Silicate Modulus Research Articles

Interpretation of the early stiffening process in alkali-activated slag pastes

To better understand early stiffening of AAS pastes, distinctive microstructural features by varying the silicate modulus (Ms) have been visualized with in-situ microscopy. In addition, the activation reaction was monitored with multiple approaches, while solid and liquid phases in hydrating AAS were characterized separately. In silicate-activated AAS, it was found fine granules of reaction products are intensively dispersed in the activator solution, leading to a less flocculated system. Compared to hydroxide-activated AAS, the development of interparticle connections was limited at early ages, whereas reaction products were detected with much smaller grain size, less crystalline phase, and higher Al incorporation. Results indicate that the stiffening of hydroxide-activated AAS is attributed to the formation of a well-percolated network through solid reaction products. Instead, massive fine granules of reaction products dispersed in the pore solution continuously develop, which may intensify the interparticle interactions and macroscopically results in the stiffening of a silicate-activated AAS.

Study on the synthesis mechanism of sodalite, gismondine, and zeolite-P1 zeolite materials from ladle furnace slag and fly ash

In this study, geopolymers were prepared using ladle furnace slag (LFS) and fly ash (FA), and hydrothermal treatment was then used to synthesize bulk zeolite molecular sieves with gismondine, zeolite-P1, and sodalite phases. The effect of the synthesis conditions on the crystalline phases of the zeolite molecular sieves was investigated by XRD. The results showed that the best zeolite molecular sieves were prepared with an LFS: FA ratio of 4: 6, a curing temperature of 40 °C, a curing time of 12 h, a sodium silicate modulus (Ms) of 1.4, a NaOH concentration of 4 mol/L, a hydrothermal temperature of 120 °C, and a hydrothermal time of 12 h. On this basis, the products were analyzed by SEM, N2 adsorption, and FT-IR. The results showed that the synthesized zeolite molecular sieves had mesoporous properties, and the degree of polymerization and cross-linking of the silica-aluminate gel were enhanced after hydrothermal treatment. In addition, the formation mechanism of the zeolite molecular sieves was explored through the changes of the silica-alumina during zeolite formation. This paper is the first to use the hydrothermal conversion of zeolite molecular sieves from LFS-FA based polymers to provide some guidance for the resource utilization of LFS and FA.

Preparation and Properties of Double Liquid Grouting Materials (DLGMs) Used for the Regenerated Roof of a Coal Mine

Double liquid grouting materials (DLGMs) are composed of slurry A and slurry B. In response to the need for sustainable development, there is currently a focus on improving the utilization rate of resources. In this paper, industrial solid waste fly ash, slag, and ordinary Portland cement were used to prepare slurry A, while sodium silicate was used as slurry B. Slurry C was made by adding slurry B to slurry A. The mix design parameters of the DLGMs, with large amounts of fly ash, were optimized based on the response surface method. The results showed that the relative content of cement and the reactivity and morphological effect of supplementary cementitious materials (fly ash and slag) were the main factors affecting the operable time, viscosity, and stability of slurry A. The relative content of cement and the sodium silicate modulus were the main factors affecting the operable time of the DLGMs. Compared to the C30F70S0-Z3.3 group (where C, F, S, and Z represented cement, fly ash, slag, and sodium silicate modulus, respectively), the operable time of the C0F70S30-Z3.3 group increased by approximately 36 min. As the sodium silicate modulus was lowered to 2.3, the operable time of the C0F70S30-Z2.3 group increased by about 32 min compared to that of the C30F70S0-Z2.3 group. The established model and response surface can well reflect the influence of multiple factors on the properties of the DLGMs. When the mass ratio of cement/fly ash/slag in slurry A was 7.5%: 70%: 22.5%, and the sodium silicate modulus and content of slurry B were 2.8 and 10%, respectively, the 28-day compressive strength of the DLGMs can reach up to 11.3 MPa. The content of fly ash was the most significant factor affecting the 28-day compressive strength of the DLGMs, followed by the sodium silicate content. The least influential factor was the sodium silicate modulus. The XRD and SEM results showed that a large amount of Ca2+ produced by cement hydration can quickly react with [SiO4]4- in sodium silicate to form C-S-H gel. Moreover, it also promoted the hydration of C3S and C2S in grouting to produce more C-S-H gel, which was conducive to the alkali activation of slag and fly ash, resulting in a denser microstructure and hence, yielded obvious increases in the compressive strengths of the DLGMs.

