Geopolymer, also known as alkali aluminum silicate, is used as a substitute for Portland cement, and it is also used as a binder because of its good adhesive properties and heat resistance. Since Davidovits developed Geopolymer matrix composites (GMCs) based on the binder properties of geopolymer, they have been utilized as flame exhaust ducts and aircraft fire protection materials. Geopolymer structures are formed through hydrolysis and dehydration reactions, and their physical properties can be influenced by reaction conditions such as concentration, reaction time, and temperature. The aim of this study is to examine the effects of silica size and aging time on the mechanical properties of composites. Commercial water glass and kaolin were used to synthesize geopolymers, and two types of silica powder were added to increase the silicon content. Using carbon fiber mats, a fiber-reinforced composite material was fabricated using the hand lay-up method. Spectroscopy was used to confirm polymerization, aging effects, and heat treatment, and composite materials were used to measure flexural strength. As a result, it was confirmed that the longer time aging and use of nano-sized silica particles were helpful in improving the mechanical properties of the geopolymer matrix composite.

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

Geopolymer is an alumina silicate-based ceramic material that has good heat-resistance and fire-resistance; it can be cured at room temperature, and thus its manufacturing process is simple. Geopolymer can be used as a reinforcement or floor finish for high-speed curing applications. In this manuscript, we investigate a high-speed curing geopolymer achieved by adding calcium to augment the curing rate. Metakaolin is used as the main raw material, and aqueous solutions of KOH and K2SiO3 are used as the activators. As a result of optimizing the high bending strength as a target factor for geopolymers with SiO2 / Al2O3 ratio of 4.1 ~ 4.8, the optimum ranges of the active agent are found to be 0.1 ≤ K2O / SiO2 ≤ 0.4 and 10 ≤ H2O / K2O ≤ 32.5, and the optimum range of the curing accelerator is found to be 0.82 Ca (OH)2 / Al2O3 2.87. The maximum flexural strength is found to be 1.35 MPa at Ca (OH)2 / Al2O3 = 2.82, K2O / SiO2 = 0.3, and H2O / K2O = 11.3. The physical and thermal properties are analyzed to validate the applicability of these materials as industrial insulating parts or repairing·finishing materials in construction.

Geopolymers have many advantages over Portland cement, including energy efficiency, reduced greenhouse gas emissions, high strength at early age and improved thermal resistance. Alkali activated geopolymers made from waste materials such as fly ash or blast furnace slag are particularly advantageous because of their environmental sustainability and low cost. However, their durability and functionality remain subjects for further study. Geopolymer materials can be used in various applications such as fire and heat resistant fiber composites, sealants, concretes, ceramics, etc., depending on the chemical composition of the source materials and the activators. In this study, we investigated the thermal properties and microstructure of fly ash and blast furnace slag based geopolymers in order to develop eco-friendly construction materials with excellent energy efficiency, sound insulation properties and good heat resistance. With different curing times, specimens of various compositions were investigated in terms of compressive strength, X-ray diffraction, thermal property and microstructure. In addition, we investigated changes in X-ray diffraction and microstructure for geopolymers exposed to 1,000 oC heat.

Fly ash is one of the aluminosilicate sources used for the synthesis of geopolymers. The particle size distribution of fly ash and the content of unburned carbon residue are known to affect the compressive strength of geopolymers. In this study, the effects of particle size and unburned carbon content of fly ash on the compressive strength of geopolymers have been studied over a compositional range in geopolymer gels. Unburned carbon was effectively separated in the -46μm fraction using an air classifier and the fixed carbon content declined from 3.04 wt% to 0.06 wt%. The mean particle size (d50) decreased from 22.17μm to 10.79μm. Size separation of fly ash by air classification resulted in reduced particle size and carbon residue content with a collateral increase in reactivity with alkali activators. Geopolymers produced from carbon-free ash, which was separated by air classification, developed up to 50 % higher compressive strength compared to geopolymers synthesized from raw ash. It was presumed that porous carbon particles hinder geopolymerization by trapping vitreous spheres in the pores of carbon particles and allowing them to remain intact in spite of alkaline attack. The microstructure of the geopolymers did not vary considerably with compressive strength, but the highest connectivity of the geopolymer gel network was achieved when the Si/Al ratio of the geopolymer gel was 5.0.

