Sodium Water Glass Research Articles

Structure of sodium silicate water glass—X-ray scattering experiments and force-field molecular dynamics simulations

Sodium silicate water glass is used in various applications as adhesives and lubricants. Herein, we used X-ray scattering experiments and force-field molecular dynamics (MD) simulations to investigate the structure of sodium silicate water glass. The concentrated sodium water glass had a low-Q pre-peak; in contrast, the diluted glass did not, as observed from X-ray scattering experiments. The intensity of the low-Q peak decreased with an increase in pressure. MD simulations provided a structure of sodium silicate water glass with sodium clusters surrounded by hydrated silicate anions at low pressures. These sodium clusters were the origin of the low-Q peaks in the simulated patterns. The sodium clusters dissolved in water with an increase in pressure, and consequently, the intensity of the low-Q peak drastically decreased.

Strength and Microstructure Characteristics of Blended Fly Ash and Ground Granulated Blast Furnace Slag Geopolymer Mortars with Na and K Silicate Solution.

Mineral geopolymer binders can be an attractive and more sustainable alternative to traditional Portland cement materials for special applications. In geopolymer technology the precursor is a source of silicon and aluminium oxides, the second component is an alkaline solution. In the synthesis of geopolymer binders the most commonly used alkaline solution is a mixture of sodium or potassium water glass with sodium or potassium hydroxide or silicate solution with a low molar ratio, which is more convenient and much safer in use. In this paper, we present the influence of sodium or potassium silicate solution on the physical and mechanical properties of fly ash and ground granulated blast furnace slag-based geopolymer mortars. Mercury intrusion porosimetry and microstructural observation allowed for comparing the structure of materials with a different type of alkaline solution. The evolution of compressive and flexural tensile strength with time determined for composites using 10%, 30% and 50% slag contents (referring to fly ash mass) was analysed. The tests were performed after 3, 7, 14 and 28 days. It was observed that, as the amount of slag used increases in the precursor, the strength of the material grows. Mortars with the sodium alkaline solution were characterised by a higher strength at a young age. However, the values of strength 28 days were higher for geopolymers with potassium alkaline solution reaching 75 MPa in compression. Geopolymer mortar microstructure observation indicates a high matrix heterogeneity with numerous microcracks. Matrix defects may be caused by the rapid kinetics of the material binding reaction or shrinkage associated with the drying of the material.

The use of limestone sludge for the geopolymer preparation

The study investigates the effect of sludge waste from mining and washing of limestone on the properties of geopolymer binders based on metakaolin and blast furnace slag. The effect of adding two types of limestone sludge on workability, setting time, compressive strengths, durability and pore distribution was investigated. Limestone sludge was dosed in an amount of 0–30 %. Sodium water glass was used as an alkaline activator in the ratio of 5:4. A linear correlation between the flowability and limestone sludge content was observed, and very satisfactory results of compressive strength after 90 days were obtained for samples with sodium water glass (about 55 MPa). The positive effect of CaCO3 on strength was confirmed. The increased content of clay components resulted in a reduction of compressive strength.

Effectiveness of common water-reducing admixtures in alkali-activated slag pastes with different types of activator

Rheology of alkali-activated slag (AAS) is a very complex issue, where the activator nature as well as its dose play an important role. Moreover, the use of water-reducing admixtures in these systems is an issue, as they often do not work properly. This could be attributed to the high pH as well as to the surface chemistry of AAS. Therefore, lignosulfonate-, polynaphthalene- and polycarboxylate-based superplasticizers were used to modify AAS pastes with sodium waterglass, hydroxide and carbonate activator. These pastes were tested using a rotational rheometer in an oscillatory shear mode of increasing shear strain to observe the evolution of viscoelastic moduli and to determine the oscillatory stress corresponding to the linear viscoelastic region limit (“yield point”) and to the crossover point, where the storage modulus equals the loss modulus (“flow point”). In most cases, the used plasticizers did not improve the rheological properties; the only exception was the lignosulfonate one in sodium hydroxide-activated slag.

