• Steel and Composite Structures
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• v.49 no.4
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• pp.457-471
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• 2023

To make up for the performance weaknesses of recycled aggregate concrete (RAC), expand the application range of RAC, and alleviate the environmental problems caused by excessive exploitation of natural coarse aggregates (NCA), this study proposes a basalt fiber-reinforced recycled aggregate concrete (BFRRAC)-filled square steel tubular columns that combines two modification methods of steel tube and fiber, which may greatly enhance the mechanical properties of RAC. The axial compression performance for BFRRAC-filled square steel tubular columns was reported during this study. Seven specimens with different replacement ratios of recycled coarse aggregate (RCA), length-diameter ratios, along with basalt fiber (BF) contents were designed as well as fabricated for performing axial compression test. For each specimen, the whole failure process as well as mode of specimen were discovered, subsequently the load-axial displacement curve has obtained, after which the mechanical properties was explained. A finite element analysis model for specimens under axial compression was then established. Subsequently, based on this model, the factors affecting axial compression performance for BFRRAC-filled square steel tubes were extended and analyzed, after which the corresponding design suggestion was proposed. The results show that in the columns with length-diameter ratios of 5 and 8, bulging failure was presented, and the RAC was severely crushed at the bulging area of the specimen. The replacement ratio of RCA as well as BF content little affected specimen's peak load (less than 5%). As the content of BF enhanced from 0 kg/m³ to 4 kg/m³, the dissipation factor and ductility coefficients increased by 10.2% and 5.6%, respectively, with a wide range.

• 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.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5551-5557
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• 2012

Sedimentary rocks dug up in construction fields are mostly stockpiled for landfill disposal, leading to an increase in construction costs and construction inefficiency. After screening, some of the sandstone can be used as aggregate; however, most of the shale ends up as industrial waste in practice. In this study, to stabilize the demand and develop resources for alternative aggregates of concrete, the potential use of shale, which is widely distributed in the Daegu-Kyeongbuk region, as a concrete aggregate was evaluated. Red and black shale exported from a Daegu excavation site was selected for use in the experiments and evaluated by comparing with hornfels, which is widely used as a coarse aggregate and is a type of andesite and metamorphosed sedimentary rock. The physical properties of the aggregate were evaluated in accordance with the test methods of KS F 2527 "crushed concrete aggregate," and the compressive strength against the shale aggregate replacement ratio was measured. The compressive strength of the concrete after 28 days was 30.8 MPa when the black shale replaced 100% of the aggregate in the concrete and 31.1 MPa when the red shale replaced 100% of the aggregate in the concrete. Compared with the compressive strength of 37.5 MPa for concrete prepared by using plain aggregate, using shale as a substitute for the aggregate produced an average compressive strength that was 82% of normal concrete.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.7
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• pp.4960-4968
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• 2015

In this study to improve the chloride durability of the shotcrete structure depending on types and contents of mineral admixture chloride resistance was evaluated by NT BUILD 492 of european test standards. It was also evaluated with the mechanical properties such as static strength and chloride penetration resistance. For shotcrete mixed crushed stone aggregate of the maximum size 10mm of coarse aggregates was produced. Based on 28days compression strength the variable mixed with 15% silica fume showed the highest strength in 67.55MPa. As the content of fly ash and blast furnace slag increased, the strength lowered. In the chloride penetration resistance test, OPC showed "high grade" and In the case of admixture, the penetration resistance tended to increase in all variables except the fly ash. In order to evaluate the service life, the accelerated chloride penetration test was conducted by the standards of KCL, ACI, FIB. Test results were obtained with the lowest spreading factor in a variable mixed with silica fume of 15%. At the KCI standards, It was found to have a service life of about 65 years and at the FIB standards, It was found to have a service life of 131 years. Among standards, the service life of KCI standard in all of the variables was evaluated as the lowest.

• Journal of the Korean GEO-environmental Society
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• v.16 no.11
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• pp.39-43
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• 2015

In this study, the infiltration quantity of fine-grained soil into coarse-grained soil or aggregate for methods to accelerate consolidation drainage is checked by laboratory tests under various conditions and those characteristics on infiltration are examined closely. Irrespectively of pressures to fine-grained soil corresponding to stresses in a soil mass or moisture contents of fine-grained soil, fine-grained soil does not infiltrate into standard sand and marine sand, so it is verified that drain-resistance into sand mass of drainage / pile does not occur entirely and its shear strength would increase highly by water compaction. It is known that the infiltration depth of fine-grained soil into aggregate increases according that those size is larger in case of aggregates and it increases according that the pressure or the moisture contents is higher in case of same size aggregate. It is thought that drain-resistance into aggregate mass of drainage / pile would occurs by infiltrated fine-grained soil in advance though the infiltration depth of fine-grained soi of lower moisture content than liquid limit into 13 mm aggregate is low quietly. So gravel drain method or gravel compaction pile method, etc. using aggregate of gravels or crushed stones, etc. larger than sand particle size should be not applied in very soft fine-grained soil mass of higher natural moisture contents than liquid limit, and it is thought that its applying is not nearly efficient also in soft fine-grained soil mass of lower natural moisture contents than liquid limit.

• Journal of the Korean GEO-environmental Society
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• v.17 no.12
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• pp.35-43
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• 2016

With the development of construction technology, constructions of dam and levee (dike) as well as the environmental problems are becoming issues. Recently, many countries have tried to develop and used CSG (Cemented Sand and Gravel), which needs fewer requirements than others in aggregates, constructability and ground condition during the dam construction. Mixing up with small amount of cement, CSG is able to increase the strength and proceed accelerated construction without artificial gradation adjustment of riverbed aggregate and crushed rock on construction site. Thus, CSG can minimize environmental damage resulted from quarries mining and reduce cost of construction. Unlike heat of hydration condition that regular concrete usually met, CSG exposes to repeated dry-wet and freezing and thawing environment. Thus, consider the importance of structure of dam or levee, intensive study on the durability of CSG is needed. In this study, freezing and thawing experiment was carried out to evaluate the durability of CSG. In results, the durability factor of CSG is 30~40 or >40 when the amount of cement is $0.4{\sim}0.6kN/m^3$ or $0.8{\sim}1.0kN/m^3$, respectively. The unconfined compressive strength is reduced to 30~50% or 40~70% when the amount of cement is $0.4{\sim}0.6kN/m^3$ or $0.8{\sim}1.0kN/m^3$, respectively. Taken together, the strength and durability of CSG is reliable when the amount of cement is over $0.8kN/m^3$.