• Title/Summary/Keyword: Aggregate temperature

Search Result 361, Processing Time 0.025 seconds

Numerical Study on Fire Performance of Hollowcore Slabs (할로우코어 슬래브의 내화성능에 대한 수치해석 연구)

  • Min, Jeong-Ki;Woo, Young-Je
    • Journal of Korean Association for Spatial Structures
    • /
    • v.15 no.3
    • /
    • pp.95-102
    • /
    • 2015
  • Numerical model on precast prestressed concrete (PC) hollowcore slabs using 11.3 mm diameter 7-wire stand was developed based on finite element analysis. In order to validate the modelling, previous experiment results with respect to prestressed solid concrete slabs were used and compared throughout the course of fire exposure. In addition to, the fire performance of hollowcore slabs with different aggregate types, moisture contents and compressive strength of concrete was investigated. As a result, it can be seen that the type of aggregates and moisture contents used in hollowcore slabs can affect the fire performance as well as temperature developments.

An Experimental study on Explosive spalling of Concrete According to Kinds of Fine Aggregate and Admixture (잔골재 및 혼화재 종류에 따른 콘크리트의 폭열 성상에 관한 실험적 연구)

  • 장재봉;김갑수;김재환;김용로;권영진;김무한
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • 2003.11a
    • /
    • pp.667-670
    • /
    • 2003
  • The purpose of this study is to present data for the reusing, reinforcement and estimation of safety of the RC structure damaged by fire, and for the prevention of explosive spalling by checking the character of explosive spalling according to kinds of fine aggregate, admixture and water-cement ratios. The materials used fine aggregates were sea sand, crushed sand and recycled sand, and the admixtures were fly ash and blast-furnace slag. Also the water-cement ratios was 55% and 30.5%. After those were heated respectively for 30 and 60 minutes in accordance with Standard Time-Temperature Curve. And then conditions of explosive spalling were divided into five grades, and characters of explosive spalling were investigated.

  • PDF

Properties of Mortar Using Steel Slag Fine Aggregate (제강슬래그 잔골재를 사용한 모르타르 특성)

  • 조성현;한기석;박성우;권기주;오상윤;김진만
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • 2003.05a
    • /
    • pp.217-222
    • /
    • 2003
  • The steel slag, a by-product which is produced during the manufacture of steel by refining pig iron, is mainly used as road materials after aging it. It is necessary to age steel slag for long time in air because the reaction with water and free-CaO in steel slag could make the expansion of volume. This problem prevents steel slag from being used as aggregate for concrete. But steel slag used in this study was controled by an air-jet method which rapidly cools substance melted at a high temperature. Rapid cooling prevents from generation of free-CaO in steel slag. In this study, properties of steel slag manufactured by air-jet method and mortar used it were investigated. As results of this study, free-CaO contents were controled under 1%. Mortar used this steel slag demanded to lower water contents, higher compressive strength and lower drying shrinkage than the basic mortar in the same condition.

  • PDF

Effects of Aggregate Mixing on the Strength Properties of Fire-Damaged Concrete (골재 혼입 유무가 고온수열 콘크리트의 강도 특성에 미치는 영향)

  • Kwon, Hyun-Woo;Kim, Young-Min;Heo, Young-Sun;Lee, Gun-Cheol
    • Proceedings of the Korean Institute of Building Construction Conference
    • /
    • 2021.05a
    • /
    • pp.133-134
    • /
    • 2021
  • In this study, the effects of aggregates on the properties of concrete as a study to determine the mechanical properties of high-temperature damaged concrete were examined. The samples to be reviewed are cement paste, mortar, and concrete, and the strength characteristics were reviewed after heating the compression strength and tensile strength properties. The increase in magnetic shrinkage at around 100℃ showed a significant drop in strength in mortar, which does not contain aggregates or has a small diameter, and after 300℃, concrete showed a sharp drop in strength due to the hydration and aggregation of cement.

