Next Article in Journal
Adhesion of 3D-Printed Versus Milled Resin Posts to Composite Resin Core Build-Up Material: Influence of Surface Treatments
Previous Article in Journal
Medicago Sativa Stems—A Multi-Output Integrated Biorefinery Approach
Previous Article in Special Issue
Flexural Behavior of Thin Concrete Slabs Reinforced with Surface Embossed Grid-Type Carbon-Fiber Composites
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Polymers
Volume 17
Issue 12
10.3390/polym17121710
polymers-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Geopolymer Concrete Physical and Mechanical Properties on a Combined Binder Reinforced with Dispersed Polypropylene Fiber

by
Sergei A. Stel’makh
1,
Alexey N. Beskopylny
2,*,
Evgenii M. Shcherban
3,
Diana Elshaeva
1,
Andrei Chernilnik
1,
Denis Kuimov
4,
Alexandr Evtushenko
1 and
Samson Oganesyan
1
1
Department of Unique Buildings and Constructions Engineering, Don State Technical University, 344003 Rostov-on-Don, Russia
2
Department of Transport Systems, Faculty of Roads and Transport Systems, Don State Technical University, 344003 Rostov-on-Don, Russia
3
Department of Engineering Geometry and Computer Graphics, Don State Technical University, 344003 Rostov-on-Don, Russia
4
Department of Digital Technologies and Platforms in Electric Power Industry, Faculty of Energy and Oil and Gas Industry, Don State Technical University, 344003 Rostov-on-Don, Russia
*
Author to whom correspondence should be addressed.
Polymers 2025, 17(12), 1710; https://doi.org/10.3390/polym17121710
Submission received: 4 June 2025 / Revised: 12 June 2025 / Accepted: 18 June 2025 / Published: 19 June 2025
(This article belongs to the Special Issue Fiber Reinforced Polymers Applications as Reinforcement of Concrete Structures—Design Aspects, Tests and Analysis, 2nd Edition)
Browse Figures
Versions Notes

Abstract

Geopolymer concrete is a promising construction material that acts as an alternative to cement concrete. Unlike traditional cement concrete, geopolymers are environmentally friendly materials, the production of which does not involve significant carbon dioxide emissions. However, the structure formation and properties of geopolymers significantly depend on raw materials and are insufficiently studied. The aim of the study is to select the optimal combination of ground granulated blast furnace slag (GGBS) and fly ash (FA) as a binder and the optimal content of polypropylene fiber to create a sustainable, environmentally friendly and effective geopolymer concrete. To study various compositions of geopolymer binders selected by combining GGBS and FA, experimental geopolymer concrete mixtures and samples from them were manufactured. The density and slump of fresh concrete and the density and compressive strength of hardened composites were studied as mechanical characteristics. The microstructure of the geopolymer matrix was analyzed using optical and scanning electron microscopes. The most rational combination of GGBS 80% and FA 20% was determined, which allows obtaining a composite with the highest compressive strength of up to 31.5 MPa. A dispersion reinforcement study revealed that 0.8% polypropylene fiber (PF) is optimal. This allowed us to increase the compressive strength by 7.3% and the flexural strength by 48.7%. The geopolymer fiber concrete obtained in this study is a sustainable and environmentally friendly alternative composite material and has sufficient performance properties for its use as an alternative to cement concrete.

1. Introduction

The global demand for sustainable technological solutions in the construction industry is rapidly growing. The key and most popular building material in the field of civil and industrial construction is cement-based concrete [1]. Cement production is accompanied by emissions of a huge amount of greenhouse gases—up to 7% of global emissions [2]. The development of alternative environmentally friendly materials that can replace cement concrete is currently a relevant area of study. Geopolymer concrete is a building material with a reduced impact on the environment, comparable in its characteristics to cement concrete [3,4,5].
In the current literature, alkali-activated aluminosilicate binders are considered a promising replacement for Portland cement. The main advantages of these binders include the fact that the process of their preparation is quite economical and does not require calcination, firing and direct extraction of natural resources and their processing. The main raw material for their production is waste from the industrial and fuel and energy complex. This type of binder is also highly environmentally friendly and will reduce the carbon footprint [6,7]. However, despite the huge economic potential and environmental friendliness of aluminosilicate binders, there are several limitations that hinder their widespread use. First, this is the complexity of developing a binder formulation of optimal composition and the instability of the chemical composition of aluminosilicate components. Thus, the search for new formulation solutions and the development of optimal compositions of geopolymer binders for obtaining geopolymer composites with improved performance properties are relevant and are highly popular in the modern global materials science community [8,9,10].
The most popular aluminosilicate components for obtaining geopolymer binders are fly ash (FA), ground granulated blast furnace slag (GGBS) and other types of slag. Geopolymer mixtures on GGBS with a compressive strength of up to 62.6 MPa have already been developed [11]. In addition, a geopolymer composite based on GGBS with the addition of gypsum and NaCl has already been obtained, which significantly increased its compressive strength up to 82.3% and resistance to sulfide corrosion [12]. A combination of copper slag and 2% microsilica allowed us to obtain a geopolymer with a compressive strength of 79 MPa [13]. A combination of GGBS, rice husk ash and lightweight clay filler allowed us to obtain lightweight geopolymers with a density of up to 1868 kg/m3 and a compressive strength of up to 37.1 MPa [14]. The efficiency of using GGBS as a base for a geopolymer binder is also confirmed by several other studies [15,16,17,18]. Another popular aluminosilicate component is ash of various origins, including fly ash (FA). Previously, it was possible to obtain stable geopolymer concrete on FA with the addition of microsilica [19]. Ash from the incineration of solid municipal waste in combination with an alkaline activator of optimal composition exhibits the properties of a binder and allows obtaining a composite with a compressive strength of 43.7 MPa [20]. Correctly selected geopolymer composites on FA are actively used in 3D printing technology [21]. Similar experimental results confirming the effectiveness of FA in geopolymer concrete technology are reflected in several other studies [22,23,24,25,26,27]. Using multiple aluminosilicate components, including GGBS, in optimal combinations enables the creation of geopolymer composites with desired performance characteristics [28,29,30,31,32,33].
In general, most of the studies devoted to geopolymer composites are aimed at developing the optimal composition of the geopolymer binder and selecting the best composition of the alkali activator for it [34,35]. Using fiber to improve the properties of various types of composites is a popular formulation solution and is actively studied as one of the options for improving the strength properties of geopolymer concrete [36]. For example, the addition of steel fibers to geopolymer concrete made it possible to increase its compressive strength by 23.2% [37]. Basalt fibers show good results in the geopolymer’s structure, limiting its shrinkage cracks and improving strength properties [38,39]. Including steel fiber and polyvinyl fibers made it possible to increase the strength properties of the geopolymer when exposed to a temperature of 200 °C [40]. The study of the behavior of geopolymer concrete under the influence of high temperatures proves its competitiveness in comparison with cement composites in this indicator [41,42].
Polypropylene fibers, introduced into the composition of the geopolymer composite in an amount of 1%, also positively affect its properties, increasing the compressive strength by up to 18% [43]. Improving the mechanical properties and structure of geopolymer composites by adding polypropylene fibers has been proven previously [44]. The inclusion of 0.8% polypropylene fibers in the composition of geopolymer concrete for 3D printing has increased its strength properties and improved plasticity [45]. Also, the addition of polypropylene fibers improves the performance characteristics of geopolymer concrete, counteracting the penetration of chlorides [46]. The positive effect of dispersed reinforcement of geopolymer composites with various types of fibers has been proven in several other studies [47,48,49]. The development of new types of sustainable geopolymer concretes using various types of man-made waste is highly relevant, especially for those regions where there is a problem of industrial waste accumulation. It is important to note that the development of several types of waste combinations in the geopolymer composition is the most desirable result. However, the development of such compositions is quite complex and requires a large amount of experimental research aimed at studying the properties of the waste itself and the properties of finished composites. To achieve geopolymer concrete with the required operational properties based on waste, it is necessary to search for many various formulations and technological solutions, which significantly limit the geopolymer concrete usage in construction practice. Thus, based on the results of the review, a deficit of works was established in which the effect of polypropylene fiber on the structure formation and characteristics of geopolymer concrete on a combined binder was studied [11,25]. The main gaps in the research are in studying the effect of reinforcement of geopolymer concrete with polypropylene fiber on a combined binder and obtaining the dependencies of the properties of such concrete on the parameters of its composition from precursors of local origin.
Thus, the scientific novelty of the work lies in studying the structure and obtaining new dependencies of the properties of geopolymer concrete on a combined binder based on GGBS and FA and dispersed-reinforced with polypropylene fiber of local origin on the parameters of the composition.
The objective of this study is to select the optimal combination of ground blast-furnace granulated slag and fly ash as a binder and the optimal content of polypropylene fiber to create a sustainable, environmentally friendly and effective geopolymer concrete. Based on this, the following tasks were formulated:
−
Development of experimental compositions of geopolymer concrete on a combined binder with different ratios of GGBS and FA and selection of the optimal dosage of polypropylene fiber;
−
Production of fresh geopolymer concrete on a combined binder and control of its density and slump;
−
Production of geopolymer concrete samples and evaluation of its density and compressive and flexural strength. Analysis of the structure of geopolymer composite reinforced with polypropylene fiber;
−
Analysis of the experimental results and selection of the most optimal formulation of geopolymer fiber-reinforced concrete, allowing us to obtain a composite with the required performance properties;
−
Development of recommendations for the practical use of the obtained geopolymer concrete reinforced with dispersed polypropylene fiber.

