Next Article in Journal
Assessing the Effects of Exposure to Green Rooftop Spaces on Perceived Restorativeness: A Field Study in Xiamen, China
Previous Article in Journal
Performance Evaluation of Highly Modified Asphalt-Based Binders in High Friction Surface Treatment: Comparative Study with Epoxy-Based System
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Buildings
Volume 15
Issue 9
10.3390/buildings15091426
buildings-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

Synthesis and Property Characterization of Low-Activity Waste-Derived Quaternary Cementitious Materials

by
Linlin Jiang
1,
Xianhui Zhao
2,* and
Haoyu Wang
1
1
School of Civil Engineering, Tianjin Renai College, Tianjin 301636, China
2
School of Civil Engineering, Hebei University of Engineering, Handan 056038, China
*
Author to whom correspondence should be addressed.
Buildings 2025, 15(9), 1426; https://doi.org/10.3390/buildings15091426
Submission received: 28 March 2025 / Revised: 21 April 2025 / Accepted: 22 April 2025 / Published: 23 April 2025
(This article belongs to the Section Building Materials, and Repair & Renovation)
Browse Figures
Versions Notes

Abstract

:
The environmental risks associated with industrial solid wastes—fly ash (FA), red mud (RM), carbide slag (CS), and steel slag (SS)—are amplified by their massive global accumulation. This study developed a quaternary cementitious system using low-activity industrial wastes—FA, RM, CS, and SS—as alternatives to high-reactivity ground granulated blast furnace slag. The hydration behavior, mechanical properties, and microstructure were investigated, along with the effects of Ca(ClO)2 and Ca3(PO4)2 as calcium additives. Fresh properties (fluidity, pH, and electrical conductivity), compressive strength, and drying shrinkage were evaluated, while SEM-EDS, XRD, FTIR, and TG-DSC analyzed microstructural evolution. The results show that FA-RM alone failed to solidify, but CS enhanced hydration, reducing fluidity and increasing strength, while SS improved thermal stability as a micro-aggregate. The optimized FA-RM-CS-SS system achieved 16.7 MPa at 90 days. Ca(ClO)2 accelerated C-S-H gel formation, whereas Ca3(PO4)2 stabilized the matrix via hydroxyapatite precipitation, mitigating shrinkage. This approach enables simultaneous waste utilization, along with Cl- and P-containing pollutant immobilization, offering a sustainable strategy for eco-friendly construction materials.

1. Introduction

The escalating climate crisis, driven by unprecedented levels of global CO2 emissions, has become one of the most pressing challenges of the 21st century. CO2 emissions account for approximately 39.6% of the global carbon footprint, making them a primary contributor to global warming and climate change [1]. To mitigate these effects, it is imperative to not only reduce CO2 emissions but also actively remove CO2 from the atmosphere, aiming for net-zero carbon emissions [2] and, ultimately, achieving carbon neutrality [3]. As of now, over 130 countries have committed to achieving net-zero carbon emissions and carbon neutrality, reflecting a global consensus on the urgency of addressing climate change [4]. Among the various strategies for CO2 sequestration, mineralization—a process that converts CO2 into stable carbonate minerals—has emerged as a promising approach. This process can be facilitated using naturally occurring minerals rich in calcium and magnesium, such as serpentine, olivine, basalt, and wollastonite, as well as alkaline industrial solid wastes, including fly ash (FA), steel slag (SS), carbide slag (CS), and blast furnace slag (BFS). Extensive research has demonstrated the feasibility of CO2 sequestration using both natural minerals [5,6] and industrial solid wastes (by-products) [7,8,9]. Renforth et al. [10] estimate that by the year 2100, alkaline materials could sequester between 2.9 and 8.5 billion tons of CO2 annually, highlighting the significant potential of this approach.
However, the utilization of natural minerals for CO2 mineralization is not without challenges. The extraction, grinding, and pretreatment of these minerals to enhance their reactivity are energy-intensive processes, which significantly increase the cost of mineral carbonation and hinder its large-scale deployment [11]. In contrast, alkaline industrial solid wastes, which are abundant in CaO and/or MgO, exhibit high reactivity and are produced in vast quantities globally. It is estimated that the direct and indirect use of these solid wastes for CO2 mineralization could reduce global CO2 emissions by approximately 4.02 gigatons annually [12]. Currently, a wide range of industrial solid wastes, including FA, SS, CS, and red mud (RM), have been identified as effective materials for CO2 sequestration, making their utilization a focal point of research and innovation.
Among these industrial by-products, FA, SS, CS, and RM are of particular interest due to their abundance and chemical composition. FA, a fine particulate by-product generated from the combustion of coal, biomass, or municipal solid waste, is a significant environmental concern due to its hazardous constituents [13]. Although FA is utilized in various sectors, including construction, chemical synthesis, and environmental engineering [14], its recycling efficiency remains limited, with only 30% of the total production being reused. The majority of FA is disposed of in landfills due to its low reactivity and heterogeneous nature. Global FA production is estimated at approximately 800 million tonnes annually, with China being the largest producer (500 million tonnes), followed by India (140 million tonnes) and the combined output of the USA and Europe (114 million tonnes) [15,16]. Similarly, SS, an inevitable by-product of metallurgical processes during primary and secondary steel production, is generated in substantial quantities worldwide. China alone produces over 100 million tonnes of SS annually, yet its utilization rate remains below 30% [17]. CS, another industrial residue, is an alkaline material predominantly composed of Ca(OH)2, with a wet-base pH ranging from 12 to 13. It is a by-product of acetylene gas production via calcium carbide hydrolysis [18], and its annual production in China exceeds 28 million tonnes [19]. RM, a highly alkaline solid waste generated during alumina oxide production [20], is produced at an average rate of 1.25 tonnes per tonne of alumina oxide [21]. According to the China Non-Ferrous Metals Industry Association, China’s RM production reached 107 million tonnes in 2023, with a utilization rate of 9.8%. Although this represents a significant improvement compared to previous years and positions China as a global leader in RM management [22], the overall utilization rate remains below 10% [23]. Consequently, the cumulative stockpile of RM in China has surpassed 800 million tonnes [24], creating severe environmental, safety, and land-use challenges.
The inefficient utilization of these industrial by-products poses a critical environmental and economic challenge. Open-pile storage, the predominant disposal method, not only occupies vast land resources but also contributes to environmental degradation, including air, water, and groundwater pollution [25,26]. Despite their adverse environmental impacts, these solid wastes possess considerable potential to contribute to ecological sustainability. However, realizing this potential requires addressing existing technical limitations and implementing innovative solutions to minimize their carbon footprint and mitigate environmental harm. By transforming these waste materials into valuable resources, it is possible to achieve a more sustainable and circular economy.
In recent years, significant progress has been made in the synthesis of novel alkali-activated materials (some geopolymers) using industrial waste materials (by-products). These geopolymers are typically produced through alkali activation techniques, utilizing the chemical components of industrial waste, such as CaO, MgO, SiO2, and Al2O3 [27,28,29]. Examples include the NaOH activation of FA-CS [30], the Na2SiO3 activation for FA-RM [31], the NaOH activation of FA–soda residue [32], and the NaOH activation of ground granulated blast furnace slag (GGBFS)-FA-RM [33], among others. To circumvent the high cost of industrial alkalis and the corrosive nature of high alkalis [34], a one-step or one-part mixing method has been employed to produce polymer materials [35,36,37]. Nonetheless, the use of high concentrations of strong alkalis can lead to carbonation and efflorescence in samples or products, potentially causing cracks and a decline in quality [38]. Currently, there is a trend toward combining multiple industrial wastes to produce cementitious materials, which helps to avoid the aforementioned issues. The integrated use of various solid-waste streams serves as a potent strategy to enhance the efficiency of producing cementitious composites [23,39,40]. In binary system materials, the effective chemical components involved in chemical cementation are usually limited. The types of solid waste involved in binary and ternary system materials are relatively few, making it difficult to achieve the synergistic utilization of diverse components. Quaternary system materials can provide diverse components, such as SiO2-Al2O3-CaO-Na2O, involved in the alkali activation process, making it easier to synthesize highly cementitious gel products and thereby achieve high-value and efficient utilization of multiple solid wastes. However, the synergistic mechanisms of quaternary waste systems (FA-RM-CS-SS) remain underexplored, with particular emphasis on selecting diverse industrial by-products characterized by massive stockpiles and low utilization rates.
Consequently, this study avoids the use of highly reactive GGBFS and synthesizes an FA-RM-CS-SS quaternary waste cementitious material by utilizing calcium phosphate and calcium hypochlorite as additives. The workability and mechanical strength of the samples were studied, the drying shrinkage characteristics of the hardened samples were measured, and the chemical composition, microstructure, and morphology of the samples were tested using SEM-EDS, XRD, FTIR, and TG-DSC methods. The macro and micro information obtained was used to reveal the fundamental mechanism of the quaternary waste cementation and the influence mechanism of calcium phosphate and calcium hypochlorite as additives. This provides experimental references for the sustainable solidification and recycling of polymeric waste.

2. Materials and Methods

2.1. Raw Materials

In this study, a novel cementitious composite was synthesized exclusively from industrial by-products, namely, fly ash (FA), red mud (RM), carbide slag (CS), and steel slag (SS). The chemical composition of these raw materials was analyzed using X-ray fluorescence (XRF) spectroscopy (ZSX Primus III+, Rigaku, Japan), with the results comprehensively presented in Table 1. To evaluate their potential for cementitious applications, key physical properties, such as specific gravity and surface area, were measured. Additionally, the morphological characteristics of the materials were examined using scanning electron microscopy (SEM), as illustrated in Figure 1. The mineralogical phases present in the by-products were identified through X-ray diffraction (XRD), and a detailed discussion of these findings is provided in Section 3.4.2.

