Furnace Slag Geopolymer Research Articles

Kinetics and simulation of biodiesel production using a geopolymer heterogenous catalyst

This work aims to develop a comprehensive kinetic and simulation study of biodiesel production using waste cooking oil (WCO) catalyzed by blast furnace slag geopolymer (BFSG) as a heterogeneous catalyst. The kinetic investigation was established following the pseudo-first and second-order model using three reaction parameters, namely, the reaction temperature (40–60 °C), reaction time (4–8 h) and catalyst ratio (6–14 wt.%), while maintaining a constant methanol-to-oil composition of 40 wt.%. The geopolymer-catalyzed transesterification process was simulated using ChemCAD version 8.1.0, which incorporates the four major triglycerides (triolein, tripalmitin, tristearin and triolein) of WCO. The results of the transesterification reaction of WCO in a kinetic plug flow reactor (PFR) demonstrated a good fit of the data, with an R 2 above 0.96 in both cases. The pseudo-first-order (PFO) model revealed a more favorable reaction pathway, with an activation energy of 58.876 kJ.mol−1, as opposed to the value of 131.369 kJ.mol−1 obtained from the pseudo-second-order (PSO) analysis. The catalytic activity of BFSG yielded a maximum conversion of 99.18% at a 12 wt.% catalyst ratio. The study results demonstrated the effectiveness of the transesterification process catalyzed by BFSG as a promising low-cost technology for the biodiesel industry.

Mechanical properties of bentonite soil stabilized with rice husk ash and ground granulated blast furnace slag geopolymer

Mechanical properties of bentonite soil stabilized with rice husk ash and ground granulated blast furnace slag geopolymer

Synthesis of BiOX-Red Mud/Granulated Blast Furnace Slag Geopolymer Microspheres for Photocatalytic Degradation of Formaldehyde.

Release of formaldehyde gas indoors is a serious threat to human health. The traditional adsorption method is not stable enough for formaldehyde removal. Photocatalytic degradation of formaldehyde is effective and rapid, but photocatalysts are generally expensive and not easy to recycle. In this paper, geopolymer microspheres were applied as matrix materials for photocatalysts loading to degrade formaldehyde. Geopolymer microspheres were prepared from red mud and granulated blast furnace slag as raw materials by alkali activation. When the red mud doping was 50%, the concentration of NaOH solution was 6 mol/L, and the additive amount was 30 mL, the prepared geopolymer microspheres possessed good morphological characteristics and a large specific surface area of 38.80 m2/g. With the loading of BiOX (X = Cl, Br, I) photocatalysts on the surface of geopolymer microspheres, 85.71% of formaldehyde gas were adsorbed within 60 min. The formaldehyde degradation rate of the geopolymer microspheres loaded with BiOI reached 87.46% within 180 min, which was 23.07% higher than that of the microspheres loaded with BiOBr, and 50.50% higher than that of the microspheres loaded with BiOCl. While ensuring the efficient degradation of formaldehyde, the BiOX (X = Cl, Br, I)-loaded geopolymer microspheres are easy to recycle and can save space. This work not only promotes the resource utilization of red mud and granulated blast furnace slag, but also provides a new idea on the formation of catalysts in the process of photocatalytic degradation of formaldehyde.

Triaxial Stress-Strain Behavior of a Novel Basalt Rock Waste and Ground Granulated Blast Furnace Slag Geopolymer

Triaxial Stress-Strain Behavior of a Novel Basalt Rock Waste and Ground Granulated Blast Furnace Slag Geopolymer

Transformation of rice husk modified basic oxygen furnace slag into geopolymer composites

Synergistic use of industrial and agricultural by-products can be solution of carbon emission from construction industry. The whole world is facing a crisis in finding ways to dispose of waste material. Hence, this study attempts to use rice husk and rice husk ash in geopolymers. Thus the study aims to develop a rice husk/basic oxygen furnace slag based geopolymer and study the factors affecting the performance of the binder. The developed geopolymer specimens were characterized using mechanical testing, physical and chemical techniques. The expansive nature of the organic matter in rice husk resulted in the geopolymer expanding and cracking. For this reason, rice husk ash was used to replace basic oxygen furnace slag. The rice husk was calcined at 600 °C to produce rice husk ash. The amount of rice husk ash as a replacement for basic oxygen furnace slag geopolymer varied from 0% to 50%. The effect of NaOH concentration, solid/liquid ratio, Na2SiO3/NaOH ratio, and the curing temperature was also studied to investigate the optimum parameter. The unconfined compressive strength is used to determine the performance of the binder. The results indicated an uptrend in unconfined compressive strength when increasing the rice husk ash content from 5% to 10%, and the optimum was 10%. Specimen with 8 M NaOH concentration had the highest unconfined compressive strength of 6.285 MPa. Moreover, it was also found that curing at 80 °C is an optimum condition for curing. Efflorescence formation and alkali leaching increased with the increase in rice husk ash content.

