• Advances in concrete construction
• /
• 제2권4호
• /
• pp.301-308
• /
• 2014

The present research work is on the effect of sawdust ash (SDA) on the mechanical strengths of self compacting concrete (SCC) using naphthalene sulfonate (NS) as a plasticizer. Experiments on compressive, flexural and splitting tensile strengths are conducted and the data analyzed using the Minitab 15 software. The results showed that SDA can defer the reaction of cement hydration and prolong the setting times of cement paste. This was very much pronounced on the flexural and splitting tensile strengths at 90 days of curing which are 36 % and 33 % higher than the control strengths, respectively. The study has proposed strength relations of mortar compressive strength with the flexural and splitting tensile strengths and these are, 5 and 7 times respectively. The flexural strength is 1.5 times that of the splitting tensile. Finally, linear models were developed on these relationships.

• 터널과지하공간
• /
• 제7권3호
• /
• pp.221-229
• /
• 1997

Disc-type and ring-type specimens of four different materials were tested to investigate the tensile characteristics and their brief results are presented. Materials tested were marble, granite, cement mortar and plaster. Unizxial tensile strengths are compared with Brazilian and ring test strengths. It was found that Brazilian strengths were usually greater than uniaxial tensile strengths and affected by loading rates. In the ring tests, tensile strengths were generally found to be decreased as relative hole radius being increased. Ring test strengths, however, converged to some value in r$\geq$0.45 of marble, r$\geqq$0.29 of cement mortar and r$\leq$0.5 of plaster specimens. In such range of r, furthermore, transverse cracking of specimens were observed.

• Computers and Concrete
• /
• 제3권6호
• /
• pp.389-400
• /
• 2006

This paper presents the investigations towards developing a better understanding on the contribution of steel fibers on the tensile strength of high-performance fiber reinforced concrete (HPFRC). An extensive experimentation was carried out with w/cm ratios ranging from 0.25 to 0.40 and fiber content ranging from zero to 1.5 percent with an aspect ratio of 80. For 32 concrete mixes, flexural and splitting tensile strengths were determined at 28 days. The influence of fiber content in terms of fiber reinforcing index on the flexural and splitting tensile strengths of HPFRC is presented. Based on the test results, mathematical models were developed using statistical methods to predict 28-day flexural and splitting tensile strengths of HPFRC for a wide range of w/cm ratios. The expressions, being developed with strength ratios and not with absolute values of strengths and are applicable to wide range of w/cm ratio and different sizes/shapes of specimens. Relationship between flexural and splitting tensile strengths has been developed using regression analysis and absolute variation of strength values obtained was within 3.85 percent. To examine the validity of the proposed model, the experimental results of previous researchers were compared with the values predicted by the model.

• 한국의류학회지
• /
• 제42권2호
• /
• pp.224-236
• /
• 2018

This study analyzed differences between Jumchi-Hanji papers not dyed and dyed with persimmon juice (50% concentration) in five strength properties (tensile, wet tensile, tearing, bursting, and folding strengths). For the analysis, the undyed and the dyed Jumchi-Hanji papers were made by Jumchichigi during 40 minutes and made with the Dakji of different layer (a layer, two layers) and Choji method (Oebal-teugi, Ssangbal-teugi). Differences between Jumchi-Hanji papers dyed with the different concentration of persimmon juice (20% vs 70%) in the five strengths were also identified. For this examination, Jumchi-Hanji papers were made with two layer Dakji (Oebal-teugi Choji method) and by Jumchichigi during 60 minutes. Jumchi-Hanji papers made in this study were used as test samples. As a result, Jumchi-Hanji papers dyed with persimmon juice had higher tensile strength (CD), wet tensile strength (MD, CD), and bursting strength than those of undyed Jumchi-Hanji papers. However, tearing strengths (MD, CD) of dyed Jumchi-Hanji papers were lower than undyed Jumchi-Hanji papers. Folding strengths (CD) of dyed Jumchi-Hanji papers were low but the folding strengths (MD) of them were high compared to undyed Jumchi-Hanji papers. In addition, the concentration of persimmon juice influenced the five strength properties of Jumchi-Hanji. The tensile, wet tensile, and bursting strengths of Jumchi-Hanji papers dyed with a 70% concentration were higher than those one of Jumchi-Hanji papers dyed with a 30% concentration while the tearing and folding strengths of Jumchi-Hanji papers dyed with a 70% concentration were lower than Jumchi-Hanji papers dyed with a 30% concentration.

