• Proceedings of the Korean Institute of Building Construction Conference
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• v.y2004m10
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• pp.55-58
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• 2004

This paper investigated the results of quality of concrete using mixed sand with grading adjustment in order to find out the applicability of fine aggregate with bad grading, According to test results, fluidity of concrete with fine level grading river sand was decreased while with coarse level grading crushed sand increased compared with that with medium level grading crushed sand. Use of mixed sand with grading adjustment(MSG) resulted in an improvement in fluidity. Increase in fineness modulus led to an increase in bleeding, For compressive strength, use of MSG increased compressive strength. For drying shrinkage, use of fine level grading river sand resulted in an increasing drying shrinkage due to the larger presence of fine particles, while use of MSG led to a reduction in drying shrinkage

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.182-183
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• 2021

In this study, This is the result of thermal characteristics analysis to suggest an efficient method of using coal gasification slag(CGS) of byproduct from integrated gasification combined cycle(IGCC). In Specific Heat characteristics, CGS and CS showed similar values. Isothermal Conduction Calorimetry showed that the hydration reaction of cement was retarded when CGS was used. Therefore, it is expected that CGS will be used as an efficient alternative to reducing the hydration heat of mass concrete as a functional aggregate combination.

• Economic and Environmental Geology
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• v.57 no.2
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• pp.161-175
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• 2024

Aggregate typically refers to sand and gravel formed by the transportation of rocks in rivers or artificially crushed, constituting a core resource in the construction industry. Gyeongsangbuk-do, the largest administrative area in South Korea, produces various sources of gravel, including forest, land (excluding other sources), river, and crushed stone. As of 2022, it has extracted approximately 6.96 million cubic meters of aggregate, with permitted production totaling around 4.07 million cubic meters and reported production of about 2.88 million cubic meters. The aggregate demand in Gyeongsangbuk-do is estimated to be 12.39 million cubic meters according to the estimation method in Ready-Mix Concrete. From the supply perspective, about 120 extraction sites are operational, with most municipalities maintaining an appropriate balance between aggregate demand and supply. However, in some areas, there is inbound and outbound transportation of aggregate to neighboring regions. Regions with significant inbound and outbound aggregate transportation in Gyeongsangbuk-do are areas connected to Daegu Metropolitan City and Pohang City along the Gyeongbu rail line, showing a high correlation with population distribution. Gyeongsangbuk-do faces challenges such as population decline, aging rural areas, and insufficient balanced regional development. Analysis using GIS reveals these trends in gravel demand and supply. Currently in this study, Gyeongsangbuk-do meets its demand for aggregate through the supply of various aggregate sources, maintaining stable aggregate procurement. River and terrestrial aggregates may be sustained as short-term supply strategies due to the difficulty of longterm development. Considering the reliance on raw material supply for selective crushing, it suggests the need for raw material management to maintain stability. Gyeongsangbuk-do highlights quarries in the forest as an important resource for sustainable aggregate supply, advocating for the development of large-scale aggregate quarries as a long-term alternative. These research findings are expected to provide valuable insights for formulating strategies for sustainable management and stable utilization of aggregate resources.

• Geomechanics and Engineering
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• v.36 no.1
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• pp.39-50
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• 2024

Bitumen and high-quality subangular aggregates, the two principal materials used for asphalt concrete construction, are finite and expensive materials. The general availability of crumb rubber and naturally occurring aggregates of different shapes, especially flat and elongated shapes, indicates that they are feasible alternative materials for expanding the volume of bitumen and utilizing a wider range of aggregate shapes for the development of asphalt concrete, with an associated environmental benefit. The study investigated the effect of adding up to 15% crumb rubber and aggregates sorted into different groups, i.e., rounded, elongated, flat, and their combinations, on the rheological and mechanical properties and durability of 50/70 of hot-mix asphalt pavement. The addition of crumb rubber decreased ductility and penetration but increased the softening point. For a 5.5% bitumen content, asphalt concrete briquettes consisting of 7% crumb rubber and three types of aggregate shapes, i.e., 100% rounded, a mix of 75% rounded and 25% elongated, and a mix of 75% rounded, 15% elongated and 10% flat, were associated with high Marshall stability and indirect tensile strength as well as low lateral deformation due to their high solidity and moderate angularity ratio. Also, the addition of 7% crumb rubber resulted in a significant improvement in the tensile strength ratio and rebound strain of briquettes consisting of 75% rounded and 25% elongated aggregates and those with 75% rounded, 15% elongated and 10% flat aggregates. In relation to the parameters investigated, the three groups of briquettes met some of the local (South Africa) requirements for the surface course and base course of low traffic volume roads.

