Blended Fly Ash Research Articles

Performance evaluation of fly ash–copper slag-based geopolymer bricks

This study investigates the production and evaluation of geopolymer bricks made from a blend of fly ash, copper slag, soda ash activator, and sand as fillers. Locally abundant industrial and mining waste materials were selected as the primary components. The bricks were synthesized using two binders: 60% fly ash with 40% copper slag, or 70% fly ash with 30% copper slag. Both were milled with the activator at a 0.2 soda ash-to-precursor ratio. Fine sand was added to the mixes at 1:2 and 1:3 binders-to-sand ratios. The bricks’ physical, mechanical, and durability properties were examined through compressive strength, modulus of rupture, density, water absorption, drying shrinkage, and efflorescence test, and their performance was compared to established industry standards. The experimental findings indicate that bricks made with 60% fly ash, 40% copper slag, and a 1:2 binder-to-sand ratio exhibited optimal compressive strength (9.64 MPa) and water absorption (7.5%) at 28 days of curing age. Conversely, there was only a marginal increase of up to 4.7% in the strength of the formulation with 70% fly ash and 30% copper slag, attaining a compressive strength of 4.9 MPa between the curing ages. Furthermore, the results indicated a positive correlation between the density and compressive strength of the geopolymer bricks at similar curing ages. The bricks’ density showed minimal variation with curing age and the highest modulus of rupture value observed was 2.5 MPa. The optimal bricks also exhibited relatively low linear shrinkage, good resistance to efflorescence, and met the relevant industry standards.

Experimental study on the stabilization of marine soft clay as subgrade filler using binary blending of calcium carbide residue and fly ash

This study endeavors to realize the concurrent utilization of marine soft clay (MSC) and industrial waste, specifically calcium carbide residue (CCR) and fly ash (FA), through a series of experimental investigations. The optimal ratio between CCR and FA, as well as the efficacy of the composite agent (CF–1), were examined, and an empirical equation associating the unconfined compressive strength (qu) of stabilized MSC was developed through unconfined compressive strength (UCS) tests. Microscopic analyses, including X–ray diffraction (XRD), scanning electron microscopy (SEM), and energy–dispersive spectroscopy (EDS), were employed to unveil the intrinsic mechanisms underlying CF–1 stabilized MSC. Subsequently, the suitability of CF–1 solidified MSC as a roadbed filler was ascertained through laboratory tests. Results revealed the optimum CCR:FA ratio for CF–1 to be 4:1, demonstrating superior curing effects compared to individual components such as Portland cement (PC), CCR, and FA, with commendable environmental and economic benefits. The developed empirical equation exhibited effectiveness in predicting the qu of CF–1 solidified MSC under varying curing dates (T) and dosages (Wg) conditions. Characterization through XRD, SEM, and EDS identified the primary products formed within the stabilized MSC matrix with CF–1 as comprising calcium–silicate–hydrate (C–S–H) gel, calcium–aluminate–hydrate (C–A–H) gel, and a minor amount of calcite. As T and Wg increased, the reduction in pores between soil particles enhanced the structural integrity and macro–strength of the cured MSC. The failure pattern of CF–1–solidified MSC elementary samples depended on the CF–1 dosage and curing duration. The solidification mechanism of CF–1 on MSC involved pozzolanic, ion exchange, and carbonation reactions. CF–1 solidified MSC satisfied all the specified requirements for roadbed filler in the relevant code, demonstrating substantial potential for in–situ solidification projects involving MSC.