• 한국의류학회지
• /
• 제45권6호
• /
• pp.1035-1051
• /
• 2021

This study compares the strength properties of Jumchi-Hanjis dyed with 70% and 100% persimmon juice concentrations and undyed Jumchi-Hanjis. The Juumchi-Hanjis were made from Dakjis (mulberry papers), which were mixed with different ratios of fibers from paper mulberries originating in Korea and Thailand, including wood pulp from Canada. Research results showed that tensile, wet tensile, and bursting strengths of Jumchi-Hanjis dyed with 70% concentration were higher than those of undyed Jumchi-Hanjis. However, the tearing strengths of the dyed Jumchi-Hanjis were lower than those of undyed Jumchi-Hanjis. The wet tensile strengths of Jumchi-Hanjis dyed with 100% concentration were higher than those of dyed with 70% concentration. The increase and decrease of tensile, tearing, and bursting strengths depending on persimmon juice dyeing differed as per the mixing ratio of the raw materials of Jumchi-Hanjis. Dyeing with 100% persimmon juice concentration tends to be more useful than 70% to increase the tensile (MD) and wet tensile strengths of Jumchi-Hanjis containing only Korean mulberry fibers (90%) and wood pulp (10%) as raw materials. Dyeing with 100% concentration tends to be less useful than 70% to increase the tensile, tearing and bursting strengths of Jumchi-Hanjis with high proportions (90% or 60%) of mulberry fibers from Thailand.

• Steel and Composite Structures
• /
• 제21권6호
• /
• pp.1327-1345
• /
• 2016

$Al_2O_3$/SiC particulate reinforced (Metal Matrix Composites) MMCs which were produced by using stir casting process, bending strength and hardening behaviour were obtained using an analysis of variance (ANOVA) technique that uses full factorial design. Factor variables and their ranges were: particle size $2-60{\mu}m$; the stirring speed 450 rpm, 500 rpm and the stirring temperature $620^{\circ}C$, $650^{\circ}C$. An empirical equation was derived from test results to describe the relationship between the test parameters. This model for the tensile strength of the hybrid composite materials with $R^2$ adj = 80% for the bending strength $R^2$ adj = 89% were generated from the data. The regression coefficients of this model quantify the tensile strength and bending strengths of the effects of each of the factors. The interactions of all three factors do not present significant percentage contributions on the tensile strength and bending strengths of hybrid composite materials. Analysis of the residuals versus was predicted the tensile strength and bending strengths show a normalized distribution and thereby confirms the suitability of this model. Particle size was found to have the strongest influence on the tensile strength and bending strength.

• Structural Monitoring and Maintenance
• /
• 제11권2호
• /
• pp.71-86
• /
• 2024

In this study, to reduce the amount of cement consumed in the production of cementitious composites, the effects of partial replacement of cement weight with nano-silica, silica fume, and copper slag on the mechanical properties of polypropylene fiber-reinforced cementitious composites are investigated. For this purpose, the effect of replacing cement weight by each of the aforementioned materials individually and in combination is studied. A total of 34 mix designs were prepared, and their compressive, tensile, and flexural strengths were obtained for each mix. Among the mix designs with one cement replacement material, the highest strength is related to the sample containing 2.5% nano-silica. In this mix design, the compressive, tensile, and flexural strengths improve by about 33%, 13%, and 15%, respectively, compared to the control sample. In the ones with two cement replacement materials, the highest strengths are related to the mix made with 10% silica fume along with 2% nano-silica. In this mix design, compressive, tensile, and flexural strengths increase by about 42%, 18%, and 20% compared to the control sample, respectively. Furthermore, in the mixtures containing three cement substitutes, the final optimal mix design for all three strengths has 15% silica fume, 10% copper slag, and 2% nano-silica. This mix design improves the compressive, tensile, and flexural strengths by about 57%, 23%, and 26%, respectively, compared to the control sample. Finally, two relationships have been presented that can be used to predict the values of tensile and flexural strengths of cementitious composites with very good accuracy only by determining the compressive strength of the composites.

