• Computers and Concrete
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• v.19 no.2
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• pp.153-159
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• 2017

In this study, the strength properties of alkali-activated silica fume (SF) mortars were investigated. The crushed limestone sand with maximum size of 0-5 mm and the sodium meta silicate ($Na_2SiO_3$) used to activate the binders were kept constant in the mortar mixtures. The mortar specimens using the replacement ratios of 0, 25, 50, 75 and 100% SF by weight of cement together with $Na_2SiO_3$ at a constant rate were produced in addition to the control mortar produced by only cement. Moreover, the mortar specimens using the replacement ratio of 4% titanium dioxide ($TiO_2$) by weight of cement in the same mixture proportions were produced. The prismatic specimens produced from eleven different mixtures were de-moulded after a day, and the wet or dry cure was applied on the produced specimens at laboratory condition until the specimens were used for flexural strength ($f_{fs}$) and compressive strength ($f_c$) measurement at the ages of 7, 28 and 56 days. The $f_{fs}$ and $f_c$ values of mortars applied the wet or dry cure were compared with the results of control mortar. The findings revealed that the $f_c$ results of the alkali activated 50% SF mortars were higher than that of mortar produced with Portland cement only. It was found that the $f_{fs}$ and $f_c$ of alkali-activated SF mortars cured in dry condition was averagely 4% lower than that of alkali-activated SF mortars cured in wet condition.

• Journal of the Korean Geotechnical Society
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• v.29 no.4
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• pp.45-56
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• 2013

In this study, a blast furnace slag with latent hydraulic property is used to cement granular soils without using Portland cement. When the blast furnace slag reacts with an alkaline activator, it can cement soils. The effect of amounts of blast furnace slag and types of alkaline activator on soil strength was investigated for resource recycling. Four different amounts of slag and six different activators (two naturals and four chemicals) were used for preparing specimens. The specimens were air-cured for 3 or 7 days and then tested for unconfined compressive strength (UCS). The UCS of cemented sand with slag increased, in the order of specimens mixed with potassium carbonate, calcium hydroxide, sodium hydroxide and potassium hydroxide. Chemical alkaline activator was better than natural alkaline activator. The maximum UCS of 3-days cured specimens was 3 MPa for 16% of slag with potassium hydroxide, which corresponded to 37% of one with 16% of high-early strength portland cement. As the amount of slag increased, the UCS and dry density of a specimen increased for all alkaline activator cases. As the curing time increased from 3 days to 7 days, the UCS increased up to 97%. C-S-H hydrates were found in the cemented specimens from XRD analyses. Cement hydrates were more generated with increasing amount of slag and they surrounded sand particles, which resulted in higher density.

• The Korean Journal of Ecology
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• v.27 no.1
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• pp.49-55
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• 2004

To verify growth properties of Carex kobomugi, above and belowground parts of C. kobomugi were surveyed on coastal sand dune at Sinduri, Choongnam Province from April, 2001 to June 2003. The results were the same as follows. In coastal sand dune, C. kobomugi followed Elymus mollis from mean high tide line. Density of C. kobomugi was the highest at unstable sand dune and 150 plants/㎡. And rates of flowering plant were 70% at unstable area and 10% at stable area. C.kobomugi is thus plant that adapted to unstable sand dune. Shoot distributed irregularly. The rhizome of C. kobomugi gradually decreased with the soil depth in unstable area, but mainly distributed to 20 ㎝ depth. New rhizome could be generated from the rhizome which was below 150 ㎝ depth or 5 years old. The number and length of new rhizome were related to biomass of previous year's shoot. That was, shoots which were below 0.5 and over 3 g/shoot in dry weight generated 1 and 5 rhizomes, respectively. And the mean lengths of rhizome from small (below 0.5 g) and large (over 3.0 g) shoots were 13.0 ㎝ and 57.6 ㎝, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.1
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• pp.65-72
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• 1983

Dry sand specimens for both normally consolidated and overconsolidated triaxial compression tests were prestressed on the path with five different coefficients of earth pressure 1.0, 3/4, 0.55, $K_0$ and 1/3. Deformation resistance of normally consolidated sand increased with increasing the initial stress for all coefficients of earth pressure during consolidation, and the deformation modulus at a certain initial stress showed a tendency to increase with increasing the coefficient of earth pressure. And deformation moduli($E_i$, $E_{50}$), were found to be proportional to the $n_{th}$ power of initial stresses[${\sigma}_{m0}{^{\prime}}$, ${\sigma}_{10}{^{\prime}}$, ${\sigma}_{30}{^{\prime}}$, $({\sigma}_1-{\sigma}_3)_0$] for both isotropically and anisotropically normally consolidated samples, where n varied from 0.37 to 0.92. Overconsolidated sand with the higher overconsolidation ratio showed the higher deformation modulus. It is concluded that the $K_0$-anisotropically consolidated triaxial compression test is necessary to obtain the more accurate value of in-situ deformation modulus.

