• Title/Summary/Keyword: Optimum Curing time

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Selection of the optimum mixture condition for stabilization of Songdo silty clay (송도 지역 해양성 점토 고화처리를 위한 최적배합 조건의 선정)

  • Kim, Jun-Young;Jang, Eui-Ryong;Chung, Choong-Ki;Lee, Yong-Jun;Jang, Soon-Ho;Choi, Jung-Yeul
    • Proceedings of the Korean Geotechical Society Conference
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    • 2009.09a
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    • pp.412-419
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    • 2009
  • Large quantity of extra soils discharged from excavation site in Songdo area can be treated by hardening agents and utilized in surface stabilized layer overlying thick reclaimed soft soil deposit. Though surface layer stabilization method using cement or lime for very soft soils has been studied in recent years, but studies on moderately soft clayey silt has not been tried. The purpose of this research is to investigate optimum mixing condition for stabilizing Songdo marine soil with low plasiticity. The optimum mixing conditions of hardening agents with Songdo soil such as kind of agents, mixing ratio, initial water content and curing time are investigated by uniaxial compression test and laboratory vane test. The results indicate that strength increases with high mixing ratio and long curing time, while decreases drastically under certain water content before mixing. Finally, optimum mixing condition considering economic efficiency and workability with test results was proposed.

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The Basic Study on the Spun Concrete Pipes using Blast-Furnace Slag Powder (고로슬래그 미분말을 사용한 콘크리트 흄관에 대한 기초적 연구)

  • 조영근;김승진;박유신;성기웅;손진군
    • Proceedings of the Korea Concrete Institute Conference
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    • 2000.10b
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    • pp.939-944
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    • 2000
  • This study examines both strength development and pore volume of high temperature curing mortar, using a blast-furnace slag powder (BFS). This study experiments with various pre-steaming period, differing curing temperature and the replacement of BFS. According to the results, the strength development of BFS mortar is stronger when higher curing temperature are used(as opposed to standard curing). Also, regardless of the curing method, pore volume decreases as the curing time increases. From these results we can identify the optimum conditions required pre-steaming period, differing curing temperature and the replacement to produce BFS mortar properties.

Optimization of Black Garlic Extract Curing Conditions for Mackerel Using Response Surface Methodology (반응표면분석을 이용한 고등어 절임용 흑마늘 추출액 절임조건의 최적화)

  • Shin, Jung-Hye;Kang, Min-Jung;Kim, Ra-Jeong;Yoon, Hwan-Sik;Sung, Nak-Ju
    • Korean journal of food and cookery science
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    • v.27 no.6
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    • pp.793-801
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    • 2011
  • We examined the quality characteristics of obtaining the optimal curing conditions for black garlic extract (BGE) added mackerel by using response surface methodology (RSM). The condition of RSM was included in 13 experimental points using two dependent variables: concentration of BGE (2.6~12.5 brix, X1) and curing time of BGE (17.58~102.42 min, X2). An assessment was conducted with four replicates on three independent variables: volatile basic amine (VBN, Y1), thiobarbituric acid (TBA, Y2), and shear force (Y3). The minimum content of VBN was 1.625 mg% at 3.17 brix, for 80.5 min. This was obtained when the BGE concentration was lower and the curing time was longer. The content of the TBA was 3.13~12.24 MA mg/kg at experiment range and the stationary point was at saddle point. Therefore, by using ridge analysis, the minimum point of TBA was 2.414 MA mg/kg at 3.5 brix for 84.4 min. The truth coefficient of the BGE concentration and curing time were 2.9 brix and 75.1 min, respectively, with a shear force ($120.764cm/kg^2$) shown at maximum point. The optimum Hunter color range was estimated from the lowest TBA value. The optimum range of the L color was 39.16~40.26, a and b color were 4.40~4.88 and 12.35~13.20, respectively.

The study on mechanical properties of PC panel with steam curing condition (증기양생 조건에 따른 터널 PC 패널의 물리적 특성에 관한 연구)

  • Ma, Sang-Joon;Jang, Pil-Sung;Shiin, Jin-Yong;Nam, Kwan-Woo
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.10 no.1
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    • pp.17-24
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    • 2008
  • Many problems exist in the current cast in place concrete lining used in domestic tunnel construction. Especially, the crack of tunnel lining brings about a social and economic problem. It has a lot of influence on stability of structure and the fine finish of lining. So enormous repair-work and reinforcement of tunnel lining could occur an running out of government's budget. In our country, there are domestic production enterprises which produce a special pre-cast concrete product, but the technical level of them is still far behind compared to developed countries. Also, optimum steam coring method is important for the production of high quality product. But there is no regulation of steam curing method in our country. This study is to investigate the properties of PC panel according to the variation of steam curing conditions such as presteaming time and rate of temperature rise. The result shows that the optimum presteaming time of steam curing method in PC panel is more than 1 hour and the desirable rate of temperature in curing chamber is about $20^{\circ}C/hr$.