2. Materials and Methods

2.1. Materials

Ground blast furnace granulated slag (GGBS) (Severstal, Cherepovets, Russia) and fly ash (FA) (Novocherkassk GRES, Novocherkassk, Russia) were used as the major components for the aluminosilicate binder. The chemical composition of GGBS and FA and their appearance are presented in Table 1 and Figure 1, respectively. The chemical composition of FA and GGBS was provided by suppliers.
Quartz sand (QS) (Nedra, Samarskoye village, Russia) was used as a fine aggregate with the following characteristics: bulk density—1402 kg/m3; apparent density—2594 kg/m3; the content of dust and clay particles—0.03%; content of clay in lumps—0.05%; no organic and contaminant content.
Crushed granite (CrS) (Pavlovsk Nerud, Voronezh, Russia) was used as a coarse aggregate with the following characteristics: bulk density—1435 kg/m3; apparent density—2663 kg/m3; resistance to fragmentation—11.0 wt %; content of plate-like and needle-like grains—5.2 wt %.
The distribution curves of GGBS, FA, QS, CrS particles are shown in Figure 2.
Based on the analysis of the curves in Figure 2, it was established that the main share of GGBS particles, 82.5%, ranges in size from 30 to 150 μm. The majority (81.4%) of FA particles are sized between 10 μm and 60 μm. Fine filler QS has a fineness modulus of 1.82. Coarse filler has a grain size of 5 to 20 mm.
The particle size affects the density of the composite structure during the geopolymerization reactions and the water requirement of the mixture, which affects the characteristics of geopolymer concrete, so it is important to select such granulometric compositions of the components that will ensure dense packing of particles by filling intergranular voids, and without additionally increasing the water requirement of the mixture.
Sodium hydroxide (NaOH) (Khimprom, Novocheboksarsk, Russia) was used as an alkaline activator.
Polypropylene fiber (Armplast, Taganrog, Russia) with the following characteristics was used for dispersed reinforcement: fiber diameter—12 μm; fiber length—12–16 mm; tensile strength—320 MPa; density—0.91 g/cm3.

2.2. Methods

Development of the optimal composition of geopolymer fiber concrete on a combined binder included two main stages. First, the optimal ratio of GGBS and FA in the concrete composition was selected. Second, the optimal percentage of reinforcement of the PF geopolymer composite was selected. In the first stage, 6 compositions of geopolymer concrete were developed (Table 2). The percentage ratio of GGBS and FA varied with an interval of 20%. The optimal amount of NaOH and water for preparing the alkaline activator was determined by calculation during the selection of the composition of geopolymer concrete.
The program of the first stage of experimental research is presented in Figure 3.
In the second stage of experimental studies, 6 compositions of geopolymer concrete with different PF content were developed. The formulation of geopolymer fiber concrete and the experimental study program are presented in Table 3 and Figure 4, respectively.
The study adopted a range of fiber dosages from 0.2 to 1.2% due to the analysis of the previously published literature concerning the use of polypropylene fiber in geopolymer concrete and preliminary test experiments conducted by the authors earlier, which revealed the inappropriateness and irrationality of expanding the range, due to a noticeable deterioration in the performance of the finished composite [18,25,45,46,50,51].
Preparation of fresh geopolymer concrete and molding of experimental samples both at the first and second stages of the experimental study was carried out in a similar manner and included the following main stages: dosing of all raw materials according to the recipe; preparation of an alkaline solution (an alkaline solution with a NaOH concentration of 14.18% was prepared 24 h before use); GGBS, FA and QS were poured into a mixer and mixed dry for 60 s; then the alkaline solution was poured in and everything was mixed until smooth; CrS was added to the finished geopolymer mixture and was mixed until smooth. PF was added at the very end, and the mixture was additionally mixed; the finished geopolymer concrete mixture was unloaded from the mixer and poured into cube molds and prism molds in 3 stages; at each stage, the mixture was additionally compacted using a bayonet; then the filled forms were placed on a laboratory vibration platform SMZh (Imash, Armavir, Russia) and compacted for 60 s; after compaction, the surface of the samples was smoothed, and they were kept in the molds for 10 h, after which they were subjected to heat and moisture treatment (steaming was carried out for 10 h, the temperature of isothermal heating was 85–90 °C); after heat and moisture treatment, the samples were cooled and removed from the molds; then they were placed in a normal hardening chamber until they reached the age of 28 days. The curing conditions in such a chamber were as follows: temperature 20 ± 2 °C, relative humidity 95 ± 5%.
Unlike Portland cement concrete, the hardening rate of geopolymer concrete largely depends on the composition of the grout (alkaline activator), and with a correctly selected composition of the alkali activator, the presence of additives that accelerate hardening and heat treatment, the geopolymer can sometimes gain design strength faster than Portland cement concretes. However, in most current studies devoted to slag-based geopolymer concretes, the optimal hardening time for them, like Portland cement concretes, is considered to be 28 days [52,53].
This mode of heat and moisture treatment was chosen after analyzing previously obtained data [54,55,56], where the efficiency of heat and moisture treatment of geopolymer binders and concretes based on them was explained by the fact that at high curing temperatures, Ca, Al and Si react more quickly with water and form a high-density CASH gel.
Polypropylene fiber was introduced into the finished geopolymer concrete mixture. The fibers were divided into approximately 3 equal parts; each part was evenly scattered over the entire surface of the mixture and mixed for 30 s. This operation was repeated and ensured the most uniform distribution of fiber throughout the entire volume of the mixture. The homogeneity of the fiber dispersion was checked on fresh geopolymer concrete samples and hardened specimens after strength tests, both visually and using an optical microscope.
Preliminary holding in molds and steaming were conducted in order to intensify the rate of geopolymer reactions. GGBS and FA are pozzolanic active mineral substances, and as is known, their hardening rate is slower in comparison with Portland cement [57].
The slump of the cone and the density of freshly made concrete mixtures were determined in accordance with the method requirements [58]. To determine the slump, a cone, a metal sheet and a ram, previously wiped with a damp cloth, were used. The cone was placed on the sheet and filled with the mixture in 3 stages. Each layer was compacted with 25 blows of the ram. After compacting the mixture, its excess was cut off with a ruler. The cone was raised up and placed nearby. Then the slump of fresh geopolymer concrete was measured. The density, compressive strength and flexural strength of geopolymer concrete and fiber concrete were determined according to the methods [59,60,61,62,63,64,65]. Cube samples were first used to determine the density and then to determine the compressive strength. First, their geometric sizes and weights were measured. Then the samples were installed in the Press P-50 laboratory unit (IMASH, Armavir, Russia). The load was applied at a rate of increase of 0.6 ± 0.2 MPa/s. Before testing, the geometric parameters of the prism samples were measured and then installed in a special laboratory setup and loaded at a rate of increase of 0.05 ± 0.01 MPa/s. The results obtained during the tests were processed using the formulas presented in Table 4.
In total, 18 cube samples were made during the first stage of experimental studies to determine the efficiency of the newly developed geopolymer concrete compositions in terms of density and compressive strength. In the second stage of experimental studies, 36 samples were made, including 18 cube samples and 18 prism samples, to evaluate the efficiency of PF dispersed reinforcement. Granulometric analysis of aluminosilicate components and fillers was performed using a Microsizer 201C laser particle analyzer (VA INSALT, St. Petersburg, Russia) and laboratory sieves. The structure of geopolymer concrete and fiber concrete was studied using an MBS-10 optical microscope (Izmeritelnaya Tekhnika, Moscow, Russia) at a magnification of 10 times. The microstructure of the geopolymer matrix was studied using a Tescan scanning electron microscope (Brno, Czech Republic) with an Inca Energy 450/XT electron probe microanalysis system. The images were obtained in backscattered electrons (BEs) or secondary electrons (SEs). Areas with a higher average atomic weight (relatively enriched in heavy elements) are colored in lighter shades. In BEs, areas with a higher average atomic weight (relatively enriched in heavy elements) are colored in lighter shades.