Research on Reducing Shrinkage Behavior of Ground Granulated Blast Furnace Slag Geopolymers Using Polymer Materials

Geopolymers are a new type of environmentally friendly cement-based material with serious drying shrinkage problems. In order to overcome this problem and improve the engineering performance and durability of geopolymers, in this study we added 0%, 0.3%, 0.5%, 0.7%, and 0.9% polymer materials, namely, polyacrylamide, sodium polyacrylate, and sodium tetraborate, respectively, to geopolymers to reduce their degree of shrinkage. We also assessed changes in their length and durability to determine how the addition of polymer materials could reduce their degree of shrinkage. The results indicate that 0.7% sodium tetraborate yielded the most favored shrinkage, and, through imaging technology, the crack change at the age of 0–3 days was measured, during which polyacrylamide (PAM) effectively slowed down the dimensions of crack propagation by 0.47% compared with the control group.

Influence on Rheology and Microstructure of Nanosilica and Modified Polycarboxylate in Water‐Glass‐Activated Fly Ash/Ground Granulated Blast Furnace Slag Geopolymers

AbstractThis study establishes the effect of nano silica (NS) in the alkali activator on the behaviour of rheology and microstructure of Alkali activated material. The rheological behaviour of the Fly ash (FA)‐Ground granulated blast furnace slag (GGBS) (4 : 1) activated using water glass of Ms 1.1 (SiO2/Na2O), with nano silica (NS), Modified Poly carboxylate (MPC) was studied and the link between the composition and fundamental behaviour are reported. A total of 12 mortar mixtures were cast by varying the dose of NS from 0–3 %, and MPC 0–2.5 % and their fresh properties were obtained from the slump, setting time and flow value. The compressive strengths of mortars showed an increasing trend from 40 to 55 MPa with NS addition from 0–2.5 wt% at an optimal dose of 1 % MPC. The suspensions with and without NS fit well with Herschel‐Bulkley model, in the hysteresis cycle. The incorporation of NS at a threshold value below 2 % leads to a drastic change in viscosity with increasing time at a constant shear rate, implying. a thixotropy with yield‐type behaviour that are associated with the rebuilding of the flocculated structure with time. The nucleating effect of NS progressively improved the strength of the mix, due to the formation of compact gel microstructure which was confirmed by SEM micrograph with fewer pores. NS improves CSH gel and gelatinous silica phase in the matrix as is evident from the formation of the SiQ4 structural unit as it is absent in control. The poly (Sialate) structural unit in geopolymer ascertained from 29Si, 27Al MAS NMR chemical shift corresponds to Alq3(3Si) with the absence of remnant Al(IV) peak of Fly ash in NS (2.%) activated samples.

Comparison of thermal performance between fly ash geopolymer and fly ash-ladle furnace slag geopolymer

This paper compared the thermal stability between fly ash (FA) and fly ash-ladle furnace slag (FA-LS) geopolymers. FA-LS geopolymer was prepared by mixing FA and LS (FA:LS weight ratio of 80:20) with an alkali activator. Geopolymers were aged at room temperature for 28 days before being exposed to high temperatures (200 °C – 1000 °C). Unexposed FA and FA-LS geopolymers had a compressive strength of 38.9 MPa and 40.5 MPa, respectively. The FA and FA-LS geopolymers retained 61.6% and 91.3% compressive strength, respectively, when exposed to temperatures up to 1000 °C. FA-LS geopolymers experienced smaller variation in the density (2.6 – 5.5%) and pores (17.4 – 23.0%) compared to FA geopolymers (density and porosity of 2.9 – 25.2% and 19.0 – 30.0%, respectively). The formation of crystalline peaks, densification of matrix, pores and their connectivity, cracks and dimensional changes influenced the compressive strength of exposed geopolymers. FA-LS geopolymers could be potentially applied as heat-resistance material.