2.1.1. Industrial By-Products

Fly ash (FA) was sourced from Gongyi Porun Casting Materials Co., Ltd. (Gongyi, Henan, China) and classified as low-calcium (CaO < 10%). The particle size distribution showed a maximum diameter of 10.0 μm, with an average of 2.0 μm. The material consisted of spherical glassy micro-spheres, indicating pozzolanic potential (Figure 1a). Its alkalinity (pH = 9.89) and electrical conductivity (1.68 mS/cm) were measured, as summarized in Table 2.
Red mud (RM) was obtained from the same supplier as FA and characterized by irregular granular morphology (Figure 1b). The chemical composition was dominated by SiO2 (27.50%), Al2O3 (28.40%), and Fe2O3 (25.80%). The high Na2O content (14.70%) contributed to its low alkalinity, influenced by carbonation and air-dried pretreatment (pH = 9.56, Table 2).
Carbide slag (CS), a Category II solid waste, was provided by Wuhu Environmental Protection Technology Co., Ltd. (Gongyi, Henan, China), derived from acetylene production via calcium carbide hydrolysis. The material exhibited agglomerated particles (Figure 1c) and a CaO-rich composition (78.86%). Its high pH (12.22) and conductivity (3.52 mS/cm) reflected strong alkaline properties (Table 2).
Steel slag (SS), a by-product of steelmaking processes [41], was supplied by Gongyi Porun Casting Materials Co., Ltd. (Gongyi, Henan, China), featuring angular particles (Figure 1d). The material contained substantial CaO (43.60%) and Fe2O3 (16.50%), with alkalinity (pH = 12.13) and conductivity (2.97 mS/cm) comparable to CS (Table 2).

2.1.2. Calcium Additives

Calcium hypochlorite (Ca(ClO)2), an analytical-grade oxidizing agent, was obtained from Kermel Chemical Reagent Co., Ltd. (Tianjin, China). The powder contained ≥35% active chlorine (Table 3) and formed an alkaline solution when dissolved in water (pH = 11.32, conductivity = 6.53 mS/cm).
Tricalcium phosphate (Ca3(PO4)2), sourced from Bohua Chemical Reagent Co., Ltd. (Tianjin, China), was used as a stabilizer and moisture retainer. The compound demonstrated limited water solubility (pH = 8.71, conductivity = 1.28 mS/cm) and met purity standards (≥34% active content; Table 3).

2.1.3. Other Components

Mixing water, sourced from Handan City, Hebei, China, was utilized for sample preparation and characterized by a neutral pH (7.3) and low conductivity (80.30 μS/cm).
Fine aggregates, composed of river sand with a fineness modulus of 2.62 and a density of 2.64 g/cm3, were incorporated into mortar samples for drying shrinkage assessment. The sand primarily consisted of quartz SiO2 (92%), with minor silicate and aluminosilicate impurities [38].

2.2. Sample Fabrication

Ten distinct formulations of paste and mortar samples were designed to investigate the synergistic effects of industrial by-products (FA, RM, CS, and SS) and calcium additives (CAs), comprising a 1:1 mass blend of Ca(ClO)2 and Ca3(PO4)2 (Table 4). Five paste groups (labeled “P*”) were prepared to assess the individual contributions of by-products in all-solid-waste systems, while five mortar groups (“DP*”) were fabricated to evaluate drying shrinkage according to the Chinese standard JC/T 603–2004 [42].
The raw materials—FA, RM, CS, and SS—were blended with the additive composite (Ca(ClO)2:Ca3(PO4)2 = 1:1) before mixing. For paste preparation, the solid mixture was homogenized with tap water through 3 min of high-speed mechanical stirring (Figure 2). The slurry was cast into steel molds, compacted, and cured at 25 °C (60% relative humidity) for 24 h before demolding. The paste or mortar was filled into the steel mold in two layers, with each layer vibrated for 60 s on a vibration compaction table—an instrument vibrated at a frequency of 1 Hz (once per second). Excess material was then removed using a metal straight edge to ensure a smooth surface, proper air void removal, and optimal compaction. Extended demolding periods (72 h) were required for FA-CA and FA-RM-CA samples due to delayed curing kinetics. Post-demolding, all specimens were immersed in water (25 °C and 100% humidity) to maintain hydration activity.
Mortar preparation involved the incorporation of river sand into a fresh paste, followed by 3 min of additional mixing to ensure uniformity (Figure 2). The “DP*” series was formulated with a water–binder ratio of 0.5 and a binder–sand ratio of 1:2. High-humidity curing conditions were maintained to optimize hydration reactions in the by-product-based systems, a critical factor for enhancing mechanical strength. The inclusion of Ca(ClO)2 and Ca3(PO4)2 aimed to improve compactness and structural integrity by promoting pore refinement and stabilizing hydration products.

2.3. Testing Methods

2.3.1. Determination of Fresh Properties

The pH values of fresh paste mixtures (P1–P5) were determined using a PHS-3G pH meter (Shanghai Raymagnet Co., Ltd., Shanghai, China) with ±0.01 accuracy. Calibration was performed with standard buffer solutions before measurements, and the electrode probe was positioned to avoid contact with container surfaces during testing.
Electrical conductivity (EC) was measured with a DDS–307A conductivity meter [32], capable of 0.01 mS/cm precision across a 0–100 mS/cm range (LABO-HUB, Toyohashi, Japan). A 10 cm−1 constant electrode probe was employed, and five spatially distributed measurements were collected to account for sample heterogeneity. Mean pH and EC values were recorded after homogenization but before fluidity testing.
The fluidity of the paste was evaluated through a standardized slump cone to quantify workability. For the slump cone test, fresh paste was prepared by homogenizing binders and water at a predefined water-to-binder (w/b) ratio using a planetary mixer. Fresh paste was poured into a standardized stainless steel slump cone (height: 60 mm; top diameter: 36 mm; bottom diameter: 60 mm) onto a smooth glass plate (400 × 400 mm). The testing procedure is as follows: (1) Pre-moisten the glass plate and slump cone with a damp cloth to minimize adhesion. (2) Position the slump cone centrally on the glass plate and fill it with fresh paste in one continuous pour. (3) Strike off excess paste using a straight edge and vertically lift the cone within 3–5 s. (4) Allow the paste to flow freely for 30 s, then measure the maximum flow diameter in two directions (0°, 90°) using a digital caliper. (5) Repeat the test in three parallel trials; report the average diameter (mm) with standard deviation [43,44]. If the result fell outside the valid range of 80–150 mm, the test was repeated after adjusting the water–cement ratio or mixing parameters. All tests were conducted under controlled environmental conditions (23 ± 2 °C, 50 ± 5% relative humidity).

2.3.2. Evaluation of Hardened Properties

Density evaluation of hardened pastes was conducted according to ASTM C830-00 standards [30,32,38,45]. Three replicate specimens were analyzed, with density calculated as the mass-to-volume ratio (g/cm3).
Compressive strength testing was performed on 40 mm cubic specimens at 28- and 90-day intervals using a DYE–300–10 servo-control testing machine (Tongli in Zuogezhuang, Hebei, China). The procedure followed GB/T 17671–2021 (ISO) [46], with loading applied at 2400 N/s. Strength values were derived from six parallel tests under identical conditions to ensure statistical reliability.
Drying shrinkage monitoring was implemented on 25 mm × 25 mm × 280 mm specimens over 90 days, complying with JC/T 603–2004 [42]. After 3 days of initial curing, specimens were transferred to controlled environments (25 °C and 60% RH). Shrinkage measurements were acquired using a BC156–300 precision length comparator (Lisheng, Cangzhou, China), with triplicate samples averaged for each data point.
Mortar formulations for shrinkage assessment maintained a 1:2 binder–sand ratio and 0.5 water–binder ratio (Table 4). Flowability was controlled within 130–170 mm to ensure molding consistency. Notably, DP1 and DP2 specimens exhibited insufficient cementation under ambient conditions, resulting in structural disintegration during water curing. Consequently, shrinkage data were only obtained for DP3, DP4, and DP5 specimens.

2.3.3. Detection of Micro-Characteristics

Microstructural characterization of 90-day cured all-solid-waste paste samples (P1, P2, P3, P4, and P5) was conducted through SEM-EDS, XRD, FTIR, and TG-DSC analyses.
SEM-EDS analysis was performed on gold-sputtered specimens using a TESCAN MIRA LMS equipment (Brno, Czech Republic) coupled with an Oxford Smartedx EDS detector (Zeiss, Oxford, UK). Elemental mapping and morphological features were examined at selected regions to assess phase distribution and interfacial bonding. EDS spectroscopy was employed to examine the elemental composition of selected regions in the 90-day samples. Morphological analysis was conducted at an accelerating voltage of 5 kV, while spectroscopic measurements were performed at 15 kV.
XRD patterns were acquired with a Rigaku SmartLab-SE diffractometer (Rigaku, Tokyo, Japan) under Cu-Kα radiation (40 kV, 40 mA). Scans were conducted from 10° to 80° 2θ at 2°/min, with data refinement executed via MDI Jade 6.5 software [47].
FTIR spectra were obtained using a Thermo Scientific Nicolet iS20 spectrometer (Waltham, MA, USA) to identify characteristic functional groups and hydration products. Samples dried at 45 °C for 48 h and milled to 2.0 μm were homogenized with KBr (1:100 ratio) and pelletized under 20 MPa pressure. Spectra were collected at 4 cm−1 resolution across 32 scans.
Thermal stability was evaluated through TG-DSC measurements using a PerkinElmer STA 8000 analyzer (Waltham, MA, USA). Specimens (9–10 mg) were heated from 30 °C to 1000 °C at 15 °C/min under airflow to quantify the mass loss and identify phase transitions.