CONVERSION OF ALUMINO-SILICEOUS REJECTS FROM POWER AND STEEL INDUSTRIES INTO BINARY GEOPOLYMER BRICK: EXPLOITING-GBFS MATERIAL SYNERGY UNDER AMBIENT CONDITIONS FOR SUPPORTING CIRCULAR ECONOMY

In recent year, advances in construction material have enabled the utilization of abundant reject material for value added purposes. The mining and metallurgical industries, particularly those with mineral rich rejects, have emerged as alternative sources of material for the construction application. The combination of granulated blast furnace slag (GBFS) from the steel industry and fly ash (FA) has been identified as one of the most suitable materials combinations for producing geopolymer blocks without the need for reinforcement or with the additives. Binary blended FA and GBFS based geopolymer bricks were cast with variable raw precursors and activator ratio using mini brick plant setup and cured at ambient temperature. The decisive parameters based on Indian standards forwhich the testing was done are compressive strength, water absorption, efflorescence and density. The compressive strength achieved for the test cubes casted for prism test was in the range of 20 - 30 MPa at ambient temperature. The bricks were found to meet the requirements established by Indian Standard 1077:1992 for producing energy-efficient masonry products. The cost and embodied energy (EE) of the developed geopolymer bricks were estimated. As being a binary blend of FA and GBFS cured at room temperature, the developed bricks could reduce the EE and carbon dioxide emission (CO2) and energy required for heat curing. The comparative analysis for the conventionally available bricks with the geo-brick showed promising results. Utilization of steel and power industry waste is a way to achieve circular economy in the waste.

Eco-Efficient Mortars for Sustainable Construction: A Comprehensive Approach

Cement production is responsible for approximately 7% of global carbon dioxide emissions. Despite our efforts, we have not been able to find a competitive substitute that is both reliable and environmentally friendly. The easiest way to solve the issue is to rationalize resources and try to minimize their use by replacing them with other materials. The current market shortage and reduced initial strength have limited the availability of blends that contain a significant amount of fly ash. Given the current economic, political, and environmental circumstances, it is predicted that a solution may be ternary blends with cement, fly ash, and MTK. Despite being “ancient” materials, there have been no recent global performance assessments. In this context, an investigation was carried out with ternary blend mortars. A significant volume of cement has been replaced with fly ash and metakaolin. The results show that these blends’ performance is promising because they offer a wide range of possibilities for replacing cement, maintaining or even improving its properties. MTK and fly ash’s synergies significantly enhance mechanical performance and durability. Furthermore, the global sustainability analysis shows that ternary blends are 36% more efficient than binary blends of cement and fly ash or metakaolin.

Hydration characteristics and hydration products of calcium sulfoaluminate cement and fly ash blended pastes

This study investigated a binary blend of calcium sulfoaluminate cement and fly ash with a target compressive strength of more than 32.5 MPa based on the EN 197-1 standard, using as much fly ash as possible. In the binder system of calcium sulfoaluminate cement and fly ash, a decrease in the replacement level of fly ash results in an increase in compressive strength. Mortar with a 40% replacement level of fly ash for calcium sulfoaluminate cement and added gypsum shows 49.41 MPa strength at 28 d. Its hydrates are hydroxy-AFm, ettringite, crystalline aluminum hydroxide, amorphous aluminum hydroxide, strätlingite, and monosulfate. They are attributed to the hydration of ye’elimite, C2S, and C3A in calcium sulfoaluminate cement. The reactivity of fly ash is not observed until 28 d of hydration. The formation of ettringite is the main cause of the gains in compressive strength.

Experimental study on the mechanical behavior of concrete incorporating fly ash and marble powder waste

This research is focused on the development of an eco-friendly low-cost concrete using fly ash (FA) and marble powder waste (MPW) as partial replacements for cement and fine aggregate respectively. The substantial use of cement in concrete makes it expensive and contributes to global warming due to high carbon emissions. Thus, using such waste materials can help reduce the overall carbon footprint. For this purpose, various mix designs of concrete were developed by varying the percentages of FA and MPW. The concrete's fresh and hardened properties were experimentally determined for those mixes. The test results revealed that MPW as a sand substitute increases strength up to 40% and gradually decreases beyond that, but a 60% replacement still has more strength than the control specimen. Similarly, using FA as a cement replacement was found to reduce the strength, but the reduction was not very significant up to 20%. A mixed blend of FA and MPW showed superior results and maximum strength was obtained at F10M40. The optimal mix, with 10% FA and 40% MPW (F10M40), achieved a compressive strength of 4493.46 psi, a 16.21% improvement compared to the control mix proportion. Furthermore, the microstructure of the cementitious material was improved due to the pozzolanic reaction that led to a denser microstructure, as supported by the permeability test and SEM analysis.