  • PDF

An Experimental Study of Silica Particle Growth in a Coflow Diffusion Flame Utilizing Light Scattering and Local Sampling Technique (II) - Effects of Diffusion - (광산란과 입자포집을 이용한 동축류 확산화염 내의 실리카 입자의 성장 측정(II) - 확산의 영향 -)

  • Cho, Jaegeol;Lee, Jeonghoon;Kim, Hyun Woo;Choi, Mansoo
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.23 no.9
    • /
    • pp.1151-1162
    • /
    • 1999
  • The effects of radial heat and $H_2O$ diffusion on the evolution of silica particles in coflow diffusion flames have been studied experimentally. The evolution of silica aggregate particles in coflow diffusion flames has been measured experimentally using light scattering and thermophoretic sampling techniques. The measurements of scattering cross section from $90^{\circ}$ light scattering have been utilized to calculate the aggregate number density and volume fraction using with combination of measuring the particle size and morphology through the localized sampling and a TEM image analysis. Aggregate or particle number densities and volume fractions were calculated using Rayleigh-Debye-Gans and Mie theory for fractal aggregates and spherical particles, respectively. Flame temperatures and volumetric differential scattering cross sections have been measured for different flame conditions such as inert gas species, $H_2$ flow rates, and burner injection configurations to examine the relation between the formation of particles and radial $H_2O$ diffusion. The comparisons of oxidation and flame hydrolysis have also been made for various $H_2$ flow rates using $N_2$ or $O_2$ as a carrier gas. Results indicate that the role of oxidation becomes dominant as both carrier gas($O_2$) and $H_2$ flow rates increases since the radial heat diffusion precedes $H_2O$ diffusion in coflow flames used in this study. The effect of carrier gas flow rates on the evolution of silica particles have also been studied. When using $N_2$ as a carrier gas, the particle volume fraction has a maximum at a certain carrier gas flow rate and as the flow rate is further increased, the hydrolysis reaction Is delayed and the spherical particles finally evolves into fractal aggregates due to decreased flame temperature and residence time.

Manufacturing of artificial lightweight aggregate from water treatment sludge and application to Non-point treatment filteration (정수슬러지를 재활용한 인공경량골재의 제조 및 비점오염원 여재의 적용)

  • Jung, Sung-Un;Lee, Seoung-Ho;Namgung, Hyun-Min
    • Industry Promotion Research
    • /
    • v.6 no.4
    • /
    • pp.1-9
    • /
    • 2021
  • The purpose of this study is to manufacture lightweight aggregates for recycling water treatment sludge, to identify the physical properties of the aggregates, and present a method of utilizing the manufactured lightweight aggregates. The chemical composition and thermal properties were examined via a raw materials analysis. The aggregate examined here was fired by the rapid sintering method and the single-particle density and water absorption rate were measured. Water treatment sludge has high ignition loss and high fire resistance. When 30wt% of purified sludge was added, the single-particle density of the aggregates was in the range of 0.8~1.2g/cm3 at a temperature of 1,150~1,200℃. At temperatures of 1200℃ or higher, ultra-light aggregates having a single-particle density of 0.8 or less could be produced. When applied to concrete by replacing the general aggregate in the concrete, a specimen having strength values of 200 to 450 kgf/cm2 on 28 days was obtained, and when applied as a filter material, the performance was equal to or higher than that of ordinary sand.

A novel prediction model for post-fire elastic modulus of circular recycled aggregate concrete-filled steel tubular stub columns

  • Memarzadeh, Armin;Shahmansouri, Amir Ali;Poologanathan, Keerthan
    • Steel and Composite Structures
    • /
    • v.44 no.3
    • /
    • pp.309-324
    • /
    • 2022
  • The post-fire elastic stiffness and performance of concrete-filled steel tube (CFST) columns containing recycled aggregate concrete (RAC) has rarely been addressed, particularly in terms of material properties. This study was conducted with the aim of assessing the modulus of elasticity of recycled aggregate concrete-filled steel tube (RACFST) stub columns following thermal loading. The test data were employed to model and assess the elastic modulus of circular RACFST stub columns subjected to axial loading after exposure to elevated temperatures. The length/diameter ratio of the specimens was less than three to prevent the sensitivity of overall buckling for the stub columns. The gene expression programming (GEP) method was employed for the model development. The GEP model was derived based on a comprehensive experimental database of heated and non-heated RACFST stub columns that have been properly gathered from the open literature. In this study, by using specifications of 149 specimens, the variables were the steel section ratio, applied temperature, yielding strength of steel, compressive strength of plain concrete, and elastic modulus of steel tube and concrete core (RAC). Moreover, parametric and sensitivity analyses were also performed to determine the contribution of different effective parameters to the post-fire elastic modulus. Additionally, comparisons and verification of the effectiveness of the proposed model were made between the values obtained from the GEP model and the formulas proposed by different researchers. Through the analyses and comparisons of the developed model against formulas available in the literature, the acceptable accuracy of the model for predicting the post-fire modulus of elasticity of circular RACFST stub columns was seen.