Freeze-thaw resistance of blast furnace slag alkali activated mortars

In this study, blast furnace slag geopolymer mortars were prepared in prism molds with the size of 4 x 4 x 16 cm by alkali activating powdered sodium meta silicate (Na2SiO3). The mortar mixtures prepared to contain sodium in different proportions were cured with 3 different curing methods, and 300 cycles of freeze-thaw were applied, and strength and weight losses were examined. Control samples prepared with PC were also exposed to freeze-thaw cycles and the results were compared with each other. It was observed that 8% sodium added geopolymer mortars significantly preserved their compressive strength and weight. Especially, the compressive strength of the samples produced with 8% sodium and exposed to freeze-thaw cycle after 28 days of air curing increased by around 32%.

Removal of Heavy Metals from Wastewater Using Fly Ash Modified Basic Oxygen Furnace Slag Geopolymers

In the current study, fly ash modified basic oxygen furnace slag geopolymers were synthesized and used as geofilters to remove heavy metals from wastewater. Batch experiment based on the removal of heavy metals from synthesized wastewater was conducted so as to investigate the influence of contact time and porosity on the metal removal efficiency and adsorption capacity of the geofilters. Adsorption kinetics was evaluated using Lagergren's pseudo-first-order model, Ho's pseudo-second order and Elovich models. Effect of contact time between geopolymer and wastewater was investigated within the first 15 minutes of adsorption with time interval of 3 minutes. The highest percentages for the removal of Fe2+, Cu2+, Al3+ and Ni2+ions with 1%H2O2 – FA-BOFS based geopolymer obtained after 15minutes were 100%, 86.87%, 84.64% and 84.63% respectively. The trend based on metal absorption capacities in an ascending order given as Fe >Cu>Ni>Al. The adsorption capacity of metal within the 15miniutes was relatively constant possibly due to sufficient number of sites upon which metal ion adsorption may have possibly occurred on the outer surface of geopolymers irrespective of H2O2 content. Metal ion adsorption rates in the current study strongly adhered to the Ho's pseudo-second-order model based on linear regression fitting method. The correlation coefficients R2 were 0.999. FA-BOFS based geopolymer can be considered as emergent and versatile material with inherent chemical microstructural property able to remove heavy metals from polluted effluent and metalliferous drainage.

Strength and Microstructure Characteristics of Blended Fly Ash and Ground Granulated Blast Furnace Slag Geopolymer Mortars with Na and K Silicate Solution.

Mineral geopolymer binders can be an attractive and more sustainable alternative to traditional Portland cement materials for special applications. In geopolymer technology the precursor is a source of silicon and aluminium oxides, the second component is an alkaline solution. In the synthesis of geopolymer binders the most commonly used alkaline solution is a mixture of sodium or potassium water glass with sodium or potassium hydroxide or silicate solution with a low molar ratio, which is more convenient and much safer in use. In this paper, we present the influence of sodium or potassium silicate solution on the physical and mechanical properties of fly ash and ground granulated blast furnace slag-based geopolymer mortars. Mercury intrusion porosimetry and microstructural observation allowed for comparing the structure of materials with a different type of alkaline solution. The evolution of compressive and flexural tensile strength with time determined for composites using 10%, 30% and 50% slag contents (referring to fly ash mass) was analysed. The tests were performed after 3, 7, 14 and 28 days. It was observed that, as the amount of slag used increases in the precursor, the strength of the material grows. Mortars with the sodium alkaline solution were characterised by a higher strength at a young age. However, the values of strength 28 days were higher for geopolymers with potassium alkaline solution reaching 75 MPa in compression. Geopolymer mortar microstructure observation indicates a high matrix heterogeneity with numerous microcracks. Matrix defects may be caused by the rapid kinetics of the material binding reaction or shrinkage associated with the drying of the material.