Geopolymer cements and geopolymer resins are newly advanced mineral binders that are used in order to reducethe carbon dioxide generation that accompanies cement production. The effect of additives on the compressive strength ofgeopolymerized class-F fly ash was investigated. Blast furnace slag, calcium hydroxide(Ca(OH)2), and silica fume powders wereadded to fly ash. A geopolymeric reaction was initiated by adding a solution of water glass and sodium hydroxide(NaOH) tothe powder mixtures. The compressive strength of pure fly ash cured at room temperature for 28 days was found to be as lowas 291kgf/cm−2, which was not a suitable value for use in engineering materials. On the contrary, addition of 20wt% and40wt% of blast furnace slag powders to fly ash increased the compressive strength to 458kgf/cm−2 and 750kgf/cm−2,respectively. 5wt% addition of Ca(OH)2 increased the compressive strength up to 640kgf/cm−2; further addition of Ca(OH)2further increased the compressive strength. When 2wt% of silica fume was added, the compressive strength increased to 577kgf/cm−2; the maximum strength was obtained at 6wt% addition of silica fume. It was confirmed that the addition of CaO andSiO2 to the fly ash powders was effective at increasing the compressive strength of geopolymerized fly ash.

When a new bonding agent using coal ash is utilized as a substitute for cement, it has the advantages of offering a reduction in the generation of carbon dioxide and securing the initial mechanical strength such that the agent has attracted strong interest from recycling and eco-friendly construction industries. This study aims to establish the production conditions of new hardening materials using clean bottom ash and an alkali activation process to evaluate the characteristics of newly manufactured hardening materials. The alkali activator for the compression process uses a NaOH solution. This study concentrated on strength development according to the concentration of the NaOH solution, the curing temperature, and the curing time. The highest compressive strength of a compressed body appeared at 61.24MPa after curing at 60˚C for 28 days. This result indicates that a higher curing temperature is required to obtain a higher strength body. Also, the degree of geopolymerization was examined using a scanning electron microscope, revealing a micro-structure consisting of a glass-like matrix and crystalized grains. The microstructures generated from the activation reaction of sodium hydroxide were widely distributed in terms of the factors that exercise an effect on the compressive strength of the geopolymer hardening bodies. The Si/Al ratio of the geopolymer having the maximum strength was about 2.41.

The goal of the present work was to investigate the development of a geopolymeric ceramic material from a mixture of mine residue, coal fly ash, blast furnace slag, and alkali activator solution by the geopolymer technique. The results showed that the higher compressive strength of geopolymeric ceramic material increased with an increase in active filler (blast furnace slag + coal fly ash) contents and with a reduction of mine residue contents. The geopolymeric ceramic had very high early age strength. The compressive strength of the geopolymeric ceramic depended on the added active filler content. The maximum compressive strength of the geopolymeric ceramic containing 20 wt.% mine residue was 141.2 MPa. The compressive strength of geopolymeric ceramic manufactured by adding mine residue was higher than that of portland cement mortar, which is 60 MPa, when cured for 28 days. SEM observation showed the possibility of having amorphous aluminosilicate gel within geopolymeric ceramic. XRD patterns indicate that the geopolymeric ceramic was composed of amorphous aluminosilicate, calcite, quartz, and muscovite. The Korea Standard Leaching Test (KSLT) was used to determine the leaching potential of the geopolymeric ceramic. The amounts of heavy metals were noticeably reduced after the solidification of mine residue with active filler.

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.

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 Na2SiO3 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.