3. Results and Discussion

3.1. The Performance of Geopolymer Concrete Evaluation on a Combined Binder

Figure 5 and Figure 6 show the results of determining the density ( ρ f c ) and the slump of fresh geopolymer concrete, respectively.
According to the data on determining the density of fresh geopolymer concrete (Figure 5), a change in the content of aluminosilicate components GGBS and FA in the binder does not significantly affect the density of the geopolymer concrete mix. Deviations from the control composition of type 100G/0F varied from 0.1% to –0.7%.
As can be seen from Figure 6, the highest value of fresh geopolymer concrete slump was recorded for the composition of type 100G/0F, where GGBS was the main component of the binder. The lowest slump value is for the composition of type 0G/100F. The slump of the 0G/100F composition on the FA binder is 53.3% less than that of the 100G/0F composition. With an increase in the proportion of FA in the combined binder, the slump in the mixtures decreases. For the 80G/20F, 60G/40F, 40G/60F and 20G/80F type compositions, the slump values decreased by 6.7%, 13.3%, 20.0% and 40.0%, respectively. The decrease in the slump of the geopolymer concrete mixture with an increase in the FA content is explained by the fact that FA particles have a higher water demand compared to GGBS due to their smaller size. Based on the analysis of the particle distribution curves, it was found that the main share of GGBS particles varies in the size range from 30 to 150 μm, and FA particles in the range from 10 μm to 60 μm. More alkaline activators will be spent on wetting the FA particles, which they absorb from themselves from the total volume of the mixture, thereby reducing their workability. For 20G80F and 0G100F, the drop becomes more abrupt due to the fact that the proportion of FA increases by four or more times compared to GGBS, which leads to a sharp increase in the water demand of the mixture due to the smaller size of FA particles compared to GGBS. Much more alkaline activator will be spent on wetting the FA particles, which they absorb from the total volume of the mixture, thereby significantly reducing the sediment of the mixture [66,67]. Further, Figure 7 and Figure 8 present the results of determining the density (ρ) and compressive strength (Rgc) of geopolymer concrete, respectively.
As with the density of fresh geopolymer concrete, the density of the hardened composite changed insignificantly. Deviations from the 100G/0F composition ranged from 0.1% to –0.8%. Changing the ratio of GGBS and FA in the geopolymer binder does not significantly affect the density of the concrete composite since the bulk density of the applied GGBS and FA differs insignificantly in dry form.
Based on the results of determining the compressive strength, shown in Figure 8, it was found that geopolymer concrete on a combined binder consisting of 80% GGBS and 20% FA has the highest strength. The compressive strength of the 80G/20F composition was 17.5% higher than that of the 100G/0F composition. The combination of 80% GGBS and 20% FA allows us to obtain a geopolymer binder system with the most rational combination of Ca/Si. It is the content of these elements that is responsible for the activity of geopolymerization reactions and the amount of formed hydrosilicate gel (CSH), which binds all raw materials and directly affects the strength of geopolymer concrete. Further, as the proportion of GGBS decreases and the proportion of FA increases, a negative effect is observed, which is associated with a decrease in the amount of formed CSH [68,69,70]. Further, as the proportion of GGBS decreased and the proportion of FA increased, a negative effect was observed. The compressive strength of the 60G/40F, 40G/60F, 20G/80F and 0G/100F compositions was lower by 6.0%, 14.2%, 19.0% and 33.2%, respectively. The appearance and nature of the destruction of geopolymer concrete of the 80G/20F type composition are shown in Figure 9.
The sample of geopolymer concrete shown in Figure 9 has a yellow-gray tint. Failure occurred mainly in the central and left side parts of the sample.
The reason that the 80G/20F composition has the highest compressive strength is that this geopolymer system has a denser hydrosilicate gel (CSH) with a high Ca/Si content, which actively fills all the voids at the interface of all raw materials. Accordingly, geopolymer systems with lower compressive strength have less dense CSHs and a low Ca/Si content. An increase in the FA content in this system reduces the reactivity. Also, a number of other studies have shown that alkali-activated pastes based on GGBS, as a rule and in most studies, have higher strength than alkali-activated FA pastes based on fly ash [68,69].
The obtained result in the selection of the optimal composition of the geopolymer combined binder is consistent with many other studies, where the authors also managed to develop effective and environmentally friendly geopolymer composites by combining various aluminosilicate components in the binder (Table 5).
Combining GGBS and FA allowed us to select a geopolymer binder with the optimal composition. With a combination of 80% GGBS and 20% FA, geopolymerization reactions proceed most intensively, and a greater amount of CSH is formed, which directly affects the final strength of the composite. The 80G/20F composition was accepted as the most effective and was taken as a basis for further study of the effect of dispersed reinforcement with polypropylene fiber.

3.2. Assessment of Geopolymer Concrete Performance on a Combined Binder Reinforced with Polypropylene Fiber

Figure 10 and Figure 11, respectively, show the results of determining the compressive strength R f g c and flexural strength R b t of geopolymer concrete with PF.
The dependencies presented in Figure 10 and Figure 11 are well approximated by polynomial functions of degree 4 and 3, respectively:
R f g c = 31.53 − 1.011   x + 13.23   x 2 − 12.44   x 3 + 1.42   x 4 ,             R 2 = 0.95
R b t = 3.92 + 2.305   x + 1.577   x 2 − 2.430   x 3 ,             R 2 = 0.938
here x is PF content, %; R2 is the coefficient of determination.
Figure 10 shows that the introduction of PF into the concrete composition has a positive effect on the strength of the geopolymer composite. With a PF content of 0.2% to 0.8%, a stable increase in compressive strength is observed. The maximum compressive strength was recorded at 0.8% PF, the increase was 7.3%. Then, with a content of 1.0% and 1.2% PF, an inverse relationship is observed: the efficiency of dispersed PF reinforcement decreases. With 1.0% PF, the compressive strength is 3.2% higher than the control composition, and with 1.2% PF, the compressive strength is 1.9% lower.
As can be seen from Figure 11, geopolymer concrete with PF from 0.2% to 0.8% has a stable trend to increase flexural strength. The maximum value of the increase in bending strength was recorded at 0.8% PF and amounted to 48.7% compared to the control composition. The efficiency of dispersed reinforcement decreases for higher PF contents—1.0% and 1.2%. The increases in bending strength were 33.3% and 23.1%, respectively.
The decrease in the efficiency of dispersed reinforcement with the introduction of 1.0% or more PF occurs due to the supersaturation of geopolymer concrete with fiber. Too high dosages of dispersed reinforcing fiber lead to the fact that, at the manufacturing stage, these fibers cannot be evenly distributed throughout the entire volume of the composite and clump. In areas where such formations are present, there will be reductions in strength. The presence of such zones negatively affects the properties of the composite, and the effect of dispersed reinforcement is reduced or even leads to deterioration of the properties of geopolymer composites [35,75].
Thus, based on the results of determining the compressive and bending strength of geopolymer concrete on a combined binder, it was found that dispersed PF reinforcement has a positive effect on these properties. The introduction of PF into the composition of geopolymer concrete up to 1% has a positive effect on compressive and bending strength. At higher dosages, an inverse relationship is observed in the form of a decrease in strength properties. The PF content of 0.8% is optimal for this type of geopolymer concrete. PF, introduced into the geopolymer composite in an optimal amount, is distributed uniformly throughout its volume and promotes the creation of macrostructural cells, where fiber fibers additionally bind together the binding components, sand and crushed stone. Due to the formation of these macrostructural cells, dispersed-reinforced geopolymer concretes better resist the effects of destructive loads. However, discrepancies arise in the operational mechanisms of PF within the composite structure when evaluating compressive and flexural strengths. The mechanism of PF operation under compressive load can be described as follows. Fibers have a chaotic distribution in the composite body, part of the stresses from the compressive load are perceived by themselves and additionally hold the structure of the composite in all directions [76]. Under the action of a bending load, fibers also perceive part of the stresses and resist it until complete destruction. It is this difference in the features of the fiber operation mechanism that explains the higher increases in bending strength compared to compressive strength. The PF content above the norm leads to a negative effect. The fibers cannot be distributed normally and evenly throughout the entire volume of the composite. They clump together, forming zones of low strength, which lead to a weakening of the entire structure of the geopolymer composite. In general, the use of various types of fiber in geopolymer composite technology is a popular formulation solution [77,78]. The results obtained in this section of the study are in good agreement with the works of other authors (Table 6).
Dispersed reinforcement of the PF geopolymer composite in the amount of 0.8% of the combined binder mass is a rational formulation solution and allows obtaining geopolymer concrete with additionally improved strength properties.
Figure 12 and Figure 13 show the microstructure of geopolymer paste of composition 80G/20F without PF and with 0.8% PF.
The geopolymer matrix based on the mixture of 80% GGBS and 20% FA has a well-compacted microstructure (Figure 12b and Figure 13b), and a large amount of gel-like products of the geopolymerization reaction is observed. No unreacted GGBS and FA particles are recorded in Figure 12 and Figure 13. It is noted that the geopolymer matrix samples studied after the action of compressive destructive loads have characteristic microcracking (Figure 12a and Figure 13a), represented by thin and short microcracks. The PF at the fiber–matrix interface is pulled out of the matrix structure and deformed under the action of destructive loads. The nature of the destruction at the fiber–matrix interface indicates a sufficiently good adhesion of the matrix and fiber.
Further, in Figure 14 and Figure 15, an analysis of the structure of the geopolymer composite of the 80G/20F type without PF and with 0.8% PF is presented. The photographs were taken at 10× magnification.
The geopolymer concretes shown in Figure 14 and Figure 15 have a fairly uniform structure. The contact zone between the fillers and the geopolymer binder is visually dense, indicating a well-organized structure without noticeable defects (Figure 14b). The PFs are distributed uniformly and are partially extended from the geopolymer matrix, which indicates the standard nature of destruction and deformation of fibers under compressive and bending loads (Figure 15) [79,90,91]. Figure 15 shows the contact zone at the phase boundary between the fiber and the geopolymer binder, and the microcracks that formed in the composite structure during its destruction. The combination of GGBS and FA in optimal quantities and their different granulometric compositions, where for GGBS the main share of particles falls in the range from 30 to 150 μm, and for FA from 10 μm to 60 μm, made it possible to obtain the densest and strongest structure. FA particles are smaller than GGBS particles, and due to this, they can fill the voids between them, and thus, a denser composite structure is created during the geopolymerization reactions [72,91,92,93]. Thus, the conducted study of the structure confirms the obtained dependencies of the characteristics of geopolymer concrete on a combined binder based on GGBS and FA, dispersed-reinforced with polypropylene fiber, on the parameters of its composition.
The results of this experimental study reflect the following specific results:
-
Qualitative and quantitative characteristics of the feedstock for its further use in geopolymer concrete technology were determined;
-
The most rational compositions of the geopolymer binder system for obtaining highly effective geopolymer concretes were obtained;
-
The optimal composition of the geopolymer binder was selected by combining 80% GGBS and 20% FA with a compressive strength of 31.5 MPa;
-
The optimal PF content of up to 0.6–1.0% was selected for dispersed reinforcement of geopolymer concrete.
The obtained results develop and complement the theoretical and experimental dependencies of the global science of geopolymer composites [51,55,81]. The obtained geopolymer concrete has sufficient strength properties for its extensive use in real construction practice. The developed geopolymer fiber concrete can be actively used both for the manufacture of various factory-made products and in construction site conditions. The main advantages of this geopolymer fiber concrete include its high environmental friendliness, low carbon impact on the environment and cost-effectiveness. Using slag and ash for manufacturing concrete simultaneously allows for solving several problems. The problem of recycling industrial and fuel and energy complex waste is solved, the rejection of cement will significantly reduce the cost of concrete production and, at the same time, solve the problem of reducing the carbon impact [93,94,95]. However, it is worth noting the limitations of this study, which are primarily associated with the features of the aluminosilicate components used to manufacture the binder. Depending on the location and technology of the industrial enterprise, the waste it receives in the form of slag and ash can vary greatly in chemical composition, which makes the developed recipe limited, and its practical use with aluminosilicate components of other origins may not be as effective and will require additional adjustment of the composition of geopolymer concrete.

