• Journal of the Korea Concrete Institute
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• v.15 no.3
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• pp.400-408
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• 2003

Chloride ion inside concrete destroys the so-called passive film surrounding reinforcing bars inside concrete so that the so-called salt attack accelerates corrosion which is the most critical factor for durability as well as structural safety of reinforced concrete structures. Recently, as a solution of the salt attack, the ground granulated blast-furnace slag(GGBFS) have been used as binder or blended cement more extensively. In this paper, characteristics of chloride ion diffusion for the GGBFS concrete, which is known to possess better resistance to damage due to the chloride ion penetration than ordinary portland cement(OPC) concrete possesses, are analyzed and a chloride ion diffusion model for the GGBFS concrete is proposed by modifying an existing diffusion model for the OPC concrete. The proposed model is verified by comparing diffusion analysis results using the model accelerated chloride penetration test results for concrete specimens as well as field test results for an RC bridge pier. Then, an optimal resistance condition to chloride penetration for the GGBFS concrete is obtained according to degrees of fineness and replacement ratios of the GGBFS concrete. The result shows that the GGBFS concrete has better resistance to chloride ion penetration than OPC concrete has and the resistance is more affected by the replacement ratio than the degree of fineness of the GGBFS.

• Journal of the Korea Concrete Institute
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• v.26 no.6
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• pp.723-730
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• 2014

The usage of Ground Granulated Blast Furnance Slag (GGBFS) has been increased recently. Studies on the cement hydration model incorporating GGBFS as well as the properties of cement paste done with GGBFS such as compressive strength, hydration products and hydration heat have been the subjects of many researches. However, studies on the reaction degree of GGBFS that affect the properties of cement paste incorporating GGBFS are lacking globally and specially in Korea. Thus, in this study, the reaction degree of GGBFS using the method if selective dissolution, compressive strength, the amount of chemical bound water and $Ca(OH)_2$ were measured and analysed in accordance with water-binder ratio, replacement ratio of GGBFS, and curing temperature. The results show that the reaction degree of GGBFS, the amount of chemical bound water and $Ca(OH)_2$ in cement paste with GGBFS were higher in conditions where the replacement ratio of GGBFS was low and both water-binder ratio and curing temperature were high. Finally, the reaction degree of GGBFS was achieved at a value between 0.3~0.4.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.5
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• pp.44-49
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• 2016

Among the deteriorating agents, chloride ion is reported to be one of the most harmful ions due to its rapid diffusion and direct effect on steel corrosion. Cold joint which occurs in mass concrete placing is vulnerable to shear resistance and more severe deterioration. The paper presents an quantitative evaluation of chloride diffusion coefficient in OPC(Ordinary Portland Cement) and GGBFS(Ground Granulated Blast Furnace Slag) concrete containing cold joint. GGBFS concrete shows $6.6{\times}10^{-12}m^2/sec$ which is almost 30% level of OPC concrete results and the trend is repeated in the case of cold joint concrete. Compared with OPC concrete, GGBFS concrete is evaluated to have better resistance to chloride penetration, showing 0.30 times of chloride diffusion coefficient in concrete without cold joint 0.39 times with cold joint, respectively.

• Journal of the Korea Institute of Building Construction
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• v.19 no.5
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• pp.421-429
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• 2019

The changes in the resistance to chloride ingress of concrete using a ground granulated blast furnace slag (GGBFS) according to curing conditions were examined. The curing conditions were divided in air-dry curing and under-water curing. Three concrete mixures with the GGBFS replacement ratio of 0%(control), 30%, and 60% were prepared. For tests, evaluations of concrete compressive strength, and chloride ion diffusion coefficient were performed. As the GGBFS replacement ratio increased, the concrete compressive strength of the in air-dry cured specimens decreased compared to under-water cured specimens. When the chloride ion diffusion coefficient was measured, the chloride ion diffusion coefficient decreased as the GGBFS replacement ratio increased. However, the diffusion coefficient of the in air-dry cured specimen was increased up to 111% compared with the under-water cured specimen.

• Advances in concrete construction
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• v.3 no.3
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• pp.223-236
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• 2015

Concrete is the most widely used material of construction. Concrete gained the popularity as a construction material due to the easy availability of its component materials, the easy formability, strength and rigidity upon setting and curing.In construction industry, strength is the primary criterion in selecting a concrete for a particular application. Now a days, the substantial amount of waste materials, containing the properties of the Pozzolana, is being generated from the major industries; and disposal of such industrial wastes generated in abundance is also a serious problem from the environmental and pollution point of view. On this backdrop, efforts are made by the researchers for exploring the possible utilization of such waste materials in making the sustainable construction material. The present paper reports the experimental investigations to study the strength characterization of concrete made from the pozzolanic waste materials. For this purpose, the Pozzolanic materials such as fly ash and ground granulated blast furnace slag were used as a cement replacing materials in conjunction with ordinary Portland cement. Equal amount of these materials were used in eight trial mixes with varying amount of cement. The water cement ratio was also varied. The chemical admixture was also added to improve the workability of concrete. The compressive strengths for 7, 28, 40 and 90 days' were evaluated whereas the flexural and tensile strengths corresponding to 7, 28 and 40 days were evaluated. The study corroborates that the pozzolanic materials used in the present investigation along with the cement can render the sustainable concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.1
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• pp.85-92
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• 2021

