Calcium Carbide Residue as a Supplementary Precursor is Geopolymer Binders

With the declining availability of conventional supplementary cementitious materials such as fly ash and slag, there is an urgent need to identify alternative aluminosilicate sources for geopolymer synthesis. Calcium carbide residue (CCR), a high-calcium industrial by-product from acetylene production, has shown potential as a sustainable precursor, yet its role in slag-based geopolymer systems remains insufficiently explored. The aim of this work is to evaluate the chemical reactivity, mechanical performance, and microstructural characteristics of slag-based geopolymers incorporating CCR, with and without metakaolin (MK). Mechanical properties were assessed through setting-time measurements and compressive strength testing, while microstructural evolution was examined using standard microstructural and thermal characterization techniques such as XRD, FTIR, TGA and SEM. The incorporation of CCR in the geopolymer mixes influenced setting behavior and strength development over time, with lower CCR content delaying setting by about 13%, while higher dosage or ternary blends with MK accelerated setting behaviour by up to 10% due to synergistic reactivity. Compressive strength results confirmed that the binary mix with lower CCR dosage and the ternary blends containing MK achieved strengths comparable to the control mix, with the ternary blends reaching approximately 96%–99% of the control strength. This highlights their potential as alternative precursors without compromising mechanical performance. Microstructural analyses revealed that CCR alters the gel morphology and phase composition, resulting in a hybrid C–A–S–H and N–A–S–H gel system with a refined pore structure and potentially denser microstructure Furthermore, the ternary combination of slag, CCR, and MK enhances the Si/Al and Ca/Si ratios, facilitating improved polycondensation and the development of a more cohesive and interconnected gel matrix. These findings demonstrate the potential of CCR as a viable precursor in geopolymer systems, contributing to improved structural performance and sustainability by diverting an industrial waste from landfills and reducing reliance on conventional precursors such as slag.

1 Introduction

Ordinary Portland cement (OPC), the most widely used binding material in construction, serves as the key ingredient in concrete and mortar, providing strength and durability to structures (Sumesh et al., 2017; Amran et al., 2021a). However, the production of OPC is energy-intensive with 5%–9% of global anthropogenic carbon emission, contributing to environmental concerns (Amran et al., 2021a; Ahmad et al., 2024; Nikolakopoulos et al., 2024; Mohamad et al., 2021; Mohammed et al., 2025). The growing sustainability and environmental concerns surrounding OPC and concrete have spurred innovative research on low-carbon cements and alternatives cementitious material, among which alkali activated cement or geopolymer cement (GPC) stands out as the most transformative approach and has undergone a resurgence of interest in recent years (Amran et al., 2021a; Zhang et al., 2018). Geopolymers, introduced by Davidovits in 1970, are aluminosilicate binders (M₂O⋅mAl₂O₃⋅nSiO₂, where M is an alkali metal) polymerized from aluminosilicate source materials – precursors such as fly ash (FA), ground granulated blast furnace slag (GGBFS), metakaolin (MK), and mine tailings, in the presence of alkaline solution – activators such as sodium hydroxide (SH) and sodium silicate (SS) (Davidovits, 1991; David and ovits, 1994). For instance, the mixture of alkali activator and GGBFS undergoes a polymerization–condensation reaction, resulting in the formation of calcium aluminate silicate hydrate (C–A–S–H) and sodium aluminate silicate hydrate (N–A–S–H) gels, along with various secondary reaction products such as layered double hydroxides (Vázquez-Rodríguez et al., 2023).

FA and GGBFS, by-products of the coal and steel industries respectively, are the most widely used precursors for geopolymerization, but their long-term availability is increasingly uncertain due to global industrial transitions (Ghafari et al., 2020; Amran et al., 2021b; Bayrak et al., 2023; Hanani Ismail et al., 2024). FA, the most widely used supplementary cementitious material (SCM) in North America, supplies have become inconsistent as coal-fired power plants adopt pollution-control technologies and shift toward Powder River Basin coal, affecting ash quantity and quality (Fořt et al., 2021; Sabet et al., 2013). Similarly, the global transition from traditional blast-furnace steelmaking to electric arc furnace technologies is reducing the production of reactive slag or eliminating it altogether (Bonfante et al., 2025; Hafez et al., 2021; Scrivener et al., 2018). This trend poses challenges for their continuous use as SCM in construction. Based on this concern, innovative low-carbon aluminosilicate source materials that present similar physicochemical and engineering properties along with cost-effectiveness with FA or GGBFS are urgently needed. However, despite this clear need for alternative precursors, the potential of calcium carbide residue (CCR), particularly in slag-based systems and in combination with MK, remain insufficiently established.

Horpibulsuk et al (2014) introduces CCR as a viable source as a precursor to produce GPC, either as only precursor or combined with other pozzolanic materials to create a cementing agent (Horpibulsuk et al., 2014). As shown in Equation 1, CCR is a by-product rich in calcium hydroxide (Ca(OH)₂), generated during acetylene (C₂H₂) production via the hydrolysis of calcium carbide (CaC₂). It is formed when limestone and coke are heated in an electric arc furnace to form CaC₂ and carbon monoxide (CO) gas. Its application in concrete has recently generated interest because of its potential to improve various properties of concrete while reducing environmental impact (Zhang et al., 2018; Horpibulsuk et al., 2014; Adufu et al., 2023).

${CaC}_2+{2H}_{2}O\to C_2{H}_2+{Ca\left(OH\right)}_2(1)$

Equation 1. Calcium Carbide Residue from acetylene.

Several studies have investigated the production of geopolymer concrete incorporating FA and CCR. For instance, by varying the replacement levels of FA with CCR (0%, 10%, 20%, and 30%) and adjusting the SS-to-SH ratios (1.0–2.5 by weight), researchers have evaluated the effects on setting time and compressive strength of the resulting mortars (Sun et al., 2022; Phoo-ngernkham et al., 2020; Hanjitsuwan et al., 2018; Arulrajah et al., 2016). Findings reveal that both CCR content and the SS-to-SH ratio significantly influence the mortar’s setting time, with higher ratios facilitating quicker setting due to enhanced geopolymerization, supported by increased calcium content from CCR. However, a threshold is identified where further increases in CCR beyond 20% reduce both compressive and bond strength, suggesting an optimal CCR replacement level for achieving the best material performance. Hanjitsuwan et al. (2018), also investigated a similar combination of CCR and FA in alkali-activated mortar. The results showed that increasing CCR significantly reduced setting time, offering benefits for projects requiring quick setting, and enhanced strength development due to the additional formation of C–S–H and N–A–S–H gels. Moreover, mortars with CCR exhibited improved resistance to acid and sulfate attack, highlighting the potential CCR as a sustainable additive in geopolymer binders (Hanjitsuwan et al., 2018). In addition, Phummiphan et al. (2017) also confirmed that the partial replacement with CCR is also highly influenced and dependent on the SS/SH. The optimal CCR replacement ratio for maximizing the 90-day unconfined compressive strength (UCS) of lateritic soil-FA geopolymer was found to be 20% across all tested SS/SH ratios, highlighting that the effectiveness of CCR activation is highly dependent on the activator ratio (Phummiphan et al., 2017). Recent study by Zhu et al. (2025) demonstrated that CCR, owing to its high calcium content, contributed to the formation of C–S–H and N–A–S–H gels and could partially replace conventional alkali activators (Zhu et al., 2025).

