• Journal of the Korea Institute of Building Construction
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• v.7 no.4
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• pp.101-108
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• 2007

Furnace slag powder used currently in Korea needs to add special functions in response to the increase of large-scale projects. In addition, it is advantageous in that it has a lower hydration heat emission rate than ordinary Portland cement and improves properties such as the inhibition of alkali aggregate reaction, watertightness, salt proofness, seawater resistance and chemical resistance. However, furnace slag powder is not self -hardening, and requires activators such as alkali for hydration. Accordingly, if recycled fine aggregate, from which calcium hydroxide is generated, and furnace slag, which requires alkali stimulation, are used together they play mutually complementary roles, so we expect to use the mixture as a resource-recycling construction material. Thus the present study purposed to examine the properties and characteristics of furnace slag powder and recycled aggregate, to manufacture recycled fine aggregate concrete using furnace slag and analyze its performance based on the results of an experiment, to provide materials on concrete using furnace slag as a cement additive and recycled fine aggregate as a substitute of aggregate, and ultimately to provide basic materials on the manufacturing of resource-recycled construction materials using binder and fine aggregate as recycled resources.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2015.07a
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• pp.216-217
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• 2015

This study consist of research on the strength development properties of alkali activated slag(AAS) by differential combination of activators, initial protecting and curing conditions. 3 type of binders cured in the atmosphere, underwater and sealed were estimated compressive strength of 3, 7 and 28 days. Test results showed that strength development properties of binders varied with initial protecting and curing conditions because of ionized anions in pore water.

• Computers and Concrete
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• v.20 no.1
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• pp.77-84
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• 2017

Shirasu, a pyroclastic flow deposit, showed considerable performance as aluminosilicate source in geopolymer, based on past research. However, the polymerization reactivity was somewhat lower compared to the traditional fly ash based geopolymer even though the long-term strength was fairly good. The present study concentrates on the development of higher initial strength performance of Shirasu based geopolymer by utilizing ground granulated blast furnace slag as an admixture. Mortars with various mix proportions were adopted to study the effect of parametric changes on strength development along with the addition of slag in different percentages. A combination of sodium hydroxide and sodium silicate was used as alkaline activators considering parameters like molar ratios of alkali to geopolymer water and silica to alkali molar ratio. The mortars were cured at elevated temperatures under different curing conditions to analyze the effect on strength development. Compressive strength test, mercury intrusion porosimetry and X-ray powder diffraction were carried out to assess the strength performance and microstructure of slag-Shirasu based geopolymer. Based on the experimental study, it was observed that the initial and long-term strength development of Slag-Shirasu geopolymer were improved by the addition of slag.

• Applied Microscopy
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• v.43 no.4
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• pp.155-163
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• 2013

Meta-kaolin (MK) and blast furnace slag (BS) were used as raw materials with NaOH and sodium silicate as alkali activators for making geo-polymers. The compressive strength with respect to the various pre-curing conditions was investigated. In order to improve the recycling rate of BS while still obtaining high compressive strength of the geo-polymers, it was necessary to provide additional CaO to the MK by adding BS. The specimens containing greater amounts of BS can be applied to fields that require high initial compressive strength. Alkali activator(s) are inevitably required to make geo-polymers useful. High temperature pre-curing plays an important role in improving compressive strength in geo-polymers at the early stage of curing. On the other hand, long-term curing produced little to no positive effects and may have even worsened the compressive strength of the geo-polymers because of micro-structural defects through volume expansion by high temperature pre-curing. Therefore, a pre-curing process at a medium range temperature of $50^{\circ}C$ is recommended because a continuous increase in compressive strength during the entire curing period as well as good compressive strength at the early stages can be obtained.

• Journal of the Korean Ceramic Society
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• v.52 no.4
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• pp.253-263
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• 2015

Ordinary Portland cement is a widely favored construction material because of its good strength and durability and its reasonable price; however, spalling behaviour during fire exposure can be a serious risk that can lead to strength degradation or collapse of a building. Geopolymers, which can be synthesized by mixing aluminosilicate source materials such as metakaolin and fly ash, and alkali activators, are resistant to fire. Because the chemical composition of geopolymers controls the properties of the geopolyers, geopolymers with various Si:Al ratios were synthesized and evaluated as fire resistant construction materials. Rejected fly ash generated from a power plant was quantitatively analyzed and mixed with alkali activators to produce geopolymers having Si:Al ratios of 1.5, 2.0, and 3.5. Compressive strength of the geopolymers was measured at 28 days before and after heating at $900^{\circ}C$. Geopolymers having an Si:Al ratio of 1.5 presented the best fire resistance, with a 44% increase of strength from 29 MPa to 41 MPa after heating. This material also showed the least expansion-shrinkage characteristics. Geopolymer mortar developed no spalling and presented more than a 2 h fire resistance rating at $1,050^{\circ}C$ during the fire testing, with a cold side temperature of $74^{\circ}C$. Geopolymers have high potential as a fire resistant construction material in terms of their increased strength after exposure to fire.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.2
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• pp.190-197
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• 2020

