F Fly Ash Research Articles

Mock-up pragmatic study on the impact performance of self-compacting concrete incorporating sea sand

Self-Compacting Concrete (SCC) allows for the use of non-desalted sea sand as a fine aggregate, but the durability of triple mix SCC with partial sea sand replacement remains unclear. To optimize binder and fine aggregate replacements, tests for consistency, setting times, soundness, compressive strength, and Ultrasonic Pulse Velocity were performed. Six SCC variations, incorporating 30%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\%$$\\end{document} Class F Fly Ash (FA), 5%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\%$$\\end{document} Ground Granulated Blast Furnace Slag (GGBS), and various fine aggregate combinations, were evaluated for their fresh, mechanical, microstructural, and durability properties. Results demonstrated that SCC with 50%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\%$$\\end{document} sea sand and 50%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\%$$\\end{document} manufactured sand achieved superior 90th\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{th}$$\\end{document} day compressive strength. This improvement was attributed to accelerated cement setting and enhanced FA reactivity, leading to better hydration products. Microstructural analysis revealed more hydration products and fewer pores in specimens with 50%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\%$$\\end{document} sea sand, due to the disconnected pore structure from Friedel’s salt formation. Chloride binding in concrete involves both chemical and physical mechanisms. Chemical binding is related to Friedel’s salt, while physical binding depends on Calcium-Silicate-Hydrate (C-S-H) content. Dense C-S-H formation from sea sand, confirmed by Scanning Electron Microscope (SEM) images, results in greater chloride binding. Additionally, aluminum oxide in FA and GGBS enhances chemical binding by forming Friedel’s salt.

Effects of elevated temperature on mechanical properties and microstructures of alkali-activated mortar made from low calcium fly ash-calcium carbide residue mixture

This research investigated the high-temperature resistance of alkali-activated mortar (AAM) using Class F fly ash (FA) blended with calcium carbide residue (CR) as a binder. The FA was blended with CR at 15 %, 30 %, and 45 % by weight. Sodium hydroxide (NaOH) and sodium silicate solution (Na2SiO3) was used as activator in the ratio of 2:1 by weight. The sodium hydroxide solution concentrations were 6, 8, and 10 M, the liquid-to-binder ratio was 0.85, and the binder-to-fine aggregate ratio was 1:2.75 by weight. The study assessed physical characteristics, compressive strength, weight loss, and microstructural analysis, subsequent to being subjected to 2-hour heating at 400, 600, and 800 °C. According to the findings, the highest compressive strength (prior heating) was recorded as 41.3 MPa after 28 days and this was observed in samples where 30 % of CR was combined with 70 % of FA. Meanwhile, when exposed to elevated temperatures, the compressive strength of all samples was decreased. The decomposition of Ca(OH)2, C-S-H, and C-A-S-H gel in the matrix as indicated by the microstructure result was conformed to the result of compressive strength loss. Nonetheless, when the samples were sintered at 800 °C, a new crystalline phase was formed, resulting in a slightly increase in compressive strength compared to samples sintered at 600 °C.

Waste valorization: Sustainable geopolymer production using recycled glass and fly ash at ambient temperature

This research explores the reutilization of waste glass powder (GP) and class F fly ash (FA) in the development of an advanced geopolymer, focusing on reducing natural resource consumption to serve as a green alternative for conventional concrete material. Investigating mix ratios of GP-to-FA (0-to-1), activated with 2–12 M NaOH, followed by ambient temperature curing, this study mainly assesses strength (compressive, and flexural) and durability at different ages. Mechanical properties concerning reaction kinetics and Al/Si ratio, reveal that GP initially acts as an inert filler with slow reaction kinetics, while significant strength improvement at later ages is attributed to the reaction between GP and FA. Optimal performance is achieved with a geopolymer mixture featuring a GP-to-FA ratio of 1:3 (Al/Si ratio of 0.51) and an 8 M NaOH solution, resulting in the highest compressive strength of 40 MPa and superior durability. Microstructural analysis (SEM-EDS, and 29Si MAS NMR) identifies the reacting product as calcium/sodium aluminate silicate hydrate (C/N-(A)-S-H) gel within the geopolymer matrix. Leaching tests further underscore potential environmental concerns related to excessive alkali leaching, necessitating meticulous mix design management. Embodied energy and carbon footprint assessments confirm the environmental friendliness of the GP-FA-based geopolymer. Overall, this research demonstrates the feasibility of producing effective geopolymers from dry waste at ambient temperature, emphasizing the potential synergy between waste glass recycling and the concrete industry towards sustainable construction practices.