Studies indicate that CCR, particularly when combined with 5% GGBFS, significantly enhances the compressive strength and stiffness of the stabilized C&D aggregates, making it a viable option for pavement applications and offering a cost-effective alternative to traditional materials (Arulrajah et al., 2016). However, these studies highlight limitations, including uncertainty about the long-term durability and performance of geopolymer-stabilized materials in real-world conditions, as well as variability in the composition of industrial CCRs, pointing to critical areas for future research.

Moreover, given the anticipated limitations in the future availability of FA and GGBFS, MK is also emerging as a promising alternative and is increasingly being combined with CCR as a precursor in geopolymer synthesis. Adufu et al. (2023) evaluates the impact of CCR on the physical and mechanical characteristics of MK-based GPC (Adufu et al., 2023). The study highlighted the importance of CCR ratio and curing temperatures in developing MK-based GPCs achieving optimum setting time and workability. Specifically, they found that CCR significantly increases the setting time and reduces workability due to its high alkalinity and lower density compared to MK. In addition, curing at 30 °C significantly enhances early-age strength development and helped address the negative effect of excessive alkalinity introduced by CCR, particularly in mix containing 15% CCR.

While CCR has been studied as a precursor in geopolymer systems (Adufu et al., 2023; Obeng et al., 2024; Obeng et al., 2023), existing research has primarily focused on its use in pavement applications and geotechnical soil stabilization (Phoo-ngernkham et al., 2020; Arulrajah et al., 2016; Phummiphan et al., 2017). As such and to the best of our knowledge no research has investigated the influence of CCR as a supplementary precursor in slag-based GPC. Additionally, the combined synergistic effect of CCR with MK in varying proportions on early-age and long-term compressive strength and microstructural properties remains insufficiently explored. This presents a critical gap, particularly considering the potential for synergistic interactions between CCR (a Ca-rich material), GGBFS, and MK, which may influence the formation of N–A–S–H and C–(A)–S–H gels. Understanding these interactions is essential for optimizing setting time, strength development, and microstructural performance. Addressing this knowledge gap will support the development of sustainable, hybrid GPC systems using underutilized industrial by-products.

This research aims to evaluate the performance of GPC mortars incorporating partial replacement of GGBFS with CCR and MK in slag-based GPC systems. The study explores binary and ternary precursor combinations to elucidate the reaction mechanisms and the formation of N–A–S–H and C–(A)–S–H gels. A factorial experimental design was employed to investigate the influence of CCR and MK replacement levels (10%, 15%, and 20%) on slag-based GPC. Additionally, the effects of the alkaline-to-binder (A/B) ratio and precursor fineness were examined to optimize mix performance. The fresh and hardened properties of the developed mortars were evaluated, alongside detailed microstructural characterization. This work contributes to the advancement of hybrid GPC formulations utilizing CCR and MK as sustainable precursors, promoting the development of eco-friendly mortars. The resulting hybrid GPC mortars show potential for applications in internal and external wall coatings, as well as in the repair of deteriorated surfaces. The outcomes of this study will advance low-carbon alternative materials and promote sustainable construction practices through the effective utilization of industrial by-products that are typically destined for landfills.

2 Materials and methods

2.1 Materials

The CCR, slag and MK, are serving as the main precursors for the GPC. Slag was collected from Argos, Tampa Plant and the MK was obtained from Fishstone concrete with their chemical composition consistent with ASTM 618. While CCR, acquired from carbide industries LLC and GNR imports exports, was first thermally processed to synthesize greater amount of Ca content. This was carried out by initially drying CCR at room temperature for 24 h, followed by oven-drying at 110 °C for 2 h. The dried materials were then pulverized and subsequently screened using a sieve with an aperture size of less than 150 µm to obtain a uniform fine powder as shown in Figure 1. The chemical composition of CCR, along with the acquired slag and MK, as determined by X-ray fluorescence (XRF, Bruker M4 Tornado), is shown in Figure 2. The major oxides composition of slag is 56.61% CaO, 25.35% SiO₂, 8.31% Al₂O₃ conforming with ASTM C989/C989M-24 (ASTM C989/C989M, 2024), while CCR is composed predominantly of CaO (96.43%). In contrast, MK contains 52.51% SiO₂, 40.83% Al₂O₃ and 2.58% Fe₂O₃, yielding a combined content of over 95%, which satisfies the ASTM C618 requirement for Class F pozzolans (ASTM C618, 2023). In this study, commercial-grade sodium hydroxide (SH) and sodium silicate (SS) were used as alkali activators for synthesizing the GPC. Both chemicals were sourced from Sigma Aldrich. The SH, supplied in pellets form, had a purity of 97%, while the SS solution contained 14.7% Na₂O, 29.4% SiO₂, and 55.9% water by weight.

Figure 1

Figure 1. The purification and synthesis process of CCR aimed at enhancing its Ca content involved initial drying at room temperature, followed by oven drying at 110 °C. The dried material was then pulverized using a ball mill and sieved through a <150 µm mesh to obtain a fine, uniform powder.

Figure 2

Figure 2. XRF’s Chemical composition of Slag, CCR and MK. Slag and CCR particles demonstrate high calcium content, while MK contains a combined total of SiO₂, Al₂O₃ and Fe₂O₃ exceeding 70%, indicating its high pozzolanic reactivity.

The X-ray diffraction (XRD) pattern depicting the crystalline phases and peaks of each material are shown in Figure 3A. It shows that slag is predominantly amorphous, with minor crystalline phases like gypsum and calcite. CCR is highly crystalline, dominated by portlandite and calcite with sharp, intense peaks. MK contains both crystalline (quartz, kaolinite) and amorphous phases, indicated by a broad hump in the pattern. The scanning electron microscopy (SEM) micrographs of the materials are shown in Figures 3B–D. Slag exhibits large, angular, and smooth particles, indicative of a dense, glassy, and mostly amorphous structure. In contrast, CCR displays a more heterogeneous and irregular morphology, with rough, fragmented particles suggesting a highly crystalline composition. MK shows a highly porous, fluffy, and agglomerated structure composed of fine, irregular particles.

Figure 3

Figure 3. (A) XRD patterns showing the crystalline phases of Slag, CCR, and MK. (B) SEM micrograph of Slag, (C) SEM micrograph of CCR, and (D) SEM micrograph of MK. The SEM micrographs show that all materials have irregularly shaped particles, with MK exhibiting the finest particles, CCR containing the largest and coarsest particles, and Slag displaying a smooth, glassy morphology indicative of its amorphous nature.

