• Title/Summary/Keyword: alkali-activator

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Physicochemical Characteristics and Carbon Dioxide Absorption Capacities of Alkali-activated Blast-furnace Slag Paste (알칼리 활성화된 고로슬래그 페이스트의 물리화학적 특성 및 이산화탄소 흡수능 평가)

  • Ahn, Hae Young;Park, Cheol Woo;Park, Hee Mun;Song, Ji Hyeon
    • International Journal of Highway Engineering
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    • v.17 no.2
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    • pp.99-105
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    • 2015
  • PURPOSES: In this study, alkali-activated blast-furnace slag (AABFS) was investigated to determine its capacity to absorb carbon dioxide and to demonstrate the feasibility of its use as an alternative to ordinary Portland cement (OPC). In addition, this study was performed to evaluate the influence of the alkali-activator concentration on the absorption capacity and physicochemical characteristics. METHODS: To determine the characteristics of the AABFS as a function of the activator concentration, blast-furnace slag was activated by using calcium hydroxide at mass ratios ranging from 6 to 24%. The AABFS pastes were used to evaluate the carbon dioxide absorption capacity and rate, while the OPC paste was tested under the same conditions for comparison. The changes in the surface morphology and chemical composition before and after the carbon dioxide absorption were analyzed by using SEM and XRF. RESULTS: At an activator concentration of 24%, the AABFS absorbed approximately 42g of carbon dioxide per mass of paste. Meanwhile, the amount of carbon dioxide absorbed onto the OPC was minimal at the same activator concentration, indicating that the AABFS actively absorbed carbon dioxide as a result of the carbonation reaction on its surface. However, the carbon dioxide absorption capacity and rate decreased as the activator concentration increased, because a high concentration of the activator promoted a hydration reaction and formed a dense internal structure, which was confirmed by SEM analysis. The results of the XRF analyses showed that the CaO ratio increased after the carbon dioxide absorption. CONCLUSIONS : The experimental results confirmed that the AABFS was capable of absorbing large amounts of carbon dioxide, suggesting that it can be used as a dry absorbent for carbon capture and sequestration and as a feasible alternative to OPC. In the formation of AABFS, the activator concentration affected the hydration reaction and changed the surface and internal structure, resulting in changes to the carbon dioxide absorption capacity and rate. Accordingly, the activator ratio should be carefully selected to enhance not only the carbon capture capacity but also the physicochemical characteristics of the geopolymer.

Evaluation of Flexural Performance of Eco-Friendly Alkali-Activated Slag Fiber Reinforced Concrete Beams Using Sodium Activator (나트륨계 알칼리 활성화제를 사용한 친환경 알카리활성 슬래그 섬유보강콘크리트 보의 휨성능 평가)

  • Ha, Gee-Joo;Yi, Dong-Ryul;Ha, Jae-Hoon
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.19 no.2
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    • pp.170-178
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    • 2015
  • In this study, it was developed eco-friendly alkali-activated slag fiber reinforced concrete using ground granulated blast furnace slag, alkali activator (water glass, sodium hydroxides), and steel fiber. Eight reinforced concrete beam using alkali-activated slag concrete were constructed and tested under monotonic loading. The major variables were mixture ratio of alkali activator, mixed/without of steel fiber. Experimental programs were carried out to improve and evaluate the flexural performance of such test specimens, such as the load-displacement, the failure mode, the maximum load carrying capacity, and ductility capacity. All the specimens were modeled in scale-down size. The reinforced concrete beams using the eco-friendly alkali-activated slag fiber reinforced concrete was failed by the flexure or flexure-shear in general. In addition, the maximum strength increased with the adding the mol of sodium hydroxide, and the specimen reinforced the steel fiber showed the value of maximum strength which is increased by 15.8% through 25.9%. It is thought that eco-friendly alkali-activated slag fiber reinforced concrete can be used with construction material and product to replace normal concrete. If there is applied to structures such as precast concrete member and production of 2nd concrete product, it could be improved the productivity and reduction of construction duration etc.