Rheological Characterization of Inorganic Curing Foam for Preventing Spontaneous Combustion of Coal

ABSTRACT This study examines the rheological characteristics of inorganic cured foam (ICF). The apparent viscosity, yield stress, and modulus of elasticity of fresh cement-fly ash composite slurries with varying fly ash blending ratios at water/ash ratios of 0.4, 0.5, 0.6, and 0.7 were determined. The findings indicate that, under identical testing conditions, the apparent viscosity, yield stress, and modulus of elasticity of fresh cement-fly ash composite slurries (FCFS) gradually decrease with increasing water/ash ratio. The apparent viscosity and modulus of elasticity of inorganic curing foam (ICF) decrease as the volume expansion rate increases, while the linear viscoelastic region (LVER) broadens with higher volume expansion rates. Furthermore, the fitted apparent viscosity-shear stress curve for FCFS aligns with the power law model, whereas the apparent viscosity-shear stress curve for ICF slurries is better represented by the Carreau-Yasuda function model. The results of the study will contribute to the industrial application of inorganic curing foams for the prevention of spontaneous coal combustion.

Can Geopolymer Be a Replacement for Portland Cement in Full-Depth Reclamation Projects? Short- and Long-Term Performance Analysis

The fundamental concern of the full-depth reclamation (FDR) technique using Portland cement (FDR-PC) lies in its detrimental effect on the environment. Therefore, researchers are exploring alternative binders that are comparatively greener but compatible with FDR. This study evaluates both the strength and durability aspects of FDR incorporating geopolymer binder (FDR-GP) as an alternative to conventional FDR-PC. Various blends of fly ash (FA) and ground granulated blast furnace slag (GGBS) have been experimented with as geopolymer pre-cursors, ensuring that the additive content does not exceed 20% by weight of the total mix. Sodium hydroxide (NaOH) was utilized for the alkalinization in varying molarities to enhance the performance of the mixes. The experimental design was formulated to achieve a target 7-day unconfined compressive strength (UCS) strength of 4.95 MPa. This was obtained at a lower molarity (M) of 2 M and a 70% FA, 30% GGBS binder content. The mixes performed satisfactorily in both compression and flexure, along with excellent durability properties analyzed through wetting and drying tests. Furthermore, the long-term performance of FDR-GP mixes was investigated with regard to both UCS and flexural strength after 56, 161, and 238 days of curing. Thereafter, a comprehensive microstructural analysis was conducted to understand the fundamental changes in the matrix that influence mix performance. The outcome of this research confirms the potential of using FA/GGBS-based geopolymer as an alternative binder in FDR projects of flexible pavement, the mechanical and durability properties of which adequately satisfy the requirements as stipulated in various design standards.

High-temperature properties of fly ash and silica fume composite magnesium potassium phosphate cement

Magnesium potassium phosphate cement (MKPC) is extensively employed in patching materials and fireproof coatings owing to its outstanding properties. This study employs a blend of fly ash and silica fume to substitute a portion of the cementitious materials, aiming to enhance the performance of MKPC under high-temperature conditions. The relative proportions of fly ash and silica fume were considered. MKPC was subjected to cubic compression and three-point flexural tests. Additionally, the phase and microstructure of MKPC were also characterized using XRD and SEM. The compressive strength, flexural strength, visual appearance, and mass loss of MKPC specimens were evaluated before and after exposure to various high temperatures. Following exposure to elevated temperatures, MKPC specimens without fly ash and silica fume doping showed a significant decrease in strength. Conversely, specimens doped with 15 % or 10 % silica fume exhibited the most remarkable strength enhancement. The dehydration of K-struvite at elevated temperatures was the primary reason for the mass loss and strength reduction of MKPC. Silica fume and fly ash can facilitate the sintering of phases and amorphous particles derived from K-struvite decomposition, leading to the formation of ceramic-like structures. Notably, the contribution of silica fume to the sintering effect exceeds that of fly ash. Therefore, blending fly ash and silica fume proves to be an effective approach to enhancing the high-temperature resistance of MKPC.

