• Journal of the Korean GEO-environmental Society
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• v.15 no.8
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• pp.51-58
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• 2014

In this research, the composite grounds including original clay and soil-cement were constructed for conducting uniaxial compression test. Strength and deformation properties were analysed using results of laboratory tests with variations of water content of clay, replacement ratio and cement content. Numerical simulation using 3D distinct element method was conducted for soil cement. For strength of composite ground that contains more than cement contents of 15 %, it is more effective to increase cement content than increase of replacement ratio. Strength and elastic modulus of composite ground could be predicted by regression equations using uniaxial compression strength of clay, cement content of soil cement and replacement ratio. For strength and elastic modulus of soil cement, which is most important things for predicting final strength and elastic modulus of composite ground, numerical simulation using the distinct element method adapted bonding model could be used to verify laboratory test, and predict strength and elastic modulus.

• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.4 s.23
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• pp.29-36
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• 2006

There are loss of lives and properties in many areas of the basin of the Nak-Dong river by the unusual weather and the localized heavy rain recently, and many difficulties of levee construction for prevention of disasters by acquisition of material and expensive transportation. In this research, The factors and causes which affect the strength through laboratory tests about the cemented sand that is mixed a few portland cement and sand of Nak-Dong river bed was researched closely. For providing the fundamental data which is needed in design and analysis of levee material, the compaction test and the standard triaxial compression test etc was conducted., analyzed compression strength and characteristic of stress-strain behavior in which the influence of cement content.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5C
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• pp.207-215
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• 2009

Cemented soils or concrete are usually cured under moisture conditions and their strength increases with curing time. An insufficient supply of water to cemented soils can contribute to hydration process during curing, which results in the variation of bonding strength of cemented soils. In this study, by the consideration of in situ water supply conditions, cemented sand with cement ratio less than 20% is prepared by air dry, wrapped, moisture, and underwater conditions. A series of unconfined compression tests are carried out to evaluate the effect of curing conditions on the strength of cemented soils. The strength of air dry curing specimen is higher than those of moisture and wrapped cured specimens when cement ratio is less than 10%, whereas it is lower when cement ratio is greater than 10%. Regardless of cement ratio, air dry cured specimens are stronger than underwater cured specimens. A strength increase ratio with cement ratio is calculated based on the strength of 4% cemented specimen. The strength increase ratio of air dry cured specimen is lowest and that of wrapped, moisture, and underwater cured ones increased by square. Strength of air dry cured specimen drops to maximum 30% after wetting when cement ratio is low. However, regardless of cement ratio, strength of moisture and wrapped specimens drops to an average 10% after wetting. The results of this study can predict the strength variation of cemented sand depending on water supply conditions and wetting in the field, which can guarantee the safety of geotechnical structures such as dam.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.2
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• pp.529-536
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• 2014

Physical characteristics of cement-admixed clay such as water content, specific gravity, unit weight and void ratio are main factors for strength, compressibility and prediction of consolidation behavior. In the past, the physical characteristics of admixed soils could be understanded through complex laboratory tests and field survey after construction. In this study, the tests were performed with conditions such as clay water contents 0%-170%, cement contents 5%-25% and curing period 3-90days after that analyzed for changes which are water content, specific gravity unit weight and void ratio of admixed soils. A prediction of properties through mechanical relationships with clay in situ water content, cement content and curing period could be proposed using the test results. The prediction equation of void ratio of admixed soils was derived using void ratio equation in geotechnical engineering and compared with test results of bangkok clay and then this study could be verified.

• Journal of the Korean GEO-environmental Society
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• v.3 no.2
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• pp.23-33
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• 2002

Examined a practical use possibility of paper fly ash that is industrial by-product as a stabilization/hardening agent. Performed unconfined compression test, scanning electron microscopy and pH analysis etc. for 100% paper fly ash-soil mixtures and each paper fly ash-soil mixtures that add cement as the second addition and sulfate component of small quantity for strength promotion and so on. In all cases, strength of admixtures increased according as curing time and mixing ratio increases but almost strength is revealed at mixing early and expressed maximum strength increase efficiency at mixing ratio 9% with raw soil. Compare with the case that use paper fly ash only, in case of cement amount 10~30% was included in paper fly ash, strength of admixtures increases two times and 40% was included, that increases from five to eight times.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.10
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• pp.23-29
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• 2020

The soil structures settle down continuously under cyclic dynamic loading after opening railway lines. This study examined the characteristics of the settlement and stiffness of cement-treated soils with the change in the content of fines under cyclic dynamic loading. Eighteen cases of the test were carried out with the changes in the fines content of soils, cement content, and curing days. Based on the test results, cement-treated soils containing more than 3% of cement could decrease settlement sufficiently even with a high portion of fines under cyclic dynamic loading. In addition, the elastic and plastic settlements could be reduced using 3 to 4% cement to the level of 1/4 and 1/6, respectively. In the viewpoint of stiffness, the resilient modulus of cement-treated soils increases with increasing cement content. Using more than 3% of cement, the 80MPa compaction stiffness standard for the upper subgrade of railways was satisfied, even with 40% of fines content of soils.

