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Article

Characterization of Steel Industry Byproducts as Precursors in Alkali-Activated Binders

by
Madson Lucas de Souza
1,*,
Abcael Ronald Santos Melo
1,
Laura Prévitali
2,
Lucas Feitosa de Albuquerque Lima Babadopulos
1,
Juceline Batista dos Santos Bastos
3 and
Iuri Sidney Bessa
1
1
Campus do Pici, Universidade Federal do Ceará, Fortaleza 60455-760, Brazil
2
Campus Marne-la-Vallée, Université Gustave Eiffel, 77420 Champs-sur-Marne, France
3
Campus Fortaleza, Instituto Federal de Educação, Ciência e Tecnologia do Ceará, Fortaleza 60040-531, Brazil
*
Author to whom correspondence should be addressed.
Buildings 2025, 15(17), 3119; https://doi.org/10.3390/buildings15173119
Submission received: 30 June 2025 / Revised: 28 August 2025 / Accepted: 28 August 2025 / Published: 1 September 2025
(This article belongs to the Section Building Materials, and Repair & Renovation)
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Versions Notes

Abstract

The civil construction and infrastructure sectors are known for their high environmental impact. Most of this impact is related to the carbon dioxide (CO2) emissions from Portland cement. As a sustainable alternative, alkali-activated binders (AABs) are explored for their potential to replace traditional binders. This research focused on AAB formulations using steel industry byproducts, such as Baosteel’s slag short flow (BSSF), coke oven ash (CA), blast furnace sludge (BFS), and centrifuge sludge (CS), as well as fly ash (FA) from a thermoelectric plant. Byproducts were characterized through laser granulometry, Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscopy (SEM), followed by the formulation of AABs with different precursor ratios. After 28 days, the compressive strength was obtained for each formulation. Based on the compressive strength tests, two binary mixtures were selected for microstructural and chemical analyses through XRF, FTIR, and SEM. CA demonstrated the greatest potential for use in binary AABs based on BSSF, as it presented a higher source of aluminosilicates and smaller particle sizes. The formulations containing BSSF and CA achieved compressive strengths of up to 9.8 MPa, while the formulations with BSSF and FA reached 23.5 MPa. SEM images revealed a denser, more cohesive matrix in the FA-based AAB, whereas CA-based AABs showed incomplete precursor dissolution and higher porosity, which contributed to the lower mechanical strength of CA-based AABs. These findings highlight the critical role of precursor selection in developing sustainable AABs from industrial byproducts and demonstrate how different formulations can be tailored for specific applications.

1. Introduction

The civil construction and infrastructure sectors are known for their high environmental impact, both in terms of their waste generation and their energy and natural resource consumption [1]. The production of Portland cement, a widely used binder, is responsible for significant CO2 emissions, which are estimated at one ton of CO2 per ton of Portland-based concrete produced [2]. To meet the growing demand for sustainability, alternative binders have been explored to reduce the environmental footprint of these sectors. Among these, alkali-activated binders (AABs), also known as geopolymers, have emerged as promising substitutes for Portland cement [3]. AABs are produced by activating an aluminosilicate precursor with a highly concentrated alkaline solution, which creates a binder that can vary from amorphous to semicrystalline [4].
These materials exhibit potential advantages such as high early-age strength, enhanced chemical durability, and the capacity to incorporate diverse industrial byproducts, which positions them as sustainable alternatives in materials technology [3,5]. Significant research has focused on the development and application of AABs [3] due to their environmental and performance benefits compared to conventional Portland cement. Commonly investigated precursors include fly ash, blast furnace slag, and metakaolin [5]. Nevertheless, certain alternatives remain underexplored, such as steel industry byproducts, which present opportunities for novel applications in alkali-activated systems [6].
Global crude steel production exceeds 1.89 billion tons annually, generating approximately 600 kg of waste per ton of steel produced, much of which consists of steel slags [7]. In Brazil, steel production reached 34.1 million tons in 2023, with significant contributions from the state of Ceará, which houses ArcelorMittal Pecém (AMP) [8]. During steel production, various byproducts are generated, including coke oven ash (CA), blast furnace sludge (BFS), centrifuge sludge (CS), and different slags [8].
Steel production by AMP takes place through the basic oxygen furnace (BOF) process, which is responsible for 75% of the total steel production in Brazil [8,9]. This process generates a range of byproducts, including steelmaking slags. A specific technological cooling method, known as the Baosteel slag short flow (BSSF) process, is employed to treat BOF slag at AMP. In this process, liquid slag is poured into a rotating drum and cooled by water jets, which produces a granulated material. The subsequent magnetic separation yields the BSSF byproduct (BSSF slag) [8]. AMP generates, on average, over 219 thousand tons of BSSF annually, with around 63% being commercialized [8]. Typical slag generation rates range from 100 to 150 kg per ton of liquid steel [8]. Although this BSSF process has higher operational costs compared to conventional air cooling, it allows for faster product dispatching, as the co-product from the BOF process alone requires around 12 months of ambient curing to limit its expansive characteristics (undesirable in construction and infrastructure projects) before it can be employed in construction. This rapid cooling not only minimizes storage yard requirements but also produces a clean, safe, and higher-quality byproduct that is suitable for faster market dispatch [8].
Despite this potential, research on the application of BSSF in AABs remains largely unexplored, with most studies focusing on its use as an aggregate in conventional concretes [10,11,12]. Regarding BOF slags—closely related but still distinct from BSSF slag—recent studies have highlighted promising avenues for their application. Pereira et al. (2020) [13] demonstrated that BOF slag-based AABs, when formulated with optimized solid/liquid ratios, can produce dimensionally stable elements with potential engineering applications. Nunes et al. [6] reported that alkaline activation dissolves significant crystalline phases in BOF slag, leading to the formation of cementitious hydrates despite its low inherent reactivity. Caetano et al. [14] evaluated the fresh and hardened properties of alkali-activated pastes containing varying proportions of bottom ash/BOF slag and fly ash/BOF slag, finding that higher BOF contents accelerated setting under ambient curing. Araújo [15] developed mix design guidelines for AABs using FA and BOF slag, incorporating parameters for the silica modulus, alkali content, precursor ratios, and curing conditions. Furthermore, AAB technology has shown strong potential in civil engineering applications, including in interlocking pavers [16,17] and as a performance-enhancing additive in asphalt binders [18,19].
Given the growing need for sustainable construction materials, this study aims to evaluate the potential of AABs formulated with steel industry byproducts. Specifically, the research focuses on using BSSF, CA, BFS, and CS from steel industry and fly ash (FA) from thermoelectric plants as precursors for AABs, based on their particle size, chemical composition, and microstructural characteristics. Two precursor configurations were assessed for the AAB formulations: (i) a configuration exclusively based on steel industry byproducts and (ii) a combination of BSSF and FA with varying ratios. FA was included due to its well- established ability to enhance mechanical properties [5]. Two formulations, selected based on their compressive strength, underwent microstructural and chemical analysis.
This study addresses a largely unexplored area by evaluating the use of potential steel industry byproducts as AAB precursors. Despite representing significant industrial waste streams, their potential in alkali activation has been scarcely explored compared to that of conventional precursors such as FA, blast furnace slag, or even BOF slags. By characterizing these byproducts in detail and evaluating their performance in binary systems (with and without FA), this research demonstrates that underutilized industrial residues can be transformed into sustainable binders. In doing so, it contributes to waste valorization, CO2 reduction, and the expansion of the material portfolio available to the alkali-activated materials community, with particular relevance to the development of sustainable binders for pavement and other civil construction applications. It is also noteworthy that this work is part of a broader research project aimed at developing self-compacting alkali-activated concretes for civil construction and paving applications, with the goal of producing pavers without vibration presses.