Induction furnace slag as fine and coarse aggregate in quaternary blended self-compacting concrete: A comprehensive study on durability and performance

This research explores the innovative use of Induction Furnace slag Aggregate (IF-slag) as both fine and coarse aggregates in Quaternary Blended Self-Compacting Concrete (QBSCC) mixes, an area that has received limited attention in previous studies. The primary aim is to compare the durability characteristics of QBSCC mixes containing natural aggregate versus those incorporating IF-slag aggregate. A total of 18 SCC mixes were prepared in two groups: one using natural aggregate and the other using IF-slag aggregate. Each group consisted of eight optimized QBSCC mixes alongside a reference SCC mix. The QBSCC mixes were formulated using Ordinary Portland Cement (OPC) with Supplementary Cementitious Materials (SCM) such as Silica Fume (SF), Class F-Fly Ash (FAF), and Ground Granulated Blast Furnace Slag (GGBFS). Previous work by the authors analysed the fresh and mechanical properties of these QBSCC mixes. This study assesses various durability properties, including water absorption, permeable pore volume, absorption coefficient sorptivity, ultrasonic pulse velocity, resistance to chloride ion penetration, electrical resistivity, and thermal conductivity. Experimental findings indicate that SCC prepared with IF-slag exhibited inferior durability performance compared to natural aggregate. However, regardless of aggregate type, QBSCC mixes outperformed the SCC mix containing 100% OPC. Notably, the SCC-47.5 (OPC)/52.5(SCM) QBSCC mix demonstrated significant improvements in durability properties, achieving a reduction of 25% in water absorption, 24% in permeable pore volume, 48% in absorption coefficient, and 46% in sorptivity. QBSCC mixes also exhibited resistance to chloride ion penetration and enhanced electrical resistivity. Moreover, using quaternary blends reduced the thermal conductivity and improved the energy efficiency.

Assessment of flexural response of RC beams and unrestrained shrinkage of fiber-reinforced high-volume fly ash-based no-aggregate concrete and self-compacting concrete

The use of industrial byproducts as a substitute for cement in concrete production to improve its properties is becoming a widespread practice in producing sustainable concrete. Although research around the world emphasizes higher substitution levels of fly ash (FA) to accrue the benefits from the microstructure refinement, no attempt has been made to study the deflection behavior and drying shrinkage of concrete that is devoid of aggregates while supplementing 80% of cement with class F fly ash (F-FA). Two types of concrete are used to cast full-scale reinforced concrete (RC) beams of size 150×300×2200 mm. The first type is a novel no aggregate concrete (NAC) made up of 80% F-FA and 20% ordinary Portland cement (OPC). The second type is high-volume fly ash self-compacting concrete (HVFASCC), which has 60% F-FA as a cement supplement and is equivalent in compressive strength to NAC. The NAC is reinforced with polypropylene fibers (PF) in three varying volume fractions: 0.6%, 0.8%, and 1.0%. All the beams are tested under a simply supported four-point loading condition. The drying shrinkage strain and mass loss are measured for prisms of size 75×75×300 mm up to 220 days exposed at 20% relative humidity (RH) and 50 ºC temperature in a humidity oven for all the mixes. The mechanical properties are also assessed along with the water absorption (sorptivity). The results indicate that adding PF to the beams with NAC delays the formation of the first crack and improves the peak load, the ultimate load, and the ductility of the NAC beam. Additionally, the beams with PF exhibit lower mid-span deflection and ductile failure mode, improving the overall structural performance. Regarding drying shrinkage, the HVFASCC prisms record the lowest shrinkage strains of all mixes. Adding PF to NAC increases the initial and ultimate drying shrinkage strains. However, adding PF to NAC inhibits the rate of shrinkage strain over the test duration. This research enhances understanding of how PF affects no-aggregate concrete behavior, paving the way for more comprehensive construction materials.