3. Results

3.1. Fresh Properties of All-Solid-Waste Materials

The fresh properties of all-solid-waste pastes were analyzed to evaluate the influence of material composition on pH, electrical conductivity (EC), and flowability. Distinct variations in these parameters were observed across formulations, as illustrated in Figure 3.
The FA-CA mixture exhibited a flowability of 131 mm, EC of 4.75 mS/cm, and pH of 12.03. The incorporation of RM into the FA-RM-CA system increased flowability and EC, while the substitution of FA with CS and RM (FA-RM-CS-CA) reduced all three parameters. The further inclusion of SS (FA-RM-CS-SS-CA) elevated flowability and pH, with negligible EC variation. The removal of additives in FA-RM-CS-SS-00 decreased flowability and EC but increased pH. The pH and EC of fresh pastes were primarily governed by CS, SS, and Ca(ClO)2 (Table 2). Elevated EC in FA-RM-CS-CA was attributed to the high alkalinity of CS, which increased soluble ion concentrations [48]. The pH rise in FA-RM-CS-SS-CA correlated with the alkaline SS content [49]. The absence of Ca(ClO)2 in FA-RM-CS-SS-00 reduced EC significantly due to diminished ionic contributions.
The fluidity data reveal that material composition critically impacts flowability through competing mechanisms of particle packing, water demand, and chemical interactions. The combination of FA and CAs yielded moderate fluidity (131 mm), while adding RM enhanced flowability to 140 mm due to its alkaline ions (Na+/K+), improving electrostatic repulsion and fine particles, and optimizing packing density. However, introducing CS drastically reduced fluidity to 86 mm, as its irregular morphology and excessive Ca(OH)2 content increased water absorption and induced premature coagulation. Partial recovery occurred when SS was incorporated (106 mm), likely due to its glassy phases acting as micro-aggregates to reduce friction, with CAs mitigating water demand. Notably, omitting CAs in the same mixture lowered fluidity to 98 mm, underscoring their role in particle dispersion via zeta potential modulation. Key factors include the balance between fine particles (enhancing packing) and coarse/angular materials (disrupting flow), ionic effects (alkali ions vs. Ca2+-induced coagulation), and additive-driven lubrication. Optimizing the CS content and CA dosage is essential to harmonize sustainability and workability in multi-component systems.
These findings demonstrate the critical roles of CS and SS in regulating ionic environments and pH during fly ash solidification. CS enhanced ion solubility through alkaline dissolution, SS stabilized pH via buffering capacity, and Ca(ClO)2 optimized EC by introducing mobile chloride ions. The interplay between these components highlights the importance of compositional balance in achieving target fresh-state properties.

3.2. Hardened Properties of All-Solid-Waste Materials

Water-curing stability was evaluated across formulations, with FA-CA (P1) and FA-RM-CA (P2) exhibiting rapid disintegration upon immersion (Figure 4). The fine particle size and low alkalinity of RM, while serving as micro-aggregates during polymerization [36], were compromised by its sodium content. In contrast, CS- and SS-containing samples demonstrated enhanced stability under identical conditions.
The compressive strength and density data are presented in Figure 5. FA-RM-CS-CA (P3), FA-RM-CS-SS-CA (P4), and FA-RM-CS-SS-00 (P5) exhibited progressive strength and density gains at 28 and 90 days (Figure 5a). The 90-day strength of P3, P4, and P5 increased by 110%, 100%, and 140% relative to their 28-day values, respectively. These improvements were attributed to sustained hydration reactions and gel formation, which enhanced interparticle bonding [19]. P3 benefits from dual calcium sources (CS and CAs), promoting a stable hydrated gel network [50]. The alkaline RM environment and FA’s pozzolanic effect synergistically enhance later-age strength. P4 incorporates SS, introducing Fe and Mg, which diversify hydration products and form an interwoven structure with ettringite. CAs further optimize hydration kinetics, supporting strength development. P5, despite lacking CAs, leverages SS components for slower but sustained late-stage hydration, yielding more gel. Free CaO in SS may compensate for calcium deficiency, contributing to the significant strength increase. The functions of the raw materials and the compressive strength results are consistent with the subsequent microstructural test findings (Section 3.4). The inclusion of CS in P3 elevated the Ca(OH)2 content, promoting aluminosilicate compound synthesis and strength development [25]. SS addition introduced divergent effects on mechanical performance. While P4 showed a 16.2% strength reduction compared to P3 at 90 days, P5 (25% SS and additive-free) achieved a 15.2% strength increase over P3. After 90-day curing, P5 attained 16.7 MPa strength and 1.75 g/cm3 density (Figure 5b), demonstrating effective solidification through synergistic hydration. The mechanical limitations of SS were linked to its compositional characteristics. P4 achieved lower strength (14.5 MPa) despite higher density (1.78 g/cm3), a phenomenon associated with inert components and low C2S reactivity in SS exceeding 20% content [23,51]. Brittle failure modes with vertical/diagonal cracks were observed in P3, P4, and P5 under compressive loading (Figure 5c), indicating retained structural integrity despite delayed strength development in SS-containing systems.
Delayed hydration kinetics in SS-rich formulations were attributed to slow C2S dissolution. This phase-limited reaction impeded late-stage hydration product formation, as reported in analogous systems [23,51]. The results underscore the need for optimized SS dosage to balance microstructural refinement and reactivity constraints.

3.3. Drying Shrinkage Properties of All-Solid-Waste Materials

Drying shrinkage evolution in DP3, DP4, and DP5 mortar samples was monitored over 90 days, with stabilization observed after 50 days (Figure 6). This behavior aligns with reported shrinkage patterns in alkali-activated systems such as phosphogypsum–soda residue–CS composites [19], FA–salt-loss soda residue binders [32], and FA-CS-based materials [30,45,52,53]. SS substitution in DP4 increased drying shrinkage from −15.67 × 10−4 (DP3) to −21.08 × 10−4. This enhancement was linked to SS-derived free CaO and MgO, which promoted delayed hydration and expansive crystalline product formation, generating microcracks and elevated porosity [54]. The coarser SS particle size further reduced the capillary pore-filling capacity, amplifying capillary tension during moisture loss [55]. Additive incorporation (Ca(ClO)2 + Ca3(PO4)2) reduced shrinkage by 8.7% between DP4 (−23.09 × 10−4) and DP5 (−21.08 × 10−4). Statistical significance (p < 0.05) was confirmed through triplicate testing (standard deviation < 5%).

3.4. Micro-Characterization of All-Solid-Waste Materials

3.4.1. Morphological and Compositional Analysis via SEM-EDS

Microstructural analysis of P1 and P2 samples reveals cementation failure between FA and additives. In P1 (FA-CA), FA spherical glass beads retained smooth surfaces without gel formation (Figure 7a). Partial RM substitution in P2 (FA-RM-CA) similarly showed no interfacial bonding, leaving FA particles unreacted (Figure 7a). These observations correlate with rapid disintegration during water curing (Section 3.2, Figure 4).
Effective cementation was observed in P3–P5 samples, characterized by rough-surfaced spherical glass beads embedded in gel matrices (Figure 7b–d). The dense microstructure of P3 and P4 (Figure 7b,c) aligned with their superior compressive strength (Figure 5a), indicating C-S-H and aluminosilicate polymer (x-A-S-H) gel formation. EDS analysis confirms these hydration products as key contributors to mechanical enhancement. Cementation failure in P1 and P2 was attributed to the insufficient activation of RM under dry conditions. The lower alkalinity of dried RM [56,57] limited its ability to react with FA-derived SiO2 and Al2O3, preventing gel network development [58]. This contrasts with conventional assumptions regarding FA-RM-CA system stability.
EDS elemental mapping of P3-P5 specimens (Figure 8) identifies distinct Fe distribution patterns. P3 exhibited higher Fe content and localized enrichment compared to P4, reflecting SS incorporation. Unreacted FA particles were detected as Si/Al-rich regions, with P4 showing surface-embedded glass microspheres indicative of incomplete hydration. These findings corroborate the 16.2% strength reduction in P4 relative to P3 (Section 3.2). Uniform Fe distribution in P4 was achieved through additive-induced iron salt dissolution. Calcium additives (CAs) in P4 facilitated Fe dispersion within the matrix, reducing localized enrichment [59]. This phenomenon was further validated by XRD analysis (Section 3.4.2).
The functional roles of components were clarified through microstructural evidence. CS provided soluble calcium for gel formation, while SS acted as a micro-aggregate, reinforcing the skeletal framework. Although CAs did not enhance strength, they promoted Fe homogeneity, mitigating phase segregation risks.

3.4.2. Mineralogical Phase Analysis via XRD

Mineralogical phases in hydration products were identified through XRD analysis of the P1-P5 samples and raw materials (Figure 9). The raw by-products exhibited distinct compositions: FA contained mullite (3Al2O3·2SiO2) and quartz (SiO2), RM comprised Ca(OH)2, SiO2, and iron salts, CS included Ca(OH)2, CaCO3, MgO, and SiO2, and SS consisted of Ca(OH)2, CaCO3, and iron salts (Figure 9a). CaCO3 formation in CS and SS was attributed to carbonation processes [60,61], which enhanced microstructural densification through pore filling [62].
Novel hydration phases were detected in additive-containing systems. In P1 (FA-CA), the interaction between CAs and FA-derived silicates/aluminates produced Ca4Si3O10·8H2O (Figure 9b). P2 (FA-RM-CA) generated (Na,K)₆Ca2(AlSiO4)₆Cl4 and Fe-Al-P-O phases (Fe10S11 and FeAl2(PO4)2(OH)2·8H2O). These crystalline products correlated with weak cementation, consistent with the mechanical data (Figure 4 and Figure 5). CS incorporation in P3 (FA-RM-CS-CA) promoted x-A-S-H gel formation alongside Fe2PO4·2H2O and CaCl2·2H2O. The diversity of silicate phases (x = Na, K, Ca, Fe, and Mg) indicated enhanced reactivity due to CS-derived Ca2+, which activated FA and RM components. In contrast, P4 (FA-RM-CS-SS-CA) exhibited Fe₈(OH)1₆(C2O4)·3H2O and KFe3(SiFe)O10(OH)2 but lacked crystalline x-A-S-H, suggesting SS inhibited silicate crystallization [63]. CA-free P5 (FA-RM-CS-SS-00) formed NaCa(SiAl)20O40·8H2O and Mg-Al-CO3 hydrotalcite-like phases. This confirmed CAs’ role in suppressing x-A-S-H crystallization in multi-component systems. Under normal circumstances, the crystalline state of x-A-S-H exhibits higher strength than the amorphous state. The addition of CAs causes the x-A-S-H to tend toward an amorphous product, reducing the cementation degree of the sample and leading to a decrease in the compressive strength of the final sample (i.e., the compressive strength of P4 is lower than that of P5, Figure 5a). The absence of CAs allowed natural alkali activation, yielding stable aluminosilicate networks. Phase evolution trends reveal additive-specific effects. CAs facilitated PO43− and Cl− release via Ca3(PO4)2 and Ca(ClO)2 dissolution [59], driving Fe dispersion and amorphous gel formation. However, SS addition (P4) introduced inert Fe components that competed with silicate polymerization, reducing the crystalline phase content.
These findings highlight the trade-offs between component interactions and hydration product crystallinity. While CS enhanced gel network development, SS and CAs modulated phase stability, emphasizing the need for balanced formulations in all-solid-waste systems.

