Fly Ash Class Research Articles

Balancing Sustainability and Strength: Analyzing the Effects of Textile, Tannery, and Water Treatment Sludge on Brick Performance

This study investigates the feasibility of incorporating various industrial waste materials, specifically textile sludge, tannery sludge, and water treatment plant sludge, in brick production as a sustainable construction practice. The research analyses the impact of varying sludge proportions on the compressive strength of fired clay bricks. Results indicate an inverse relationship between increasing sludge content and compressive strength across all types. Bricks incorporating higher proportions of textile sludge exhibited a linear decrease in compressive strength, ranging from 0.1 MPa to a low of 0.005 MPa. Similarly, increasing the ratio of tannery sludge to fly ash Class C and Ground Granulated Blast-furnace Slag within the brick mixture consistently corresponded with reduced compressive strength, with a 5:70:25 mix yielding 0.8 MPa and a 40:30:30 proportion resulting in 0.17 MPa. Water treatment plant sludge exhibited a similar trend. A mix proportion of 5:70:25 (sludge: fly ash class C: GGBS) yielded a compressive strength of 1.87 MPa while increasing the sludge proportion to 40:50:10 resulted in a lower compressive strength of 1.20 MPa. These findings underscore the importance of a balanced approach when incorporating industrial sledges in brick production. While beneficial from a sustainability perspective, the observed reduction in compressive strength, particularly compared to conventional clay bricks exceeding 2.5 MPa, necessitates careful consideration. Future research should focus on optimizing mix designs, incorporating performance-enhancing additives, or identifying applications where lower compressive strengths are acceptable to fully realize the potential of these waste materials in sustainable construction.

Comparative Study of Mechanical Properties of Self Compacting Concrete Using Binary Pozzolanic Materials

Abstract: The study examined the viability of using waste supplementary cementing materials (SCMs), such as fly ash (FA) and silica fume (SF), as partial replacement of Ordinary Portland cement. The way SCC's fresh properties and hardened were impacted by FA and SF. The study examined the fresh characteristics and hardened characteristics of various distinct SCC mixes using SCC with partial replacement of Ordinary Portland Cement with FA (class F) and SF. First, the cement was replaced by percentages in the mixes 0%, 10%, 15%, 20%, 25%, and 30% by FA and constant replacement of 10% by SF. Then cement was replaced by percentages in the mix with 25% FA constant and 4%, 6%, 8%, 10%, and 12% by SF. For every combination, the water/binder (w/b) ratio was set at 0.43. The EFNARC (Specification and Guidelines for Self-Compacting Concrete) standards were met by the slump flow, T50, and viscosity of the SCC. After 28 days of curing, the blend consisting of 65% PC, 25% FA, and 10% SF had a maximum compressive strength of 41.22 MPa which is 12.07% greater than the compressive strength of the control specimen which is 36.78 MPa. The Split Tensile Strength of the same blend is 4.37% is greater than the control specimen. Non-destructive tests were also performed after 28 days of curing and the regression equations give the excellent relationship between Rebound Number, Ultrasonic Pulse Velocity, and Compressive Strength. This is due to the formation of the proper matrix as the particle size of SF and FA is less than that of cement and the free lime of cement reacts with FA and SF to form C-S-H gel which provides strength.

Characterization and Properties of Binder and Nano-Filler in Geopolymer Paste with Graphene Oxide