Improvement on engineering properties of alkali-activated paste with calcined oyster shell ash and flue gas desulfurisation gypsum

To reduce environmental pollution and conserve natural resources, calcined oyster shell ash (COSA), class F fly ash (FFA) and flue gas desulfurisation gypsum (FGDG) were used in an attempt to improve the engineering properties of alkali-activated ternary cementitious paste. The COSA – obtained by calcining crushed oyster shells at 800°C for 3 h and then grinding to pass through a no. 100 sieve – was used to substitute FFA at rates of 2.5, 5.0 and 7.5 mass%. The alkali solution used was 10M sodium hydroxide and sodium silicate with a modulus of 2.5. The hardened paste with 7.5% COSA, 1% FGDG and ratio of weight of added water to dry binder of 0.09 at 56 days had the highest compressive strength of 62 MPa. Microstructural analyses (scanning electron microscopy and energy-dispersive X-ray spectroscopy) showed that the resulting calcium aluminosilicate hydrate gel was found to have a compact microstructure, which improved the compressive strength of specimens. In summary, COSA successfully replaced natural limestone as a calcium oxide activator to manufacture an alkali-activated ternary cementitious paste containing FFA and FGDG.

Perlite incorporation for sedimentation reduction and improved properties of high-density geopolymer cement for oil well cementing

Portland cement (PC) is known for its environmental and technical concerns and massive energy consumption during manufacturing. Geopolymer cement is a promising technology to totally replace the use of PC in the oil and gas industry. Although geopolymers are widely used in the construction industry, it is yet to see a full-scale application in the petroleum industry. High-density geopolymer cement development is essential to substitute heavy-weight Portland cement slurries for high pressure well cementing applications. Sedimentation issue is associated with high-density cement slurries which use high specific gravity solids such as weighting materials. This problem causes heterogeneity and density variation along the cemented sections. The main target of this work is to evaluate the use of perlite powder to address the sedimentation issue in the heavy weight geopolymer systems. Hematite-based Class F fly ash (FFA) geopolymer cement slurries with perlite concentrations of 0, 1.5, and 3% by weight of binder (BWOB) were prepared. The sedimentation problem was investigated using three techniques: API method, nuclear magnetic resonance (NMR), and computed tomography (CT) scan. The perlite effects on different geopolymer properties such as unconfined compressive strength (UCS), porosity, elastic and rheological properties were assessed. The results proved that perlite incorporation in high-density hematite-based FFA geopolymer significantly reduced sedimentation issue by increasing yield point and gel strength. NMR and CT scan showed that perlite decreases porosity and density variation across the geopolymer samples. The UCS increased with increasing perlite percentage from 0 to 3%. The measured Young’s moduli (YM) and Poisson’s ratios (PR) showed that the developed perlite based geopolymer systems are considered more flexible than Class G cement systems. It was found that the optimum perlite concentration is 3% BWOB for tackling sedimentation and developing a slurry with acceptable mixability and rheological properties.