The Investigation of Ground Granulated Blast Furnace Slag Geopolymer at High Temperature by Using Electron Backscatter Diffraction Analysis

The Investigation of Ground Granulated Blast Furnace Slag Geopolymer at High Temperature by Using Electron Backscatter Diffraction Analysis

Valorization of fly ash as an additive for electric arc furnace slag geopolymer cement

The precursors of alkali-activated materials (AAMs) have major effects on their properties. More attention was paid to using by-product precursors such as slag and fly ash (FA) for AAMs, whilst less attention was paid to using another by-product precursor such as electric arc furnace slag (EAFS). The use of EAFS as a geopolymer precursor is still under the development stage. Thus, the current paper aims to study the fresh and mechanical properties, as well as durability of EAFS geopolymer cement activated with NaOH and sodium silicate solution. The durability was studied by two parameters named water absorption and chloride penetration permeability. To improve the properties of EAFS geopolymer cement, EAFS was partially replaced with 15–60 wt% FA. X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) were used to analyze the results. The results showed modified properties of EAFS geopolymer cement with the incorporation of FA such as high flowability, high mechanical strength, low water absorption, low charge passed, preventing the formation of microcracks, refining and densifying the microstructure.

Impact of alkali activated mortar incorporating different heavy metals on immobilization proficiency using gamma rays attenuation

The target of the present paper is to investigate the heavy metals effect on the attenuation properties of the geopolymer mortar used as radiation shielding for nuclear facilities. Radiation shielding properties of geopolymer mortar mixtures prepared using different types of heavy metals such as lead phosphate, barium sulfate in addition to some industrial heavy iron metal wastes and lead metals such as electric arc furnace slag (EAFS) and lead slag as partial replacement of blast furnace slag were investigated comparatively with hardened Portland cement mortar. Fine aggregates used were local sand dunes, air cooled slag, and lead slag, while the used activator was 8% sodium hydroxide. The effect of fine heavy metals on the bulk density of geopolymer mortar was investigated, in addition to gamma linear attenuation coefficients for the studied mortar against Cs137 (662 keV) and Co60 (1173 and 1332 keV), also the most important gamma transmission parameters were measured as (half-value layer, HVL; tenth-value layer, TVL and mean free path, MFP). It was found that, the density of the blast furnace slag geopolymer mortar increases upon replacing sand dunes with fine lead slag aggregates as well as air cooled slag. In addition, the geopolymer mortars containing EAFS as fine materials have the highest density compared to lead slag, barium sulfate and lead phosphate, respectively. The results indicate that, blast furnace slag geopolymer mortar made of lead slag as a fine aggregate containing EAFS possess high gamma rays shielding properties compared the other mortars.

ASR potential of nickel slag fine aggregate in blast furnace slag-fly ash geopolymer and Portland cement mortars

Utilizing nickel slag as aggregates in concrete production proposes an economic option for recycling this industrial by-product, and meanwhile preserves the natural rock aggregate resources. Thus, there is an urgent need to further explore the potentially alkali-silica reaction (ASR) nature. This study investigates the ASR of high-magnesium nickel slag (HMNS) fine aggregate in the fly ash-blast furnace slag geopolymer and Portland cement (PC) mortars. No obvious ASR product is observed in the mortars with HMNS fine aggregate, which exhibit lower ASR expansion than the mortars with ASR reactive sand. In the geopolymer mortars, the reactive Al species initially dissolved from HMNS promote the formation of aluminum-containing alkalis silicate gel layer covered on the surface of HMNS grains. This provides a diffuse barrier to protect the inner silica against further attack of alkalis, and consequently mitigates the deleterious ASR. In the PC mortars, the pozzolanic reaction of HMNS improves the consumption of portlandite in the pore solution to reduce the alkalinity and calcium content, resulting in a suppression to the ASR degradation. The accelerated mortar bar test shows that HMNS is reliable for the utilization without deleterious ASR expansion risk.

The Incorporation of Sodium Hydroxide (NaOH) Concentration and CaO-Si Components on Ground Granulated Blast Furnace Slag Geopolymers.

This paper investigates the incorporation of sodium hydroxide (NaOH) concentration and CaO-Si component on ground granulated blast furnace slag geopolymers (GGBFS). An optimal mechanical property of GGBFS with various NaOH concentrations had been determined by performing a number of compressive strength tests. It was found that GGBFS with 10M NaOH concentration resulted in high compressive strength at 65.31 MPa after 28 days curing. The microstructure analysis of the GGBFS geopolymers using SEM and FTIR revealed the formation of calcium silicate hydrate (Ca5Si6O16(OH)2.4H2O) and calcium carbonate (CaCO3) phase within the geopolymer backbone chain. The optimum NaOH concentration allows the acceptable formation of CaO-Si bond on the GGBFS geopolymers main structure and thus leads to optimum compressive strength.

