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Lee M.-J.,Hanwha Engineering and Construction | Hong S.-J.,Hanwha Engineering and Construction | Choi Y.-M.,Hanwha Engineering and Construction | Lee W.,Hanwha Engineering and Construction | Lee W.,Korea University
Engineering Geology | Year: 2010

A series of penetration tests (CPTs and DMTs) and 1-dimensional compression tests are performed on artificially cemented sands to investigate the cementation effect on the deformation characteristics of sand. The constrained modulus (M) is observed to be more sensitive to the cementation than the measurements by CPT and DMT because the cementation effect is not fully reflected in the CPT and DMT results due to the damage of cementation induced during the penetration. As the cementation causes similar effects on the horizontal stress index (KD) and cone resistance (qc), the KD-qc/sigma;v' relation is observed to be similar for both uncemented and cemented sands, regardless of the cementation degree. It is also shown that the dilatometer modulus (ED) of cemented sand is larger than that of uncemented sand at the same qc and the difference increases with the cementation degree. The M/qc and M/ED of cemented sand are significantly larger than those of uncemented sand. The M/qc and M/ED of cemented sand decrease with increasing qc, while those of uncemented sand are almost constant. It is also found that the M/ED-qc/pa relationship of cemented sand is independent of the cementation degree. © 2010 Elsevier B.V.


Kang S.-T.,Daegu University | Kim J.-S.,Hanwha Engineering and Construction | Lee Y.,Daejeon University | Park Y.-D.,Daegu Haany University | Kim J.-K.,Korea Advanced Institute of Science and Technology
KSCE Journal of Civil Engineering | Year: 2012

A series of experiments and numerical analyses have been carried out to derive a model of the moisture diffusion coefficient in concrete structures. The moisture diffusion coefficient generally depends on the relative humidity and temperature as well as the age of concrete, because microstructures of concrete develop with aging, especially in the early stage of aging. Therefore, the modified model of the moisture diffusion coefficient proposed here takes these three parameters into consideration. Experiments on moisture diffusion were performed to investigate the variation of the moisture diffusion coefficient with age and temperature under three temperature conditions (20, 50, and 80°C). Based on the experimental results, a new model of the moisture diffusion coefficient considering the aging and temperature was developed by a numerical inverse analysis. As it considers porosity, humidity, and temperature, beyond the existing model for hardened concrete, the suggested diffusion coefficient model is applicable to early age concrete. © 2012 Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg.


Lee M.J.,Hanwha Engineering and Construction | Choi Y.M.,Korea University | Chae Y.H.,Korea University | Lee W.,Korea University
Geotechnical and Geophysical Site Characterization 4 - Proceedings of the 4th International Conference on Site Characterization 4, ISC-4 | Year: 2013

In this study, both laboratory and field tests are performed for evaluating the cementation effect on various in-situ tests. A series of calibration chamber test using artificially cemented specimen is conducted for estimate the effect of cementation on CPT, DMT and bender element tests. And the results of SPTs, CPTs and SPS tests on naturally cemented coastal sediment are also analyzed. Calibration chamber tests show that the small strain shear modulus (G max) is more sensitive to the cementation than the measurements by CPT and DMT because the cementation effect is not fully reflected in the CPT and DMT results due to the damage of cementation induced during the penetration. It is also observed that the dilatometer modulus from DMT is more effective to evaluate the cementation effect than the cone resistance from CPT. The calibration chamber and in-situ tests verify that the G max/q c-q c1 and (G max/p a)/N 60-(N 1) 60 relations suggested by Schnaid et al. (2004) are effective to detect the cementation of in-situ sediment. However, the (G max/p a)/N 60-(N 1) 60 relation should be corrected a little for the more exact prediction of cementation level. The observation of in-situ tests on naturally cemented sediment shows the q c/N ratio of Jeju sediments is much higher than that of un-cemented sand on the (q c/p a)/N 60-D 50 relation. It means that SPT is more destructive to cementation bonds than CPT. © 2013 Taylor & Francis Group.


Jung J.-Y.,Kongju National University | Park C.-G.,Kongju National University | Park J.-S.,Hanwha Engineering and Construction
Journal of Applied Polymer Science | Year: 2013

This study investigated the effect of styrene-butadiene latex (latex) content on the pullout behavior of structural polypropylene fibers (SPF) in hybrid fiber-reinforced latex-modified cement-based composite made with a blend of SPF and nonstructural polypropylene fiber. Bond tests were performed in accordance with JCI SF-8. NSPF was incorporated at 9.10 kg/m 3 and SPF at 0.45 kg/m 3. Latex was added at 0-20% of the binder weight. The experimental results demonstrated that latex improved the pullout properties of the load-displacement curve in the debonded zone. Also, the bond strength and interface toughness increased with latex content up to 15% but decreased when the latex content reached 20%. Microstructure analysis showed increased scratching on the SPF surface. Copyright © 2012 Wiley Periodicals, Inc.


Lee M.-J.,Hanwha Engineering and Construction | Choo H.,Georgia Institute of Technology | Kim J.,Korea University | Lee W.,Korea University
Bulletin of Engineering Geology and the Environment | Year: 2011

A series of cone penetration and bender element tests were performed on sands artificially cemented with gypsum in a calibration chamber to investigate the effect of cementation on the cone tip resistance (qc) and small strain shear modulus (Gmax) of sand. It was found that both the qc and Gmax of cemented sand are significantly affected by the degree of cementation while the effects of stress and density are reduced due to the cementation bonds. As the degree of cementation increases, the relationship between the of cemented sand is observed to be similar to that of quartz sand with low compressibility. As the density and stress level affect qc more significantly than Gmax, the Gmax/qc of cemented sand decreases with increasing qc. However, as the cementation causes a larger increase in Gmax than qc, the Gmax/qc ratio of cemented sand increases as the gypsum content increases. It was also observed from the relation that the Gmax/qc ratio of cemented sand locates above the upper bound suggested by previous studies. © 2010 Springer-Verlag.

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