Preparation of building insulation foam materials by recycling industrial and agroforestry wastes

Energy shortage and environmental pollution have aroused widespread attention in the social circle. By combining industrial (waste photovoltaic glass powder (WPGP) and blast furnace slag (BFS)) and agroforestry wastes (rice husk ash (RHA) and plant ash (PA)) with alkali activator, 14 kinds of building insulation foam materials (BIFM) were prepared for the first time. The dry density, thermal conductivity, compressive strength, volumetric water absorption, pore parameters and microstructure of BIFM were tested. The effects of Na2O content, sodium silicate modulus and RHA content on the above indexes were discussed. The relationship among dry density, thermal conductivity and porosity of BIFM was discussed. The CO2 emissions and energy consumption of 14 kinds of BIFMs were estimated using a simplified method. The test results showed that the effects of Na2O content and sodium silicate modulus on the properties of BIFM were complementary. When the mass fraction of RHA was 15%, sodium silicate modulus was 1.4, and Na2O content was 8%, the optimum thermal conductivity was 0.0497 W/(m·K). Encouragingly, BIFM was beneficial in terms of both energy consumption and carbon footprint compared to traditional building insulation materials. The prepared BIFM can be used as a promising building insulation material.

New insights into the early-age reaction kinetics of metakaolin geopolymer by 1H low-field NMR and isothermal calorimetry

Early-age reaction kinetics of geopolymers is one of the challenging issues associated to their mechanical performances and durability. In this work, the early-age reaction of metakaolin geopolymer prepared by activators with various silicate moduli was studied. Compared to conventional methods, a novel approach was firstly proposed to evaluate the early-age reaction of geopolymer by using 1H low-field nuclear magnetic resonance (NMR) and isothermal calorimetry. The state and relative quantity of water in geopolymer pastes were detected by NMR during reaction process. While in this timescale, the heat release of pastes was recorded by isothermal calorimetry. A good consistency to the measurement of reaction process between these two testing methods can be observed. Activator with low silicate modulus (i.e., high alkalinity) deepens the reaction degree at the same timescale and the gel pore volume is increased with the alkalinity of activator. This method is useful to monitor the early-age reaction process of geopolymer, which is expected to offer new insights into the early-age reaction kinetics of geopolymer.

Development of new material for geopolymer lightweight cellular concrete and its cementing mechanism

Lightweight cellular concrete (LCC) is widely used in engineering and construction because of its low density and good thermal and acoustic insulation capabilities. However, cement production, the cementitious material for LCC, consumes much energy and emits large amounts of CO2. Therefore, reducing cement consumption is one of the main hot issues in the development of China's construction industry. The geopolymer cementitious material is one of the ideal substitutes for silicate cement because of its low energy consumption in production and its ability to give full play to the fly ash and slag activity under the action of alkali excitation. It is imperative to combine geopolymer with LCC to find a kind of lightweight and high strength building material, but there is still a lack of systematic research on this aspect. On the basis of exploring samples of geopolymer lightweight cellular concrete (GLCC), the influence of fly ash, slag content, sodium silicate modulus, alkali content, water cement ratio and other factors on the strength and fluidity of GLCC was analyzed by single factor (SF) test, and the reasonable value range of four factors was proposed. The significant effect of the four factors and the best matching ratio was derived through response surface (RS) test, and RS optimization prediction and validation were carried out. On the other hand, the cementing mechanism of geopolymer on LCC was analyzed from a microscopic perspective by comparing LCC and LCC filled with fly ash (LCCFFA) specimens with SEM tests.

Investigation of the effect of thermal-oxidative destruction of pyrocarbon on formation of structure of a binder and residual strength of sand-liquid-glass mixtures

A study of the effect of thermal-oxidative degradation of a carbon-containing additive on the formation of the binder film structure and the residual strength of sand-liquidglass mixtures after various calcination temperatures is presented. Pyrolyzed industrial carbon (pyrocarbon) of P324 grade was used as an additive. The methods of differential thermal and thermogravimetric analyzes were used to study the physical and chemical processes that occur with the investigated carbon-containing material when heated to a temperature characteristic of the heating of the surface layer of the core (molding) mixture in contact with liquid steel. This made it possible to reveal the temperature ranges of the degradation of the carbon-containing additive, which lead to a violation of the integrity of the sodium silicate film and a decrease in the residual strength of the sand-liquid-glass mixture. For a comparative analysis of the structure of silicate binder films and the residual strength of sand-liquid-glass mixtures after calcination at temperatures of 453, 673, 873, and 1073 K (180, 400, 600, and 800 °C), standard cylindrical samples from reference (quartz sand of 1K2O303 grade and liquid glass with a silicate modulus of 2.8, a density of 1490 kg/m3 as a binder) and experimental (with the introduction of pyrolytic carbon in the amount of 2 % (wt.)) mixtures have been prepared. As a result of the study, it was found that the residual strength of the studied sand-liquid-glass mixtures depends on the morphological features of the surface of the silicate binder film, expressed by the presence of carbonaceous formations (soot), pores and crystals of sodium carbonates (stress concentrators in the binder film).