• Journal of the Korean Geotechnical Society
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• v.20 no.9
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• pp.125-131
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• 2004

A series of unconfined compression tests were carried out firstly to investigate mechanical behaviors of Lightweight Foamed Soil (LWFS) which is composed of dredged soils, cement and air foam. And secondly, to compare the difference of mechanical characteristic of LWFS with previous research conclusions (Yoon & Kim,2004) by using different dredged soils sampled at Joong-Ma in Gwangyang harbor area. Based on numberous laboratory experiments, it was found that deformation coefficient $(E_{50})$ of LWFS increases with increasing cement contents but decreases with increasing initial water contents of dredged soils. Appropriate regression formula (normalizing factor scheme) which considers relationship between LWFS composing elements, initial water contents of dredged soils, cement, air foam, and uniaxial compression strength or LWFS is proposed for practical applications. Finally, it was clear that, to apply LWFS method to practical projects, certain laboratory test would be necessary to take considerations of soil locality because mechanical charac-teristics of LWFS were surely dependent upon their sampled locations and properties.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4C
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• pp.213-220
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• 2008

A study on cemented sand reinforced with short fibers was carried out to improve its unconfined compressive strength and brittle behavior. Nak-dong River sand was mixed with Portland cement and polyvinyl alcohol (PVA) fibers. A PVA fiber widely used for concrete reinforcement is randomly distributed into cemented sand. Nak-dong River sand, cement and fibers with optimum water content were compacted in 5 layers and then cured for 7 days. The effect of fiber reinforcement rather than cementation was emphasized by using a small amount of cement. Weakly cemented sand with a cement/sand ratio less than 8% was fiber-reinforced with different fiber ratios and tested for unconfined compression tests. The effect of fiber ratio and cement ratio on unconfined compressive strength was investigated. Fiber-reinforced cemented sand with 2% cement ratio showed up to six times strength to non-reinforced cemented sand. Because of ductile behavior of fiber-reinforced specimens, an axial strain at peak stress of specimens with 2% cement ratio increases up to 7% as a fiber ratio increases. The effect of 1% fiber addition into 2% cemented sand on friction angle and cohesion was analyzed separately. When the fiber reinforcement is related to friction angle increase, the 8% of applied stress transferred to 1% fibers within specimens.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6C
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• pp.259-265
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• 2012

This paper investigates engineering characteristics of lightweight soils mixed with air foam and tire powder. Lightweight soils could be used as foundation materials, back-fills of reducing vibrating or abutment, and so on. Unconfined and triaxial compression tests were carried out to analyze strength and deformation characteristics of lightweight soils by changing target moist unit weight and cement contents. In comparison with strength characteristics of two different kinds of lightweight soils with same most unit weights ($13kN/m^3$), unconfined compression tests showed similar compressive strength, however, triaxial compression tests showed that compressive strength of lightweight soils mixed with waste tire powder was relatively larger strength than that of lightweight soils mixed with air foam because of elasticity of waste tire powder. Also, unconfined and triaxial compressive strengths of most of lightweight soils increase with increases of moist unit weight and cement contents. However, the strength of lightweight soils mixed with air foam under $11kN/m^3$, when moist unit weight exceeds a certain cement contents, decreases even though cement contents increase because of the effect in a void gap of air foam.

• Journal of the Korean Geotechnical Society
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• v.23 no.8
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• pp.159-169
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• 2007

The behavior of fiber-reinforced cemented sands (FRCS) was studied to improve a brittle failure mode observed in cemented sands. Nak-dong River sand was mixed with ordinary Portland cement and a Polyvinyl alcohol (PVA) fiber. A PVA fiber is widely used in concrete and cement reinforcement. It has a good adhesive property to cement and a specific gravity of 1.3. A PVA fiber has a diameter of 0.1 mm that is thicker than general PVA fiber for reinforced cement. Clean Nak-dong River sand, cement and fiber at optimum water content were compacted in 5 layers giving 55 blows per layer. They were cured for 7 days. Cemented sands with a cement/sand ratio of 4% were fiber-reinforced at different locations and tested for unconfined compression tests. The effect of fiber reinforcement form and distribution on strength was investigated. A specimen with evenly distributed fiber showed two times more strength than not-evenly reinforced specimen. The strength of fiber-reinforced cemented sands increases as fiber reinforcement ratio increases. A fully reinforced specimen was 1.5 times stronger than a specimen reinforced at only middle part. FRCS behavior was controlled not only by a dosage of fiber but also by fiber distribution methods or fiber types.