This paper evaluates the mechanical properties and durability of cement matrix blended with mineral admixtures and ferronickel slag(FNS) powder which is an industrial b y-product during ferronickel smelting process. The hydration heat, pore structure, compressive strength, length change, rapid chloride penetration test(RCPT), and freezing and thawing resistance of ternary blended cement matrix were investigated and compared with ordinary portland cement matrix. The result showed that the compressive strength of ternary blended cement matrix using ferronickel slag powder and mineral mixture was low in strength compared to the reference concrete, but recovered to a certain extent by using alkali activator. Length change of cement mortar using FNS powder have shown less shrinkage occurs than the reference specimen. In addition, irrespective of using the alkali-activators, all ternary mix are indicative of the 'very low' range for chloride ion penetrability according to the ASTM C 1202, and the freeze-thaw resistance also showed excellent results.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.1
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• pp.58-63
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• 2015

Several researches on cement zero concrete using alkali-activators have been conducted to investigate its fundamental material properties such as slump, strength and durability, however, research on the structural behavior of relevant members involving the elastic modulus, stress-strain relationship is essential for the application of this cement zero concrete to structural members. In this paper the shear behavior of reinforced concrete beams using 50 MPa-alkali activated slag concrete was experimentally evaluated. To achieve such a goal, six reinforced concrete beam specimens were fabricated and their shear behaviors were observed. The maximum difference between test results and analysis results in crack shear stress for beam specimens without stirrups is 31%, while that for beam specimens with stirrup is 15%. Furthermore, it is also found that the shear strength of alkali activated slag concrete is by 22~57% greater than the nominal shear strength calculated by design code, implying that shear design equations would provide conservative results on the safety side.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.650-657
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• 2021

Alkali activators that stimulate mineral compounds are expensive materials, but in order to replace industrial products of high alkali in gredien ts, both product an d econ omic feasibility must be satisfied. In this study, alkali in dustrial waste(LW) from the LCD man ufacturin g process were used for the purpose of alkali active reaction of GGBFS for high stren gth concrete over 50MPa. Concrete mixed with LW had reduced workability, but it had the characteristic of increasing compressive strength. Analysis using ACI 209 Compressive Strength Model Equation was made to compare the changes in strength coefficients according to LW mixing. The durability test of concrete, such as Chloride Penetration Resistance and carbonation resistance, also showed excellent performance. In the Adiabatic temperature rise test results, the concrete mixed with LW had the effect of accelerating the initial hydration heat. However, the final Adiabatic temperature rise was not significantly affected by the mixing of LW.

• International Journal of Highway Engineering
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• v.15 no.3
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• pp.1-8
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• 2013

PURPOSES : This study is to evaluate the feasibility of using the alkali activated cement concrete for application of partial-depth repair in pavement. METHODS : This study analyzes the compressive strength of alkali activated cement mortar based on the changes in the amount/type/composition of binder(portland cement, fly ash, slag) and activator(NaOH, $Na_2SiO_3$, $Na_2CO_3$, $Na_2SO_4$). The mixture design is divided in case I of adding one kind-activator and case II of adding two kind-activators. RESULTS : The results of case I show that $Na_2SO_4$ based mixture has superior the long-term strength when compared to other mixtures, and that $Na_2CO_3$ based mixture has superior the early strength when compared to other mixtures. But the mixtures of case I is difficult to apply in the material for early-opening-to-traffic, because the strength of all mixtures isn't meet the criterion of traffic-opening. The results of case II show that NaOH-$Na_2SiO_3$ based mixtures has superior the early/long-term strength when compared to NaOH-$Na_2SiO_3$ based mixtures. In particular, the NaOH-$Na_2SiO_3$ based some mixtures turned out to pass the reference strength(1-day) of 21MPa as required for traffic-opening. CONCLUSIONS : With these results, it could be concluded that NaOH-$Na_2SiO_3$ based mixtures can be used as the material of pavement repair.

• Resources Recycling
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• v.27 no.1
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• pp.106-117
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• 2018

The present study was carried out to find a suitable drying method for the determination of non-evaporable water in hydraulic inorganic materials. In Part 1 of the paper, the case ordinary Portland cement was discussed and, in this Part 2, the case of alkali active slag (AAS) was investigated. Various drying methods including vacuum and oven drying, and an ignition, were used for the AAS system having different w/b, types and amounts of alkali activators. It was found that a combination of the vacuum and oven drying was a suitable drying method for the AAS case. Although a part of the crystallized water in hydration products was decomposed, but the free and adsorbed water could be completely evaporated and the deviation of the results was small.