2. Materials and Methods

This section describes the materials used and the experimental methods employed in this study to develop and evaluate alkali-activated binders (AABs) formulated with steel industry byproducts. The aim is to provide sufficient details to ensure that the processes are replicable. First, the constituent materials, including the steel industry byproducts and activators, are introduced. Then, the methodological procedures for analyzing the materials, formulating the AABs, and testing their mechanical properties are presented.

2.1. Constituent Materials

The byproducts from the steel production process—BSSF, CA, BFS, and CS—were collected from AMP. The generation pathways of these materials, following the specific production processes employed at AMP, are illustrated in Figure 1 [8]. CA is produced during the combustion of coal and iron ore in either the sintering plant or the coke oven, depending on the operational route. This fine particulate solid is recovered during gas dedusting and can be reintroduced into steel production as an auxiliary energy source. BFS is generated during the washing of the gas from the blast furnace, when solid particulates are separated from water, which produces a slurry commonly referred to as “blast furnace sludge.” CS results from the cleaning and washing of production systems and equipment across steelmaking operations and is obtained through an industrial decantation process that functions similarly to a “wastewater sludge” stream for the plant. BSSF slag is produced just after the liquid slag from the steelmaking process undergoes treatment in a rotating drum, where it is cooled with water jets, granulated, and magnetically separated to yield a cleaner, higher-quality product, as described in larger detail in the Introduction section [8].
Following the analysis described in Section 2.3.1, only BSSF and CA were selected as precursors for AAB production. To achieve better mechanical properties, FA was also incorporated into AAB formulations along with BSSF. The specific gravity of BSSF, CA, and FA is 3740, 2080, and 2210, respectively.
As activators, a sodium hydroxide solution with a molar concentration of 10 mol/L and a commercial alkaline sodium silicate solution were used. Although the sodium silicate solutions used for mixes M1–M5 and M6–M10 were obtained from different commercial batches, their key properties were consistent, since their key parameters remained very similar. For example, the silica modulus (SiO2/Na2O) averaged 2.2 for M1–M5 and 2.3 for M6–M10, while the total solid content was approximately 47.8% and 47.9%, respectively. These slight variations were within acceptable tolerances for the supplier’s specification and did not significantly affect the activation conditions. The sodium hydroxide provided the necessary alkalinity to initiate the activation reaction, while the sodium silicate functioned as a supplementary source of soluble silica [20].

2.2. Methods

This research included four main methodological stages (Figure 2): (i) analysis of industrial byproducts with potential for use as precursors in AAB; (ii) formulation of AABs (a) exclusively from steel industry byproducts and (b) from BSSF and FA, both with varied precursor ratios; (iii) evaluation of compressive strength at 28 days, and (iv) microstructural analysis of the binary AABs with higher compressive strength.

2.3. Industrial Byproducts Analysis

The properties of AABs are intrinsically linked to the type and characteristics of the precursor used, including factors such as particle size, chemical composition, aluminosilicate content, and calcium content [3,5,21,22]. Therefore, all materials were subjected to particle size analysis and chemical composition assessments to characterize them, to evaluate their potential for alkali activation, and to understand how they can contribute to the development of binders with adequate mechanical properties for civil construction and paving applications. BSSF was one of the precursors previously selected for analysis. Laser granulometry, Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscopy (SEM) tests were conducted. Prior to these analyses, the materials were sieved to a particle size below 150 μm and subsequently dried in an oven at 100 °C for 24 h [15,23,24].
Unlike the other byproducts, the BSSF underwent a grinding process prior to sieving to enhance its reactivity and optimize its use. This step is essential not only for material characterization but also for AAB production, as a lower surface area can favor crystallization and hinder the interaction between particles, thereby limiting the formation of alkali-activated gels [25,26]. The BSSF was milled in a planetary ball mill (motor: ¼ HP) operating at a fixed rotational speed of approximately 170 rpm on the drive roll. The milling jar had a total capacity of 15 L, and each batch contained 6 kg of material along with 60 porcelain balls, each with an average mass of 105.5 ± 2 g and a diameter of 38.2 ± 0.6 mm. Each batch was milled for 6 h, ensuring effective grinding and homogenization prior to the production of AABs.

