Sodium Silicate Research Articles

Utilization of Egyptian kaolinitic sandstone rocks for production of ecofriendly green building materials

ABSTRACT Nowadays, geopolymers are considered as an environmentally friendly construction material and a substitute for Ordinary Portland cement (OPC) with the aim of decreasing CO2 emissions. The present study utilizes natural kaolinitic sandstone rock and water-cooled slag as precursor components, with sodium silicate and sodium hydroxide acting as alkali activators. The different percentages of substituting natural kaolinitic sandstone with water-cooled slag are 0%, 20%, 40%, 60%, 80% and 100%. Six mixes were prepared and subjected to a curing regime of 90 days under conditions of 100% relative humidity. FTIR, SEM imaging, XRD, and compressive strength testing were evaluated. The results show that increasing the slag content by up to 40% improves the mechanical properties of the prepared mixes compared to the control mix, with curing times of up to 90 days. As a result, when kaolinitic sandstone is replaced by up to 40% slag, its compressive strength values increase 266.55% compared to the control mix and can therefore be used for the production of geopolymer materials for general and special purposes with high requirements. Based on the results, it was concluded that geopolymers can be considered as a potential alternative to OPC that possesses similar or better structural and mechanical properties.

3D-печать текстиль-бетонных конструкций

A paper proposes the technological solution for the use of textile reinforcement with the additive technologies in the construction. This solution involves the preliminary manufacture of reinforcing frames. Those are the textile reinforcing net made of an alkali-resistant basic knitted fiberglass with an integrated layer of wall insulation. The treatment of reinforcing net with liquid glass increases the strength characteristics of the resulting composite – textile reinforced concrete. The technology consists in spreading of the prepared frames on the printed structure as a nozzle of 3D printer moves. The use of reinforcing net allows ones to reduce the manual labour costs for the connection of the external and internal surfaces of the printed wall, makes it possible to embed heat-insulating material into the wall under construction in the printing process. Moreover, the technology reduces the requirements for the concrete mix, since the reinforcing net acts as a formwork and prevents spreading during printing.

Graphene Mitigates Nanoscale Tribochemical Wear of Silica Glass in Water

AbstractDespite the ubiquitous use of glasses, their simultaneous susceptibility toward scratch‐induced defects and atmospheric hydration deteriorates their mechanical and chemical durability. Here, it is demonstrated that the deposition of a few‐layer graphene provides unprecedented wear resistance to silica glass in aqueous conditions. To this extent, nanoscale scratch tests are carried out on graphene‐glass surfaces via contact‐mode atomic force microscopy with chemically inert and reactive tips. It is observed that the graphene‐glass exhibits up to ≈98% friction reduction and no discernable damage or material loss. This observation is in stark contrast to the behavior of bare silica glass which suffers severe tribochemical wear at equivalent contact conditions with even milder stresses. Further, through reactive molecular simulations, it is demonstrated that parallel mechanisms of lubrication and chemical passivity contribute to the enhanced damage resistance of graphene‐glass surfaces against any countersurface chemistry. Altogether, the present study provides an impetus toward physically and chemically durable glass coatings exploiting the functionalities of two‐dimensional materials.

Iron redox effect on the structure and viscosity of a sodium silicate glass and melt

The viscosity of silicate melts is one of the most important physical properties for understanding high-temperature phenomena in magmatic systems and material processing. The effects of composition and temperature on viscosity have long been elucidated. Although iron ions are the main components of magmatic systems, their influence on viscosity remains unclear because the behavior of iron is complicated; iron ions have two redox states, Fe3+ and Fe2+. Here, we elucidate the viscosity of an iron-sodium-silicate system with a variety of iron redox states at temperatures close to its glass transition temperature (Tg). The redox states and structures of the samples were characterized using x-ray absorption near-edge structure (XANES) spectroscopy, Raman spectroscopy, synchrotron x-ray total scattering, and density (molar volume) measurements. The viscosity increased (by more than four orders of magnitude) with an increase in the ratio of Fe3+ to total Fe (Fe3+/Fetot), whereas the temperature dependence of the viscosity was larger for glasses with a higher Fe3+/Fetot ratio at temperatures close to the glass transition temperature. The tendencies in viscosity and structural variation against the Fe3+/Fetot ratio support the consensus on the structural roles of Fe3+ and Fe2+ from previous studies: Fe3+ ions have a stronger tendency to behave as network formers than Fe2+ ions.

