• Journal of the Korean Society of Safety
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• v.30 no.4
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• pp.120-127
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• 2015

The aim of the present study is to investigate some characteristics of concrete according to addition of blast furnace slag and alkali-activator dosages. Blast furnace slag was used at 30%, 50% replacement by weight of cement, and liquid sulfur having NaOH additives was chosen as the alkaline activator. In order to evaluate characteristics of blast furnace slag concrete with sulfur alkali activators, compressive strength test, total porosity, chloride ions diffusion coefficient test were performed. The early-compressive strength characteristics of blast furnace slag concrete using a sulufr-alkali activators was compared with those of reference concrete and added 30, 50% blast furnace slag concrete. Also, Blast furnace slag concrete using sulfur-alkali activators enhanced the total porosity, chloride ions diffusion coefficient than two standard concrete. Alkali-activated blast furnace slag concrete was related to total porosity, compressive strength and chloride ions diffusion coefficient each others. As a result, it should be noted that the sulfur-alkali activators can not only solve the demerit of blast furnace slag concrete but also offer the chloride resistance of blast furnace slag concrete using sulfur alkali activators to normal concrete.

• Journal of the Korea Institute of Building Construction
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• v.16 no.4
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• pp.321-329
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• 2016

The use of ternary blended cement consisting of Portland cement, granulated blast-furnace slag (GGBFS) and fly ash has been on the rise to improve marine concrete structure's resistance to chloride attack. Therefore, this study attempted to investigate changes in chloride attack resistibility of concrete through NT Build 492-based chloride migration experiments and test of concrete's ability to resist chloride ion penetration under ASTM C 1202(KS F 2271) when 1.5-2.0% of alkali-sulfate activator (modified alkali sulfate type) was added to the ternary blended cement mixtures (40% ordinary Portland cement + 40% GGBFS + 20% fly ash). Then, the results found the followings: Even though the slump for the plain concrete slightly declined depending on the use of the alkali-sulfate activator, compressive strength from day 2 to day 7 improved by 17-42%. In addition, the coefficient from non-steady-state migration experiments for the plain concrete measured at day 28 decreased by 36-56% depending on the use of alkali-sulfate. Furthermore, total charge passed according to the test for electrical indication of concrete's ability to resist chloride ion penetration decreased by 33-62% at day 7 and by 31-48% at day 28. As confirmed in previous studies, reactivity in the GGBFS and fly ash improved because of alkali activation. As a result, concrete strength increased due to reduced total porosity.

• Journal of the Korean Ceramic Society
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• v.26 no.5
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• pp.601-608
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• 1989

Electrical properties of ZrF4-based heavy metla fluoride glasses were measured by the ac complex impedance method. The effects of alkali and chloride ions addition into fluoro zirconate glasses on the electrical conductivity were examined. The electrical conductivities of fluoride glasses show Arrhenian behavior in the temperature range of the experiment and were decreased by the addition of sodium fluoride up to 15mol%. Mixed alkali substitution resulted in conductivity minimum at intermediate composition which is commonly observed as mixed alkali effect' in alkali oxide glasses. Chloride ion substituted for fluoride ion was found to lower the conductivity.

• International Journal of Concrete Structures and Materials
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• v.8 no.4
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• pp.289-299
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• 2014

Alkali-activated slag concretes are being extensively researched because of its potential sustainability-related benefits. For such concretes to be implemented in large scale concrete applications such as infrastructural and building elements, it is essential to understand its early and long-term performance characteristics vis-a'-vis conventional ordinary portland cement (OPC) based concretes. This paper presents a comprehensive study of the property and performance features including early-age isothermal calorimetric response, compressive strength development with time, microstructural features such as the pore volume and representative pore size, and accelerated chloride transport resistance of OPC and alkali-activated binder systems. Slag mixtures activated using sodium silicate solution ($SiO_2$-to-$Na_2O$ ratio or $M_s$ of 1-2) to provide a total alkalinity of 0.05 ($Na_2O$-to-binder ratio) are compared with OPC mixtures with and without partial cement replacement with Class F fly ash (20 % by mass) or silica fume (6 % by mass). Major similarities are noted between these binder systems for: (1) calorimetric response with respect to the presence of features even though the locations and peaks vary based on $M_s$, (2) compressive strength and its development, (3) total porosity and pore size, and (4) rapid chloride permeability and non-steady state migration coefficients. Moreover, electrical impedance based circuit models are used to bring out the microstructural features (resistance of the connected pores, and capacitances of the solid phase and pore-solid interface) that are similar in conventional OPC and alkali-activated slag concretes. This study thus demonstrates that performance-equivalent alkali-activated slag systems that are more sustainable from energy and environmental standpoints can be proportioned.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.1
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• pp.15-21
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• 2023