본 연구에서는 지오폴리머 결합재인 고로슬래그를 분쇄할 때 석고의 혼입 여부, 고로슬래그와 플라이애시의 혼합비율과 수축저감제 첨가 여부를 변수로 하여 실험하였다. 실험에서는 슬럼프플로우를 측정하여 작업성을 파악하였으며, 압축강도와 휨강도 및 건조수축을 측정하여 역학적 성능을 파악하였다. 석고를 혼입한 고로슬래그는 혼입하지 않은 고로슬래그에 비해 슬럼프플로우가 커지는 경향을 보였으며, 고로슬래그와 플라이애시의 혼합비율이 5:5인 경우가 혼합비율이 8:2인 경우보다 슬럼프플로우가 커지는 경향을 보여 석고와 플라이애시가지오폴리머의 작업성을 높여주는 것으로 나타났다. 석고를 혼입하지 않은 고로슬래그를 사용한 지오폴리머는 석고를 혼입한 고로슬래그를 사용한 경우보다 압축강도와 휨강도가 모두 크게 나타났으며, 고로슬래그와 플라이애시의 혼합비율이 8:2인 경우가 혼합비율이 5:5인 경우보다 압축강도와 휨강도가 커지는 경향을 보였다. 석고를 혼입하지 않은 고로슬래그를 사용하고 플라이애시의 혼합비율을 높일수록 건조수축은 감소되었으며 수축저감제도 지오폴리머의 건조수축 저감에 효과적임을 알 수 있었다.

In this research work, the effect of seawater in the synthesis of fly ash based geopolymer was investigated. Fly ash as a binder was mixed with alkaline activator. The activator used was a mixture of NaOH solution and liquid sodium silicate. The NaOH solution was prepared by dissolving NaOH pellets in seawater to 10mol/L. In this study, compressive strength testing, X-ray diffraction, mercury intrusion porosimetry, scanning electron microscopy with energy dispersive spectroscopy, and analyses for acid- and water-soluble chloride contents were carried out on hardened geopolymer paste samples.

In this study, it was developed geopolymer concrete of alkali-activated using the mixed fly ash and blast furnace slag. and it was developed the interlocking block using the developed geopolymer concrete. In addition, the bending strength and water absorption rate of the interlocking block was tested by KS standard. The test results were as follows. The water adsorption ratio of the BSF4 specimen was under 10%, and the flexural strength of that was over 5MPa

In this study, it was developed geopolymer concrete of alkali-activated using the mixed fly ash and blast furnace slag. and it was developed the interlocking block using the developed geopolymer concrete. In addition, the bending strength and water absorption rate of the interlocking block was tested by KS standard. The test results were as follows. The water adsorption ratio of the BSF4 specimen was under 10%, and the flexural strength of that was over 5MPa.

Geopolymer has recently emerged as an environmentally sustainable material considered to be an alternative to conventional Portland cement. Current study exhibits and discusses the results of experiment on the alteration in mechanical strength of fly ash-based geopolymer mortar activated by alkaline solution with three different sodium hydroxide solution concentrations (etc 10M, 14M and 18M) after exposure to elevated temperatures ranging from 100oC to 1000oC. Thegeopolymermotarexhibitedits strength increase after exposure at 100oC or 200oC ,followed bythe considerable strength loss in strength between 300oC and 700oC. However, the mortar strength rose slightly after exposure to temperature range from 800oC to 1000oC due to the viscous sintering process.

Recently, geopolymer binder or alkali-activated binder has been enormously studied as an alternative to portland cement. However, studies on heat resistance of geopolymers are still few, whereas studies on resistances against chemical attack and carbonation, and mechanical performance of geopolymer are being investigating. This paper aims to summarize a literature review on heat resistance of gel structure in geopolymers exposed to elevated temperature.

The objective of this study is to investigate the immobilization properties of arsenic in solidification process using geopolymer binder. Metakaolin and fly ash were used as prime materials for geopolymer that was also called as activated metakaolin cement (or Si + Al cement). The immobilization of As in geopolymer was found to be very limited regardless of the oxidation state of As and the mixing ratio of As to the binders. These results may be ascribed to the low Ca contents in prime materials used and the structural property of geopolymer formed. It was generally accepted that As was immobilized into C-S-H (calcium silicate hydrates) via precipitation and sorption, when it was solidified with ordinary portland cement and/or lime. When Ca(II) or Fe(III) was used as stimulating agents, the As leaching was reduced by15 ~ 25% than that of control experiment. These limited improvements of As immobilization might be resulted from the extremely high pH in geopolymer reaction.

