• Computers and Concrete
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• v.13 no.1
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• pp.31-47
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• 2014

This research is focused on obtaining the fracture property of steel fiber reinforced concrete(SFRC) specimens at early ages of 1, 2, 3 and 7-day, respectively. For this purpose, three point bending tests of nine groups of SFRC beams with notch of 40mm depth and different steel fiber ratios were conducted. The experimental results of early age specimens were compared with the 28-day hardened SFRC specimens. The test results indicated that the steel fiber ratios and curing age significantly influenced the fracture properties of SFRC. A reasonable addition of steel fiber improved the fracture toughness of SFRC, while the fracture energy of SFRC developed with curing age. Moreover, a quadratic relationship between splitting strength and fracture toughness was established based on the experiment results. Additionally, afinite element (FE) method was used to investigate the fracture properties of SFRC.A comparison between the FE analysis and experiment results was also made. The numerical analysis fitted well with the test results, and further details on the failure behaviors of SFRC could be revealed by the suggested numerical simulation method.

• Journal of Powder Materials
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• v.4 no.4
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• pp.243-251
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• 1997

Engine valve-shaped TiAl-Mn intermetallics containing 43.5 to 47.5at%Al (Mn/Al=0.036) are successively fabricated by reactive sintering the elemental powder mixtures near-net shaped by extrusion and die forging. A duplex structure consisted of lamellar grains and equiaxed $\gamma$ grains is developed for all compositions, and the areal fraction of the lamellar grains(or equiaxed $\gamma$ grains) decreases (or increases) with increasing Al content. As Al content increased, the elongation increases with accompanying decrease in yield strength and ultimate tensile strength at both room temperature and 80$0^{\circ}C$. This indicates that the suitable composition is Ti-45at%Al-1.6at%Mn in considering the balance of ambient and elevated tensile properties. The reactive-sintered Ti-45Al-1.6Mn alloy shows superior oxidation resistance not only to the plasma arc melted one but also to the heat resistance steel STR35(representative exhaust valve head material for automotive engine). The reactive-sintered Ti-45Al-1.6Mn alloy coated with an oxidizing scale exhibits a better wear resistance than induction hardened martensitic steel STR11(representative exhaust valve tip material for automotive engine).

• Computers and Concrete
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• v.25 no.1
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• pp.83-94
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• 2020

The use of fly ash in modern-day concrete technology aiming sustainable constructions is on rapid rise. Fly ash, a spinoff from coal calcined thermal power plants with pozzolanic properties is used for cement replacement in concrete. Fly ash concrete is cost effective, which modifies and improves the fresh and hardened properties of concrete and additionally addresses the disposal and storage issues of fly ash. Soft computing techniques have gained attention in the civil engineering field which addresses the drawbacks of classical experimental and computational methods of determining the concrete compressive strength with varying percentages of fly ash. In this study, models based on soft computing techniques employed for the prediction of the compressive strengths of fly ash concrete are collected from literature. They are classified in a categorical way of concrete strengths such as control concrete, high strength concrete, high performance concrete, self-compacting concrete, and other concretes pertaining to the soft computing techniques usage. The performance of models in terms of statistical measures such as mean square error, root mean square error, coefficient of correlation, etc. has shown that soft computing techniques have potential applications for predicting the fly ash concrete compressive strengths.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.223-224
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• 2009

This study was performed to development 80MPa high strength concrete using local raw material of Busan and to estimate field application ability. As the result of three types of mixture, fresh and hardened properties were satisfied with target requirement properties. Hydration temperature was revealed mean 75$\sim$85$\circ$C. Additionally, in case of compressive strength, core specimen's strength is six times higher than field curing specimen by very high hydration heat.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.11a
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• pp.89-92
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• 2008

This research analyzed the basic characteristics of unhardened concrete and the compression strength characteristics of hardened concrete according to liquidity retention agent mix rate change to improve the liquidity fluidity retention performance of high performance concrete, and produced the following results. The moment fluidity retention agent is added according to fluidity retention agent mix rate change, which increased fluidity retention agent mix rate, slump flow decreased, and in the case of slump flow according to the progress time change by the fluidity retention agent mix rates, the more fluidity retention agent mix rate increased, the lower slump flow change rate became. The moment fluidity retention agent is added according to fluidity retention agent mix rate change, fluidity retention agent mix rate increased compared to non-mixture of fluidity retention agent, and the air amount by progress time change by the fluidity retention agent mix rates slightly increased, however target range is still met and unit volume mass is inversely proportional to air amount. Compression strength according to age progress by the fluidity retention agent mix rates was shown to increase slightly with increase in fluidity retention agent mix rate, and yet the difference was not significant.

