Sodium Silicate Powder Research Articles

Development of a novel extrusion device to improve the printability of 3D printable geopolymer concrete

This study explores the printability of 3D geopolymer concrete using a novel extrusion device. Geopolymer, known for its eco-friendliness and rapid curing, offers an eco-friendly alternative to conventional cement in 3D printing. A novel extrusion device, integrating mixing and stirring functions, was developed to blend sodium silicate powder and precursor slurry effectively. Systematic experiments on mixing ratio, time, and speed revealed optimal conditions for geopolymer concrete printability. The precursor slurry remained pumpable for 90 min and displayed rapid reactivity in the new device. The extruded geopolymer concrete exhibited exceptional buildability, reaching a remarkable yield strength growth rate of 931.69 Pa/s. Actual printing tests resulted in a 154-layer hollow cylinder, 1840 mm tall, printed in just 26.87 min. Increasing mixing time enhanced compressive strength and reduced porosity, showcasing the potential of this set-on-demand approach and the novel extrusion device in 3D printable geopolymer concrete applications.

A new iron battery technology: Charge-discharge mechanism of ferrous chloride and ferric oxide electrolyte in all solid-state iron-graphite batteries

This study investigates a Fe/SSE/GF battery. Iron (Fe) as cathode material contains higher electrical capacity and competitive advantages. The solid-state electrolyte (SSE) material is sodium silicate powder mixed with iron compound powders. There are four types of iron compounds: 1) iron oxide, 2) chlorinated/Na-rich iron oxide, 3) Cl-rich iron oxide, 4) ferrous chloride, which are compared with sodium silicate powder. The negative electrode material is graphite film (GF). According to experiments, converting iron into iron oxide or ferric chloride can enhance battery capacity (beyond 200 mAh/g) and cycle life. The reliability of the Fe/SSE/GF battery was assessed by substituting sodium silicate powder with an iron compound electrolyte and adding binder (Polyvinyl Alcohol, PVA) into powder to enhance the performance of Fe/SSE/GF. This experimental research is not only innovative but also represents a significant milestone in the field of solid-state energy storage.

Effect of Solid Sodium Silicate on Workability, Hydration and Strength of Alkali-Activated GGBS/Fly Ash Paste

Based on economic and environmental considerations, the recycling economy of mineral waste has been found to have great potential and economic benefits worldwide, in which alkali-activated cementitious materials are one of the main developing directions. The alkali activators commonly used in alkali-activated cementitious materials are the composite activators of sodium silicate solution and solid sodium hydroxide, which not only need to deal with high viscosity and corrosive chemicals, but also need to be prepared in advance and properly stored. In this paper, ground granulated blast furnace slag (GGBS) and fly ash were used as precursors, while solid sodium silicate powder was applied as the alkali activator. In addition, the precursors were mixed with the activator in advance and activated by adding water to prepare alkali-activated GGBS/fly ash cement. The influence of precursor components, the dosage of the alkali activator and the liquid–solid ratio on the working performance, mechanical strength and hydration process of alkali-activated cement was studied. The results showed that the further incorporation of GGBS accelerated the alkali activation reaction rate and improved the strength of the specimen. However, in the specimen with GGBS as the main component of the precursor, the main hydration product was C-A-S-H gel, which was different in the structural order and quantity. The compressive strength indicated that there was the best amount of activator to match it in terms of the precursor with certain components. A too high or too low amount of activator will hinder the alkali activation reaction. This study can provide some significant reference material for the use of solid alkali activators in alkali-activated cementitious materials.

Mechanical properties of an eco-friendly one-part alkali-activated binder: Influence of metakaolin and water content

Alkali-activated binder (AAB) is a product with lower carbon footprint and has great potential to be an alternative to Portland cement in civil construction. In this study, one-part AAB has been synthesized by mixing alternative sodium silicate powder, obtained from rice husk ash (RHA) and metakaolin (MK). The main objective was to verify the effect of MK (two types were used with different reactivity characteristics) and water content on the mechanical properties of pastes and mortars produced with the one-part AAB. Some tests were conducted (e.g. setting times, flexural and compressive strengths, elastic modulus) and the results indicated that the MK type and the water content directly affect different properties. As expected, the decrease in water content decreased the workability of the mortars and improved the mechanical strength. A more reactive MK provided an increase in compressive strength higher than 60%. The results confirm the possibility of producing an alternative sodium silicate powder from RHA dissolution, that when mixed with MK, results in AAB with acceptable compressive strength. This paper reveals that with the correct materials and a good mix design, the properties of this eco-friendly AAB can be considerably improved.