Thermo- mechanical and microstructural characterization of LECA and low carbon cement based lightweight mortar using box behnken design, and embodied energy analysis

Lightweight aggregate mortar (LWAM) containing different kinds of supplementary cementitious materials (SCMs) has gained significant attention as a sustainable construction material. However, the behavior of this type of mortar at elevated temperature conditions, such as those encountered in fire events, remains largely unexplored. In this study, the effect of different temperatures (i.e. at 27⁰C, 110⁰C and 850⁰C) on the Thermo-mechanical and microstructural properties of LWAM containing low grade limestone slurry (LgLS), class- F fly ash (FA), and lightweight expanded clay aggregate (LECA) is investigated. LgLS and FA were replaced with ordinary Portland cement (OPC) in the range of 0–20%, and 0–30% by weight. River sand was replaced with LECA, ranging from 0% to 50% with an increment of 25% in river sand fractions. Along with this, statistical modelling and parametric optimization were done using Box Behnken Design (BBD) of Response Surface Methodology (RSM). Advanced characterization techniques such as- Field Emission Scanning Electron Microscopy (FE-SEM) and X-ray Diffraction (XRD) were performed to investigate the effect of higher temperatures on the microstructure and hydration products of LWAM matrix. Embodied energy analysis was also carried out to investigate the environmental assessment along with cost analysis. It was concluded that as compared to the reference LWAM mix at 27 °C; CS at 28 days was increased by 15–25% at temperature of 110 °C for different mixes, while the same was drastically decreased by 60–64% at higher temperature i.e. 850 °C. Embodied energy analysis predicted that carbon emission can be minimized by about 25%, which is the need of the recent era to meet sustainable development goals.

Alkali-activated binder based on red mud with class F fly ash and ground granulated blast-furnace slag under ambient temperature

Abstract This study examined the fresh and hardened characteristics of alkali-activated binders (AABs) based on ternary mixtures of red mud (RM), class F fly ash (FA), and ground granulated blast-furnace slag (GGBFS). The binders were prepared by dry mixing of 50% RM, 25–50% FA, and 0–25% GGBFS. The alkali activators were prepared from sodium hydroxide solution with different concentrations (6–14 mol) and sodium silicate solution. Curing at room temperature was adopted for the preparation of all samples. The flowability, setting time, and compressive and flexural strength tests were used to examine the properties of the resulting binders. To study the microstructural characterization, the scanning electron microscope, X-ray diffraction, and Fourier transformation infrared techniques were used. The results show that the flowability of the AAB decreases with higher GGBFS content, the addition of GGBFS reduces the setting time, and the incorporation of GGBFS increases the flexural and compressive strengths of the AAB. Microstructural and chemical analysis results indicate that in addition to geopolymer gel, calcium silicate hydrate (C–S–H) is formed upon adding GGBFS, producing a denser microstructure.

Durability Assessment of Alkali-Activated Concrete Exposed to a Marine Environment

This study investigated the performance of two alkali-activated concretes (AACs) subjected to marine exposure for 2 years. The AACs were synthesized from a low-calcium Class F fly ash (FA) and a blast-furnace slag. Concrete specimens were exposed in a marine environment in a port facility in southern Australia for 2 years. The specimens were subject to a range of nondestructive testing (NDT) techniques, including resistivity, Schmidt hammer, and ultrasonic pulse velocity (UPV) tests. In addition, chloride diffusion coefficients were calculated from concrete cores taken from specimens exposed in the marine environment. Microscopy analysis was undertaken using Fourier-transform infrared (FT-IR), nuclear magnetic resonance (NMR), and thermogravimetric analysis (TGA), and comparative data were taken on laboratory specimens at 28 days. Furthermore, the chloride diffusion coefficients were compared with the results of standard laboratory tests undertaken on the control samples at 28 days, including rapid chloride permeability testing (RCPT) using a 10-V driving voltage, an NT Build 492 test, and a bulk diffusion test, to determine the relationship between the 28-day laboratory tests results and the site performance. The data showed good correlation between the predicted performance based on the 28 day laboratory tests and the 2-year site data. The chloride diffusion of the ground granulated blast-furnace slag (GGBS) concrete agreed very accurately with the predicted value from the modified RCPT test, whereas the performance of FA concrete was superior to that predicted.