Globally, current research has developed new cement-based materials to meet increased demands for performance, energy efficiency, and environmental protection. Geopolymer, cost-effective, and high-early strength concrete binder alternative, has grown in popularity. Geopolymer reduces emissions by 80% during production while maintaining strength levels comparable to Ordinary Portland Cement (OPC). In their natural state, geopolymer binders have a microstructure that is cross-linked and significantly more brittle than OPC. To improve the properties of geopolymer, several approaches were adopted. However, recent study suggests that incorporating nanomaterials such as graphene oxide (GO) to geopolymer has shown an improvement in physical and mechanical properties. Graphene oxide is an inorganic nanomaterial that improves the mechanical characteristics of various composite materials by showing substantial filling effects on composite materials that significantly improve composite material integrity. The investigation into the potential of GO to improve the efficacy of geopolymer composite materials in various engineering applications has garnered considerable attention in recent years. The simplified hummer’s method was employed to synthesise the GO. Various characterization techniques involving SEM, XRD, and FTIR were utilized to understand the crystalline structure and microstructure of GO nanoparticles. GO powder were used as 0.05%, 0.10%, 0.15%, 0.20%, and 0.25% by weight of binder that includes fly ash class F and steel slag with an optimum binder modification of 40% fly ash and 60% steel slag. The influence of GO on Bulk density, microstructure, and mechanical strength were determined. The compressive strength results indicated an improvement of compressive strength by 21.48% in geopolymer paste with 0.15% GO after 28 days of curing.

UTILIZATION OF HIGH-VOLUME FLY ASH AS A SUPPLEMENTARY CEMENTITIOUS MATERIAL IN ENVIRONMENTALLY FRIENDLY CONCRETE

Innovations in material technology are expected to reduce the use of commercial cement and replace it with other environmentally friendly materials with the same performance as normal concrete. Aim: This study aim to analyze the mechanical property of High-Volume Fly Ash Concrete (HVFAC) using F class fly ash with different mix percentages. Methodology and Results: The experiment was conducted in laboratory scale. Four variations of test specimens consisted of: 1 variation (F0), which is conventional concrete with 100% Portland cement as control specimen, and three variations of HVFC (F70, F80, and F90), which were made with fly ash content (%) 70, 80, and 90 of total cementitious. Fresh concrete testing to determine workability, while hard concrete testing is done by density and compressive strength tests at the age of 3, 7, and 28 days on specimens that have been treated with the water submerged curing method. Conclusion, significance, and impact of study: All HVFAC specimens fulfill the Self Compacting Concrete (SCC) category. The compressive strength test results at 28 days showed that the addition of fly ash percentage caused a decrease in compressive strength values in all HVFAC variants, but still exceeded the minimum requirements of high and medium quality concrete. All HVFAC variations meet the requirements of ASTM C618-23 based on the evaluation of Strength Activity Index (SAI) values at 7 and 28 days of age. The utilization of 90% fly ash as a cement substitute resulted in an environmentally friendly concrete product based on the concept of cleaner production.

Enhancing Thermomechanical Strength and Thermal Stability of Poly(dicyclopentadiene) Composites through Cost-Effective Fly Ash Reinforcement for Structural and Impact Applications.

Poly(dicyclopentadiene) (poly-DCPD) is a thermoset with potential for high-performance applications. In this research, epoxy resin was blended with different concentrations of fly ash class F particles at 0.0, 1.0, 10.0, and 50.0 wt.%, aiming to improve its use as a high-volume structural material by decreasing costs and reducing its negative environmental impact through using fly ash particles. A planetary Thinky mixer was used to initially mix the resin with the curing agent, followed by incorporating a Grubbs catalyst. The microstructures were analyzed using scanning electron microscopy (SEM), where particles were found to be homogeneously distributed over the polymer matrix. The thermomechanical behavior was evaluated via curing, compression, dynamic mechanical analysis (DMA), and thermo-gravimetric analysis (TGA). Nanoindentation tests were also conducted. Fly ash was found to decelerate the curing of the resin through the release of calcium ions that enhanced the exothermic reaction.

Shrinkage, Permeation and Freeze-Thaw Characteristics of Ambient Cured High Calcium-Based Alkali-Activated Engineered Composites.