Research on Recycling Various Wastes in Papermaking as Eco-Friendly Slurry

Waste recycling has always been a priority in the paper industry. In this study, the potential of translating various wastes in papermaking into building materials was separately evaluated. For the first time, the improvement of flexibility and sample texture after translating wastes into cementitious materials was analyzed. The results showed that 20% of the waste in alkali-activated slag slurry is the best proportion for papermaking. In addition, paper sludge and wood chips significantly improved the slurry flexibility while lime mud and bottom ash did not have this effect. Considering the effect of adding wood chips on the optimization of the sample texture, the most appropriate proportion of the paper sludge was 5% when the wood chips in the mixture were 15%. The most suitable alkali equivalent was 6%, with a silicate modulus of 0.9. According to the experimental results, wastes in papermaking had great potential for exploitation and application as circular materials.

Composition design and characterization of alkali-activated Slag–Metakaolin materials

This study explores the effects of the interactions among Na2O content, metakaolin content and activator modulus on the compressive strength and autogenous shrinkage of alkali-activated slag–metakaolin (AASM) materials. The Box–Behnken RSM design was used to create an experimental scheme, establish a model, and optimize the mix proportions. Fourier transform infrared spectroscopy, scanning electron microscopy, and Mercury intrusion experiments were used to analyze the compositions, microstructures, and pore structures of the hydration products of the AASM, respectively. Results showed that the interactions between the activator modulus and metakaolin content, as well as Na2O content and metakaolin content, are the key factors affecting the compressive strength and autogenous shrinkage, respectively, of the AASM. Under the optimal conditions of Na2O content of 6%, sodium silicate modulus of 1.5, and metakaolin/slag ratio of 1: 3, the relative errors in the model verification test for compressive strength and autogenous shrinkage are 0% and 0.18%, respectively. In the water glass modulus and metakaolin content interaction, Ca2+, A13+, and Si4+ ions in the composite system react with several [SiO4]4− groups to form C-A-S-H and N-A-S-H gels, which fill each other to make the composite structure denser. When Na2O interacts with metakaolin, the OH− and Na+ in the solution react with A13+ and Si4+ to generate additional N-A-S-H, thereby reducing the compressive strength of the composite system, mitigating autogenous shrinkage, and increasing volume stability.

Experimental Research on Mechanical and Shrinkage Properties of Alkali Activated Low-Carbon Green Concrete.

This paper describes orthogonal experiments to investigat the effects of content of fly ash and slag, sol ratio, modulus of sodium silicate and expander on the compressive strength and shrinkage of alkali activated low-carbon green concrete (AAGC) of different ages. The microstructures and hydration product compositions of AAGC with different proportions were further studied by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Mercury Intrusion Porosimetry (MIP). The results show that with an increase of fly ash content, the compressive strength of AAGC gradually decreases, the decline of compressive strength at 28 d is smaller than that of 7 d, and the shrinkage strain gradually increases at 28 d. As the sol ratio increases, the compressive strength increases first and then decreases. When the sol ratio is 0.42, the compressive strength is maximal at 28 d; the same is true for compressive strength at 7 d. Additionally, an increase of sol ratio can reduce the shrinkage strain at 28 d. Finally, when the sol ratio was 0.46, the shrinkage decreased by 30.5% compared with 0.40 at 28 d. As the modulus of sodium silicate (Ms) increases, the compressive strength first increases and then decreases. When Ms is 1.4, the compressive strength reaches the maximum. As Ms increases, the shrinkage strain decreases first and then increases at 28 d. When Ms is 1.0, the shrinkage strain is the maximum at 28 d. Finally, with an increase in the content of expander, the compressive strength decreases at 7 d and 28 d, and the shrinkage strain decreases at 28 d. The shrinkage strain at 28 d is the minimum with 9% content. AAGC mixed with a small amount of fly ash and expander has more hydration products and significantly reduced cracks. In addition, the proportion of small hole volume of AAGC increases, while the proportion of large hole volume decreases. AAGC mixed with fly ash and slag without expander has more unhydrated particles and its structure is loose.

