• Geomechanics and Engineering
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• v.3 no.3
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• pp.207-218
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• 2011

This article describes laboratory research done on strength evaluations for stabilized samples made of tropical fibrous peat. The stabilizing agents used were ordinary Portland cement (OPC) as binding agent and blast furnace slag (BFS) as additive. Stabilized samples were tested for their strength through unconfined compressive strength (UCS) and California bearing ratio (CBR). Different dosage rates of OPC and BFS were used in trial and error experiments for the most effective combination for stabilized peat samples that were at their natural moisture content. Stabilized trial samples were air cured for 90 days. After detecting the most effective dosage rate in the trial samples, their values were used to prepare CBR samples at their optimum moisture content (OMC). CBR samples were then air cured from 1 to 90 days and tested under un-soaked and soaked conditions. The most effective dosage rate for the stabilized peat samples was found to be close to when 75% for OPC and 25% of BFS per total weight of OPC, and BFS. As an example, if 11.25% OPC, and 3.75% BFS are mixed with peat and compacted at their OMC and air cured for 90 days, stabilized peat will have an increase in CBR of 0.8% to 45 % for un-soaked and 20% for soaked conditions.

• Geomechanics and Engineering
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• v.14 no.3
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• pp.301-306
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• 2018

Stabilization of clayey soil has been studied from past to present by mixing different additives to the soil to increase its strength and durability. In recent years, there has been an increasing interest in stabilization of soils with natural pozzolans. Despite this, very few studies have investigated the impact of pozzolanic additives under freeze-thaw cycling. This paper presents the results of an experimental research study on the durability behavior of clayey soils treated with lime and perlite. For this purpose, soil was stabilized with 6% lime content by weight of dry soil (optimum lime ratio of the the soil), perlite was mixed with it in 0%, 5%, 10%, 20%, 25% and 30% proportions. Test specimens were compacted in the laboratory and cured for 7, 28 and 84 days, after which they were tested for unconfined compression tests. In addition to this, they were subjected to 12 closed system freeze-thaw cycles after curing for 28 days. The results show that the addition of perlite as a pozzolanic additive to lime stabilized soil improves the strength and durability. Unconfined compressive strength increases with increased perlite content. The findings indicate that using natural pozzolan which is cheaper than lime, has positive effect in strength and durability of soils and can result cost reduction of stabilization.

• Journal of the Korean Society of Industry Convergence
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• v.13 no.2
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• pp.99-106
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• 2010

The effects of additive and shrinkage reducing agent on the drying and autogenous shrinkage of high strength concrete are investigated in this study. As results, when the ratio of W/B(low water to binder ratio) increase, the compressive strength is decreased. Comparing with PC(portland cement) concrete, the strength is 2.8%, 3.2% and 3.8% lower respectively than that of PC when concrete mixing ratio is 0.2%, 0.3% and 0.4% in 28 days curing. Drying shrinkage strain of PC concrete showed $-650{\times}10^{-6}$ in 91 days curing. When SR(shrinkage reducing agent) of 0.2%, 0.3% and 0.4% is mixed, the drying shrinkage strains are 21%, 34% and 41% lower than those of PC in 91 days curing. Autogenous shrinkage strain of PC concrete appeared $-480{\times}10^{-6}$ in 56 days curing. When SR of 0.2%, 0.3% and 0.4% is mixed, the autogenous drying shrinkage strain are 12.5%, 19.8% and 33.3% lower than those of PC in 56 days curing. In cases of using the mineral and shrinkage agent or only using a shrinkage reducing agent also appeared same reducing effects for drying shrinkage and autogenous shrinkage.