Sustainable zero cement-based one-part ambient cured alkali-activated engineered composites (AAECs) are developed. The durability and microstructural characteristics of developed AAECs using 2% v/v polyvinyl alcohol (PVA) fibers, silica sand, binary or ternary combinations of precursors (fly ash class C 'FA-C', fly ash class F 'FA-F' and ground granulated blast furnace slag 'GGBFS') and two types of powder form alkaline reagents (Type 1 and Type 2) are evaluated compared to conventional engineered cementitious composites (ECCs) and alkali-activated mortars (AAMs) without fiber. AAECs developed satisfactory compressive strength ranging from 34 MPa to 46 MPa. Expansion/shrinkage and mass change (loss/gain) behaviors are affected by binary/ternary combination of source materials, reagent types and curing regimes (water or ambient) for both AAMs and AAECs. The binary (FA-C + GGBFS) and reagent 2 (calcium hydroxide + sodium sulfate) composites demonstrated lower shrinkage due to formation of crystalline C-A-S-H/C-S-H binding phases than their ternary (FA-C + FA-F + GGBFS) and reagent 1 (calcium hydroxide + sodium metasilicate) counterparts which formed amorphous N-C-A-S-H/N-A-S-H phases. The matrix densification due to the formation of reaction products and fiber-induced micro-confinement leads to lower shrinkage and mass change of AAECs compared to their AAM counterparts. Composites exhibited lower or comparable secondary sorptivity indices compared to control ECC, indicating their superior permeation performance. All AAECs had a relative dynamic modulus of elasticity (RDME) greater than 90% at 300 cycles (comparable to control ECC), exhibiting satisfactory freeze-thaw resistance with reagent 2 mixes showing better performance compared to those with reagent 1. The production feasibility of strain hardening AAECs with powder form reagents having satisfactory mechanical and durability properties is confirmed.

The Strength and Fracture Characteristics of One-Part Strain-Hardening Green Alkali-Activated Engineered Composites.

Alkali-activated engineered composites (AAECs) are cement-free composites developed using alkali activation technology, which exhibit strain hardening and multiple micro-cracking like conventional engineered cementitious composites (ECCs). Such AAECs are developed in this study by incorporating 2% v/v polyvinyl alcohol (PVA) fibers into alkali-activated mortars (AAMs) produced using binary/ternary combinations of fly ash class C (FA-C), fly ash class F (FA-F), and ground-granulated blast furnace slag (GGBFS) with powder-form alkaline reagents and silica sand through a one-part mixing method under ambient curing conditions. The mechanical and microstructural characteristics of eight AAECs are investigated to characterize their strain-hardening performance based on existing (stress and energy indices) and newly developed tensile/flexural ductility indices. The binary (FA-C + GGBFS) AAECs obtained higher compressive strengths (between 48 MPa and 52 MPa) and ultrasonic pulse velocities (between 3358 m/s and 3947 m/s) than their ternary (FA-C + FA-F + GGBFS) counterparts. The ternary AAECs obtained a higher fracture energy than their binary counterparts. The AAECs incorporating reagent 2 (Ca(OH)2: Na2SO4 = 2.5:1) obtained a greater fracture energy and compressive strengths than their counterparts with reagent 1 (Ca(OH)2: Na2SiO3.5H2O = 1:2.5), due to additional C-S-H gel formation, which increased their energy absorption for crack propagation through superior multiple-cracking behavior. A lower fracture and crack-tip toughness facilitated the development of enhanced flexural strength characteristics with higher flexural strengths (ranging from 5.3 MPa to 11.3 MPa) and a higher energy ductility of the binary AAMs compared to their ternary counterparts. The tensile stress relaxation process was relatively gradual in the binary AAECs, owing to the formation of a more uniform combination of reaction products (C-S-H/C-A-S-H) rather than a blend of amorphous (N-C-A-S-H/N-A-S-H) and crystalline (C-A-S-H/C-S-H) binding phases in the case of the ternary AAECs. All the AAECs demonstrated tensile strain-hardening characteristics at 28 days, with significant improvements from 28% to 100% in the maximum bridging stresses for mixes incorporating 40% to 45% GGBFS at 365 days. This study confirmed the viability of producing green cement-free strain-hardening alkali-activated composites with powder-form reagents, with satisfactory mechanical characteristics under ambient conditions.