4. Conclusions

Several types of scientific proposals for improving the properties of geopolymer concrete have been studied and tested. The optimal combination of aluminosilicate binders for the production of geopolymer concrete has been selected. The optimal content of polypropylene fiber for dispersed reinforcement of geopolymer concrete has been determined.
(1) It has been established that with an increase in the FA content, the cone slump decreases. The difference in the slump between the GGBS-based composition and the FA-based composition was 53.3%. FA particles are smaller and have a larger specific surface area compared to GGBS particles, and therefore, more water is required for their wetting, which leads to a decrease in the slump of the mixtures.
(2) The optimal composition of the geopolymer binder with a content of 80% GGBS and 20% FA has been determined. This combination of aluminosilicate components made it possible to obtain geopolymer concrete with a maximum compressive strength of 31.5 MPa. With this combination of GGBS and FA, the polymerization reactions proceed most actively with a large number of CSHs.
(3) Dispersed PF reinforcement improves the strength properties of geopolymer concrete. The PF content in the composite 0.8% is the most optimal. With a content of 0.8% PF, the maximum values of compressive and flexural strength were recorded, the increases which amounted to 7.3% and 48.7%, respectively. At the optimal dosage, polypropylene fibers are uniformly distributed throughout the structure of geopolymer concrete and create additional bonds, which subsequently lead to the strengthening of the entire structure of the composite.
(4) Electron and optical microscopy analysis of the geopolymer matrix based on a mixture of 80% GGBS and 20% FA showed a well-compacted microstructure and a large number of gel-like products of the geopolymerization reaction. No unreacted GGBS and FA particles were recorded. The PF at the fiber–matrix boundary is torn out of the matrix structure and deformed under the action of destructive loads. The nature of the destruction at the fiber–matrix boundary indicates a fairly good adhesion of the matrix and fiber.
(5) The resulting geopolymer fiber concrete on a combined binder has a compressive strength of 33.8 MPa and a flexural strength of 5.8 MPa, which determines its wide range of applications in real construction practice.
Further research is planned in the direction of studying the stress–strain behavior of geopolymer concrete using polymer fibers, as well as durability properties such as frost resistance, sulfate and chloride resistance and water resistance.

Author Contributions

Conceptualization, S.A.S., E.M.S., D.E. and A.C.; methodology, S.A.S., E.M.S. and D.E.; software, D.K.; validation, S.A.S., E.M.S., A.E. and A.C.; formal analysis, A.N.B., D.K. and S.O.; investigation, S.A.S., E.M.S., A.N.B., D.K., S.O., A.C. and D.E.; resources, S.A.S., E.M.S. and D.E.; data curation, A.E.; writing—original draft preparation, S.A.S., E.M.S. and A.N.B.; writing—review and editing, S.A.S., E.M.S. and A.N.B.; visualization, A.N.B.; supervision, A.N.B.; project administration, A.N.B.; funding acquisition, E.M.S. All authors have read and agreed to the published version of the manuscript.

Funding

The study was supported by the grant of the Russian Science Foundation No. 25-29-00535, https://rscf.ru/en/project/25-29-00535/ (accessed on 18 June 2025).

Institutional Review Board Statement

Not applicable.

Data Availability Statement

The original contributions presented in the study are included in the article; further inquiries can be directed at the corresponding author.

