• 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 Geotechnical Society
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• v.30 no.1
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• pp.93-101
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• 2014

In this study, a blast furnace slag having latent hydraulic property with an alkaline activator for resource recycling was used to solidify sand without using cement. Existing chemical alkaline activators such as $Ca(OH)_2$ and NaOH were used for cementing soils. An alkaliphilic microorganism, which is active at higher than pH 10, is tested for a new alkaline activator. The alkaliphilic microorganism was added into sand with a blast furnace slag and a chemical alkaline activator. This is called the microorganism alkaline activator. Four different ratios of blast furnace slag (4, 8, 12, 16%) and two different chemical alkaline activators ($Ca(OH)_2$ and NaOH) were used for preparing cemented specimens with or without the alkaliphilic microorganism. The specimens were air-cured for 7 days and then tested for the experiment of unconfined compressive strength (UCS). Experimental results showed that as a blast furnace slag increased, the water content and dry density increased. The UCS of a specimen increased from 178 kPa to 2,435 kPa. The UCS of a specimen mixed with $Ca(OH)_2$ was 5-54% greater than that with NaOH. When the microorganism was added into the specimen, the UCS of a specimen with $Ca(OH)_2$ decreased by 11-60% but one with NaOH increased by 19-121%. The C-S-H hydrates were found in the cemented specimens, and their amounts increased as the amount of blast furnace slag increased through SEM analysis.

• Proceedings of the Korea Contents Association Conference
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• 2014.11a
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• pp.139-140
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• 2014

최근 건선산업에서 문제점으로 지적되고 있는 것은 제조과정 중 이산화탄소를 다량 방생시키는 시멘트의 사용이다. 이는 알칼리활성 무기결합재로 대체함으로써 시멘트보다 이산화탄소 배출량을 저감할 수 있지만 고가의 알칼리 자극제를 다량 사용하기 때문에 경제적 측면 및 사용성을 고려하지 않으면 사용할 수 없기 때문에 이에 대한 대체재에 관한 연구가 필요한 실정이다. 이에 본 연구에서는 고로슬래그를 기반으로 하는 알칼리 활성 무기결합재에 알칼리 자극제의 사용량을 저감하기 위해 레드머드를 사용하고, 레드머드에 적합한 알칼리 자극제의 종류와 사용방법에 대하여 연구하고자 하였다.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.555-556
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• 2009

The purpose of this study is to estimate compressive strength of concrete using granulated blast furnace slag. We used Sodium silicate, Potassium silicate, Barium hydroxide as alkali activators and Calcium hydroxide to develop water resistance.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.361-362
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• 2010

Six alkali-activated(AA) concrete mixes were tested to ascertain the effect of unit binder content on the slump and compressive strength of concrete. Test results showed that the compressive strength of AA-concrete increased with the increase of the unit binder content, while the increasing rate was lower that recorded in ordinary portland cement concrete.

• Journal of the Korea Institute of Building Construction
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• v.15 no.5
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• pp.457-464
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• 2015

The alternative material for cement has been attracting attention in construction projects. Especially, the alkali activated slag(hereafter, AAS) concrete is able to use for a structural vertical member because of 40MPa of compressive strength, However, the research about time-dependent deformation such as creep which is important to strength member is insufficient. Therefore, in this study, experiments were performed with respect to time-dependent deformation including the drying shrinkage and creep deformation of AAS concrete. The creep deformed ratio of AAS concrete was more than OPC concrete by approximately 4.3% and the dry shrinkage deformation of AAS concrete was more than OPC concrete by approximately 69%. The large amount of sodium silicate, alkali activator, is added causing temperature crack than promoted drying and drying creep which is confirmed by water ration test and SEM.

• 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.

• Journal of the Korean Geotechnical Society
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• v.29 no.4
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• pp.45-56
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• 2013

In this study, a blast furnace slag with latent hydraulic property is used to cement granular soils without using Portland cement. When the blast furnace slag reacts with an alkaline activator, it can cement soils. The effect of amounts of blast furnace slag and types of alkaline activator on soil strength was investigated for resource recycling. Four different amounts of slag and six different activators (two naturals and four chemicals) were used for preparing specimens. The specimens were air-cured for 3 or 7 days and then tested for unconfined compressive strength (UCS). The UCS of cemented sand with slag increased, in the order of specimens mixed with potassium carbonate, calcium hydroxide, sodium hydroxide and potassium hydroxide. Chemical alkaline activator was better than natural alkaline activator. The maximum UCS of 3-days cured specimens was 3 MPa for 16% of slag with potassium hydroxide, which corresponded to 37% of one with 16% of high-early strength portland cement. As the amount of slag increased, the UCS and dry density of a specimen increased for all alkaline activator cases. As the curing time increased from 3 days to 7 days, the UCS increased up to 97%. C-S-H hydrates were found in the cemented specimens from XRD analyses. Cement hydrates were more generated with increasing amount of slag and they surrounded sand particles, which resulted in higher density.

• Resources Recycling
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• v.27 no.2
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• pp.38-47
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• 2018

Integrated gasification combined cycle (IGCC) is a next generation energy production technology that converts coal into syngas with enhanced power generation efficiency and environmental performance. IGCC produces almost coal gasification slag as the solid by-product. IGCC slag is generated about 140,000 tons for a year although recycling of it is still in the early stages. We evaluated the potential of IGCC slag which is generated from a pilot plant in South Korea as an alkali-activated cement. Samples which were activated with the combined activator of sodium silicate solution and caustic soda had an average compressive strength of 4.5 MPa, showing expansion. Expansion of the alkali-activated slag was presumed to be caused by free CaO in the slag, although it was not detected by the ethylene glycol method. Samples that were activated with the combined activator of sodium aluminate and caustic soda had an average compressive strength of 10 MPa. Hydroxy sodalite and $C_3AH_6$ were found to be the new crystalline phases. IGCC slag can be used as an alkali-activated material, but the strength performance should be improved with proper mix design approach to calculate optimum proportions which can alleviate the expansion issue at the same time.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.6
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• pp.26-33
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• 2012

This paper reported on the effect of blended activator on the physical properties of alkali-activated slag mortar. Five different activators(caustic alkalis) were used: sodium hydroxide(NaOH, A Case), calsium hydroxide($Ca(OH)_2$, B Case), magnesium hydroxide($Mg(OH)_2$, C Case), aluminum hydroxide($Al(OH)_3$, D Case), and potassium hydroxide(KOH, E Case). We blended five caustic alkalis with sodium carbonate($Na_2CO_3$). The dosage of five caustic alkalis was 3M and sodium carbonate was 1M, 2M and 3M. The result of flow and setting time was decrease as the dosage of sodium carbonate increase. But the compressive strength was increase as the dosage of sodium carbonate increase. It was shown that there is a good effect of blended caustic alkalis with sodium carbonate in alkali-activated slag mortar.