Distinct deformation mechanisms of silicate glasses under nanoindentation: The critical role of structure

We use large-scale molecular dynamics simulations to investigate the indentation response of three silica-based glasses with varying compositional complexities. Our primary goal is to clarify the roles of the typical network-modifying species, namely, sodium, and the secondary network-forming species, namely, boron, in influencing the mechanical behavior of the glasses under localized stress. The distinct mechanical responses of the glasses are linked to structural features such as bond strength, network connectivity, and atomic packing density. The enhanced nanoscale ductility of sodium silicate and sodium borosilicate glasses, compared to silica, is attributed to the structural flexibility induced by Na atoms, which depolymerize the network, and by B species in mixed coordination. We also find that shear flow, driven by network flexibility, is the dominant deformation mechanism in the sodium silicate and sodium borosilicate glasses, while densification dominates in silica due to its low packing density. The evolution of short-to-intermediate-range structures is responsible for the distinct deformation behaviors of the glasses. These results highlight the critical role of structure in determining the deformation mechanisms of silicate glasses under sharp contact loads, providing insights for improving the mechanical performance of these materials.

Nanodots of Transition Metal Sulfides, Carbonates, and Oxides Obtained Through Spontaneous Co-Precipitation with Silica.

The controlled formation and stabilization of nanoparticles is of fundamental relevance for materials science and key to many modern technologies. Common synthetic strategies to arrest growth at small sizes and prevent undesired particle agglomeration often rely on the use of organic additives and require non-aqueous media and/or high temperatures, all of which appear critical with respect to production costs, safety, and sustainability. In the present work, we demonstrate a simple one-pot process in water under ambient conditions that can produce particles of various transition metal carbonates and sulfides with sizes of only a few nanometers embedded in a silica shell, similar to particles derived from more elaborate synthesis routes, like the sol-gel process. To this end, solutions of soluble salts of metal cations (e.g., chlorides) and the respective anions (e.g., sodium carbonate or sulfide) are mixed in the presence of different amounts of sodium silicate at elevated pH levels. Upon mixing, metal carbonate/sulfide particles nucleate, and their subsequent growth causes a sensible decrease of pH in the vicinity. Dissolved silicate species respond to this local acidification by condensation reactions, which eventually lead to the formation of amorphous silica layers that encapsulate the metal carbonate/sulfide cores and, thus, effectively inhibit any further growth. The as-obtained carbonate nanodots can readily be converted into the corresponding metal oxides by secondary thermal treatment, during which their nanometric size is maintained. Although the described method clearly requires optimization towards actual applications, the results of this study highlight the potential of bottom-up self-assembly for the synthesis of functional nanoparticles at mild conditions.

Reactionary powder concrete based on alkali-activated cement

The development of reactive powder concretes based on alkali-activated cements for the construction and protection of critical infrastructure is of woldwide importance for improving the safety of their exploitation. The factors influencing the kinetics of strength gain and drying shrinkage of reactive powder concretes using sodium silicate pentahydrate as an alkaline activator were determined.It was shown that increasing the ratio of alkali-activated cement to sand from 1:3 to 1:1 and using the activator in the liquid state increased the concrete strength gain: the compressive strength was 52.3 MPa, 85.0 MPa, 100.6 MPa, and 124.7 MPa at the ages of 1, 3, 28, and 90 days of hardening, respectively. The ratio of compressive strength to flexural strength was 5.3...5.9 at an age of 28 days, indicating a high fracture toughness of the obtained material. An increase in the content of alkali-activated cement in concrete determined a decrease in the influence of sand granulometry on concrete strength,due to its “floating” placement in the cement matrix.The introduction of a fine calcite additive ensured to reduce the shrinkage of concrete by 1.3...1.5 times at an age of 90 days due to the densification of the microstructure and the intensification of crystallisation processes. The implementation of these measures resulted in a high strength alkali-activated cement reactive powder concrete of strength classC80/95, high fracture toughness and reduced drying shrinkage.

