• 전산구조공학
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• 제24권1호
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• pp.26-30
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• 2011

• Computers and Concrete
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• 제9권6호
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• pp.427-437
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• 2012

This article presents the effect of replacement fly ash (FA) with diatomite (DE) on the properties of geopolymer mortars. DE was used to partially replace FA at the levels of 0, 60, 80 and 100% by weight of binder. Sodium silicate ($Na_2SiO_3$) and sodium hydroxide (NaOH) solutions were used as the liquid portion in the mixture in order to activate the geopolymerization. The NaOH concentrations of 15M, $Na_2SiO_3$/NaOH ratios of 1.5 by weight, and the alkaline liquid/binder (LB) ratios by weight of 0.40, 0.50, 0.60 and 0.70 were used. The curing at temperature of $75^{\circ}C$ for 24 h was used to accelerate the geopolymerization. The flows of all fresh geopolymer mortars were tested. The compressive strengths and the stress-strain characteristics of the mortar at the age of 7 days, and the unit weights were also tested. The results revealed that the use of DE to replace part of FA as source material in making geopolymer mortars resulted in the increased in the workability, and strain capacity of mortar specimens and in the reductions in the unit weights and compressive strengths. The strain capacity of the mortar increased from 0.0028 to 0.0150 with the increase in the DE replacement levels from 0 to 100%. The mixes with 15M NaOH, $Na_2SiO_3$/NaOH of 1.5, LB ratio of 0.50, and using $75^{\circ}C$ curing temperature showed 7 days compressive strengths 22.0-81.0 MPa which are in the range of normal to high strength mortars.

• Structural Engineering and Mechanics
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• 제86권5호
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• pp.687-704
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• 2023

This study aims to examine the structural response of glass fibre-reinforced polymer (Glass-FRP) reinforced geopolymer electronic waste aggregate concrete (GEWC) compression elements under axial compression for sustainable development. The research includes the fabrication of nine GEWC circular compression elements with different reinforcement ratios and a 3-D nonlinear finite element model using ABAQUS. The study involves a detailed parametric analysis to examine the impact of various parameters on the behavior of GEWC compression elements. The results indicate that reducing the vertical distance of glass-FRP ties improves the ductility of GEWC compression elements, and those with eight longitudinal rebars have higher axial load-carrying capacities. The finite element predictions were in good agreement with the testing results, and the put forwarded empirical model shows higher accuracy than previous models by involving the confinement effect of lateral glass-FRP ties on the axial strength of GEWC compression elements. This research work contributes to minimizing the carbon footprint of cement manufacturing and electronic waste materials for sustainable development.

• Computers and Concrete
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• 제33권6호
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• pp.707-724
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• 2024

This paper proposes a study of cement replacement with rice husk ash (RHA) and eggshell ash (ESA) for enhanced mechanical properties of geopolymer (GP) concrete with and without admixture. The main objective is to investigate the mechanical properties of GP with various replacement levels of Pozzolana Portland cement by RHA and ESA. The GP resistance to durability is examined and impact of ash materials on concrete's durability performance is determined. The environmental benefits of using agricultural waste materials in GP manufacturing minimize cement usage and CO2 emissions. The goal is to assess value of RHA-ESA of building material, paving stones for structures to lessen environmental impact. The novelty lies in use of ESA and RHA as partial replacements for cement and investigation of admixtures to enhance concrete properties, and reduce environmental impact. The research contributes by introducing a novel approach to reducing cement consumption by using ESA and RHA to address environmental concerns. It also explores the potential benefits of admixtures improving concrete performance and reducing environmental pollution. A study is carried with and without impacts of admixture to find compressive strength of GP cubes. The cement has been replaced by RHA and ESA in the range of (2.5%+7.5%, 5%+5%, 7.5%+2.5) by weight of cement for M20 mix. The compressive strength (CS) and split tensile strength (STS) at 7days, 14 days and 28 days is obtained as 21 N/mm2 at 7.5%RHA+2.5%ESA and 2.3 at 7.5%RHA+2.5%ESA, 24 N/mm2 at 7.5%RHA+2.5%ESA and 2.3 at 7.5%RHA+2.5%ESA, 28 N/mm2 at 7.5%RHA+2.5%ESA and 2.8 at 7.5%ESA respectively with normal curing condition.