Acknowledgments

The authors would like to acknowledge the administration of Don State Technical University for their resources and financial support.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Gaidzhurov, P.P.; Volodin, V.A. Strength Calculation of the Coupling of the Floor Slab and the Monolithic Reinforced Concrete Frame Column by the Finite Element Method. Adv. Eng. Res. 2022, 22, 306–314. [Google Scholar] [CrossRef]
  2. Araújo, L.B.R.; Targino, D.L.L.; Babadopulos, L.F.A.L.; Fabbri, A.; Cabral, A.E.B.; Chehade, R.; Costa, H.N. Impact of Curing Temperature and Steel Slag Aggregates on High-Strength Self-Compacting Alkali-Activated Concrete. Buildings 2025, 15, 457. [Google Scholar] [CrossRef]
  3. Nikmehr, B.; Al-Ameri, R. A State-of-the-Art Review on the Incorporation of Recycled Concrete Aggregates in Geopolymer Concrete. Recycling 2022, 7, 51. [Google Scholar] [CrossRef]
  4. Ahmed, H.U.; Mohammed, A.A.; Rafiq, S.; Mohammed, A.S.; Mosavi, A.; Sor, N.H.; Qaidi, S.M.A. Compressive Strength of Sustainable Geopolymer Concrete Composites: A State-of-the-Art Review. Sustainability 2021, 13, 13502. [Google Scholar] [CrossRef]
  5. Shcherban’, E.M.; Stel’makh, S.A.; Beskopylny, A.; Mailyan, L.R.; Meskhi, B. Increasing the Corrosion Resistance and Durability of Geopolymer Concrete Structures of Agricultural Buildings Operating in Specific Conditions of Aggressive Environments of Livestock Buildings. Appl. Sci. 2022, 12, 1655. [Google Scholar] [CrossRef]
  6. Gulam, N.F.B.A.; Kaish, A.B.M.A.; Mahmood, A.; Raman, S.N.; Jamil, M.; Hamid, R. A Review on the Effect of Fly Ash, RHA and Slag on the Synthesizing of Coal Bottom Ash (CBA) Based Geopolymer. Eng. Proc. 2021, 11, 20. [Google Scholar] [CrossRef]
  7. Luhar, S.; Luhar, I.; Shaikh, F.U.A. Review on Performance Evaluation of Autonomous Healing of Geopolymer Composites. Infrastructures 2021, 6, 94. [Google Scholar] [CrossRef]
  8. Ionescu, B.A.; Lăzărescu, A.-V.; Hegyi, A. The Possibility of Using Slag for the Production of Geopolymer Materials and Its Influence on Mechanical Performances—A Review. Proceedings 2020, 63, 30. [Google Scholar] [CrossRef]
  9. Cheng, J.; Qin, Y.; Yao, Z.; Luo, L.; Qu, C. Study on the Chloride–Sulfate Resistance of a Metakaolin-Based Geopolymer Mortar. Materials 2024, 17, 5045. [Google Scholar] [CrossRef]
  10. Murtazaev, S.-A.Y.; Salamanova, M.S.; Saidumov, M.S.; Gatsaev, Z.S.; Alaskhanov, A.K.; Murtazaeva, T.S.-A. Development of geopolymer binders. Constr. Mater. Prod. 2024, 7, 4. [Google Scholar] [CrossRef]
  11. Adeleke, B.O.; Kinuthia, J.M.; Oti, J.; Ebailila, M. Physico-Mechanical Evaluation of Geopolymer Concrete Activated by Sodium Hydroxide and Silica Fume-Synthesised Sodium Silicate Solution. Materials 2023, 16, 2400. [Google Scholar] [CrossRef] [PubMed]
  12. He, W.; Li, B.; Meng, X.; Shen, Q. Compound Effects of Sodium Chloride and Gypsum on the Compressive Strength and Sulfate Resistance of Slag-Based Geopolymer Concrete. Buildings 2023, 13, 675. [Google Scholar] [CrossRef]
  13. Arunachelam, N.; Maheswaran, J.; Chellapandian, M.; Murali, G.; Vatin, N.I. Development of High-Strength Geopolymer Concrete Incorporating High-Volume Copper Slag and Micro Silica. Sustainability 2022, 14, 7601. [Google Scholar] [CrossRef]
  14. Hema, P.; Revathi, V. Durability Evaluation of GGBS-RHA-Based Geopolymer Concrete Along with Lightweight Expanded Clay Aggregate Using SEM Images and EDAX Analysis. Buildings 2024, 14, 3355. [Google Scholar] [CrossRef]
  15. Oti, J.; Adeleke, B.O.; Mudiyanselage, P.R.; Kinuthia, J. A Comprehensive Performance Evaluation of GGBS-Based Geopolymer Concrete Activated by a Rice Husk Ash-Synthesised Sodium Silicate Solution and Sodium Hydroxide. Recycling 2024, 9, 23. [Google Scholar] [CrossRef]
  16. Liu, S.; Liu, Z.; Takasu, K.; Koyamada, H.; Suyama, H. Study on the Effect of Recycled Fine Aggregate Qualities on Fly Ash/GGBS-Based Geopolymer Mortar. Materials 2023, 16, 7289. [Google Scholar] [CrossRef]
  17. Polydorou, T.; Spanou, M.; Savva, P.; Sakkas, K.; Oikonomopoulou, K.; Petrou, M.F.; Nicolaides, D. Development of a High Strength Geopolymer Incorporating Quarry Waste Diabase Mud (DM) and Ground Granulated Blast-Furnace Slag (GGBS). Materials 2022, 15, 5946. [Google Scholar] [CrossRef]
  18. Thakur, G.; Singh, Y.; Singh, R.; Prakash, C.; Saxena, K.K.; Pramanik, A.; Basak, A.; Subramaniam, S. Development of GGBS-Based Geopolymer Concrete Incorporated with Polypropylene Fibers as Sustainable Materials. Sustainability 2022, 14, 10639. [Google Scholar] [CrossRef]
  19. Hamed, Y.R.; Keshta, M.M.; Elshikh, M.M.Y.; Elshami, A.A.; Matthana, M.H.S.; Youssf, O. Performance of Sustainable Geopolymer Concrete Made of Different Alkaline Activators. Infrastructures 2025, 10, 41. [Google Scholar] [CrossRef]
  20. Xu, Q.; Shang, N.; Ko, J.H. Utilization of Municipal Solid Waste Incineration (MSWIFA) in Geopolymer Concrete: A Study on Compressive Strength and Leaching Characteristics. Materials 2024, 17, 4609. [Google Scholar] [CrossRef]
  21. Marczyk, J.; Ziejewska, C.; Gądek, S.; Korniejenko, K.; Łach, M.; Góra, M.; Kurek, I.; Doğan-Sağlamtimur, N.; Hebda, M.; Szechyńska-Hebda, M. Hybrid Materials Based on Fly Ash, Metakaolin, and Cement for 3D Printing. Materials 2021, 14, 6874. [Google Scholar] [CrossRef] [PubMed]
  22. Waqas, R.M.; Butt, F. Behavior of Quarry Rock Dust, Fly Ash and Slag Based Geopolymer Concrete Columns Reinforced with Steel Fibers under Eccentric Loading. Appl. Sci. 2021, 11, 6740. [Google Scholar] [CrossRef]
  23. Le, H.-B.; Bui, Q.-B.; Tang, L. Geopolymer Recycled Aggregate Concrete: From Experiments to Empirical Models. Materials 2021, 14, 1180. [Google Scholar] [CrossRef] [PubMed]
  24. Zailani, W.W.A.; Abdullah, M.M.A.B.; Arshad, M.F.; Razak, R.A.; Tahir, M.F.M.; Zainol, R.R.M.A.; Nabialek, M.; Sandu, A.V.; Wysłocki, J.J.; Błoch, K. Characterisation at the Bonding Zone between Fly Ash Based Geopolymer Repair Materials (GRM) and Ordinary Portland Cement Concrete (OPCC). Materials 2021, 14, 56. [Google Scholar] [CrossRef] [PubMed]
  25. Agustini, N.K.A.; Triwiyono, A.; Sulistyo, D.; Suyitno, S. Mechanical Properties and Thermal Conductivity of Fly Ash-Based Geopolymer Foams with Polypropylene Fibers. Appl. Sci. 2021, 11, 4886. [Google Scholar] [CrossRef]
  26. Nikoloutsopoulos, N.; Sotiropoulou, A.; Kakali, G.; Tsivilis, S. Physical and Mechanical Properties of Fly Ash Based Geopolymer Concrete Compared to Conventional Concrete. Buildings 2021, 11, 178. [Google Scholar] [CrossRef]
  27. Ahmad Zailani, W.W.; Bouaissi, A.; Abdullah, M.M.A.B.; Abd Razak, R.; Yoriya, S.; Mohd Salleh, M.A.A.; Rozainy M. A. Z., M.R.; Fansuri, H. Bonding Strength Characteristics of FA-Based Geopolymer Paste as a Repair Material When Applied on OPC Substrate. Appl. Sci. 2020, 10, 3321. [Google Scholar] [CrossRef]
  28. Hussain, K.; Butt, F.; Alwetaishi, M.; Waqas, R.M.; Aslam, F.; Ibraheem, M.; Zhu, X.; Ahmad, N.; Tufail, R.F.; Musarat, M.A.; et al. Effect of Quarry Rock Dust as a Binder on the Properties of Fly Ash and Slag-Based Geopolymer Concrete Exposed to Ambient and Elevated Temperatures. Appl. Sci. 2021, 11, 9192. [Google Scholar] [CrossRef]
  29. Jiang, C.; Wang, A.; Bao, X.; Chen, Z.; Ni, T.; Wang, Z. Protective Geopolymer Coatings Containing Multi-Componential Precursors: Preparation and Basic Properties Characterization. Materials 2020, 13, 3448. [Google Scholar] [CrossRef]
  30. Wei, X.; Ming, F.; Li, D.; Chen, L.; Liu, Y. Influence of Water Content on Mechanical Strength and Microstructure of Alkali-Activated Fly Ash/GGBFS Mortars Cured at Cold and Polar Regions. Materials 2020, 13, 138. [Google Scholar] [CrossRef]
  31. Bhina, M.R.; Liu, K.-Y.; Hu, J.-E.H.-Y.; Tsai, C.-T. Investigation of the Mechanical Properties of Quick-Strength Geopolymer Material Considering Preheated-to-Room Temperature Ratio of Sand, Na2SiO3-to-NaOH Ratio, and Fly Ash-to-GGBS Ratio. Polymers 2023, 15, 1084. [Google Scholar] [CrossRef]
  32. Ionescu, B.A.; Barbu, A.-M.; Lăzărescu, A.-V.; Rada, S.; Gabor, T.; Florean, C. The Influence of Substitution of Fly Ash with Marble Dust or Blast Furnace Slag on the Properties of the Alkali-Activated Geopolymer Paste. Coatings 2023, 13, 403. [Google Scholar] [CrossRef]
  33. Xiao, S.; Cai, Y.; Guo, Y.; Lin, J.; Liu, G.; Lan, X.; Song, Y. Experimental Study on Axial Compressive Performance of Polyvinyl Alcohol Fibers Reinforced Fly Ash—Slag Geopolymer Composites. Polymers 2022, 14, 142. [Google Scholar] [CrossRef] [PubMed]
  34. Meskhi, B.; Beskopylny, A.N.; Stel’makh, S.A.; Shcherban’, E.M.; Mailyan, L.R.; Shilov, A.A.; El’shaeva, D.; Shilova, K.; Karalar, M.; Aksoylu, C.; et al. Analytical Review of Geopolymer Concrete: Retrospective and Current Issues. Materials 2023, 16, 3792. [Google Scholar] [CrossRef]
  35. Zubarev, K.P.; Shcherban’, E.M.; Stel’makh, S.A.; Beskopylny, A.N.; Elshaeva, D.; Chernil’nik, A.; Zakieva, N.I.; Pimenova, E.V.; Shilov, A.A. Structure and Properties Improvement by Recipe Factors of Geopolymer Basalt Fiber Reinforced Concrete for Building Enclosing Structures. Buildings 2024, 14, 743. [Google Scholar] [CrossRef]
  36. Saprykina, T.K.; Zhadanov, V.I. Improving Theoretical Concepts of Composition Design of Dispersedly-Reinforced Concretes. Mod. Trends Constr. Urban Territ. Plan. 2024, 3, 66–73. [Google Scholar] [CrossRef]
  37. Su, J.; Mao, J.; Zhou, B.; Zhang, W.; Wang, L.; Mu, C. Dynamic compressive mechanical properties of fibre-reinforced geopolymer concrete. Case Stud. Constr. Mater. 2025, 22, e04268. [Google Scholar] [CrossRef]
  38. Nikmehr, B.; Kafle, B.; Al Zand, A.W.; Al-Ameri, R. The effect of hybrid basalt fibres on the mechanical and structural characteristics of geopolymer concrete containing geopolymer-coated recycled concrete aggregates. Constr. Build. Mater. 2024, 450, 138649. [Google Scholar] [CrossRef]
  39. Zhang, Y.H.; Zhong, W.L.; Fan, L.F. Long-term durability investigation of basalt fiber-reinforced geopolymer concrete in marine environment. J. Mater. Res. Technol. 2024, 31, 593–605. [Google Scholar] [CrossRef]
  40. Zhang, P.; Feng, Z.; Guo, J.; Zheng, Y.; Yuan, P. Mechanical behavior and microscopic damage mechanism of hybrid fiber-reinforced geopolymer concrete at elevated temperature. Ceram. Int. 2024, 50, 53851–53866. [Google Scholar] [CrossRef]
  41. Yan, J.; Wang, J.; Chen, H.; Xiang, P. High Temperature Exposure Assessment of Graphene Oxide Reinforced Cement. Front. Mater. 2022, 9, 786260. [Google Scholar] [CrossRef]
  42. Cao, B.; Li, Y.; Li, P. Synergistic Effect of Blended Precursors and Silica Fume on Strength and High Temperature Resistance of Geopolymer. Materials 2024, 17, 2975. [Google Scholar] [CrossRef]
