• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.05a
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• pp.105-107
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• 2012

This study was conducted to investigate the strength development of fly ash concrete using the strength development estimation for the ready mixed concrete for construction of nuclear reactors. The findings are as follows. First, the higher the curing temperature becomes, the shorter the setting time becomes. In addition, the compressive strength also increased as the curing temperature gets higher. The apparent activation energy derived from ASTM C 1074 showed 34.75 KJ/mol. The results of concrete strength estimation confirmed that Gompertz model formula has good accuracy.

• KIEAE Journal
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• v.14 no.4
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• pp.133-138
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• 2014

The present study was carried out to assess the basic material properties and thermal behavior of light-weight foamed concrete panel mixed with PCM (Phase Changing Material). To do so, this study fabricated light-weight foamed concrete (1.0kg/m3) in pre-foaming method and mixed it with PCM micro capsule of 1-dodecanol and melamine to examine its physical and thermal properties. The results confirmed strength reinforcement effect by proper replacement ratio of fly-ash, which is an industrial by-product, and PCM. In addition, it found out that PCM-mixed light-weight foamed concrete had time delay and temperature reduction effect within the range of PCM phase transition according to the rise of outdoor temperature. It was also observed that the insulation performance of PCM-mixed light-weight foamed concrete was more dependent upon thickness than PCM replacement ratio.

• Journal of the Korea Concrete Institute
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• v.23 no.3
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• pp.311-320
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• 2011

Fly ash (FA), byproduct from power plant has been actively used as mineral admixture for concrete. However, since bottom ash (BA) is usually used for land reclaim or subbase material, more active reuse plan is needed. Pond ash (PA) obtained from reclaimed land is mixed with both FA and BA. In this study, 6 PA from different domestic power plant are prepared and 5 different replacement ratios (10%, 20%, 30%, 50%, and 70%) for fine aggregate substitutes are considered to evaluate engineering properties of PA as fine aggregate and durability performance of PA concrete. Tests for fine aggregate of PA for fineness modulus, density and absorption, soundness, chloride and toxicity content, and alkali aggregate reaction are performed. For PA concrete, durability tests for compressive strength, drying shrinkage, chloride penetration/diffusion, accelerated carbonation, and freezing/thawing are performed. Also, basic tests for fresh concrete like slump and air content are performed. Although PA has lower density and higher absorption, its potential as a replacement material for fine aggregate is promising. PA concrete shows a reasonable durability performance with higher strength with higher replacement ratio. Finally, best PA among 6 samples is selected through quantitative classification, and limitation of PA concrete application is understood based on the test results. Various tests for engineering properties of PA and PA concrete are discussed in this paper to evaluate its application to concrete structure.

• Journal of the Korea Concrete Institute
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• v.23 no.1
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• pp.49-55
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• 2011

The distresses of alkali-silica reaction (ASR) was recently reported at highway cement concrete pavement in Korea, which showed typical cracking and spalling patterns of ARS. Korea is was no longer safe zone against ASR, needding to find a control methodology against ASR. The purpose of this research was to provide a control methodology against ASR using mineral admixtures through a series of laboratory test program. Laboratory works included the accelerated mortar bar test (AMBT) by ASTM C 1260 regulation with five types of aggregate and three types of mineral admixtures (fly ash, ground granulated blast-furnace slag and silica fume). The result of ASTM C 1260 test for five types of aggregates without mineral admixtures showed that Siltstone and Mudstone were found to be "reactive." Tuff and Andesite-1 were found to be "possiblely reactive." In case of concrete mixed with 10, 20, and 30% fly ash, all specimens except Mudstone mixed with 10% FA were found to be "non-reactive". In cases of concrete mixed with 30, 40, and 50% ground granulated blast-furnace slag and 5, 7.5, and 10% silica fume, all specimens were found to be "non-reactive." These results could be selectively applied in constructions in Korea.

• Journal of the Korea Concrete Institute
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• v.28 no.3
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• pp.299-308
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• 2016

This paper presents an investigation of the mechanical and microstructural properties on hardened samples that were synthesized using blended binder(fly ash(FA) and blast furnace slag cement(BFSC)), alkali activator and sea water or distilled water. Binders were prepared by mixing the FA and BFSC in different blend weight ratios of 6:4, 7:3 and 8:2. Sodium hydroxide and sodium silicate were used 5 wt% of binder, respectively, as an alkaline activator. The compressive strength and absorption were measured at the age of 3, 7 and 28 days, and the XRD, TGA and MIP tests were performed at the age of 28 days. An increase in the content of BFSC leads to an increase in the quantities of ettringite and C-S-H formed, regardless of the type of mixing water. And it also shows higher strength due to the reduction of pores larger than ~50 nm. All hardened samples in this study have common hydration products of C-S-H, $Ca(OH)_2$ and calcite. Hydrocalumite of all reaction products formed was only present in hardened sample mixed with sea water. For each FA/BFSC mixing ratio, the compressive strength of hardened sample mixed with sea water was similar to that mixed with distilled water. It is proposed that the slight increase of strength of samples mixed with sea water is mainly due to the presence of hydrocalumite phase containing chlorine ion, contributing to the change of total porosity and pore size distribution in samples.