Effects and mechanism of superplasticizers and precursor proportions on the fresh properties of fly ash – slag powder based geopolymers

To promote the application of green geopolymer materials, the effects and mechanism of commercial superplasticizers on the fresh properties of one-part geopolymers prepared from fly ash (FA), slag powder (Slag) and anhydrous sodium silicate powder were studied, including flowability, rheological properties and particles packing properties. And the influence of precursor proportion (FA:Slag) i.e. the mass proportion of FA and Slag on the effectiveness of superplasticizers was also considered. The results show the fluidity of geopolymer with 2.4 % liquid naphthalene-based superplasticizer (N-L) increased by 19.20 % when FA:Slag = 85:15, and the 0.20 % one kind of solid polycarboxylate-based superplasticizer (PC-S2) increased the fluidity of geopolymer by 16.47 % when FA:Slag = 95:5. The addition of superplasticizers could improve fluidity, increase plastic viscosity, and decrease yield stress of the pastes. The particles packing properties, including excess water and water film thickness (WFT) of the geopolymer pastes with superplasticizers also increase. It is interesting to find that the effectiveness of superplasticizers varies from different types of superplasticizers. This could be understood by the mechanism of the two types of superplasticizers based on Zeta, FTIR results, and water film theory. Accordingly, naphthalene-based superplasticizers guided by the adsorption-dispersion effect, due to their stable molecular structures and short chains, could improve the workability, while the effectiveness of polycarboxylate-based superplasticizers guided by the steric hindrance effect of lateral chains may be judged by the combined effects of the interaction between particles and the effects induced by superplasticizers.

Mechanochemically activated bottom ash-fly ash geopolymer

A source of sub-bituminous coal bottom ash was mechanochemically activated by co-grinding fly ash and a sodium silicate powder for use in a geopolymer application. A total of nine different mixes were considered to study the effects of the mechanochemical treatment, mixing procedure, and bottom ash loading. The compressive strength, reactivity, rate of geo-polymerization and morphology were investigated using isothermal calorimetry, nano-indentation, optical and scanning electron microscopy, and Fourier-transform infrared spectroscopy. The solid-state mechanochemical activation attacks the fly and bottom ash particles producing small sheet-like activated agglomerates. The activation enhances the dispersion of the activated particle, alters the sodium silicate and aluminosilicate reaction kinetics and intensifies the interconnectivity of geopolymer structure, decreases pore size, and significantly increases compressive strength (between 60% and 80%). When treated in this manner, the bottom ash serves as an effective extender to fly ash in geopolymer systems up to 50% replacement of fly ash without significant reduction in mechanical strength or significant alteration to the microstructure.

Producing sodium silicate powder from iron ore tailings for use as an activator in one-part geopolymer binders

Mine tailings disposal is an increasingly important issue for mining companies. Two recent tailing dam failures in Brazil have caused unmeasurable environmental, social and economic damages. This study evaluated the use of iron ore tailings (IOT) as a source of silica (SiO2) to produce an alternative form of sodium silicate (SS) for use as an activator in one-part geopolymer binders. The novel SS was produced in a mechano-thermo-chemical process for mixing IOT with sodium hydroxide (NaOH). The materials were characterised by mineral composition, mineral phase, chemical groups and morphology. One-part geopolymer binders were synthesised with commercial SS and SS produced from tailings to compare their reactivity. Compressive strength tests showed that geopolymers produced with tailings SS and commercial SS achieved maximum mechanical resistance values of approximately 32 MPa and 40 MPa, respectively, which are comparable to regular Portland cement.

Strength effect of alkali activated red mud slag cement in ambient condition

The excess demand for cement in construction area is relevant compatible to maxima utilization of industrial solid waste as an alternation of binding material. Since the disposal of red mud turns to major environmental issue for its alkaline nature, so this research was to evaluate the viability of red mud as a cementitious material. This type of material was developed by the addition of granulated slag and red mud with three different proportion i.e. 30/70, 50/50, and 70/30. Those solid compositions were activated with the low concentration of the alkali solution prepared by sodium hydroxide pellet and sodium silicate powder varying as mole proportion of SiO 2 -Na 2 O from 0 to 1.5 mol. Best compressive strength values were obtained by ARSC 50 containing 50% slag and 50% red mud, but activated by SN 1.5 with the value 90.1 MPa after 60 days of curing age in ambient condition. Hydration characteristics of ARSC 50 were observed by XRD, SEM. Ettringite and amorphous C-S-H gel are the prime factors of strength development of ARSC. This paper provides a major solution of utilization of red mud and preservation of energy and natural sources.

