• Title/Summary/Keyword: Engineering Properties of concrete

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Fundamental Properties of Mortar with Magnet-Separated Converter-Slag Powder as SCM (자력 선별 전로슬래그 미분말을 결합재로 활용한 모르타르의 기초특성)

  • Beom-Soo Kim;Sun-Mi Choi;Jin-Man Kim
    • 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.

Static and Dynamic Analysis for Railway Tunnel according to Filling Materials for overbroken tunnel bottom (철도터널 하부 여굴처리 방법에 대한 정적 및 동적 안정성 검토)

  • Seo, Jae-Won;Cho, Kook-Hwan
    • Journal of the Korean Society for Railway
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    • v.20 no.5
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    • pp.668-682
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    • 2017
  • Alignments of railways recently constructed in Korea have been straightened due to the advent of high-speed rail, which means increasing the numbers of tunnels and bridges. Overbreak during tunnel construction may be unavoidable, and is very influential on overall stability. Over-excavation in tunneling is also one of the most important factors in construction costs. Overbreak problems around crown areas have decreased with improvements of excavation methods, but overbreak problems around bottom areas have not decreased because those areas are not very influential on tunnel stability compared with crown areas. The filling costs of 10 cm thickness of overbreak at the bottom of a tunnel are covered under construction costs by Korea Railway Authority regulations, but filling costs for more than the covered thickness are considered losses of construction cost. The filling material for overbreak bottoms of tunnels should be concrete, but concrete and mixed granular materials with fractured rock are also used for some sites. Tunnels in which granular materials with fractured rock are used may have a discontinuous section under the concrete slab track. The discontinuous section influences the propagation of waves generated from train operation. When the bottom of a tunnel is filled with only concrete material, the bottom of the tunnel can be considered as a continuous section, in which the waves generated from a train may propagate without reflection waves. However, a discontinuous section filled with mixed granular materials may reflect waves, which can cause resonance of vibration. The filled materials and vibration propagation characteristics are studied in this research. Tunnel bottom filling materials that have ratios of granular material to concrete of 5.0 %, 11.5 %, and 18.0 % are investigated. Samples were made and tested to determine their material properties. Static numerical analyses were performed using the FEM program under train operation load; test results were found to satisfy the stability requirements. However, dynamic analysis results show that some mixed ratios may generate resonance vibration from train operation at certain speeds.

The Solidification Characteristics of Recycled Aggregate Mixed with Incineration Ash and Waste Concrete (소각재와 폐콘크리트를 이용한 재생골재의 고형화 특성)

  • Yeon, Ikjun;Ju, Soyoung;Lee, Sangwoo;Shin, Taeksoo;Kim, Kwangyul
    • Journal of the Korean GEO-environmental Society
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    • v.9 no.5
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    • pp.5-13
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    • 2008
  • In this study, It was carried out to evaluate the feasibility of recycled crushed concrete as aggregate used cement mortar replace sand and to investigate engineering properties of recycled aggregate for hazardous waste solidification. The compressive strength of cement mortar replaced 5-15% (wt.) recycled aggregate was over 163kgf/cm2 which is the standard of first grade concrete block class C. And cement mortar was examined to evaluate the stability by leaching test. Cu, Cd, Pb, Cr, and As as the heavy metals were proved very stable but mercury (Hg) was leached high concentration because it was simply tied to the cement surface. We investigated the crystal structures of cement mortar and they had shown the peaks of Ca(OH)2, ettringite, and CSH (calcium silicate hydrate). As the result, the longer curing time, the higher CSH peak that means to increase compressive strength and the cement mortar was more stable. Therefore it was shown that it may be possible to apply hazardous waste solidification using recycled aggregate, fly ash and sewage sludge ash.

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An Experimental Study on Water-Purification Properties in Cement Bricks Using Effective Micro-Organisms and Zeolite (유용 미생물과 제올라이트를 이용한 시멘트 벽돌의 수질 정화 특성에 관한 실험적 연구)

  • Kim, Wha-Jung;Choi, Kil-Jun;Park, Jun-Seok
    • Journal of the Korea Concrete Institute
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    • v.23 no.3
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    • pp.331-338
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    • 2011
  • The purpose of this study is to use organisms or micro-organism functions for eco-friendly water-purification of cement bricks, utilizing bioremediation. Many researches have been performed in the past to improve water quality by using effective micro-organisms in construction materials. In order to purify water using micro-organisms, this research used soybean paste bacteria, an effective micro-organism that was identified through 16S rDNA sequence analysis performed in Daegu S. Environment Protection Institute in addition to Natto bacteria that was studied in the previous research. With these effective micro-organisms with water-purification ability, this study examined their water-purification possibility on cement bricks. This study used Zeolite to immobilize micro-organisms to bricks, and confirmed that the micro-organisms were attached on Zeolite from SEM analysis. The experimental results showed that specific micro-organisms can be used to effectively remove contamination an used to develop eco-friendly construction materials. The study on micro-organisms for material purification shows great promises as a future research topic.