• Advances in concrete construction
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• 제11권2호
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• pp.127-140
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• 2021

In this study, twenty-five geopolymer (GP) mixes were prepared by varying the alkaline solids to Metakaolin (MK) and sodium silicate to NaOH ratios from 0.1 to 0.5 and 0.2 to 1.0, respectively, thus giving a wide range of molar ratios of silica to alumina, sodium oxide to alumina and water to sodium oxide. The compressive strength of these GP mixes was determined for four curing schemes involving oven curing at 100℃ for 24 h and three ambient curing with the curing ages of 3, 14, and 28 days. The test results revealed that for the manufacture of GP binder for structural applications of strength up to 90 MPa, the molar ratio of silica to alumina should be greater than 2.3, sodium oxide to alumina should be between 0.6 to 1.2, and water to sodium oxide should not exceed 12. The compressive strength of ambient cured GP mortar gets stabilized at 28 days of ambient curing. Experimental findings were also corroborated by GP microstructure analysis. The embodied energy of MK-based GP mortars, especially of high strength, is significantly less than the cement mortar of equivalent strength.

• Advances in materials Research
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• 제4권3호
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• pp.133-144
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• 2015

The aim of this investigation is to prepare geopolymer resin by alkali activation of ceramic waste (AACW) with different sodium hydroxide (NaOH) and liquid sodium silicate (LSS) concentrations. In order to prepare geopolymer cement, AACW was replaced by 10 and 30 % by weight (wt.,) of concrete waste (CoW) as well as 10 and 30 wt., % ground granulated blast-furnace slag (GGBFS). The results showed that, the compressive strength of AACW increases with the increase of activator content up to 15:15 wt., % NaOH: LSS. All AACW hardened specimens activated by 3:3 (MC6), 6:6 (MC12), 12:12 (MC24) and 15:15 wt., % (MC30) NaOH: LSS destroyed when cured in water for 24h. The MC18 mix showed higher resistivity to water curing. The results also showed that, the replacement of AACW containing 9:9 wt., % NaOH: LSS (MC18) by 10 (MCCo10) and 30 (MCCo30) wt., % CoWdecreased the compressive strength at all ages of curing. In contrast, the MCCo10 mix showed the lower chemically combined water content compared to MC18 mix. The MCCo30 mix showed the higher chemically combined water content compared to MC18 and MCCo10 mixes. The compressive strength and chemically combined water of all AACWmixes containing GGBFS (MCS10 and MCS30) were higher than those of AACWwith no GGBFS (MC18). As the amount of GGBFS content increases the chemically combined water increases. The x-ray diffraction (XRD) proved that as the amount of CoWcontent increases, the degree of crystallinity increases. Conversely, the replacement of AACW by GGBFS leads to increase the amorphiticity character. The infrared spectroscopy (FTIR) confirms the higher reactivity of GGBFS compared to CoW as a result of successive hydration products formation, enhancing the compaction of microstructure as observed in scanning electron microscopy (SEM).

• Advances in concrete construction
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• 제13권1호
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• pp.71-81
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• 2022

Aluminosilicate materials as precursors are heterogenous in nature, consisting of inert and partially reactive portion, and have varying proportions depending upon source materials. It is essential to assess the reactivity of precursor prior to synthesize geopolymers. Moreover, reactivity may act as decisive factor for setting molar concentration of NaOH, curing temperature and setting proportion of different precursors. In this experimental work, the reactivities of two precursors, low calcium (fly ash (FA)) and high calcium (ground granulated blast furnace slag (GGBS)), were assessed through the dissolution of aluminosilicate at (i) three molar concentrations (8, 12, and 16 M) of NaOH solution, (ii) 6 to 24 h dissolution time, and (iii) 20-100℃. Based on paratermeters influencing the reactivity, different proportions of ternary binders (two precursors and ordinary cement) were activated by the combined NaOH and Na2SiO3 solutions with two alkaline activators to precursor ratios, to synthesize the geopolymer. Reactivity results revealed that GGBS was 20-30% more reactive than FA at 20℃, at all three molar concentrations, but its reactivity decreased by 32-46% with increasing temperature due to the high calcium content. Setting time of geopolymer paste was reduced by adding GGBS due to its fast reactivity. Both GGBS and cement promoted the formation of all types of gels (i.e., C-S-H, C-A-S-H, and N-A-S-H). As a result, it was found that a specified mixing proportion could be used to improve the compressive strength over 30 MPa at both the ambient and hot curing conditions.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2009년도 추계 학술논문 발표대회
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• pp.107-110
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• 2009