The purpose of this study is to investigate the properties of hardener-free epoxy-modified mortars(EMMs) using ground granulated blast furnace slag(GGBFS) and alkali activators. The hardener-free EMMs with a GGBFS content of 20% using 4 types of alkali activators were prepared with various polymer-binder ratios, and tested for strengths, water absorption, carbonation depth, chloride ion and H2SO4 penetration depth. The conclusions obtained from the test results are summarized as follows: The compressive strength of the EMMs with a GGBFS content of 20% attains a maximum at a polymer-binder ratio of 10%. The flexural strength of the hardener-free EMMs using Ca(OH)2 as a alkali activator is improved with increasing polymer-binder ratios. However, the flexural strength of the EMMs using NaCO3, Na2SO4 and Li2CO3 is gradually decreased with increasing polymer-binder ratios. Regardless of the type of alkali activator, the water absorption, chloride ion penetration and carbonation depth are remarkably decreased with increasing polymer-binder ratios due to the epoxy film formed in the EMMs. The H2SO4 penetration depth of the hardener-free EMMs with a GGBFS content of 20% is gradually increased with increasing polymer-binder ratio. In this study, the properties of hardener-free EMMs using Ca(OH)2 as a alkali activator are more excellent than those of other alkali activators.

• Structural Engineering and Mechanics
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• v.55 no.3
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• pp.675-686
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• 2015

The use of ground granulated blast furnace slag (GGBFS) from steel industries waste is showing perspective application in civil engineering as partial substitute to cement. Use of such waste conserves natural resources and minimizes the space required for landfill. The GGBFS used in the present work is of ultra fine size and hence serves as micro filler. In this paper strength and durability characteristics of ultra fine slag based high strength concrete (HSC) (with a characteristic compressive strength of 50 MPa) were studied. Cement was replaced with ultra fine slag in different percentages of 5, 10, and 15% to study the compressive strength, porosity, resistances against sulfate attack, sorptivity and chloride ion penetration. The experiments to study compressive strength were conducted for different ages of concrete such as 7, 28, 56, and 90 days. From the detailed investigations with 16 mix combinations, 10% ultra fine slag give better results in terms of strength and durability characteristics.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.929-934
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• 2001

This study aimed to examine the cause of latent hydraulic property manifestation of ground granulated blast-furnace slag(GGBFS) using different alkali activators in pH, type and quantity. According to the experimental result, the higher pH value accelerated lastly latent hydraulic property and the early stage strength of GCBFS was ranked as activators with the higher pH, in an order of NaOH, $Ca(OH)_{2}$ and $Na_{2}$$Co_{3}$. Also, NaOH had accelerated latent hydraulic property of GGBFS, which had 40~50% of the 3 and 7 days compressive strength of base mortar in case of using 10% of powder-weight. In the case of 30% of GGBFS substitution with annexing 2.5% $Ca(OH)_{2}$, the compressive strength on the 3 and 7 days of the early-age, was increased to 5~10% than that of the same admixture with no activator. With annexing 5.0% $Ca(OH)_{2}$, the strength was increased to 10~20%. Although activator NaOH was effective on the manifestation of latent hydraulic property, it caused cement mortar compressive strength decrease by enlarging pore diameter.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.4
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• pp.113-119
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• 2019

Many researches on alternative materials as construction materials is continuing by recycling industrial byproducts due to shortage of sitereclamation and natural aggregates. In this paper, engineering properties in early-aged OPC (Ordinary Portland Cement) and GGBFS (Ground Granulated Blast Furnace Slag) concrete are evaluated with EOS aggregate replacement. The related experiments were carried out with 0.6 of water to binder ratio, three levels of EOS replacement ratios (0%, 30% and 50%) for fine aggregate, and two levels of cement replacement with GGBFS (0% and 40%). Several tests such as slump air content, and unit mass measurement are performed for fresh concrete, and compressive strength and diffusion coefficient referred to NT BUILD 492 method are measured for hardened concrete. Through the tests, it was evaluated that the compressive strength in concrete with EOS aggregate increased to 3 days and 7 days but slightly decreased at the age of 28 days. In the accelerated chloride penetration test, GGBFS concrete showed reduced diffusion coefficients by 60 - 67% compared with OPC concrete. The lowest chloride diffusion coefficient was evaluated in the 50% replacement with EOS aggregate, which showed an applicability of EOS aggregate to concrete production.

• Journal of the Korea Concrete Institute
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• v.29 no.1
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• pp.101-107
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• 2017

This study aimed to conduct the basic analysis on the fractal characteristics of cementitious materials. The pore structure of cement paste incorporating ground granulated blast furnace slag (GGBFS) was measured using mercury intrusion porosimetry (MIP) and the fractal characteristics were investigated using different models. Because the pore structure of GGBFS-blended cement paste is an irregular system in the various range from nanometer to millimeter, the characteristics of pore region in the different scale may not be adequately described when the fractal dimension was calculated over the whole scale range. While Zhang and Li model enabled analyzing the fraction dimension of pore structure over the three divided scale ranges of micro, small capillary and macro regions, Ji el al. model refined analysis on the fractal characteristics of micro pore region consisting of micro I region corresponding to gel pores and micro II region corresponding to small capillary pores. As the pore size decreased, both models suggested that the pore surface of micro region became more irregular than macro region and the complexity of pores increased.