Synthesis and multi-objective optimization of fly ash-slag geopolymer sorbents for heavy metal removal using a hybrid Taguchi-TOPSIS approach

This study develops and evaluates a highly effective geopolymer sorbent specifically designed for the removal of heavy metals from wastewater. Single and binary blends of fly ash and slag were utilized as the binding material. The geopolymer composite was activated using either sodium hy solely or in combination with sodium silicate. The Taguchi method was employed to design the geopolymer mixes, having four factors, each with four levels of variation. These factors included the fly ash-to-slag ratio (FA), binder content (BC), the molarity of the sodium hydroxide solution (M), and the sodium silicate-to-sodium hydroxide ratio (SS/SH). The performance of the geopolymer sorbent was rigorously assessed against a comprehensive set of criteria, including metal sorption capacity, setting time, flowability, density, compressive strength, abrasion resistance, water absorption, permeable voids, sorptivity, carbon footprint, and cost. The TOPSIS methodology was applied to aggregate the response criteria and determine the optimal mix for superior performance. The results showed that the optimum mix consisted of an FA of 33 %, BC of 1050 kg/m3, M of 10, and SS/SH of 3. A sensitivity analysis confirmed that changes in the weighting of the performance criteria did not significantly impact the proportioning of the optimum mix. Furthermore, the analysis of variance (ANOVA) revealed that the FA contributed the most to the sorbent’s performance, followed by the SS/SH, BC, and M. The development of this geopolymer sorbent not only addresses a critical environmental concern but also offers great potential for practical applications in industries and municipalities worldwide.

Carbonation and corrosion of steel in fly ash concrete, concluding investigation of five-year-old laboratory specimens and preliminary field data

Carbonation development and reinforcement corrosion were investigated on concretes exposed for a five-year period at 90% RH, 20 ℃, and 5% CO2, and for a six-year period at natural carbonation. Portland cement-based binders with 0%, 18%, and 30% fly ash were investigated. The fly ash blends showed lower carbonation resistance compared to PC both at laboratory and field exposure, a large difference in carbonation performance was observed between the laboratory exposed specimens. The carbonation rate was fastest on the laboratory specimens and showed square-root time dependency the first 2.5 years, but reduced rate at later age. Deeper carbonation depths were in general observed in the vicinity of the reinforcement compared to the unreinforced laboratory exposed specimens. Not all specimens were fully carbonated at the steel-concrete interface. The correlation between degree of carbonation of the steel-mortar interface, the open circuit potential, and the observed corrosion of the steel bars varied between binders and bar position (top or bottom). The measured corrosion rate in the laboratory exposed (90% RH, 20 ℃, and 5% CO2) carbonated concrete was on average 0.2 μA/cm2, with an upper value of 0.6 μA/cm2. The highest corrosion rate was measured in the fly ash concrete. No corrosion rate data are yet available for the field exposed concretes.

Feasible study on optimal utilization of blended fly ash and GGBS on the performance of concrete

Feasible study on optimal utilization of blended fly ash and GGBS on the performance of concrete

Experimental Study on Workability, Strength & Durability of Geopolymer Concrete with use of Fly ash, Ground Granulated Blast Furnace Slag & Silica Fume

Abstract: Geopolymer concrete, crafted from a blend of Fly Ash, GGBS, and Silica Fume activated by sodium silicate and sodium hydroxide, demonstrates excellent workability and strength over time. It proves resilient against acid, chloride, water absorption, and carbonation, making it a sustainable choice for construction projects seeking durability and performance. These qualities position geopolymer concrete as a promising alternative to traditional concrete methods.