2.2 Experimental design

The binary and ternary mixes of slag, CCR, and MK were structured using a maximum of 20% CCR substitution, which is below the 30% threshold beyond which compressive strength was observed to decline significantly; therefore, 20% was chosen as a safe upper limit to avoid performance losses (Phoo-ngernkham et al., 2020; Hanjitsuwan et al., 2018; Hanjitsuwan et al., 2017). A mix of SS and SH solution were used as alkaline activator for the preparation of the mixes (Rattanasak et al., 2009; Mahamat Ahmat et al., 2023). 10 M SH solution was prepared 24 h prior and allowed to cool before mixing with SS. The activator-to-binder (A/B) ratio was set at 0.4, based on previous studies that identified this proportion as optimal for effective geopolymer synthesis (Ghafoor et al., 2021; Ketana et al., 2021). Likewise, SS/SH ratio of 2.5 was used, in alignment with values reported in previous studies to enhance geopolymerization (Ghafoor and Fujiyama, 2023; Arafa et al., 2018; Deb et al., 2014; Kina et al., 2025), while 1.6 was used as the sand-to-binder ratio (S/B) (Hanjitsuwan et al., 2018; Hanjitsuwan et al., 2017). To prepare the GPC, the binders were measured and mixed thoroughly together for 5 min before mixing the mixture with sand for another 5 min. The prepared alkaline activator was then added to the dry mixture and mixed for three to 4 min. The fresh mix is then cast into molds of size 2in × 2in × 2in and then all the filled-in molds were covered with a thin polyethylene film to prevent the evaporation of water. The samples were demolded after 1 day and were cured in a controlled chamber at room temperature as proposed for optimum geopolymerization and in previous studies and more suitable for in situ application (Somna et al., 2011). Replicate samples were prepared to ensure statistical reliability and consistency. Additionally, a 3 in. × 6 in. cylindrical specimen was cast for validation purposes. Detail of the mix design is shown in Table 1 and experimental process is shown in Figure 4.

Table 1

Table 1. Mix proportion (by weight).

Figure 4

Figure 4. Sample preparation and testing procedure of GPC sample with slag, CCR and MK. The figure depicts the sequential process of geopolymer production, encompassing material mixing, casting, and curing. It also outlines the characterization methods used to assess the mechanical performance and microstructural properties of the hardened specimens.

2.3 Test methods and microstructural analyses

After preparing the samples, the initial and final setting time were determined in accordance with ASTM C807 using modified Vicat apparatus (ASTM C807, 2021). The compressive strength of the cube and cylindrical samples at various curing ages (1, 7 and 28 days) were tested using Automatic compression machine (Humboldt HCM-300iHAC) in accordance with ASTM C109 (ASTM C109, 2024) and ASTM C39 (ASTM C39, 2024) respectively. Specimens were preloaded at 75 psi/sec and loaded at 35 psi/sec, with an approach rate set to 15% of the machine’s maximum load capacity. The test automatically terminated upon a 10% drop from the peak load, indicating specimen failure. M1, M3 and M4 were selected for microstructural analysis using integration of characterization techniques, including XRD, FTIR, TGA and SEM. The selection of these mixes was based on M1 serving as the control mix, M3 representing the binary mix containing the highest CCR content, and M4 serving as representative ternary blend incorporating both CCR and MK. This selection allowed for a comprehensive assessment of how different precursor combinations influence phase composition, gel formation, and the overall microstructural development of the geopolymer matrix. Crystalline phases were identified using XRD (Rigaku Miniflex Powder XRD), performed at scan range from 10° to 70° 2θ, at a scan speed of 10.00°/min and a fine step width of 0.01°. FTIR (Nicolet 6700) was used to analyze functional groups and investigate chemical bonding in the samples, scanning in the wavenumber region of 400–4,000 cm^-1. Thermal stability and decomposition behaviour were examined with TGA (Mettler Toledo TGA2), with approximately 5 mg of powdered sample placed in alumina crucibles. The analysis was conducted under a nitrogen atmosphere, with the temperature ramping from room temperature to 1,000 °C at a constant heating rate of 20 °C/min. Morphological characteristics of the sample fragments were observed using SEM-EDS (Thermo Axia Variable Pressure SEM). SEM samples were prepared from broken pieces of the hardened paste samples, impregnated with epoxy to preserve their structural integrity, followed by a systematic grinding and polishing process using various grits of silicon carbide paper. This preparation was carried out with a combined Struers Rotopol-15 and Struers Rotoforce-1 system to achieve a smooth and suitable surface for high-resolution imaging before SEM examination. For XRD, FTIR, and TGA analyses, powdered forms of the samples were used to ensure uniformity and accurate characterization.

3 Results and discussion

3.1 Setting time

The setting time of the GPC mixes are summarized in Figure 5. Across all mixes, the initial setting time ranged from 19 to 22 min, while the final setting time ranged from 27 to 34 min, indicating a relatively narrow and consistent setting window. The control mix, M1, showed an initial and final setting time of 20 and 30 min, respectively. Replacing 10% of slag with CCR in M2 extended the setting time to 22 and 34 min, due to CCR’s high Ca(OH)₂ content, which can slow early hydration reactions (Sun et al., 2023). In contrast, M3 showed reduced times of 19 and 28 min, suggesting that higher CCR levels enhance the alkaline environment, accelerating slag activation (Phoo-ngernkham et al., 2020; Hanjitsuwan et al., 2018). Ternary blends incorporating both CCR and MK at different replacement level of slag (M4 and M5) exhibited moderate to lower setting times. This could be attributed to the high pozzolanic activity and large surface area of MK, which promote early reactions with the high Ca content present in CCR, thereby helping to moderate and stabilize the setting behaviour. Notably, M5 recorded the shortest final setting time of 27 min, indicating synergistic reactivity between CCR and MK (Sathonsaowaphak et al., 2009). CCR, when used in binary blends with slag, tends to delay setting time at lower replacement levels. However, at higher levels or when incorporated into ternary blends with MK, it accelerates setting, likely due to increased Ca availability and enhanced reactivity from the combined effects of CCR and MK.

Figure 5

Figure 5. Setting time of geopolymer samples. The figure showed that the inclusion of CCR accelerates setting at lower replacement levels. However, at higher CCR contents or when blended with MK in ternary mixes, the setting time is reduced, indicating the influence of mix composition on geopolymerization kinetics.

3.2 Compressive strength

The compressive strength development of the GPC mixes over time is shown in Figures 6A–C. The control mix (M1) exhibited the highest early strength (7,109 and 9,938 psi at 1 and 7 days respectively), consistent with the high reactivity of slag in alkali-activated systems. Slag contributes readily to the formation of C–A–S–H gel, which is the primary binding phase in high-calcium geopolymer mortars and is responsible for rapid strength gain (Temuujin et al., 2009; Provis and Bernal, 2014; Nath and Sarker, 2014). Substituting slag with CCR in M2 and M3 led to reductions in early strength by 16.4% and 26.7% at 1 day, 19.1% and 29.9% at 7 days, respectively. This is likely due to CCR’s limited aluminosilicate content and slower contribution to gel formation (Hanjitsuwan et al., 2018). However, by 28 days, the reduction in strength decreased significantly to 12.0% for M2 and 21.5% for M3, indicating that CCR increasingly contributes to secondary C–S–H and C–A–S–H gel formation at later curing ages (Zhu et al., 2025). The ternary blends (M4 and M5) demonstrated compressive strength comparable to M1 at both early and later ages. At 28 days, the strength reductions were minimal, with 0.7% for M4 and 3.5% for M5. This improved performance may be attributed to the synergistic reaction between MK and CCR. MK, being rich in reactive aluminosilicates, promotes the formation of N–A–S–H gel, which complements the calcium-rich gels contributed by slag and CCR. This leads to the formation of hybrid C–A–S–H/N–A–S–H gel, enhancing microstructural development of the geopolymer matrix (Metwally et al., 2025; Dhana et al., 2024).