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Mechanical behaviours of biopolymers reinforced natural soil

  • Zhanbo Cheng ;Xueyu Geng
    • Structural Engineering and Mechanics
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    • v.88 no.2
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    • pp.179-188
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    • 2023
  • The mechanical behaviours of biopolymer-treated soil depend on the formation of soil-biopolymer matrices. In this study, various biopolymers(e.g., xanthan gum (XG), locust bean gum (LBG), sodium alginate (SA), agar gum (AG), gellan gum (GE) and carrageenan kappa gum (KG) are selected to treat three types of natural soil at different concentrations (e.g., 1%, 2% and 3%) and curing time (e.g., 4-365 days), and reveal the reinforcement effect on natural soil by using unconfined compression tests. The results show that biopolymer-treated soil obtains the maximum unconfined compressive strength (UCS) at curing 14-28 days. Although the UCS of biopolymer-treated soil has a 20-30% reduction after curing 1-year compared to the maximum value, it is still significantly larger than untreated soil. In addition, the UCS increment ratio of biopolymer-treated soil decreases with the increase of biopolymer concentration, and there exists the optimum concentration of 1%, 2-3%, 2%, 1% and 2% for XG, SA, LBG, KG and AG, respectively. Meanwhile, the optimum initial moisture content can form uniformly biopolymer-soil matrices to obtain better reinforcement efficiency. Furthermore, the best performance in increasing soil strength is XG following SAand LBG, which are significantly better than AG, KG and GE.

A Study on the Effect of Curing Temperature on the Unconfined Compressive Strength of Soil Cement Mixtures. (양생온도가 Soil Cement의 압축강도에 미치는 영향에 관한 연구)

  • 김재영
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.17 no.4
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    • pp.3931-3942
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    • 1975
  • This study was conducted to investigate the strength of soil cement for varied curing temperatures (0,10,20,30,40,50,60$^{\circ}C$) and cement content (3,6,9,12%) in four cement-stabilized soils (KY: sand, MH: sand, SS: sandy loam, JJ:loam). The experimental results obtained from unconfined compressive strength tests were as follows: 1. According to increase of curing temperature as 30,40,50, and 60$^{\circ}C$, the unconfiened compressive strength of soil cement increased, the rate of increase in the early curing period was large, and around 120 hours was suifficient curing time to complete hardening. 2. The strength at 10$^{\circ}C$ decreased to the rate of 30 to 40 percent than that of 20$^{\circ}C$ while the strength at 0$^{\circ}C$ was very small, strength of soil cement increased in cold weather unless that the temperature was below 0$^{\circ}C$ 3. The average maximum temperature, about 30$^{\circ}C$ during July and August in Korea may be recommended for a optimum construction period to increase the strength of soil cement. 4. Accelerated curing time that strength was equivalent to 28-Day norma1 curing decreased in accordance with the increase of curing temperature, and also accelerated curing decreased the effect of cement content. Accelerated curing that strength was equivalent to 28-day normal curing for soil cement of cement content 9% and temperature 60$^{\circ}C$ was 45 hours; KY, 50 hours: MH, 40 hours; SS, 34 hours; JJ. 5. According to the increase of the percent passing of No. 200 sieve, accelerated curing times became shorter to become the required stength. 6. Relation between accelerated curing times and normal curing days was showeda linear of which slope decreased in accordance with the increase of curing temperature, it may be expressed as follows: (1). 30$^{\circ}C$ t=3.6d+6(r=0.97) (2). 40$^{\circ}C$ t=3.2d-5.1(r=0.95) (3). 50$^{\circ}C$ t=2.1d-4.0(r=0.93) (4). 60$^{\circ}C$ t=1.4d+4.0(r=0.90) in which t=accelerate curing time. d=normal curing day. 7. Accelerated curing time that the strength was equivalent to 35kg/$\textrm{cm}^2$ which was the strength of cement brick was 96 hours at temperature 30$^{\circ}C$ to SS 9%, and 120 hours at temperature 50$^{\circ}C$ to JJ 9%, Consequently, a economic soil cement brick may be made in future.

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A Study on the Strength Characteristics of Lime-Soil Mixtures. (석회혼합토의 강도특성에 관한 연구)

  • 조성정
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.22 no.3
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    • pp.46-59
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    • 1980
  • This study was conducted to obtain the most effective distribution of grain size and the optimum lime content for lime-soil stabilization. To achieve the aim, the change of consistency, the characteristics of compaction and unconfined compressive strength were tested by adding of 0, 4, 6, 8, 10 and 12 percent lime by weight for all soils adjusted by given ratios of sand to clay. The results obtained were as follows; 1. There was a tendency that the plasticity index of lime-soil mixture was decreased by increasing the amount of lime, whereas the liquid limit was varied irregularly and the plastic limit was increased. 2. With the addition of more lime, the optimum moisture content of lime-soil mixture was increased, and the maximum dry density was decreased. 3. The optimum lime content of lime-soil mixture was varied from soil to soil, and the less amount of small grain size, the less value of optimum lime content. 4. The optimum distribution of grain size for lime-soil mixture was in the soil, having the ratio of about 60 percent of cohesive clay and about 40 percent of sand by weight. 5. In the soil having fine grain size, the effect of curing appeared for long periods of time, whereas the increasing rate of unconfined compressive strength was great on the soil of coarse grain size in the earlier stage of curing period.

