• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.477-482
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• 2016

This study investigates the expressions characteristics of compression strength depending on the condition of fresh concrete and cured concrete by producing Non-cement mortar and concrete only with solidified sludge in the dehydrated cake form, recycled concrete and premixed materials(BS, FA) in order to actively use remicon recycling water as resources, rather than as construction waste material. After treating wastewater of pH 12.5 or more with alkali activator and after promoting BS hydration reaction, the amount of BS inflow was found to be increased and compression strength was increased accordingly: these results coincide with the analysis results of TG-DTA and SEM.

• Journal of the Korea Institute of Building Construction
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• v.20 no.5
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• pp.391-397
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• 2020

This study is to compare and analyze the strength, drying shrinkage and carbonation properties of lightweight aggregate mortar using recycling water as prewetting water and mixing water. The flow, compressive strength, split tensile strength, drying shrinkage and carbonation depth of lightweight aggregate mortar with recycling water were measured. As test results, the mortar flow was similar in all mixes regardless of the recycling water content. The compresseive strength of the RW5 mix with 5% recycling water as prewetting water and mixing water was the highest value, about 53.9 MPa after 28 days. In addition, the tensile strength of lightweight mortar was about 3.4 to 3.8 MPa, indicating 7 to 9% of the compressive strength value regardless of recycling water content. In the case of drying shrinkage, the RW2.5 mix using 2.5% recycling water showed the lowest shrinkage rate as about 0.107% at 56 days. The drying shrinkage of the plain mix without recycling water was relatively higher than the RW2.5 and RW5 mix. The RW5 mix showed lowest carbonation depth compared to other mixes. In this study, the RW5 lightweight aggregate mortar with 5% recycling water exhibits excellent compressive strength and carbonation resistance. Therefore, it is considered that if the recycling water, a by-product of the concrete industry, is properly used as prewetting water and mixing water of lightweight mortar and concrete, it will be possible to increase the recycling rate of the by-product and contribute to improve the property of lightweitht aggregate mortar and concrete.

• 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.

• Economic and Environmental Geology
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• v.57 no.2
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• pp.177-184
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• 2024

This study was conducted to find a way to reduce the production of cakes generated in the domestic aggregate production process. Cakes from 8 wet aggregate producers were collected and particle size was analyzed. Samples were collected step by step from an aggregate producer A, particle size analysis was performed, and the material balance was calculated before and after an sand recovery unit by modeling the production process. As a result of the particle size analysis of eight cakes, one sample contained 50% sand, and the rest contained about 5% to 25% sand. The results showing that the cake contained a variety of sand in cakes may indicate that the recovery efficiency of the sand recovery units in the field varied. Sieve analysis of the samples showed that the generation of sand particles increased 2.8 times during the third crushing compared to the second crushing, and more cake particles were generated. As a result of simulating the sand recovery unit model, the lower the cut point of the cyclone and dewatering screen, the higher the sand production and the less cake production appeared. In order to reduce the production of cake in the field, it was determined that an optimal operation of the sand recovery unit was necessary in the aggregate production process.

• Journal of the Korea Organic Resources Recycling Association
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• v.26 no.1
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• pp.29-37
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• 2018

In this study, optimum extraction conditions for phosphorus recovery from sewage sludge ash(SSA) were investigated. For this purpose, an experiment was conducted to determine optimal recovery conditions for Ca-P type phosphorus by using calcium component in the recycled aggregate residue. The phosphorus content of sewage sludge ash was confirmed to be 5.0 %. When $H_2SO_4$ was used as an extract, concentration of 1 N $H_2SO_4$, L/S ratio of 10, and extraction time of 30 min were found to be the optimal extraction conditions. Phosphorus was extracted by using optimal extraction conditions, and then the heavy metals eluted with phosphorus were removed using 1~20 g of cation exchange resin. In 20 g of cation exchange resin, Fe 71.3%, Cu 82.4%, Zn 79.9%, and Cr 15% were removed. After that, the mixing ratio of the calcium extract obtained from the recycled aggregate residue (RAR) was changed to 1:1, 1:5, 1:10. The pH of the SSA to RAR mixture was adjusted to 2, 4, 8 and 12 by the addition of 5 N NaOH to the mixture of 1:5, and the phosphorus was recovered as Ca-P type precipitate. The optimum pH was 8. When recycled aggregate residues were used, the weight of calcium phosphate increased, but the amount of wastewater generated also increased. Therefore, it was concluded that the use of recycled aggregate residue was not economically feasible.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.1
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• pp.85-91
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• 2021

Aggregate waste separator with rotating separating net was designed for applying classification process of construction waste. In order to evaluate the performance of the aggregate waste separator, according to the type of waste, standardized waste samples are prepared using acrylic. The appropriate operating point was evaluated by the classification efficiency and misclassification rate of recycled aggregate according to the control frequency of the blower operating and inlet position of the separating net. The classification efficiency at the operating point of the aggregate waste separator was evaluated through flow analysis assuming recycled aggregate and waste sample as particles. As a result of the performance test, when the distance. between the conveyor belt and the inlet was 0.2m, the classification efficiency was 95%, but the misclassification rate of recycled aggregate was 2% or more, which satisfies the classification efficiency and the misclassification rate of less than 2%. The operating point was shown at a control frequency of 58Hz at a suction distance of 0.254m. As a resu lt of flow analysis, there was no misclassification of recycled aggregate. In order to redu ce constru ction waste in the existing recycled aggregate production process, adsorption system using a rotating separating net that can be operated as an installation type was built.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.458-465
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• 2017

The purpose of the present study was to examine the method of physically processing oyster shells for use as raw material(aggregate) through experimentation. The results of the experiment found that the adequate particle size of the pulverized oyster shells should be smaller than 10mm due to their shape. Also, after considering various particle size distributions and residual rates by particle size, the study found the cutter mill to be the most suitable tool for pulverizing oyster shells. The use of a cutter mill resulted in recovery rates of 97.3%, 98.2%, and 98.9% for inner screens of 8mm, 12mm, and 20mm respectively, revealing how the increase of screen size results in slightly higher recovery rates. The experiment involving the difference between the inner screen of the cutter mill and the speed of the inverter shows that a smaller screen size and a faster inverter speed result in a lower fineness modulus, while a rise in inverter speed for an identical screen made possible the material recovery of a much lower range of particle sizes.

• Resources Recycling
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• v.8 no.1
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• pp.44-51
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• 1999

Converter slag was reduced and modified by the simultaneous addition of carbon and waste foundry sand as a $SiO_2$ source. The basic properties such as phase distribution, composition, specific density, hardness. absorption of water and compressive strength of modified slags were measured. The Iron recovery was significantly affected by the basicity of slag. The properties of slow cooled-modified slags of basicity 1.34 arc very similar to the natural aggregates.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.153-154
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• 2019

In this study, the fluidity and compressive strength of lightweight mortar using recycling water for pre-wetting of artificial lightweight aggregate were compared and analyzed to maximize the utilization of the recycling water, which is a by-product of the Ready-Mixed Concrete industry. For this purpose, the pre-wetting water was replaced with recycling water at the ratio of 0, 2.5, 5, 7.5 and 10%.

• Magazine of RCR
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• v.4 no.2
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• pp.50-52
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• 2009