Figure 6

Figure 6. Compressive strength of geopolymer samples (A) at various ages, (B) control and binary blends at 28 days, and (C) control and ternary blends at 28 days. The results show progressive strength gain over time, with ternary mixes achieving comparable strength with the control. Conversely, the mix containing the highest proportion of CCR exhibited the lowest compressive strength at 28 days.

To further validate whether the observed differences in early and later-age compressive strengths across the geopolymer mixes were statistically significant, single-factor ANOVA and Tukey HSD test were conducted on the 1-, 7-, and 28-day compressive strength results. For the 1-day compressive strength, the ANOVA yielded a p-value of 0.087, which is greater than the 0.05 significance level, indicating that there was no significant difference in early strength among the mixes at this age and Tukey HSD was not conducted. This absence of significant difference at 1 day is expected because early-age strength in slag-based geopolymer systems is primarily governed by the rapid dissolution of slag and the formation of initial C–A–S–H gels, while the contribution from MK and CCR remain limited (Bernal et al., 2012). However, for the 7-day and 28-day compressive strengths, the ANOVA results yielded p-values of 8.48 × 10⁻⁸ and 6.81 × 10⁻⁵, respectively, both well below the 0.05 threshold. These results confirm that there were significant differences in compressive strength among the mixes at these curing ages, highlighting the notable influence of incorporating CCR and MK in slag-based geopolymers. Tukey’s HSD test was subsequently performed for the 7- and 28-day results, as shown in Table 2. Mixes with no significant difference in strength are labelled with the same letter, while those with statistically significant differences are labelled with different letters, as shown in Figures 7A,B. The results indicate that M2 and M3 had significantly lower strengths compared to M1, M4, and M5. Notably, M4 and M5 were statistically similar to M1 (p > 0.05), suggesting that combining slag with both CCR and MK can yield early and later-age compressive strengths comparable to those of 100% slag-based mix. These findings demonstrate that the synergistic use of CCR and MK offers a promising strategy for reducing slag content without compromising mechanical performance.

Table 2

Table 2. Tukey HSD pairwise comparisons of 7- and 28-days compressive strength.

Figure 7

Figure 7. Compressive Strength of Geopolymer Samples with Tukey HSD Grouping at (A) 7 Days (B) 28 Days. Bars labelled with the same letter indicate no statistically significant difference in strength as determined by Tukey HSD (p > 0.05). M2 and M3 showed significantly lower strength compared to others, while M4 and M5 exhibited strengths statistically similar to M1.

3.3 Microstructural analyses

3.3.1 XRD analysis

The XRD patterns at 7 and 28 days, as shown in Figure 8, revealed the evolution of geopolymer reaction products in slag-based GPC modified with CCR and MK. At 7 days, all samples exhibit a broad hump between 20° and 35° 2θ, characteristic of amorphous phases such as C–A–S–H gel in M1 and M3 (Gharieb and Khater, 2025; Li et al., 2025; Cong and Mei, 2021), however M4 showed a broader and more intense hump suggesting the presence of a hybrid C–A–S–H/N–A–S–H gel, as MK usually form N–A–S–H gel (Metwally et al., 2025; Rashad, 2013). The prominent peak around 40° 2θ in M4 is attributed to halite, a crystalline byproduct from excess sodium ions in the activator reacting with trace chlorides, possibly from raw materials or environmental exposure, consistent with findings in sodium-rich geopolymer systems (Sun and Vollpracht, 2018). At 28 days, the intensity and definition of the amorphous hump between 26°–35° 2θ increase, indicating continued gel development. M4 and M1 exhibits the stronger hump, confirming enhanced geopolymerization. In M4, this is due to the high reactivity of MK and its contribution to the formation of hybrid C–A–S–H/N–A–S–H gel. This synergy contributed to the superior 28-day compressive strength observed in this M4, which is comparable to M1 (Metwally et al., 2025; Rashad, 2013). The presence of additional crystalline peaks around 28–30° 2θ observed in M4 and more prominently in M3 corresponds to calcite and can be attributed to the carbonation of excess Ca(OH)₂ derived from CCR.

Figure 8

Figure 8. XRD pattern of samples at (A) 7-days, (B) 28-days. M4 shows a broader amorphous hump at 7 days and hybrid gel formation at 28 days due to MK, contributing to higher strength. M3 displays sharper calcite peaks from higher CCR content, corresponding to its lower strength.

3.3.2 FTIR analysis

The FTIR spectra at 7 and 28 days in Figure 9A,B indicate several characteristic bands, revealing the progressive chemical changes and gel formation in M1, M3, and M4. A broad band observed around 3,400 cm^-1 in all samples corresponds to O–H stretching vibrations of bound and free water molecules, reflecting water present within the geopolymer matrix (Nath and Sarker, 2014). This band is more prominent in M1 and decreases in intensity in M3 and M4 over time, indicating the consumption of water as geopolymerization progresses. Peaks near 1,640 cm^-1 are associated with H–O–H bending of physically bound water, also diminishing by 28 days, further supporting the continuation of hydration and gel development (Davidovits, 2008). The distinct peaks at around 1,450 cm^-1 represent C=O stretching vibrations, typically indicating carbonate phases resulting from carbonation of Ca-rich phases found in slag and CCR (Gharieb and Khater, 2025; Hu et al., 2025). This observation aligns with XRD results, which also revealed the presence of crystalline carbonate phases such as calcite.

Figure 9

Figure 9. FTIR spectra of samples at (A) 7-days, (B) 28-days. M1 and M4 exhibit stronger Si–O–T bands, reflecting enhanced gel formation, particularly in M4 due to the presence of MK together with CCR. Additionally, all samples show prominent carbonate peaks, attributed to the carbonation of calcium-rich components in slag and CCR.

The most significant structural evolution is observed in the Si–O–T asymmetric stretching band (T = Si or Al), located around 950–1,000 cm^-1, which signifies the development of geopolymer gels (C–A–S–H and N–A–S–H). This band became more intense by 28 days, particularly in M1 and M4, indicating higher degree of geopolymerization, attributed to the absence of CCR in M1 and the presence of MK together with CCR in M4 (Onutai et al., 2023; Barzoki and Gowayed, 2025). Additionally, bending vibrations of Si–O or Al–O bonds appear in the 450–550 cm^-1 region (T–O), consistently observed across all samples, indicating the stable formation of the geopolymeric framework (Liu et al., 2025; Chen et al., 2024). Overall, the FTIR results confirm that M4, containing both CCR and MK, show prominent and clearly defined peaks similar to M1. This suggest a more developed geopolymeric structures and higher reactivity in M4 compared to M3. It also revealed that the inclusion of CCR alone leads to lower early gel formation due to its limited aluminosilicate content. In contrast, the addition of MK enhances geopolymerization due to its high pozzolanic activity and large surface area, contributing positively to gel formation, structural integrity and the superior mechanical performance observed in the mix (Bernal et al., 2012; Bernal et al., 2013).

3.3.3 TGA analysis

As shown in Figure 10, the 28-day TGA curves reveal the thermal decomposition behaviour of M1, M3, and M4, providing insight into water content, gel stability, and carbonate decomposition. All samples exhibit an initial rapid mass loss below 200 °C, corresponding to the evaporation of physically bound water and loosely bound hydration products, which accounts for approximately 15% loss of the total mass. This phase is typical of geopolymer systems and is associated with the loss of pore water and weakly held hydroxyl groups in early-formed gels (David and ovits, 1994; Provis and Bernal, 2014; Nath and Sarker, 2014; Ranjbar et al., 2014).

Figure 10

Figure 10. TGA curve of samples at 28-days. All samples show greatest mass loss below 200 °C from water evaporation. M1 shows higher loss between 350 °C and 600 °C due to less stable gels, while M3 and M4 exhibit greater stability but higher carbonate decomposition beyond 800 °C from CCR content.

Between 200 °C and 600 °C, all mixes experienced gradual mass loss associated with the decomposition of chemically bound phases and the restructuring of geopolymer gels, though the extent and nature of the loss varied across compositions. Between 200 °C and 350 °C, all three mixes show a similar and steady mass loss, indicating that this region is dominated by the decomposition of chemically bound water and initial structural reorganization of the geopolymer gels, such as partial breakdown of C–A–S–H or N–A–S–H networks (Kina et al., 2025; Yang et al., 2023). From 350 °C to 600 °C, M1 exhibits a noticeably higher mass loss than M3 and M4. This additional loss is likely due to less stable or more loosely bound gel structures in the control mix, which may undergo structural collapse or dehydroxylation more readily than the more complex hybrid gels present in M3 and M4 (Li et al., 2025). This indicate that C–A–S–H gel in M1 is less stable at mid-range temperature while the incorporation of CCR and especially MK in M4 likely leads to the formation of more cross-linked aluminosilicate networks, which are thermally more stable.

Beyond 600 °C, however, the trend changes around 800 °C, as M1 experiences a relatively lower mass loss rate compared to M3 and M4. This phase is largely attributed to the decarbonation of calcite (CaCO₃), formed through the carbonation of excess Ca(OH)₂, which is more prevalent in CCR-containing mixes (Hu et al., 2025; Aziz et al., 2020). Hence, M3 and M4 display greater mass loss in this range, consistent with stronger carbonate signals in their FTIR and XRD. Generally, while all mixes experience their greatest mass loss below 180 °C, the control mix exhibits greater thermal instability between 350 and 600 °C but undergoes less decarbonation above 600 °C. The inclusion of CCR enhances mid-range thermal stability but increases carbonate-related decomposition at high temperatures. However, the incorporation of MK reduces carbonation-related mass loss compared to CCR alone, although it remains slightly higher than that observed in the control mix.

3.3.4 SEM analysis

Figures 11A–C present the 7-days SEM micrographs of M1, M3, and M4 highlight clear differences in microstructure, shaped by their binder composition and reactivity. M1 presents a relatively dense and compact matrix with fewer unreacted slag particles, indicating effective C–A–S–H gel formation (Temuujin et al., 2009; Zhang et al., 2025; Chen et al., 2025). This observation is supported by FTIR results, which show a strong and well-defined Si–O–T stretching band, and by the broad amorphous hump observed between 26° and 35° 2θ in the XRD pattern, both indicating extensive gel formation. However, microcracks are visible, likely resulting from shrinkage, and pores are also observed, probably caused by entrapped air or water loss during curing. M3 shows a less compact and more porous microstructure, with a greater number of partially or unreacted slag particles, incompletely reacted CCR, and more extensive cracking. These features indicate incomplete geopolymerization and weaker particle bonding, a typical result when high levels of calcium from CCR dilute the reactive aluminosilicate content, leading to segregation or uneven gel formation (Yan et al., 2024).

Figure 11

Figure 11. SEM images of samples at 7-days (A) M1, (B) M3, and (C) M4. M1 shows a dense matrix with minor cracks and pores, indicating effective gel formation. M3 displays a porous, cracked structure with unreacted particles, suggesting incomplete geopolymerization. M4 exhibits a denser, more refined microstructure with fewer cracks, attributed to enhanced gel formation from MK incorporation.

In contrast, M4, similar to M1, exhibits a refined and denser matrix with fewer cracks, although some pores are still present. The incorporation of MK increases the availability of reactive aluminosilicates, promoting the formation of a hybrid C–A–S–H/N–A–S–H gel, which enhances particle bonding, densifies the matrix, and helps control cracking. This observation aligns with previous findings that MK addition leads to finer gel networks and reduced microstructural defects in blended geopolymer systems (Metwally et al., 2025; Choi et al., 2025; Qiao et al., 2024). The SEM-EDS analysis of M4 is shown in Figure 12, with the EDS spectrum indicating the significant presence of key geopolymer-forming elements such as Ca, Si, Na, and Al, which supports the formation of a hybrid C–A–S–H/N–A–S–H gel resulting from the combined contributions of slag, CCR, and MK. Thus, the SEM analysis confirms that M3 exhibits the most compromised microstructure, whereas M1 and M4 display more refined and balanced microstructure, characterized by effective gel development despite the presence of minor porosity.

Figure 12

Figure 12. SEM-EDS analysis of M4. The spectrum confirms the presence of Ca, Si, Na, and Al, indicating the formation of a hybrid C–A–S–H/N–A–S–H gel from the combined effects of slag, CCR, and MK.

4 Conclusion

This study investigates the performance of slag-based GPC incorporating calcium carbide residue (CCR) as a supplementary precursor. The combined effect of CCR and metakaolin (MK) was also examined to assess their influence on both mechanical and microstructural properties. Binary (slag/CCR) and ternary (slag/CCR/MK) precursor systems were explored to evaluate their impact on gel formation mechanisms, with a particular focus on the development of N–A–S–H and C–A–S–H gel phases. A factorial experimental design was adopted to examine the effects of CCR and MK at replacement levels of 10%, 15%, and 20%. The performance of the mixes was assessed through fresh and hardened properties, supported by detailed microstructural characterization. Based on the experimental findings, the following conclusions are drawn:

1. CCR influenced the setting behavior of the mixes, delaying it by approximately 13% at lower dosages but accelerating it by about 10% at higher levels or when combined with MK. This behavior is attributed to the increased availability of Ca from CCR and the enhanced pozzolanic reactivity of MK, whose fine particle size and high surface area promote early-age geopolymerization. Despite this variation, all mixes achieved rapid-setting characteristics, with initial setting times ranging from 19 to 22 min and final setting times ranging from 27 to 34 min, confirming that CCR can be effectively incorporated as a supplementary precursor in slag-based GPC without compromising the workability.

2. The binary mixes showed a slight reduction in strengths compared to the control at higher replacement levels, due to the limited aluminosilicate content in CCR. However, ternary mixes containing CCR and MK achieved strengths comparable to the control, reaching 96%–99% of the control’s 28-day compressive strength, highlighting potential of CCR to enhance performance when paired with more reactive materials like MK. Statistical analysis further confirmed these trends, showing no significant difference in strength of the mixes at 1 day, while significant differences observed at 7 and 28 days reflected the positive influence of optimized precursor combinations on strength development.

3. Microstructural analyses provided strong evidence of the beneficial role of CCR in the geopolymer matrix. SEM imaging coupled with EDS analysis revealed that the incorporation of CCR, especially in ternary blends with MK, led to a more compact and refined microstructure with reduced porosity and fewer unreacted particles. This is attributed to the formation of a hybrid C–A–S–H/N–A–S–H gel network. XRD analysis further supported this by displaying a broad amorphous hump, indicative of an extensive gel phase with low crystallinity. FTIR spectra showed more intense Si–O–T bands, suggesting enhanced geopolymerization and gel formation. Additionally, TGA results demonstrated improved thermal stability in the mid-temperature range, further confirming the structural enhancement provided by the hybrid gel system formed through CCR and MK incorporation.

4. Synergistic effects in ternary systems with MK promote the balance of Si/Al and Ca/Si ratios, enhancing the polycondensation process and contributing to a more compact and interconnected gel matrix during geopolymerization.

5. Future work will include a comprehensive life cycle assessment (LCA) and techno-economic analysis (TEA) to evaluate the environmental and economic feasibility of using CCR and MK in slag-based GPC. In addition, long-term durability testing will be conducted to assess the material’s performance under realistic exposure conditions. These studies will provide a more complete understanding of the sustainability and practical applicability of the developed systems.

Data availability statement

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding authors.

Author contributions

TM: Conceptualization, Data curation, Investigation, Methodology, Software, Writing – original draft. DS: Investigation, Methodology, Writing – original draft. EF: Conceptualization, Funding acquisition, Methodology, Project administration, Supervision, Validation, Writing – review and editing, Resources, Visualization.

Funding

The authors declare that financial support was received for the research and/or publication of this article. Georgia Tech Sustainability NEXT Grant (DE00023413) and Brook Byers Institute for Sustainable Systems Faculty Fellow (DE00027490). This work was performed in part at the Georgia Tech Institute for Matter and Systems, a member of the National Nanotechnology Coordinated Infrastructure (NNCI), which is supported by the National Science Foundation (ECCS-2025462).

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Generative AI statement

The authors declare that no Generative AI was used in the creation of this manuscript.

Any alternative text (alt text) provided alongside figures in this article has been generated by Frontiers with the support of artificial intelligence and reasonable efforts have been made to ensure accuracy, including review by the authors wherever possible. If you identify any issues, please contact us.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

References

Adufu, Y. D., Sore, S. O., Nshimiyimana, P., Messan, A., and Escadeillas, G. (2023). Effect of curing conditions on physico-mechanical properties of metakaolin-based geopolymer concrete containing calcium carbide residue. MRS Adv. 8, 591–595. doi:10.1557/s43580-023-00572-8

CrossRef Full Text | Google Scholar

Ahmad, M. R., Fernàndez-Jimenez, A., Chen, B., Leng, Z., and Dai, J. G. (2024). Low-carbon cementitious materials: scale-up potential, environmental impact and barriers. Constr. Build. Mater 455, 139087. doi:10.1016/j.conbuildmat.2024.139087

CrossRef Full Text | Google Scholar

Amran, M., Al-Fakih, A., Chu, S. H., Fediuk, R., Haruna, S., Azevedo, A., et al. (2021a). Long-term durability properties of geopolymer concrete: an in-depth review. Case Stud. Constr. Mater. 15, e00661. doi:10.1016/j.cscm.2021.e00661

CrossRef Full Text | Google Scholar

Amran, M., Debbarma, S., and Ozbakkaloglu, T. (2021b). Fly ash-based eco-friendly geopolymer concrete: a critical review of the long-term durability properties. Constr. Build. Mater 270, 121857. doi:10.1016/j.conbuildmat.2020.121857

CrossRef Full Text | Google Scholar

Arulrajah, A., Mohammadinia, A., Phummiphan, I., Horpibulsuk, S., and Samingthong, W. (2016). Stabilization of recycled demolition aggregates by geopolymers comprising calcium carbide residue, fly ash and slag precursors. Constr. Build. Mater 114, 864–873. doi:10.1016/j.conbuildmat.2016.03.150

CrossRef Full Text | Google Scholar

Arafa, S. A., Ali, A. Z. M., Awal, A. S. M. A., and Loon, L. Y. (2018). “Optimum mix for fly ash geopolymer binder based on workability and compressive strength,” in IOP Conf Ser Earth Environ Sci (Bristol, United Kingdom: Institute of Physics Publishing). doi:10.1088/1755-1315/140/1/012157

CrossRef Full Text | Google Scholar

ASTM C109 (2024). Test method for compressive strength of hydraulic cement mortars (using 50mm [2 in.] cube specimens). doi:10.1520/C0109_C0109M-24

CrossRef Full Text | Google Scholar

ASTM C39 (2024). Test method for compressive strength of cylindrical concrete specimens. doi:10.1520/C0039_C0039M-24

CrossRef Full Text | Google Scholar

ASTM C618 (2023). Specification for coal ash and raw or calcined natural pozzolan for use in concrete. doi:10.1520/C0618-23E01

CrossRef Full Text | Google Scholar

ASTM C807 (2021). Test method for time of setting of hydraulic cement mortar by modified vicat needle. doi:10.1520/C0807-21

CrossRef Full Text | Google Scholar

ASTM C989/C989M (2024). Specification for slag cement for use in concrete and mortars. doi:10.1520/C0989_C0989M-24

CrossRef Full Text | Google Scholar

Aziz, I. H., Al Bakri Abdullah, M. M., Heah, C. Y., and Liew, Y. M. (2020). Behaviour changes of ground granulated blast furnace slag geopolymers at high temperature. Adv. Cem. Res. 32, 465–475. doi:10.1680/jadcr.18.00162

CrossRef Full Text | Google Scholar

Barzoki, P. K., and Gowayed, Y. (2025). Tailoring metakaolin-based geopolymers for high-temperature stability: Chemical, thermal and mechanical insights. Ceram. Int. 51, 11346–11353. doi:10.1016/j.ceramint.2024.12.553

CrossRef Full Text | Google Scholar

Bayrak, B., Çelebi, O., Öz, A., Ustabaş, İ., Kaplan, G., and Cüneyt Aydın, A. (2023). Effect of aluminosilicate precursors and curing regime on physico-mechanical durability and microstructural characteristics of coral geopolymers (Cor-Geo): cleaner production for coral islands. Constr. Build. Mater 407, 133596. doi:10.1016/j.conbuildmat.2023.133596

CrossRef Full Text | Google Scholar

Bernal, S. A., Mejía De Gutiérrez, R., and Provis, J. L. (2012). Engineering and durability properties of concretes based on alkali-activated granulated blast furnace slag/metakaolin blends. Constr. Build. Mater 33, 99–108. doi:10.1016/j.conbuildmat.2012.01.017

CrossRef Full Text | Google Scholar

Bernal, S. A., Provis, J. L., Walkley, B., San Nicolas, R., Gehman, J. D., Brice, D. G., et al. (2013). Gel nanostructure in alkali-activated binders based on slag and fly ash, and effects of accelerated carbonation. Cem. Concr. Res. 53, 127–144. doi:10.1016/j.cemconres.2013.06.007

CrossRef Full Text | Google Scholar

Bonfante, F., Ferrara, G., Humbert, P., Garufi, D., Tulliani, J. M., and Palmero, P. (2025). Aqueous carbonation of EAF steel slag to produce supplementary cementitious material: effects on mineral composition, hydration reactivity and mechanical properties. Constr. Build. Mater 479, 141361. doi:10.1016/j.conbuildmat.2025.141361

CrossRef Full Text | Google Scholar

Chen, C., Shenoy, S., Sasaki, K., Zhang, H., and Tian, Q. (2024). Influence of liquid-to-solid ratios on properties and microstructure of coal gasification slag-based one-part geopolymer. Case Stud. Constr. Mater. 20, e02924. doi:10.1016/j.cscm.2024.e02924

CrossRef Full Text | Google Scholar

Chen, M., Wu, D., Chen, K., Liu, C., Zhou, G., and Cheng, P. (2025). The effects of solid activator dosage and the liquid-solid ratio on the properties of FA-GGBS based one-part geopolymer. Constr. Build. Mater 463, 140067. doi:10.1016/j.conbuildmat.2025.140067

CrossRef Full Text | Google Scholar

Choi, H., Pour-Ghaz, M., and Park, S. (2025). Compressive strength degradation of metakaolin-based geopolymer with an excessively high S/A ratio: insights from nanoindentation on N-A-S-H gel structure. J. Build. Eng. 108, 112870. doi:10.1016/j.jobe.2025.112870

CrossRef Full Text | Google Scholar

Cong, P., and Mei, L. (2021). Using silica fume for improvement of fly ash/slag based geopolymer activated with calcium carbide residue and gypsum. Constr. Build. Mater 275, 122171. doi:10.1016/j.conbuildmat.2020.122171

CrossRef Full Text | Google Scholar

Davidovits, J. (1994). “PROPERTIES OF GEOPOLYMER CEMENTS,” in Proceedings of the First International Conference on Alkaline Cements and Concretes, Scientific Research Institute on Binders and Materials (Kiev: Kiev State Technical University), 131–149. Available online at: www.geopolymer.org.

Google Scholar

Davidovits, J. (1991). Geopolymers: inorganic polymeric new materials. J. OfThamalAnalysis 37, 1633–1656. doi:10.1007/bf01912193

CrossRef Full Text | Google Scholar

Davidovits, J. (2008). Geopolymer CHemistry and applications. 5th edition. Available online at: https://www.researchgate.net/publication/265076752.

Google Scholar

Deb, P. S., Nath, P., and Sarker, P. K. (2014). The effects of ground granulated blast-furnace slag blending with fly ash and activator content on the workability and strength properties of geopolymer concrete cured at ambient temperature. Mater Des. 62, 32–39. doi:10.1016/j.matdes.2014.05.001

CrossRef Full Text | Google Scholar

Dhanalakshmi, K., Sudarvizhi, S. M., Jose, P. A., and Dhanasekaran, M. (2024). Exploring the chemistry of metakaolin-based geopolymers. J. Polym. Res. 31, 349. doi:10.1007/s10965-024-04170-6

CrossRef Full Text | Google Scholar

Fořt, J., Šál, J., Ševčík, R., Doleželová, M., Keppert, M., Jerman, M., et al. (2021). Biomass fly ash as an alternative to coal fly ash in blended cements: functional aspects. Constr. Build. Mater 271, 121544. doi:10.1016/j.conbuildmat.2020.121544

CrossRef Full Text | Google Scholar

Ghafari, E., Ghahari, S., Feys, D., Khayat, K., Baig, A., and Ferron, R. (2020). Admixture compatibility with natural supplementary cementitious materials. Cem. Concr. Compos 112, 103683. doi:10.1016/j.cemconcomp.2020.103683

CrossRef Full Text | Google Scholar

Ghafoor, M. T., and Fujiyama, C. (2023). Constitutive model for self-compacting geopolymer mortar based on fly ash content. J. Build. Eng. 71, 106462. doi:10.1016/j.jobe.2023.106462

CrossRef Full Text | Google Scholar

Ghafoor, M. T., Khan, Q. S., Qazi, A. U., Sheikh, M. N., and Hadi, M. N. S. (2021). Influence of alkaline activators on the mechanical properties of fly ash based geopolymer concrete cured at ambient temperature. Constr. Build. Mater 273, 121752. doi:10.1016/j.conbuildmat.2020.121752

CrossRef Full Text | Google Scholar

Gharieb, M., and Khater, H. M. (2025). Valorization study of mixing aluminum slag with binary geopolymer blends to produce lightweight geopolymer concrete. Constr. Build. Mater 466, 140288. doi:10.1016/j.conbuildmat.2025.140288

CrossRef Full Text | Google Scholar

Hafez, H., Kassim, D., Kurda, R., Silva, R. V., and de Brito, J. (2021). Assessing the sustainability potential of alkali-activated concrete from electric arc furnace slag using the ECO2 framework. Constr. Build. Mater 281, 122559. doi:10.1016/j.conbuildmat.2021.122559

CrossRef Full Text | Google Scholar

Hanani Ismail, A., Kusbiantoro, A., Tajunnisa, Y., Jaya Ekaputri, J., and Laory, I. (2024). A review of aluminosilicate sources from inorganic waste for geopolymer production: sustainable approach for hydrocarbon waste disposal. Clean. Mater. 13, 100259. doi:10.1016/j.clema.2024.100259

CrossRef Full Text | Google Scholar

Hanjitsuwan, S., Phoo-ngernkham, T., and Damrongwiriyanupap, N. (2017). Comparative study using Portland cement and calcium carbide residue as a promoter in bottom ash geopolymer mortar. Constr. Build. Mater 133, 128–134. doi:10.1016/j.conbuildmat.2016.12.046

CrossRef Full Text | Google Scholar

Hanjitsuwan, S., Phoo-ngernkham, T., yuan Li, L., Damrongwiriyanupap, N., and Chindaprasirt, P. (2018). Strength development and durability of alkali-activated fly ash mortar with calcium carbide residue as additive. Constr. Build. Mater 162, 714–723. doi:10.1016/j.conbuildmat.2017.12.034

CrossRef Full Text | Google Scholar

Horpibulsuk, S., Munsrakest, V., Udomchai, A., Chinkulkijniwat, A., and Arulrajah, A. (2014). Strength of sustainable non-bearing masonry units manufactured from calcium carbide residue and fly ash. Constr. Build. Mater 71, 210–215. doi:10.1016/j.conbuildmat.2014.08.033

CrossRef Full Text | Google Scholar

Hu, Z., Gu, X., Li, Z., Hu, Z., Ge, X., Liu, J., et al. (2025). A novel solid waste activator for coal gasification slag-based geopolymers: sodium-based desulfurization ash and carbide slag. Constr. Build. Mater 470, 140655. doi:10.1016/j.conbuildmat.2025.140655

CrossRef Full Text | Google Scholar

Ketana, N. S., Srinivasa Reddy, V., Rao, M. V. S., and Shrihari, S. (2021). “Effect of various parameters on the workability and strength properties of geopolymer concrete,” in E3S Web of Conferences (Les Ulis, France: EDP Sciences). doi:10.1051/e3sconf/202130901102

CrossRef Full Text | Google Scholar

Kina, C., Tanyildizi, H., and Acik, V. (2025). Hybrid portland cement-slag-based geopolymer mortar: strength, microstructural and environmental assessment. Process Saf. Environ. Prot. 195, 106771. doi:10.1016/j.psep.2025.106771