2.3.1. Steel Industry Byproducts

After analyzing the 4 steel industry byproducts (BSSF, CA, BFS, and CS), the byproduct with the highest potential for application in the production of binary AAB based on BSSF was selected from CA, BFS, and CS. Laser granulometry (Figure 3) revealed that the byproducts BSSF, CA, BFS, and CS had particle diameters of 186.0 μm, 112.4 μm, 149.5 μm, and 195.1 μm, respectively, each of which corresponded to the 90% passing percentage (D90). The D90 value for BSSF and CS exceeds the 150 μm sieve mesh, likely due to a slight desynchronization or calibration issue with the used sieve. However, since this analysis is solely for powder characterization, it does not affect the interpretation of the results. Additionally, the specific surface areas were measured as follows: 0.329 m2/g for BSSF, 0.252 m2/g for CA, 0.506 m2/g for BFS, and 0.116 m2/g for CS. Among these, CA exhibited the smallest particle diameter, while BFS demonstrated the largest specific surface area along with the second smallest particle diameter. Therefore, the byproducts CA and BFS showed a more favorable tendency for greater reactivity with alkaline activators, especially if they were in the presence of amorphous material [27]. To observe the morphology of the materials, SEM images were taken, and these are presented in Figure 4. All the steel industry byproducts presented an irregular shape with high angularity.
The oxide composition, determined by X-ray fluorescence (XRF), is presented in Table 1. All materials exhibited a significant presence of iron oxide (Fe2O3), varying between 20% and 40%, due to the use of iron ore as a raw material in the steel production process (Figure 1). The composition of alumina (Al2O3) and silica (SiO2) was the primary focus of evaluation, as AABs are obtained through the alkaline activation of an aluminosilicate precursor [4,28,29]. It was observed that CS (39.8%) and CA (21.4%) had higher contents of Al2O3 and SiO2, which makes these byproducts the most promising for application in AABs. Nevertheless, CA inherently contains a significant fraction of carbonaceous material (soot), which is not detected by XRF. As a result, the oxide composition in Table 1 underestimates the true carbon content of CA. In contrast, the elevated CaO content (also confirmed by the FTIR analysis) in BSSF is noteworthy, as it plays an important role as one of the main influencers in the products formed during the alkaline activation of an aluminosilicate source [28].
Figure 5 shows the diffraction patterns obtained through X-ray diffraction (XRD), which were conducted mainly to identify the crystalline phases. While crystalline compounds are associated with specific diffraction angles (2θ), amorphous materials produce broad diffuse humps [30,31]. The diffractograms reveal distinct mineralogical assemblages for each byproduct, which are directly linked to their generation pathways during different stages of BOF and BSSF steelmaking operations within the AMP industry.
The BSSF sample is characterized by sharp and intense peaks associated with wuestite (Fe0.95O—ICDD 96-101-1169), brownmillerite (Ca2Fe1.63Al0.37O5—ICDD 96-901-5863), and larnite (Ca2SiO4—ICDD 96-901-2795), which is consistent with previous findings [32,33]. This crystalline assemblage is likely a consequence of the BSSF processing being carried out in a rotating drum, where slag is simultaneously cooled with water jets, which promotes rapid crystallization. These phases corroborate the high calcium and iron contents previously detected by XRF. Wuestite is a typical byproduct of steelmaking generated during high temperature rolling processes [34]. Moreover, mechanical properties—such as the elastic modulus, hardness, and elastic recovery—decrease progressively from hematite (Fe2O3) to wuestite [35]. The brownmillerite and larnite both contribute to slag stability, although larnite is known to exhibit expansive reactivity in aqueous environments. Brownmillerite is volumetrically stable, typically being formed during oxygen blowing in BOF slags, where FeO oxidizes to Fe2O3 and reacts with calcium and aluminum [36]. Beyond its role in slag stability, brownmillerite has been identified as a promising candidate for low-carbon cement production [37]. Thus, the presence of brownmillerite in BSSF underscores its potential for innovative, high-value reuse within cementitious systems.
Additionally, the BSSF process involves simultaneous quenching and grinding, which strongly influences phase transformations [33]. Crystal formation is a function of both the chemical composition of the melt and its cooling rate. While silica-rich blast furnace slags tend to vitrify under rapid cooling [33], BSSF—with its comparatively lower silica content (see Table 1)—rarely undergoes vitrification, even when subjected to intense quenching. Consequently, crystallization remains the dominant outcome. Overall, the predominance of calcium-bearing phases highlights the role of BSSF as a calcium-rich precursor that can promote the formation of C–A–S–H type gels and accelerating gel development during alkali activation [28].
The CA diffractogram exhibits a partially amorphous background, which is evident from a broad hump between 20 and 35° in the 2θ range that is superimposed with crystalline reflections from quartz (SiO2—ICDD 96-900-9667), bassanite (CaSO4·0.5H2O—ICDD 96-900-5522), graphite (C4—ICDD 96-120-0018), and sillimanite (Al2SiO5—ICDD 96-900-3989). The occurrence of bassanite and graphite aligns with the byproduct’s origin in sintering and coking operations: bassanite results from the partial dehydration of gypsum—an intermediate phase between gypsum (CaSO4·2H2O) and anhydrite (CaSO4)—whereas graphite forms through incomplete combustion of coke or coal during steelmaking. Importantly, the broad amorphous halo [30,31] may be largely influenced by the presence of amorphous elemental carbon (soot) [38,39], which is invisible to XRF and appears as an amorphous background in XRD, rather than being attributable solely to aluminosilicate phases. Although the amorphous contribution from carbon complicates interpretation, CA still contains aluminosilicate phases such as quartz and sillimanite, which may contribute to alkali activation [28,29]. Additionally, the fine particle size of CA can promote filler effects and enhance reaction kinetics within alkali-activated systems [3,28].
For BFS, the main crystalline phases identified include quartz (SiO2—ICDD 96-500-0036), wulfingite (ZnO2H2—ICDD 96-901-5546), and halloysite (Al2Si2O11—ICDD 96-101-1247). Quartz and halloysite may provide reactive aluminosilicate species that contribute to alkali activation [4,28,29]. The occurrence of Zn-bearing phases such as wulfingite is linked to BOF processing, and these are typically considered contaminants that limit slag reuse in steelmaking [40,41]. Moreover, wulfingite is highly stable and exhibits low solubility in both acidic and alkaline solutions [42], which may hinder its reactivity during alkali activation and affect its performance as a precursor.
Finally, the CS sample shows crystalline peaks associated with calcium phosphate silicate (Ca2SiO4·0.05Ca3(PO4)2—ICDD 00-049-1674), brownmillerite (Ca2Fe2O5—ICDD 96-901-4765), and calcium aluminum oxide (Ca12Al14O33—ICDD 01-078-0910). This composition reflects its derivation from wastewater sludge streams that are rich in calcium, iron, and aluminum-bearing compounds.
Complementing the XRF and XRD analysis, Figure 6 shows the FTIR of the steel industry byproducts. The peak between 1640 cm−1 and 1650 cm−1 observed in CA, BFS, and CS is attributed to the bending vibration of H-OH groups from chemically bound water. Additionally, broad humps around 3420 cm−1 and 3440 cm−1 correspond to the stretching vibrations of -OH groups. These bands in the raw materials are characteristic of the presence of humidity in the samples, even after oven-drying. More pronounced peaks can be seen in the BFS and CS samples, which is expected due to the wet nature of these materials. The characteristic bands observed in BSSF at approximately 1464 cm−1 are associated with the asymmetric stretching vibrations of C-O (CO32−) [43,44]. These bands indicate a higher presence of calcite, which is potentially formed through the reaction between excess calcium oxide (CaO) and atmospheric CO2 [45,46]. Specifically, for BSSF, distinct shoulders at 938 cm−1 and 866 cm−1 are evident. These features may correspond to the symmetric stretching vibrations of Si–O–Si bonds [44] or could be linked to Fe–O bonds [47]. Bands between 900 cm−1 and 1300 cm−1 are present in all the analyzed powders. These bands are usually attributed to the asymmetric stretching modes of Si–O–T bonds, where T represents Si or Al in tetrahedral sites [48]. Additionally, for all materials, excepted for CA, bands around 550 cm−1 correspond to the bending modes of Si–O, Al–O, or even Fe–Si–O bonds [49,50].
Considering all the physical and chemical analyses of the steel industry byproducts, CA demonstrated the greatest potential for use in binary AABs with BSSF, owing to its favorable aluminosilicate content and finer particle size distribution [27,28].