The Effect of DMPA Contents on the Water Dispersability and Mechanical Properties of Urea Resin (DMPA의 함량이 우레아 수지의 수분산 안정성과 기계적 성질에 미치는 영향)

  • Park, Jae Cheol;Kim, Dong Soo;Lee, Soo
    • Journal of the Korean Applied Science and Technology
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    • v.36 no.4
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    • pp.1128-1135
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    • 2019
  • In this study, different types of polyether amines and H12MDI were used to synthesize water dispersed urea resins, which can be applied to coating material on the concrete slabs for bicycle road using the ordinary application equipments. The concentrations of several polyether amines with different molecular weights and the number of amine functionality were varied to set up the optimal condition for water dispersed urea resin preparation with both an excellent tensile strength and an elongation. In addition, the effect of DMPA[2,2-Bis(hydroxymethyl)propanoic acid] concentration on the storage stability of the water dispersed urea resin was also investigated. The formation of urea bonds from isocyanate and polyether amines was confirmed through FT-IR ATR spectroscopy. From the mechanical properties of urea resins, PU-4 and PU-6, which were prepared with both diamines and triamine of different molecular weights and number of functionality, showed the tensile strength of 10.5 N/㎟ and 12.7 N/㎟, respectively and the elongation of 1165 % and 969%, respectively. Among the water dispersed urea resin synthesized with different contents of DMPA, PU-6 showed the highest mechanical properties, a tensile strength of 14.2 N/㎟ and an elongation of 993%. In addition, the water dispersion state of this PU-6 was the most stable even after 8 weeks.

Rapid Evaluation Method for OPC Fineness by Hydrometer and Influence of OPC Fineness on Properties of Mortar (액체밀도계법에 의한 OPC 분말도의 신속추정 및 OPC 분말도가 모르타르의 특성에 미치는 영향)

  • Han, Cheon-Goo;Kim, Young-Tae
    • Journal of the Korea Institute of Building Construction
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    • v.18 no.5
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    • pp.429-437
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    • 2018
  • The aim of the research is to analyze a feasibility of rapid evaluation method for cement fineness by the relation analysis between density measurement using hydrometer and fineness of ordinary Portland cement. Additionally, based on the commercially available cement product, relation between a series of fundamental properties of cement mortar and fineness of cement powder was analyzed. As an experimental result, the actually measured fineness value of cement powder showed a good correlation with the fineness value obtained by hydrometer while there was poor correlation with the fineness value on specification. Especially, the density measurement in three minutes showed the closest relation with cement powder fineness, thus rapid quality evaluation of cement powder can be possible by using the regression equation obtained from the three minutes density measurement. Additionally, there was a high relation between cement powder fineness with a fundamental properties of the cement mortar such as fluidity, air content, setting time, and strength development.

Effects of subsequent curing on chloride resistance and microstructure of steam-cured mortar

  • Hu, Yuquan;Hu, Shaowei;Yang, Bokai;Wang, Siyao
    • Advances in concrete construction
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    • v.9 no.5
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    • pp.449-457
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    • 2020
  • The influence of subsequent curing on the performance of fly ash contained mortar under steam curing was studied. Mortar samples incorporated with different content (0%, 20%, 50% and 70%) of Class F fly ash under five typical subsequent curing conditions, including standard curing (ZS), water curing(ZW) under 25℃, oven-dry curing (ZD) under 60℃, frozen curing (ZF) under -10℃, and nature curing (ZN) exposed to outdoor environment were implemented. The unsteady chloride diffusion coefficient was measured by rapid chloride migration test (RCM) to analyze the influence of subsequent curing condition on the resistance to chloride penetration of fly ash contained mortar under steam curing. The compressive strength was measured to analyze the mechanical properties. Furthermore, the open porosity, mercury intrusion porosimetry (MIP), x-ray diffraction (XRD) and thermogravimetric analysis (TGA) were examined to investigate the pore characteristics and phase composition of mortar. The results indicate that the resistance to chloride ingress and compressive strength of steam-cured mortar decline with the increase of fly ash incorporated, regardless of the subsequent curing condition. Compared to ZS, ZD and ZF lead to poor resistance to chloride penetration, while ZW and ZN show better performance. Interestingly, under different fly ash contents, the declining order of compressive strength remains ZS>ZW>ZN>ZD>ZF. When the fly ash content is blow 50%, the open porosity grows with increase of fly ash, regardless of the curing conditions are diverse. However, if the replacement amount of fly ash exceeds a certain high proportion (70%), the value of open porosity tends to decrease. Moreover, the main phase composition of the mortar hydration products is similar under different curing conditions, but the declining order of the C-S-H gels and ettringite content is ZS>ZD>ZF. The addition of fly ash could increase the amount of harmless pores at early age.