3.4.3. Chemical Bond Analysis via FTIR

The FTIR spectra of cured samples (P1, P2, P3, P4, and P5) were analyzed to identify functional group variations and chemical bonding shifts (Figure 10). Key absorption bands were correlated with specific vibrational modes to elucidate hydration mechanisms. Significant absorption peaks in the 963–1069 cm−1 range were assigned to Si–O–T (T = Si/Al) asymmetric stretching vibrations [64,65]. Carbonate CO32− stretching modes were detected at 1417–1448 cm−1 [4], while a broad band at 3400–3523 cm−1 indicated interlayer water in silicate/aluminosilicate hydrates [66,67]. The CS spectrum exhibited a distinct the peak from the -OH bond of Ca(OH)2 at 3643 cm−1 [68].
In P1 (FA-CA), a 3 cm−1 shift in the Si–O–T stretching band (1072 → 1069 cm−1) suggests limited silicate network formation. This observation aligns with the SEM images showing unreacted FA particles with smooth surfaces (Figure 7a), indicating insufficient alkali activation by CAs to initiate aluminosilicate polymerization. P2 (FA-RM-CA) showed no Si–O–T wavenumber shifts relative to RM, consistent with the SEM evidence of poor FA-RM interfacial bonding (Figure 7a). The absence of new vibrational modes confirmed RM’s inability to activate FA under dry conditions [56,57]. A 104 cm−1 Si–O–T wavenumber reduction (1072 → 968 cm−1) was observed in P3 (FA-RM-CS-CA) compared to FA. The concurrent disappearance of the Ca(OH)2 peak (3643 cm−1) confirms CS-driven activation, facilitating Si–O–Al chain polymerization into calcium silicate/aluminosilicate gels [69,70]. These findings correlate with the SEM-detected gel-coated microstructures (Figure 7b). P4 (FA-RM-CS-SS-CA) exhibited minimal Si–O–T shift relative to P3, suggesting analogous aluminosilicate formation. The SEM-observed gel matrices (Figure 7c) support this conclusion, demonstrating SS compatibility with the hydration process despite its inert components [23,51]. CA removal in P5 induced an 8 cm−1 Si–O–T band shift to lower wavenumbers, confirming CAs’ role in promoting Si–O–Si polymerization [71,72]. The resultant spectra indicate composite silicate–aluminosilicate gel formation in P4, with CAs enhancing silicate phase development.
The correlations between FTIR and SEM establish structure–property relationships across formulations. While CS enabled effective activation through Ca2+ release, CAs optimized silicate network connectivity. The incorporation of SS maintained gel formation but did not alter fundamental bonding mechanisms, validating its role as a micro-aggregate rather than a reactive phase.

3.4.4. Thermal Behavior Analysis via TG-DSC

The thermal decomposition profiles of P3-P5 hydration products were characterized through TG-DSC measurements (Figure 11). Mass loss events and endothermic transitions were correlated with phase transformations to assess material stability. Three-stage decomposition was identified in P3 through DTG peak analysis (Figure 11a). Initial mass losses (19.518%) at 70.17 °C and 142.35 °C were attributed to interlayer water release from C-A-S-H gels [19,32]. Ca(OH)2 decomposition at 270.52 °C contributed 2.933% mass loss [73], while CaCO3 decarbonization at 453.52 °C and 693.48 °C resulted in 5.992% total loss [74,75]. The peak temperature variations reflect the CaCO3 crystallinity differences and experimental parameters [4]. Similar decomposition patterns were observed in P4 and P5 (Figure 11b,c). P4 exhibited 18.645% (70.77–143.54 °C), 3.123% (270.66 °C), and 8.239% (456.02–712.73 °C) mass losses. P5 demonstrated 13.548% (67.92–143.93 °C), 3.236% (269.25 °C), and 8.578% (458.00–707.53 °C) losses. Delayed CaCO3 decomposition was detected in CA-containing systems. The DSC curve of P4 showed CaCO3 decarbonation initiating at 693.69 °C, 17.28 °C higher than P5 (676.41 °C). This indicates CA-enhanced thermal stability through delayed carbonate breakdown. A total of 200–1000 °C mass losses were ranked as P3 (8.925%) < P4 (11.362%) < P5 (11.814%), correlating with the gel content variations. Enhanced thermal resistance in P3 was linked to its dense gel matrix. The abundant C-A-S-H gels in P3 reduced Ca(OH)2/CaCO3 exposure, limiting the decomposition extent. This microstructure–property relationship aligns with its superior mechanical performance (Section 3.2).
These findings demonstrate CAs’ dual role in modifying hydration kinetics and thermal stability. While promoting gel formation, CAs delayed carbonate decomposition through chemical interactions, offering insights for the high-temperature application design of all-solid-waste cementitious materials.

4. Discussion

This study focuses on blending four low-activity industrial by-products—FA, RM, CS, and SS—to leverage their respective chemical and physical advantages, thereby developing a novel cementitious material (Sample P5). This study aims to explore the feasibility of utilizing industrial solid wastes (fly ash, red mud, carbide slag, and steel slag) as substitutes for traditional cementitious materials (e.g., cement) to develop low-carbon and sustainable building materials (e.g., grouting materials). By sequentially adding red mud, copper slag (CS), and steel slag to fly ash, the role of the raw materials was revealed. The fresh properties, hardened performance, and microstructural bonding mechanisms of this composite cementitious material were further characterized. The research findings indicate that with a mixing ratio of 1:1:1:1 for the four industrial by-products and a water-to-binder ratio of 0.46, a compressive strength of 16.7 MPa can be achieved after 90 days. Synergy theory, a key concept in the realm of waste recycling and cementitious material synthesis, has garnered significant attention. Extensive research indicates that composite materials derived from mixed solid wastes exhibit superior workability and mechanical qualities attributed to the synergistic interactions of elements like Ca, Si, Al, Na, and S [76,77]. However, there are few examples of the synergistic use of multiple solid wastes, and there are binary [34], ternary [33,78], quaternary [19], and even polymeric solid-waste systems [37], leading to significant variations in the chemical and mechanical properties of the synthesized samples. Table 5 lists some examples of polymeric waste cementitious systems and their mechanical strengths. It is evident that to achieve higher strengths, most multi-waste cementitious materials have employed highly reactive GGBFS to increase the synthesis of cementitious products in the system [79,80]. However, existing studies primarily focus on binary or ternary systems, while the synergistic mechanisms of quaternary waste systems (FA-RM-CS-SS) remain underexplored, particularly regarding the role of additives in enhancing stability. Compared to ternary systems (e.g., GGBFS-CS-SR with 43 MPa [81]), the quaternary FA-RM-CS-SS system achieves comparable strength (16.7 MPa) while utilizing 100% industrial by-products, significantly reducing reliance on high-reactivity GGBFS. Recent studies on multi-waste systems focus on various waste combinations, while our work pioneers the integration of four industrial by-products, addressing the challenge of low-activity waste synergy.
As shown in Table 5, the compressive strength of the GGBFS-FA-SS-RM quaternary system sample was close to 13.5 MPa [45], while that of the GGBFS-FA-RM-CS quaternary system sample ranged from 6.0 to 6.5 MPa [43,82]. In this study, the 90-day compressive strength of the quaternary system synthesized with FA, RM, CS, and SS reached 16.7 MPa, indicating that the compressive strength of the multi-solid-waste sample P5 in this study is comparable to or even higher than that of the GGBFS-containing quaternary systems. This is attributed to the synergistic effects of diverse solid wastes in the addition of the water-to-solid ratio of mixtures. Therefore, in the application of multi-solid-waste cementitious materials, CS can replace highly reactive GGBFS; in some cases, SS can also substitute for the function of GGBFS.
Table 5. Representative cases of full-solid-waste cementitious systems and their mechanical properties.
Table 5. Representative cases of full-solid-waste cementitious systems and their mechanical properties.
CasesFull-Solid-Waste Compositions28 d Compressive
Strengths (MPa)		References
BinaryFA-SS18.8[73]
BinaryGGBFS-SR2.4[83]
TernaryGGBS-CS-SR43.0[81]
TernaryGGBFS-FA-RM~9.5[84]
TernaryGGBFS-SS–Desulfurized gypsum—[85]
TernaryBFS-APG-CS51.42[25]
TernaryFA-SS–Desulfurization gypsum5.0–50.0[73]
TernaryGGBFS-SS–β-hemihydrate
phosphogypsum		1.9–31.6[86]
TernaryGGBFS-SS-CS41.5[87]
TernaryGGBFS-CS–Iron tailings2.89[88]
QuaternaryGGBFS-SR-CS-PG43.9[19]
QuaternaryGGBFS-FA-SS-RM~13.5[45]
QuaternaryGGBFS-FA-RM–Eggshell particles8.0–12.0[84]
QuaternaryGGBFS-FA-RM-CS~6.5[43]
QuaternaryBFS-RM-SS–Flue gas
desulfurization gypsum		3.0–18.0[23]
QuaternaryGGBFS-FA-RM-CS6.0[82]
QuaternaryGGBFS-FA-SF-CS–Gypsum15.0–30.0[89]
QuaternaryGGBFS-MK-CS–Waste mud>3.0[90]
Note: PG—phosphogypsum; GGBFS—ground granulated blast furnace slag; CS—carbide slag; SR—soda residue; FA—fly ash; RM—red mud; SS—steel slag; APG—anhydrous phosphogypsum; BFS—blast furnace slag; SF—silica fume; MK—metakaolin.
Additionally, by incorporating calcium additives (a mixture of Ca(ClO)2 and Ca3(PO4)2) into the FA-RM-CS-SS system, a compressive strength of 14.5 MPa was achieved after 90 days (Sample P4). Although the compressive strength decreased compared to Sample P5, the drying shrinkage rate was reduced by 8.7%. Ca(ClO)2 and Ca3(PO4)2, as contaminants containing Cl and P can be immobilized within the FA-RM-CS-SS system. Meanwhile, as calcium ion providers, Ca(ClO)2 and Ca3(PO4)2 can promote the synthesis of hydration products in the FA-RM-CS-SS system. The mechanism involved dual stabilization:
I.
Ca(ClO)2 accelerated early hydration, forming dense C-S-H gels that restricted moisture migration pathways [91,92]:
Ca(ClO)2 + Ca(OH)2 → Ca(OCl)2·Ca(OH)2
II.
Ca3(PO4)2 reacted with Ca(OH)2 to produce hydroxyapatite, stabilizing pH at ~12.5 and inhibiting dissolution–reprecipitation shrinkage [93]:
Ca3(PO4)2 + 3Ca(OH)2 → 3Ca(OH)2·Ca3(PO4)2
Phosphate ions additionally suppressed ettringite recrystallization via Al3+ complexation [94].
This dual modification strategy demonstrated synergistic matrix densification and pollutant immobilization. Chlorine and phosphorus were chemically encapsulated, suggesting potential applications in environmental remediation [95,96]. The approach effectively mitigated both physical (capillary stress) and chemical (phase transition) shrinkage mechanisms, advancing the development of dimensionally stable all-solid-waste cementitious materials.
However, the compressive strength of the FA-RM-CS-SS system samples (P4 and P5) exhibited a sharp increase from 28 to 90 days, indicating a significant age effect. Therefore, future research should focus on the long-term stability of multi-solid-waste composite cementitious materials.

