• Journal of the Korea Concrete Institute
• /
• v.13 no.2
• /
• pp.184-191
• /
• 2001

Recently, as industrialization is rapidly growing and the standard of life is rising, the quantities of waste glasses have been hastily increased and most of them are not recycled but abandoned. It cause some problems such as the waste of natural resources and environmental pollution. Therefore, this study was conducted basic experimental research to analyze the possibilities of recycling of waste glasses(crushed waste glasses outbreaking from our country such as amber, emerald-green, flint and mixed) as fine aggregates for concrete. Test results of fresh concrete, slump and compacting factors decrease because grain shape is angular and air content increase due to involving small size particles so much in waste glasses. Also compressive, tensile and flexural strengths decrease with increase of the content of waste glasses. In conclusion, the content of waste glasses below 30% is reasonable and usage of pertinent admixture is necessary to obtain workability and air content.

• International Journal of Highway Engineering
• /
• v.11 no.2
• /
• pp.205-216
• /
• 2009

As a subsequent study, this paper presents a comparative evaluation of structural responses in asphalt pavements with stabilized foundations. The approach based on a finite element analysis which incorporates non-linear behaviors of pavement geomaterials is used to estimate each performance indicator under standard single axle loading condition. In addition, results from laboratory tests are used to provide physical and mechanical properties of stabilized geomaterials for analyzing various pavement structures. Changes in pavement responses with varying layer thickness and stabilizer contents were investigated. It is found that the effect of layer thickness and stabilizer content is a critical factor in structural response of stabilized pavements. Moreover, a design criterion is proposed for selecting minimum contents of stabilizer of coarse-grained geomaterials based on a result of unconfined compressive strength and proper layer thickness of foundations.

• Journal of Convergence for Information Technology
• /
• v.7 no.1
• /
• pp.67-73
• /
• 2017

Paper sludge ash, blast furnace slag, fine powder quicklime, anhydrous gypsum, and fly ash as the main ingredients were prepared to suit the salty soils of marine soils. The solidification component is a kind of recycled ceramic, and CaO plays an important role in solidification. The neutralization time after solidification was about 2 weeks, and the compressive strength was about 12N/mm2 in the mortar test after one week incubation with standard yarn. This is about 14 times stronger than the solidifying agent used in the metropolitan area. As a result of applying plate load test to saltous marine soils, we obtained the yield load that can pass the large scale even after 5 days. In the uniaxial compressive strength test, shear strength of about 300 kPa was obtained after 5 days. It will be useful for supplementing the soft ground in the area where marine reclamation is much like the Incheon area.

• Steel and Composite Structures
• /
• v.35 no.4
• /
• pp.463-474
• /
• 2020

In this paper, the influence of adding multi-walled carbon nanotube (MWCNT) on the pull behavior of steel and GFRP bars in ultra-high-performance concrete (UHPC) was examined experimentally and numerically. For numerical analysis, 3D nonlinear finite element modeling (FEM) with the help of ABAQUS software was used. Mechanical properties of the specimens, including Young's modulus, tensile strength and compressive strength, were extracted from the experimental results of the tests performed on standard cube specimens and for different values of weight percent of MWCNTs. In order to consider more realistic assumptions, the bond between concrete and bar was simulated using adhesive surfaces and Cohesive Zone Model (CZM), whose parameters were obtained by calibrating the results of the finite element model with the experimental results of pullout tests. The accuracy of the results of the finite element model was proved with conducting the pullout experimental test which showed high accuracy of the proposed model. Then, the effect of different parameters such as the material of bar, the diameter of the bar, as well as the weight percent of MWCNT on the bond behavior of bar and UHPC were studied. The results suggest that modifying UHPC with MWCNT improves bond strength between concrete and bar. In MWCNT per 0.01 and 0.3 wt% of MWCNT, the maximum pullout strength of steel bar with a diameter of 16 mm increased by 52.5% and 58.7% compared to the control specimen (UHPC without nanoparticle). Also, this increase in GFRP bars with a diameter of 16 mm was 34.3% and 45%.

• Journal of the Korean Ceramic Society
• /
• v.39 no.12
• /
• pp.1138-1142
• /
• 2002

Slag cement and supersulfated slag cement were fabricated by mixing blast furnace slag and ordinary portland cement and adapted to solidify/stabilize heavy metal contained hazardous waste sludge. In case of slag cement, it showed continuous increase of their compressive strengths, which is attributed to the formation of the C-S-H, ettringite and monosulfate with STS sludge. However, BF and COREX sludge has a different shape and composition. therefore, adequate compressive strength could not be achieved with this slag cement. In case of the mixture of the each sludge like the STS-BF or the STS-COREX, the compressive strength over the standard level for disposing the wastes could be obtained with slag cement. The supersulfated slag cement that contain accelerators was very effective in solidifying the COREX sludge, which was difficult to solidify using different cement and obtained high compressive strength only for 3 days.