Mechanical Properties of Fiber-Reinforced High-Volume Fly-Ash-Based Cement Composite—A Long-Term Study

This article presents the long-term mechanical properties of a novel cement composite, no-aggregate concrete (NAC), containing 80% of low-calcium (class F) fly ash (F-FA) and 20% ordinary Portland cement (OPC) without aggregates. The study investigates the effect of adding polypropylene fibers (PPFs) in varying volume fractions to NAC by conducting compressive, splitting tensile, flexural, bond strength, and sorptivity tests, emphasizing the morphological features over a curing duration of up to three years. The results indicate that adding PPF has an insignificant effect on compressive strength. However, flexural, splitting tensile, and bond strength improve with an increasing volume fraction of PPF. The addition of PPF achieves a ductile failure which is desirable. The initial and final water absorption rate (sorptivity) reduces with the addition of PPF. Further, scanning electron microscopy (SEM) images reveal dense precipitation of C-S-H, while energy-dispersive X-ray spectroscopy (EDS) quantifies the hydration products. The ultrasonic pulse velocity (UPV) affirms the composite’s excellent quality.

The Durability of High-Volume Fly Ash-Based Cement Composites with Synthetic Fibers in a Corrosive Environment: A Long-Term Study

The utilization of class F fly ash (F-FA) is limited to 15–30% as a substitution for cement. The study intends to tap into the potential of high-volume F-FA as a pozzolan and micro filler by eliminating aggregates. The article presents the long-term behavior of a novel cement composite called no-aggregate concrete (NAC), incorporating 20% ordinary Portland cement (OPC) and 80% F-FA, with polypropylene (PP) fibers in 0.6, 0.8, and 1.0% volume fractions, in a corrosive environment. The bulk diffusion of preconditioned 100 mm cubes reveals that all mixtures’ chloride-binding capacity increases significantly with prolonged exposure. The total chloride content for mixtures M1, M2, and M3 is within acceptable limits as per EN 206. M4 with 1.0% PP fibers shows a higher total chloride content at 2 cm depth. The average chloride content for all mixtures is within 0.4%. The compressive strength of mixtures cured in water is about 90 MPa at 730 days, and is severely affected in the absence of fibers in a corrosive environment. The microstructure of mixtures at 730 days displays a cohesive, compact, continuous matrix, and the presence of unreacted F-FA.

Comparative analysis of quaternary blended self-compacting concrete (QBSCC) mixes incorporating induction furnace slag (IFS) and crushed stone aggregate: A performance study

This study explores using Induction Furnace Slag (IFS) as aggregate in Quaternary Blended Self-Compacting Concrete (QBSCC) mixes. The experimental work consists of two stages. Stage I focuses on determining the optimal QBSCC mixes, aiming to develop environmentally friendly Self-Compacting Concrete (SCC) by utilizing different types and ratios of cementitious materials. A total of 27 QBSCC mixes were prepared with a reference SCC mix consisting of 100% ordinary Portland cement (OPC), are prepared considering water binder (w/b) ratio of 0.4. The quaternary blended mixes are created by combining OPC, class F Fly Ash (FA), Silica Fume (SF) and Ground Granulated Blast Furnace Slag (GGBFS). The replacement ranges for SF are set between 2.5% and 7.5% in increments of 2.5%, for FA between 10% and 20% in increments of 5%, and GGBFS between 30% and 50% in increments of 10%. In stage II, the optimized QBSCC mixes are further enhanced by incorporating IFS, the properties in the fresh state such as slump flow, V-funnel, L-box, and J-ring tests are conducted for all SCC mixes, all of which comply with the EFNARC guidelines. The mechanical characteristics studied, includes compressive strength (cube and cylinder), split tensile strength (at 3, 7, 28, and 56 days), flexural strength (at 28 and 56 days), elastic modulus, shear strength and pull-out bond strength (at 56 days) are evaluated. It is noted that the hardened properties of SCC mixes containing IFS exhibit slightly higher values compared to crushed stone aggregate SCC mixes. Furthermore, an increase in Supplementary Cementitious Material (SCM) content in QBSCC mixes leads to a decrease in the hardened properties, irrespective of the kind of aggregate used. The QBSCC mixes identified as SCC57.5/42.5, SCC52.5/47.5, and SCC47.5/52.5 are determined to be the preferred blends for producing Self-Compacting Concrete (SCC). Remarkably, Induction Furnace Slag (IFS) can be utilized as both fine and coarse aggregate, completely replacing conventional aggregates, regardless of the content of supplementary cementitious materials (SCM). This finding highlights the notable effectiveness of IFS as a replacement material in SCC production.