Early properties and chemical structure analysis of alkali-activated brick geopolymer with varied alkali dosage

Alkali-activated brick powder geopolymer (BPG) was prepared by use of brick powder (BP) under the activation of sodium silicate-based activator with silicate modulus of 1.6 and alkali dosages of 2%, 4%, 6%, 8%, and the effect of alkali dosage on the early properties and reaction mechanism of BPG was studied in this paper. Results show that the BPG paste prepared with alkali dosage of 6% exhibits the best fluidity (180 mm). With increasing alkali dosage, the dissolution rate of Al from BP first increases and then decreases. The negative correlation exists between the setting time of BPG and the dissolution rate of Al from BP. The optimal compressive strength reaches 31.1 MPa at the alkali dosage of 6% after cured for 3 days (T = 70 °C, RH = 30%). Lower or excessive alkali dosage is both unfavorable to the enhancement of strength. The calorimetry, FTIR and NMR results show that the increase in alkali dosage (≤6% Na2O) improves the reaction degree, promotes the formation of network structures and increases the Al-rich structural units (Q4(3Al) and Q4(4Al)) due to the beneficial effect of alkali enhancement on dissolution of Al from BP, thereby increasing the polymerization degree of reaction products and enhancing the compressive strength of BPG. However, the higher alkali dosage (8% Na2O) impedes the further dissolution of Al and the formation of Al-rich structural units, which results in the lower reaction degree and compressive strength.

ZSM-5 as a support for Ru-containing catalysts of levulinic acid hydrogenation: Influence of the reaction conditions and the zeolite acidity

Levulinic acid (LA) is a substance, which can be obtained from cellulosic biomass and hydrogenated to gamma-valerolactone (GVL) – important platform chemical. This work describes the study of a ruthenium-containing catalysts synthesized by the impregnation of HZSM-5 having different silicate modulus (40, 80 or 400) with ruthenium precursor, which resulted in formation of oxidized Ru(III) and Ru(IV) species on the catalyst surface. Synthesized catalysts allowed more than 98% of LA conversion for 60 min of the reaction and 100% GVL selectivity while working at relatively mild conditions (100 °C, 1 MPa of H2) in aqueous medium. It was demonstrated that the observed catalytic activity mainly depends on two factors: (i) concentration of strong Lewis acid centers on the catalyst surface and (ii) surface content of RuO2, since the synthesized catalysts needed no preliminarily activation procedure.

Fresh and hardened properties of alkali-activated slag concrete: The effect of fly ash as a supplementary precursor

The present study explores the possibility of replacing blast furnace slag (BFS) with coal fly ash (FA) to produce alkali-activated material (AAM) concrete with hybrid precursors. With an increased FA replacement ratio, the reaction kinetics, fresh and hardened properties of AAM mixtures have been investigated. The retardation effect on the reaction kinetics with an increased FA content has been observed, which not only extended the induction period along with the heat flow evolution but also reduced the cumulative heat release up to 24 h. Spherical FA particles can provide a ball-bearing effect to improve the workability of the hybrid AAM mixtures, while FA also slows down the deterioration of fresh properties since they are less reactive compared to BFS particles. Regarding the strength development, FA results in the reduction at all curing ages in the mixtures with a low silicate modulus (Ms0.25). Similarly, reduction in 1-day compressive strength has been detected in high silicate modulus mixtures (Ms0.5) with FA replacement, while the mixture with 10% FA exhibits the highest compressive strength among Ms0.5 concretes at later curing ages. Bigger capillary pores have been detected in AAM mixtures with an increase in FA content. However, AAM with 10% FA shows the lowest porosity in Ms0.5 mixtures, which is in agreement with the compressive strength results.

Properties and environmental assessment of eco-friendly brick powder geopolymer binders with varied alkali dosage