• Journal of the Korean Geotechnical Society
• /
• v.35 no.1
• /
• pp.31-42
• /
• 2019

About 3% of Casein is included in milk and it accounts for 80% of milk's protein. It has an adhesive property when mixed with calcium hydroxide and sodium hydroxide solutions. It has been usually used to bond woods under dry condition but becomes weak when exposed to moisture. Such weakness is very critical when casein is applied for soil cementation under groundwater condition. Therefore, this study was aimed to protect such weakness by changing or adding certain ingredients of casein adhesive. Two types of cemented specimens were prepared with Nakdong river sand and tested for unconfined compressive strength and durability. Each specimen was mixed with casein or cement. Ingredients of casein binder suggested by the University of Wisconsin, which is called a standard casein recipe, was also prepared. This study tried 6 different types of casein binder recipe. Among them, one with 30% hydroxide calcium increase and 50% hydroxide sodium decrease compared with the standard casein was most effective. Based on the most effective casein recipe, cemented sand with 1-4% of casein ratio was prepared and tested. The unconfined compressive strength and durability index were 6,253kPa and 92% for the specimen with 4% of casein ratio and 1,500kPa and 62% for the one with 8% of cement ratio. Therefore, casein cemented sand showed better performance. In addition, over 3% of casein cemented sand had over 80% durability index.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.21 no.3
• /
• pp.433-452
• /
• 2019

This study deals with shotcrete reinforcing performance according to the amount of synthetic fiber (PP fiber) and proper evaluation method. The shotcrete compressive strength, flexural strength and flexural toughness were tested by setting the mixing amounts of steel fiber ($37.0kg/m^3$) and synthetic fiber (PP fiber) as parameters ($5.0kg/m^3$, $7.0kg/m^3$ and $9.0kg/m^3$). Particularly, circular panel flexural toughness test (Road and Traffic Authority, RTA) was performed to evaluate the shotcrete energy absorption capacity. As a result, the compressive strength and the bending strength of the steel fiber reinforced shotcrete were large, but the flexural toughness of the synthetic fibe (PP fiber) reinforced shotcrete was large. Therefore, synthetic fiber (PP fiber) reinforced shotcrete is considered to have a reinforcing effect comparable to that of steel fiber reinforced shotcrete. Analysis of the relationship between the flexural toughness and the energy absorption capacity of synthetic fiber (PP fiber) reinforced shotcrete revealed that the energy absorbing ability is exhibited at a flexural toughness lower than the allowable standard (3.0 MPa). (Class A: 2.55 MPa = 202J, Class B: 2.72 MPa = 282J, Class C: 3.07 MPa = 403J). As a result of this study, it can be concluded that the actual shotcrete support performance can be evaluated by evaluating the support performance of the shotcrete measured at less than the allowable standard (3.0 MPa) at the actual tunnel site.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.2C
• /
• pp.121-131
• /
• 2006

The strength standard of shotcrete in Korea is relatively lower than that in Europe where high-strength shotcrete has been developed and actively applied to the common practice, so it is hard to test a quality of high-strength shotcrete. In this study, field test was performed to find a solution improving the strength and a long-term durability on domestic shotcrete. In field test, a high-strength shotcrete was produced using high-quality additions and accelerators, and an effect of additions and accelerators was observed. In addition, quality test based on EFNARC was also performed. As a result of field test, a promotion ratio of early strength is 90~97% in case of using alkali-free accelerators, therefore, alkali-free accelerators had an effect on an increase of early strength on shotcrete. A compressive strength of shotcrete using Micro-silica fume was 45.2~55.8MPa and flexible strength was 5.01~6.66MPa, so a promotion ratio of strength was 37~79%, 17~61% respectively. It was showed that increment effect of strength by the silica fume replacement of 7.5~10% for cement mass was remarkable. As a result of test, it was possible to apply high-strength shotcrete to the domestic practice using high-quality additions such as Micro-silica fume and accelerators such as alkali-free.

• Structural Engineering and Mechanics
• /
• v.22 no.5
• /
• pp.541-562
• /
• 2006

This paper compares the performance of axially loaded concrete filled steel tube (CFST) columns cast using a conventionally vibrated normal concrete (NC) and a novel self-consolidating concrete (SCC) made with a new viscosity modifying admixture (VMA). A total of sixteen columns with a standard compressive strength of about 50 MPa for both SCC and NC were tested by applying concentric axial load through the concrete core. Columns were fabricated without and with longitudinal and hoop reinforcement (Series I and Series II, respectively) in addition to the tube confinement. The slenderness of the columns expressed as height to diameter ratio (H/D) ranged between 4.8 and 9.5 for Series CI and between 3.1 and 6.5 for Series CII. The strength and ductility of SCC columns were found comparable to those of their NC counterparts as the maximum strength enhancement in NC columns ranged between 1.1% and 7.5% only. No significant difference in strain development was found due to the presence of SCC or NC or due to the presence of longitudinal and hoop reinforcement. Biaxial stress development in the steel tube as per von Mises yield criterion showed similar characteristics for both SCC and NC columns. The confined strength ($f^{\prime}_{cc}$) of SCC was found to be lower than that of NC and $f^{\prime}_{cc}$ also decreased with the increase of slenderness of the columns. Analytical models for the prediction of confined concrete strength and axial strength of CFST columns were developed and their performance was validated through test results. The proposed models were found to predict the axial strength of CFST columns better than existing models and Code based design procedures.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.8 no.2
• /
• pp.165-182
• /
• 2006

In this study, field test was performed to investigate the strength-improvement effect of shotcrete mixed Micro-silica fume and shotcrete quality was estimated by EFNARC standard. Deterioration test combined the Freezing-thawing and Carbonation was also performed in order to investigate a long-term durability of high-strength shotcrete. As a result of test, the compressive strength of shotcrete using Micro-silica fume was 45.2~55.8MPa and flexible strength was 5.01~6.66MPa, so a promotion ratio of strength was 37~79%, 17~61% respectively. And the strength-improvement effect of strength by silica fume addition ratio of 7.5~10% for cement mass was more superior to the others. Due to relative dynamic modulus, mass decrease rate and carbonation progress of shotcrete mixed Micro-silica fume, it was especially realized that Micro-silica fume reduced deterioration caused by steel fiber and improved a long-term durability of shotcrete.