• Environmental Engineering Research
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• v.24 no.2
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• pp.246-253
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• 2019

This study was conducted to explore the optimum proportion of zeolite and zeolite-kaolin as additives to cement clinker and gypsum samples, while maintaining the strength properties of produced environmentally sustainable cements. According to the British standard method, zeolite was added to cement clinker in proportions of 5-12% and 10-12% by weight, respectively, in the preparation of samples of zeolite-containing cement and zeolite-kaolin-based cement. Kaolin was used as a second additive as 10-20% of the total weight. The compressive strength tests were performed on base cement samples according to a standard procedure given in ASTM C109 Compressive Strength of Hydraulic Cement. These values were compared with those of the reference sample and the Omani allowable limits. The results indicated that the best compressive strength values were obtained with 88% cement clinker, 5% gypsum, and 7% zeolite for the zeolite-containing cement. Quantities of 70% cement clinker, 5% gypsum, 10% zeolite, and 15% kaolin gave the best results for zeolite-kaolin-based cement, resulting in a substitution of than 25% cement clinker. The study concluded that the partial cement clinker replacement using zeolite/kaolin combination may have a great influence on the reduction of $CO_2$ emission and energy saving in cement manufacturing.

• Geomechanics and Engineering
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• v.28 no.3
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• pp.239-253
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• 2022

Suitable techniques to stabilize organic soil and improve its engineering behaviour are in demand. Despite various alternatives, nano-additives proved to be an effective stabilizer owing to their strength enhancing properties. The study focuses on using nano-silica as a potential stabilizer to improve organic silt. Soil was treated with four dosages of nano-silica namely 0.2%, 0.4%, 0.6% and 0.8% of dry weight of the soil. Nano-silica treated soil showed a strength increase of nearly 25% at a dosage of 0.4% after curing for two hours. Strength of the treated soil improved with age. Strength improved by nearly 62.9% after 28 days of curing and 221.4% after 180 days of curing due to formation of Calcium - Silicate - Hydrate (CSH) gel in the soil matrix. Dosage of 0.6% nano-silica is observed to be the optimum dosage. Coefficient of permeability and compression index showed an increase by 13.32 and 5.5 times respectively owing to aggregation of particles and creation of void spaces as visualized from the scanning electron micrographs. Further model foundation study and numerical parametric studies using PLAXIS 2D indicate that optimized and economic results can be obtained by varying the additive dosage with depth.

• Structural Engineering and Mechanics
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• v.82 no.4
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• pp.543-556
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• 2022

Fly ash (FA) is the main additive to concretes currently produced. This substitute of ordinary Portland cement (OPC) have a positive effect on the structure and mechanical parameters of mature concrete. Unfortunately, the problem of using FA as the OPC replacement is that it significantly reduces the performance of concretes in the early stages of their curing. This limits the possibility of using this type of concrete, e.g., in the prefabrication, where it is required to obtain high strength composites after short periods of their curing. In order to minimize these negative effects, research has been undertaken to increase the early strength of the concretes with FA through the application of a specially dedicated chemical nanoadmixture (NA) in the form of seeds of the C-S-H phase. Therefore, this paper presents results of tests of modified concretes both with the addition of FA and with NA. The analyses were carried out based on the results of the macroscopic and microstructural tests in 5 time periods, i.e. after: 4, 8, 12, 24 and 72 hours. The greatest increase in mechanical strength parameters and rapid development of the basic matrix phases in composites in the first 12 hours of composites curing was observed.

• Journal of the Korean Society of Industry Convergence
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• v.27 no.2_2
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• pp.371-375
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• 2024

Epoxy resins are widely used in various fields due to their high adhesion, mechanical strength, and solvent resistance. However, as the volume decreases during the hardening process and the cooling process after hardening, stress is generated and when an external force is applied, the brittle material exhibits destruction behavior. To complement this, research has been conducted using inorganic nanofillers such as halloysite nanotube(HNT). HNT has a nanotube structure with the chemical formula of Al₂Si₂O₅(OH)₄·nH₂O and is a natural sediment of aluminosilicate. It has been used as additive to improve the mechanical properties of epoxy composites with exchange of amine group as a terminal functional group. In order to simplify complicated procedures of common wet method, a dry coating machine was designed and used for amine group exchange in previous research. In this study, they were applied as filler in epoxy composites, and mechanical properties such as tensile strength and flexural strength of composites were examined.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.3
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• pp.63-71
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• 2022