5. Conclusions

This study pioneers the integration of four low-activity industrial by-products (FA, RM, CS, and SS) into a cementitious system. Through the characterization of fresh properties, hardened properties, and microstructures, it reveals the synergistic effects of raw materials and the impact of additives. Below are the key findings and implications:
(1)
A novel cementitious system was developed through the synergistic integration of four low-activity industrial by-products (FA, RM, CS, and SS), achieving 16.7 MPa compressive strength (higher than other samples) with 100% solid-waste utilization (without any additives). This breakthrough demonstrates the feasibility of creating high-performance construction materials without conventional binders, addressing both waste valorization and carbon footprint reduction;
(2)
The dual additives Ca(ClO)2 and Ca3(PO4)2 were shown to enable multifunctional enhancement, reducing drying shrinkage while immobilizing Cl− and PO43− pollutants. Ca(ClO)2 accelerated C-S-H gel formation, whereas Ca3(PO4)2 stabilized pH through hydroxyapatite precipitation, collectively mitigating chemical shrinkage mechanisms;
(3)
An optimal SS content (≤20%) was identified as critical for balancing micro-aggregate reinforcement and reactivity suppression. While SS addition delayed long-term strength development due to inert C2S components, its role in reducing drying shrinkage and maintaining dimensional stability proved essential for practical applications.
The environmental remediation functionality was integrated into the cementitious system via pollutant encapsulation. Unlike traditional CaO/Ca(OH)2 activators, the additives chemically immobilize chlorine and phosphorus, offering dual benefits of material performance and contaminant sequestration. This work establishes a paradigm for designing circular construction materials, with future research needed to validate long-term durability under field conditions. These findings advance sustainable engineering practices by transforming multi-source industrial wastes into value-added composites with engineered functionality.

Author Contributions

Conceptualization, L.J.; data curation, H.W.; formal analysis, H.W.; funding acquisition, X.Z.; investigation, L.J. and X.Z.; methodology, L.J.; project administration, H.W.; resources, X.Z.; software, X.Z.; supervision, X.Z.; validation, X.Z. and H.W.; writing—original draft, L.J.; writing—review and editing, X.Z. and H.W. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Tianjin Research Innovation Project for Postgraduate Students, grant number 2021KJ078.

Data Availability Statement

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

Conflicts of Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in the paper.