2.3.2. Thermoelectric Byproduct—Fly Ash (FA)

In addition to the AABs produced exclusively with steel industry byproduct precursors, this study also explored the incorporation of FA in AABs, a precursor widely utilized in previous research [5,51]. For this purpose, binary precursor systems were employed: FA and BSSF, sourced from a thermoelectric power plant and the steel industry, respectively. Table 2 presents the oxide compositions of the FA obtained through XRF analysis. High levels of Al2O3 (15.6%) and SiO2 (46.8%) were identified, along with moderate CaO levels of 8.1%. According to ASTM C618 [52], these oxide levels classify the material as Class F FA, which is characterized by a predominantly silico-aluminous composition and lower calcium content. This composition is advantageous for promoting the formation of stable aluminosilicate gels such as N–A–S–H. Notably, a considerable number of aluminosilicates were detected, surpassing the values found in the steel industry byproducts that were analyzed. The substantial presence of SiO2 and Al2O3 is critical for the alkaline activation mechanism, as these oxides provide the essential framework for the dissolution–polycondensation process that leads to the formation of geopolymeric gel networks [4]. This compositional advantage positions FA as a valuable component in the development of sustainable binders, contributing to enhanced mechanical and microstructural performance in AABs, particularly when used in combination with industrial byproducts like BSSF.
The laser granulometry results are presented in Figure 7a. FA exhibited a finer granulometry than BSSF, with a D90 of 126.2 μm and a higher specific surface area (0.414 m2/g). These characteristics suggest a greater potential reactivity of FA, as finer particles and larger surface areas are known to enhance dissolution kinetics in alkali-activated systems. Figure 7b presents an SEM image of FA, revealing predominantly spherical particles, commonly referred to as cenospheres. This morphology plays a significant role in enhancing the performance of alkali-activated systems. The spherical shape acts like a microscopic ball bearing, improving the flowability of the mixture and promoting better particle dispersion. Additionally, these particles contribute to better packing efficiency, as they can fill void spaces more effectively than angular particles (like the steel byproducts), thereby increasing the packing density of the system. This results in improved surface contact between FA and the alkaline activator, which is crucial for initiating the dissolution of the amorphous glassy phase—responsible for releasing reactive Si and Al species that drive gel formation. These combined effects may enhance the reactivity of FA AABs [29,53].
Figure 7c presents the FTIR spectra of FA, showing prominent vibrational bands around 980 cm−1. These bands are attributed to the asymmetric stretching vibrations of Si–O–T bonds, where T represents either Si or Al atoms occupying tetrahedral sites in the amorphous aluminosilicate structure [48]. The intensity and breadth of these bands in FA indicate a high content of potential reactive phases, which are critical for alkali activation. Additionally, bands near 550 cm−1 correspond to the bending vibrations of Si–O and Al–O bonds, further supporting the presence of aluminosilicate materials [50].
Complementary to these results, Figure 7d displays the XRD patterns of FA, showing a predominance of quartz (SiO2—ICDD 96-101-1098), gypsum (CaSO4·2H2O—ICDD 96-901-3165), magnetite (Fe3O4—ICDD 96-900-5839), and hercynite (FeAl2O4—ICDD 96-900-1971), which are like phases found in some previous studies [54,55,56]. However, a relatively common mineral, mullite (3Al2O3∙2SiO2), was not identified. Additionally, greater quantity of aluminosilicate phases was observed compared with the BSSF sample, as evidenced by the broad halo in the 2θ range of 20–40°. Overall, the predominance of aluminum- and silicon-bearing phases underscores the role of FA as an aluminosilicate-rich precursor that is capable of promoting the formation of N–A–S–H-type gels during alkali activation [4,28,29].
By combining precursors with low and high calcium content, such as FA and BSSF, respectively, it is possible to obtain binders with intermediate calcium levels. This combination can enable the creation of a binder that benefits from the advantages of both systems, such as the high chemical resistance of N–A–S–H gels and the low porosity of C–A–S–H gels [3]. When mixed effectively, these materials can result in AABs with mechanical properties and curing times suitable for practical field applications [57,58].

2.4. Formulation of AABs

Based on the analyses of the industrial byproducts (Section 2.3), two distinct precursor matrices were chosen for the formulation of AABs: (i) BSSF and CA; and (ii) BSSF and FA. The parameters for the dosages were established as follows: (i) the alkali content (Na2O/(BSSF+CA or BSSF+FA)), referred to as N/B, was set at 10% by mass, aligning with other studies that reported N/B ratios between 4% and 15% [15,20,59]; and (ii) the silica modulus (SiO2/Na2O) of the activators was set at 0.75, based on research that utilized silica moduli ranging from 0.5 to 2 [15,20,60]. Once these parameters were fixed, each matrix was divided into five formulations with varying masses of the precursor quantities. The values were adjusted based on studies that replaced fly ash with steel slag by up to 50% [15,61,62]. The 10 different dosages, referred to as mixes, are detailed in Table 3.
For mixes M3, M4, and M5, the alkali content was increased from 10% to 14% due to the inability to mix and mold these binders with the original content. This adjustment was necessary because there was insufficient liquid solution to react with all the precursor particles. In the case of M5, despite the alkali content increasing to 14%, mixing and molding were still not feasible. Additionally, the activators used in M1–M5 and M6–M10 came from different batches. However, the dosing was performed to ensure that the parameters for the alkali content and silica modulus remained constant.
The mixing procedure for all AABs was determined and executed in a planetary mixer as follows: (i) 1 min of pre-homogenization of the precursors; (ii) 1.5 min of mixing with the activators at 62 ± 5 RPM (low speed); (iii) 1 min pause to check for homogeneity; (iv) 1.5 min of mixing at 125 ± 5 RPM; (v) 30 s pause to check for homogeneity; (vi) 1 min of mixing at 125 ± 5 RPM (the duration of this step may be extended depending on the homogeneity of the mixture). After the mixing procedure, the fresh AABs were immediately cast into cubic molds with internal dimensions of 4 cm × 4 cm × 4 cm. The molds were filled in a single layer without vibration, as the mixtures exhibited self-compacting behavior. Once cast, the specimens were kept at ambient laboratory conditions (approximately 25 °C and 65–85% relative humidity) for initial setting and hardening. Demolding was performed carefully after 24 h to avoid damaging the specimens. Subsequently, the specimens were stored under the same ambient conditions for a total of 28 days prior to mechanical testing, and for at least 180 days before microstructural analysis. No additional thermal curing or moisture sealing was employed, to simulate practical conditions for potential field applications.