Geotechnical Properties of Fly Ash Blended Expansive Soil: A Review

Fly ash, an industrial byproduct, is used as both a building material and a soil stabilizer due to its pozzolanic properties. Moreover, it is challenging to extrapolate the results based on an inadequate amount of laboratory data because of the non-homogeneous character of the soil and the diversity in the chemical properties of fly ash. This review article fills in the gaps by providing an overview of the existing data related to the geotechnical characteristics of expansive soil stabilized with fly ash. The chemical composition of fly ash is provided in terms of oxides of various elements to help identify the kinds produced in different nations. Additionally, information about the physical and geotechnical characteristics of fly ash blended expansive soil is provided in order to comprehend the influence of the fly ash's chemical composition and the expansive soil's fines percentage. While the geotechnical property comprises Atterberg's limit, compaction, UCS, shear strength, free swelling index, CBR, and consolidation, the physical property includes specific gravity and durability. Shear modulus, damping ratio, and Poisson's ratio are used to describe the dynamic properties of the modified expansive soil. The published data in this field and the research gap will be identified by the researchers with the aid of this article. Doi: 10.28991/CEJ-SP2024-010-06 Full Text: PDF

MECHANICAL AND HYDRAULIC PERFORMANCE OF PERVIOUS RECYCLED AGGREGATE GEOPOLYMER CONCRETE

The widespread expansion of the global economy and the increase in human population have been major contributors to pollution and environmental complications. Construction and demolition wastes (CDW), impervious pavement surfaces, and industrial waste disposal sites have emerged as serious environmental challenges over the past decade. These challenges must be addressed through the synergic use of different sustainable practices, including pervious surfaces, CDW, and industrial wastes. Their combined utilization produces a pervious geopolymer concrete made with recycled concrete aggregates (RCA). This research aims to develop and assess the mechanical and hydraulic properties of pervious geopolymer recycled aggregate concrete (PGRAC) with a design porosity of 15%. The mixes were made with two binder blends of ground granulated blast furnace slag and fly ash (1:0 and 1:1) and RCA replacement of 0 and 100%. The mechanical and hydraulic performance were characterized by compressive strength and permeability, respectively. Results showed that pervious concrete made with natural aggregates and comprising a binder blend of slag:fly ash of 1:0 demonstrated 36% higher compressive strength than counterparts having a binder blend of 1:1. Meanwhile, the permeability was unaffected by the variation in the binder. At 100% RCA, the compressive strength of mixes having a binder blend of 1:0 was 192% higher than that of the equivalent mix having a binder blend of 1:1. Yet, the latter had 12% higher permeability than the former. These research findings demonstrate the ability to produce sustainable PGRAC for use in pavement applications.

MECHANICAL AND HYDRAULIC PERFORMANCE OF PERVIOUS RECYCLED AGGREGATE GEOPOLYMER CONCRETE

The widespread expansion of the global economy and the increase in human population have been major contributors to pollution and environmental complications. Construction and demolition wastes (CDW), impervious pavement surfaces, and industrial waste disposal sites have emerged as serious environmental challenges over the past decade. These challenges must be addressed through the synergic use of different sustainable practices, including pervious surfaces, CDW, and industrial wastes. Their combined utilization produces a pervious geopolymer concrete made with recycled concrete aggregates (RCA). This research aims to develop and assess the mechanical and hydraulic properties of pervious geopolymer recycled aggregate concrete (PGRAC) with a design porosity of 15%. The mixes were made with two binder blends of ground granulated blast furnace slag and fly ash (1:0 and 1:1) and RCA replacement of 0 and 100%. The mechanical and hydraulic performance were characterized by compressive strength and permeability, respectively. Results showed that pervious concrete made with natural aggregates and comprising a binder blend of slag:fly ash of 1:0 demonstrated 36% higher compressive strength than counterparts having a binder blend of 1:1. Meanwhile, the permeability was unaffected by the variation in the binder. At 100% RCA, the compressive strength of mixes having a binder blend of 1:0 was 192% higher than that of the equivalent mix having a binder blend of 1:1. Yet, the latter had 12% higher permeability than the former. These research findings demonstrate the ability to produce sustainable PGRAC for use in pavement applications.