Effect of alkali-activator and method of pulverization and fineness on the hydration in slag-cement (슬래그의 분쇄방법 및 분말도의 차이와 알칼리 자극제가 슬래그 시멘트의 수화특성에 미치는 영향)

  • Lee, Hee-Gun;Kim, Sang-Kyu;Lee, Seung-Heun;Kim, Seung-Jin;Park, Ju-Won
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.11a
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    • pp.525-528
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    • 2008
  • This study is performed to know influence on the hydration according to alkali activator and method of pulverization and fineness in slag-cement. The compressive strength of mortar were examined when the SG powder of which the specific surface area are 4,000, 6,000, and 8000cm$^2$/g were substituted for 50wt.% of ordinary portland cement. Na$_2$SO$_4$, Ca(OH)$_2$, NaOH were used as alkali activator. respectively, As the results, the compressive strength of mortar increased as following the order, Na$_2$SO$_4$>Ca(OH)$_2$>None>NaOH until 7days. But at 28days, mortar used Ca(OH)$_2$ as alkali activator were the highest strength.

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Properties of Epoxy-Modified Mortars with Alkali Activators and Ground Granulated Blast Furnace Slag (알칼리자극제 및 고로슬래그미분말을 병용한 에폭시수지 혼입 폴리머 시멘트 모르타르의 성질)

  • Kim, Wan-Ki
    • 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.

Characteristics of geopolymer based on recycling resources (재활용 폐자원에 따른 지오폴리머의 특성변화 연구)

  • Kim, Yoo-Teak;Kim, Hyun-Jung;Jang, Chang-Sub
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.22 no.3
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    • pp.152-157
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    • 2012
  • In this study, geopolymer was prepared with reject ash and blast furnace slag using NaOH as an alkali activator and water glass. The aim of this study was to investigate the compressive strength variation according to the contents of NaOH and water glass and replacement ratio of reject ash (RA) and blast furnace slag (BS). The compressive strength measured after 28 days was 38.91 MPa for the geopolymer which consist of 100 % of BS with 1 wt% NaOH and 3 wt% water glass. The major factor for improving compressive strength was the alkali activator proportion and the replacement ratio of RA and BS.

The Effect on the Alkali-Activator Mixing Ratio of Cementless Mortar Using Fly Ash and Blast Furnace Slag (알칼리 활성화제 혼합비가 플라이애시와 고로슬래그를 사용한 무시멘트 모르타르에 미치는 영향)

  • Kang, Hyun-Jin;Ko, Kyung-Taek;Ryu, Gum-Sung;Kang, Su-Tae;Park, Jung-Jun;Lee, Jang-Hwa
    • Proceedings of the Korea Concrete Institute Conference
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    • 2010.05a
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    • pp.315-316
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    • 2010
  • The purpose of this study is to observe the effect of mixture ratio of alkali-activator on workability and compressive strength of alkali-activated mortar that using fly ash and blast furnace slag.

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Research for the production of blast furnace cement mortar using an alkaline activation method (알칼리 활성화 방법에 따른 고로슬래그 경화체 제조 연구)

  • Shin, Jae-Ran;Lee, Ju-Yeol;Park, Byung-Hyun
    • Journal of Korean Society of Water and Wastewater
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    • v.30 no.3
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    • pp.293-297
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    • 2016
  • This study was performed in order to obtain the effect of the compressive strength of the cured product with manufacturing conditions (amounts of fine aggregate and different types of alkali activator). Material which is the basis of the cured product was used for the blast furnace slag, which has a latent hydraulic activity. Consequently, when using sodium hydroxide as the alkali activator, it is possible to obtain a higher compressive strength than using the calcium hydroxide. And also, it can be added a 10% of fine aggregate with blast furnace slag to improve the compressive strength.