  43. Mirgozar Langaroudi, M.A.; Mohtasham Moein, M.; Saradar, A.; Karakouzian, M. Investigation of the Mechanical Properties and Durability of Fiber-Reinforced Geopolymer Mortars Containing Metakaolin and Glass Powder. Infrastructures 2025, 10, 25. [Google Scholar] [CrossRef]
  44. Al-mashhadani, M.M.; Canpolat, O.; Aygörmez, Y.; Uysal, M.; Erdem, S. Mechanical and microstructural characterization of fiber reinforced fly ash based geopolymer composites. Constr. Build. Mater. 2018, 167, 505–513. [Google Scholar] [CrossRef]
  45. Masoud, L.; Hammoud, A.; Mortada, Y.; Masad, E. Rheological, mechanical, and microscopic properties of polypropylene fiber reinforced-geopolymer concrete for additive manufacturing. Constr. Build. Mater. 2024, 438, 137069. [Google Scholar] [CrossRef]
  46. Rani, S.Y.; Nusari, M.S.; bin Non, J.; Poddar, S.; Bhaumik, A. Durability of geopolymer concrete with addition of polypropylene fibre. Mater. Today Proc. 2022, 56, 2846–2851. [Google Scholar] [CrossRef]
  47. Shcherban’, E.M.; Stel’makh, S.A.; Beskopylny, A.N.; Meskhi, B.; Efremenko, I.; Shilov, A.A.; Vialikov, I.; Ananova, O.; Chernil’nik, A.; Elshaeva, D. Composition, Structure and Properties of Geopolymer Concrete Dispersedly Reinforced with Sisal Fiber. Buildings 2024, 14, 2810. [Google Scholar] [CrossRef]
  48. Raza, A.; Ahmed, B.; Hechmi El Ouni, M.; Chen, W. Mechanical, durability and microstructural characterization of cost-effective polyethylene fiber-reinforced geopolymer concrete. Constr. Build. Mater. 2024, 432, 136661. [Google Scholar] [CrossRef]
  49. Mansourghanaei, M.; Biklaryan, M.; Mardookhpour, A. Durability and Mechanical Properties of Granulated Blast Furnace Slag Based Geopolymer Concrete Containing Polyolefin Fibers and Nano Silica. KSCE J. Civ. Eng. 2024, 28, 209–219. [Google Scholar] [CrossRef]
  50. Wang, X.; Li, L.; Wei, M.; Xiang, Y.; Wu, Y.; Zhou, B.; Sun, Y.; Cheng, W. Experimental study on the mechanical properties of short-cut basalt fiber reinforced concrete under large eccentric compression. Sci. Rep. 2025, 15, 10845. [Google Scholar] [CrossRef]
  51. Morgun, V.N. About Dynamics of Improving the Foam Concrete Technological and Operational Properties upon Disperse Reinforcement with Polypropylene Fibers. Mod. Trends Constr. Urban Territ. Plan. 2023, 2, 69–76. [Google Scholar] [CrossRef]
  52. Vázquez-Rodríguez, F.; Elizondo, N.; Montes-González, M.; Gómez-Rodríguez, C.; González-Carranza, Y.; Guzmán, A.M.; Rodríguez, E.A. Microstructural and Mechanical Characteristics of Alkali-Activated Binders Composed of Milled Fly Ash and Granulated Blast Furnace Slag with µ-Limestone Addition. Materials 2023, 16, 3818. [Google Scholar] [CrossRef] [PubMed]
  53. Gudiel, E.; Payá, J.; Borrachero, M.V.; Monzó, J.M. Physico-Mechanical Properties of Alkali-Activated Based Composites Using Recycled Tire Fibers. Appl. Sci. 2025, 15, 1346. [Google Scholar] [CrossRef]
  54. Beskopylny, A.N.; Stel’makh, S.A.; Shcherban’, E.M.; Mailyan, L.R.; Meskhi, B.; El’shaeva, D.; Varavka, V. Developing Environmentally Sustainable and Cost-Effective Geopolymer Concrete with Improved Characteristics. Sustainability 2021, 13, 13607. [Google Scholar] [CrossRef]
  55. Lv, Y.; Chen, Y.; Dai, W.; Yang, H.; Jiang, L.; Li, K.; Jin, W. Preparation and Properties of Porous Concrete Based on Geopolymer of Red Mud and Yellow River Sediment. Materials 2024, 17, 923. [Google Scholar] [CrossRef]
  56. Chithiraputhiran, S.; Neithalath, N. Isothermal reaction kinetics and temperature dependence of alkali activation of slag, fly ash and their blends. Constr. Build. Mater. 2013, 45, 233–242. [Google Scholar] [CrossRef]
  57. Safari, Z.; Younis, K.H.; Kamal, I. Sustainable Utilization of Waste Pumice Powder in Slag-Based Geopolymer Concretes: Fresh and Mechanical Properties. Sustainability 2024, 16, 9296. [Google Scholar] [CrossRef]
  58. GOST R 57809-2017/EN 12350-2:2009; Testing Fresh Concrete—Part 2: Slump Test. Standartinform: Moscow, Russia, 2017. Available online: https://docs.cntd.ru/document/1200157288 (accessed on 13 March 2024).
  59. EN 12390-7:2019; Testing Hardened Concrete—Part 7: Density of Hardened Concrete. iTeh Standards: Etobicoke, ON, Canada, 2019. Available online: https://standards.iteh.ai/catalog/standards/cen/811a0cf3-55e3-495a-b06e-5c302d5f2806/en-12390-7-2019 (accessed on 13 March 2024).
  60. EN 12390-1:2021; Testing Hardened Concrete—Part 1: Shape, Dimensions and Other Requirements of Specimens and Moulds. iTeh Standards: Etobicoke, ON, Canada, 2021. Available online: https://standards.iteh.ai/catalog/standards/cen/d1c9ccee-2e5a-425e-a964-961da95d2f99/en-12390-1-2021 (accessed on 13 March 2024).
  61. EN 12390-2:2019; Testing Hardened Concrete—Part 2: Making and Curing Specimens for Strength Tests. iTeh Standards: Etobicoke, ON, Canada, 2019. Available online: https://standards.iteh.ai/catalog/standards/cen/ae7e6a86-1cbc-455e-8b2a-8964be9087f9/en-12390-2-2019 (accessed on 13 March 2024).
  62. EN 12390-3:2019; Testing Hardened Concrete—Part 3: Compressive Strength of Test Specimens. iTeh Standards: Etobicoke, ON, Canada, 2019. Available online: https://standards.iteh.ai/catalog/standards/cen/7eb738ef-44af-436c-ab8e-e6561571302c/en-12390-3-2019 (accessed on 13 March 2024).
  63. EN 12390-4:2019; Testing Hardened Concrete—Part 4: Compressive Strength—Specification for Testing Machines. iTeh Standards: Etobicoke, ON, Canada, 2019. Available online: https://standards.iteh.ai/catalog/standards/cen/10b1c613-819b-42d7-8f94-480cd37a666a/en-12390-4-2019 (accessed on 13 March 2024).
  64. EN 12390-5:2019; Testing Hardened Concrete—Part 5: Flexural Strength of Test Specimens. iTeh Standards: Etobicoke, ON, Canada, 2019. Available online: https://standards.iteh.ai/catalog/standards/cen/5653c2c7-55a9-4bcb-8e13-5b1dfb0e3baf/en-12390-5-2019 (accessed on 13 March 2024).
  65. GOST 10180-2012; Concretes. Methods for Strength Determination Using Reference Specimens. Standartinform: Moscow, Russia, 2018. Available online: https://docs.cntd.ru/document/1200100908 (accessed on 27 March 2025).
  66. Ansari, M.A.; Shariq, M.; Mahdi, F. Multi-optimization of FA-BFS based geopolymer concrete mixes: A synergistic approach using grey relational analysis and principal component analysis. Structures 2025, 71, 108007. [Google Scholar] [CrossRef]
  67. Beskopylny, A.N.; Stel’makh, S.A.; Shcherban’, E.M.; Saidumov, M.S.; Abumuslimov, A.; Mezhidov, D.; Wang, Z. Eco-Friendly Foam Concrete with Improved Physical and Mechanical Properties, Modified with Fly Ash and Reinforced with Coconut Fibers. Constr. Mater. Prod. 2025, 8, 1. [Google Scholar] [CrossRef]
  68. Puligilla, S.; Mondal, P. Role of slag in microstructural development and hardening of fly ash-slag geopolymer. Cem. Concr. Res. 2013, 43, 70–80. [Google Scholar] [CrossRef]
  69. Puertas, F.; Palacios, M.; Manzano, H.; Dolado, J.S.; Rico, A.; Rodríguez, J. A model for the C-A-S-H gel formed in alkali-activated slag cements. J. Eur. Ceram. Soc. 2011, 31, 2043–2056. [Google Scholar] [CrossRef]
  70. Zhu, J.F.; Wang, Z.Q.; Tao, Y.L.; Ju, L.Y.; Yang, H. Macro–micro investigation on stabilization sludge as subgrade filler by the ternary blending of steel slag and fly ash and calcium carbide residue. J. Clean. Prod. 2024, 447, 141496. [Google Scholar] [CrossRef]
  71. Batran, T.Z.; Ismail, M.K.; Serag, M.I.; Ragab, A.M. Cement-Free Geopolymer Paste: An Eco-Friendly Adhesive Agent for Concrete and Masonry Repairs. Buildings 2024, 14, 3426. [Google Scholar] [CrossRef]
  72. Amleh, L.; Hassan, M.; Hussein, L. Influence of Climate Change on the Probability of Chloride-Induced Corrosion Initiation for RC Bridge Decks Made of Geopolymer Concrete. Sustainability 2024, 16, 8200. [Google Scholar] [CrossRef]
  73. Sherwani, A.F.H.; Younis, K.H.; Arndt, R.W.; Pilakoutas, K. Performance of Self-Compacted Geopolymer Concrete Containing Fly Ash and Slag as Binders. Sustainability 2022, 14, 15063. [Google Scholar] [CrossRef]
  74. Zhang, G.-Y.; Lee, S.; Han, Y.; Wang, X.-Y. The Effect of Oyster Shell Powder on the High-Temperature-Properties of Slag-Ceramic Powder-Based Geopolymer. Materials 2023, 16, 3706. [Google Scholar] [CrossRef]
  75. Liu, X.; Liu, E.; Fu, Y. Reduction in Drying Shrinkage and Efflorescence of Recycled Brick and Concrete Fine Powder–Slag-Based Geopolymer. Appl. Sci. 2023, 13, 2997. [Google Scholar] [CrossRef]
  76. Xu, S.; Yuan, P.; Liu, J.; Pan, Z.; Liu, Z.; Su, Y.; Li, J.; Wu, C. Development and preliminary mix design of ultra-high-performance concrete based on geopolymer. Constr. Build. Mater. 2021, 308, 125110. [Google Scholar] [CrossRef]
  77. Sadrmomtazi, A.; Tahmouresi, B.; Saradar, A. Effects of silica fume on mechanical strength and microstructure of basalt fiber reinforced cementitious composites (BFRCC). Constr. Build. Mater. 2018, 162, 321–333. [Google Scholar] [CrossRef]
  78. Shcherban’, E.M.; Beskopylny, A.N.; Stel’makh, S.A.; Mailyan, L.R.; Meskhi, B.; Shilov, A.A.; Pimenova, E.; El’shaeva, D. Combined Effect of Ceramic Waste Powder Additives and PVA on the Structure and Properties of Geopolymer Concrete Used for Finishing Facades of Buildings. Materials 2023, 16, 3259. [Google Scholar] [CrossRef]
  79. Ertürkmen, D.; Ürünveren, H.; Beycioğlu, A.; Ibadov, N.; Aruntaş, H.Y.; Garbacz, A. Bond Performance of GFRP Bars in Glass and Basalt Fiber-Reinforced Geopolymer Concrete Under Hinged Beam Tests. Materials 2025, 18, 498. [Google Scholar] [CrossRef] [PubMed]
  80. Ahmed, T.I.; Rashed, A.S.; Tobbala, D.E. Sustainable Self-Healing Geopolymer Concrete Incorporating Recycled Plastic, Brick Waste, and Bacillus sphaericus. Ceramics 2025, 8, 72. [Google Scholar] [CrossRef]
  81. Hussain, S.; Matthews, J.; Amritphale, S.; Edwards, R.; Matthews, E.; Paul, N.; Kraft, J. Influence of Steel and Poly Vinyl Alcohol Fibers on the Development of High-Strength Geopolymer Concrete. Minerals 2024, 14, 1007. [Google Scholar] [CrossRef]
  82. Xu, L.; Liu, Q.; Ding, X.; Sun, S.; Huang, Z. Mechanical Properties of Fiber-Reinforced Permeable Geopolymer Concrete. Materials 2023, 16, 6030. [Google Scholar] [CrossRef]
  83. Zhang, M.; Qiu, X.; Shen, S.; Wang, L.; Zang, Y. Mechanical and Thermal Insulation Properties of rGFRP Fiber-Reinforced Lightweight Fly-Ash-Slag-Based Geopolymer Mortar. Sustainability 2023, 15, 7200. [Google Scholar] [CrossRef]
  84. Wei, Q.; Liu, Y.; Le, H. Mechanical and Thermal Properties of Phosphoric Acid Activated Geopolymer Materials Reinforced with Mullite Fibers. Materials 2022, 15, 4185. [Google Scholar] [CrossRef]
  85. Heweidak, M.; Kafle, B.; Al-Ameri, R. Influence of Hybrid Basalt Fibres’ Length on Fresh and Mechanical Properties of Self-Compacted Ambient-Cured Geopolymer Concrete. J. Compos. Sci. 2022, 6, 292. [Google Scholar] [CrossRef]
  86. Ziada, M.; Erdem, S.; Tammam, Y.; Kara, S.; Lezcano, R.A.G. The Effect of Basalt Fiber on Mechanical, Microstructural, and High-Temperature Properties of Fly Ash-Based and Basalt Powder Waste-Filled Sustainable Geopolymer Mortar. Sustainability 2021, 13, 12610. [Google Scholar] [CrossRef]