Synthesis and characterization of amorphous nano silica from South African coal fly ash

In this study, amorphous silica nanoparticle was extracted from South African coal fly ash (SACFA), using a facile sol–gel synthesis method. Prepared amorphous silica nanoparticles (ASNPs) were characterized employing X-ray fluorescence (XRF) spectroscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), transition electron microscope (TEM), Brauer Emmett Teller (SBET) surface area analysis, and ultraviolet–visible diffuse reflection spectroscopy (UV–vis DRS). XRF analysis suggests SACFA as fly ash class F. the XRD pattern, reveals the structural compositing of SACFA and the amorphous nature of extracted SNP, while the FTIR assay shows the presence of silanol and siloxane groups. SEM and TEM analysis revealed primary silica nanoparticles were roughly spherical with sizes of about 98 nm. EDX spectral confirms the presence of SiO2. The findings of this study demonstrate a simple sol–gel method of synthesizing amorphous nano silica from SACFA, thus suggesting the utilization of SACFA in high-tech and complex material preparation and applications in a more inventive manner.

Effect of Bamboo Leaf Ash on The Properties of Geopolymer Concrete at Ambient Curing Temperature

As a result of the growing environmental concerns in the cement industry and the rising cost of building materials, alternative cement technologies have become an area of increasing interest. In this study, geopolymer concrete containing fly ash class F and bamboo leaf ash was chosen as a cement substitute in concrete manufacturing. This research was an experimental study evaluating the effect of bamboo leaf ash (BLA) on geopolymer concrete by addition as a partial replacement of fly ash. The test samples were 100 x 100 x 100 mm cubes and 300 x 150 mm cylinders at the ambient curing temperature. The design mix of C25 was used for this study. This research aimed to explore the suitability of the use of bamboo leaf ash as a mixing material in geopolymer concrete in more environmentally friendly industries. The properties that were investigated in this study are the basic aggregate tests, XRF analyses of BLA and fly ash, and workability tests by evaluating slump and compaction factor tests. In addition, compressive strength and splitting tensile strength of 28, 56, and 90 days. Therefore, in this study, various levels of bamboo leaf ash were utilized, including 0%, 5%, 10%, 15%, and 20% BLA. The alkaline liquid-to-binder ratio for all mixes was constant at 0.6, while the Na2SiO3 to NaOH ratio was 2.5. The test results of the workability show that the increased amount of bamboo leaf ash gradually reduces the alkaline liquid. The result of compressive and splitting tensile showed that fly ash substitutes that contained 5% and 10% of the bamboo leaf had higher strengths of about 38.7 MPa, 40.8 MPa, 4 MPa, and 4.22 MPa, respectively than other mixtures. Therefore, bamboo leaf ash can be one of the constituent materials used to improve the mechanical properties of geopolymer concrete

Strength behavior of green concrete by using fly ash and silica fume

Fly ash and silica fume, when used properly, improve the mechanical and durability properties of concrete. Some specialists have recently raised concerns about the fly ash and silica-fume concrete's long-term compressive strength. In this investigation, high calcium fly ash from the NLC Neyveli, which is more cementitious and pozzolanic, is used. If pozzolanic material ingests the extra calcium from C class fly ash, a better outcome may be anticipated. Researchers have studied this effect by substituting silica fume. The rate of strength property gains up to 56 days of curing was determined for conventional concrete (CC), fly ash concrete (FAC), silica fume concrete (SFC), and fly ash silica fume concrete (FASFC), with and without superplasticizer. A study on replacing 50% of the cement weight with fly ash and another 20% of the fly ash weight with silica fume in standard M30 grade concrete was done (SP). It has been established that strengthening cement concrete with fly ash, silica fume, and superplasticizer.

Carbon Emissions Assessment Fly ash and Steel Slag As a Substitute for Cement in Concrete Mixing Using the Method Artificial Neural Networks