A Study on the Performance Evaluation Method of Warm-mix Asphalt Mixture by the Analysis of Bonding Properties between Asphalt Binder and Aggregate (중온 아스팔트 혼합물의 성능 평가를 위한 아스팔트 바인더와 골재 사이의 접착물성분석 방법에 관한 연구)

  • Yoo, In Sang;Cho, Dong-Woo;Hwang, Sung Do;Rhee, Suk Keun
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.31 no.6D
    • /
    • pp.803-810
    • /
    • 2011
  • The public interest of global warming and energy shortage is gradually increased, and the related industries also have become interested in developing eco-friendly material and technology. Warm-mix asphalt (WMA) is a result of the developments to alleviate global warming and energy problems. This WMA is produced at lower temperatures than the temperature at which hot mix asphalt (HMA) is produced. Because most tests in Superpave are developed only for the performance and maintenance of HMA produced by hot temperatures, it is difficult for the tests to identify properly the material properties and then evaluate the performances between HMA and WMA. This study deals with the development of a new protocol to differentiate HMA and WMA performance, and especially the interfacial properties between asphalt and aggregate are targeted as the performance indicator; thus, an evaluation method and guideline are suggested. The concept and idea of the test method applied in this study were modified from the DSR moisture damage test protocol. In addition, TSR test was performed to affirm the relation between the asphalt-aggregate interface and the asphalt-aggregate mixture performances. The followings are the results of this study. Shear stress at 85% linear visco-elastic complex modulus (LVE $G^*$) can be a better parameter than LVE $G^*$, which can assess the interfacial or bonding performance between asphalt and aggregate. Moreover, measuring the bonding performance in thinner film thicknesses will be a better way to evaluate the real and field situation between asphalt and aggregate. The interfacial properties' criteria to apply the newly developed test and parameter should be developed, after the asphalt mixture criteria relating to the interfacial properties are completed.

Density and Water Absorption Characteristics of Artificial Lightweight Aggregates containing Stone-Dust and Bottom Ash Using Different Flux (폐석분 및 바텀애시를 사용한 인공경량골재의 융제(Flux) 종류에 따른 밀도 및 흡수율 특성)

  • Han, Min-Cheol;Shin, Jae-Kyung
    • Journal of the Korean Recycled Construction Resources Institute
    • /
    • v.7 no.3
    • /
    • pp.49-55
    • /
    • 2012
  • In this paper, the physical properties of lightweight aggregate such as density and water absorption according to addition ratio and type of flux were investigated. When using $Na_2CO_3$ as flux of lightweight aggregate, burnability was available at low burning temperature and water absorption increased. And as increasing addition ratio of $CaCO_3$, NaOH, $Fe_2O_3$, absorption decreased and $CaCO_3$, NaOH, $Fe_2O_3$ were considered improper to use flux of lightweight aggregate because of high dried density. $Na_2SO_4$ was proper to use flux of lightweight aggregate due to dried density $1.35{\sim}1.50g/cm^3$ and lower absorption. When using glass abrasive sludge as flux of lightweight aggregate, dried density and water absorption were in the range of $1.45{\sim}1.55g/cm^3$ and 9~12% respectively. It was indicated that as increasing addition ratio of blast furnace slag powder, density increased whereas absorption decreased. In use of oxidizing slag as flux, artificial lightweight aggregate which have dried density $1.46g/cm^3$, water absorption 8,5 % can be manufactured at 10 % of addition ratio.

  • PDF

Growth of Grass and Control of temperature of Planting Concrete for Roof Using Recycled Aggregate (재생골재를 이용한 옥상식재용 콘크리트의 잔디생육과 열환경조정효과)

  • 이상태;김정진;황정하;김진선;오선교;한천구
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • 2001.05a
    • /
    • pp.237-242
    • /
    • 2001
  • The objective of this study is to investigate growth of grass planted with planting concrete using recycled aggregste. Planting concrete blocks are constructed on the roof of existing building. Temperature variation according to planting concrete method are also investigate. According to test results, it shows that grass grows very well under planting concrete method. When planting concrete method is applied, it brings about temperature reducing effects about 1~$2^{\circ}C$ at inner part of the buildings at cooling required period compared to that with existing roof, and at heating required period temperature insulating effects about 2~$4^{\circ}C$.

  • PDF