• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.711-714
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• 2005

This paper focused on development of geopolymer for wood wool ceramic board. Geopolymer can substitude ordinary portland cement and its accelerator of wood wool cement board as inorganic polymer. In this study, what we would obtain geopolymer's properties such as initial setting time(KS L 5108), flow(KS L 5102) and compressive strength of 3days aged(KS L 5105), was less than 1 hour, more than $110\%$, more than 40Mpa. Geopolymer have three essential materials called filler, hardener and geopolymer liquor. So, We applied filler by quartz, hardener by blast furnace slag powder, metakaoline and fly ash, geopolymer liquor by NaOH, KOH and sodium silicate solution. As result of this experiment, what we could obtain best fitted geopolymer's properties such as initial setting time, flow and compressive strength of 3days aged, was 45min, $116\%$ and 43.6Mpa. This result can be applicable to commercial wood wool ceramic board.

• Journal of Ceramic Processing Research
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• 제19권5호
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• pp.419-423
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• 2018

A newly conceived geopolymer composite was fabricated by a combination of the geopolymer and polyurethane sponge. The density and porosity of hardened geopolymer composite, corresponded to different pore sizes of polyurethane sponge, exhibited no significant differences from each other. However, the mechanical behavior, the compressive strength and flexural strength, showed slight differences accordingly. Fracture of the geopolymer composite exposed to high compressive load was not observed from all specimens containing polyurethane sponge. The toughness enhancement of the geopolymer composite, due to spontaneous elasticity of polyurethane sponge, crack spread, and crack diffraction, was identified through the stress-strain curve and microstructure of fracture surface. The newly designed geopolymer composite having a 3-dimensional sponge skeleton showed relatively higher flexural strength of 8.0 MPa than other conventional geopolymer composites.

• Advances in concrete construction
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• 제13권1호
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• pp.25-34
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• 2022

The production of geopolymer is considered as a cleaner process due to much lower CO₂ emission than that from the production of Portland cement. This paper presents a study of the potential use of recycled steel fibre (RSF) coming from the recycling process of the old tires in geopolymer mortars. Ground expanded perlite (EP) is used as a source of alumino-silicate and sodium hydroxide (NaOH=5, 10, 15, and 20M) is used as alkaline medium for geopolymer synthesis. RSFs were added to the mortar mixtures in four different volume fractions (0, 0.5, 1.0, and 1.5% of the total volume of mortar). The unit weight, ultrasound pulse velocity, flexural and compressive strength of expanded perlite based geopolymer mortar (EPGM) mixtures were determined. The microstructures of selected EPGMs were examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analyses. The optimum molarity of sodium hydroxide solution was found to be 15M for geopolymer synthesis by EP. The test results revealed that RSFs can be successfully used for fibre-reinforced geopolymer production.

• Advances in concrete construction
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• 제11권1호
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• pp.73-80
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• 2021

Rice Husk Ash (RHA) geopolymer paste activated by sodium aluminate were characterized by X-ray diffractogram (XRD), scanning electron microscope (SEM), energy dispersion X-Ray analysis (EDAX)and fourier transform infrared spectroscopy (FTIR). Five series of RHA geopolymer specimens were prepared by varying the Si/Al ratio as 1.5, 2.0, 2.5, 3.0 and 3.5. The paper focuses on the correlation of microstructure with hardened state parameters like bulk density, apparent porosity, sorptivity, water absorption and compressive strength. XRD analysis peaks indicates quartz, cristobalite and gibbsite for raw RHA and new peaks corresponding to Zeolite A in geopolymer specimens. In general, SEM micrographs show interconnected pores and loosely packed geopolymer matrix except for specimens made with Si/Al of 2.0 which exhibited comparatively better matrix. Incorporation of Al from sodium aluminate were confirmed with the stretching and bending vibration of Si-O-Si and O-Si-O observations from the FTIR analysis of geopolymer specimen. The dense microstructure of SA2.0 correlate into better performance in terms of 28 days maximum compressive strength of 16.96 MPa and minimum for porosity, absorption and sorptivity among the specimens. However, due to the higher water demand to make the paste workable, the value of porosity, absorption and sorptivity were reportedly higher as compared with other geopolymer systems. Correlation regression equations were proposed to validate the interrelation between physical parameters and mechanical strength. RHA geopolymer shows comparatively lower compressive strength as compared to Fly ash geopolymer.

• 한국재료학회지
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• 제20권9호
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• pp.488-493
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• 2010

Geopolymer is a term covering a class of synthetic aluminosilicate materials with potential use in a number of areas, but mainly as a replacement for Portland cement. In this study, geopolymers with fly ash and meta kaolin were prepared using KOH as an alkali activator and water glass. The effect of water glass on the microstructures and the compressive strength of the geopolymer was investigated. As the amount of water glass increased, the dissolved inorganic binder particles in the geopolymers increased due to polymerization, resulting in a dense microstructure. The meta kaolin-based geopolymer showed a better extent of polymerization and densification than that of the fly ash-based geopolymer. XRD data also suggested that polymerization in meta kaolin-based geopolymers should be active resulting in the formation of an amorphous phase with an increasing amount of water glass. The compressive strength of the geopolymer was also dependent on the amount of water glass. The compressive strength of the geopolymers from both fly ash and meta kaolin increased with an increasing amount of water glass because water glass improved the extent of polymerization of the inorganic binder and resulted in a dense microstructure. However, the addition of water glass to the geopolymer did not seem to be effective for the improvement of compressive strength because the meta kaolin-based geopolymer mainly consisted of a clay component. For this reason, the fly ash-based geopolymer showed a higher value of compressive strength than the meta-kaolin geopolymer.