Influence of Alkaline Binders on the Workability and Strength of Self Compacting Geopolymer Concrete

Self-compacting geopolymer concrete (SCGC) has emerged as a promising alternative to traditional concrete due to its environmental benefits. In SCGC, alkaline binders, such as sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃), play a crucial role in influencing both workability and strength. Notably, the ratio of alkaline binders significantly impacts the overall performance of SCGC. This study investigated five SCGC mixes with varying alkaline binder (A/B) ratios ranging from 0.40 to 0.60, incorporating 50% fly ash (FA) and 50% ground granulated blast furnace slag (GGBS). The mixes included 14 M NaOH, a superplasticizer (9 kg/m³), and extra water (54 kg/m³) to evaluate the effect of the A/B ratio on workability and mechanical strength properties. The results revealed that the fresh properties of SCGC with A/B ratios of 0.4, 0.45, and 0.5 complied with EFNARC guidelines, as assessed by the slump flow test, with the lowest T50cm slump flow recorded at 696 mm. The mix with an A/B ratio of 0.5 exhibited the best mechanical performance, achieving a compressive strength (CS) of 38.3 MPa, a splitting tensile strength (STS) of 4.63 MPa, and a flexural strength (FS) of 5.85 MPa. These findings suggest that an SCGC mix with a 0.5 A/B ratio optimizes rheological and mechanical properties at a 14 M NaOH concentration.

Eco-Flame Shield: Formulating a Hybrid Fire Retardant Coating Using Carbonized Rice Husk Ash, Carbonized Coconut Coir Ash, and Sodium Silicate

This research is a quasi-experimental study that experimented and tested the effectiveness of using carbonized rice husk ash (CRHA), carbonized coconut coir ash (CCCA), and sodium silicate (SS) in developing and formulating an eco-friendly hybrid fire retardant coating that slows down fire spread, provides a non-harmful alternative to conventional fire retardants, and promotes practical solutions and fire safety measures in various applications, benefiting the environment, community, and public safety. Through experimental tests, such as Time to Ignition, Flame Spread, and Flammability tests, the necessary data were collected, analyzed, and interpreted using a quantitative approach. The results concluded that treated wood Sample 3, formulated with 10% carbonized rice husk ash (CRHA), 15% carbonized coconut coir ash (CCCA), and 75% sodium silicate (SS), was the most effective formulation compared to the other treated wood samples (Sample 1 and Sample 2) and the untreated wood sample (Sample 4). The formulated fire-retardant coating demonstrated promising results as an effective solution, reducing waste and dependence on harmful chemicals. Its potential applications extended to textiles and construction, offering a cost-effective and environmentally friendly alternative. Further research was recommended to explore controlled application methods and to broaden the understanding of this eco-friendly hybrid fire retardant coating, promoting wider adoption and contributing to both environmental sustainability and economic viability.

Properties of alkali activated cellular lightweight binder blocks with industrial and agro waste

The construction industry is continuously seeking sustainable alternatives to conventional building materials. Alkali-Activated Cellular Lightweight Binder Blocks (AACLBs) present a promising solution by utilizing alkali activation technology to augment the properties of lightweight concrete. This research focuses on optimizing the composition of AACLBs by replacing conventional binders with alkali-activated materials derived from industrial by-products and agro waste with the help of a protein based foaming agent (FA). The industrial waste materials investigated include Fly Ash (F) and Blast Furnace Slag (BFS) while agro waste such as Rice Husk Ash (RHA) are considered as sustainable alternatives. With Sodium Hydroxide (NaOH) and Sodium Silicate (Na2SiO3) as activators, 8 different combinations are adopted in this study. Properties such as density and compressive strength (CS) are analyzed to assess the structural capabilities of the AACLBs and are compared with that of cement-based blends. The alkaline solution to binder ratio is kept constant as 2.5 for two dilution ratios (1:30 & 1:60) and ambient curing is adopted. The target densities for conventional cement-based mixes are set as 1200–1600 kg/m3 and 1500–1800 kg/m3 for alkali-based mixes. The findings show that, the highest CS of 42.76 MPa and a density of 1870 kg/m3 is observed for FB1 combination at a dilution ratio of 1:30. Conversely, the FBR2 combination at a dilution ratio of 1:60 yielded a CS of 21.23 MPa, accompanied by a minimum density of 988 kg/m3.

Study on Preparation and Heat Insulation Properties of Solidified Foams for Forest Fire Prevention and Control

ABSTRACT For effective prevention and control of forest fires, a new type of solidified foam was prepared by using composite foaming agent, foam stabilizer, sodium silicate, sodium bicarbonate solution, loess and cement as raw materials. The optimal ratio of solidified foam surfactant, foam stabilizer, gel agent, crosslinking agent and powder was investigated experimentally. Its thermal insulation performance was tested and its thermal insulation mechanism was analyzed. The results showed that when the surfactant ratio was SDS: AES = 2:1, the concentration was 0.8%, the concentration of foam stabilizer dodecyl alcohol, gelling agent WG and crosslinking agent NaHCO3 were 0.08%, 10% and 2%, respectively. When the powder ratio is loess: cement = 4:6, water-cement ratio 0.6 and foam content 8 V, the comprehensive performance of solidified foam is the best. The solidified foam is heated at different temperatures, and the temperature rise is the slowest. When it is heated at 400°C, the highest temperature is 71.92°C, which is 75.89°C lower than the highest temperature of gel foam. The fire retardant material has excellent stability and can block heat for a long time. In the process of fire extinguishing, it can effectively isolate oxygen, reduce heat transfer efficiency, and inhibit the spread of fire.