To prepare zinc oxide powder, three types of sodium-based alkali precipitants such as NaOH, Na₂CO₃, NaOH/NaHCO₃ were compared to the differences in the manufacturing process of zinc oxide powder from zinc precipitate products like intermediates with the consideration of thermodynamic reaction. The prepared zinc precipitate products by the reaction with the sodium-based alkali precipitant were confirmed to respectively hydroxy zinc chloride (Zn₅(OH)₈Cl₂·H₂O) and zinc carbonate hydroxide (Zn₅(OH)₆(CO₃)₂·H₂O) from XRD analysis. Zinc oxide particles were compared in heat treatment at 800℃ according to sodium-based alkali precipitants. The mixed NaOH and NaHCO₃ of alkali precipitant reaction was contributed to synthesize the more uniform zinc oxide particles.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.5
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• pp.75-84
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• 2016

This paper presents an investigation of the mechanical properties on non-sintered cement pastes immersed in sea waters at three different temperatures. The non-sintered cement pastes were synthesized using blended binder(Class F fly ash; FA and ground granulated blast furnace slag; GGBFS) and alkali activator(sodium hydroxide and sodium silicate). Binders were prepared by mixing the FA and GGBFS in different blend weight ratios of 6:4, 7:3 and 8:2. The alkali activators were used 5wt% of blended binder, respectively. Calcium carbonate was used as an chemical additive. The compressive strength, bulk density and absorption of alkali-activated FA-GGBFS blends pastes were measured at 3 and 28 days after immersed in sea waters at three different temperatures($5^{\circ}C$, $15^{\circ}C$ and $25^{\circ}C$). The XRD and SEM tests of the pastes were conducted at 28 days. Water-soluble chloride(free chloride) and acid-soluble chloride(total chloride) contents in the pastes were also measured after 28 days immersion in sea water. The experimental results showed that increasing the content of FA in alkali-activated FA-GGBFS blends pastes immersed in sea water increases the absorption, water-soluble chloride content and acid-soluble chloride content, and reduces the compressive strength and bulk density. And it was found that there was a variation of strength change for the alkali-activated FA-GGBFS blends pastes immersed in sea waters at three different temperatures that depends on the blending ratio of FA and GGBFS.

• Journal of the Korea Institute of Building Construction
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• v.12 no.3
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• pp.315-322
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• 2012

The effect of ground granulated blast-furnace slag(GGBS) and alkali activator compressive strength, resistance of chloride attack and freezing-thawing is assessed to develop high volume slag concrete, the replacement rate of GGBS of which is more than 80 percent. result, as the replacement rate of GGBS increases, the compressive strength development properties of concrete in early and long term age decreased and resistance chloride attack and freezing-thawing is increased. The early strength development property, however, is extremely advanced by addition of the alkali activator, which is also found to improve resistance chloride attack and freezing-thawing.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.1
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• pp.1-7
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• 2019

Recently, studies on alkali activated slag(AAS) binders that do not use cement have been actively conducted. It is known that AAS concrete is highly resistant to chloride damage based on the test method used for ordinary concrete. However, it is fully not understood whether the test method used for concrete can be applied to AAS mixtures. Therefore, in this study, we verified the consistency of NT Build 492 and ASTM C 1202 test methods by applying various experimental variables. According to the experimental results, the two tests yielded opposite results. Therefore, the chloride durability of AAS mortar can be different depending on the evaluation method.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2007.11a
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• pp.91-94
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• 2007

It is essential every concrete structure should continue to perform its intended functions, that is maintain its required strength and durability, during the service life. However, deterioration occurs more progressively from the outside of concrete exposed to severe conditions. Deterioration in the concrete structure is due to carbonation and chloride ion attack. Therefore, concrete structure is needed to surface protection for increase durability using impregnant. Impregnant classify into two large groups in polymeric and silicate materials. Silicate impregnant is included silane and alkali silicate(sodium and lithium silicate). Thus, this study is concerned with carbonation and chloride ion resistance of self cleaning hydrophilic impregnant of concrete structure using lithium and potassium silicate. From the experimental test result, lithium and potassium silicate have a good properties as a carbonation and chloride ion resistance. Lithium and potassium silicate make good use of hydrophilic impregnant.

• Journal of the Korean Applied Science and Technology
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• v.31 no.2
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• pp.176-182
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• 2014

Using alkali treatment solution, neutrality treatment solution and acid treatment solution, the surface corrosion layer of copper plates and bronze plates that have been artificially corroded using HCl, $H_2SO_4$ and $HNO_3$ solutions were removed. In the case of alkali treatment solution, only air oxidation in the form of black tenorite and white cuproous chloride remained without being removed. In the case of using a neutrality treatment solution, a anhydrous type layer of reddish brown cupric chloride remained without being removed, together with this black and white corrosion substance. In the case of using an acid treatment solution, this red corrosion substance also remained, but all of the oxide was removed on the surface of the specimen that was treated by alternatively using alkali treatment solution and acid treatment solution. In the case of this treatment solution with the order of alkali-acid, oxidation no longer proceeded only through the distilled water cleaning process after treatment, thereby showing that oxidation from the cleaning solution no longer proceeded.