Décalcification resistance of various alkali-activated materials

The resistance of alkali-activated materials (AAMs) to degradation processes, particularly the decalcification, was studied in this paper. The ground granulated blast furnace slag was alkali-activated using various activators with the same activator dosage 6% Na2O by slag weight (sodium hydroxide, sodium waterglass and sodium carbonate) and subjected to testing of decalcification resistance (immersion in 6M NH4 NO3) for 84 days. The reference samples were stored in water. The progress of degradation was studied using the phenolphthalein technique, mechanical properties testing (compressive and flexural strength), and dilatometry analysis or weight measurements. The results obtained were compared to the CEM III/A 32.5R. The significant loss of mass along with the deterioration of mechanical properties were observed for all binder types, still some of the AAMs showed better durability than the cementitious one.

Study on regulators of purifying magnesite ore by cationic reverse flotation

The floatability of magnesite, dolomite and quartz is a major factor affecting the removal of silicon and calcium from magnesite ore. The effect of the regulators sodium hexametaphosphate (SH), sodium silicate (SS), trisodium phosphate (TP), tannic acid (TN) and monoammonium oxalate (OA) on the floatability of magnesite, dolomite, and quartz under the ether amine (EAH) system was studied. The results show that the five regulators have relatively little influence on the floatability of quartz and magnesite. Dolomite can be activated when the dosage of SH is less than 40 mg/L; however, dolomite can be inhibited when the SH dosage is greater than 40 mg/L. The other four regulators have inhibitory effects on dolomite, and TN and TP have strong inhibitory effects on dolomite. Under the conditions of optimum grinding fineness, pH and collector dosage, a recovery of approximately 70% and a concentrate with a grade of over 47% were obtained by three stages of reverse flotation using sodium hexametaphosphate and water glass as regulators and Haicheng magnesite ore with an SiO2 content of 2.38% and a CaO content of 0.75%. Potentiometric measurements and infrared spectroscopy analysis show that physical adsorption occurs between the three minerals and collectors, while the interaction of magnesite and dolomite with SH and SS involves both physical adsorption and chemical adsorption.

Use of Ash after Denitrification as an Additive to Concrete Based on Alcali-Activated Slag

This paper deals with the possibility of using fly ash after denitrification by the SNCR method a partial replacement in alkali-activated concrete based on blast furnace granulated slag. Previous research has verified the use of fly ash after denitrification in alkali-activated materials based on blast furnace granulated slag, and so far no negative effects on the properties of these mixtures have been found. The tests were performed on cement test specimens. As part of the preparation of concrete mixtures, two recipes were prepared. The first reference mixture contained only blast furnace granulated slag activated by sodium water glass with silicate modulus of 2. The second recipe was modified by replacing of 30% slag by fly ash after denitrification by SNCR method. Within the strength characteristics, the reference mixture always achieved better results. Very slow increases in strength were recorded for the mixture with 30% slag replacement by fly ash, when the compressive strength after 7 days of maturation was only 4.5 MPa.

Influence of Water Glass Introduction Methods on Selected Properties of Portland Cement

This article presents a study of the effect of water glass and its introduction on the hydration of Portland cement and its properties in plastic and solid states. The introduction of sodium water glass into the mixing water extends the setting time of Portland cement by 35%, while introduction into the cement paste reduces it by 24.4%; for potassium water glass, the respective values are 10.8% and 10.8%. The introduction of sodium water glass into the mixing water decreases its consistency by 17.6%; its introduction into the cement paste reduces its consistency by 97%. Based on microcalorimetric studies and using the modelling method, mechanisms of the processes occurring in the cement paste, for various methods of introducing water glass admixtures, and their influence on the properties of cement are proposed. The important implications of the obtained results are that, using various methods for introducing admixtures of water glass, it is possible to regulate the setting of cement slurries within significant limits that are important during their transportation.