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Multi-response optimization of FA/GGBS-based geopolymer concrete containing waste rubber fiber using Taguchi-Grey Relational Analysis

  • Arif Yilmazoglu;Salih T. Yildirim;Muhammed Genc
    • Computers and Concrete
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    • v.34 no.2
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    • pp.213-230
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    • 2024
  • The use of waste tires and industrial wastes such as fly ash (FA) and ground granulated blast furnace slag (GGBS) in concrete is an important issue in terms of sustainability. In this study, the effect of parameters affecting the physical, mechanical and microstructural properties of FA/GGBS-based geopolymer concretes with waste rubber fiber was investigated. For this purpose, the effects of rubber fiber percentage (0.6%, 0.9%, 1.2%), binder (75FA25GGBS, 50FA50GGBS, 25FA75GGBS) and curing temperature (75 ℃, 90 ℃ and 105 ℃) were investigated. The Taguchi-Grey Relational Analysis (TGRA) method was used to obtain optimum parameter levels of rubber fiber geopolymer concrete (RFGC). The slump, fresh and hardened density, compressive strength, flexural strength, static and dynamic modulus of elasticity, ultrasonic pulse velocity (UPV) tests and scanning electron microscopy (SEM) analysis were performed on the produced concretes. The analysis of variance (ANOVA) method was used to statistically determine the effects of the parameters on the experimental results. A confirmation test was performed to test the accuracy of the optimum values found by the TGRA method. With the increase of GGBS percentage, the compressive strength of RFGC increased up to 196%. The increase in rubber fiber percentage and curing temperature adversely affected the mechanical properties of RFGC. As a result of TGRA, the optimum value was found to be A1B3C1. ANOVA results showed that the most effective parameter on the experimental results was the binder with 99% contribution percentage. It is understood from the SEM images that the optimum concrete had a denser microstructure and less capillary cracks and voids. For this study, the use of the TGRA method in multiple optimization has proven to provide very useful and reliable results. In cases where many factors are effective on its strength and durability, such as geopolymer concrete, using the TGRA method allows for finding the optimum value of the parameters by saving both time and cost.

A Study on the Strength Properties and the Temperature Hysteresis of Winter Concrete according to the difference of Curing Method in Mock-up Test (실물대시험에서의 양생방법 차이에 따른 한중콘크리트의 온도이력 및 강도특성에 관한 연구)

  • Won, Cheol;Han, Cheon-Goo
    • Journal of the Korea Institute of Building Construction
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    • v.3 no.4
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    • pp.87-94
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    • 2003
  • This study is to investigate the temperature hysteresis and development of compressive strength due to the curing conditions and to evaluate the optimum curing condition of test specimens showing the same development of strength to that of real structures in cold weather. The results of temperature curve with curing conditions in mock-up tests showed the trend of decrease plain concrete with insulation form, plain concrete with heating, concrete with accelerator for freeze protection, and control concrete in turn. The strength development of plain concrete of inside and outside of shelter showed the very slow strength gains due to early freezing, but that of concrete with accelerator for freeze protection showed the gradual increase of strength with time. From this, it is clear that accelerator for freeze protection has the effects of refusing the freezing temperature and accelerating the hardening under low temperature. Strength test results of small specimens embedded in members and located in insulation boxes at the site are similar to that of cores drilled from the members at the same ages, thus it is clear that these curing methods are effective for evaluating in-place concrete strength

AN EXPERIMENTAL STUDY ON THE PRODUCTION OF HIGH-STRENGTH CONCRETE PILE IN SITE (현장생산용 고강도 콘크리트 파일에 관한 실험적 연구)

  • 박칠림;권영호;백명종;이상수;정도순
    • Proceedings of the Korea Concrete Institute Conference
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    • 1995.04a
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    • pp.183-188
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    • 1995
  • Up to date, high-strength concrete pile which is producing in factory sells in the market. But according to the site and the construction conditions, the system to produce high-strength concrete pile directly in site is utilized in advanced country. Such the production system is the technique phenomenon very disirable in the side of quality control in site and the construction schedule, the time and the cost saving. This study is a fundamental experiment including concrete mixing design, non-autoclave curing method and the optimum condition to produce high-strengh concrete pile in site. As results of this study, High-strength concrete pile in site which target strength is 400kg/ $\textrm{cm}^2$ is able to produce it with optimum curing ciondition(75$^{\circ}C$, 9hr)and mixing design.

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