RETRACTED: A scientometric analysis on mechanical and microstructural characterization of geopolymer composites subjected to high temperatures

Class F fly ash (FA)-sourced geopolymers (GPM) are susceptible to different high-temperature phenomena, for instance, spalling, cracking, and thermal shrinkage. Protection of structural elements from fire is of great significance. These days, the construction industry is struggling to introduce sustainable binding composite materials to develop an eco-friendly environment due to the large carbon production during the manufacturing process of Portland cement. Therefore, the development of sustainable cementitious GPM is in the spotlight of the current research. The use of GPM as a substitute for Portland cement is the best replacement for sustainable development. A large number of review studies on the mechanical, durability, and microstructural features of GPM have already been performed; nevertheless, the influence of high temperatures up to 1000 °C on GPM and its exposure to fire still needs more exploration to check the suitability of GPM in the construction industry. In the present study, an extensive review of the mixing process, fresh behavior, curing conditions, shrinkage behavior, and thermal features of FA-sourced GPM subjected to fire conditions is performed. The effect of adding various alkali materials on the thermal features of GPM is elaborated. The phase formation, initial strength development, and melting temperature due to the involvement of minor elements are reviewed and deliberated. The pore interconnectivity to minimize the damaging behavior of GPM and the progression of ingredient features when the GPM is subjected to high temperature are also covered in the present study. The results of the studies presented that the potassium-sourced alkali materials depict a better thermal resistance of GPM. Concerning future works and recommendations, the reactive phases of GPM under high temperatures should be examined.

The effect of class F fly ash on the geopolymerization and compressive strength of lightweight aggregates made from alkali-activated mine tailings

Lightweight aggregates (LWAs) produced using alkaline activation of aluminosilicate-rich mine tailings (MTs) are viable substitutes for natural lightweight aggregates used in construction and building industry. However, most pure MTs do not contain adequate quantities of amorphous aluminosilicates to make geopolymerization feasible without adjusting the Si:Al ratio through the incorporation of amorphous aluminosilicates or other aluminum/silicon source materials. A comprehensive exploration of the production of LWAs using MTs in conjunction with reactive aluminosilicates has not yet been thoroughly investigated. In this study, class F fly ash (FA) was used as an amorphous supplement to adjust the Si:Al ratio, leading to improved geopolymerization of LWAs. The mixtures of MTs and FA were pelletized using a disk granulator machine by spraying 10 M NaOH with a liquid-to-solid ratio (L/S) of 0.25. The effects of different concentrations of FA (10%, 15%, 20%, 25%, and 30%) on the chemical, physical, mechanical, mineralogical, and morphological features of the resulting LWAs were examined. The results indicate that increasing the FA content of LWAs decreased their water absorption and porosity while increasing their bulk density and compressive strength without affecting their specific gravity. The scanning electron microscope (SEM-EDS) images show that by increasing the FA content, especially at 20% and upward, homogeneous geopolymerization was achieved in the specimens and the Si:Al ratio in LWAs with 20% or more FA was greater than three, indicating a greater likelihood of geopolymer backbone formation. The results of x-ray diffraction spectrometry (XRD) and Fourier-transform infrared spectroscopy (FTIR) showed that the alkali activation process resulted in the disappearance of the gypsum phase originally available in the MTs and the appearance of sodalite (sodium carbonate) in the LWAs. Future research should utilize the Life Cycle Assessment (LCA) methodology to evaluate environmental impact and should explore advanced additives/modifiers for improved mechanical characteristics and manufacturability to increase potential construction applications.

