Fly Ash Based Geopolymer Binder Research Articles

Optimization of process parameters for the synthesis of class F fly ash-based geopolymer binders

The Taguchi optimization approach was applied in this study to identify the optimal mix ratios for the production of geopolymer paste that uses fly ash as an aluminosilicate precursor. The method allows for probing the combined effect of selected process parameters on the output response with the least number of experiments possible, thereby reducing overall process time, cost, and effort. The compressive and splitting tensile strength values of the geopolymer paste specimens were explored in terms of alkali activator to binder ratio, NaOH concentration, Na2SiO3 to NaOH mass ratio, and standing time. A total of sixteen different proportions of mixtures were prepared, and the mechanical strengths of the specimens were evaluated using a universal testing machine. XRD and SEM analyses were used to examine the microstructures of the fly ash and the proposed optimized geopolymer paste. Results showed that a combination of alkali activator to binder ratio of 0.46, NaOH concentration of 14 M, Na2SiO3 to NaOH mass ratio of 1.5, and standing time of 72 h were found to be the best parameter settings yielding the highest strength of the paste specimens. The maximum compressive and splitting tensile strengths were 24.96 and 4.40 MPa, respectively, at the corresponding optimal values of the parameters. The apparent density of the specimens at these optimal conditions was determined to be 1835 kg/m3. From ANOVA results, it was observed that standing time and NaOH concentration had a significant influence on compressive and splitting tensile strength values, respectively. Based on the confirmation test, a variation of 4.1% and 2.2% in compressive and splitting tensile strengths, respectively, were observed as a result of extraneous variables.

ANALYSIS REGARDING THE MECHANICAL PROPERTIES OF ALKALI-ACTIVATED FLY ASH-BASED GEOPOLYMER CONCRETE CONTAINING SPENT GARNET AS REPLACEMENT FOR SAND AGGREGATES

As research regarding the production and optimization of geopolymer materials is constantly increasing and is fundamentally motivated by the need, identified both in the global ecological context and at national level, new materials can be developed using this type of binder. Sustainable consumption of resources, focuses on the capitalization of existing waste and prevention of generating new ones, therefore adopting the Sustainable Development principles. The increase in the utilization of sand from rivers for various construction purposes, which also disturbs the environment can be considered another damaging factor for the environment. Recycling of garnets and their use as replacement for sand aggregates could provide an ecological solution for the production of the alkali-activated fly ash-based geopolymer binders. The aim of this paper is to present preliminary results regarding the use of spent garnet as replacement for sand aggregates in the production of alkali-activated fly ash-based geopolymer binders using Romanian local raw materials and to study its influence on the mechanical performances of the binder.

Sustainable Fly Ash Based Geopolymer Binders: A Review on Compressive Strength and Microstructure Properties

As a result of global warming, the pursuance of low-carbon, sustainable building materials has been prioritized. The development of geopolymer/cement-less binders can be considered an innovative and green way forward to minimize carbon footprint and tackle industrial waste material utilization. However, the chemical composition and properties of industrial waste-derived geopolymer binders varies considerably based on the chemical compositions of the source materials. This review paper presents a comprehensive understanding of the role of different chemical compositions (namely SiO2, Al2O3, CaO, Fe2O, and MgO) available in contemporary industrial wastes and the development of geopolymer binders. Subsequently, the compressive and microstructure properties of various FA-based geopolymer binders have been discussed to exhibit the feasibility of FA as a reliable source material. Significant findings and research gaps have been considered to aid future research works. Indeed, they provide guidelines for the commercial implementation of FA-based geopolymer binders as a low-carbon alternative to Portland cement.

Effect of Sodium Hydroxide Molarity on Compressive Strength of Porous Concrete Containing Fly Ash-based Geopolymer Binder

Effect of Sodium Hydroxide Molarity on Compressive Strength of Porous Concrete Containing Fly Ash-based Geopolymer Binder

Thermal behavior and post-heating fracture characteristics of polypropylene microfiber-reinforced geopolymer binders