References

  1. Yoro, K.; Daramola, M. CO2 emission sources, greenhouse gases, and the global warming effect. In Advances in Carbon Capture; Woodhead Publishing: Sawston, UK, 2020; pp. 3–28. [Google Scholar] [CrossRef]
  2. Fankhauser, S.; Smith, S.M.; Allen, M.; Axelsson, K.; Hale, T.; Hepburn, C.; Kendall, J.M.; Khosla, R.; Lezaun, J.; Mitchell-Larson, E.; et al. The meaning of net zero and how to get it right. Nat. Clim. Change 2022, 12, 15–21. [Google Scholar] [CrossRef]
  3. Chen, L.; Msigwa, G.; Yang, M.; Osman, A.I.; Fawzy, S.; Rooney, D.W.; Yap, P.-S. Strategies to achieve a carbon neutral society: A review. Environ. Chem. Lett. 2022, 20, 2277–2310. [Google Scholar] [CrossRef] [PubMed]
  4. Wang, C.; Jiang, H.; Miao, E.; Wang, Y.; Zhang, T.; Xiao, Y.; Liu, Z.; Ma, J.; Xiong, Z.; Zhao, Y.; et al. Accelerated CO2 mineralization technology using fly ash as raw material: Recent research advances. Chem. Eng. J. 2024, 488, 150676. [Google Scholar] [CrossRef]
  5. Matter, J.M.; Stute, M.; Snæbjörnsdottir, S.Ó.; Oelkers, E.H.; Gislason, S.R.; Aradottir, E.S.; Sigfusson, B.; Gunnarsson, I.; Sigurdardottir, H.; Gunnlaugsson, E.; et al. Rapid carbon mineralization for permanent disposal of anthropogenic carbon dioxide emissions. Science 2016, 352, 1312–1314. [Google Scholar] [CrossRef]
  6. Chen, M.; Wang, C.; Shi, Q.; Hu, H.; Zhang, Q.; Li, Z. Enhanced simultaneous CO2 mineralization and cadmium immobilization in a wide pH range by using ball-milled serpentine. Chem. Eng. J. 2023, 474, 145558. [Google Scholar] [CrossRef]
  7. Cheng, C.; Huang, W.; Xu, H.; Liu, Z.; Li, X.; Shi, H.; Yu, Y.; Qu, Z.; Yan, N. CO2 sequestration and CaCO3 recovery with steel slag by a novel two-step leaching and carbonation method. Sci. Total Environ. 2023, 891, 164203. [Google Scholar] [CrossRef]
  8. Li, C.; Li, Y.; Zhu, W.; Zeng, G.; Ouyang, Z.; Cheng, M.; Jiang, Z. Carbon dioxide cured building materials as an approach to decarbonizing the calcium carbide related industry. Renew. Sustain. Energy Rev. 2023, 186, 113688. [Google Scholar] [CrossRef]
  9. Ren, S.; Aldahri, T.; Liu, W.; Liang, B. CO2 mineral sequestration by using blast furnace slag: From batch to continuous experiments. Energy 2021, 214, 118975. [Google Scholar] [CrossRef]
  10. Renforth, P. The negative emission potential of alkaline materials. Nat. Commun. 2019, 10, 1401. [Google Scholar] [CrossRef]
  11. Bobicki, E.R.; Liu, Q.; Xu, Z.; Zeng, H. Carbon capture and storage using alkaline industrial wastes. Prog. Energy Combust. Sci. 2012, 38, 302–320. [Google Scholar] [CrossRef]
  12. Pan, S.-Y.; Chen, Y.-H.; Fan, L.-S.; Kim, H.; Gao, X.; Ling, T.-C.; Chiang, P.-C.; Pei, S.-L.; Gu, G. CO2 mineralization and utilization by alkaline solid wastes for potential carbon reduction. Nat. Sustain. 2020, 3, 399–405. [Google Scholar] [CrossRef]
  13. Grabias-Blicharz, E.; Franus, W. A critical review on mechanochemical processing of fly ash and fly ash-derived materials. Sci. Total Environ. 2023, 860, 160529. [Google Scholar] [CrossRef]
  14. Zhang, Y.; Wang, L.; Chen, L.; Ma, B.; Zhang, Y.; Ni, W.; Tsang, D.C.W. Treatment of municipal solid waste incineration fly ash: State-of-the-art technologies and future perspectives. J. Hazard. Mater. 2021, 411, 125132. [Google Scholar] [CrossRef]
  15. Bandura, L.; Panek, R.; Madej, J.; Franus, W. Synthesis of zeolite-carbon composites using high-carbon fly ash and their adsorption abilities towards petroleum substances. Fuel 2021, 283, 119173. [Google Scholar] [CrossRef]
  16. Belviso, C. State-of-the-art applications of fly ash from coal and biomass: A focus on zeolite synthesis processes and issues. Prog. Energy Combust. Sci. 2018, 65, 109–135. [Google Scholar] [CrossRef]
  17. Zhang, W.; Hao, X.; Wei, C.; Liu, X.; Zhang, Z. Activation of low-activity calcium silicate in converter steelmaking slag based on synergy of multiple solid wastes in cementitious material. Constr. Build. Mater. 2022, 351, 128925. [Google Scholar] [CrossRef]
  18. Namarak, C.; Satching, P.; Tangchirapat, W.; Jaturapitakkul, C. Improving the compressive strength of mortar from a binder of fly ash-calcium carbide residue. Constr. Build. Mater. 2017, 147, 713–719. [Google Scholar] [CrossRef]
  19. Wang, D.; Zhang, Z.; Guo, W.; Li, J.; Li, X.; Zhao, Q. A novel all-solid-waste binder prepared by salt-alkali synergistic activation system constructed from phosphogypsum, soda residue and calcium carbide slag. Cem. Concr. Compos. 2025, 155, 105841. [Google Scholar] [CrossRef]
  20. Kumar, A.; Saravanan, T.J.; Bisht, K.; Kabeer, K.I.S.A. A review on the utilization of red mud for the production of geopolymer and alkali activated concrete. Constr. Build. Mater. 2021, 302, 124170. [Google Scholar] [CrossRef]
  21. Niu, A.; Lin, C. Trends in research on characterization, treatment and valorization of hazardous red mud: A systematic review. J. Environ. Manag. 2024, 351, 119660. [Google Scholar] [CrossRef]
  22. Qingke, N.; Haiqing, Z.; Haipeng, Y.; Xiangxin, J.; Rihua, Z. Development and field test of Red mud-Fly Ash Geopolymer pile (RFP). Clean. Waste Syst. 2024, 9, 100184. [Google Scholar] [CrossRef]
  23. Zhang, J.; Li, S.; Li, Z. Investigation the synergistic effects in quaternary binder containing red mud, blast furnace slag, steel slag and flue gas desulfurization gypsum based on artificial neural networks. J. Clean. Prod. 2020, 273, 122972. [Google Scholar] [CrossRef]
  24. Wang, S.; Jin, H.; Deng, Y.; Xiao, Y. Comprehensive utilization status of red mud in China: A critical review. J. Clean. Prod. 2021, 289, 125136. [Google Scholar] [CrossRef]
  25. Zhao, Y.; Zhou, X.; Zhou, Q.; Zhu, H.; Cheng, F.; Chen, H. Development of full-solid waste environmentally binder for cemented paste backfill. Constr. Build. Mater. 2024, 443, 137689. [Google Scholar] [CrossRef]
  26. Zhang, Q.; Feng, P.; Shen, X.; Cai, Y.; Zhen, H.; Liu, Z. Comparative analysis of carbonation strengthening mechanisms in full solid waste materials: Steel slag vs. carbide slag. Cem. Concr. Compos. 2025, 157, 105927. [Google Scholar] [CrossRef]
  27. Li, L.; Xie, J.; Zhang, B.; Feng, Y.; Yang, J. A state-of-the-art review on the setting behaviours of ground granulated blast furnace slag- and metakaolin-based alkali-activated materials. Constr. Build. Mater. 2023, 368, 130389. [Google Scholar] [CrossRef]
  28. Nasir, M.; Johari, M.A.M.; Maslehuddin, M.; Yusuf, M.O.; Al-Harthi, M.A. Influence of heat curing period and temperature on the strength of silico-manganese fume-blast furnace slag-based alkali-activated mortar. Constr. Build. Mater. 2020, 251, 118961. [Google Scholar] [CrossRef]
  29. Chen, Z.; Chen, P.; Li, S.; Shen, X.; Fang, J.; Gu, Z.; Wang, Y. Enhancing the performance of NaOH-activated slag using waste green tea extract as a multi-function admixture. Case Stud. Constr. Mater. 2024, 21, e03605. [Google Scholar] [CrossRef]
  30. Zhao, X.; Wang, H.; Jiang, L.; Meng, L.; Zhou, B.; Zhang, J. Long-Term Physical and Mechanical Properties and Microstructures of Fly-Ash-Based Geopolymer Composite Incorporating Carbide Slag. Materials 2021, 14, 6692. [Google Scholar] [CrossRef]
  31. Bai, B.; Chen, J.; Bai, F.; Nie, Q.; Jia, X. Corrosion effect of acid/alkali on cementitious red mud-fly ash materials containing heavy metal residues. Environ. Technol. Innov. 2024, 33, 103485. [Google Scholar] [CrossRef]
  32. Wang, H.; Zhao, X.; Gao, H.; Yuan, T.; Zhang, X. The effects of salt-loss soda residue and oxalate acid on property and structure of fly ash-based geopolymer. Constr. Build. Mater. 2023, 366, 130214. [Google Scholar] [CrossRef]
  33. Xiaoshuang, S.; Yanpeng, S.; Jinqian, L.; Yuhao, Z.; Ruihan, H. Preparation and performance optimization of fly ash- slag- red mud based geopolymer mortar: Simplex-centroid experimental design method. Constr. Build. Mater. 2024, 450, 138573. [Google Scholar] [CrossRef]
  34. Sun, B.; Ye, G.; de Schutter, G. A review: Reaction mechanism and strength of slag and fly ash-based alkali-activated materials. Constr. Build. Mater. 2022, 326, 126843. [Google Scholar] [CrossRef]
  35. Gao, X.; Yao, X.; Yang, T.; Zhou, S.; Wei, H.; Zhang, Z. Calcium carbide residue as auxiliary activator for one-part sodium carbonate-activated slag cements: Compressive strength, phase assemblage and environmental benefits. Constr. Build. Mater. 2021, 308, 125015. [Google Scholar] [CrossRef]
  36. Ye, N.; Yang, J.; Liang, S.; Hu, Y.; Hu, J.; Xiao, B.; Huang, Q. Synthesis and strength optimization of one-part geopolymer based on red mud. Constr. Build. Mater. 2016, 111, 317–325. [Google Scholar] [CrossRef]
  37. Zhao, X.; Wang, H.; Gao, H.; Liang, L.; Yang, J. Synthesis, Stability and Microstructure of a One-Step Mixed Geopolymer Backfill Paste Derived from Diverse Waste Slags. Sustainability 2023, 15, 6708. [Google Scholar] [CrossRef]
  38. Ren, S.; Li, L.; Zhao, X.; Wang, H.; Zhao, R. Unveiling the Potential of Civil Briquette Furnace Slag as a Silico-Aluminon Additive in Alkali-Activated Materials. Materials 2024, 17, 6188. [Google Scholar] [CrossRef]
  39. Li, Z.; Zhang, J.; Li, S.; Gao, Y.; Liu, C.; Qi, Y. Effect of different gypsums on the workability and mechanical properties of red mud-slag based grouting materials. J. Clean. Prod. 2020, 245, 118759. [Google Scholar] [CrossRef]
  40. Yao, X.L.; Wang, W.L.; Liu, M.; Yao, Y.G.; Wu, S. Synergistic use of industrial solid waste mixtures to prepare ready-to-use lightweight porous concrete. J. Clean. Prod. 2019, 211, 1034–1043. [Google Scholar] [CrossRef]
  41. Zhang, M.; He, M.; Zhang, J. Mitigation of efflorescence for multi-componential geopolymer: Influence of steel slag, flue gas desulfurization gypsum and pre-curing periods. J. Clean. Prod. 2023, 403, 136835. [Google Scholar] [CrossRef]