• Computers and Concrete
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• 제20권1호
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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.

• 한국재료학회지
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• 제20권1호
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• pp.1-6
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• 2010

Geopolymer materials are attractive as inorganic binders due to their superior mechanical and eco-friendly properties. In the current study, geopolymer-based cement was prepared using aluminosilicate minerals from fly-ash with KOH as an alkaline-activator and $Na_2SiO_3$ as liquid glass. Then, calcium carbonate powder from a clam shell was mixed with the geopolymer and the mixture was coated on a concrete surface to provide points of attachment for environmental organisms to grow on the geopolymers. We investigated the effect of the shell powder grain size on the microstructure and bonding property of the geopolymers. A homogeneous geopolymer layer coated well on the concrete surface via aluminosilicate bonding, but the adhesiveness of the shell powder on the geopolymer cement was dependent on the grain size of the shell powder. Superior adhesive characteristics were shown in the shell powder of large grain size due to the deep penetration into the geopolymer by their large weight. This kind of coating can be applied to the adhesiveness of eco-materials on the surface of seaside or riverside blocks.

• 한국전산구조공학회논문집
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• 제35권2호
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• pp.101-107
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• 2022

본 논문에서는 지오폴리머의 상변화를 관찰하기 위하여 나노인덴테이션 데이터를 가우시안 믹스쳐 모델로 분석하는 방법을 제시하였다. 지오폴리머는 일반 시멘트 대비 CO₂ 발생량을 줄일 수 있어 시멘트 대체 재료로써 많은 연구가 이루어지고 있다. 기존 연구들로부터 최적의 실리콘/알루미늄 비율을 찾았으나 1.8 초과에서 압축강도 저하의 원인은 아직 불분명하다. 본 연구에서는 실리콘/알루미늄 비율이 재료에 미치는 영향을 조사하고자 나노인덴테이션 실험을 수행하였다. 실험 결과를 가우시안 믹스쳐 모델로 상분석하였고, 실리콘/알루미늄 비율이 증가할수록 재료가 균질거동을 하는 것을 관찰할 수 있었다. 본 연구결과는 강도저하를 규명하는데 직접적인 근거로 활용될 수 있을 것으로 기대된다.

• Advances in concrete construction
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• 제15권4호
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• pp.251-267
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• 2023

In this paper, an experimental investigation is carried out to assess the inherent self-compacting properties of geopolymer mortar and its impact on flexural strength of thin-walled ferro-geopolymer box beam. The inherent self-compacting properties of the optimal mix of normal geopolymer mortar was studied and compared with self-compacting cement mortar. To assess the flexural strength of box beams, a total of 3 box beams of size 1500 mm × 200 mm × 150 mm consisting of one ferro-cement box beam having a wall thickness of 40 mm utilizing self-compacting cement mortar and two ferro-geopolymer box beams with geopolymer mortar by varying the wall thickness between 40 mm and 50 mm were moulded. The ferro-cement box beam was cured in water and ferro-geopolymer box beams were cured in heat chamber at 75℃ - 80℃ for 24 hours. After curing, the specimens are subjected to flexural testing by applying load at one-third points. The result shows that the ultimate load carrying capacity of ferro-geopolymer and ferro-cement box beams are almost equal. In addition, the stiffness of the ferro-geoploymer box beam is reduced by 18.50% when compared to ferro-cement box beam. Simultaneously, the ductility index and energy absorption capacity are increased by 88.24% and 30.15%, respectively. It is also observed that the load carrying capacity and stiffness of ferro-geopolymer box beams decreases when the wall thickness is increased. At the same time, the ductility and energy absorption capacity increased by 17.50% and 8.25%, respectively. Moreover, all of the examined beams displayed a shear failure pattern.

• 한국결정성장학회지
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• 제29권2호
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• pp.61-70
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• 2019

Geopolymer는 시멘트와 비교하여 $CO_2$ 배출량의 감소, 내화성, 낮은 열전도성 등 다양한 장점을 보유하고 있는 eco-friendly 건설재료이다. 그러나 표면에 화염을 가할 경우 geopolymer panel 표면의 열적거동에 대한 연구결과는 많지 않다. 본 연구에서는 내열성 건축자재로서 화염노출시 geopolymer 경화체의 표면특성을 조사하기 위하여 alumina 골재가 사용된 geopolymer 경화체 표면의 화염노출 특성에 대하여 조사하였다. 화염노출시 panel의 외형변형 및 열충격에 의한 크랙은 없었으며, calcite의 잔존량과 aluminosilicate gel의 halo 패턴으로 보아 화염에 의한 탈탄산 및 탈수는 표면에 국한되어 발생했으며, geopolymer 경화체의 내구성은 화염조사 후에도 유지되고 있는 것으로 판단된다. Quartz와 calcite가 감소함에 따라 gehlenite와 calcium silicate가 증가하는 경향을 나타내고 있으며, BFS의 치환량이 많을수록 현저하게 나타난다. 화염노출에 따른 미세구조의 변화는 탈탄산, 결정수의 탈수 등으로 기공의 형성과 발전되는 과정을 거쳐 calcium silicate, gehlenite 등과 같은 새로운 결정상의 형성에 의해 geopolymer panel 표면의 치밀화와 강화기구로 작용하여 내구성이 향상된 것으로 생각된다.