• Advances in concrete construction
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• 제11권3호
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• pp.219-229
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• 2021

In recent years, geopolymer cements, have gained significant attention as an environmental-friendly type of cement. In this experimental research, effects of different alkaline activator solutions and variations of associated parameters, including time of addition, concentration, and weight ratio, on the mechanical strengths of Granulated Ground Blast Furnace Slag (GGBFS)-based Geopolymer Concrete (GPC) were investigated. Investigation of the effects of simultaneous usage of KOH and NaOH solutions on the tensile and flexural strengths of GGBFS-based GPC, and the influence of NaOH solution addition time delay on the mechanical strengths is among the novel aspects investigated in this research. four series of mix designs and corresponding specimen testing is conducted to study different parameters of the active alkali solutions on GPC mechanical strengths. The results showed that addition of NaOH to the mix after 3 min of mixing KOH and Na2SiO3 with dry components (1/3 of the total mixing duration) resulted in the highest compressive, tensile and flexural strengths amongst other cases. Moreover, increasing the KOH concentration up to 12 M resulted in the highest compressive strength, while weight ratio of 1.5 for Na2SiO3/KOH was the optimum value to achieve highest compressive strengths.

• 한국농공학회논문집
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• 제60권1호
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• pp.101-110
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• 2018

This study experimentally investigated the compressive and flexyral strength development characteristics of polymer concrete using four different type polymeric resins such as unsaturated polyester, vinyl ester, epoxy, and PMMA (polymethyl methacrylate) as binders. The test results show that the average compressive strength of those four different polymer concretes was 88.70 MPa, the average flexural strength was 20.30 MPa. Those test results show that compressive and flexural strengths of polymer concrete were much stronger than compressive and flexural strengths of ordinary Portland cement concrete. In addition, the relative gains of the compressive strength development at the age of 24 hrs compared to the age of 168 hrs were 68.6~88.3 %. Also, the relative gains of the flexural strength development at the age of 24 hrs compared to the age of 168 hrs were 73.8~93.4 %. These test results show that compressive and flexural strengths of each polymer concrete tested in this study were developed at the early age. Moreover, the prediction equations of compressive and flexural strength developments regarding the age were determined. The determined prediction equations could be applied to forecast the compressive and flexural strength developments of polymer concrete investigated in this study because those prediction equations have the high coefficients of correlation. Last, the relations between the compressive strength and the flexural strength of polymer concrete were determined and the flexural/compressive strength ratios were from 1/4 to 1/5. These results show that polymer concretes investigated in this study were appropriate as a flexural member of a concrete structure because the flexural/compressive strength ratios of polymer concrete were much higher than the flexural/compressive strength ratios of Portland cement concrete.

• Computers and Concrete
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• 제16권2호
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• pp.209-222
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• 2015

This paper presents results of biaxial compressive tests and strength criterion on two replacement percentages of recycled coarse aggregate (RPRCA) by mass for plain structural recycled aggregate concrete (RAC) at all kinds of stress ratios. The failure mode characteristic of specimens and the direction of the cracks were observed and described. The two principally static strengths in the corresponding stress state were measured. The influence of the stress ratios on the biaxial strengths of RAC was also analyzed. The experimental results showed that the ratios of the biaxial compressive strength ${\sigma}_{3f}$ to the corresponding uniaxial compressive strength $f_c$ for the two RAC are higher than that of the conventional concrete (CC), and dependent on the replacement percentages of recycled coarse aggregate, stress states and stress ratios; however, the differences of tensile-compressive ratios for the two RAC and CC are smaller. On this basis, a new failure criterion with the stress ratios is proposed for plain RAC under biaxial compressive stress states. It provides the experimental and theoretical foundations for strength analysis of RAC structures subject to complex loads.

• 한국구조물진단유지관리공학회 논문집
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• 제7권2호
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• pp.201-208
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• 2003

In domestic, bearing wall apartment building have not rectangular walls but irregular walls which are designed at walls of various cross-sectional shapes such as H-shaped, T-shaped, Box-shaped and L-shaped. In these irregular walls connected with rigid joint each other, one side walls of irregular walls is expected to show effective behavior for rigid-jointed the other side walls. Moreover, previous studies have focused on simplifying irregular walls into rectangular walls because of the complication in structural design and analysis. So studies for variables affecting behaviors of irregular walls, such as aspect ratios and compressive strength of concrete, are insufficient. The objective of this study is to evaluate the behaviors of T-shaped structural walls with different concrete compressive strengths and aspect ratios by experimental works. Results of this experimental study show that flange wall is contributed to increase the flexural strengths by the variation of concrete strengths and aspect ratios, and that it is needed to evaluate the effect width of flange wall for rational wall design.

• 대한조선학회논문집
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• 제47권5호
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• pp.709-718
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• 2010

This paper deals with two contents: first, distributions of plate slenderness ratios, stiffened plate slenderness ratios, and stiffener slenderness ratios, which include dimensions and material variables of stiffened plates, of stiffened plates of large-sized in-service vessels, and, second, comparison of compressive strengths. The investigated vessels consist of 59 tankers, 49 bulkers, 28 product carriers, 15 container carriers, and 12 multi-purpose vessels. The tankers are ranged from handymax class to VLCC and larger than Suezmax class. The sizes of the bulkers are 20K to 200K deadweight. The maximum size of containers is less than 5000TEU class. Two parameters for normal distributions of the slenderness ratios (mean and standard deviation) are suggested and probable ranges of the slenderness ratios are also graphically presented. The ultimate strengths of the stiffened plates are presented using the various simplified formulas and nonlinear FEAs. As well, average compressive strength curves, which are necessary for the estimation of the hull girder moment capacities, are proposed. It is proved that formulas for stiffened plates in CSR overestimate slightly in overall average strain range. Mode5 formula (plate buckling mode) in CSR show unreasonably conservative results with respect to the ultimate strengths rather than post-ultimate average compressive strengths.