Development of technology for textile materials with special properties

Due to the increasing amount of oily wastewater accompanying the development of industry and society, as well as frequent accidental oil spills, there is a growing need for functional materials that absorb oil and separate oil and water. Various approaches have been used to manufacture such functional materials. The creation of new oil-absorbing materials with high selectivity towards water and oil by increasing hydrophobicity and oleophilicity is promising. In this paper, the issue of obtaining a composition for making textile materials hydrophobic and oleophilic is considered. The purpose of this work is to develop innovative textile materials designed to purify water resources from oil pollution and evaluate the effectiveness and safety of materials. The practical significance of the work lies in the need to develop a textile material that will surpass other materials in the efficiency of cleaning oil pollution, environmental friendliness and cost. Sodium oleate, liquid glass and citric acid were used for this purpose. The materials were treated with a ready-made solution, then dried for 10 minutes at 120 ° C and processed in a thermal press at 150 ° C for thermal fixation. 100% cotton fabric article 1030 and synthetic fabric 81421 premier Standard 250 (65% PE, 35% cotton) were used as the object of the study. New materials have been developed to ensure effective separation of oil from water, the physico-chemical foundations of the new method have been improved in order to give textile materials hydrophobic and at the same time oleophilic properties for effective purification of water resources from oil pollution. It has been established that new materials can be effectively used for high-quality water purification from oil pollution.

Bioaugmentation of Industrial Wastewater and Formation of Bacterial–CaCO3 Coupled System for Self-Healing Cement

This study investigates the potential of bioaugmentation with Bacillus species to enhance wastewater treatment and develop a bacterial–CaCO3 system for self-healing cement applications. Utilizing microbiologically induced calcium carbonate precipitation (MICP), this study evaluates the dual functionality of Bacillus licheniformis and B. muralis strains. For wastewater treatment, the bioaugmentation process achieved significant pollutant reductions, including a 99.52% decrease in biochemical oxygen demand (BOD5), a 92.13% reduction in chemical oxygen demand (COD), and a substantial removal of heavy metals and nutrients. This process also produced high concentrations of CaCO3 precipitate enriched with viable bacterial cells, demonstrating an eco-friendly approach to improving water quality. For self-healing cement applications, bioaugmented CaCO3 crystals were coated with nutrient and sodium silicate layers to form a bacterial–CaCO3 coupled system. This system demonstrated a 92% recovery in compressive strength after 180 days, highlighting its ability to autonomously repair microcracks in cement-based materials. The layered encapsulation strategy ensured bacterial viability and a controlled activation mechanism, offering a scalable and sustainable solution for infrastructure resilience. This dual-function approach addresses critical environmental and construction challenges by linking efficient wastewater treatment with innovative self-healing material development, contributing to global sustainability and circular economy goals.

Enhancing Mechanical Properties of Alkali-Activated Slag SIFCON for Sustainable Construction Using Recycled Glass and Tire-Derived Waste Steel Fibers

This paper presents the outcomes of a study in which continuous steel fibers, recovered from scrap tires of vehicles, were used to prepare alkali-activated slag-based slurry infiltrated fibrous concrete (SIFCON). In this experimental study, the steel fibers used were 250 mm long, with varying fiber contents of 0%, 1%, 2%, 3%, 4%, and 5%. The alkali-activated SIFCONs were produced by activating ground granulated blast furnace slag (GGBS) with a mixture of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) solutions. Mixtures with ordinary Portland cement (OPC) were also cast for comparison purposes. The feasibility of utilizing finely ground waste glass as a silicate source for chemical activator solution in alkali-activated SIFCONs was also investigated. In this context, two different molar concentrations of NaOH, namely 8 M and 14 M, were employed during production. As activators, one series of mixtures utilized sodium hydroxide and sodium silicate solutions, while the other series replaced sodium silicate with finely ground waste glass. As a result, three different waste materials were utilized in concrete. 30 different mixtures were cast and examined in the experimental study. Load–deflection curves were obtained in three-point bending test and mechanical properties of the mixtures such as compressive, splitting and flexural strengths, fracture energy, and toughness were determined. The flexural strength and toughness increased with the use of waste steel fibers. The continuous waste fibers derived from discarded tires yielded results comparable to commercially available fibers, demonstrating their effectiveness in enhancing mechanical properties. Depending on mix design, the alkali-activated SIFCON attained flexural strength exceeding 75 MPa and compressive strength surpassing 100 MPa. These results suggest that concretes incorporating a variety of waste materials can be effectively combined. This innovative approach bridges an existing gap in the literature by combining alkali activation, waste glass, and waste steel fibers, ultimately yielding a sustainable composite that outperforms normal concretes in terms of mechanical properties while promoting environmental sustainability. Test results demonstrate that it is possible to obtain concrete with comparable mechanical properties while primarily composed of by-products and waste materials. This approach marks a substantial step in achieving high-performance concrete that relies solely on waste or by-products.Graphical

