• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.3
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• pp.161-168
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• 2023

Converter slag is a by-product generated by refining the pig iron produced into molten steel in the blast furnace, occupying about 15 % of the weight of steel production. It has a high free-CaO content that can generate expansion cracks when used for concrete aggregate. This is the main reason to make it difficult to recycle. To solve this problem, government guideline requires that converter slag has to be aged in an open yard for 90 days. However, aging can not be perfectly performed because it entails time and cost. In this study, we tried to investigate the applicability of converter slag as a cementitious material rather than an aggregate by mixing converter slag with mortar formulations. According to the EDS results of the converter slag in the experiment, we found that screening in the aggregate phase was more effective than that in the powder phase. When the particles separated by a magnet in the aggregate state were pulverized and used for concrete up to a 15 % replacement ratio, various engineering characteristics, such as flow, length change, and compressive strength, showed engineering characteristics similar to those of the control mix.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.777-780
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• 2008

There were some attempt to reuse water with sludge combinative water for ready mixed concrete. But recycling water consist of cement, aggregate and chemical admixture. So it caused deterioration of concrete. The object of this study was to search for recycling method of the recycling water sludge as mineral admixture. This experiment dealed with the effect of $2.5{\sim}12.5$% range of the recycling sludge which can be used for admixture binder(BFS, FA, BFS+FA) on properties of activated recycling water sludge for admixture of concrete. As a result, Although the slump levels reduced and air contents increased as sludge replacement levels increased, it didn't change highly. The compression strength of concrete slightly increased with an increasing amount of recycling water sludge replacement.

• Journal of the Korea Concrete Institute
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• v.20 no.5
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• pp.549-555
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• 2008

In this paper, the applicability of Hwangtoh, as an alternative of cement paste, is investigated for the solution of internal heat and shrinkage caused by the hydration of cement paste. Several small-sized specimens of Hwangtoh and ordinary portland concrete (OPC) were compared as to compressive strength, heat of hydration, and shrinkage strain. Moreover, the applicability to the construction structures was reviewed through the test of large-size specimens. The 28-day compressive strength of Hwangtoh concrete (HBC), ranged 18 to 33 MPa, can reach that of OPC. Not only the maximun internal temperature of HBC was read about 1/4 of OPC as it is cured, but also its shrinkage decreased more than the OPC did. Therefore, Hwangtoh binder is more favorable than cement binder in terms of its hydration heat and shrinkage under the construction of concrete.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.1
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• pp.25-30
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• 2016

The purpose of this study is to investigate experimentally the effect of reinforcement of polyetylene fiber, inclusion of silica sand, and replacement of cement with fly ash on the compressive and tensile behavior of fiber reinforced composite. Five types of mixture proportions were determined and compressive strength and uniaxial tension tests were performed. Test results showed that strength, ductility, and control of cracking were improved by the reinforcement of fiber. Although the strength was improved by the inclusion of dried silica sand, the ductility was reduced and the crack width was increased. On the other hand, the increase of ductility, the decrease of crack width, and the decrease of strength were observed by the replacement of cement with fly ash.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.2
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• pp.101-107
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• 2022

This study proposes the deconvolution method for the nanoindentation test results of geopolymer employing the Gaussian mixture model. Geopolymer has been studied extensively as an alternative construction material because it emits relatively lower CO₂ compared to ordinary Portland cement. Geopolymer is made of aluminosilicate and alkaline solution, and the Si/Al molar ratio affects its mechanical properties. Previous studies revealed that the Si/Al molar ratio of 1.8~2.0 results in the highest compressive strength, and the Si/Al molar ratio over 1.8 degrades the compressive strength of geopolymer severely; however the reason for the compressive strength degradation is still unclear. To understand the effect of the Si/Al molar ratio on the geopolymer structure, this study exploits the nanoindentation. The phase deconvolution of the indent modulus data is successful using the Gaussian mixture model, and it is observed that the Si/Al molar ratio alters the homogeneity of the geopolymer. Geopolymer becomes more homogeneous up to an Si/Al molar ratio of 1.8 at which geopolymer exhibits the highest compressive strength. The examination of this study is assumed to be adopted as evidence of strength degradation by the Si/Al ratio higher than the optimum value.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.2
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• pp.143-149
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• 2024