Concrete is a construction material made from a mixture of Portland cement, air, coarse aggregate, fine aggregate, and sometimes also uses admixture materials with a certain ratio. Cement, which is the binding agent in the concrete mixture, contributes to 8% of the world's carbon dioxide (CO2) emissions. Fly ash and steel slag are one of the wastes that are currently being researched and developed as cement ingredients in concrete mixtures. This is because the chemical composition of fly ash and slag associated with cement is very suitable when added to concrete mixtures.This study aims to find out of the optimal of fly ash and slag content in the concrete mixture in terms of strength by using the Artificial Neural Network (ANN) method and in accordance with SNI 7656: 2012. Furthermore, this study also aims to measure the ratio of CO2 emissions that are produced from normal concrete, concrete with fly ash, and concrete with steel slag, using references from Idemat2014 and Ecoinvent V3.The results showed that the optimum content of fly ash class F, fly ash class C, and steel slag in the concrete mixture were 30%, 20%, and 55%, respectively. The results also concluded that steel concrete slag as the lowest emitter of CO2 compared to normal concrete, class F fly ash concrete, and class C fly ash concrete. Keywords: concrete, fly ash, steel slag, ANN, comppresive strength, CO2 emission

Analysis of the Impact of Fly Ash on Environmental Pollution (Case Study of Pulp and Paper Pangkalan Kerinci)

The accumulation of fly ash in large quantities will cause problems for the environment, such as air and water pollution and a decrease in the quality of ecosystems containing Ni, V, As, Be, Cd, Ba, Cr, Cu, Mo, Zn, Pb, Se and Ra which can affect groundwater quality and human health. This study aims to analyze the impact of waste generated from the Pulp and Paper on the environment around the industry. The data obtained is in the form of primary data from the results of the Toxicity Characteristic Leaching Procedure (TCLP) test and direct observation in the field to identify environmental conditions around the landfill, while TLCP laboratory analysis was carried out to determine the toxic characteristics of TLCP in fly ash from the Pulp and Paper BaseKerinci. The TCLP test results for fly ash the analyzed waste Fly ash produced from the pulp and paper is suitable for use with fly ash class F2+A12O3+Fe2O3 content of 75.19%. Utilization of fly ash can be an effort to reduce the impact of fly ash on environmental pollution. The waste produced by pulp and paper obtains a metal value below the quality standard so that it does not have a negative impact on the surrounding environment.

Compressive and Flexural Strength of High-Volume Fly Ash Mortars Aged with Air-entraining Admixtures

This paper presents the findings of an investigation into the compressive and flexural strength of various cement mortars containing very high levels of Class F fly ash (HVFA). A total of twelve cement mortar mixtures with constant water/powder ratios, cement, sand, and Air-Entraining Admixtures (AEA) were subjected to 20, 30, 40, 50, 60, and 70% partial replacement of cement content with Fly Ash (HVFA) class F. The results of the tests show that the compressive and flexural strength decreased slowly as the fly ash content increased to up to 40%, but the strength values began to decrease dramatically with the addition of a higher amount of fly ash. According to the results, the best percentage of cement replacement with fly ash in mortar is 40%. It has 24% less compressive strength and 13% less flexural strength than 20% FA mortar. In general, the air-entraining admixture has no negative effect on the properties of the cement mortars. The measured properties of the hardened mortar are very satisfying.

The Effect of Nano-Silica and Nano-Alumina with Polypropylene Fiber on the Chemical Resistance of Alkali-Activated Mortar

This study investigates the simultaneous effect of nano-silica and nano-alumina with and without polypropylene fiber on the chemical-resistant of alkali-activator mortar (AAM) exposed to (5% Sulfuric Acid, 5% Magnesium Sulphate, and 3.5% Sodium chloride) attack. Design-expert software provided the central composite design (CCD) for mixed proportions. Nano-silica (NS) and nano-alumina (NA) at 0, 1%, and 2%, and with polypropylene fiber (0, 0.5%, and 1%) were used in the production of AAM. The alkali activator mortar mixes were created using an alkaline activator to binder ratio of 0.5. The binder materials include 50% fly ash Class F (FA) and 50% ground granulated blast furnace slag (GGBS). A sodium silicate solution (Na2SiO3) and sodium hydroxide solution (NaOH) were combined in the alkaline activator at a ratio of 2.5 (Na2SiO3/NaOH). The mechanical properties of AAM were tested via compressive strength and flexural strength tests. The results show that the acid attack, more than the sulphate and chloride attacks, significantly influenced the AAM. The addition of both nanomaterials improved the mechanical properties and chemical resistance. The use of nanomaterials with PPF showed a superior effect, and the best results were indicated through the use of 2%NA–1%PPF.

