Compressive Strength Of Geopolymers Research Articles

The Effects of Replacement Metakaolin with Diatomite in Geopolymer Materials

Geopolymers are aluminosilicate inorganic polymers. In this study, the effects of replacement metakaolin with diatomite in geopolymer materials were investigated. The geopolymer materials were prepared by leaching diatomite (from Lampang province) and metakaolin (from Ranong province) with alkaline activator solutions. The fresh slurry was cast into plastic molds with a cubic shape and then cured at room temperatures. Effects of ratios between diatomite and metakaolin were investigated. Furthermore, influences of curing time on the properties of the studied samples were also determined. Many techniques for material characterization such as XRF, XRD, and SEM were employed in this work. The mechanical property of geopolymer compressive strength was tested after curing. It was found that compressive strength of the samples increased with increased amounts of diatomite.

Investigating geopolymer cement performance in presence of water based drilling fluid

Oil well cementing is one of the most important steps in drilling and completion processes and providing a full zonal isolation which is the most important features in the oil cementing. Traditionally, Portland cement is used for oil cementing operations, however, a few years ago, a new cost-effective material came to light called geopolymer. In this research, a fly ash class C based geopolymer was used. This research investigates the effect of drilling fluid contamination with geopolymer cement to understand its impact on geopolymer rheological and mechanical performance. Initially, the optimized geopolymer was prepared and mixed with different drilling fluid ratios, including 0%, 5%, and 10% by weight of cement at atmospheric pressure and ambient temperature (24 °C). Same percentages were added to Portland cement to compare it with the geopolymer. Four tests were conducted to determine the effects of drilling fluids including: rheology, density, fluid-loss, and compressive strength for different curing time (1 day, 3 days, and 7 days). Results showed that drilling fluids enhanced the geopolymer rheological behavior by improving geopolymer viscosity and reducing the fluid loss. Drilling fluids reduced the geopolymer viscosity which facilitates the pumping operation during the cementing. In contrast, mixing the drilling fluid with Portland cement had a negative effect on rheological behavior as well as fluid loss. Mixing the drilling fluid with Portland cement increased the fluid loss significantly. In term of compressive strength, as the amount of drilling fluids increased, the compressive strength of geopolymer was not significantly affected. After 3 days curing time, geopolymer lost about 8.5% of its strength when 5% of drilling fluids weight percent was added. Whereas, Portland cement has lost 38.4% of its strength when 5% of drilling fluids weight percent was added. After 7 days curing time, geopolymer lost about 23% of its strength when 5% of drilling fluid by weight of cement was added. However, Portland cement lost 49% of compressive strength in the same conditions. These obtained results indicates that geopolymer has the ability to withstand the drilling fluids contamination.

Kajian Karakteristik Kimia dan Fisika Abu Layang yang Menjadi Penentu Kekuatan Mekanik Perekat Geopolimer Berbahan Dasar Abu Layang

Conversion of fly ash into geopolymers is one of the right ways to reduce the problem of coal ash waste which is hazardous and poisonous waste while its production continues to increase every year. In this study, fly ash from Pacitan power plant, Semen Gresik, Petrokimia Gresik, and Australia were used as the raw materials for making geopolymers. The geopolymers were made based on previous research. Geopolymer compressive strength that was measured at 7 days after curing was 46.71; 42.6; 42.6; 9.55 MPa, respectively. Analyses of phase composition and crystallinity, morphology and particle size and composition of fly ash constituents showed that the factor that had the strongest influence in this study was the size of fly ash particles. Fly ash with the largest particle size produces geopolymers with the lowest compressive strength. High calcium content produces a short setting time and all geopolymers that have high compressive strength are made from fly ash with a high content of Fe 2 O 3

Immobilization of Chromium from Liquid Waste of Electroplating Home-Industries by Fly Ash Geopolymerization