This paper presents the effect of alkali dosage on the mechanical properties and water resistance of alkali-activated brick powder geopolymers (BPG) by measurements of compressive and flexural strengths, bulk density, water absorption and softening coefficient. To reveal the micro-mechanism of BPG under varied alkali dosage, the mineralogical phases, reaction degree, micromorphology, and pore structure of BPG are analyzed by techniques of XRD, TGA, SEM and MIP, respectively. Furthermore, the environmental impacts of BPG are evaluated by considering CO2-e emission and energy consumption. Results show that the BPG prepared with low alkali dosage (2% or 4% Na2O) exhibits the loose microstructure with few amorphous gels and relatively high porosity (including high proportion of capillary pores) resulting in the relatively poor mechanical properties and water resistance. However, a higher alkali dosage (6% or 8% Na2O) promotes the geopolymerization reaction resulting in the denser microstructure with more amorphous gels and relatively lower porosity, thereby greatly enhancing the mechanical properties and water resistance with maximal flexural strength, compressive strength and softening coefficient of 2.2 MPa, 31.1 MPa and 0.77 respectively. Water immersion may cause Na+ and OH− to dissolve from BPG matrix resulting in a charge imbalance of three-dimensional network structures, which will further lead to strength degradation. In comparison to ordinary Portland cement paste, BPG can reduce CO2-e emission by about 40%–70% and energy consumption by about 20%–50%. The optimal mixing parameters have an alkali dosage of 6%, a silicate modulus of 1.6 and a water-to-binder of 0.3 by considering the compressive strength and environmental impacts.

Improving the Fire-Retardant Properties of Cotton-Containing Textile Materials Through the Use of Organo-Inorganic SiO<sub>2</sub> Sols

The effect of fire-retardant compositions based on organo-inorganic SiO2 sols without the use of flame retardants on increasing the fire resistance of cotton-containing textile materials has been studied. Previous studies have shown that the combined use of silicate coatings and flame retardants of simple structure prevents the ignition of impregnated samples of cotton-containing fabric and the proposed chemistry of this process. These studies did not use flame retardants to obtain more information on the effect of the composition and concentration of experimental organo-inorganic SiO2 sols on the fire resistance of treated tissues. The compositions were prepared by the sol-gel method using a technical product – liquid glass – with a silicate modulus of 2,5 and acetic acid solution. The influence of sols concentration in terms of conditioned SiO2 on their rheological features has been studied. It was found that the optical density, fluidity and survivability of experimental sols depend on the concentration of SiO2 in the sol. The compositions were applied to the fabric by the bath method in layers: each layer of the coating was fixed on the surface of the fabric by thermal shock in an oven at temperatures of 80-100 °C. Untreated cotton fabric caught fire under the influence of fire after 7 seconds. Impregnated tissue samples did not ignite under the action of fire, but gradually charred. To determine the effect of coating thickness and SiO2 concentration in the sol on the fire resistance of impregnated fabric samples, fire tests at a gas pressure of 0,2 MPa were performed for 8 s and the area of damage to the reverse side of the fabric was determined. Prolonged exposure to the flame resulted in a crack in the center of the charred spot. In the absence of flame retardants in the fire-retardant composition after removal of the fire source, decay was observed. The time for which a crack is formed in the sample under the action of fire was determined at the time of onset of tissue destruction. It is shown that in the case of using a sol of 10% concentration it is necessary to apply three layers of coating, which doubles the fire resistance (from 7 s for untreated fabric to 15 s for impregnated fabric), the start time of destruction increases 5 times (from 1 min to 5,5 min). The area of damage to the reverse side of the fabric not treated and impregnated with the experimental coating is reduced from 632 mm2 to 0, respectively.

Stable solutions of orthosilicic acid

Soluble silicon plays a significant role in living organisms. Orthosilicic acid is the only bioavailable form of silicon. Sodium silicate solutions with various silicate moduli and different types of acids were used in our work to investigate the effect of silicate modulus and types of acids on the stability of the solutions of orthosilicic acid. It was determined that both the silicate modulus and the type of acid have a certain impact on the stability of orthosilicic acid solution. The effect of sulfuric, hydrochloric, orthophosphoric and methanesulfonic acid on the stability of orthosilicic acid solutions was studied depending on the silicate modulus of sodium silicate. It was shown that in the following series of anions SO42–, Cl–, CH3SO3–, PO43–, the stability of orthosilicic acid solutions increases. In the following series of alkaline modulus 3.02, 2.72, 2.06, 1.96, the stability increases too. The use of orthophosphoric acid and liquid glass with a silicate modulus of 1.96 allowed obtaining a solution, which is stable for at least 40 days.

