared to recovery hydration chemically at the calcining temperature of 700, suggested highly possibility as recycled cement.

• Journal of the Korea Institute of Building Construction
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• v.4 no.4
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• pp.79-86
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• 2004

The purpose of this study was the development of a recycling process to recover the hydraulic properties of hydration products which account for a large proportion of cementitious powder from concrete waste. This process was performed to recycle cementitious powder as recycle cement. Therefore, after the theoretical consideration of the properties of recycle process of recycled aggregates and cementitious powder, we investigated the hydraulic properties of cementitious powder under various temperature conditions in hardened mortar which was modeled on concrete waste. And we analyzed properties of chemical reactions of recycled cement with admixture materials such as Fly-Ash, Blast Furnace Slag As a result of the experiment, the most effective method to recover hydraulic properties of the cementitious powder from concrete waste was condition of burning at 700℃ for 120 minute. And it is shown that the fluidity of mortar was decreased rapidly when the burning temperature of recycle cement was increased. However, the compressive strength and fluidity were improved significantly when admixture materials such as Fly-Ash or Blast Furnace Slag was added.

• Journal of the Korea Institute of Building Construction
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• v.4 no.3
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• pp.143-151
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• 2004

The purpose of this study is development of technique to use cementitious powder as recycle cement produced from deteriorated Concrete waste which has a large quantity of calcium carbonate. Therefore, after having theoretical consideration based on the properties of high-heated concrete and concerning about neutralization of Concrete, we analysis chemical properties of ingredients of cementitious powder. After making origin cement paste, then processing the accelarated carbonation, we consider the properties of hydration and chemical properties of cementitious powder under various temperature conditions. As a result of the thermal analysis, the $CaCO_3$ content of cementitious powder would affect decision of heat temperature to recover its hydrated ability because $CaCO_3$ content is increased when neutralization is progressed. And as a result of XRD analysis, in case of origin powder of non-neutralized paste, CaO peak is found at $700^{\circ}C$. but, heat temperature to generate CaO would increase when the content of neutralized ingredients is increased. Finally, recycle cement heated at $700^{\circ}C$ 120min. shows the best compressive strength when the content of neutralized ingredients in recycle cement is less then 50%.

• Environmental Engineering Research
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• v.21 no.4
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• pp.341-349
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• 2016

To improve the utilization rate of construction waste as mine backfilling materials, this paper investigated the feasibility of using recycled powder as mine paste backfilling cementitious material, and studied the pozzolanic activity of recycled construction waste powder. In this study, alkali-calcium-sulfur served as the activation principle and an orthogonal test plan was performed to analyze the impact of the early strength agent, quick lime, and gypsum on the pozzolanic activity of the recycled powder. Our results indicated that in descending order, early strength agent > quick lime > gypsum affected the strength of the backfilling paste with recycled powder as a cementitious material during early phases. The strength during late phases was affected by, in descending order, quick lime > gypsum > early strength agent. Using setting time and early compressive strength as an analysis index as well as an extreme difference analysis, it was found that the optimal ratio of recycled powder cementitious material for mine paste backfilling was recycled powder:quick lime:gypsum:early strength agent at 78%:10%:8%:4%. X-ray diffraction analysis and scanning electron microscope were used to show that the hydration products of recycled powder cementitious material at the initial stages were mainly CH and ettringite. As hydration time increased, more and more recycled powder was activated. It mainly became calcium silicate hydrate, calcium aluminate hydrate, etc. In summary, recycled powder exhibited potential pozzolanic activities. When activated, it could replace cementitious materials to be used in mine backfill.