2.5. Compressive Strength

To evaluate the compressive strength, 3 specimens from each AAB were tested after 28 days of ambient curing. The tests were conducted in accordance with ASTM [63], using a universal testing machine with a capacity of 300 kN (EMIC GR048). The loading was applied at a rate of (500 ± 0.5) N/s, and failure was detected when the specimens could no longer support an increase in load [64].

2.6. Microstructural and Chemical Analysis

Microstructural and chemical analyses were performed on AAB samples after 180 days of curing, enabling the evaluation of properties at an advanced stage of binding gel and phase development [65]. The samples were extracted from specimens previously subjected to compressive strength testing. For analysis, the material was either crushed into powders for XRF and FTIR testing or prepared as small fragments for SEM examination.

2.6.1. XRF

XRF analysis was conducted to determine the oxide composition of the powdered AAB samples, using a Rigaku ZSX Mini II sequential wavelength dispersive X-ray spectrometer (WDX). The instrument operated at 40 kV and 1.2 mA with a palladium (Pd) tube, providing semi-quantitative analysis of elements with atomic numbers ranging from fluorine to uranium.

2.6.2. FTIR

FTIR analysis was carried out using a Shimadzu IR-Prestige spectrometer over the wavenumber range of 4000–400 cm−1. Powdered AAB samples were mixed with potassium bromide (KBr) and pressed into pellets for measurement. This technique was employed to identify functional groups and chemical bonds—such as C–O and Si–O–T (where T = Si or Al), as well as H–OH groups—providing insights into the structural composition of the binding phases.

2.6.3. SEM

SEM analysis was performed using an Inspect S50—FEI microscope to investigate the morphological features of the AAB fragments. The focus was on identifying unreacted and reacted precursors, microcracks, voids, the morphology of the gel matrix, and the gel structures.

3. Results

3.1. Compressive Strength

3.1.1. AAB Based on CA and BSSF

The compressive strength results for the AABs produced with different proportions of BSSF and CA are presented in Figure 8. The workability during mixing and casting was evaluated qualitatively through visual inspection of the mixture’s flow, its cohesiveness, and the ease of filling the molds, with the aim of future application in civil construction or paving. This approach allowed for immediate identification of formulations with inadequate fresh-state performance. For the AABs containing higher proportions of CA (M3, M4, and M5), the initial alkali content (N/B) of 10% was insufficient to produce a workable paste. The N/B was therefore increased to 14% to facilitate mixing and molding [66]. This adjustment was necessary due to the amount of available liquid solution being insufficient to adequately react with all the precursor particles. For M5 (100% CA), even with the N/B increased to 14%, proper mixing remained unachievable.
In all AABs, the silica modulus of the activator solution was fixed at 0.75. This relatively low value was selected to minimize adverse effects on workability while maintaining consistent alkali silicate chemistry and thereby ensured that any observed variations in fresh and hardened properties were primarily associated with changes in the precursor composition rather than the activator formulation. The silica modulus plays a decisive role in AAB rheology: higher silicate contents in the activator generally increase the solution viscosity and promote the formation of early silicate oligomers, which can enhance structural build-up in the paste but also limit particle mobility [3,5,6,67].
CA—despite its finer particle size compared to BSSF—exhibited poor compatibility with the alkaline solution due to its carbonaceous composition (as discussed in Section 2.3.1). The presence of soot, which is intrinsically non-wetting [68,69], hindered the dispersion of particles and impaired the mixing process. Although finer particles usually increase the liquid demand, in CA-rich systems this effect was aggravated by the non-wetting nature of soot, which limited the precursor–activator interaction. Consequently, with the fixed silica modulus condition, and even under increased N/B, CA-rich mixtures such as M5 required more free liquid yet still showed reduced flowability, ultimately compromising the homogeneity and preventing effective alkali activation.
Given the variations in N/B required to achieve workable AABs, comparisons regarding variations in compressive strength were conducted separately for the AABs with 10% (M1 and M2) and 14% (M3 and M4) N/B. In the 10% N/B group, there is a noticeable trend of increasing CA content, which consequently leads to higher levels of SiO2 and Al2O3 (Table 1) and results in elevated compressive strength values (7.2 MPa for M1 and 9.8 MPa for M2) [4,70]. This trend suggests that, under adequate workability conditions, the additional reactive silica and alumina from CA contributed positively to gel formation and matrix densification. Conversely, in the 14% N/B group, an inverse trend was observed, where the increase in CA led to a reduction in the compressive strength (3.7 MPa for M3 and 2.0 MPa for M4). This phenomenon is associated with the greater alkali content required to improve workability. This can be explained by the increased alkali content, which results in higher liquid content in the binder matrix, ultimately leading to lower mechanical strength [71].
Regarding the observed reduction in compressive strength from M4 to M3, it is hypothesized that the higher CA content in M4 resulted in the 14% alkali content being insufficient to promote adequate mixing and create a favorable environment for the reactions between precursors and activators, which consequently affected the formation of the gels responsible for the mechanical strength of the AAB. These results highlight the delicate interplay between precursor particle characteristics, the activator composition (specifically the silica modulus), and the liquid/solid ratio in determining both the fresh-state and hardened-state performance of AABs.