• Journal of Korean Society for Quality Management
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• v.17 no.2
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• pp.81-92
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• 1989

A class of standard optimization techniques to estimate the stationary transition probabilities among states is discussed. With the use of aggregate time series data on employed labor in industrial sectors, the alternative restricted estimates including minimum absolute deviation, unweighted, weighted, generalized inverse, minimum chi-square and maximum likelihood are evaluated and compared. Analytic and numerical results are shown favorably with the viewpoint of the validity and predictive potentiality of model.

• Computers and Concrete
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• v.9 no.1
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• pp.35-50
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• 2012

The 2D representative volume element (RVE) for softening quasi-brittle materials like concrete is determined. Two alternative methods are presented to determine a size of RVE in concrete subjected to uniaxial tension by taking into account strain localization. Concrete is described as a heterogeneous three-phase material composed of aggregate, cement matrix and bond. The plane strain FE calculations of strain localization at meso-scale are carried out with an isotropic damage model with non-local softening.

• Korean Management Science Review
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• v.8 no.1
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• pp.3-11
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• 1991

Non-Stationary transition probabilities models which is incorporated into a Markov framework with exogenous variables to account for some of variability are discussed, and extended for alternative procedure. Also as an application of the methodology, the size change of aggregate time-series data on the planted system of agricultural crops is estimated, and evaluated for the precision of time-varying evolution statistically.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.351-354
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• 2000

In recent years, the world development of alternative construction materials is associated with disposal problems of waste materials as a result of industrial activities. Technologies of refining gypsum to several gypsum modifications ($\alpha$ and $\beta$-hemihydrate) which can be used as construction material in a large scale do actually exist or are under development. This paper provides a technical and economic perspective of the waste gypsum treatment. Especially, several applications particularly of $\alpha$-hemihydrate will be presented, e.g. artificial gypsum aggregate and light-weight masonry units.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.99-104
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• 2001

Slag product has the possibility as alternative aggregate and sand under the circumstance of natural resource shortage. Copper slag is the by-product produced in process of copper industry. Recycling the slag in construction industry could give positive effects on the environmental preservation. This study presents that the fundamental properties of high strength concrete which used copper slag as alternative sand. Testing factors are concrete's slump, bleeding, air contents and compressive strength. The results of this study are as follows. (1) Mixing of W/C 30%, substitution rate 25% shows the best slump. As substitution rates are going up, concrete slump is uprising and air contents are downsizing. (2) The bleeding of concrete becomes more serious as substitution rates are going up. (3) The best compressive strength of copper slag concrete is achieved in mixing of W/C 30%, substitution rate 25%.

• Bulletin of the Korean Chemical Society
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• v.25 no.2
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• pp.298-300
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• 2004

An alternative molecular porphyrin-phthalocyanine aggregate was prepared and characterized with UV-visible and X-ray absorption spectroscopies. UV-visible experiments evidence 1-dimensional porphyrin-phthalo-cyanine array formed by mixing $SnTPPCl_2 ({\lambda}_{max}=429,\;{\varepsilon}=2.4{\times10^ 5 /M{\cdot}cm)\;and\;NiPc(OBu)_8({\lambda}_{max}=744 nm,\;{\varepsilon}= 2.0{\times}10^ 5 /M{\cdot}cm)$ in solution. In the UV-visible spectrum of the porphyrin-phthalocyanine array, $(SnPNiPc)_n$, a new Q-band appeared at 844 nm with decrease of the Q-band peak of $NiPc(OBu)_8$ at 744 nm. The red-shift of Q-band evidences an alternative porphyrin-phthalocyanine array formed in solution through metal-halide interaction rather than ${\pi}-{\pi}$ facial interaction, in which nickel of $NiPc(OBu)_8$ coordinates with chloride of $SnTPPCl_2$ through self assembly. Ni K-edge XANES (X-ray absorption near edge structure) spectra also support the axial ligation of nickel to chloride. The square planar structure of $NiPc(OBu)_8$ turns to an octahedral structure in (SnPNiPcSnP) by axial ligation. A higher energy-shift (0.2 eV) of the preedge peak of (SnPNiPcSnP) indicaties partial oxidation of nickel by charge transfer from NiPc$(OBu)_8$ to SnTPPCl$_2$.