  42. JC/T 603-2004; Standard Test Method for Drying Shinkage of Mortar. Technical Supervision & Research Center for China Building Materials Industry: Beijing, China, 2004. Available online: https://www.cssn.net.cn/app/home/productDetail/a8105c02d10d9a7a92a9fef608f6879d (accessed on 18 June 2024). (In Chinese)
  43. Li, L.; Zhao, X.; Wang, H.; Cao, J.; Zhao, X.E. Properties characterization and microstructural analysis of alkali-activated solid waste-based materials with sawdust and wastewater integration. PLoS ONE 2025, 20, e0313413. [Google Scholar] [CrossRef] [PubMed]
  44. GB/T 2419-2005; Test Method for Fluidity of Cement Mortar. China Building Materials Federation: Beijing, China, 2005. Available online: https://www.cssn.net.cn/cssn/front/6824280.html (accessed on 18 June 2024). (In Chinese)
  45. Wang, H.; Zhao, X.; Gao, H.; Yuan, T.; Liu, X.; Zhang, W. Effects of alkali-treated plant wastewater on the properties and microstructures of alkali-activated composites. Ceram. Int. 2023, 49, 8583–8597. [Google Scholar] [CrossRef]
  46. GB/T 17671-2021; Method of Testing Cements—Determination of Strength (Idt ISO 679: 2021). China Building Materials Federation: Beijing, China, 2021. Available online: https://www.cssn.net.cn/cssn/front/4311243.html (accessed on 18 June 2024). (In Chinese)
  47. Fu-Quan, C.; Cui-Lan, C.; Ben-Shan, Z. A Novel Method for Calculating Starch Crystallinity. Food Sci. 2011, 32, 68–81. [Google Scholar]
  48. Zhang, Y.L.; Liu, X.M.; Xu, Y.T.; Tang, B.W.; Wang, Y.G.; Mukiza, E. Synergic effects of electrolytic manganese residue-red mud-carbide slag on the road base strength and durability properties. Constr. Build. Mater. 2019, 220, 364–374. [Google Scholar] [CrossRef]
  49. Riley, A.L.; Mayes, W.M. Long-term evolution of highly alkaline steel slag drainage waters. Environ. Monit. Assess. 2015, 187, 463. [Google Scholar] [CrossRef]
  50. Wang, S.; Pan, H.M.; Xiao, C.; Zhao, Q.X.; Wang, J.X. Preparation and mix proportion optimization of red mud-fly ash-based cementitious material synergistic activated by carbide slag and MSWIFA. Constr. Build. Mater. 2024, 415, 135032. [Google Scholar] [CrossRef]
  51. Thomas, J.J.; Ghazizadeh, S.; Masoero, E. Kinetic mechanisms and activation energies for hydration of standard and highly reactive forms of β-dicalcium silicate (C2S). Cem. Concr. Res. 2017, 100, 322–328. [Google Scholar] [CrossRef]
  52. Huang, D.W.; Yuan, Q.M.; Chen, P.; Tian, X.; Peng, H. Effect of activator properties on drying shrinkage of alkali-activated fly ash and slag. J. Build. Eng. 2022, 62, 105341. [Google Scholar] [CrossRef]
  53. Zhang, B.; Zhu, H.; Cheng, Y.Z.; Huseien, G.F.; Shah, K.W. Shrinkage mechanisms and shrinkage-mitigating strategies of alkali-activated slag composites: A critical review. Constr. Build. Mater. 2022, 318, 125993. [Google Scholar] [CrossRef]
  54. Mo, L.W.; Yang, S.; Huang, B.; Xu, L.L.; Feng, S.F.; Deng, M. Preparation, microstructure and property of carbonated artificial steel slag aggregate used in concrete. Cem. Concr. Comp. 2020, 113, 103715. [Google Scholar] [CrossRef]
  55. Li, M.H.; Lu, Y.J.; Liu, Y.J.; Chu, J.J.; Zhang, T.S.; Wang, W. Influence of the Steel Slag Particle Size on the Mechanical Properties and Microstructure of Concrete. Sustainability 2024, 16, 2083. [Google Scholar] [CrossRef]
  56. Lu, J.; Shen, Y.; Wang, Y.; Zhang, H.; Guan, X.; Zhu, J.; Liu, S. In-situ wet carbonation activation of red mud waste for sustainable grout materials. J. Ind. Eng. Chem. 2024, 136, 453–464. [Google Scholar] [CrossRef]
  57. Liu, S.; Shen, Y.; Wang, Y.; Shen, P.; Xuan, D.; Guan, X.; Shi, C. Upcycling sintering red mud waste for novel superfine composite mineral admixture and CO2 sequestration. Cem. Concr. Compos. 2022, 129, 104497. [Google Scholar] [CrossRef]
  58. Li, Y.C.; Min, X.B.; Ke, Y.; Liu, D.G.; Tang, C.J. Preparation of red mud-based geopolymer materials from MSWI fly ash and red mud by mechanical activation. Waste Manag. 2019, 83, 202–208. [Google Scholar] [CrossRef]
  59. Wang, Q.P.; Liao, Z.Y.; Yao, D.X.; Yang, Z.J.; Wu, Y.H.; Tang, C.L. Phosphorus immobilization in water and sediment using iron-based materials: A review. Sci. Total Environ. 2021, 767, 144246. [Google Scholar] [CrossRef]
  60. Siauciunas, R.; Hilbig, H.; Prichockiene, E.; Smigelskyte, A.; Takulinskas, Z. Accelerated carbonation of C2SH based dense concrete. Ceram. Int. 2020, 46, 29436–29442. [Google Scholar] [CrossRef]
  61. Zhang, D.; Shao, Y.X. Effect of early carbonation curing on chloride penetration and weathering carbonation in concrete. Constr. Build. Mater. 2016, 123, 516–526. [Google Scholar] [CrossRef]
  62. Li, W.Z.; Cao, M.L.; Liu, F.Y.; Wang, D.; Chang, J. Pretreatment of alkali activation and carbonation of steel slag for using as binding material. Cem. Concr. Comp. 2024, 149, 105521. [Google Scholar] [CrossRef]
  63. Duque-Redondo, E.; Yamada, K.; Manzano, H. Effect of Chloride and Sulfate in the Immobilization of Cs-137 in C-S-H Gel. J. Adv. Concr. Technol. 2021, 19, 95–105. [Google Scholar] [CrossRef]
  64. Yusuf, M.O. Bond Characterization in Cementitious Material Binders Using Fourier-Transform Infrared Spectroscopy. Appl. Sci. 2023, 13, 3353. [Google Scholar] [CrossRef]
  65. Feng, H.; Wen, J.X.; Shao, Q.; Yang, Y.Y.; Yao, X.P. Carbonation resistance of fly ash/slag based engineering geopolymer composites. Constr. Build. Mater. 2024, 449, 138471. [Google Scholar] [CrossRef]
  66. Jhang, J.H.; Boscoboinik, J.A.; Altman, E.I. Ambient pressure x-ray photoelectron spectroscopy study of water formation and adsorption under two-dimensional silica and aluminosilicate layers on Pd(111). J. Chem. Phys. 2020, 152, 084705. [Google Scholar] [CrossRef] [PubMed]
  67. Efimov, A.M.; Pogareva, V.G.; Shashkin, A.V. Water-related bands in the IR absorption spectra of silicate glasses. J. Non-Cryst. Solids 2003, 332, 93–114. [Google Scholar] [CrossRef]
  68. Puligilla, S.; Mondal, P. Co-existence of aluminosilicate and calcium silicate gel characterized through selective dissolution and FTIR spectral subtraction. Cem. Concr. Res. 2015, 70, 39–49. [Google Scholar] [CrossRef]
  69. Bossard, C.; Granel, H.; Jallot, É.; Montouillout, V.; Fayon, F.; Soulié, J.; Drouet, C.; Wittrant, Y.; Lao, J. Mechanism of Calcium Incorporation Inside Sol-Gel Silicate Bioactive Glass and the Advantage of Using Ca(OH)2 over Other Calcium Sources. ACS Biomater. Sci. Eng. 2019, 5, 5906–5915. [Google Scholar] [CrossRef]
  70. Wang, H.; Gillott, J.E. Mechanism of Alkali-Silica Reaction and the Significance of Calcium Hydroxide. Cem. Concr. Res. 1991, 21, 647–654. [Google Scholar] [CrossRef]
  71. Glasser, L.S.D.; Kataoka, N. On the Role of Calcium in the Alkali-Aggregate Reaction. Cem. Concr. Res. 1982, 12, 321–331. [Google Scholar] [CrossRef]
  72. Amirhossein, M.; Wei, J.Q. Characterization of Calcium Silicate Hydrate Gels with Different Calcium to Silica Ratios and Polymer Modifications. Gels 2022, 8, 75. [Google Scholar] [CrossRef]
  73. Duan, S.Y.; Liao, H.Q.; Cheng, F.Q.; Song, H.P.; Yang, H.Q. Investigation into the synergistic effects in hydrated gelling systems containing fly ash, desulfurization gypsum and steel slag. Constr. Build. Mater. 2018, 187, 1113–1120. [Google Scholar] [CrossRef]
  74. Monteagudo, S.M.; Moragues, A.; Gávez, J.C.; Casati, M.J.; Reyes, E. The degree of hydration assessment of blended cement pastes by differential thermal and thermogravimetric analysis. Morphological evolution of the solid phases. Thermochim. Acta 2014, 592, 37–51. [Google Scholar] [CrossRef]
  75. Maitra, S.; Bose, S.; Bandyopadhyay, N.; Roychoudhury, A. Dehydration kinetics of calcium aluminate cement hydrate under non-isothermal conditions. Ceram. Int. 2005, 31, 371–374. [Google Scholar] [CrossRef]
  76. Vaiciukyniene, D.; Nizeviciene, D.; Kiele, A.; Janavicius, E.; Pupeikis, D. Effect of phosphogypsum on the stability upon firing treatment of alkali-activated slag. Constr. Build. Mater. 2018, 184, 485–491. [Google Scholar] [CrossRef]
  77. van Riessen, A.; Jamieson, E.; Kealley, C.S.; Hart, R.D.; Williams, R.P. Bayer-geopolymers: An exploration of synergy between the alumina and geopolymer industries. Cem. Concr. Comp. 2013, 41, 29–33. [Google Scholar] [CrossRef]
  78. Li, M.G.; Tan, H.B.; Zhang, J.J.; Deng, X.F.; Kong, X.H.; Chen, P.; Jian, S.W.; He, X.Y.; Yang, J. Enhancement in compressive strength of carbide slag activated ground granulated blast furnace slag by introducing CaCl2 and NaCl. Constr. Build. Mater. 2023, 385, 131071. [Google Scholar] [CrossRef]
  79. Nath, P.; Sarker, P.K. Effect of GGBFS on setting, workability and early strength properties of fly ash geopolymer concrete cured in ambient condition. Constr. Build. Mater. 2014, 66, 163–171. [Google Scholar] [CrossRef]
  80. Neupane, K. Fly ash and GGBFS based powder-activated geopolymer binders: A viable sustainable alternative of portland cement in concrete industry. Mech. Mater. 2016, 103, 110–122. [Google Scholar] [CrossRef]
  81. Guo, W.C.; Zhang, Z.Y.; Bai, Y.Y.; Zhao, G.Q.; Sang, Z.H.; Zhao, Q.X. Development and characterization of a new multi-strength level binder system using soda residue-carbide slag as composite activator. Constr. Build. Mater. 2021, 291, 123367. [Google Scholar] [CrossRef]
  82. Jiang, H.S.; Ke, G.J.; Li, Z.Y. Synergistic activation mechanism and long-term properties of a solid waste cementitious materials based on red mud and calcium carbide slag. Constr. Build. Mater. 2024, 438, 137313. [Google Scholar] [CrossRef]
  83. Ren, Q.S.; Qi, W.Y.; Zhao, Q.X.; Jia, Y.L.; Feng, Y.B.; Han, Y.J.; Duan, G.; Pang, H.T. Preparation and Characterization of Low-Carbon Cementitious Materials Based on Soda-Residue-Activated Ground Granulated Blast-Furnace Slag: A Case Study on Cemented Paste Backfills. Metals 2023, 13, 694. [Google Scholar] [CrossRef]