비소는 광산, 제련소와 같은 산업 활동과 농작물에 사용된 살충제 등 인간 활동으로 발생하는 오염물이다. 비소는 토양 세척, 토양 세정과 흡착-탈착, 용해-침전, 고형화/안정화 등으로 처리하고 있다. 그중 고형화/안정화공법은 금속산화물, 점토, 석회 등을 사용한 연구가 진행 중이나, 시멘트 계열 바인더가 주로 이용되고 있다. 이에 본 연구에서는 시멘트보다 이산화탄소 배출량이 적고, 빠른 조기강도 발현, 화학적인 안정성, 내구성, 내화성과 같은 역학적 특징을 갖는 지오폴리머를 사용하여 비소의 고형화 특성을 평가하였다. 즉, 비소의 산화 상태, 첨가량, 무기성 바인더의 조성, Fe 및 Ca 첨가 등이 비소의 지오폴리머 고형화에 미치는 영향을 조사하였다. 모든 실험에서 Fly ash와 Metakaolin을 사용하여 무기성 바인더 총량을 1500g으로 하였으며, 무기성 바인더의 조성별 실험을 제외 한 나머지 실험에서는 Fly ash와 Metakaoline은 1:1 비율로 혼합하여 사용하였다. 시편의 크기는 5×5×5 cm³이며, 실험 조건별당 시편은 9개씩 제조하였다. 압축강도는 지오폴리머 혼합 14일 후 측정하였으며, 용출 농도는 폐기물공정시험법의 용출시험방법으로 용출한 뒤, ICP-OES(Varian사)로 측정하였다. 압축강도 측정 결과, As(III)의 경우, 0.1%, 0.5% 1.0%에서 각각 68.5, 64.7, 61.8 MPa, As(V)의 경우 68.9, 75.2, 76.8 MPa로 측정되었다. 비소를 첨가하지 않은 실험의 강도, 68.14MPa 비해서 적거나 최대 약 12%가량 증가한 강도가 측정되었다. 무기성 재료 조성 실험에서는 3가지 조건에서 각각 64.8, 49.1, 37.4 MPa이 측정되었다. Fe과 Ca을 첨가한 실험에서는 평균 42.9 MPa으로 조건별로 강도의 차이가 크지 않았으나, 첨가제를 사용하지 않은 실험의 강도, 68.5MPa에 비하여 약 37% 감소된 압축강도가 측정되었다. ICP-OES 분석 결과 As(III) 실험에서 0.1%, 0.5%, 1.0%에서 용출비소 농도가 각각 81.9, 373.3, 764.9 mg/L, As(V)의 경우 82.0, 380.0, 769.9 mg/L로. As 첨가량의 증가에 따라 일정하게 증가하였다. 무기성 바인더의 조성별(무기성 재료에 대한 fly ash 중량비% : 50%, 34%, 0%)로 81.6, 69.5, 69.2 mg/L로 Fly ash 첨가율이 가장 높은 조건에서 용출비소농도가 높게 측정되었다. Fe과 Ca를 이용한 실험에서는 61.7~69.8 mg/L의 비소가 용출되었고, 첨가제를 넣지 않은 지오폴리머(82.0 mg/L)에 비하여 약 15~25%가 감소한 비소 농도를 보였다. 몰비 Fe/As 3일 때, 용출된 5가 비소의 농도가 69.75mg/L로 가장 높게 측정되었고, 몰비 Ca/As 12일 때 61.74mg/L로 가장 낮게 측정되었다. 첨가하는 Fe, Ca의 양이 많을수록 제거율은 증가되나 그 효과가 미미하므로, 첨가제의 양을 증가시킬수록 효율은 떨어진다.