• International Journal of Highway Engineering
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• v.6 no.3 s.21
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• pp.65-77
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• 2004

Deformational characteristics of subbase materials are important parameters in the mechanistic design of pavement. The subbase materials are mostly unbound granular materials in Korea, and seven representative subbase materials were collected for testing from the pavement construction sites. To evaluate the deformational characteristics of subbase materials, RC/TS, TX and FF-RC tests were performed. The effects of various variables on modulus were studied. The variation in the modulus with number of loading cycles and loading frequency are very small and can be ignored in a practical sense. The modulus of subbase materials were significantly affected by confining pressure and strain level. The representative modulus reduction curve and constitutive models for Korean subbase materials were suggested.

• International Journal of Highway Engineering
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• v.2 no.2
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• pp.149-161
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• 2000

The stiffness of the subbase materials is represented by the resilient modulus, $M_R$, which are very important properties in the mechanistic design of flexible pavement system. However, the cyclic $M_R$ testing method is too complex, expensive, and time consuming to be applicable on a production basis. In this study, the alternative $M_R$ testing technique for subbase materials was developed using a free-free resonant column (FF-RC) test considering deformational characteristics of subbase materials. To estimate the deformational characteristics of subbase materials, effects of strain amplitude and mean effective stress on modulus of subbase materials were investigated. The $M_R$ values determined by alternative testing procedures matched well with those determined by standard $M_R$ test, showing the capability of the proposed methods being used in determining $M_R$ values.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3D
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• pp.331-338
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• 2008

Road pavements consist of layered structure and each layer is made of various materials. The load responses of pavement structures are very sensitive to properties of subbase materials. Successful pavement design, therefore, depends on the method and the accuracy of measuring material properties, and it requires realistic description of the behavior of layered materials. Resilient modulus ($M_R$) is widely used properties representing pavement structure materials. In this study, we collected data for mechanical characteristics of subbase materials that were used in domestic construction and adopted them to form a constitutive equation of subbase $M_R$ value. Proposed model was evaluated through the finite element analysis.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.657-664
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• 2000

Weak and soft compressible clay deposits are commonly found in natural subgrade soils. These Soils need to be stabilized for using the subbase materials of highway constructions. This paper presents that a chemical treatment using chemical additives comprised of sulfate(SO$_4$) and chloride(Cl) is evaluated for stabilizing soft clay deposits and lime. The physical and mechanical characteristics of soil-lime and additives are described by means of a laboratory study. The study results indicate that the presence of chlorides encouraged the efficiency of lime stabilization, and the use of calcium chloride with quicklime is the best additive for improving soil behavior. The treated soil with lime-calcium chloride can have the adaptability to the subbase materials of highway constructions.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.89-98
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• 2010

Recently, many researches on bottom ash which is produced in the burning process of power plant are actively performed for its utilization for soil-subbase materials. In this paper, bottom ashes from 5 different power plants are prepared and several tests including compaction, CBR, and tri-axial compression are carried out for mixed bottom ash and weathered soil considering 3 replacement ratio of 30%, 50%, and 70%. Through the tests, CBR result over 20 are evaluated without plastic property, which shows availability of subbase material. With higher increase in replacement ratio of bottom ash, CBR of mixed soil increases due to the higher mechanical performance of bottom ash. However, replacement effects of bottom ash on friction angle and cohesion are evaluated to be little since bottom ash plays a little role in rearrangement of mixed soil. Bottom ash with a good mechanical property is evaluated to have reasonable bearing capacity which shows a good property for subbase materials.

• Journal of the Korean Geotechnical Society
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• v.20 no.4
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• pp.57-63
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• 2004

The range of stresses experienced in subgrade soils and subbase materials in pavement under working stress conditions is below about 150㎪. Therefore, the deformational characteristics of soils at low confining pressures are important properties in the analysis and design of pavement system. Subgrade soils and subbase materials were collected from the actual pavement projects for testing. To evaluate the effect of confining pressure on modulus of those materials at low confining pressures, RC and FFRC tests were performed. Interestingly, the relationship between modulus of soils and confining pressure is more appropriate in linear space than in logarithm space at low confining pressure. Based on those results, new model fur evaluating the effects of confining pressure on modulus at low confining pressures was proposed.

• International Journal of Highway Engineering
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• v.3 no.2 s.8
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• pp.103-112
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• 2001

This study was performed to evaluate applicability of recycled aggregates as subbase and surface concrete materials for cement concrete pavement. Laboratory compaction test, CBR test and plate load bearing test were conducted to evaluate applicability for pavement subbase materials. Recycled concrete for surface course was manufactured with a design strength of $280kgf/cm^2$. Normal coarse aggregate was substituted with recycled aggregates with five different ratios, 0%, 20%, 40%, 60% and 80% for recycled concrete mixes. Fresh concrete Properties, concrete strength properties for the five substitution percentages of recycled aggregates after 28-day curing and freezing-and-thawing resistance were evaluated experimentally. Based on the experimental results, it was concluded that the recycled aggregate was the material good enough to use for subbase material, and 40% or lower substitution ratio was an appropriate percentage of recycled aggregates replacement for surface concrete.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.1103-1109
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• 2010

In this paper in order to analyze the mechanical properties, the permeability and the freezing properties of SB-2 materials which are mainly used with the subbase materials on the rod. For this ends, a series of the physical test, the permeability test and the freezing test were carried out the samples mixed the small aggregate and the big aggregate from which was re-classified the SB-2. From the test results, it was analyzed the characteristics of permeability and the characteristics of freezing of the samples.

• International Journal of Highway Engineering
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• v.15 no.2
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• pp.83-94
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• 2013

PURPOSES : In Korea, most designs of pavement had been mainly performed by considering CBR of granular materials before KPRP(Korea Pavement Research Program) and 86 AASHTO design method were introduced. Since then, the trend of the pavement designs gradually have moved to using mechanical characteristics throughout the resilient modulus based on the test results up to recently. In this study, we should like to research the mechanical characteristics of paving materials containing Recycled aggregates through the cyclic loading triaxial compression tests. METHODS : The kinds of materials were tested; coarse grained subbase materials, refining aggregates base materials and recycled aggregates. RESULTS : The present study aims to figure out the resilient modulus of paving materials containing Recycled aggregates through the cyclic loading triaxial compression tests. CONCLUSIONS : The test results revealed that the engineering properties of the recycled aggregates were more excellent than the those of others.

• International Journal of Highway Engineering
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• v.13 no.4
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• pp.41-50
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• 2011

It is well-known that pavement is easily damaged by several factors including permanent deformation and fatigue crack, causing service life of the pavement to be shorter than expected. It is very important to predict amount of permanent deformation for designing pavement and developing design method of pavement. A new model of permanent deformation of pavement materials based on concept of shear stress ratio has been proposed because the lower pavement materials are highly affected by shear strength of the material. In this study a large repetitive triaxial load test has been adapted for performing test of permanent deformation of crushed subbase materials. The test procedure which includes concept of shear stress ratio has been newly developed. Several important model parameters can be obtained from the test that can be used for making correct permanent deformation model of the material.