  87. Murthy, S.S.; Patil, N.N. Mechanical and durability characteristics of flyash and GGBFS based polypropylene fibre reinforced geopolymer concrete. Mater. Today Proc. 2022, 59, 18–24. [Google Scholar] [CrossRef]
  88. Gailitis, R.; Radina, L.; Pakrastins, L.; Sprince, A. Mechanical and Early Long-Term Property Assessment of Foamed 3D-Printable Geopolymer Composite. Materials 2025, 18, 2837. [Google Scholar] [CrossRef]
  89. Pham, K.V.A.; Nguyen, T.K.; Le, T.A.; Han, S.W.; Lee, G.; Lee, K. Assessment of Performance of Fiber Reinforced Geopolymer Composites by Experiment and Simulation Analysis. Appl. Sci. 2019, 9, 3424. [Google Scholar] [CrossRef]
  90. Puzatova, A.V.; Dmitrieva, M.A.; Tovpinets, A.O.; Leitsin, V.N. Study of Structural Defects Evolution in Fine-Grained Concrete Using Computed Tomography Methods. Adv. Eng. Res. 2024, 24, 227–237. [Google Scholar] [CrossRef]
  91. Antipas, I.R. Effect of Glass Fiber Reinforcement on the Mechanical Properties of Polyester Composites. Adv. Eng. Res. 2023, 23, 387–397. [Google Scholar] [CrossRef]
  92. Sha, F.; Dong, Y.; Gu, S.; Fan, X.; Xiao, W. Study on novel alkali-activated cementitious grout for scour control of offshore foundation. Geomech. Energy Envir. 2025, 42, 100663. [Google Scholar] [CrossRef]
  93. Beskopylny, A.N.; Shcherban’, E.M.; Stel’makh, S.A.; Mailyan, L.R.; Meskhi, B.; El’shaeva, D. The Influence of Composition and Recipe Dosage on the Strength Characteristics of New Geopolymer Concrete with the Use of Stone Flour. Appl. Sci. 2022, 12, 613. [Google Scholar] [CrossRef]
  94. Wei, M.; Chen, L.; Lei, N.; Li, H.; Huang, L. Mechanical properties and microstructures of thermally activated ultrafine recycled fine powder cementitious materials. Constr. Build. Mater. 2025, 475, 141195. [Google Scholar] [CrossRef]
  95. Razveeva, I.F.; Ivanchenko, S.A.; Bondarenko, I.V.; Kotenko, M.P.; Fedchishena, A.A. Development of Laboratory-made Compositions of Concrete Based on the Certain Raw Materials and Restrictions of the AKKUYU NPP Construction. Mod. Trends Constr. Urban Territ. Plan. 2022, 1, 24–33. [Google Scholar] [CrossRef]
Polymers 17 01710 g001
Figure 1. Appearance of aluminosilicate components: (a) FA, (b) GGBS.
Figure 1. Appearance of aluminosilicate components: (a) FA, (b) GGBS.
Polymers 17 01710 g001
Polymers 17 01710 g002aPolymers 17 01710 g002b
Figure 2. Particle distribution curves of (a) GGBS and FA; (b) GGBS and FA cumulative content; (c) QS; (d) CrS.
Figure 2. Particle distribution curves of (a) GGBS and FA; (b) GGBS and FA cumulative content; (c) QS; (d) CrS.
Polymers 17 01710 g002aPolymers 17 01710 g002b
Polymers 17 01710 g003
Figure 3. Experimental study program of geopolymer concrete on a combined binder.
Figure 3. Experimental study program of geopolymer concrete on a combined binder.
Polymers 17 01710 g003
Polymers 17 01710 g004
Figure 4. Experimental study program for geopolymer fiber-reinforced concrete with combined binder.
Figure 4. Experimental study program for geopolymer fiber-reinforced concrete with combined binder.
Polymers 17 01710 g004
Polymers 17 01710 g005
Figure 5. Density of fresh geopolymer concrete as a function of GGBS and FA content.
Figure 5. Density of fresh geopolymer concrete as a function of GGBS and FA content.
Polymers 17 01710 g005
Polymers 17 01710 g006
Figure 6. Dependence of fresh geopolymer concrete slump on GGBS and FA content.
Figure 6. Dependence of fresh geopolymer concrete slump on GGBS and FA content.
Polymers 17 01710 g006
Polymers 17 01710 g007
Figure 7. Dependence of the density of geopolymer concrete on the content of GGBS and FA.
Figure 7. Dependence of the density of geopolymer concrete on the content of GGBS and FA.
Polymers 17 01710 g007
Polymers 17 01710 g008
Figure 8. Compressive strength of geopolymer concrete as a function of GGBS and FA content.
Figure 8. Compressive strength of geopolymer concrete as a function of GGBS and FA content.
Polymers 17 01710 g008
Polymers 17 01710 g009
Figure 9. A sample of geopolymer concrete of the 80G/20F type (a) before failure; (b) after failure.
Figure 9. A sample of geopolymer concrete of the 80G/20F type (a) before failure; (b) after failure.
Polymers 17 01710 g009
Polymers 17 01710 g010
Figure 10. Compressive strength of geopolymer concrete as a function of PF content.
Figure 10. Compressive strength of geopolymer concrete as a function of PF content.
Polymers 17 01710 g010
Polymers 17 01710 g011
Figure 11. Geopolymer concrete flexural strength versus PF content.
Figure 11. Geopolymer concrete flexural strength versus PF content.
Polymers 17 01710 g011
Polymers 17 01710 g012
Figure 12. Microstructure of geopolymer paste of composition 80G/20F: (a) with magnification of 300×; (b) with magnification of 1000×.
Figure 12. Microstructure of geopolymer paste of composition 80G/20F: (a) with magnification of 300×; (b) with magnification of 1000×.
Polymers 17 01710 g012
Polymers 17 01710 g013
Figure 13. Microstructure of geopolymer paste of composition 80G/20F with 0.8% PF: (a) with magnification of 300×; (b) with magnification of 1000×.
Figure 13. Microstructure of geopolymer paste of composition 80G/20F with 0.8% PF: (a) with magnification of 300×; (b) with magnification of 1000×.
Polymers 17 01710 g013
Polymers 17 01710 g014
Figure 14. Structure of a sample of geopolymer concrete of type 80G/20F: (a) without marking; (b) with marking.
Figure 14. Structure of a sample of geopolymer concrete of type 80G/20F: (a) without marking; (b) with marking.
Polymers 17 01710 g014
Polymers 17 01710 g015
Figure 15. Structure of the sample of geopolymer concrete of the 80G/20F type with 0.8% PF: (a) without marking; (b) with marking.
Figure 15. Structure of the sample of geopolymer concrete of the 80G/20F type with 0.8% PF: (a) without marking; (b) with marking.
Polymers 17 01710 g015
Table 1. Chemical composition of GGBS and FA.
Table 1. Chemical composition of GGBS and FA.
OxidGGBSFA
SiO2 (%)31.150.82
Al2O3 (%)7.0920.5
Fe2O3 (%)0.517.71
CaO (%)38.55.55
MgO (%)4.322.18
TiO2 (%)0.280.87
Р2О5 (%)0.030.21
SO3 (%)2.190.16
LOI (%)15.9812.0
Bulk density (kg/m3)10981013
Table 2. Compositions of geopolymer concrete on a combined binder.
Table 2. Compositions of geopolymer concrete on a combined binder.
Mixture TypeGGBS/FA (%)GGBS (kg/m3)FA
(kg/m3)		QS
(kg/m3)		CrS
(kg/m3)		NaOH (kg/m)3Water
(L/m3)
100G/0F100/04880485127231190
80G/20F80/20390.497.6485127231190
60G/40F60/40292.8195.2485127231190
40G/60F40/60195.2292.8485127231190
20G/80F20/8097.6390.4485127231190
0G/100F0/1000488485127231190
Table 3. Compositions of geopolymer fiber concrete on a combined binder.
Table 3. Compositions of geopolymer fiber concrete on a combined binder.
Mixture TypeGGBS
(kg/m3)		FA
(kg/m3)		QS
(kg/m3)		CrS
(kg/m3)		PF
(kg/m)3		NaOH
(kg/m)3		Water
(L/m3)
PF/0.2390.497.648512720.9831190
PF/0.4390.497.648512721.9531190
PF/0.6390.497.648512722.9331190
PF/0.8390.497.648512723.9031190
PF/1.0390.497.648512724.8831190
PF/1.2390.497.648512725.8631190
Table 4. Processing of the results obtained during the tests.
Table 4. Processing of the results obtained during the tests.
Name of the IndicatorCalculation Formula
Cone slumpDifference between the height of the mold and the height of the highest point of the settled geopolymer mixture. Average value based on the results of two tests.
Mixture density ρ f c = m − m 1 V × 1000               (1)
here m is the mass of the measuring vessel with concrete mixture (g);
m1 is the mass of the measuring vessel without mixture (g);
V is the capacity of the measuring vessel (cm3).
Concrete density ρ = m V × 1000                    (2)
here m is the mass of the sample (g);
V is the volume (cm3)
Compressive strength R = α F A                      (3)
here F is the breaking load (N);
A is the area of the working cross-section of the sample (mm2);
α is the coefficient considering the dimensions of the samples (for samples with a side of 100 mm α = 0.95).
Bending strength R b t = δ F   l a   b 2                     (4)
here F is the breaking load (N);
a, b, l are the width, height of the prism cross-section and the distance between the supports, respectively, when testing samples for tensile strength under bending (mm);
δ is the coefficient considering the dimensions of the samples (for samples with a side of 100 mm δ = 0.92).
Table 5. Analysis of the effect of combined geopolymer binders on the properties of the geopolymer composite.
Table 5. Analysis of the effect of combined geopolymer binders on the properties of the geopolymer composite.
Ref NumberType of Aluminosilicate ComponentProportion The Obtained Result
[71] Slag/microsilica/metakaolin70%/20%/10%Repair geopolymer composition with good adhesive properties
[72] Fly ash/slag 50%/50%Geopolymer concrete with high resistance to chloride corrosion
[73]70%/30%
[52]Slag/fly ash/limestone60%/40%/+5%Geopolymer composite with compressive strength of 42 MPa
[53]Diabase sludge/slag30%/70%Geopolymer composite with reduced shrinkage and compressive strength of 98.05 MPa
[74]Slag/oyster shell powder90%/10%Efficient and environmentally friendly composites with the required performance properties and improved durability properties
[75]Slag/concrete and brick waste powder45%/55%
Table 6. Analysis of the effect of dispersed reinforcement with polypropylene fiber on the properties of geopolymer concrete.
Table 6. Analysis of the effect of dispersed reinforcement with polypropylene fiber on the properties of geopolymer concrete.
Ref NumberFIBER TYPEOptimum ContentObtained Result
[79]Glass/Basalt1%/1%Hinged geopolymer beams with the addition of glass and basalt fiber showed strength of 49% and 37% higher than that of the control geopolymer concrete
[80]Polypropylene0.2–0.4%Geopolymer solutions with improved strength and reduced permeability were obtained
[81]Steel3%Inclusion of steel fiber in geopolymer concrete after 28 days allowed to obtain a composite with a compressive strength of 107 MPa
[82]0.3%Increase in compressive strength of permeable geopolymer composite up to 43.62%
[83]Recycled fiberglass2–6%Compressive strength of foamed geopolymer composite increased by 25–165%, and shrinkage decreased by 55%
[84]Mullite fiber10%Increase in compressive strength up to 20%
[85]Basalt1–2%Geopolymer composites with improved strength and performance properties were obtained
[86]
[87,88,89]Polypropylene0.25–2%
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Stel’makh, S.A.; Beskopylny, A.N.; Shcherban, E.M.; Elshaeva, D.; Chernilnik, A.; Kuimov, D.; Evtushenko, A.; Oganesyan, S. Geopolymer Concrete Physical and Mechanical Properties on a Combined Binder Reinforced with Dispersed Polypropylene Fiber. Polymers 2025, 17, 1710. https://doi.org/10.3390/polym17121710