A hybrid model based on convolution neural network and long short-term memory for qualitative assessment of permeable and porous concrete

Estimating design factors like concrete strength and durability is complicated by the cement industry's practice of producing multiple grades of cement for different uses, necessitating substantial labor hours and monetary investment. The experimental findings of accelerated carbonation-induced corrosion and associated durability characteristics of concrete built with high-volume Class F Fly Ash (FA), including AC impendence, half-cell potential, water permeability, and volume of permeable voids. FA was added to ordinary portland cement at varied replacement amounts (0–70%) to create concrete specimens. The concrete specimen has been prepared by varying different proportions of water cement ratio (0.45, 0.40, and 0.35). To predict the compressive strength and carbonation level of concrete, this study presents a simulation environment based on Artificial Intelligence (AI) that makes use of input parameters such as water/cement ratio, fly-ash percentage, and time duration. Here, One-Dimensional Convolution Neural Network based Long Short-Term Memory (1D-CNN-LSTM) has been proposed for estimating the carbonation depth and compressive strength of concrete. The developed model will be compared with other state-of-the-art techniques, including DL and ML-based techniques. The obtained R2 values from the proposed 1D-CNN-LSTM regression network deliver accuracy of 80% for estimating carbonation depth and 96% for predicting compressive strength. The proposed methodology demonstrates the use of modern AI-based techniques in the actual design model and illustrates the development of DL methods such as LSTM and CNN.

Mix design development for geopolymer treated expansive subgrades using artificial neural network

Expansive soils have been inevitable during road constructions due to its widespread availability. Conventional stabilizers; cement and lime have not been quite reliable in terms of economic, environmental, and durability perspectives. Thus, geopolymer has come into limelight as a sustainable alternative. However, the complexity of geopolymer-soil behaviour makes it challenging to predict their strength development patterns and it requires a large number of trial and error tests in laboratory scale due to the soil specific nature of such mixes. To date, no research has been attempted to develop design charts for geopolymer-expansive soil stabilization field applications. This study proposes design charts using Artificial neural networks (ANN) to predict the 28-day unconfined compressive strength (UCS) of Class F fly ash (FA) based geopolymer stabilized expansive soil (PI = 32% – 46%) to support field implementation of this novel geopolymer based soil stabilization. The model was developed based on a robust collection of literature data; FA/Soil, Activator/FA, Na2SiO3/NaOH, alkaline molarity, and their respective 28-day UCS values. Three contour plots for mix design: FA/soil vs. NaOH molarity, activator/FA vs. Na2SiO3/NaOH, and Na2SiO3/NaOH vs. NaOH molarity were proposed based on the model predictions. The proposed mix design charts were validated through the in-house tests which showed reasonable match in comparison with the predicted 28-day UCS using the contour plots. The proposed mix design charts can be employed for in-situ geopolymer-expansive subgrade stabilization to achieve strengths between 0.6 and 2.1 MPa.

Properties of Engineered Cementitious Composites Using Combined Systems of Fly Ash and Post-Processed Bagasse Ash as Supplementary Cementitious Materials