  84. Zhao, X.; Wang, H.; Wang, X.; Zhao, X.-e. Sustainable application of waste eggshell as fillers in alkali-activated solid waste-based materials: Varying treated methods and particle sizes. Constr. Build. Mater. 2024, 425, 136040. [Google Scholar] [CrossRef]
  85. Li, Q.; Li, J.J.; Zhang, S.Q.; Huang, X.Y.; Wang, X.; Wang, Y.; Ni, W. Research Progress of Low-Carbon Cementitious Materials Based on Synergistic Industrial Wastes. Energies 2023, 16, 2376. [Google Scholar] [CrossRef]
  86. Chen, P.; Ma, B.; Tan, H.; Wu, L.; Zheng, Z.; He, X.; Li, H.; Jin, Z.; Li, M.; Lv, Z. Improving the mechanical property and water resistance of β-hemihydrate phosphogypsum by incorporating ground blast-furnace slag and steel slag. Constr. Build. Mater. 2022, 344, 128265. [Google Scholar] [CrossRef]
  87. Wang, Q.; Wang, Y.; Gu, X.W.; Liu, J.P.; Xu, X.C. Study on the Properties and Hydration Mechanism of Calcium Carbide Residue-Based Low-Carbon Cementitious Materials. Buildings 2024, 14, 1259. [Google Scholar] [CrossRef]
  88. Feng, Y.B.; Li, F.; Qi, W.Y.; Ren, Q.S.; Qi, W.Y.; Duan, G.; Zheng, K.L.; Han, Y.J.; Pang, H.T. Mechanical Properties and Microstructure of Iron Tailings Cemented Paste Backfills Using Carbide Slag-Activated Ground Granulated Blast-Furnace Slag as Alternative Binder. Minerals 2022, 12, 1549. [Google Scholar] [CrossRef]
  89. Cong, P.L.; Mei, L.N. Using silica fume for improvement of fly ash/slag based geopolymer activated with calcium carbide residue and gypsum. Constr. Build. Mater. 2021, 275, 122171. [Google Scholar] [CrossRef]
  90. Wang, Q.; Zhang, R.B.; Guo, J.W.; Cai, G.J.; Li, Y.F. Study on mechanical properties and microstructure of metakaolin-slag-calcium carbide residue synergistic solidifying waste engineering mud. Constr. Build. Mater. 2024, 438, 137135. [Google Scholar] [CrossRef]
  91. Zhang, Q.; Wu, Y.; Luo, J.Y.; Cao, J.S.; Kang, C.J.; Wang, S.N.; Li, K.Y.; Zhao, J.N.; Aleem, M.; Wang, D.B. Enhanced volatile fatty acids production from waste activated sludge with synchronous phosphorus fixation and pathogens inactivation by calcium hypochlorite stimulation. Sci. Total Environ. 2020, 712, 136500. [Google Scholar] [CrossRef]
  92. Yin, W.Z.; Yang, B.; Fu, Y.F.; Chu, F.D.; Yao, J.; Cao, S.H.; Zhu, Z.L. Effect of calcium hypochlorite on flotation separation of covellite and pyrite. Powder Technol. 2019, 343, 578–585. [Google Scholar] [CrossRef]
  93. Kim, W.; Saito, F. Sonochemical synthesis of hydroxyapatite from H3PO4 solution with Ca(OH)2. Ultrason. Sonochem. 2001, 8, 85–88. [Google Scholar] [CrossRef]
  94. Dou, W.X.; Zhou, Z.; Jiang, L.M.; Jiang, A.J.; Huang, R.W.; Tian, X.C.; Zhang, W.; Chen, D.Q. Sulfate removal from wastewater using ettringite precipitation: Magnesium ion inhibition and process optimization. J. Environ. Manag. 2017, 196, 518–526. [Google Scholar] [CrossRef]
  95. Sun, Q.; Lin, J.; Cao, J.X.; Li, C.; Shi, D.; Gao, M.R.; Wang, Y.; Zhang, C.S.; Ding, S.M. A new method to overall immobilization of phosphorus in sediments through combined application of capping and oxidizing agents. Sci. Total Environ. 2019, 694, 133770. [Google Scholar] [CrossRef]
  96. Fang, D.X.; Huang, L.P.; Fang, Z.Y.; Zhang, Q.; Shen, Q.S.; Li, Y.M.; Xu, X.Y.; Ji, F.Y. Evaluation of porous calcium silicate hydrate derived from carbide slag for removing phosphate from wastewater. Chem. Eng. J. 2018, 354, 1–11. [Google Scholar] [CrossRef]
Buildings 15 01426 g001
Figure 1. SEM images of by-products: (a) fly ash, (b) red mud, (c) carbide slag, and (d) steel slag.
Figure 1. SEM images of by-products: (a) fly ash, (b) red mud, (c) carbide slag, and (d) steel slag.
Buildings 15 01426 g001
Buildings 15 01426 g002
Figure 2. Schematic diagram for sample synthesis and characterization of all-solid-waste materials.
Figure 2. Schematic diagram for sample synthesis and characterization of all-solid-waste materials.
Buildings 15 01426 g002
Buildings 15 01426 g003
Figure 3. (a) Electrical conductivity, (b) pH value, and (c) fluidity of fresh mixtures with all-solid wastes.
Figure 3. (a) Electrical conductivity, (b) pH value, and (c) fluidity of fresh mixtures with all-solid wastes.
Buildings 15 01426 g003
Buildings 15 01426 g004
Figure 4. Curing in water for hardened all-solid-waste samples.
Figure 4. Curing in water for hardened all-solid-waste samples.
Buildings 15 01426 g004
Buildings 15 01426 g005aBuildings 15 01426 g005b
Figure 5. (a) Compressive strengths, (b) densities, and (c) failure modes of hardened samples with full wastes.
Figure 5. (a) Compressive strengths, (b) densities, and (c) failure modes of hardened samples with full wastes.
Buildings 15 01426 g005aBuildings 15 01426 g005b
Buildings 15 01426 g006
Figure 6. Drying shrinkage vs. curing age of all-solid-waste mortar samples.
Figure 6. Drying shrinkage vs. curing age of all-solid-waste mortar samples.
Buildings 15 01426 g006
Buildings 15 01426 g007aBuildings 15 01426 g007b
Figure 7. SEM images of all-solid-waste samples: (a) P1 and P2, (b) P3, (c) P4, and (d) P5.
Figure 7. SEM images of all-solid-waste samples: (a) P1 and P2, (b) P3, (c) P4, and (d) P5.
Buildings 15 01426 g007aBuildings 15 01426 g007b
Buildings 15 01426 g008aBuildings 15 01426 g008b
Figure 8. EDS spectra and elemental compositions via mapping technique of all-solid-waste samples: (a) P3, (b) P4, and (c) P5. The colors in the images should be referenced to the online published version.
Figure 8. EDS spectra and elemental compositions via mapping technique of all-solid-waste samples: (a) P3, (b) P4, and (c) P5. The colors in the images should be referenced to the online published version.
Buildings 15 01426 g008aBuildings 15 01426 g008b
Buildings 15 01426 g009
Figure 9. XRD patterns of (a) all-solid-waste samples and (b) raw materials.
Figure 9. XRD patterns of (a) all-solid-waste samples and (b) raw materials.
Buildings 15 01426 g009
Buildings 15 01426 g010
Figure 10. FTIR spectra of (a) all-solid-waste samples and (b) raw materials.
Figure 10. FTIR spectra of (a) all-solid-waste samples and (b) raw materials.
Buildings 15 01426 g010
Buildings 15 01426 g011aBuildings 15 01426 g011b
Figure 11. TG, DTG, and DSC curves of all-solid-waste samples: (a) P3, (b) P4, and (c) P5.
Figure 11. TG, DTG, and DSC curves of all-solid-waste samples: (a) P3, (b) P4, and (c) P5.
Buildings 15 01426 g011aBuildings 15 01426 g011b
Table 1. Chemical compositions and physical indexes of by-products.
Table 1. Chemical compositions and physical indexes of by-products.
IndexParametersFly Ash
(FA)		Red Mud
(RM)		Carbide Slag
(CS)		Steel Slag
(SS)
Chemical
(mass%)		SiO245.1027.502.7216.00
Al2O325.3228.402.285.68
CaO5.322.5078.8643.60
MgO1.600.200.0010.20
Fe2O39.5025.801.0216.50
K2O0.000.100.050.37
Na2O0.0014.700.000.24
Others13.160.8015.077.41
PhysicalSpecific gravity (−)2.452.561.802.01
Specific surface area (m2/kg)640360420445
Note: ‘Others’ notes TiO2, SO3, etc.
Table 2. The pH and electrical conductivity of raw materials (temperature 25 °C and humidity 80%).
Table 2. The pH and electrical conductivity of raw materials (temperature 25 °C and humidity 80%).
RolesSolid
Substances		Solid Mass
(g)		Water Mass
(g)		Electrical
Conductivity
(mS/cm)		pH Value
(-)
Water——160.01.299.03
By-productsFly ash80.0160.01.689.89
Red mud80.0160.03.059.56
Carbide slag80.0160.03.5212.22
Steel slag80.0160.02.9712.13
AdditivesCa3(PO4)22.0160.01.288.71
Ca(ClO)22.0160.06.5311.32
Table 3. Chemical components of additives—calcium hypochlorite and tricalcium phosphate.
Table 3. Chemical components of additives—calcium hypochlorite and tricalcium phosphate.
Name of AdditivesCalcium HypochloriteTricalcium Phosphate
Chemical formulaCa(ClO)2Ca3(PO4)2
Molecular mass (g/mol)142.920310.000
Effective chlorine Cl≥35.000%—
Effective content—≥34.000%
Hydrochloric acid insoluble≤0.050%≤0.040%
Ammonia precipitate≤0.200%—
Nitrate (NO3)—≤0.200%
Arsenic (As)—≤0.002%
Sulphate (SO4)≤0.100%≤0.020%
Iron (Fe)≤0.005%≤0.010%
Heavy metals (as Pb)≤0.002%≤0.002%
Magnesium and metal salts≤0.500%—
Moisture content—≤1.000%
Table 4. Designed mixing proportions of all-solid-waste materials based on industrial wastes.
Table 4. Designed mixing proportions of all-solid-waste materials based on industrial wastes.
No.SampleBy-Products (g)Additives (g)
with a 1:1 Mass Blend		Tap
Water
(g)		River
Sand
(g)
Fly
Ash		Red
Mud		Carbide
Slag		Steel
Slag		Ca3(PO4)2Ca(ClO)2
P1FA-CA400———55182—
P2FA-RM-CA200200——55182—
P3FA-RM-CS-CA200100100—55182—
P4FA-RM-CS-SS-CA10010010010055182—
P5FA-RM-CS-SS-0010010010010000182—
DP1FA-CA400———55200800
DP2FA-RM-CA200200——55200800
DP3FA-RM-CS-CA200100100—55200800
DP4FA-RM-CS-SS-CA10010010010055200800
DP5FA-RM-CS-SS-0010010010010000200800
Note: The by-products include fly ash (FA), red mud (RM), carbide slag (CS), and steel slag (SS). The additives include calcium hypochlorite (Ca(ClO)2) and tricalcium phosphate (Ca3(PO4)2). The amounts of by-products and additives are given in grams (g).
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

Jiang, L.; Zhao, X.; Wang, H. Synthesis and Property Characterization of Low-Activity Waste-Derived Quaternary Cementitious Materials. Buildings 2025, 15, 1426. https://doi.org/10.3390/buildings15091426

AMA Style

Jiang L, Zhao X, Wang H. Synthesis and Property Characterization of Low-Activity Waste-Derived Quaternary Cementitious Materials. Buildings. 2025; 15(9):1426. https://doi.org/10.3390/buildings15091426

Chicago/Turabian Style

Jiang, Linlin, Xianhui Zhao, and Haoyu Wang. 2025. "Synthesis and Property Characterization of Low-Activity Waste-Derived Quaternary Cementitious Materials" Buildings 15, no. 9: 1426. https://doi.org/10.3390/buildings15091426

APA Style

Jiang, L., Zhao, X., & Wang, H. (2025). Synthesis and Property Characterization of Low-Activity Waste-Derived Quaternary Cementitious Materials. Buildings, 15(9), 1426. https://doi.org/10.3390/buildings15091426

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