AMA Style

Stel’makh SA, Beskopylny AN, Shcherban EM, Elshaeva D, Chernilnik A, Kuimov D, Evtushenko A, Oganesyan S. Geopolymer Concrete Physical and Mechanical Properties on a Combined Binder Reinforced with Dispersed Polypropylene Fiber. Polymers. 2025; 17(12):1710. https://doi.org/10.3390/polym17121710

Chicago/Turabian Style

Stel’makh, Sergei A., Alexey N. Beskopylny, Evgenii M. Shcherban, Diana Elshaeva, Andrei Chernilnik, Denis Kuimov, Alexandr Evtushenko, and Samson Oganesyan. 2025. "Geopolymer Concrete Physical and Mechanical Properties on a Combined Binder Reinforced with Dispersed Polypropylene Fiber" Polymers 17, no. 12: 1710. https://doi.org/10.3390/polym17121710

APA Style

Stel’makh, S. A., Beskopylny, A. N., Shcherban, E. M., Elshaeva, D., Chernilnik, A., Kuimov, D., Evtushenko, A., & Oganesyan, S. (2025). Geopolymer Concrete Physical and Mechanical Properties on a Combined Binder Reinforced with Dispersed Polypropylene Fiber. Polymers, 17(12), 1710. https://doi.org/10.3390/polym17121710

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop