• Advances in concrete construction
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• v.2 no.4
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• pp.301-308
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• 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.

• Advances in concrete construction
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• v.11 no.3
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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.

• Structural Monitoring and Maintenance
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• v.11 no.2
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• pp.71-86
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• 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.

• Journal of Welding and Joining
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• v.23 no.4
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• pp.34-40
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• 2005

There have been numerous approaches to examine the bonding strengths of solder joints. However, despite the technical and practical limitations, the precedent test methods such as the ball shear and ball pull tests are being used in industrial applications. In this study, the optimum jaw pressure with the modified protrusion jaw was introduced in order to obtain higher successful rate f3r ball pull testing. Furthermore, the pull strengths and fracture modes of Sn-8Zn-3Bi, Sn-4Ag-0.7Cu, and Sn-37Pb eutectic solder after isothermal aging tests ($100^{\circ}C,\;150^{\circ}C$), were evaluated with the protrusion jaw. The pull strength-displacement hysteresis curves and fracture surfaces were carefully investigated to evaluate the correlation between the pull strengths and the fracture modes of each solder. In conclusion, it is verified that Au-Zn IMCs (Intermetallic Compounds) have a detrimental effect on the pull strengths and changed fracture modes of Sn-8Zn-3Bi solder. Meanwhile, the microstructure transformation influences the degradation of pull strengths of Sn-4Ag-0.7Cu and Sn-37Pb solders.

• Macromolecular Research
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• v.11 no.4
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• pp.291-295
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• 2003

Dextran as a candidate material for colon-specific drug delivery has been studied. Crosslinked dextran hydrogels were prepared by mixing dextran, $MgCl_2$, glutaraldehyde (GA) and polyethyleneglycol (PEG 400) in water. The dextran hydrogels were characterized by measuring equilibrium swelling ratios and mechanical strengths. Response surface methodology (Central Composite Design) was used to evaluate the swelling behaviors and mechanical strengths as functions of concentrations of $MgCl_2$, GA, and PEG 400, which was found to be useful for the evaluation. It showed that the swelling behavior and mechanical strengths were influenced significantly by PEG 400 and $MgCl_2$ concentrations.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.433-436
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• 2005

The Fly-ash makes an Alumino-silicate gel when it mixes an alkali or a silicate solution. This Alumino-silicate gel is produced to the activation of an alkali silicate. And this act to the binder and makes a combine of particles. This study involved mechanical strengths of an Alumino-silicate Gel based the Fly-ash with an alkali solution. NaOH, KOH were utilized to an alkali solution. The alkali solution concentration was varied from 6 to 12M and the some added also the Meta-kaolin, Waterglass so that it made high the mechanical performance. Based on the experimental result, the compressive strengths increased as the quantity of the Meta-kaolin increased. And a mechanical strengths appeared according to the concentration of an alkali solution so that it was different. XRD, FT-IR have been used to characterize mechanical performance.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.50-53
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• 2000

The effect of punching density on the mechanical and thermal properties of nonwoven needle-punched carbon/phenol composite was studied. The carbonized preforms were farmed into composites with phenol resin. The interlaminar shear, tensile and flexural strengths were increased with increasing punching density. However, excessive punching density decreased interlaminar shear and tensile strengths. Erosion rate of carbon/phenol composite was decreased with increasing punching density

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.12
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• pp.949-954
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• 2011

In this study, the characteristics and error ranges of the mechanical bonding strength were analyzed according to before and after thermal shock test for various chips of automotive application component using Sn-3.0Ag-0.5Cu solder. In the after thermal shock test, the mechanical bonding strengths tend to decrease, meanwhile decreasing rates of mechanical strengths were less then 12% at specimen's bonding area below 3.5$mm^2$, and were from 17 to 21% at specimen's bonding area above 12 $mm^2$. On the other hand, Specimen's mean deviation rates were about 5% at specimen's bonding area more than 12 $mm^2$. Inversely, at specimen's bonding area is less then 3.5 $mm^2$, mean deviation rates were increased to about 8%. It means that the smaller device size is, the larger mean deviation rate. In addition, error ranges and deviation rates of the mechanical bonding strengths may differ slightly depending on their bonding area. Furthermore, process conditions as well as method of mechanical reliability evaluation should be established to reduce the error ranges of bonding strength.

• Proceedings of the Korea Concrete Institute Conference
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• 1990.04a
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• pp.90-95
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• 1990

It is widely recognized that the strengths of reinforced concrete members have random characteristics due to the variability of the mechanical properties of concrete and steel, the dimensional error as well as incorrect placement of reinforcing bars. Statistical models of the variabilities of strengths of reinforced concrete members, therefore, need to be developed to evaluate the safety level implied in current practices. Based on the probabilistic models of basic factors affecting the R.C. member strengths, in this study, the probabilistic characteristics of member resistance have been studied through Monte Carlo simulation.

• Elastomers and Composites
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• v.55 no.1
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• pp.1-5
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• 2020

This study examined the effects of the addition of maleic anhydride-grafted polypropylene (PP-g-MA) and polyolefin elastomer (POE) on polyamide 66 (PA66) and polypropylene (PP) blends. The blends of PA66/PP with PP-g-MA and POE were prepared using a twin screw extruder. Mechanical testing results revealed that the tensile, flexural, and izod impact strengths of the blends were maximized at a PP-g-MA content of 2 phr. The increased mechanical strength of the blends with PP-g-MA was attributed to the compatibilizing effect of the PA66 and PP blends. In addition, as the POE content increased, the impact strength of the blends increased. However, at a high POE content, the tensile and flexural strengths decreased, seemingly because of the lower mechanical properties of POE.