After inquiring into physical characteristics of using fly ash and alkali solution, it was found that higher pH density is favorable to strength development at early age and the higher the age is, the higher the compressive strength gets. Also, it was found that when there is more addition of activator, the compressive strength is higher. I was shown that more than atmospheric curing, steam curing was favorable for development of compressive strength. When the temperature of curing temperature was higher, most of the compressive strengths were higher. Thus, based on this study, it was understood that environmental-friendly chemically combined concrete using fly ash and alkali solution can be utilized without using cement.

• 한국결정성장학회지
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• 제27권6호
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• pp.319-326
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• 2017

본 연구에서는, IGCC(Integrated Gasification Combined Cycle: 석탄가스화 복합발전)에서 배출되는 용융 슬래그로 부터 지오폴리머를 제조하여 알칼리 활성화제의 몰농도, W/S 비(water/ solid ratio), 재령일에 따른 비중과 압축강도 등 물리적 특성을 분석함과 동시에 발포제인 Si 슬러지를 첨가하여 경량화 소재로서의 가능성을 고찰하였다. 특히 경량 지오폴리머의 강도 특성향상을 위하여 복합 활성화제 및 pre-curing 공정을 적용하였다. 단일 활성화제를 사용한 경량 지오폴리머의 압축 강도는 9.5 MPa이었으나, 복합 활성화제로 제조할 경우 2~5배 정도의 압축강도 증진 효과를 나타내었다. 더군다나, pre-curing을 실시한 경량 지오폴리머의 경우, pre-curing하지 않은 시편들에 비해 18~48 % 가량 높은 압축강도 값을 보였다. 본 연구에서 복합 활성화제와 pre-curing 공정의 도입으로 얻어진 경량 지오폴리머의 최고 압축강도는 40 MPa(3일 재령하여 밀도가 $1.83g/cm^3$인 시편)로서 시멘트 콘크리트에 필적하였다. XRD 결정상 분석과 SEM을 이용한 미세구조 분석을 통하여 지오폴리머 표면에서 C-S-H 겔(sodium silicate hydrate gel)의 모상에 꽃봉오리 모양의 zeolite 결정상이 균일하게 분포된 것을 확인할 수 있었다.

• 한국건설순환자원학회논문집
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• 제4권4호
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• pp.418-424
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• 2016

본 연구는 화력발전소에서 배출되는 바텀애시의 재활용에 대한 실험적 연구이다. 바텀애시는 플라이애시 보다 다공성 및 높은 흡수율 등의 특징으로 재활용에 대한 연구가 제한적인 실정이다. 본 논문에서는 바텀애시를 결합재로 사용하기 위해 비표면적을 $4,000cm^2/g$까지 미분쇄하였으며, 바텀애시 기반 지오폴리머 모르타르의 플로우, 압축강도 시험 및 미세구조 분석을 실시하였다. 지오폴리머 모르타르의 플로우 측정 결과 활성화제 몰농도가 증가함에 따라 추가배합수가 증가하여 플로우 값이 향상되었다. 압축강도를 검토한 결과 양생온도와 몰농도가 높을수록 압축강도가 증가하였고, 미세구조 분석을 통하여 지오폴리머 반응으로 생성된 지오폴리머 겔을 확인할 수 있었다. 따라서 활성화제 사용 시 지오폴리머 반응은 온도 상승에 비례하여 촉진되기 때문에 적절한 활성화제 몰농도와 고온양생을 통하여 바텀애시 기반 지오폴리머 콘크리트의 제작이 가능할 것으로 판단된다.