Performance-based and damage assessment of SFRP retrofitted multi-storey timber buildings

  • Vahedian, Abbas;Mahini, Seyed Saeed;Glencross-Grant, Rex
    • Structural Monitoring and Maintenance
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    • v.2 no.3
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    • pp.269-282
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    • 2015
  • Civil structures should be designed with the lowest cost and longest lifetime possible and without service failure. The efficient and sustainable use of materials in building design and construction has always been at the forefront for civil engineers and environmentalists. Timber is one of the best contenders for these purposes particularly in terms of aesthetics; fire protection; strength-to-weight ratio; acoustic properties and seismic resistance. In recent years, timber has been used in commercial and taller buildings due to these significant advantages. It should be noted that, since the launch of the modern building standards and codes, a number of different structural systems have been developed to stabilise steel or concrete multistorey buildings, however, structural analysis of high-rise and multi-storey timber frame buildings subjected to lateral loads has not yet been fully understood. Additionally, timber degradation can occur as a result of biological decay of the elements and overloading that can result in structural damage. In such structures, the deficient members and joints require strengthening in order to satisfy new code requirements; determine acceptable level of safety; and avoid brittle failure following earthquake actions. This paper investigates performance assessment and damage assessment of older multi-storey timber buildings. One approach is to retrofit the beams in order to increase the ductility of the frame. Experimental studies indicate that Sprayed Fibre Reinforced Polymer (SFRP) repairing/retrofitting not only updates the integrity of the joint, but also increases its strength; stiffness; and ductility in such a way that the joint remains elastic. Non-linear finite element analysis ('pushover') is carried out to study the behaviour of the structure subjected to simulated gravity and lateral loads. A new global index is re-assessed for damage assessment of the plain and SFRP-retrofitted frames using capacity curves obtained from pushover analysis. This study shows that the proposed method is suitable for structural damage assessment of aged timber buildings. Also SFRP retrofitting can potentially improve the performance and load carrying capacity of the structure.

Properties of Lean Mixed Mortar with Various Replacement Ratio of Coal Gasification Slag (석탄가스화발전 용융슬래그의 치환율 변화에 따른 빈배합 모르타르의 특성 분석)

  • Park, Kyung-Taek;Han, Min-Cheol;Hyun, Seung-Yong
    • Journal of the Korea Institute of Building Construction
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    • v.19 no.5
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    • pp.391-399
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    • 2019
  • This study reviewed the possibility of recycling into exhausted aggregate resources in Korea as a means of utilizing coal gasification slag(CGS) from integrated gasification combined cycle(IGCC) while being commissioned in order to introduce the new system to Korea. In other words, in order to solve the problem of insufficient aggregate resources, CGS generated by IGCC as a residual aggregate for concrete secondary products, which is an empty mortar, was considered to replace CGS in the range of 0 to 100 % for mixed residual aggregate mixed with crushed sand A(CSa) of good quality and sea sand(SS) of deep particles, which are the most commonly used in the domestic construction industry. According to the study, replacing CGS with CSa or crushed sand B(CSb)+SS by 25 % to 50 % resulted in good results in the aspect of the granularity of the aggregate and the workability and compressive strength of cement mortar, which were found to be usable.

Properties of High Volume Blast Furnace Slag Concrete using Recycled Aggregate with Incineration Waste Ash (소각장애시의 치환에 따른 고로슬래그 미분말 다량치환 순환골재 콘크리트의 특성)

  • Han, Cheon-Goo;Lee, Hyang-Jae;Kim, Jun-Ho
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.1 no.2
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    • pp.107-113
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    • 2013
  • This study is the study desiring to solve the problem by utilizing the kinds of recycled resources considered to be troubled complementarily. Namely the reaction of potential hydraulicity of Blast Furnace Slag Powder (BS) shall be reacted with the alkali of Recycled Fine Aggregates Coarse Aggregate, it has been experimented to obtain the optimum value with the replacement ratio of incineration plant ash (WA) treated with the slaked lime as the experiment variable by solving the alkali of shortage with the Ordinary Portland Cement (OPC). As a result, the liquidity and the air volume are declined slightly as the replacement ratio of incineration plant ash WA increases, the mixture of incineration plant ash WA 1% has been analyzed to be the most suitable considering the viewpoint of effective handling of waste as the compression and the tensile strength showed the maximum value before and after 1% even though it was disadvantageous with the increase of chloride content.