Strength development of solely ground granulated blast furnace slag geopolymers

This paper investigates the strength development of solely ground granulated blast furnace slag geopolymers (GGBFS). An optimal combination of GGBFS with various solid/liquid and alkaline activator ratios had been determined by performing a number of compressive strength tests. It was found that GGBFS with 3.0 solid/liquid ratio and 2.5 alkaline activator ratio resulted in high compressive strength at 168.7 MPa after 28 days of curing. The microstructure analysis of the GGBFS geopolymers using SEM, FTIR and XRD revealed the formation of tobermorite and calcite (CaCO3) phases within a three-dimensional system. In addition, an advanced characterisation non-destructive technique using the synchrotron micro-XRF was performed to reveal detail phase distribution in the system. It displayed that the calcium concentration was higher at silica and alumina regions, which described the formation of tobermorite and CaCO3 as the contributing factor towards high compressive strength.

Behaviour changes of ground granulated blast furnace slag geopolymers at high temperature

In this paper, the thermal performance of ground-granulated blast furnace slag (GGBFS) geopolymers is investigated. The geopolymers were prepared with sodium-based alkali activator and exposed to elevated temperature (200 to 1000°C) after 28 d of curing at room temperature. The unexposed geopolymers exhibited excellent compressive strength of 95 MPa. The compressive strength reduced to 8·9 MPa at 800°C and increased to 19·8 MPa at 1000°C. The strength regained by 122·5% as compared to the residual strength at 800°C. The crack reduction and partial melting in geopolymers treated at 1000°C signifies crack healing at elevated temperature, which in turn increases the compressive strength. In addition, the formation of crystalline phases of gehlenite (Ca2Al2SiO), mayenite (Ca12Al14O33) and larnite (Ca2SiO4) filled the geopolymer matrix and formed an ordered structure. This further enhanced the strength and high-temperature stability of GGBFS geopolymers.

Durability study on coal fly ash-blast furnace slag geopolymer concretes with bio-additives

The objective of this research was to understand the positive impact of bio-additives such as Terminalia chebula and natural sugars (molasses/palm jaggery/honey) on the durability properties of coal fly ash-blast furnace slag (BFS) based geopolymer concrete under various chemical attacks. Various tests had been conducted by immersing specimens in 5% sulfuric acid, 5% sodium sulfate and 5% sodium chloride solution for different duration of 7, 14, 28, 56 and 90 days to determine the resistance of bio-additives added geopolymer concrete against chemical attacks. The durability was also related by mercury intrusion porosimetry to find out the porosity and pore size distribution. After 90 days of immersion, test results confirmed that bio-additives inclusion in coal fly ash-blast furnace slag based geopolymer concrete had undergone weight loss and compressive strength loss in the range of 2.82–3.91%, 9.67–12.05% under sulfuric acid attack, 0.38–0.68%, 2.15–2.95% under sodium sulfate attack and 0.28–0.51%, 0.83–1.33% under sodium chloride attack respectively. However in control ordinary geopolymer specimen, the weight loss and compressive strength loss was 13.97%, 33.57% under sulfuric acid attack, 1.64%, 6.45% under sodium sulfate attack and 0.86%, 2.05% under sodium chloride attack was observed. This led to the conclusion that bio-additives added geopolymer concretes had enhanced durability properties when compared to control ordinary geopolymer concrete examined in this study.

Correlation of the Processing Parameters in the Formation of Granulated Ground Blast Furnace Slag Geopolymer

Geopolymers are inorganic materials with huge potential applications including building material, fire resistant materials, and agricultural construction materials. Various parameters influenced the final properties of these geopolymer concretes. This study developed the effects of several factors such as solid-to-liquid ratio, NaOH concentration, and Na2SiO3/NaOH ratio on the compressive strength of granulated ground blast furnace slag (GGBFS) by statistical design of experiment (DOE) approach. Analysis of the experimental results through ANOVA exhibited that the specimen with NaOH concentration of 10M, Na2SiO3/NaOH ratio equals to 2.5, and solid-to-liquid ratio of 3.0 curing at room temperatures for 28 days was potential of highest strength (168.705 MPa) in the considered procedure. Besides, the relationship between compressive strength and influential factors could be suitably by fraction factorial design method.