Immobilization is one of methods that can be used to overcome the problem of water pollution by heavy metals, such as chromium, which is possibly produced in an electroplating home-industry. One method that can be used to immobilize heavy metals is by using the waste water as a reactant in a geopolymerization process. The resulting geopolymer will contain such heavy metals and keep them from being dispersed into the environment. In this research, the immobilization was carried out by geopolymerization of fly ash from PT. IPMOMI (International Power Mitsui Operation and Maintenance) in Probolinggo, Indonesia, which pass through 60 (FA 60), 100 (FA 100), and 200 (FA 200) mesh sieve and using wastewater from electroplating home-industries in Ngingas Village, Sidoarjo-Indonesia, or a solution of Cr(NO3)3.9H2O as one of its reactants. The composition of the geopolymerization follows the results of previous research, i.e using the ratio of Solid to Liquid (S/L) = 3.59, Na2O/SiO2 = 0.67, H2O/Na2O = 3.33 and SiO2/Al2O3 = 6.46. Experimental results show that the compressive strength of geopolymers without heavy metals addition increases when the particle size decreases. Geopolymer made of FA 100 has the highest compressive strength i.e 35.05 MPa. The addition of a chromium-containing wastewater in FA 100 geopolymerization produce a geopolymer with a lower compressive strength i.e 26.42 MPa while the addition of Cr(NO3)3·9H2O solution produce geopolymer with compressive strength of 24.47 MPa. The SEM-EDX photo shows that chrome was evenly dispersed in the geopolymer. Leaching test with TCLP method (Toxicity Characteristic Leaching Procedure) on the geopolymer product showed that no chrome content in the leachate was found. This suggests that chromium is immobilized by geopolymers very well.

The influence of Pb addition on the properties of fly ash-based geopolymers

Preventing or reducing negative effects on the environment from the waste landfilling is the main goal defined by the European Landfill Directive. Generally geopolymers can be considered as sustainable binders for immobilization of hazardous wastes containing different toxic elements.In this paper the influence of addition of high amount of lead on structure, strength, and leaching behavior (the effectiveness of Pb immobilization) of fly ash-based geopolymers depending on the geopolymer curing conditions was investigated. Lead was added during the synthesis of geopolymers in the form of highly soluble salt – lead-nitrate. Structural changes of geopolymers as a result of lead addition/immobilization were assessed by means of XRD, SEM/EDS, and 29Si MAS NMR analysis. Investigated curing conditions significantly influenced structure, strength and leaching behavior of geopolymers. High addition of lead caused a sizeable decrease in compressive strength of geopolymers and promoted formation of aluminum-deficient aluminosilicate gel (depolymerization of aluminosilicate gel), regardless of the curing conditions investigated. According to the EUWAC limitations, 4% of lead was successfully immobilized by fly ash-based geopolymers cured for 28 days in a humid chamber at room temperature.

The effect of Solid/Liquid ratio on setting time, workability and compressive strength of fly ash based geopolymers

Intensive research has been focused on the exploitation of fly ash, which is the by-product of power plants. It is estimated that 9500000 t/y of fly ash are produced in Greece and only 10% of this amount is exploited in cement and concrete technology. An attractive way to manage the fly ash deposits is their use in geopolymer production. The Solid/Liquid (S/L) ratio – like the W/C ratio of cementitious mixes - is a critical parameter of the geopolymer mix design procedure. In this paper, the effect of the S/L ratio on the properties of fresh and hardened fly ash based geopolymers is studied. It is concluded that the S/L ratio does not significantly affect the setting time and the compressive strength of geopolymers. On the contrary, workability of the fresh geopolymer is greatly affected by the S/L ratio. The studied geopolymers showed comparable mechanical and physical properties with the cements that are standardized in the EN 197-1.