In this study, the interfacial reaction and drop impact reliability of Sn-Ag-Cu (SAC) solder and electroless nickel autocatalytic gold (ENAG) were studied. In addition, the solder joint properties with the ENAG surface finish was compared with electroless nickel immersion gold (ENIG) and electroless nickel electroless palladium immersion gold (ENEPIG). The IMC thickness of SAC/ENAG and SAC/ENEPIG were 1.15 and 1.12 ㎛, respectively, which were similar each other. The IMC thickness of the SAC/ENIG was 2.99 ㎛, which was about two times higher than that of SAC/ENAG. Moreover, it was found that the IMC thickness of the solder joint was affected by the metal turnover (MTO) condition of the electroless Ni(P) plating solution, and it was found that the IMC thickness increased when the MTO increased from 0 to 3. The shear strength of SAC/ENEPIG was the highest, followed by SAC/ENAG and SAC/ENIG. It was found that when the MTO increased, the shear strength was lowered. In terms of brittle fracture, SAC/ENEPIG was the lowest among the three joints, followed by SAC/ENAG and SAC/ENIG. Likewise, it was found that as MTO increased, brittle fracture increased. In the drop impact test, it was confirmed that the 0 MTO condition had a higher average number of failures than the 3 MTO condition, and the average number of failures was also higher in the order of SAC/ENEIG, SAC/ENAG, and SAC/ENIG. As a result of observing the fracture surface after the drop impact, it was found that the fracture was between the IMC and the Ni(P) layer.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.3
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• pp.330-337
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• 2021

3D printing is not only at the fundamental study and small-scale level, but has recently been producing buildings that can be inhabited by people. Buildings require a lot of cost and labor to work on the form work, but if 3D printing is applied to the building, the construction industry is received attention from technologies using 3D printing as it can reduce the construction period and cost. 3D printing technology for buildings can be divided into structural and non-structural materials, of which 3D printing is applied to non-structural materials. Because 3D printing needs to be additive manufacturing, control such as curing speed and workability is needed. Since cement mortar has a large shrinkage due to evaporation of water, cement polymer dispersion is used to improve the hardening speed, workability, and adhesion strength. The addition of polymer dispersion to cement mortar improves the tensile strength and brittleness between the cement hydrate and the polymer film. Cement mortar using polymer materials can be additive manufacturing but it has limited height that can be additive manufacturing due to its high density. When light-weight materials are mixed with polymer cement mortar, the density of polymer cement mortar is lowered and the height of additive manufacturing, so it is essential to use light-weight materials. However, the use of EVA redispersible polymer powder and light-weight materials, additional damage such as cracks in cement mortar can occur at high temperatures such as fires. This study produced a test specimen incorporating light-weight materials and EVA redispersible polymer powder to produce exterior building materials using 3D printing, and examined flame resistance performance through water absorption rate, length change rate, and cone calorimeter test and non-flammable test. From the test result, the test specimen using silica sand and light-weight aggregate showed good flame resistance performance, and if the EVA redispersible polymer powder is applied below 5%, it shows good flame resistance performance.

• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.397-404
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• 2006

This paper investigates experimentally the effect of combined addition of expansive additive and shrinkage reducing agent(SRA) on setting time, compressive strength and drying shrinkage of concrete. An increase of EA and SRA content leads to a reduction in flowability, which causes the increase of superplasticizer dosage, while air content increases. For setting time, in spite of increased superplasticizer dosage, with the increase of EA and SRA, setting time shortens. This is due to the presence of alkali ion by SRA and the faster formation of ettringite. At dosage of 5.0% of EA, concrete has the highest compressive strength and above that dosage, compressive strength decreased. On the contrary, the increase of SRA dosage results in a decrease in compressive strength. Combined addition of EA of 5.0% and SRA of 1.0% shows a comparable strength with control concrete. For drying shrinkage, as expected, the increase of EA and SRA dosage leads to reduction of drying shrinkage markedly. Moreover, combined addition of EA and SRA has better drying shrinkage reduction effect than individual use of EA and SRA by as much as $5{\sim}16%$. Optimal combination of EA and SRA is fixed at 5.0% of EA and 0.5% of SRA based on the consideration of the effect of EA and SRA on fresh state, compressive strength and shrinkage of concrete.