Effects of Using Cold Bonded Coarse and Fine Calcined Attapulgite Lightweight Aggregates on the Performance Properties of Microsilica and Fly Ash Blended Concretes

Effects of Using Cold Bonded Coarse and Fine Calcined Attapulgite Lightweight Aggregates on the Performance Properties of Microsilica and Fly Ash Blended Concretes

Green engineered cementitious composites with enhanced tensile and flexural properties at elevated temperatures

This study provides new insights in the design of green hybrid polyethylene (PE)-steel fibre reinforced high strength engineered cementitious composite (HSECC) with superior tensile and flexural strength at both ambient and elevated temperatures. Blends of high volume of ground granulated blast furnace slag (GGBFS), dolomite powder and fly ash were utilized to achieve a 60 % cement replacement for the HSECC mixes. These mixes were then exposed to 20–600 °C and a total of 210 specimens were tested to assess their residual tensile stress–strain behaviour, flexural load–displacement response, and toughness. Results indicate that high volume of GGBFS can be very effective in limiting the surface damage and retaining high strength at elevated temperatures. A combination of 1.5 % PE-0.75 % steel with quaternary blend of GGBFS, dolomite and fly ash demonstrated at least 60 % and 40 % retention in tensile and flexural strength at 600 °C, respectively. This was significantly better than the strength of the traditional control silica fume mix considered in this study as well as results reported in many previous literatures on HSECC. Microstructural examination was further conducted to understand the mechanism of fibre deterioration and justify the resulting change in pseudo-hardening behaviour with temperature rise. Findings obtained in this study clearly demonstrated the effectiveness of PE-steel fibre hybridisation at elevated temperature and confirmed that with right binder selection, superior tensile and flexural performance can be achieved even with a very high cement replacement level.

Evaluation of Alkali-Activated Mortar Incorporating Combined and Uncombined Fly Ash and GGBS Enhanced with Nano Alumina

The present research focuses on assessing the fresh and hardened properties as well as the durability performance of alkali-activated mortar in an ambient environment and the impact of integrating nano-alumina (NA) at a 2% ratio as a substitute for binder materials in alkali-activated mortar (AAM). Additionally, it assesses the effectiveness of alkali-activated mortar employing different blends of ground granulated blast furnace slag (GGBS) and fly ash as environmentally friendly substitute building materials. Fly ash (FA), ground granulated blast slag (GGBS), and an equal mixture of GGBS and FA make up these binder ingredients. As a result, the main binders contain GGBS, FA, or a 50/50 mixture of GGBS and FA. The sodium hydroxide (NaOH) concentration is fixed at a 12-molarity level, and the alkali activator solution to binder ratio is kept at 0.5. In the alkali solution, the ratio of sodium silicate to sodium hydroxide is always 2.5. The study evaluates various properties of AAM, such as compressive strength, flowability, unit weight, flexural tensile strength, and durability, under ambient conditions at a steady room temperature of 23±3°C. Results indicate that AAM mixtures devoid of NA exhibit a higher flow rate compared to those containing NA. Nonetheless, the flowability of AAM mixtures aligns well with standard requirements, being modest yet adequate. Significantly, the inclusion of NA enhances the mechanical properties and durability of AAM, demonstrating its beneficial effects. Doi: 10.28991/CEJ-2024-010-03-016 Full Text: PDF

Durability and Cost Analysis of High-Volume Fly Ash Blended Self-Compacting Mortar

Durability and Cost Analysis of High-Volume Fly Ash Blended Self-Compacting Mortar