3.1.2. AAB Based on FA and BSSF

The compressive strength results of the AABs based on BSSF and FA are presented in Figure 9. An increase in strength is observed when substituting BSSF for FA, with M10, the AAB composed of 100% FA, showing the highest average compressive strength (29.0 MPa). This is attributed to the higher presence of aluminosilicates found in FA (Table 2 and Figure 7), as aluminosilicates favor alkali-activation reactions and enhance the production of gels that contribute to mechanical strength [4,70]. Another noteworthy point is that, despite a growing trend in strength between AABs M6 and M10, the AAB M7, containing 75% BSSF and 25% FA, exhibited the highest compressive strength. This result contradicts previous research [6,14,15], which indicated that higher proportions of the BOF steelmaking byproduct (not treated as BSSF) relative to FA lead to lower compressive strength values. This finding prompted further investigation and microstructural analyses to understand the reactions and factors contributing to the observed increase in strength.
When comparing Figure 8 and Figure 9, a noticeable increase in the compressive strength of AABs based on FA is observed in comparison to those based on CA. This phenomenon is primarily attributed to the higher presence of aluminosilicates in FA [4,70], as evidenced in Table 2 and Figure 7. Notably, M2 and M7 emerged as the binary AABs with the highest compressive strength, which indicates that a ratio of 25% CA or FA with 75% BSSF is optimal among the produced AABs.
It is also important to underline the visual evidence of efflorescence in M6–M10, with severity being observed in M6 (Figure 10). In this AAB, the efflorescence progressively intensified during curing, extending beyond superficial deposition and ultimately leading to specimen degradation. This phenomenon can be attributed to the elevated CaO content associated with the increased BSSF mass, which was required to maintain a constant alkali content and silica modulus after the change in activator batches in formulations M6–M10. The higher and excessive calcium availability likely facilitated the migration of soluble salts to the surface and thereby explains both the degradation and the lower compressive strength of M6 compared with M1 (lower mass of BSSF, despite both being composed of 100% BSSF) [72]. Efflorescence was also detected in other BSSF-rich formulations (M7–M10); however, no specimen degradation was observed. As for the CA-based AABs (M1–M5), only minor signs of efflorescence were observed, yet without any evidence of specimen degradation

3.2. Microstructural and Chemical Analysis

For the microstructural and chemical analyses, two formulations—M2 (CA–BSSF = 25–75) and M7 (FA–BSSF = 25–75)—were selected based on their superior compressive strength (as indicated in Figure 8 and Figure 9), a key property for civil construction applications and an important proxy for a material’s quality. Both formulations exhibited a workable, liquid-like consistency suitable for mixing and molding, which supports their practical applicability in self-compacting alkali-activated concretes for civil construction and paving applications [15]. The selection of these optimal combinations allows for a detailed investigation of how the precursor composition may influence the formation of reaction products in BSSF-based AABs, and how it may be related to their mechanical properties.

3.2.1. XRF

Table 4 presents the oxide compositions of the AABs M2 and M7, as determined by XRF analysis. A significant increase in both Al2O3 and SiO2 is observed in M7, with the SiO2 content rising from 9.3% in M2 to 23.9% in M7. Al2O3 is fundamental for the formation of aluminosilicate binding gels such as N–A–S–H and C–A–S–H, while SiO2 enhances gel development and contributes to structural cohesion [3]. These compositional differences correlate with the mechanical performance results, which demonstrate higher compressive strength for M7 compared to M2 and thereby confirm the positive influence of increased Al2O3 and SiO2 contents on the reactivity of raw materials and the strength of AABs.
Both binders show high CaO contents, particularly in M2, which is consistent with the chemical nature of CA and BSSF (Table 1), due to their lower Al2O3 and SiO2 and higher CaO contents compared to FA (Table 2). In calcium-rich systems, the formation of C–A–S–H, C–(N) –A–S–H, or C–S–H type gels is predominant, contributing to early strength development and structural integrity [48,73]. Additionally, both formulations exhibit elevated Fe2O3 contents, with M2 presenting the highest content (49.1%). While Fe2O3 may contribute to reaction products [74] or act as an inert filler, potentially influencing microstructure densification [75], its specific role in the structural formation of the AAB structure and its effect on strength development remains underexplored and merits further investigation.
It should be noted, however, that XRF provides bulk oxide composition and does not distinguish between reacted and unreacted phases or identify specific gel types. Therefore, the XRF results are complemented by FTIR and SEM analyses, which offer more detailed information on reaction products and microstructural development.

3.2.2. FTIR

Figure 11 displays the FTIR spectra of M2 and M7. A broad absorption band observed between 3000 cm−1 and 3700 cm−1 corresponds to the stretching vibrations of hydroxyl (-OH) groups, indicating the presence of weakly bonded water within the reaction products. This spectral feature is commonly associated with hydration phases such as C–S–H gels [48,65]. Notably, the FA-based binder (M7) exhibits a more intense band in this region compared to the CA-based binder (M2), which suggests a greater formation of hydration products [76], which is consistent with the higher compressive strength values obtained—23.5 MPa for M7 versus 9.8 MPa for M2.
The peaks at 1485 cm−1 and 1405 cm−1 are attributed to the asymmetric stretching vibrations of carbonate ions (CO32−), likely resulting from the atmospheric carbonation of residual sodium compounds [43,44]. The elevated intensity of these peaks, particularly in BSSF-rich compositions, reflects a higher calcite content formed through the reaction between excess CaO—abundant in calcium-rich BSSF—and atmospheric CO2 [45,46]. This may also be influenced by the presence of unreacted BSSF or CA [65].
Bands between 900 and 1300 cm−1 are associated with asymmetric stretching vibrations of Si–O–T bonds (where T = Si or Al in tetrahedral coordination), which is characteristic of aluminosilicate networks [48]. This region is particularly informative regarding the structure and polymerization of amorphous gel phases such as N–A–S–H, C–A–S–H, and, potentially, C–S–H gels [77,78]. M7 again demonstrates higher peak intensity in this region, which further supports the evidence of an enhanced reaction and mechanical performance.
A distinct peak at 866 cm−1 may correspond to residual unreacted BSSF (see Figure 6), aligning with characteristic peaks at 938 and 870 cm−1. Alternatively, this peak could be attributed to the symmetric stretching of Si–O–Si bonds [44] or Fe–O bonds [36], corroborating the chemical profiles identified in the XRF analysis. Lastly, the band near 670 cm−1 is assigned to the symmetric stretching vibrations of Si–O–Si(Al) linkages, which is indicative of aluminosilicate framework formation [79,80]. This feature is, again, more pronounced in M7, which aligns with the improved gel formation and higher compressive strength observed in FA-based AABs.