Microstructural evolution and carbonation behavior of lime-slag binary binders

The present study investigated the microstructural evolution and carbonation behavior of lime-slag binary binders. Samples having various lime/slag ratios were fabricated and characterized with the aid of X-ray diffractometry, thermogravimetry analyses, 29Si nuclear magnetic resonance spectroscopy, mercury intrusion porosimetry, autogenous and carbonation shrinkage measurements, carbonation depth measurements, and compressive strength development tests. These test results revealed that the carbonation of lime-slag binary binders yielded stable carbonates and subsequently refinement of the pore size and a corresponding strength modification. In addition, the lime-slag binary binders exhibited much less autogenous shrinkage movement than typical alkali-activated slag made with a combination of sodium hydroxide and water glass due to its low reaction rate and volumetric expansion accompanied by the hydration of lime. On the other hand, the phenomenon of the carbonation shrinkage of lime-slag binary binders resembles that of Portland cement due to the presence of portlandite, which served as a carbonation buffer.

Environmental impact assessment of pavement road bases with reuse and recycling strategies: A comparative study on geopolymer stabilized macadam and conventional alternatives

Geopolymer is a potential solution to the high carbon emissions caused by cement. Life cycle assessment (LCA) methodology was applied in this study to evaluate the environmental impacts of pavement road bases with reuse and recycling strategies. We considered four types of stabilized road base materials to evaluate environmental impacts: waste glass-fly ash based geopolymer stabilized macadam (WFAG), fly ash based geopolymer stabilized macadam (FAG), cement stabilized macadam (CS) and cement-fly ash stabilized macadam (CFAS). Two alkaline activators were used to synthesize geopolymer road base materials. The results showed that the application of geopolymer road bases reduced global warming (GWP) significantly. Comparing with CS, the GWP of WFAG and FAG declined by 17.9% CO2, eq per function unit. The combined alkaline activator consisting of sodium hydroxide (NaOH) and water glass had lower environmental impacts compared to the one with pure NaOH alkaline activator. The ozone layer depletion (ODP) of geopolymer stabilized road bases using pure NaOH solution was an order of magnitude higher than the ODP using the combined alkaline activator consisting of NaOH and water glass. For other indicators except GWP, the environmental impacts of conventional road bases were lower than geopolymer stabilized road bases, indicating a pollution transfer during application of geopolymer road bases.

The role of recycled waste glass incorporation on the carbonation behaviour of sodium carbonate activated slag mortar

This study investigates the influences of recycled waste glass powder (RGP) on the carbonation behaviour of sodium carbonate activated ground granulated blast furnace slag (GGBS) mortars. The effect of activator dosages, types and RGP addition on resistance to carbonation are evaluated. The results indicate a high dosage of sodium carbonate or water glass combination as activator always can enhance the ability of resistance to carbonation. Furthermore, the addition of 30% RGP in the GGBS binder system seems to significantly improve the resistance to carbonation of mortars. The carbonation shrinkage is reduced after RGP incorporation; at the same time, a higher strength performance is observed. The RGP in sodium carbonate activated GGBS blends shows no influence on the species of reaction products. However, after carbonation, the sample containing RGP promotes the formation of nahcolite, while less bound water loss and calcium carbonate formation are identified. A high volume of gel pores (<10 nm) is formed in the RGP sample compared to specimens only containing GGBS. These properties contribute to a better resistance to carbonation for RGP containing sodium carbonate activated GGBS mortars.

Frost Resistance of Alkali-Activated Concrete—An Important Pillar of Their Sustainability

Sustainable development of concrete construction requires sustainable materials or sustainable binders. Specifically, alkali-activated materials (AAMs) are an interesting and wide group of materials. They have good strengths and are considered environmentally friendly materials because secondary materials are consumed during the preparation of AAMs. The durability of AAMs is also excellent. One of the most important parts of durability is frost resistance. The frost resistance of alkali-activated materials is usually very good. However, some studies showed opposite properties and poor frost resistance. The reason for this may be a different composition of the activator. The content of alkalis is often considered the main characteristic of alkali-activated materials. However, SiO2 content can play an important role too. This paper discusses the different results for the mechanical properties and frost resistance of different compositions of alkali activators made of sodium water glass with a silicate modulus modified with potassium hydroxide. The role of the activator content and the water-to-cement ratio in this phenomenon is discussed. The results of this article show that the strengths of AAMs are significantly affected by the curing method. Water curing reduced some of the strength of the specimens compared to foil-covered specimens. Frost resistance depends on the method of curing and on the composition of the activator; some concretes with high strengths showed very low frost resistance.

