• Applied Chemistry for Engineering
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• v.23 no.5
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• pp.480-484
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• 2012

Concrete, the mixture of cement, sand, gravel and water, is a suspension substance extensively used to construct building materials. When a concrete mortar is applied to the underwater construction, the rheology of concrete is of great importance to its flow performance, placement, anti-washout and consolidation. In this research, the anti-washout and rheological properties of concrete have been investigated with concrete admixtures prepared by adding anionic surfactants, cationic surfactants, and polymeric thickeners. The concrete mortar formulated by pseudo-polymeric systems with the electrostatic association of anionic and cationic surfactants, showed high viscosities and suitable anti-washout properties, but poor pumpabilities. The addition of poly methyl vinyl ether to the mixed surfactant system exhibits synergistic effects by improving the concrete mortar properties of the concrete mortar such as fluidity, visco-elastic property, self-leveling, and anti-washout.

• Corrosion Science and Technology
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• v.7 no.6
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• pp.350-361
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• 2008

Canada's oil sands contain one of the largest reserves of oil in the world. According to recent estimates, there are nearly 180 billion barrels of oil in the Canadian oil sands trapped in a complex mixture of sand, water and clay. More than 40 companies have been currently operating or developing oil sands facilities since the first production in 1967. The process of oil sands upgrading is similar with down stream refinery, but the corrosion environment in upgrading refinery is often more severe than in the refinery because of high chlorides, mineral contents, carbonic acid, heavy viscosity and fouling, higher naphthenic acid [$NA-R(CH_{2})nCOOH$], and greater sulfur contents. Naphthenic acid corrosion (NAC) which is one of the most critical corrosion issues in up & downstream refinery plants was observed for the first time in 1920's in refinery distillation processes of Rumania, Azerbaizan (Baku), Venezuela, and California. As a first API report, the 11th annual meeting stated sources and mechanism of NAC in early 1930's. API has been developing the risk base standards, such as API RP580, 571, and Publication 581 which are based on the worst NAC damage in the world since 2000. Nevertheless not only the NAC phenomena and control in Canadian sands oil process are not much widely known but also there are still no engineering guidances for the Canadian sands oil in API standards. This paper will give NAC phenomina and materials selection guidance against NA environment in Canadian oil sands upgrading processes.

• Structural Engineering and Mechanics
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• v.60 no.6
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• pp.939-952
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• 2016

A compression to tensile load transforming (CTT) device was developed to determine indirect tensile strength of concrete material. Before CTT test, Particle flow code was used for the determination of the standard dimension of physical samples. Four numerical models with different dimensions were made and were subjected to tensile loading. The geometry of the model with ideal failure pattern was selected for physical sample preparation. A concrete slab with dimensions of $15{\times}19{\times}6cm$ and a hole at its center was prepared and subjected to tensile loading using this special loading device. The ratio of hole diameter to sample width was 0.5. The samples were made from a mixture of water, fine sand and cement with a ratio of 1-0.5-1, respectively. A 30-ton hydraulic jack with a load cell applied compressive loading to CTT with the compressive pressure rate of 0.02 MPa per second. The compressive loading was converted to tensile stress on the sample because of the overall test design. A numerical modeling was also done to analyze the effect of the hole diameter on stress concentrations of the hole side along its horizontal axis to provide a suitable criterion for determining the real tensile strength of concrete. Concurrent with indirect tensile test, the Brazilian test was performed to compare the results from two methods and also to perform numerical calibration. The numerical modeling shows that the models have tensile failure in the sides of the hole along the horizontal axis before any failure under shear loading. Also the stress concentration at the edge of the hole was 1.4 times more than the applied stress registered by the machine. Experimental Results showed that, the indirect tensile strength was clearly lower than the Brazilian test strength.

• Advances in concrete construction
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• v.8 no.1
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• pp.65-76
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• 2019

This paper investigates the effect of recycled glass powder (RGP) on flowing properties of self-compacting mortars (SCMs) containing different ratios of fillers and superplasticizer dosages. Fly ash (FA), nano-silica (NS), micro-silica (MS), metakaolin (MK) and rice husk ash (RHA) are used as fillers and their synergistic effect with RFP is studied. The effects of fillers and high-range water reducer (HRWR) on flowing ability of mortars are primarily determined by slump flow and V-funnel flow time tests. The results showed that for composites with a higher RGP content, the mortar flowing ability increased but tended to decrease when the composites containing 10% MK or 5% RHA. However, the flowing ability of samples incorporating 5% RGP and 10% SF or 25% FA showed an opposite result that their slump flow spread decreased and then increased with increasing RGP content. For specimens with 3% NS, the influence of RGP content on flowing properties was not significant. Except RHA and MS, the fillers studied in this paper could reduce the dosage of HRWR required for achieving the same followability. Also, the mixture parameters were determined and indicated that the flowability of mixtures was also affected by the content of sand and specific surface area of cement materials. It is believed that excess fine particles provided ball-bearing effect, which could facilitate the movement of coarse particles and alleviate the interlocking action among particles. Also, it can be concluded that using fillers in conjunction with RGP as cementitious materials can reduce the material costs of SCM significantly.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.6
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• pp.645-653
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• 2021

Biopolymer is a general concept for high molecular compounds produced by living organisms. Among them, the xanthan and β-glucan, which are organic polymer mixture produced by micro-organisms, are mainly used to increase the viscosity of a substance. And diluting in water and mixing with sand or clay can increase compressive strength and shear strength. In this study, mixed soil prepared by mixing soil with xanthan and beta-glucan based biopolymers specially developed for the purpose of increasing soil strength was applied to the river bank revetment, and changes during winter were measured using ground LiDAR. As a result of analyzing winter changes in major sections using three-dimensional point cloud data obtained through ground LiDAR, there were no changes to the extent that it was difficult to confirm with the naked eye in the two sections coated with biopolymer blended soil. However, soil loss due to Rill erosion was confirmed in the natural embankment section where biopolymer blended soil was not used.