Facile Preparation and Characterization of Silica Nanoparticles from South Africa Fly Ash Using a Sol–Gel Hydrothermal Method

Silica nanoparticles (SNPs) consist of several applications which include lightweight aggregates, energy storage, and drug delivery. Nevertheless, the silica reagents used in SNP synthesis are both costly and hazardous. As a result, it is critical to look for other sources of silica. For this research, a simple sol–gel hydrothermal approach is used to make SNPs from South African fly ash (SAFA). SAFA is classified as fly ash class F according to X-ray fluorescence (XRF) analysis. The wide-angle X-ray diffraction (XRD) pattern reveals the structural composition of SAFA and the amorphous phase of extracted SNPs, while Fourier transform infrared (FTIR) examination reveals the presence of silanol and siloxane groups. Basic SNPs were generally spherical with diameters of about 60 nm, according to scanning electron microscopy (SEM) and transition electron microscope (TEM) studies. The presence of SiO2 is confirmed by energy-dispersive X-ray spectroscopy (EDX) spectrum analysis. Particle size assessment indicates particle sizes ranging from 48 nm to 87 nm in diameter, with a mean diameter of 67 nm. The application of SNPs in wastewater treatment demonstrated that they can be used to remove Cd2+ from an aqueous solution. This research offers new ideas for using South African fly ash in SNP manufacturing.

An Emphasis Study on Residual Engineering Properties of Fly Ash Concrete Elevated Temperature

The paper examines the properties of fly ash as partial cement replacement in normal strength concrete at ambient and elevated temperature. The properties of fly ash class F was chemically investigated. Behaviour of concrete containing fly ash subjected to elevated temperature 200 ºC up to 600 ºC at temperature rate of 2.78 ºC/min is investigated mechanically and microstructurally. Physically, fly ash concrete changed colour to brown at 400 ºC and to whitish grey at 600 ºC, which is similar to normal concrete. At 600 ºC, the residual compressive strength of fly ash concrete was slightly higher than normal concrete with a strength reduction of 13.18% and 45.22%, respectively. At 400 ºC, fly ash concrete has better splitting tensile strength than normal concrete with strength reduction of 28.81% and 43.26%, respectively. Thus, the use of fly ash as cement replacement in fly ash concrete improves concrete performance after exposed to elevated temperatures. Based on Field Emission Scanning Electron Microscopy (FESEM) and Energy Dispersive X-Ray (EDX), fly ash concrete performed better thermally proven by the formation of ettringite. In conclusion, the utilization of fly ash as a replacement for Ordinary Portland cement (OPC) at elevated temperatures is a good innovation for concrete performance.

Microwave-assisted sol–gel template-free synthesis and characterization of silica nanoparticles obtained from South African coal fly ash

Abstract In this study, we prepared a silica nanoparticle from South African fly ash (SAFA), using a facile microwave (MW)-assisted sol–gel template free syntheses method. Prepared silica nanoparticles (SNPMW) were characterized using X-ray fluorescence (XRF) spectroscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), transition electron microscope (TEM), Brunauer–Emmett–Teller (S BET) surface area analysis, and ultraviolet visible diffuse reflection spectroscopy. XRF analysis suggests SAFA as fly ash class F. The XRD pattern reveals the structural composition of SAFA and the amorphous nature of extracted SNP, while the FTIR assay shows the presence of silanol and siloxane groups. SEM and TEM analyses revealed primary silica nanoparticles were roughly spherical with sizes of about <200 nm. EDX spectra confirm the presence of SiO2. The optical bandgap of SNPMW was established to be 4.67 eV. The application of SNPMW demonstrated that it can be used to remove Pb2+ from an aqueous solution. Test results show the optimum treatment time as 60 minutes, while removal efficiency increases from 66.76 to 96.64% as the pH rises from 3 to 5, but as the pH rises above 5, the efficiency decreases. The use of an MW-assisted sol–gel preparation method gave rise to an elevated reaction rate with minimal contamination and thinner particle size SNPMW, which was utilized for the removal of Pb2+ in an aqueous solution.

Influence of Mixing Order on the Synthesis of Geopolymer Concrete.

Geopolymers are high-performance, cost-effective materials made from industrial waste that ideally fit the needs of 3D printing technology used in construction. The novelty of the present work lies in the investigation of methods to mix geopolymer concrete from fly ash (FA) class F, ground granulated blast furnace slag (GGBS), and raw calcined kaolin clay (RCKC) to determine the mixing procedure which provides the best mechanical strength and structural integrity. The experimental results show that aluminosilicates with different reaction parameters when mixed one after another provide the optimal results while the geopolymer concrete possesses the highest compressive strength and the denser structure. The results demonstrated that the reactivity of GGBS, FA, and RCKC increased for different depolymerization speeds of the selected aluminosilicates. This research will provide results on how to improve the mixing order for geopolymer synthesis for 3D printing demands. The highest compressive strength and denser structure of geopolymer concrete is achieved when each type of aluminosilicate is mixed with an alkaline medium separately.

The impact of CO2 uptake rate on the environmental performance of cementitious composites: A new dynamic Global Warming Potential analysis

The sustainability of cementitious composites is currently analyzed by static methods, with little consideration of changes over time. In terms of Global Warming Potential (GWP), increasing the CO2 concentration in the atmosphere may negatively affect the planet. Therefore, estimating the imbalance between CO2 emitted and CO2 captured by these materials may be critical when assessing their environmental performance. This is the first study that proposes a new dynamic GWP method to analyze the sustainability of materials with the ability to uptake CO2 during their service life. For that, three main concrete mixtures are assessed: (i) a reference concrete with 100% Ordinary Portland cement (OPC); (ii) a concrete with 25% Fly Ash Class C (FA) + 75% OPC; and (iii) a concrete with 40% Ground Granulated Blast Furnace Slag (GGBFS) + 60% OPC. The investigation quantifies the GWP associated over a 100-year timeframe of a concrete mixture made at year 0 and based on four different CO2 uptake rates (reference, nano-modified A and B, and CO2 curing). Results demonstrate that while CO2-cured concretes exhibit the lowest GWP at year 0, nano-modified A concretes possess the lowest GWP associated at year 100 due to the acceleration of the CO2 uptake during their lifetime. Results also reveal that the GWP of nano-modified and CO2-cured concretes will be overestimated if the effects over time are not considered. Therefore, the dynamic methodology presented in this study should be employed when quantifying their GWP in cementitious composites. Moreover, this dynamic analysis could also be applied to other impact categories or even the complete holistic life cycle assessment.

Mix Design Formulation and Stress-Strain Relationship of Fly Ash-Based Workable Geopolymer Concrete: an Experimental Study

Geopolymer concrete is known as a concrete made by one of cementitious materials in order to reduce carbon dioxide (CO2) emissions for sustainable development purposes. Instead of using Portland cement for a mortar matrix, mineral residues as a result of power plant processes so-called fly ash are used to replace completely the existence of cement in a concrete structure. A large amount of chemical compounds such as silicon dioxide or silica (SiO2), aluminum oxide (Al2O3) and iron(III) oxide or ferric oxide (Fe2O3) contained in fly ash can substitute Portland cement as a chemical binder in concrete materials. Fly ash Class F which contains more than 70% of SiO2, Al2O3 and Fe2O3 in total with less than 10% of calcium oxide (CaO) has been investigated yielding compressive strengths similar to or even higher than the conventional concrete using Portland cement. In order to obtain a strong chemical binder between aggregates and fly ash, an activator containing a mixture of sodium hydroxide (NaOH) and sodium metasilicate (Na2SiO3) is applied here, where two types of Na2SiO3 (Be52 and Be58) are employed. Further, workability is investigated by comparing Na2SiO3 type Be52 and Na2SiO3 type Be58, with maintaining an acceptable compressive strength. Then the results of proportional mix design variations for geopolymer concrete are analyzed in terms of the modulus of elasticity and the Poisson’s ratio as well as its stress-strain relationship compared to the conventional concrete.