• Korean journal of food and cookery science
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• v.8 no.1
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• pp.1-7
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• 1992

Recently, plenty of imported Chinese Mungbean is sold, for Korean Mungbean is expensive. But they say, Chinese Mungean has less delicacy and cooking quality. Above all, in comparison with Korean and Chinese Mungbeans properties they are different - Chinese Mungbean grain is twice in dimension, Chinese Mungbean is white and Korean one is yellow in peeled grain color. They are similar in size shape with the microscope. With Amylograph of Brabender the viscosity of Korean Mungbean is gradually and continually increased until heating from $25^{\circ}C$ to $92.5^{\circ}C$ and cooling to $25^{\circ}C$ again, but the one of Chines Mungbean is increased suddenly in 74$^{\circ}C$ and shows the abrupt break-down phenomenon. This same phenomenon is shown in swelling with melting-pointer, In $25^{\circ}C$, the cooling temperature, Chinese Mungbean is measured to 1400 B.U and Korean one 1600 B.U. With color-meter of Richard S. Hunter, 12% gel of Korean Mungbean starch is clear but Chinese one white. The texture of 12% gel of Chinese Mungbean starch with Rheo-meter becomes hardened much more than Korea one. As a result of sensory-test, color, cohesiveness, and flavors of Korean gel is preferred overwhelmingly.

• Computers and Concrete
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• v.19 no.5
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• pp.555-566
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• 2017

Recently some efforts have been performed to combine the advantages of light-weight and self-compacting concrete in one package called Light-Weight Self-Compacting Concrete (LWSCC). Accurate prediction of hardened properties from fresh state characteristics is vital in design of concrete structures. Considering the lack of references in mixture design of LWSCC, investigating the proper mixture components and their effects on mechanical properties of LWSCC can lead to a reliable basis for its application in construction industry. This study utilizes wide range of existing data of LWSCC mixtures to study the individual and combined effects of the components on the compressive strength. From sensitivity of compressive strength to the proportions and interaction of the components, two equations are proposed to estimate the LWSCC compressive strength. Predicted values of the equations are in good agreement with the experimental data. Application of lightweight aggregate to reduce the density of LWSCC may bring some mixing problems like segregation. Reaching a higher strength by lowered density is a challenging problem that is investigated as well. The results show that, the compressive strength can be improved by increasing the of mixture density of LWSCC, especially in the range of density under $2000Kg/m^3$.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.1
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• pp.59-68
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• 2008

The experiment was carried out to investigate the influence of coarse aggregate, admixture, and accelerator on the properties of concrete. As the maximum size of coarse aggregate decreased from 13 mm to 8 mm, fluidity of fresh concrete declined but compressive strength and dynamic modulus of elasticity of hardened concrete increased remarkably. The mechanical properties of concrete substituted silica fume to the plain concrete improved, the compressive strength of that substituted blast furnace slag increased slightly. The hydration reaction and compressive strength of specimen with sodium luminate type accelerator were high at initial, but specimen with alkali free type accelerator improved largely in 28 days.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.737-740
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• 2003

In this study, the influence of cement factor on the early strength gain and the other properties of concrete is discussed. According to the result, the setting time is faster in order of alumina cement(AC), high-early-strength cement(HSC) and ordinary Portland cement(OPC), and when OPC are replaced with HSC and AC, the final setting time is faster than when only OPC is used. At 10% replacement of AC, the instant setting happens. As the particle of cement is minute, setting time is shortened. As the properties of hardened concrete, the time when compressive strength of 5㎫, which the form can be removed, is gained is about 18 and 16 hours in the case of OPC and HSC respectively, and in the case of AC, it is about 5 hours. It also shows 16 hours at the replacing ratio of HSC of 50%, and 26 and 72 hours at the replacing ratio of AC of 5 and 10% respectively. And it shows 21, 16 and 12 hours with variation of fineness of cement, so early strength gain is fast with an increase of fineness. The coefficient of correlation between compressive strength and the rebound value is over 0.97, is very favorable. Therefore, if the rebound value of P type Schmidt hammer is more than 25, it is thought that the side forms can be removed.

• Advances in Computational Design
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• v.3 no.3
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• pp.289-302
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• 2018

The use of optimum content of supplementary cementing materials (SCMs) such as limestone filler (LF) to blend with Portland cement has been resulted in many environmental and technical advantages, such as increase in physical properties, enhancement of sustainability in concrete industry and reducing $CO_2$ emission are well known. Artificial neural networks (ANNs) have been already applied in civil engineering to solve a wide variety of problems such as the prediction of concrete compressive strength. The feed forward back propagation (FFBP) algorithm and Tan-sigmoid transfer function were used for the ANNs training in this study. The training, testing and validation of data during the backpropagation training process yielded good correlations exceeding 97%. A parametric study was conducted to study the sensitivity of the developed model to certain essential parameters affecting the compressive strength of concrete. The effects and benefits of limestone filler on hardened properties of the concrete such as compressive strength were well established endorsing previous results in the literature. The results of this study revealed that the proposed ANNs model showed a high performance as a feasible and highly efficient tool for simulating the LF concrete compressive strength prediction.