• Structural Engineering and Mechanics
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• v.90 no.5
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• pp.467-480
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• 2024

The mechanical properties and durability of concrete pavements may be degraded in extreme situations, resulting in the need for partial repair or total replacement. During the past few decades, there has been a growing body of research on substituting a portion of Portland cement with alternative cementitious materials for improving concrete properties. In this study, two different configurations of powdered and granulated blast furnace slag were implemented, replacing fine aggregates (by 12 wt.%) and Portland cement (by 0, 20, 40, and 60 wt.%) in the making of roller-compacted concrete (RCC) mixes. The specimens were fabricated to investigate the mechanical properties and durability specifications, involving freeze-thaw, salt-scaling, and water absorption resistance. The experimental results indicated that the optimum mechanical properties of RCC mixes could be achieved when 20-40 wt.% of powdered slag was added to concrete mixes containing slag aggregates. Accordingly, the increases in compressive, tensile, and flexural strengths were 45, 50, and 28%, in comparison to the control specimen at the age of 90 days. Also, incorporating 60 wt.% of powdered slag gave rise to the optimum mix plan in terms of freeze-thaw resistance such that a negligible strength degradation was experienced after 300 cycles. In addition, the optimal moisture content of the proposed RCC mixtures was measured to be in the range of 5 to 6.56%. Furthermore, the partial addition of granulated slag was found to be more advantageous than using entirely natural sand in the improvement of the mechanical and durability characteristics of all mixture plans.

• Journal of the Korean GEO-environmental Society
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• v.17 no.1
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• pp.5-12
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• 2016

Investigation of in-situ ground in cold region is difficult due to low accessibility and environmental factors. In this study, correlation between dynamic cone resistance and shear strength is suggested to estimate the strength of frozen soils by using instrumented dynamic cone penetrometer. Tests were conducted in freezing chamber after preparing sand-silt mixture with 2.3% water content. Vertical stresses of 5 kPa and 10 kPa were applied during freezing, shearing, and penetration phase to compare the dynamic cone resistance and shear strength. The dynamic cone resistance, additionally, is calculated to minimize the effect of energy loss during hammer impact. Experimental results show that as the shear strength increases, the dynamic cone penetration index (DCPI) decreases nonlinearly, while the dynamic cone resistance increases linearly. This study provides the useful correlation to evaluate strength properties of the frozen soils from the dynamic cone penetration and direct shear tests.

• Conservation Science in Museum
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• v.25
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• pp.35-50
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• 2021

This study analyzed the basic properties of soil material gathered around Maegok-dong in Gwangju, Gyeonggi-do Province (hereafter, "Maegok soil") and the physicochemical changes in the Maegok soil resulting from the addition of other clay materials in order to present scientific information about the properties of clay available for pottery production. Gravel, coarse sand, and fine sand account for 73% of the total mass of the Maegok soil. Therefore, it required refinement through sifting in order to serve in pottery clay. After sifting, the amount of silt and clay in the soil increased to 95% of the total mass. However, since it lacked plasticity and viscosity, buncheong soil was added. When it was mixed with bungcheong soil at a ratio of 7:3, Maegok soil improved as pottery clay as its viscosity increased, demonstrating compositional properties appropriate for ceramic clay even after firing. Further, its water-absorption rate was decreased to 0.40. This means that soil gathered from anywhere can be used for pottery-making by refining its original properties and through mixture with clay with specific components which help the pottery maintain its shape even after firing.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.104-112
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• 2019

The material properties of the 3D printing cement composite mortar were evaluated, and the performance range in which printing was possible was calculated using the void ratio in a fresh state as a single index. As a results of the tests, as the water-binder ratio (W/B) increased, the mortar flow value increased and the density and strength decreased. As the sand-binder ratio (SS/B) increased, the mortar flow value decreased. However, strength and density increased and decreased up to a certain SS/B. As admixture-binder ratio (Ad/B) increased, mortar flow value, density, and strength decreased. These trends make it difficult to mix-design to meet the target performances of 3D printing mortars, represented by extrudability and buildability. The value of mortar flow increased proportionally with the void ratio, while the density and strength apparently decreased as the void ratio increased. This indicates that void ratio can be utilized as a single index for controlling the material properties in the design of mortar mixtures. It was found that mortar mixture could be printed by a 3D printer when the void ratio was in the range from 0.6 to 0.7. This was verified by printing a mortar which has the void ratio of 0.634. The mortar was produced with the mixture design of W/B 35.0%, SS/B 60.0%, and Ad/B 0.1%. Further research applying diverse admixtures is needed to improve the quality of 3D printing output mortars.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.11
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• pp.747-752
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• 2014

Iodine-131, an artificial radionuclide, mostly exists as iodide ion ($^{131}I^-$) and iodate ion ($^{131}IO_3{^-}$) in the water, and When a short time contacted, it could not be removed by poly aluminum chloride (PACl) and powdered activated carbon (PAC). Although the removal rate of iodine-131 was not related with turbidity of raw water, it showed linear relationship with contact time with PAC. With the mixture of PACl (24 mg/L or more) and PAC (40 mg/L or more), about 40% of iodine-131 could be removed. Iodine-131 could be removed little by sand filtration, but approximately 100% by granular activated carbon (GAC), both virgin-GAC and spent-GAC. Microfiltration process could remove little iodine-131 while reverse osmosis process could remove about 92% of iodine-131.