Segmentation of material phases through image analysis is essential for analyzing the microstructure of materials. Micro-CT images exhibit variations in grayscale values depending on the phases constituting the material. Phase segmentation is generally achieved by comparing the grayscale values in the images. In the case of waste concrete used as a recycled aggregate, it is challenging to distinguish between hydrated cement paste and natural aggregates, as these components exhibit similar grayscale values in micro-CT images. In this study, we propose a method for automatically separating the aggregates in concrete, in micro-CT images. Utilizing the Unet-VGG16 deep-learning network, we introduce a technique for segmenting the 2D aggregate images and stacking them to obtain 3D aggregate images. Image filtering is employed to separate aggregate particles from the selected 3D aggregate images. The performance of aggregate segmentation is validated through accuracy, precision, recall, and F1-score assessments.

• Journal of the Korean Geosynthetics Society
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• v.13 no.2
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• pp.21-29
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• 2014

The use of filling material based on cement paste is inefficient at field construction because it needs a lot of the charging mass. In addition, it has environmental problem according to the large amount of cement use because its strength is also larger than criterion. The excavated soil with stabilizer can be used as the filling materials when the bored pile is constructed. Therefore, this paper describes field application of solidified soil for economical efficiency and environment-friendly. The static axial load tests and the load-transfer measurements were performed to examine the axial resistant behavior of the piles. As results, the flowability, segregation and bleeding, and bond strength of filling materials was a good performance than that of the existing cement paste. But the skin friction of pile by PDA was slightly decreased than that of the existing cement paste. However, as pile filling materials, and in terms of economics and environment, the applicability of filling material is considered very effective.

• Journal of the Korean GEO-environmental Society
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• v.25 no.5
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• pp.21-27
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• 2024

Limestone-based cement has been well utilized as a construction material throughout the world, but as civil and architectural development accelerates, limestone will gradually be depleted. The use of cement, the main material for civil engineering and construction, is rapidly increasing in modern times, and the depletion of high-quality limestone resources will be greater than expected in the future. Therefore, if existing resources can be used as construction materials to replace cement based on accumulated technology, the depleting limestone resources can be utilized for a longer period of time. In order to determine whether Hwang-toh, which forms about 10% of the surface layer of Korea's terrain, can be partially utilized as a construction material, this study aims to develop a Hwang-toh accelerator agent and prove whether it can be applied to the field through indoor tests.

• Journal of the Korea Concrete Institute
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• v.19 no.6
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• pp.667-676
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• 2007

As the 21st century began, cement and concrete that are representatives of modem building materials became a major factor in global warming, air pollution and environmental pollution. Also, the problems that are generated while pursuing high performance and high strength became social issues. Therefore, it has become urgent to prepare counter plans. This study has aimed at the recycling of sewage sludge ash and developing it as a new concept in building material which serves the environmental considerations for long-lasting developmental purpose. Also, the study aimed to find a substitute for scarce natural resources and to secure high techniques for waste recycling. The purpose of this study was also to solve fundamentally secondary environmental pollution. The results revealed that the chemical components of sewage sludge ash are mainly $SiO_2\;and\;Al_2O_3$ which are similar to the components of pozzolan. Also, it was identified that sewage sludge ash can be utilized as a hardened specimen with an alkali activated pozzolan reaction. Considering the possibility of appropriate strength development and the advantage of drying shrinkage, compared with that of cement, it was believed that sewage sludge ash can demonstrate a function as a substitute for cement given.

• Journal of the Society of Disaster Information
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• v.11 no.3
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• pp.329-336
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• 2015

When diatomite powder was used as an admixture in mortar, its effects on the mortar strength was examined by experimental tests. For the tests, 4 kinds of commercially available diatomite powder were purchased ; one non-calcined product, one calcined product, and flux-calcined product two. The compressive and flexural strength of the mortar according to the increase of added amount of calcined diatomite powder increased at all test ages(7, 28, and 56 days). However, the use of non-calcined diatomite powder worsened the fluidity of mortar severely and that caused much more required water content. And flux-calcined product did not show useful effect on the mortar strength.