Effect of process parameters on the performance of fly ash/GGBS blended geopolymer composites

Alkali activation of fly ash and ground-granulated blast-furnace slag (GGBS) is a sustainable technology that promotes recycling of industrial by-products in the form of geopolymer composites. In this study, geopolymers are prepared with fly ash, GGBS, and desert dune sand (fines). The alkaline activator solution is formulated using sodium silicate and 14 M sodium hydroxide solutions. The effect of mixture proportioning and curing conditions on the workability, setting time, and compressive strength of geopolymers was examined. The investigated process parameters included percentage of fly ash replacement by GGBS, superplasticizer dosage, amount of fines, alkaline activator solution content, and sodium silicate to sodium hydroxide ratio. The final geopolymeric product could be enhanced by employing subsequent continuous and intermittent water curing techniques. Based on the experimental results, analytical models correlating mixture proportions with workability and 28-day compressive strength were developed for geopolymers made with 100% GGBS and equal proportions of fly ash and GGBS.

Comparison of strength and durability characteristics of a geopolymer produced from fly ash, ground glass fiber and glass powder

Strength and durability characteristics of geopolymers produced using three precursors, consisting of fly ash, Ground Glass Fiber (GGF), and glass-powder were studied. Combinations of sodium hydroxide and sodium silicate were used as the activator solutions, and the effect of different sodium and silica content of the activators on the workability and compressive strength of geopolymers was investigated. The parameters used in this study were the mass ratio of Na2O-to-binder (for sodium content), and SiO2-to-Na2O of the activator (for silica content). Geopolymer mixtures that achieved the highest compressive strength from each precursor were assessed for their resistance to alkali-silica reaction and compared against the performance of portland cement mixtures. Test results revealed that GGF and fly ash-based geopolymers performed better than glass-powder-based geopolymer mixtures. The resistance of GGF-based and fly ash-based geopolymers to alkali-silica reaction was superior to that of portland cement mixtures, while glass-powder-based geopolymer showed inferior performance.

Effect of Kaolinite Mass Ratio on Compressive Strength of Kaolinite-Calcite Based Geopolymer

This study focuses on the preparation of geopolymers using various proportions of kaolinite and calcite mixture, and the effects of kaolinite mass ratio to calcite on compressive strength of kaolinite/calcite-based geopolymer. Several geopolymer samples were formed using pure kaolinite, pure calcite, and various mass ratio of kaolinite to calcite to examine properties of the geopolymers. The impact of NaOH concentration on the compressive strength of the geopolymers was also examined. The results of the laboratory analyses indicate that the compressive strength of geopolymers did not increase steadily with increasing concentration of NaOH. The optimum workability of geopolymers was obtained at 10 M NaOH and 30 % kaolinite content in the mixture. Several sensitivity experiments were carried out using the parameters at cure temperatures of 22, 45, 65 and 85 o C. The best compressive strength of 12.68 MPa was obtained on the 28th day of curing process at 85 o C. The structural evolution of the geopolymers prepared was investigated using FTIR spectroscopy. They were also characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM).

Detoxification and solidification of heavy metal of chromium using fly ash-based geopolymer with chemical agents

Geopolymers are new cementitious materials that with 3 dimensional networks, which can effectively solidify/stabilize heavy metals. Utilization of fly ash as precursor to prepare geopolymers, and influences of dosages and chemical valences of chromium reagents on geopolymers, as well as detoxification effectiveness of chemical agents for geopolymers were studied. The results showed that compressive strength of geopolymers could be improved when dosage of Cr(NO3)3 is small. Reinhardbraunsite (Ca5(SiO4)2(OH)2) was generated in geopolymers with Cr(NO3)3 or CrO3 due to ‘ions exchange’. Respectively dosing Cr2O3, Cr and CrO3 could make total pore volume of geopolymers smaller and make geopolymers more compact. Chemical bonding and physical encapsulation both existed in geopolymers. Chemical bonding played main role in geopolymers with Cr(NO3)3, and physical encapsulation played main role in geopolymers with Cr2O3, Cr and CrO3, respectively. Chemical agent DTCR could effectively improve compressive strength and capture Cr3+ of geopolymers, enhancing their abilities of anti-erosion.

Development of Green Geopolymer Using Agricultural and Industrial Waste Materials with High Water Absorbency

Geopolymer is a promising porous material that can be used for evaporative cooling applications. Developing a greener geopolymer using agricultural and industrial wastes is a promising research area. In this study, we utilize rice husk (RH), rice husk ash (RHA), metakaolin (MK), ground granulated blast furnace slag (GGBS), and palm oil fuel ash (POFA) to prepare geopolymer pastes, with alkali liquid as an activator. Many geopolymer samples have been prepared as per the Design of Experimental software (DOE), and its corresponding response surface mode and central composite design and later they were characterized. The samples were cured in an oven for 2 h at 80 °C, and thereafter stored at room temperature (~25–30 °C) prior to being tested for its water absorption and compressive strength. The effect of the different composition of precursors on water absorption, density, porosity, and the compressive strength of the prepared geopolymers have been investigated. The results showed that the compressive strength of geopolymers is directly proportional to the ratio of the alkali liquid. Post-optimization, the best geopolymer paste mixture was confirmed to contain 10% of RH, 15% RHA, 35% MK, 10% POFA and 30% of GGBS, with 72% desirability for maximum water absorption (~38%) and compressive strength (4.9 MPa). The results confirmed its applicability for evaporative cooling.

Effect of Variability of Fly Ash Obtained from the Same Source on the Characteristics of Geopolymer

Geopolymer properties is notably influenced by the quality of fly ash used as the precursor material. Fly ash obtained from the same source may have varying physical and chemical characteristics. The characteristics are influenced by, among other, the method and temperature of burning, the degree of grinding and the quarry sources of the coal. In this study, high calcium fly ash from a single power plant was investigated, to analyze the effect of its variability on the characteristics of geopolymer mortar. Fly ash samples were collected at ten different sampling periods. Three mixture compositions, with different sodium silicate solution to sodium hydroxide ratios, were prepared to produce geopolymer mortars. From the results, it was found that there are broad variation of fly ash chemical properties, however only small variation on the fineness and LOI was discovered. The setting time and compressive strength of geopolymer are influenced by the fly ash particle size, pH value and chemical content. Higher level of calcium oxide content increases the compressive strength, while finer particle size could have effect on the later age increase of the compressive strength. Faster setting time is also correlated with the higher pH value of the fly ash, with the tendency of flash setting occurrence for geopolymer using fly ash of high pH level.

Immobilization of hexavalent chromium by fly ash-based geopolymers

Abstract In this paper the immobilization of hexavalent chromium (Cr (VI)) by fly ash (FA)-based geopolymers was investigated, depending on FA characteristics, mechanical activation of FA, geopolymer synthesis conditions and concentration of Cr added. The effectiveness of Cr immobilization was determined via investigation of geopolymer compressive strength and Cr leaching. Structural changes of geopolymers during the Cr immobilization were assessed by means of gas adsorption, XRD, and NMR analysis. FA reactivity was a key factor determining both physical-mechanical and immobilizing properties of geopolymers. Mechanical activation of FA caused an increase of both geopolymer strength and effectiveness of Cr immobilization. The presence of Cr induced physical-mechanical and structural changes in geopolymers. The correlation between concentration of Cr leached and geopolymer physical-mechanical and structural parameters was established.

Fly ash and kaolinite-based geopolymers: processing and assessment of some geotechnical properties

Fly ash is an industrial waste material of the thermal power plants. At present, India produces about 100 million tons of fly ash per annum and most of them are currently dumped in landfills, thus creating a threat to the environment. In recent years, attempts are made to increase the effective utilization of fly ash in the country. This study reveals the morphological, mineralogical, and geotechnical properties of fly ash and fly ash–kaolinite-based geopolymer materials prepared with low-calcium fly ash (ASTM Class F) and kaloinite with activating solution of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) at different curing conditions. Both the fly ash and the fly ash–kaolinite-based geopolymers are prepared in molds, and the unconfined compressive strength (UCS) for each combination is obtained. The UCS of geopolymers at different concentration of alkali, curing temperature, and time is studied. The microstructural and geotechnical characterization of fly ash and geopolymers are obtained using the X-ray diffraction, X-ray fluorescence, and scanning electron microscope (SEM). The low-calcium fly ash and kaolinite-based geopolymers are found to exhibit excellent UCS as compared to that of other geotechnical materials such as clay. It is also observed that fly ash–kaolinite-based geopolymer exhibits more compressive strength than that prepared only with the fly ash. The compressive strength of the geopolymers increases with the concentration of NaOH up to 12 molar beyond which the strength decreases. The compressive strength of geopolymers increases with the improvement of curing condition. Finally, water absorption test is performed to know the water absorption characteristics of the geopolymers.

Metakaolin-, fly ash- and calcium hydroxide-based geopolymers: effects of calcium on performance

Effects of calcium on the performance of geopolymers prepared from metakaolin, class C fly ash (CFA) and calcium hydroxide are studied, including setting times and compressive strength testing. Leaching concentrations of calcium from prepared geopolymers are investigated by inductively coupled plasma atomic emission spectrometry. Relative contents of geopolymeric products and hydration products are studied by acid dissolving testing. The mineral composition, morphology and chemical groups of geopolymeric products and hydration products are analysed by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. Geopolymer setting time is much faster when calcium content increases. Calcium has a positive effect on compressive strength of geopolymers. By acid dissolving testing, the ratio of geopolymer value/ordinary hydration product value in metakaolin-based geopolymer was 4·4 : 1, whereas in CFA-based and CFA + 6% calcium hydroxide-based geopolymers the values were 1 : 1·7 and 1 : 1·5, respectively. Thus, the main product in metakaolin-based geopolymer is geopolymeric products, whereas in CFA-based geopolymer, hydration products also occur. In the alkali-activated condition, CFA-based geopolymer is a composite system with geopolymeric gel and calcium–silicate–hydrate gel co-existing.

Metakaolin-, fly ash- and calcium hydroxide-based geopolymers: effects of calcium on performance

Effects of calcium on the performance of geopolymers prepared from metakaolin, class C fly ash (CFA) and calcium hydroxide are studied, including setting times and compressive strength testing. Leaching concentrations of calcium from prepared geopolymers are investigated by inductively coupled plasma atomic emission spectrometry. Relative contents of geopolymeric products and hydration products are studied by acid dissolving testing. The mineral composition, morphology and chemical groups of geopolymeric products and hydration products are analysed by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. Geopolymer setting time is much faster when calcium content increases. Calcium has a positive effect on compressive strength of geopolymers. By acid dissolving testing, the ratio of geopolymer value/ordinary hydration product value in metakaolin-based geopolymer was 4·4 : 1, whereas in CFA-based and CFA + 6% calcium hydroxide-based geopolymers the values were 1 : 1·7 and 1 : 1·5, respectively. Thus, the main product in metakaolin-based geopolymer is geopolymeric products, whereas in CFA-based geopolymer, hydration products also occur. In the alkali-activated condition, CFA-based geopolymer is a composite system with geopolymeric gel and calcium–silicate–hydrate gel co-existing.

Influence of BFS Content in the Mechanical Properties and Acid Attack Resistance of Fly Ash Based Geopolymers

This paper analyzes the influence of an extra calcium source (added as blast furnace slag) on certain properties of fly ash based geopolymers using sodium silicate as activating solution. Geopolymers were manufactured with different fly ash/blast furnace slag (FA/BFS) ratios: 100/0, 80/20, 60/40, 40/60, and 20/80. The properties studied in the geopolymers were their compressive strength and acid attack resistance. The addition of BFS improves geopolymer compressive strength at early stages. Compressive strength increases as the proportion of BFS in the mixture increases. However, maximum compressive strength was found for a determined BFS content value in the geopolymers, so that a clear reduction of this parameter was appreciated when the BFS content increased above this value. The resistance to acid attack improves in the presence of BFS possibly due to the formation of a calcium sulphate precipitate layer that increases the compressive strength and also operates as a protective coating that hinders geopolymer deterioration.

Final Setting Time and Compressive Strength of Fly Ash and GGBS-Based Geopolymer Paste and Mortar

Geopolymer binders are attracting the attention of researchers as substitution to cement binder in conventional concrete. In manufacturing 1 ton of cement, 1 ton of CO2 is released into the atmosphere. Thus, replacement of cement by geopolymer material in construction industry reduces pollution by two ways: reduction in carbon dioxide emission into atmosphere by reducing the consumption of cement and utilization of fly ash, which is another waste product piling in huge quantities in thermal power plants. To examine the use of geopolymer as a replacement to cement, it is essential to investigate normal consistency, final setting time and compressive strength of geopolymer which are routine tests generally conducted for cement. The procedure adopted for determining the normal consistency, final setting time and compressive strength of geopolymer is same as the procedure adopted for cement. In these tests, cement is replaced by geopolymer material and water is replaced by alkaline activator solution. The parameters considered in this investigation are geopolymer source material (fly ash and GGBS) and alkaline activator consisting of sodium meta silicate and sodium hydroxide of different molarities (8, 12, 16 M). The ratio of sodium meta silicate to sodium hydroxide considered in this study is 2.5. The test results indicated that combination of fly ash and GGBS results in decreased final setting time and increased compressive strength. It was also observed that increase in sodium hydroxide increases compressive strength of geopolymer mortar.

Prediction of compressive strength of geopolymer composites using an artificial neural network

Geopolymers are highly complex materials which involve many variables and make for which modelling the properties is very difficult. There is no systematic approach in mix design for geopolymers. Since the amounts of silica modulus, Na2O content, w/b ratios and curing time have a great influence on the compressive strength, an ANN (artificial neural network) method has been established for predicting compressive strength of ground pumice based Geopolymers and the possibilities of adapting ANN and artificial intelligence system for predicting the compressive strength have been studied. Consequently, a multilayer ANN by using back propagation architecture can be developed for geopolymer compressive strength prediction. In this study, the coefficient of determination (R2) has been used for investigating the proposed model accuracy. As a result, proposed ANN model can predict the compressive strength of geopolymer with R2 = 0.958.

Microscopic Investigation of Geopolymers Made of Fused Slag from Gasification Processes Using Low-Grade Coal and Spent Catalyst Slag

Geopolymers are prospective cement substitutes because their production generates smaller amounts of carbon dioxide and they have sufficient mechanical strength. Geopolymers have attracted increasing interest from construction industries because of their recyclability and eco-friendliness. The compressive strength of geopolymers is known to be associated with their Si/Al ratio. Fused slag from gasification processes using low-grade coal (FSLC) and spent catalyst slag (SCS) were used as raw materials for making geopolymers; the Si/Al ratio was controlled by mixing different ratios of FSLC and SCS. The compressive strength of a geopolymer with a Si/Al ratio of 1.04 had the highest strength (125.6 MPa). Scanning electron microscopy (SEM) analysis was also in good agreement with the compressive strength measurements of compressive strength. There were many small crystallites in the geopolymer matrix. Using transmission electron microscopy (TEM), these crystallites were found to be single crystals, which have a perfect crystal structure. It is speculated that the formation of small crystallites 10-30 nm in size, as well as large single crystals with diameters greater than 80 nm, in the matrix of a geopolymer during the geopolymerization process might increase its compressive strength.