3.2.3. SEM

Figure 12 displays the scanning electron microscopy (SEM) images of the AABs M2 and M7 at two different magnifications, highlighting the influence of the precursor composition on microstructural development. The overall features are consistent with alkali-activated ash–slag binders, typically comprising a continuous binding gel phase with embedded unreacted ash and slag particles [65,81,82]. At a magnification of 1000×, broader features such as the presence of gels, voids, and microcracks—partly attributable to residual stresses from the compressive strength tests—are evident. At a magnification of 5000×, finer details are visible, including the formation of gel structures, unreacted FA, CA, and BSSF particles, as well as reacted FA, voids, micropores (probably formed by the reacted FA), and microcracks. The morphology of FA, with its predominantly spherical shape (Figure 7b), contrasts with the irregular forms of CA and BSSF (Figure 4), allowing clear distinction between these particles. These microstructural characteristics were identified in line with previous reports on alkali-activated systems [65,81,82,83,84,85,86,87].
In M2, the matrix displays unreacted angular particles of CA and BSSF embedded within discontinuous geopolymerization gels, along with voids and microcracks. These features are indicative of incomplete dissolution of the precursors and limited gel formation, which are often associated with limited reactivity and lower amorphous content in steel industry byproducts [84]. This may happen due to the limited amounts of reactive silica and alumina in such materials (Table 1), which hinder the formation of continuous geopolymer gels, resulting in a less homogeneous matrix and potentially reduced mechanical performance, as shown in Figure 8.
In contrast, M7 reveals a denser and more homogeneous matrix that is characterized by fewer distinct unreacted particles and a more uniform gel distribution [83]. The lower porosity and reduced presence of unreacted precursors suggest that the microstructure is dominated by gels of different chemistry than those in CA-based systems [65,88]. This behavior is associated with the different mineralogy and morphology of FA particles, and, more specifically, with variations in solubility and the nature of the reaction product gels generated by the two precursors [65]. Spherical FA particles are sometimes observed intact, but are mostly reacted or partially dissolved, which indicates active involvement in the alkali activation process [85,86]. The spherical morphology of FA enhances particle packing and flowability, improves contact with the alkaline solution, and promotes dissolution of aluminosilicate species, which in turn facilitates extensive gel network development [29,57,58].
The SEM evidence clearly corroborates the superior reactivity and performance of FA-based AABs compared to those relying solely on steel industry byproducts. While FA–BSSF AABs are more promising for structural and paving applications due to their enhanced densification and strength, CA–BSSF AABs may still be more appropriate for non-structural uses, such as in soil stabilization, asphalt binder modification, drywall panels, or low-strength construction elements.

4. Conclusions

This study aimed to evaluate the potential of alkali-activated binders (AABs) formulated with steel industry byproducts, with the objective of contributing to the development of sustainable construction materials. Specifically, the research investigated the use of Baosteel’s slag short flow (BSSF), coke ash (CA), blast furnace sludge (BFS), and centrifuge sludge (CS) from steel industry and, complementarily, the use of fly ash (FA) from thermoelectric plants as a precursor, assessing their particle size, chemical composition, and microstructural characteristics. Two precursor configurations were explored: (i) AABs based exclusively on steel industry byproducts and (ii) binary systems combining BSSF and FA in varying ratios. Based on compressive strength tests, two binary AABs with a composition of 75% BSSF and 25% CA (M2) or FA(M7) were selected for microstructural and chemical analyses. The main conclusions drawn from this work are summarized as follows:
  • Among the four steel industry byproducts, CA demonstrated the highest potential for alkali activation due to its finer particle sizes (D90 of 112.4 μm), specific surface area (0.252 m2/g), and favorable aluminosilicate content. BSSF was confirmed as a calcium-rich precursor, exhibiting phases such as brownmillerite and larnite, which support gel formation and accelerate early strength development;
  • FA presented a higher content of aluminosilicates and predominantly spherical particles, which enhanced the resulting flowability, packing density, and dissolution kinetics. Its incorporation into BSSF-based AABs contributed to the formation of dense, well-connected gel networks, improving both the mechanical properties and matrix homogeneity of the resulting AABs;
  • The increase in BSSF content in the FA-based AABs led to greater efflorescence salt formation, likely due to the excess of CaO;
  • Achieving a higher CA content in AABs required higher alkali dosages, which reduced the workability of the AABs and led to a reduction in compressive strength;
  • AABs produced solely from steel industry byproducts (BSSF and CA) achieved compressive strengths up to 9.8 MPa. In contrast, the incorporation of FA markedly improved their performance, allowing the compressive strength to reach 23.5 MPa. Both AAB systems exhibited optimal performance at a 75–25 ratio of BSSF to ash (either CA or FA), achieving the best balance between precursor reactivity and mechanical strength;
  • XRF analysis confirmed that the FA-based AAB (M7) contained higher amounts of SiO2 (23.9% vs. 9.3% for M2) and Al2O3 (3.9% vs. 1.0% for M2), achieving more effective gel formation and, consequently, improved mechanical strength. In contrast, the aCA-based AAB (M2) presented higher CaO (32.9% vs. 28.0% for M7) and Fe2O3 (49.1% vs. 35.2% for M7) contents. SEM and FTIR analyses revealed that M7 developed a denser, more homogeneous matrix with fewer unreacted particles, whereas M2 showed incomplete precursor dissolution, a discontinuous matrix, and higher porosity, which is consistent with its lower compressive strength;
  • The combination of BSSF with FA offers a pathway to valorize industrial byproducts while producing eco-efficient binders with mechanical properties that are suitable for structural and paving applications. CA–BSSF systems, although less reactive, may still be applicable for non-structural uses, such as low-strength construction elements (e.g., drywall panels), soil stabilization, and asphalt binder modification.
Overall, this study demonstrates that steel industry byproducts, particularly BSSF, can serve as effective precursors for alkali-activated systems. Their performance can be considerably enhanced by incorporating aluminosilicate-rich FA, which highlights- the potential of mixed industrial residues to produce sustainable, high-value construction materials. Utilizing these byproducts not only reduces industrial waste but also promotes material innovation. These findings underscore the critical role of precursor selection in the development of sustainable AABs from industrial byproducts.