Influence of alkali activator type and proportion on strength performance of calcined clay geopolymer mortar

The global abundance of low purity kaolin clay and the low embodied energy associated with its calcination makes it a promising aluminosilicate source that will extend the application of geopolymers. In this paper, the compressive strength and microstructure of iron rich, calcined clay based geopolymer mortars activated by two forms of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) solutions were studied and reported. The samples were cured either in the air or under sealed conditions. The result shows that the 28 days strength of the mortars achieved by reacting the calcined clay with hydrous sodium silicate powder, dissolved under normal atmospheric conditions and sodium silicate solution produced in a pressure reactor vessel are 0.5 MPa and 28.8 MPa respectively. The former produced a non-geopolymer mortar that has a discrete, undensified and uncompacted structure with heavy presence of residual particles, thus, achieving a strength that is 1.7% of the latter. The functional group analysis reveals that the binding phase of the peak strength mortar is ferro sialate (Fe-Si-O-Al).

Influence of supplementary cementitious materials on rheological properties of 3D printed fly ash based geopolymer

3D printed fly ash based geopolymer was prepared with fly ash and quartz sand as main raw materials while slag powder and silica fume as supplementary cementitious materials. In this paper, anhydrous sodium silicate powder was used as activator and ATTAGEL-50 thixotropic thickener was used as 3D printing additive. The effect of slag powder and silica fume on the rheological properties of 3D printed fly ash based geopolymer was studied. The results show that the apparent viscosity, thixotropic property, plastic viscosity and yield stress of geopolymer first increased and then decreased with the increase of slag powder and silica fume respectively. Compared with the Bingham (BH) model, the Herschel- Bulkley (H–B) model is more accurate and more suitable for characterizing the rheological model of fly ash based 3D printed geopolymer. The suitable content for slag powder is 10%. On the basis of adding slag powder, silica fume was also used to replace the fly ash, the suitable content for silica fume is 10% in this fly ash-slag powder based 3D printing geopolymer. According to the SEM observations, it is found that the interior of the printing layer of the 3D printing block is more conducive to the production of the geopolymer gel than the interlaminar surface of the printing layers. It is found that the printing layers are connected with each other through bridges.

Synthesis and characterization of NaX-type zeolites prepared by different silica and alumina sources and their CO2 adsorption properties

Abstract In this work, two pairs of silicon and aluminium sources (sodium silicate solution + Al(OH)3 and sodium silicate powder + sodium aluminate) were used for synthesizing zeolites which were labeled as Z1 and Z2, respectively. The results from XRD, BET and surface analysis indicated that sodium silicate and sodium aluminate sources yielded zeolite with high surface area and pore volume. Cetyltrimethylammonium bromide (CTAB) and heptane were used to modify the CO2 adsorption capacity and selectivity of zeolite NaX. The surface area and pore volume of zeolite products increased due to smaller crystalline size and then resulted in significant enhancement of CO2 uptake of the synthesized zeolite NaX. The role of additives on zeolite formation was to increase the nuclei formation rate and number which gave rise to smaller zeolite crystals. The best adsorbent exhibited high CO2 adsorption capacity (5.08 mmol g−1 at 303 K) and relatively high CO2 selectivity over N2 (116) which indicated the potential of adsorbent to separate CO2 from flue gas application.

Efficiency of Different Superplasticizers and Retarders on Properties of 'One-Part' Fly Ash-Slag Blended Geopolymers with Different Activators.

Currently, there are a very limited number of studies on the effect of admixtures on properties of ‘one-part’ geopolymers. This paper reports the effects of different superplasticizers and retarders on fresh and hardened properties of one-part fly ash-slag blended geopolymers made by different solid activators. Two different grades of sodium silicate, namely anhydrous sodium metasilicate powder (nSiO2/nNa2O = 0.9) and GD Grade sodium silicate powder (nSiO2/nNa2O = 2.0) were used as the solid activators. Five different commercially available superplasticizers, including three modified polycarboxylate-based superplasticizers (denoted as PC1, PC2, and PC3) and two naphthalene-based superplasticizers (denoted as N1 and N2), as well as three different retarders, including sucrose, anhydrous borax and a commercially available retarder, were investigated. Workability, setting time and compressive strength of the mixtures without and with addition of each ‘individual’ admixture were measured. The results showed the effect of admixtures on the properties of the one-part geopolymers significantly depended on the type of solid activator and the type of admixture used. When GD Grade sodium silicate powder was used as the solid activator, all investigated admixtures not only had no positive effect on the workability and setting time, but also significantly reduced the compressive strength of the mixture. However, when anhydrous sodium metasilicate powder was used as the solid activator, the PC1 and sucrose were the best performing superplasticizer and retarder, respectively, causing no reduction in the compressive strength, but significant increase in the workability (up to + 72%) and setting time (up to + 111%), respectively as compared to the mixture with no admixture. In addition, the results also showed that addition of ‘combined’ admixtures (i.e., PC1 in the presence of sucrose) significantly increased the workability (up to + 39%) and setting time (up to + 141%), but slightly reduced the compressive strength (−16%) of the mixture activated by anhydrous sodium metasilicate powder, as compared to the mixture with no admixture.