• Journal of Conservation Science
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• v.31 no.1
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• pp.1-11
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• 2015

Seated Amitabha Triad at Muwisa Temple (Treasure No. 1312) had been known as wooden Buddha statue, but a precise safety inspection revealed that the statue is terracotta Buddha statue made with clay. The clay layer of Amitabha Triad was conserved due to its severe damage. In this study, experiments were conducted to produce the most appropriate filler for the conservation treatment of the seated Amitabha Triad. Mixed clay samples with various ratios were produced and surface hardening state, crack, color change, and shrinkage of the samples during dry process were measured. Loess, fine sand powder, and cotton were used to produce the mixed clay for the filler with six different ratios and then 12 different concentration glues made with glutinous rice glue, Pachymeniopsis Elliptica glue, and animal glue were added as adhesives. Total 72 types of samples were prepared and comparative study was conducted. As a result, when the mixed clay contains 2.5% cotton compared to the weight per cent of loess and fine sand powder and also loess and fine sand in the mixed clay have a 15:1 ratio, the mixed clay had the lowest shrinkage. Animal glue is considered as an appropriate glue since it had small color change, low physical property change and shringkage. Therefore, mixed clay (loess:fine sand=15:1) mixed with 15ml animal glue is likely to be a suitable filler for conservation treatment of the seated amitabha triad at the Muwisa Temple.

• Journal of the Korean Geotechnical Society
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• v.24 no.1
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• pp.91-99
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• 2008

The method to prepare the large cemented sand specimen for calibration chamber test by air-pluviation is investigated in this study. The uniformity of cemented specimen is evaluated by performing the CPTs, DMTs, and bender element tests in the calibration chamber. The sand particles, pre-wetted with 0.5% water content, are mixed with gypsum to provide the homogeneous coating of gypsum particles on the grain surface. It was shown that the pre-wetting of particle surface is effective to minimize the potential for segregation between sands and gypsum during air-pluviation. It was observed that the extreme void ratios ($e_{max}\;and\;e_{mix}$) of the mixture of pre-wetted sand and gypsum powder increase at lower gypsum content while those of the mixture of dry sand and gypsum decrease with increasing gypsum content. It was also shown from the test results that large cemented specimens reconstituted in calibration chamber by rainer system are quite uniform in vertical and horizontal directions.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.260-263
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• 2001

Mechanical properties have been accepted to be major factor to improve wear resistance. The effect of mechanical properties on wear resistance of 0.27C-0.70Ni-1.42Cr-0.20Mo steel was studied under various test conditions. It is clear that yield strength, tensile strength, impact value, and hardness are strongly related each other. Wear resistance tests as pin on plate type and dry sand / rubber wheel type proved to be that wear depends on mechanical properties. Microstructures were also observed to make clear the wear properties. At quenching and low temperature tempering, the specimen has a good wear resistance.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.368-373
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• 1998

Prepackaged system consists out of a dry mix which contains cement, sand, redispersible polymer powder and admixtures in the right proportions. The purpose of this study is to evaluate the quality of prepackaged-type polymer-modified mortar products using redispersible poly(ethylene-vinyl acetate)(EVA) powder. Polymer-modified mortars using the redispersible polymer powder with powdered with powdered shrinkage-reducing agent were prepared with cellulose fiber contents of 0, 0.5, 1.0% and shrinkage-reducing agent contents of 0, 4%, and tested for drying shrinkage, strength, adhesion in tension, water absorption. From the test results, the prepackaged-type polymer-modified mortar products with 4% of shrinkage-reducing agent content give good properties. and that their properties largely depends on the shrinkage-reducing agent content rather than the cellulose fiber contents.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.3
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• pp.19-26
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• 1999

The detectability of pipes buried in dry sand is investigated by using the GPR with self-designed bow-tie antenna. The antennas are covered with shielding structures to reduce the direct-coupling between the transmitting and receiving antennas. The ringing, due to finite length of the antenna, is decreased by performing resistive termination at the ends of the antennas. It is shown that without additional signal processing, the presence of various buried targets can be found by discriminating hyperbolic pattern in B-scan data.

• Geomechanics and Engineering
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• v.12 no.4
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• pp.675-688
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• 2017

The anchor block is a specially designed concrete member intended to withstand pullout or thrust forces from backfill material of an internally stabilized anchored earth retaining wall by passive resistance of soil in front of the block. This study presents small-scale laboratory experimental works to investigate the pullout capacity of a concrete anchor block embedded in air dry sand and located at different distances from yielding boundary wall. The experimental setup consists of a large tank made of fiberglass sheets and steel framing system. A series of tests was carried out in the tank to investigate the load-displacement behavior of anchor block. Experimental results are then compared with the theoretical approaches suggested by different researchers and codes. The appropriate placement of an anchor block and the passive resistance coefficient, which is multiplied by the passive resistance in front of the anchor block to obtain the pullout capacity of the anchor, were also studied.