• Journal of Biosystems Engineering
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• 제29권1호
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• pp.29-36
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• 2004

The geometric characteristics of the Altari radish were measured for the purpose of mechanization of the kimchi processing. In this study, geometric characteristics such as the sectional area and volume of the radishes(pyeong-gang and sa-chul) were calculated using the image processing method, and physical properties such as the compressive strength, the cutting force of the radish and the torsional moment of the radish leaf-stems were measured by using a universal testing machine. In case of the radish(pyeong-gang), the weight was ranged 215.0∼465.0 g, the length of the radishes(body) was 86.3∼129.2 mm, the diameters were 43.3∼58.1 mm, and the length of the leaves was 261.3-368.2 mm. And the vertical compressive strengths were ranged 83.8∼171.7 N/$\textrm{cm}^2$, the horizontal compressive strengths were 113.0∼176.3 N/$\textrm{cm}^2$, the shearing forces were 86.0∼114.6 N, and the surface hardness was ranged 51.1∼52.1 N/$\textrm{cm}^2$. In case of the radish(sa-chul), the weight was ranged 203.5∼412.2 g, the length of the bodies was 67.5∼127.0 mm, the diameters were 22.3∼59.8 mm and the length of the leaves was 245.6∼312.6 mm respectively. And the vertical compressive strengths were ranged 91.3∼168.3 N/mm, the horizontal compressive strengths were 132.6∼186.9 N/$\textrm{cm}^2$, the shearing forces were 89.4∼116.5 N, and the surface hardness was ranged 52.4∼67.8 N/$\textrm{cm}^2$, respectively.

• 산업기술연구
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• 제10권
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• pp.57-67
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• 1990

Uniaxial compression tests are performed under various loading rates to study the influence of loading rate on the compressive strengths and deformation behaviours. The rock samples adopted in this experiments are Onyang granite, Hambaek sandstone, Hambaek shale and Donghae limestone. Total 120 specimens are prepared for this study. As the loading rate increases from static to dynamic state which is about the level of $800{\sim}1,400kgf/cm^2/sec$, the uniaxial compressive strengths are also increased within the range of 40%. And Young's modulus and Poisson's ratio show similar trends but have a little lower rates of increase when compared with that of uniaxial compressive strength.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.83-88
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• 2001

In this study, the tensile and compressive tests of glass fiber epoxy composites were performed to measure the strength variation with respect to strain rates of 1-200 $\textrm{sec}^{-1}$. In addition, tensile and compressive tests of 50-200 $\textrm{sec}^{-1}$ strain rates were conducted at a low temperature ($-60^{\circ}C$) to investigate the effects of temperature on the strength variation. From the test results, it was found that the tensile and compressive strengths increased about 100% and 70%, respectively, at the strain rates of 10-100 $\textrm{sec}^{-1}$ compared to the quasi-static strengths while the strengths were little affected by the environmental temperature variation.

• Structural Engineering and Mechanics
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• 제74권3호
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• pp.435-443
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• 2020

The objective of this study was to determine the effective compressive strength of a column-slab connection with different compressive strengths between the column and slab concrete. A total of eight column specimens were fabricated, among which four specimens were restrained by slabs while the others did not have any slab, and the test results were compared with current design codes. According to ACI 318, the compressive strength of a column can be used as the effective compressive strength of the column-slab connection in design when the strength ratio of column concrete to slab concrete is less than 1.4. Even in this case, however, this study showed that the effective compressive strength decreased. The specimen with its slab-column connection zone reinforced by steel fibers showed an increased effective compressive strength compared to that of the specimen without the reinforcement, and the interior column specimens restrained with slabs reached the compressive strength of the column.

• 콘크리트학회논문집
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• 제26권4호
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• pp.449-456
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• 2014

지오폴리머 반응은 매우 복잡하며, 플라이애쉬 화학조성, 입도분포, 자극제 농도와 종류, 양생온도, 양생시간 등이 지오폴리머 물성에 많은 영향을 미치고 있는 것으로 알려져 있다. 이 연구에서는 양생조건이 플라이애쉬 기반 지오폴리머 강도에 미치는 영향을 실험하기 위하여, 양생온도, 고온양생 전 전치시간, 고온에서의 양생시간 등을 변화시켜 양생조건 변화에 따른 지오폴리머 페이스트의 압축강도, SEM, 공극특성 등에 대하여 분석하였다. 실험 결과 양생온도가 높을수록 지오폴리머의 강도는 증가하였으며, 전양생시간이 길어질수록 지오폴리머 강도는 증가되었으나, 고온양생에서의 양생시간이 길어지면 압축강도가 저하현상이 관찰되었다. 고온에서의 양생시간이 길어지면 공극구조의 변화에 따라 강도 저하 현상이 관찰되었다. 따라서 양생온도와 양생시간은 지오폴리머 강도 및 미세구조에 큰 영향을 미치고 있는 것을 확인할 수 있었다.