This paper investigated the post-heating behavior of fly ash-based geopolymer binders reinforced with polypropylene (PP) microfibers. Geopolymer binders with different fiber contents including 0%, 0.05%, 0.1%, and 0.2% by fly ash weight were prepared and exposed to elevated temperatures of 200 °C, 400 °C, and 600 °C. The effect of fiber reinforcement on the mechanical strengths of unheated binders, residual fracture characteristics of heat-damaged binders, microstructure deterioration, and thermal properties of geopolymer specimens were investigated. The results revealed that PP microfibers had neglected effect on the compressive strength of the binders, but clearly enhanced their flexural strength. Maximum enhancement of 17% was observed in the flexural strength of binders with 0.05% PP fibers. Using PP microfibers enhanced the residual compressive but not the flexural strength of the heat-damaged binders. The fiber-reinforced specimens had higher residual compressive strength compared to the corresponding fibreless ones when heated up to 500 °C. The modulus of elasticity and the toughness of the binders decreased with heating. Fiber-reinforced specimens showed higher reduction in the toughness but lower reduction in the modulus due to heating compared to the fibreless specimens. Using PP microfibers reduced the thermal conductivity of geopolymer binders. The reduction due to the fiber addition was less pronounced for heated specimens compared to unheated ones.

Effect of Flyash- Rice Husk Ash Blend in the Energy Efficient Geopolymer Tiles Using Industrial Wastes

Infrastructural developments are inevitable for the developing countries and hence the production of sustainable building materials is promoted worldwide. Sustainable development in the vicinity of tiles is bewildered for more than a decade. Production of conventional tiles such as cement concrete tiles, clay tiles and ceramic tiles is energy intensive approach and levies lot of strain over the adjunct ecosystem. On the other hand there are serious problems related to the disposal of flyash, Rice Husk Ash throughout the world. An approach has been taken to synthesis tiles based on these industrial byproducts as the base materials through Geopolymer technology. In this work, Geopolymer mortar after heat curing is applied as tiles. In this work, Flyash is replaced by Rice Husk Ash in various proportions such as 20, 40, 60, 80 and 100 percent. Tests such as workability, flatness, straightness, perpendicularity, water absorption, modulus of rupture and abrasion are conducted and fair results are obtained. This research also portrays the effect of Rise Husk Ash addition over the flyash based Geopolymer binder in the utility as tiles. The findings of this research work encourages the development of energy efficient tiles using industrial wastes. Keywords: Geopolymer, Rice Husk Ash, Tiles

Rheology, Setting Time, and Compressive Strength of Class F Fly Ash–Based Geopolymer Binder Containing Ordinary Portland Cement

AbstractThis paper investigates the incorporation of ordinary portland cement (OPC) to adjust/improve the workability, setting time, and compressive strength of Class F fly ash (FA)–based geopolyme...

Durability of Moroccan fly ash-based geopolymer binder

This study investigates the durability of fly ash-based geopolymer pastes (FA-GP). Thermal behavior was evaluated by heating the FA-GP pastes at 1000 °C for 2 h (FA-GP-1000 °C). Acid resistance was studied by immersing specimens in a 5% sulfuric acid solution for a period of 4 months (FA-GP-H2SO4). Physicochemical, microstructural and mechanical changes after heat and acid exposure were studied using several analysis methods such as Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM) and compressive strength. The results showed that the visual appearance of fly ash-based geopolymer samples was well preserved after high temperature exposure, and kept about 37% of its initial compressive strength value. SEM micrographs of acid exposed samples showed very porous structure with some micro-cracks, inducing a decrease of the residual compressive strength of about 33.33 %.

Utilization of Industrial By-Products/Waste to Manufacture Geopolymer Cement/Concrete

There has been a significant movement in the past decades to develop alternative sustainable building material such as geopolymer cement/concrete to control CO2 emission. Industrial waste contains pozzolanic minerals that fulfil requirements to develop the sustainable material such as alumino-silicate based geopolymer. For example, industrial waste such as red mud, fly ash, GBFS/GGBS (granulated blast furnace slag/ground granulated blast furnace slag), rice husk ash (RHA), and bagasse ash consist of minerals that contribute to the manufacturing of geopolymer cement/concrete. A literature review was carried out to study the different industrial waste/by-products and their chemical composition, which is vital for producing geopolymer cement, and to discuss the mechanical properties of geopolymer cement/concrete manufactured using different industrial waste/by-products. The durability, financial benefits and sustainability aspects of geopolymer cement/concrete have been highlighted. As per the experimental results from the literature, the cited industrial waste has been successfully utilized for the synthesis of dry or wet geopolymers. The review revealed that that the use of fly ash, GBFS/GGBS and RHA in geopolymer concrete resulted high compressive strength (i.e., 50 MPa–70 MPa). For high strength (>70 MPa) achievement, most of the slag and ash-based geopolymer cement/concrete in synergy with nano processed waste have shown good mechanical properties and environmental resistant. The alkali-activated geopolymer slag, red mud and fly ash based geopolymer binders give a better durability performance compared with other industrial waste. Based on the sustainability indicators, most of the geopolymers developed using the industrial waste have a positive impact on the environment, society and economy.

The study of ecological impact of fly ash-based geopolymer binders on soil and aquatic biota

Coal power plants represent the large source of environmental pollution in soils, ground and surface water by leaching out toxic compounds from open landfilled and impounded coal combustion residuals (CCR) such as fly ash. The use of fly ash as a main component in geopolymer binder (GB) systems is one of the effective methods of CCR beneficial utilization. The toxicity assessment as well as leachability of harden geopolymers were tested in aqueous media where oat seeds were used as affected test objects. Bio-resistance of the developed geopolymers was evaluated by the resistance to mold fungi growth. The developed geopolymers demonstrated a very low toxicity and leachability to the biota based on the low effect to germinating ability and growth retardation of the exposed oat seeds. Therefore, the studied fly ash products were proved to be environmentally safe when used in GB systems. The absence of fungi growth observed on the surface of geopolymer samples demonstrates high bio-resistance.

Engineering properties of fibre reinforced lightweight geopolymer concrete using palm oil biowastes

ABSTRACTThis paper reports the findings of an experimental programme to investigate the development of a structural lightweight concrete mixture using geopolymer binder and palm oil biowastes. Several concrete mixes were prepared using fly ash-based geopolymer binder, crushed palm oil clinker as asource for lightweight aggregate (POCA), and oil palm trunk fibre (OPTF)as a natural fibre reinforcement. POCA was added at 25%, 50%, 75%, and 100% as volume percentages from total aggregate. OPTF was added at 1%, 2%, and 3% as volume percentages of the mixture. The produced concrete mixtures were evaluated in terms of fresh and harden properties and structural efficiency. The results revealed that OPTF can be used at full replacement level to produce structural lightweight concrete having a compressive strength of more than 30 MPa. In terms of structural efficiency, the optimum POCA content was found at 75% replacement. The optimum OPTF content was found at 1%. Incorporation of POCA and OPTF at any percentage reduced the durability of the concrete produced against acid attack. Yet, the produced mixtures provided good resistance superior to that of conventional concrete. The use of a geopolymer binder boosted the workability, mechanical properties, and durability of the mixtures produced.

ENGINEERING PROPERTIES OF LIGHTWEIGHT GEOPOLYMER CONCRETE USING PALM OIL CLINKER AGGREGATE

The palm oil industry generates a significant amount of wastes which their managing has been a major environmental concern in producing countries. The utilization of these wastes as an aggregate source for concrete production will help to sanitize the environment and provides a cheaper and renewable aggregates source for construction industries. This paper presents the results of the experimental program conducted on fly-ash based geopolymer concrete containing Palm Oil Clinker Aggregate (POCA). Several geopolymer concrete mixes were prepared in which POC was used as a replacement to both fine and coarse aggregates at different percentages starting from 25% to 100%. Mix proportioning was done in accordance with ACI 211.1-91. Geopolymer concrete specimens were cast, cured at ambient conditions and tested for the slump, density, water absorption and compressive, shear and flexural strengths. Overall, the use of fly ashbased geopolymer binder and POCA can enhance the sustainability aspects in concrete production as well as produce a high strength concrete. A concrete mixture containing 100% POCA can produce a structural lightweight concrete having a compressive strength of more than 30 MPa and a density of 1821 kg/m3. The use of a geopolymer binder promotes the workability and strength of POCA concrete and reduces its water absorbability. Incorporation of POCA up to 75% did not much change the structural efficiency of the produced concrete, while it was reduced by 32% when the POCA fully replaced the natural aggregate. Nevertheless, the benefits in terms of cost, energy, and environmental savings cannot be overlooked.

Feasibility of Utilize Sidoarjo Mud as Replacement Material in Fly Ash Based Geopolymer Binder

Sidoarjo mudflow (SM) is an alternative source material in the construction which was generated from natural disasters of volcano mudflow in Porong, Sidoarjo, East Java, Indonesia. The source material of SM has high Si and Al content that contributed to geopolymer binder. Yet, it was categorized as low Ca content that caused prolong setting time in the geopolymer binder. This study aimed to increase the Ca content by incorporating the source material of SM in FA based geopolymer so that was able to provide short setting time in the field. The results showed that the particle properties of SM material were agglomerate irregular shape and rough surface. The increase of SM replacement caused the reduction of workability in fresh geopolymer mortar. Replacement of 40% SM in FA based geopolymer provided the short setting time less than 2.5 hours. The replacement of 15% SM in FA based geopolymer enhanced the compressive strength of 7.6%. However, the highest compressive strength of 9.4% was obtained by the replacement of 10% SM.

Behaviour of fly ash geopolymer binders under exposure to alkaline media

Alkaline agents are primary binder components of geopolymer systems. In the converse, however, the hardened geopolymer binders can be adversely affected under exposure to strong alkalis. This paper presents an investigation conducted to evaluate the effects of highly alkaline exposure environment on fly ash geopolymer binders. In the study, a combination of sodium silicate and 12 M NaOH solution was used as the alkali activator to prepare a low calcium (Class F) fly ash-based geopolymer binder. Fly ash geopolymer pastes or mortars were cast into 50 mm cubes and 25 × 25 × 285 mm prisms, then immersed in different media consisting of water or 1–3 M NaOH solutions maintained at varied temperatures of 23, 38, and 80 °C. The tests done include compressive strength, expansion, and weight changes. Analytical studies were done using X-ray diffraction, X-ray fluorescence, Fourier transform infrared spectroscopy, scanning electron microscopy. Leaching analysis of storage solutions was also conducted. Results showed that alkali attack occurred when the concentrations of storage solutions exceeded 1 M NaOH. The severity of attack increased with increase in NaOH concentration and in storage temperature. It was found that the alkali attack causes damage to the polymeric structure of the binder, leading to release of Al and Si. A gel-like substance is formed, causing expansion and microcracking. New crystalline zeolite phases comprising phillipsite, zeolite-P and chabazite, also formed under exposure of the fly ash geopolymer binder to elevated alkali concentrations.

Fresh and hardened properties of one-part fly ash-based geopolymer binders cured at room temperature: Effect of slag and alkali activators

Geopolymers are considered to be a sustainable and environmentally friendly replacement for ordinary Portland cement as they lead to a reduction in carbon footprint. The dosage and type of precursors and alkali activators have been known to be important parameters affecting the fresh and hardened properties of geopolymers. This study investigates the effect of slag content as well as type and dosage of alkali activators on one-part fly ash-based geopolymers cured at room temperature. Different ratios of fly ash were replaced with slag as a CaO-rich precursor. Setting time and flowability tests were carried out to evaluate the fresh properties, compressive and flexural strength experiments were conducted to determine the mechanical properties of the geopolymers. The mineralogy and microstructure of the samples were evaluated by Optical microscope, X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM-EDS) analysis. The experimental results revealed that the increase of slag content improved the strength and reduced workability. Moreover, some microcracks were observed when over 15% of fly ash was replaced with slag. In terms of activators, the sodium metasilicate anhydrous provided optimum strength and higher flowability compared to the others. Microstructural analysis results showed the presence of more unreacted particles when less than 8% Na2SiO3 content as alkaline activator and also less than 15% slag as replacement was used in the system.

A study on the effect of nano clay and GGBS on the strength properties of fly ash based geopolymers

The role of reactive alumina and process variables such as sodium content and molarity on alkaline activation of different Nano clay and GGBS are explored. The reactive alumina content of fly ash is the key parameter which determines the maximum compressive strength achieved from the alkaline activation. In this paper, Effects of the incorporation of nano-clay in fly ash based geopolymer binders have been investigated. Low-calcium fly ash was used as the principal source of alumino silicate and it was blended with blast furnace slag in small percentages in order to accelerate the curing at room temperature. Nano-clay was added at different rates to the total binder on the 3, 7 and 28 day of curing.

Dielectric properties for characterization of fly ash-based geopolymer binders

In this study, a method for determining the setting time and the porosity of fly ash-based geopolymer binders (FAGPBs) has been established. This method permits a real-time monitoring of the geopolymerisation and hardening progressions. A parallel plate capacitor cell technique was used to determine the dielectric constant εr' and dielectric loss factor εr'' of fresh and hardened mixes. Equivalent model-circuits of the measurement system were developed, and the accuracy of the system was verified. The dielectric properties were monitored at different ages until 56 days over a frequency range of 0.1–60 MHz. The alkaline solution to fly ash ratio, sodium silicate to alkaline solution ratio, and sodium hydroxide solution molarity were varied to study their effects on the dielectric properties. It was found that dielectric properties can provide valuable information when measured in the frequency range of 10–25 MHz. In this range, the dielectric values responded well to the variations with age and with mix properties. The relationships between the dielectric properties and the different physical states and constituent materials of FAGPBs could be used for quality control applications. The εr' and εr'' time plots were effectively utilized to determine the setting time and the rate of geopolymerisation of FAGPBs. Measurements showed a strong correlation between εr' and porosity; the εr' values decreased 2.3-fold over a porosity range of 3–15%. The proposed regression models can be further used in determining the porosity of FAGPBs at a high accuracy level.

The Effect of Baggase Ash on Fly Ash-Based Geopolimer Binder

Geopolymer concrete is an environmentally friendly concrete. However, the geopolymer binder has a problem with setting time; mainly the composition comprises high calcium fly ash. This study utilized bagasse ash to improve setting time on fly ash-based geopolymer binder. The characterization of bagasse ash was carried out by using chemical and phase analysis, while the morphology characterization was examined by scanning electron microscope (SEM). The setting time test and the compressive strength test used standard ASTM C 191-04 and ASTM C39 / C39M respectively. The compressive strength of the samples determined at 3, 28 and 56 days. The result compared the requirement of the standards.

Parameters Affecting the Mechanical Properties of Fly Ash-Based Geopolymer Binders – Experimental Results

As the demand for concrete and the needs to satisfy development of infrastructure facilities increase, it is essential to find alternatives to create environment-friendly concrete. The particular procedure of alkaline activation of fly ash - in which ash resulting from a power plant is combined with a specific alkaline activator in order to create a solid material, then dried at a certain temperature - opened new opportunities for this new material to get attention worldwide. In order to obtain a material with similar properties of ordinary Portland cement concrete and to obtain desirable compressive strengths, the parameters that affect this type of binders should be fully understood. The aim of this paper is to study the main parameters affecting the mechanical strength of the fly ash-based geopolymer paste and their interactions. Parameters such as molarity of sodium hydroxide (from 8M to 12M) and alkaline activators ratio (from 0,5 to 2,5) were analysed to observe how they affect the mechanical properties of the geopolymer paste. Experimental results show that the compressive strength of the fly ash-based geopolymer paste produced using Romanian local raw materials increases with the increase of the concentration of sodium hydroxide and higher ratios of Na2SiO3/NaOH solution.

Statistical modeling and mix design optimization of fly ash based engineered geopolymer composite using response surface methodology

Abstract Fly ash-based geopolymer binders have been identified as one of the alternatives to the Ordinary Portland Cement (OPC), which qualify the criteria of green construction material. In the process of enhancement of the properties of geopolymer; engineered geopolymer composite (EGC) is a recent development that is classified as the high-performance fiber reinforced geopolymer matrix. The philosophy of the development of EGC is to achieve high compressive strength and ductility. In this paper, statistical models are developed to predict the mechanical and post-cracking properties of EGC using Response Surface Methodology (RSM). In this regard, effects of three principal variables; molarity of sodium hydroxide, sodium silicate to sodium hydroxide ratio, and curing temperature on the properties of fresh and hardened EGC (setting time, compressive strength, elastic modulus, flexural strength, flexural toughness, ductility index, tensile strength, tensile first crack strength and tensile strain capacity) were investigated. All models are found significant because, and the difference between predicted R2 and adjustable R2 was found less than 0.2. The optimized mixture proportion was assessed using multi-objective optimization technique as discussed in the RSM literature. Finally, an experimental program was performed to validate the optimized mixture proportion. The predicted and experimental results were found in a close agreement because the variation between the predicted and the experimental results was obtained less than 5%. The proposed method can be performed for any objective value of the EGC property with desirability almost equal to one, improving the yield, the reliability of the product and the processes.