• Resources Recycling
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• v.30 no.1
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• pp.53-59
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• 2021

Waste vinyl generated from household waste has been used as a solid refuse fuel (SRF) due to the presence of impurities such as soil, metal, and glass; however, the amount of SRF used has been decreasing owing to recent environmental problems, thereby necessitating the need for recycling. In this study, the mixed recycled raw material produced from household waste vinyl and polyethylene (PE) single recycled raw material produced from agricultural waste vinyl were examined. Raw material analysis revealed that waste vinyl was mainly composed of polyethylene, and approximately 2% of ash remained in the mixed recycled raw material, whereas no ash was found in the PE single recycled raw material. In addition, the analysis of tensile strength according to the mixing ratio of the two recycled raw materials revealed that the highest tensile strength was approximately 16 MPa under the heat treatment temperature of 200 ℃, compression pressure of 30 MPa, and a mixing ratio of 3:7 (mixed:PE single). In addition, the highest bending strength was approximately 39 MPa under the heat treatment temperature of 200 ℃, compression pressure of 30 MPa, and a mixing ratio of 3:7 (mixed:PE single). Therefore, the possibility of recycling waste vinyl was suggested by investigating the change in strength characteristics according to the mixing ratio of the recycled raw materials.

• Korean Journal of Environmental Agriculture
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• v.20 no.4
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• pp.258-261
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• 2001

The paper industry produces about 6,000 ton of paper ashes yearly with by-products in Yuhan-Kimberly Ltd. The paper ashes was analyzed and evaluated for their potential as the soil acidity amendment materials. This study was conducted to investigate a reasonable amount of paper ashes for soil acidity amendment effect to be applied onto raising seedling of Calendula officinalis L. The mixed proportion of applied ashes, which was compared with agricultural lime, was treated to 0, 5, 10 and 15% (v/v) in mixed soil (pH 6.0) and the peat moss (pH 3.8) respectively. Consequently paper ashe was found to be more effective than agricultural lime at germination percentage, growth condition and in sharp initial increase of soil pH. The appropriate proportion of applied paper ash was 10% (v/v) at the soil-mix, and 15% (v/v) at the peat-moss. Soil application of paper ashes may provide supplemental quantities of K, Ca, Mg and other plant nutrients. But heavy metal concentrations in paper ash was low and should not limit application rates.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.2
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• pp.163-170
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• 2022

The present study investigates NO_x-removal and sound-absorption performances of photocatalytic porous concrete prepared by various TiO₂ application methods. Photocatalytic porous concrete samples were prepared by one of the following: 1) mechanically mixing TiO₂ during casting; 2) mixing bottom ash aggregate pretreated with TiO₂ during casting; and 3) spraying TiO₂ solution to the normally fabricated porous concrete. The test results indicated that the mechanical mixing of TiO₂ decreased the compressive strength as the added TiO₂ content increased. The use of pretreated bottom ash aggregate reduced the porosity, yet the compressive strength of the concrete was similar to that measured from the former method. Porous concrete samples sprayed with the TiO₂ solution exhibited enhanced compressive strength, while the porosity was analogous to those measured from other methods. The NO_x-removal performance was the highest in the samples sprayed with the TiO₂ solution, followed by the samples using pretreated bottom ash aggregate and mechanically mixed TiO₂. The samples with mechanically mixed TiO₂ identified a relationship between soundabsorption performance and porosity. However, no particular tendency was observable in the samples with other TiO₂ application methods.

• Journal of the Korean Ceramic Society
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• v.52 no.4
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• pp.253-263
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• 2015

Ordinary Portland cement is a widely favored construction material because of its good strength and durability and its reasonable price; however, spalling behaviour during fire exposure can be a serious risk that can lead to strength degradation or collapse of a building. Geopolymers, which can be synthesized by mixing aluminosilicate source materials such as metakaolin and fly ash, and alkali activators, are resistant to fire. Because the chemical composition of geopolymers controls the properties of the geopolyers, geopolymers with various Si:Al ratios were synthesized and evaluated as fire resistant construction materials. Rejected fly ash generated from a power plant was quantitatively analyzed and mixed with alkali activators to produce geopolymers having Si:Al ratios of 1.5, 2.0, and 3.5. Compressive strength of the geopolymers was measured at 28 days before and after heating at $900^{\circ}C$. Geopolymers having an Si:Al ratio of 1.5 presented the best fire resistance, with a 44% increase of strength from 29 MPa to 41 MPa after heating. This material also showed the least expansion-shrinkage characteristics. Geopolymer mortar developed no spalling and presented more than a 2 h fire resistance rating at $1,050^{\circ}C$ during the fire testing, with a cold side temperature of $74^{\circ}C$. Geopolymers have high potential as a fire resistant construction material in terms of their increased strength after exposure to fire.

• Magazine of the Korea Concrete Institute
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• v.11 no.2
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• pp.231-239
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• 1999

When the concrete is cast at the sea, there are lots of restrictions in the working process being different from in land, and the concrete is suffered from the physical and chemical action in terms of marine environment. The compressive strength was measured after antiwash out underwater concrete mixed with fly ash had been cast and cured in order to produce the endurable high performance concrete, and then its characteristic was discussed by comparing one cured in air with in fresh water, and the effect of fly ash usage under the properly controled sea water temperature of $15{\pm}3^{\circ}C$ was also covered. The present work showed that the proper usage of fly ash was obtained at the condition of around 10% of substituted binder weight under the structure required the early age strength, and at the condition of over 40% if considering its durability and economy.