This study assessed the viability of utilizing post-processed bagasse ash (PBA) along with Class F fly ash (FA) to partially replace cement in engineered cementitious composites (ECCs). Field-collected sugarcane bagasse ash was processed by sieving, burning, and grinding to produce PBA. Cement replacement with supplementary cementitious materials (SCMs) was kept constant at 60% (by mass) in all composites. However, the composition of the SCMs was varied as follows: (1) 100%FA as control; (2) 75%FA/25%PBA; (3) 50%FA/50%PBA; (4) 25%FA/75%PBA; and (5) 100%PBA. Fresh and hardened properties of the composites were evaluated through a flow table, uniaxial tensile tests, surface resistivity, and compressive strength. Furthermore, single-crack tensile tests were conducted to evaluate fiber-bridging properties, and fracture toughness tests were conducted to determine fracture toughness. Results showed that the incorporation of PBA decreased workability. Furthermore, using PBA produced a negligible impact on the compressive strength, yet significant improvements in surface resistivity. Whereas the tensile strain capacity of the composites decreased for PBA contents greater than 25%, the tensile strength was not significantly affected. The decrease in ductility was mainly attributed to the decrease in pseudo-strain-hardening performance indexes. Overall, results suggest that producing ECCs using combined systems of FA and PBA as partial cement replacement is feasible. Yet, achieving high ductility of the composites is challenging when utilizing high content of PBA (i.e., more than 25% of FA replaced with PBA by mass).

Amine Infused Fly Ash Grafted Acrylic Acid/Acrylamide Hydrogel for Carbon Dioxide (CO2) Adsorption and Its Kinetic Analysis.

In most carbon dioxide (CO2) capture processes, chemical absorption using an amine solvent is widely used technology; however, the solvent is prone to solvent degradation and solvent loss which leads to the formation of corrosion. This paper investigates the adsorption performance of amine-infused hydrogels (AIFHs) to increase carbon dioxide (CO2) capture by leveraging the potency of amine absorption and adsorption properties of class F fly ash (FA). The solution polymerization method was used to synthesize the FA-grafted acrylic acid/acrylamide hydrogel (FA-AAc/AAm), which was then immersed in monoethanolamine (MEA) to form amine infused hydrogels (AIHs). The prepared FA-AAc/AAm showed dense matrices morphology with no obvious pore at the dry state but capable of capturing up to 0.71 mol/g CO2 at 0.5 wt% FA content, 2 bar pressure, 30 °C reaction temperature, 60 L/min flow rate, and 30 wt% MEA contents. Cumulative adsorption capacity was calculated and Pseudo-first order kinetic model was used to investigate the CO2 adsorption kinetic at different parameters. Remarkably, this FA-AAc/AAm hydrogel is also capable of absorbing liquid activator that was 1000% more than its original weight. FA-AAc/AAm can be used as an alternative AIHs that employ FA waste to capture CO2 and minimize the GHG impact on the environment.

Synergy of retarders and superplasticizers for thickening time enhancement of hematite based fly ash geopolymers

Geopolymers are an evolving technology to replace ordinary Portland cement (OPC) in oil and gas industry. Geopolymers can be formed using aluminosilicate materials such as some waste and rock-based materials. Heavy weight geopolymers suffer from low thickening times especially at high temperatures. Thickening time is affected by downhole pressures and temperatures, the latter has the most significant effect. As downhole temperature increases, the cement slurry sets faster. Thickening time is a critical parameter for cementing operations to avoid risks of an early or a delayed setting. This study focuses on increasing thickening time of hematite-based class F fly ash (FFA) geopolymers at downhole temperatures. Firstly, the effect of hematite as a weighting agent on FFA geopolymer thickening time was investigated. Next, different combinations of retarders, dispersants and superplasticizers were tested to prolong the thickening time of hematite based FFA geopolymers. After that, the effects of the proposed mixture on the rheological and mechanical properties were assessed. The thickening time of the hematite based FFA geopolymer decreased from 430 to 80 min with increasing hematite from 25 to 75% by weight of binder (BWOB). For the 75% hematite geopolymer, a proposed mixture of a poly naphthalene sulfonate (PNS) superplasticizer and a modified lignosulfonate retarder increased the thickening time from 80 to 580 min at 195 °F. The proposed additives mixture developed a formulation with the highest unconfined compressive strength (UCS) and Poisson's ratio (PR) as compared to other formulations that use each additive separately. In addition, this mixture decreased the plastic viscosity of the high density geopolymer slurries by 29% which facilitates mixing and pumping. This study introduced a solution to thickening time and pumpability challenges associated with heavy weight fly ash geopolymers at high temperatures.