C–S–H–PCE nanocomposites as hydration accelerator in calcined clay-limestone-blended low carbon cement

Abstract Recently, providing admixtures to improve the performance of the novel low-carbon-blended cement is needed to meet the requirement for environmentally friendly cements. In this study, calcium-silicate-hydrate (C–S–H) nanocomposites which are known as hydration accelerator for Portland cement were employed in such low-carbon cements. The investigation focused on the effect of polycarboxylate ether (PCE) possessing different side-chain lengths on the morphology of C–S–H nanocomposites synthesized from sodium silicate and calcium nitrate via chemical co-precipitation and on their performance (especially early strength enhancement) when applied in a calcined clay-blended cement (OPC substitution rate of 46 wt%). As observed by TEM, addition of PCE effectively controls the size of the C–S–H nanoparticles and delays the transition from C–S–H globules to foils. PCEs with short side-chain (23 EO units) exhibited the highest inhibition effect on the growth of the C–S–H nuclei, which was confirmed by particle size measurements. Additionally, incorporating such C–S–H–PCE nanocomposites into the calcined clay-blended cement (dosage 2.0 % by weight of cement) significantly improved fluidity of the cement pastes. Regarding compressive strength, pristine C–S–H produced only a minor improvement, whereas C–S–H–PCE nanocomposites yielded substantial enhancement, especially after 16 h and 1 day of curing. Remarkably, C–S–H–23PCE pronounced the strongest seeding and strength enhancing effect, owed to its particularly small particle size (d = 21.8 ± 0.3 nm). It also significantly accelerated the hydration of the silicate phases (C3S and C2S) in this blended cement, as was evidenced by isothermal heat flow calorimetry and XRD measurements.

Research on the performance and strengthening mechanism of composite‐enhanced recycled aggregate concrete

AbstractThe application of recycled aggregate concrete (RAC) greatly promotes the sustainable development of engineering construction, and improving its performance can further expand its practical application range. In order to obtain higher performance RAC, this article selects two composite pre‐treatment methods: cement silica mortar wrapping organosilicon immersion, water glass soaking, and organic silicon soaking to enhance the performance of recycled aggregate (RA). Subsequently, the composite reinforced RAC was poured, and their mechanical and durability properties were tested. The strengthening mechanism of the composite pre‐treatment method was analyzed. The results show that compared with the single‐treatment method, the composite strengthening method has an effect of increasing the apparent density of RA by 0.2%∼4%, and the effects of reducing the crushing value and water absorption are increased by 0.5%∼7.2% and 0.4%∼4.7%, respectively; both composite strengthening methods can improve the mechanical and durability properties of RAC. Analysis of the samples using SEM, TG, and XRD showed that both composite strengthening methods filled the microcracks and pores on the surface of the old mortar layer of RA and promoted the hydration of cement in the transition zone between the RAC interfaces, thereby increasing the interface strength and improving the mechanical and durability properties of RAC.

Research on the impact of carbide slag content on the strength and microstructure of solidified sludge during composite excitation.