Production of sodium silicate powder from waste glass cullet for alkali activation of alternative binders

A simple process to produce sodium silicate powder from glass cullet has been developed. A mixture of glass powder, sodium hydroxide powder, and water was heated at temperatures of 150 to 330 °C. The effects of glass to NaOH ratio, temperature and duration, inclusion of water and fineness of NaOH were investigated. Fly ash and fly ash/GGBS blends were the precursors for alkali activated binder (AAB) mortars produced with this sodium silicate. Compressive strengths were similar to or better than those obtained with commercially available sodium silicate and sodium hydroxide solutions. FT-IR tests suggested that the reactivity of the glass derived sodium silicate powder was related to the number of non-bridging oxygen atoms in the silicate structure. Cost comparison between AAB and Portland cement concretes gave similar results for normal strength concretes (35 MPa). AAB concretes with higher strengths (50 and 70 MPa) can be cheaper than equivalent traditional concrete.

Microsilica in Sodium Silicate Bonded Sands

This paper investigates the microsilica addition value in the improvement of the sand molds and cores properties made with sodium silicate binders. There are experiments confirming the importance of the better sand mixtures mobility in the strengthening of these molds and cores. The paper explains the difference between microsilica and nanosilica in their interaction with alkaline silicate solutions and shows how the products of this interaction affect the properties of the sand mixtures. The results presented in the paper show the role of microsilica in curing sodium silicate bonded sands and demonstrate more possibilities to spread its positive complex effect on the sand molds and cores cured chemically, without heat. Conducted experiments with these sands proved the benefits of applying microsilica as a sand additive for increasing density and strength of the molds and cores, for easing their shakeout by lowering silicate level in the binder system. It is shown that the microsilica presence in the powder component allows using a hydrous sodium silicate powder also as a part of this component to replace a liquid sodium silicate in the two-component silicate binder system as well as creating pourable dry mixtures of silica sand and all solid additives of the binder system.

Fabrication of hollow silica microspheres utilizing a hydrothermal approach

Hollow silica microspheres (HSMSs) have been successfully fabricated via a facile hydrothermal route using d-glucose as the sacrificial template and sodium silicate powder as the silica precursor. The resulting silica hollow particles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and infrared spectroscopy (IR). The surface area was determined using the BET method. SEM and TEM images exhibited micro-sized silica hollow particles with a size of ∼1.5 μm.

Effect of Sodium Silicate Addition on Flame Retardancy of the Oil Paint Produced byModern Paint Company

In order to produce a coating with suitable properties, many additives are included in a coating formulation to achieve specific property modifications . In this work , two kinds of flame retardant materials were used as additives to increase the combustion resistance , and to decrease the flame spread of oil paint , these are : soluble Sodium Silicate and Sodium Silicate powder with oil paint. Different weight percent ratios (2.5 , 5 , 7.5 , 8.5 , 10 , 12.5 ,15 ) % for the two additives were added to oil paint to obtain different samples. It was found that , good flame retardant , and distinct decreasing in flame spread ( flame speed ) , of oil paint was obtained , in all weight percent ratios for all the samples of the two additives . Self extinguishing was observed at the ratios (7.5 , 8.5 , 10 , 12.5 ) % for the two additives , and ( no burning ) for them , were observed at (15) % . The mechanical properties tests ( adhesion force , impact strength ) were carried out to painted samples with oil paint mixed with second additive for all the above ratios, after about month from its preparation , the samples complied with Iraqi standard specifications No. 960

Effect of mechanical activation on jell boronizing treatment of the AISI 4140

The article presents the effect of mechanical activation on the growth kinetics of boride layer of boronized AISI 4140 steel. The samples were boronized by ferroboron+(SiO2–Na2O) powders for 873–1173K temperature and 2, 4, 6 and 8h times, respectively. The morphology and types of borides formed on the surface of AISI 4140 steel substrate were analyzed. Layer growth kinetics were analyzed by measuring the extent of penetration of FeB and Fe2B sublayers as function of treatment time and temperature in the range of 873–1173K. High diffusivity was obtained by creating a large number of defects through mechanical activation in the form of nanometer sized crystalline particles through the repeated fracturing and cold-welding of the powder particles, and a depth of 100μm was found in the specimen borided by the 2h MA powders, for 4h and 1073K, where 2000–2350 HV were measured. Consequently, the application conditions of boronizing were improved by usage of mechanical activation. The preferred Fe2B boride without FeB could be formed in the boride layer under 973K boronizing temperature by mechanically activated by ferroboron+sodium silicate powder mixture due to the decrease of the activation energy.