Effect of Adding Gypsum in Blast-Furnace-Based Mortar's Fundamental Properties (이수석고가 고로슬래그 미분말 활용 무시멘트 모르타르의 기초물성에 미치는 영향)

  • Lu, Liang Liang;Kim, Jun Ho;Park, Jun Hee;Huang, Jin Guang;Baek, Byung Hoon;Han, Cheon Goo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2013.11a
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    • pp.137-138
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    • 2013
  • Nowadays, research about using recycled aggregate as alkali activator has been investigated. By the mechanism of Alkali activation, blast furnace slag's potential hydraulis property would be activated. Thee application of this technique is considered as fit for low strength concrete, so it's suitable in concrete secondary production such as bricks and blocks. Aside alkali activator, sulfate could also activate blast furnace slag's potential hydranlis property. In this research, gypsum(CaSO4·2H2O)has been added with blast furnace slag. Fundamental experiment such as flow and strength has been tested to evalnate effect of gypsum's activation property.

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Compressive Strength and Shrinkage Strain of Slag-Based Alkali-Activated Mortar with Gypsum (석고가 첨가된 슬래그 기반 알카리활성 모르터의 압축강도 및 건조수축 변형률)

  • Yang, Keun-Hyeok;Sin, Jae-Il
    • Journal of the Korea Institute of Building Construction
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    • v.8 no.1
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    • pp.57-62
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    • 2008
  • Twelve mortars were mixed and tested to explore the effect of gypsum on the compressive strength development and shrinkage strain of alkali-activated mortars. Powder typed sodium silicate and ground granulated blast-furnace slag were employed as alkaline activator and source material, respectively, to produce cementless mortar. The main variables investigated were alkali quality coefficient combining the concentration of activator and main compositions in source material, and the adding amount of gypsum ranged between 1 and 5% with respect to the weight of binder. Initial flow, compressive strength development, modulus of rupture, and shrinkage strain behavior of mortar specimens were measured. In addition, the hydration production of alkali-activated pastes with gypsum was traced using X-ray diffraction and energy-dispersive X-ray analysis combined with scanning electron microscope image. Test results showed that the initial flow of slag-based alkali-activated mortar was little influenced by the adding amount of gypsum. On the other hand, the effect of gypsum on the compressive strength of mortar specimens was dependent on the alkali quality coefficient, indicating that the compressive strength increased with the increase of the adding amount of gypsum until a certain limit, beyond which the strength decreased slowly. Shrinkage strain of mortar tested was little influenced by the adding amount of gypsum because no ettringite as hydration product was generated. However, the adding of gypsum had a beneficial effect on reducing the microcrack in the alkali-activated mortar.

Strength Development of Blended Sodium Alkali-Activated Ground Granulated Blast-Furnace Slag (GGBS) Mortar (혼합된 나트륨계열 활성화제에 의한 고로슬래그 기반 모르타르의 강도발현 특성)

  • Kim, Geon-Woo;Kim, Byeong-Jo;Yang, Keun-Hyeok;Song, Jin-Kyu
    • Journal of the Korea Concrete Institute
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    • v.24 no.2
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    • pp.137-145
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    • 2012
  • Strength model for blasted furnace slag mortar blended with sodium was investigated in this study. The main parameters of AAS (alkali activated slag) mortar were dosage of alkali activator, water to binder ratio (W/B), and aggregate to binder ratio (A/B). For evaluating the property related to the dosage of alkali activator, sodium carbonate ($Na_2CO_3$) of 4~8% was added to 4% dosage of sodium hydroxide (NaOH). W/B and A/B was varied 0.45~0.60 and 2.05~2.85, respectively. An alkali quality coefficient combining the amounts of main compositions of source materials and sodium oxide ($Na_2O$) in sodium hydroxide and sodium carbonate is proposed to assess the compressive strength of alkali activated mortars. Test results clearly showed that the compressive strength development of alkali-activated mortars were significantly dependent on the proposed alkali quality coefficient. Compressive strength development of AAS mortars were also estimated using the formula specified in the previous study, which was calibrated using the collected database. Predictions from the simplified equations showed good agreements with the test results.