A composite material was developed using carbide slag, water glass, slag, and micron silicon to facilitate the use of industrial waste resources. The mechanical properties of dredge sludge (DS) were analyzed, considering different proportions of cement, organic debris, and carbide slag. The composition and microstructure of the hydration products were analyzed using the X-ray diffractometer (XRD), scanning electron microscopy (SEM), and thermogravimetric (TG) analysis. The results indicate that with a precursor content of 20%, a water glass content of 3%, and an increase in carbide slag content from 4% to 12%, the strength of the sample initially increases and subsequently drops at each age. With a carbide slag level of 8%, the combination of CaO in the slag and water glass stimulated the slag and micron silica, leading to the formation of gel substances such C-S-H and C-A-S-H. The soil particles exhibited increased density as a result of the cohesive properties of the gel products. Following a maintenance period of 28 days, the sample's compressive strength rose to 2280 kPa. When the carbide slag level exceeds 8%, the presence of Ca(OH)2 in the mixture leads to the formation of carbonates, such as calcite, during the carbonization process. The organic matter subsequently undergoes a reaction with the Ca(OH)2 produced during the hydration of the mixture, leading to the formation of a highly soluble complex. As a result, only a limited quantity of calcium ions in the pore solution participate in the pozzolanic reaction, hence reducing the formation of gel reaction products such C-S-H.

Effect of NaOH Solution on Mechanical Properties and Morphology of Fly Ash Based Cold-Pressed Geopolymer

Cold-pressing method is beneficial in reducing the porosity of geopolymer matrix, but the low liquid volume will result in unreacted aluminosilicate materials. This problem can be resolved by increasing sodium hydroxide (NaOH) concentration. This paper thus investigates the effect of NaOH concentration on the properties of cold-pressed geopolymer. The fly ash was activated by sodium silicate (Na2SiO3) and 10, 12, 14 and 16 M of NaOH solution. The dry mix was compacted with a uniaxial hydraulic press and cured for 7 and 28 days. The specimens were measured by porosity and compressive strength measurements. Scanning electron microscopy (SEM) analysis was performed to determine the microstructure of specimens. The geopolymer was optimized at 14 M NaOH with the highest 28-day compressive strength (109.6 MPa) and lowest porosity (8.1%). The SEM micrographs proved that the geopolymer have a dense and compact microstructure.

Preparation, Characterization and Application of Sustainable Composite Phase Change Material: A Mineral Material Science Comprehensive Experiment

Phase change materials (PCMs) play a significant role in achieving sustainable objectives for green buildings. Organic solid–liquid PCMs have excellent heat energy storage density and suitable working temperatures, making them a focal point of research attention. However, these materials face challenges such as potential leakage, low thermal conductivity, and limited fire resistance, which hinder their direct application in the construction industry. Therefore, mineral-based PCMs are highly regarded due to their safety features, environmental friendliness, non-toxicity, and cost-effectiveness within sustainable building development. In this work, a multistage porous kaolinite-based geopolymer encapsulation material using primary raw materials like kaolinite mineral, sodium silicate surfactants, and hydrogen peroxide was successfully synthesized. The PEG is used as the organic solid–liquid PCM while natural graphite mineral serves as a heat transfer enhancement agent to fabricate a novel and sustainable mineral-based composite PCM, which could be applied at the environment temperature from 35–60 °C approximately. Furthermore, a study on material properties was conducted to investigate influencing factors. Comprehensive experimental reform on mineral-based PCMs will offer proficiency in experimental operations and foster the talents’ capacity for comprehensive design, which holds immense significance for understanding and designing mineral materials. This work holds great significance for the sustainable development for education and green buildings.

Role of Slag Replacement on Strength Enhancement of One-Part High-Calcium Fly Ash Geopolymer

This paper reports the effect of slag (SL) replacement and water-to-binder (w/b) ratio on properties of one-part geopolymer derived from high-calcium fly ash (FA) and sodium silicate powder (NP). The FA was replaced by SL at the rates of 20% and 40%, respectively. This study focused on conducting experimental tests to evaluate the relative slump, setting time, compressive strength, and flexural strength of one-part FA-based geopolymer. The relationship between compressive and flexural strengths of one-part geopolymer mortar was expressed using the simplified linear regression model, whereas the normalization of compressive and flexural strengths with SL replacement by the strength of one-part geopolymer mortar without SL as the divisor was also evaluated. Experimental results showed that the increase of SL replacement and w/b ratio significantly affected the workability and strength development of one-part geopolymer mortar. Higher SL replacement exhibited a positive effect on their compressive and flexural strengths; however, a reduction in its setting time was obtained. The enhancement in strength development of one-part geopolymer was primarily due to the increased calcium content of SL. Similarly, reducing the w/b ratio in the production of one-part geopolymer resulted in a decrease in setting time and an increase in strength development. Based on the relationship between compressive and flexural strengths, the prediction coefficient value (R2) obtained from the curve fitting procedure was 0.835, indicating a good level of reliability and acceptability for engineering applications. Doi: 10.28991/CEJ-SP2024-010-013 Full Text: PDF