• Nuclear Engineering and Technology
• /
• 제53권3호
• /
• pp.911-919
• /
• 2021

In this paper, the design stress intensity values for the plate-type fuel assembly for research reactor are presented. Through a tensile test, the material properties of the cladding (aluminum alloy 6061) and structural material (aluminum alloy 6061-T6), in this case the yield and ultimate tensile strengths, Young's modulus and the elongation, are measured with the temperatures. The empirical equations of the material properties with respect to the temperature are presented. The cladding undergoes several heat treatments and hardening processes during the fabrication process. Cladding strengths are reduced compared to those of the raw material during annealing. Up to a temperature of 150 ℃, the strengths of the cladding do not significantly decrease due to the dislocations generated from the cold work. However, over 150 ℃, the mechanical strengths begin to decrease, mainly due to recrystallization, dislocation recovery and precipitate growth. Taking into account the uncertainty of the 95% probability and 95% confidence level, the design stress intensities of the cladding and structural materials are established. The presented design stress intensity values become the basis of the stress design criteria for a safety analysis of plate-type fuels.

• 한국방재학회 논문집
• /
• 제10권6호
• /
• pp.35-43
• /
• 2010

본 연구는 콘크리트 포장설계법에 사용되는 재료입력변수의 DB화를 염두에 두고 신뢰성 있는 콘크리트 물성 정량화 수립을 목적으로 수행되었다. 실험에 사용된 포장용 콘크리트는 화강암, 석회암, 사암의 조골재를 사용하였으며 화강암 배합의 경우 세 골재로서 자연사, 세척사, 부순모래 배합을 포함하였다. 먼저 콘크리트 강도시험을 통해 얻은 데이터를 이용하여 강도간의 상관관계 모델식을 정리하였다. 그리고 각 조골재별로 재령에 따른 압축강도, 휨강도, 쪼갬인장강도 및 탄성계수의 모델식을 제시하였다. 화강암 배합의 경우 세골재로서 사용된 자연사, 세척사, 부순모래 배합을 모두 포함한 산술평균을 적용하여 모델식을 제시하였다. 한편 쪼갬인장강도와 탄성계수는 실험방법 및 계측상 결과가 분산되는 경향이 있어서 상관관계식에서 예측된 값과 직접 구한 실험결과에 대해 산술평균을 적용후 보정하여 각 조골재별로 재령에 따른 탄성계수 및 쪼갬인장강도의 예측식을 제시하였다. 마지막으로 각 조골재 배합별 콘크리트의 포와송비 및 건조수축에 대한 기준 값을 제시하였다.

• 한국응용과학기술학회지
• /
• 제30권4호
• /
• pp.672-678
• /
• 2013

Although the basalt fiber has superior fire-resistance and chemical resistance, it has many disadvantages in its applications. Generally, the tensile and loop strengths of basalt fiber were decreased with generated frictional heat during industial appplications. To solve this problem, polytetrafluoroethylene (PTFE) coating system was introduced and a sutable coating condition was evaluated. The basalt fiber was pre-treated with triethoxytrifluoropropylsilane (TMTFPS) at various pHs and then coated with PTFE dispersions with penetrating agent sodium bis(2-ethylhexyl)sulfo succinate (DOS-Na) to increase the tensile and loop strengths as well as to reduce the fibril during working. A universial testing machine (Instron Model 3366) was used to measure tensile and loop strengths. When the PTFE dispersion with 0.25 wt% of DOS-Na was coated on the surface of basalt fiber after pre-treating with 5 wt% of PTFE, the highest tensile and loop strengths were reached to 3.5 gf/D and 2.4 gf/D, respectively.