Композиционный строительный материал с использованием отходов лесохимии в составе

The objective of this study is to develop a technology for manufacturing concretes and their formula-tions using hydrolysed lignin to improve their quality characteristics (compressive strength, water re-pellency, frost resistance). To achieve this goal, the following tasks should be solved: to study the chemical composition of hydrolysed lignin; to reveal the influence of mechanochemical activation on the structure of hydrolysed lignin; to select optimal conditions for obtaining composite building materi-als; to determine the physical and mechanical properties of the developed composite materials. Port-land cement M 400 was used in the experiments; sand was used as a fine aggregate (GOST 8736-2014) with a fineness modulus of 2.2 at a ratio of 1:4 (the expected concrete grade is B35). The wa-ter-cement ratio was 0.5. 10% sodium water glass (GOST 13078-81), finely ground hydrolysed as lig-nin organic filler and carbamide (GOST 2081-92) as organic modifier were used. IR spectroscopy was used to determine the chemical composition of hydrolysed lignin. The study showed that hydrolysed lignin is an active organic additive. The polar groups (hydroxyl, carbonyl, carboxyl) in its molecule are capable of strong intermolecular interaction and can facilitate its association in solutions, leading to possible chain cross-linking reactions, condensation reactions, both in acidic and alkaline media. To obtain high-quality construction composite materials with desired properties, the following raw mixture comprising Portland cement, sand and additional components is recommended: 30–50% of hydrolysed lignin and 20–40% of carbamide of the mixture mass.

The influence of alkaline activator on immobilization of metals in alkali-activated blast furnace slag

In this work the influence of alkaline activator on immobilization of lead and copper in alkali-activated blast furnace slag was investigated. A total of five alkali activators were used; sodium waterglass, potassium waterglass, sodium hydroxide, potassium hydroxide and sodium carbonate. The leaching test according to ČSN EN 12457°-4 was used to evaluate the level of immobilization of heavy metals, the leached solutions were analyzed by ICP-OES. For a better understanding of immobilization process, the selected samples were characterized by analytical methods (SEM, XPS). It was found that the degree of immobilization of Pb2+ and Cu2+ in AAS was very high regardless of the type of alkaline activator used. The high degree of immobilization is caused by formation of insoluble or poorly soluble lead and copper compounds in an alkaline environment while the insoluble compounds have been confirmed by SEM and XPS.

Effect of Admixtures on Durability Characteristics of Fly Ash Alkali-activated Material

This paper deals with the possibility of partial replacement of blast furnace slag with fly ash and fly ash after denitrification by SNCR method in alkali-activated materials based on granulated blast furnace slag. The aim of this paper is to verify the effect of fly ash on properties of alkali-activated materials based on blast furnace granulated slag. Frost resistance and resistance to aggressive environments, represented by demineralized water were tested. The reference mixture was based on blast furnace granulated slag activated by sodium water glass with silicate modulus of 2. Mixtures with an ash content of 10, 20, and 30% were then compared with the reference mixture. The influence of the denitrification process on fly ash and its use in mixed alkali activated materials was also compared. As a part of the experiment, alkali-activated pastes were also prepared. Infrared spectroscopy with Furier transformation was subsequently determined on these pastes. The reference mixture achieved the highest compressive strength in the experiment and the strength decreased with increasing amount of fly ash. In terms of flexural strength, the highest values were reached for mixtures with 10% slag replacement by fly ash. In the case of frost resistance, the significant increase of flexural strength, which was 50% for the reference mixture, is particularly interesting. For compressive strength, the frost resistance coefficient ranged from 0.95 to 1.00. In the case of resistance to aggressive environments, no differences were observed in the compressive strength, on the other hand, flexural strength decrease of up to 20% was detected for 10 and 20 percent replacement of slag with fly ash that did not undergo denitrification. Monitored properties did not show any negative effect of the denitrification process on fly ash properties. Infrared spectroscopy identified the main hydration product in the region of 945 cm-1which is a C-(A)-S-H gel and in combined mixtures with fly ash also N-A-S-H gel. Doi: 10.28991/esj-2020-01247 Full Text: PDF

A comparative study of the compressive strengths and microstructural properties of geopolymer cements from metakaolin and waste fired brick as aluminosilicate sources

The main target of this work is to compare the compressive strengths and the microstructural properties geopolymer cements from waste fired brick as low-value aluminosilicate-rich waste and metakaolin. The chemical reagent used in this investigation is a sodium waterglass from rice husk ash. The obtained results show that waste fired brick contains a higher amount of SiO2 (60.98 wt%). The quartz content in the waste fired brick, standard and local metakaolins was estimated at approximately 8, 2 and 8 wt%, respectively. The X-ray patterns of these aluminosilicates indicate the broad hump structure between 15 and 35° (2θ) corresponding to the amorphous aluminosilicate phase. Besides this amorphous phase, waste fired brick shows the broad bands of hematite at 33.29 and 35.87° (2θ) indicating that some Al is replaced by Fe in IV-fold coordination. The micrographs of metakaolins show the platy-shaped with coarse-grain particles and the one of waste fired bricks indicates the platy- and spherical-shaped with smaller particle sizes. The compressive strength values of geopolymer cements from local and standard metakaolins are 40.32 and 44.46 MPa, respectively. Whereas the one from waste fired brick is 47.82 MPa. It was found that waste fired brick could be used as an alternative low-value aluminosilicate-rich waste for producing geopolymer cements with high compressive strength.

МІЦНІСТЬ ПІЩАНО-РІДКОСКЛЯНИХ СУМІШЕЙ, ЩО СТРУКТУРУВАЛИ ПАРО-МІКРОХВИЛЬОВОЮ ОБРОБКОЮ

Мета. Встановлення закономірностей впливу умов плакування кварцового піску рідким склом, параметрів паро-мікрохвильового затвердіння і терміну зберігання суміші на величину її межі міцності при стисненні в структурованому стані.Методика. У дослідженнях використовували кварцовий пісок з вмістом глинистої складової не більше 0,5% за масою і переважним розміром піщинок 0,23 мм, плакований содовим натрієвим рідким склом з силікатним модулем 2,8...3,0 і питомою щільністю 1,43...1,46 г/см3. Для визначення навантаження руйнування структурованих сумішей при стисканні за способом паро-мікрохвильового затвердіння виготовляли зразки розмірами Ø 50×50 мм і Ø 30×30 мм. Випробування зразків проводили на приладі LRu-2e. Температуру сумішей вимірювали з похибкою ±1 °С.Результати. Встановлено, що межа міцності при стисненні в результаті тривалого зберігання плакованого піску навіть в герметично закритій тарі зменшується в 2...3 рази в порівнянні з свіжовиготовленою сумішшю, що, ймовірно, обумовлено частковою карбонізацією рідкого скла в плакованому шарі. Рекомендовано для структурування піщано-рідкоскляної суміші за способом паро-мікрохвильового затвердіння використовувати свіжовиготовлений плакований кварцовий пісок з температурою 20...26 °С. При цьому для плакування натрієвим рідким склом рекомендовано використовувати кварцовий пісок з вмістом води до 0,2 % (за масою) та вмістом вологи в затверділому рідкому склі не більше 2...3 % від маси гідратованого силікату натрію. Наведені описи та аналіз встановлених закономірностей.Наукова новизна. Вперше встановлено, що плакування кварцового піску рідким склом для його подальшого структурування способом паро-мікрохвильового затвердіння слід здійснювати при утриманні в піску вологи не більше 0,2 % (за масою) з наступним сушінням піску до вмісту вологи в затверділому рідкому склі не більше 2...3 % від маси гідратованого силікату натрію.Практична цінність. Отримані дані будуть корисними в ливарному виробництві, а саме в області формоутворення піщано-рідкоскляних сумішей.

Water Interactions in Hybrid Polyacrylate-Silicate Hydrogel Systems.

Hybrid polyacrylate-silicate hydrogels were obtained in the presence of N,N′-methylenebisacrylamide (NNMBA) as the cross-linking monomer and sodium thiosulphate/potassium persulphate (NTS/KPS) as the redox initiators. The results of the tests allowed us to conclude that a hybrid structure with a polyacrylate scaffolding and a silicate matrix had been obtained. The results of the rheological analysis revealed that the hydrogel sample with a 1:7 mass ratio of sodium water glass to the sodium polyacrylate is characterized by the highest complex viscosity. Thermal analysis (Thermogravimetry/Differential Scanning Calorimetry (TG/DSC)) showed that water begins to evaporate at higher temperatures, from 120 °C to even 180 °C. These results were confirmed by mid-infrared spectroscopy (MIR) and nuclear magnetic resonance spectroscopy (NMR) analysis. Differences in the intensity of the peaks derived from water in the MIR spectra indicate that most of the water is bounded. In turn, NMR results showed that the mobility of water molecules decreases as the amount of sodium water glass in the mixture increases.

Rheology behavior of one-part alkali activated slag/glass powder (AASG) pastes

Currently, one-part alkali activated materials (AAMs) show promising applications while the rheological characteristics remain unclear. Also, AAMs incorporating waste glass powder (GP) as part of the precursor have potentials for widely use, but their rheology behaviors have been rarely studied. In this study, the rheology behaviors of one-part alkali activated slag/glass powder (AASG) pastes prepared with a solid sodium water glass (Na-WG) as the activator were investigated and compared with those of ordinary Portland cement (OPC) pastes. Meanwhile, other properties of the pastes including microstructure, workability, setting time and compressive strength were also evaluated. The effects of water to binder (W/B) ratio, activator to binder (A/B) ratio, GP content and the addition of admixtures including calcium aluminate cement (CAC) and silica fume (SF) were systemically quantified. The results showed that the plastic viscosity of the AASG pastes were much higher than that of OPC paste with the similar flow value, but the yield stress of OPC paste was much higher when using the same W/B ratio. The plastic viscosity of the AASG paste increased with the increase of A/B ratio. The yield stress and plastic viscosity of the AASG paste decreased with the increase of GP content. The addition of SF was effective in increasing the yield stress and decreasing the plastic viscosity of the AASG paste due to its fine particle size and spherical morphology.

Development of Maize Stalk Cellulose Fiber Reinforced Calcined Kaolinite Clay Geopolymer Composite

In recent years the popularity of ecological and renewable materials has grown. Aware of the availability of local resources and economic grounds, the attention is paid to the development geopolymer composite. Geopolymers are inorganic polymers that are formed by the polymerization reaction of silico-aluminate and silico-oxide. The aim of the research was to develop single maize stalk cellulose fiber reinforced calcined kaolinte caly based geopolymer composite. Kaolinite clay was characterized for its chemical composition from two different sites located in Ethiopia to use as precursor material. In addition to that, single maize stalk fiber was extracted from the maize stalk local variety by using a retting process, sodium hydroxide purity 98 % used for chemical treatment of the fiber for 30 minutes and its tensile strength 1184 Mpa and young modulus 16 Gpa were determined based on AST M D3822 to use as reinforcement. Sodium hydroxide and sodium silicate in appropriate ratio were used as an alkaline activator. Therefore, the geopolymer composite developed from chemical treated short single maize stalk cellulose fiber and calcined kaolinite clay based geopolymer matrix activated by sodium water glass. Geopolymer composites reinforced with 0 weight%, 0.1 weight%, 0.2 weight%, 0.6 weight%, and 1 weight% maize stalk single cellulose were prepared and tested for compression strength according to AST M C 1424. Measured compression strength ranged from 16 Mpa up to 27 Mpa. The result shows that the appropriate addition of single maize stalk cellulose fibers can improve the Compression strength of a calcined kaolinite based geopolymer