Microstructure Study of Early In Situ Reaction of Fly Ash Geopolymer Observed by Environmental Scanning Electron Microscopy (ESEM)

The alkali activation of waste materials can produce a binder with similar properties as Portland cement but without the drawback linked to greenhouse gas emissions. Geopolymer pastes were made using coal fly ash as precursor and sodium hydroxide and solid sodium silicate powder as alkaline activators. One sample was activated with sodium silicate only while the second sample used a 50:50 mass% mixture of sodium silicate and 8 M NaOH solution. Fresh geopolymer paste was immediately placed in the Environmental SEM chamber for microstructure observation using the ESEM mode. The sodium silicate activator dissolves rapidly and begins to bond fly ash particles. Open porosity can be observed and is rapidly filled with gel as soon as the liquid phase is able to reach the ash particle. The liquid phase is important as a fluid transport medium permitting the activator to reach and react with the fly ash particles. During this ESEM experiment, the reaction was limited to the surface of the fly ash particles. The reaction products examined had a gel like morphology and no crystallized phase was observed. The effect of the activator on the gel composition was investigated by quantitative microanalysis. The gel analyzed in the sample activated with the mixture of sodium silicate and NaOH solution is enriched in Na and Al. In that sample, the fly ash reaction rate is more advanced considering that the gel is richer in Al and that this element results from the fly ash. In fly ash-based geopolymers, the aluminum content of the aluminosilicate gel is an indicator of the fly ash reactivity.

Properties of alkali-activated mortar and concrete using lightweight aggregates

This study reports the testing of 12 alkali-activated (AA) mortars and six AA concretes using lightweight aggregates. These tests aimed to explore the significance and limitations of the development of lightweight AA mortar and concrete. Ground granulated blast-furnace slag, which was used as source material, was activated by sodium silicate powder. The main parameter investigated was the replacement level of lightweight fine aggregates to the natural sand. The effect of the water–binder ratio on the compressive strength development was also studied in AA mortars. Initial flow and development of compressive strength were recorded for the lightweight AA mortar. For the lightweight AA concrete, many factors were measured: the variation of slump with elapsed time, the development of compressive strength, splitting tensile strength, moduli of rupture and elasticity, stress–strain relationship, bond strength and shrinkage strain. Test results showed that the compressive strength of AA mortar decreased linearly with the increase of the replacement level of lightweight fine aggregates, regardless of the water–binder ratio. The compressive strength of AA concrete, however, sharply decreased when the replacement level of lightweight fine aggregates exceeded 30%. In particular, the increase in the discontinuous grading of lightweight aggregate resulted in the deterioration of the mechanical properties of AA concrete.

Properties of cementless mortars activated by sodium silicate

The present paper reports the testing of 12 alkali-activated mortars and a control ordinary portland cement (OPC) mortar. The main aim is to develop cementless binder activated by sodium silicate powder. An alkali quality coefficient combining the amounts of main compositions of source materials and sodium oxide (Na 2O) in sodium silicate is proposed to assess the properties of alkali activated mortars, based on the hydration mechanism of alkali-activated pastes. Fly ash (FA) and ground granulated blast-furnace slag (GGBS) were employed as source materials. The ratio of Na 2O-to-source material by weight for different mortars ranged between 0.038 and 0.164; as a result, alkali quality coefficient was varied from 0.0025 to 0.0365. Flow loss of fresh mortar, and shrinkage strain, compressive strength and modulus of rupture of hardened mortars were measured. The compressive strength development of alkali activated mortar was also compared with the design equations for OPC concrete specified in ACI 209 and EC 2. Test results clearly showed that the flow loss and compressive strength development of alkali-activated mortar were significantly dependent on the proposed alkali quality coefficient. In particular, a higher rate of compressive strength development achieved at early age for GGBS-based alkali-activated mortar and at long-term age for FA-based alkali-activated mortar. In addition, shrinkage strain and modulus of rupture of alkali-activated mortar were comparable to those of OPC mortar.