Author Contributions

Conceptualization, M.L.d.S., L.F.d.A.L.B. and J.B.d.S.B.; methodology, M.L.d.S., L.P. and L.F.d.A.L.B.; tests investigation, M.L.d.S. and L.P.; data curation, M.L.d.S. and A.R.S.M.; writing—original draft preparation, M.L.d.S., A.R.S.M. and J.B.d.S.B.; writing—review and editing, L.F.d.A.L.B. and I.S.B.; supervision, L.F.d.A.L.B., J.B.d.S.B. and I.S.B.; project administration, L.F.d.A.L.B. All authors have read and agreed to the published version of the manuscript.

Funding

This work was part of a research project supported by ArcelorMittal-Pecém through the project “Research and Development in Materials with Steel Aggregate for Pavement Layers” and by the National Council for Scientific and Technological Development (CNPq), project numbers: 407235/2022-1; 408682/2021-3; 405958/2023-4.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding authors.

Acknowledgments

The authors express their gratitude to ArcelorMittal-Pecém (AMP), the Pavement Mechanics Laboratory (LMP) at the Federal University of Ceará (UFC), the Civil Construction Materials Laboratories (LMCC) at UFC, and the Coordination for the Improvement of Higher Education Personnel (CAPES).

Conflicts of Interest

The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

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Buildings 15 03119 g001
Figure 1. Processes that generate steel industry byproducts (red flows indicate byproducts, blue flows represent the steelmaking process, and the green flow corresponds to the BSSF treatment).
Figure 1. Processes that generate steel industry byproducts (red flows indicate byproducts, blue flows represent the steelmaking process, and the green flow corresponds to the BSSF treatment).
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Figure 2. Methodological steps.
Figure 2. Methodological steps.
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Figure 3. Laser granulometry of steel industry byproducts.
Figure 3. Laser granulometry of steel industry byproducts.
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Figure 4. SEM images of steel industry byproducts.
Figure 4. SEM images of steel industry byproducts.
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Figure 5. XRD patterns of steel industry byproducts.
Figure 5. XRD patterns of steel industry byproducts.
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Figure 6. FTIR spectra of (a) BSSF; (b) CA; (c) BFS; and (d) CS.
Figure 6. FTIR spectra of (a) BSSF; (b) CA; (c) BFS; and (d) CS.
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Figure 7. (a) Laser granulometry, (b) SEM image, (c) FTIR spectra, and (d) XRD patterns of FA.
Figure 7. (a) Laser granulometry, (b) SEM image, (c) FTIR spectra, and (d) XRD patterns of FA.
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Figure 8. Compressive strength of AAB based on CA and BSSF.
Figure 8. Compressive strength of AAB based on CA and BSSF.
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Figure 9. Compressive strength of AABs based on FA and BSSF.
Figure 9. Compressive strength of AABs based on FA and BSSF.
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Figure 10. Visual analysis of efflorescence formation in M6–M10 AABs.
Figure 10. Visual analysis of efflorescence formation in M6–M10 AABs.
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Figure 11. FTIR spectra of M2 and M7.
Figure 11. FTIR spectra of M2 and M7.
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Figure 12. SEM images of M2 and M7.
Figure 12. SEM images of M2 and M7.
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Table 1. XRF oxide composition of steel industry byproducts (% mass).
Table 1. XRF oxide composition of steel industry byproducts (% mass).
MaterialAl2O3SiO2P2O5SO3ClK2OCaOTiO2ZnOMnOFe2O3
BSSF1.36.92.2---45.10.4-3.239.9
CA6.015.4-24.84.52.920.42.6--22.0
BFS3.16.30.512.20.7-3.7-35.40.234.5
CS37.32.511.711.11.80.77.8--0.420.7
Table 2. XRF oxide composition of FA (% mass).
Table 2. XRF oxide composition of FA (% mass).
MaterialAl2O3SiO2P2O5SO3ClK2OCaOTiO2MnOFe2O3
FA 15.646.80.41.90.03.78.11.80.121.0
Table 3. Formulation of AAB (consumption in kg/m3).
Table 3. Formulation of AAB (consumption in kg/m3).
IDCA–BSSF
(%)		FA–BSSF
(%)		NaOH SolutionNa2SiO3 Solution CAFA BSSF
M10-100-396.4350.10.0-1485.7
M225-75-392.6346.8367.9-1103.7
M350-50-482.2378.2573.2-573.2
M475-25-404.3357.1811.8-270.6
M5100-0 382.9338.21023.3-0.0
M6-0-100441.5366.0-0.01610.4
M7-25-75410.8340.6-374.71123.9
M8-50-50384.2318.5-700.7700.7
M9-75-25360.8299.1-986.9329.0
M10-100-0340.0281.9-1240.3-
Table 4. XRF oxide composition of M2 and M7 (% mass).
Table 4. XRF oxide composition of M2 and M7 (% mass).
MaterialAl2O3SiO2P2O5SO3K2OCaOTiO2MnOFe2O3Other
M2 (25–75)
%CA–BSSF		1.09.32.31.20.232.90.82.849.10.4
M7 (25–75)
%FA–BSSF		3.923.93.20.81.628.01.51.835.20.1
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Souza, M.L.d.; Melo, A.R.S.; Prévitali, L.; Babadopulos, L.F.d.A.L.; Bastos, J.B.d.S.; Bessa, I.S. Characterization of Steel Industry Byproducts as Precursors in Alkali-Activated Binders. Buildings 2025, 15, 3119. https://doi.org/10.3390/buildings15173119

AMA Style

Souza MLd, Melo ARS, Prévitali L, Babadopulos LFdAL, Bastos JBdS, Bessa IS. Characterization of Steel Industry Byproducts as Precursors in Alkali-Activated Binders. Buildings. 2025; 15(17):3119. https://doi.org/10.3390/buildings15173119

Chicago/Turabian Style

Souza, Madson Lucas de, Abcael Ronald Santos Melo, Laura Prévitali, Lucas Feitosa de Albuquerque Lima Babadopulos, Juceline Batista dos Santos Bastos, and Iuri Sidney Bessa. 2025. "Characterization of Steel Industry Byproducts as Precursors in Alkali-Activated Binders" Buildings 15, no. 17: 3119. https://doi.org/10.3390/buildings15173119

APA Style

Souza, M. L. d., Melo, A. R. S., Prévitali, L., Babadopulos, L. F. d. A. L., Bastos, J. B. d. S., & Bessa, I. S. (2025). Characterization of Steel Industry Byproducts as Precursors in Alkali-Activated Binders. Buildings, 15(17), 3119. https://doi.org/10.3390/buildings15173119

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