Study of sorption processes for corn oil refining

Studies have summarized and analyzed the structure of an aqueous sodium silicate solution, which showed their dual nature. On the one hand, they exhibit the properties of electrolytes, and on the other hand, they contain monomeric alkali metal cations and polymeric silicon-oxygen anions. The use of an aqueous solution of sodium metasilicate with a silicate modulus equal to 1, in which polyanions predominate, is substantiated for the process of chemisorption purification of unrefined corn oil. A comparative analysis of the methods of purification of unrefined and hydrated vegetable oils pretreated in an electromagnetic field with solutions of organic acids and sodium silicate is carried out. Obviously, when purifying unrefined corn oil with an aqueous solution of sodium silicate, there is a complex mechanism of the sorption process with various groups of polar accompanying substances, complicated by chemical interactions. On the basis of planned experimental studies, adequate experimental-statistical models were obtained for calculating the soap content in the resulting corn oil and its yield, depending on the studied process parameters. It was found that in the studied range of temperatures and parameters of an aqueous solution of sodium silicate, corn oil is obtained according to the acid number corresponding to the Russian National Standard for refined corn oil. The optimal parameters of the chemisorption purification process in terms of temperature, concentration and dosage of sodium silicate with a silicate modulus equal to 1 are experimentally substantiated when the Reynolds criterion of the mixer is changed in the studied range from 4000 to 12000, ensuring the production of corn oil corresponding to the accepted quality parameters.

Understanding the workability of alkali-activated phosphorus slag pastes: Effects of alkali dose and silicate modulus on early-age hydration reactions

Understanding the workability of alkali-activated phosphorus slag (AAPS) pastes is fundamental for their efficient application. This study revealed the novel mutual inhibition mechanism through which the alkali dose and silicate modulus affect the workability of AAPS pastes based on the hydration reaction. The slump loss of NaOH-activated phosphorus slag (NAPS) paste was slow, and that of waterglass-activated phosphorus slag (WAPS) paste was faster because the soluble Si in waterglass accelerated the dissolution of the phosphorus slag (PS). At a moderate waterglass modulus, the slump losses of the WAPS pastes were slow because the moderate [Al]/{[Ca]+[Mg]} ratio in the pore solution minimized the difference in the magnitude of mutual inhibition between Ca, Mg and Al, causing all hydrates to form slowly. However, at higher and lower waterglass moduli, the WAPS pastes exhibited fast slump losses because hydrates with excess elements formed rapidly due to the excessively high or low [Al]/{[Ca]+[Mg]} ratio.

Early properties and microstructure evolution of alkali-activated brick powder geopolymers at varied curing humidity

Early properties, reaction products, chemical bonds and structural units of alkali-activated brick powder geopolymers (BPG) are studied by measurement of compressive strength, and by techniques of XRD, TG, FTIR and 29Si MAS NMR taking curing humidity as variable. The results show that the optimum compressive strength of BPG can reach 67.8 MPa with curing humidity of 60%, curing temperature of 70 °C and curing age of 3d, while the high curing humidity (RH: 85% or 95%) is unfavorable to the strength development of BPG. Microscopic test results show that increasing curing humidity (for mixes cured up to < 60% RH) causes the increases in chemically bound water and Al-rich structural units (Q4(3Al) and Q4(4Al)) resulting in the excellent compressive strength. However, high curing humidity (RH: 95%) reduces the chemically bound water and hinders the formation of Al-rich structural units (Q4(3Al) and Q4(4Al)) resulting in the poor compressive strength. The reduction in physically bound water is favorable to the strength development of BPG when the chemically bound water is comparable. This research work suggests that the relatively optimum silicate modulus, alkali dosage and curing humidity for the preparation of BPG are 1.6, 6% and 60%, respectively.

The Effect of Silicate Modulus on the Properties of Polypropylene Fiber-reinforced Geopolymer Composite Material

This study investigated the effect of the silicate moduli on the properties of the geopolymer materials consisting of Class F fly ash (FA) and ground granulated blast furnace slag (GGBFS). For this purpose, geopolymer materials were prepared with alkaline solutions composed of 10 M NaOH and sodium silicate solutions (SSs) with two different silicate moduli (2Ms and 3Ms). The geopolymer mixtures were placed in molds (40 x 40 x 160 mm) and cured at 90 °C for 5 hours. After heat curing, physical, mechanical, XRD, and SEM-EDS analyses were performed on 7-day samples. According to the findings, polypropylene fiber reinforcement improved the flexural and compressive strength of the samples with high GGBFS content. Also, according to SEM-EDS analysis, it was concluded that the higher the CaO content, the lower the compressive strength, and the higher the Al2O3 content, the higher the compressive strength. As a result, the 2Ms SS improved the compressive strength of the samples with higher FA content, while the 3Ms SS improved the compressive strength of the samples with more GGBFS than FA. 1.5% polypropylene fiber-reinforced 3Ms SS samples with 25% FA had the highest compressive strength.