CrossRef Full Text | Google Scholar

Li, J., Sun, Q., and Zu, Y. (2025). Influence of steel slag doping on the mechanical properties and microstructural characterization of coal gangue based geopolymer. Mater Chem. Phys. 333, 130251. doi:10.1016/j.matchemphys.2024.130251

CrossRef Full Text | Google Scholar

Liu, H., Liu, Y., Duan, P., Bian, H., Wang, K., Lou, J., et al. (2025). Design and optimization of binary geopolymers derived from red mud-coal gasification slag based on response surface methodology. Constr. Build. Mater 464, 140203. doi:10.1016/j.conbuildmat.2025.140203

CrossRef Full Text | Google Scholar

Mahamat Ahmat, A., Johnson Alengaram, U., Fazaulnizam Shamsudin, M., Mahmoud Alnahhal, A., Shazril Idris Ibrahim, M., Ibrahim, S., et al. (2023). Assessment of sustainable eco-processed pozzolan (EPP) from palm oil industry as a fly ash replacement in geopolymer concrete. Constr. Build. Mater 387, 131424. doi:10.1016/j.conbuildmat.2023.131424

CrossRef Full Text | Google Scholar

Metwally, G. A. M., Elemam, W. E., Mahdy, M., and Ghannam, M. (2025). A comprehensive review of metakaolin-based ultra-high-performance geopolymer concrete enhanced with waste material additives. J. Build. Eng. 103, 112019. doi:10.1016/j.jobe.2025.112019

CrossRef Full Text | Google Scholar

Mohamad, N., Muthusamy, K., Embong, R., Kusbiantoro, A., and Hashim, M. H. (2021). “Environmental impact of cement production and solutions: a review,” in Mater today Proc (Elsevier Ltd), 741–746. doi:10.1016/j.matpr.2021.02.212

CrossRef Full Text | Google Scholar

Mohammed, T. O., Bin Harun, M. Z., Liu, J., and Fanijo, E. O. (2025). Effect of oil palm broom fiber on the mechanical properties of rice husk Ash–blended concrete. Recent Prog. Mater 07, 1–15. doi:10.21926/rpm.2503013

CrossRef Full Text | Google Scholar

Nath, P., and Sarker, P. K. (2014). Effect of GGBFS on setting, workability and early strength properties of fly ash geopolymer concrete cured in ambient condition. Constr. Build. Mater 66, 163–171. doi:10.1016/j.conbuildmat.2014.05.080

CrossRef Full Text | Google Scholar

Nikolakopoulos, A., Steriotis, T., Charalambopoulou, G., Karagiannakis, G., Dimitrakis, D., Michalis, V., et al. (2024). Reducing carbon emissions in cement production through solarization of the calcination process and thermochemical energy storage. Comput. Chem. Eng. 180, 108506. doi:10.1016/j.compchemeng.2023.108506

CrossRef Full Text | Google Scholar

Obeng, J., Andrews, A., Adom-Asamoah, M., and Adjei, S. (2023). Effect of calcium carbide residue on the sulphate resistance of metakaolin-based geopolymer mortars. Clean. Mater. 7, 100177. doi:10.1016/j.clema.2023.100177

CrossRef Full Text | Google Scholar

Obeng, J., Andrews, A., Adom-Asamoah, M., and Owusu-Twumasi, J. (2024). Bond behavior of reinforcing steel bars in metakaolin - calcium carbide residue-based geopolymer concrete. Eng. Res. Express 6, 035113. doi:10.1088/2631-8695/ad722b

CrossRef Full Text | Google Scholar

Onutai, S., Sato, J., and Osugi, T. (2023). Possible pathway of zeolite formation through alkali activation chemistry of metakaolin for geopolymer–zeolite composite materials: ATR-FTIR study. J. Solid State Chem. 319, 123808. doi:10.1016/j.jssc.2022.123808

CrossRef Full Text | Google Scholar

Phoo-ngernkham, T., Phiangphimai, C., Intarabut, D., Hanjitsuwan, S., Damrongwiriyanupap, N., yuan Li, L., et al. (2020). Low cost and sustainable repair material made from alkali-activated high-calcium fly ash with calcium carbide residue. Constr. Build. Mater 247, 118543. doi:10.1016/j.conbuildmat.2020.118543

CrossRef Full Text | Google Scholar

Phummiphan, I., Horpibulsuk, S., Phoo-ngernkham, T., Arulrajah, A., and Shen, S.-L. (2017). Marginal lateritic soil stabilized with calcium carbide residue and fly ash geopolymers as a sustainable pavement base material. J. Mater. Civ. Eng. 29, 04016195. doi:10.1061/(ASCE)MT.1943-5533.0001708

CrossRef Full Text | Google Scholar

Provis, J. L., and Bernal, S. A. (2014). Geopolymers and related alkali-activated materials. Annu. Rev. Mater Res. 44, 299–327. doi:10.1146/annurev-matsci-070813-113515

CrossRef Full Text | Google Scholar

Qiao, J., Lv, Y., Peng, H., Han, W., Pan, B., and Zhang, B. (2024). Performance and characterization of fly ash-metakaolin-based geopolymer pastes. Mater Today Commun. 41, 110293. doi:10.1016/j.mtcomm.2024.110293

CrossRef Full Text | Google Scholar

Ranjbar, N., Mehrali, M., Alengaram, U. J., Metselaar, H. S. C., and Jumaat, M. Z. (2014). Compressive strength and microstructural analysis of fly ash/palm oil fuel ash based geopolymer mortar under elevated temperatures. Constr. Build. Mater 65, 114–121. doi:10.1016/j.conbuildmat.2014.04.064

CrossRef Full Text | Google Scholar

Rashad, A. M. (2013). Metakaolin as cementitious material: history, scours, production and composition-A comprehensive overview. Constr. Build. Mater 41, 303–318. doi:10.1016/j.conbuildmat.2012.12.001

CrossRef Full Text | Google Scholar

Rattanasak, U., and Chindaprasirt, P. (2009). Influence of NaOH solution on the synthesis of fly ash geopolymer. Min. Eng. 22, 1073–1078. doi:10.1016/j.mineng.2009.03.022

CrossRef Full Text | Google Scholar

Sabet, F. A., Libre, N. A., and Shekarchi, M. (2013). Mechanical and durability properties of self consolidating high performance concrete incorporating natural zeolite, silica fume and fly ash. Constr. Build. Mater 44, 175–184. doi:10.1016/j.conbuildmat.2013.02.069

CrossRef Full Text | Google Scholar

Sathonsaowaphak, A., Chindaprasirt, P., and Pimraksa, K. (2009). Workability and strength of lignite bottom ash geopolymer mortar. J. Hazard Mater 168, 44–50. doi:10.1016/j.jhazmat.2009.01.120

PubMed Abstract | CrossRef Full Text | Google Scholar

Scrivener, K. L., John, V. M., and Gartner, E. M. (2018). Eco-efficient cements: potential economically viable solutions for a low-CO2 cement-based materials industry. Cem. Concr. Res. 114, 2–26. doi:10.1016/j.cemconres.2018.03.015

CrossRef Full Text | Google Scholar

Somna, K., Jaturapitakkul, C., Kajitvichyanukul, P., and Chindaprasirt, P. (2011). NaOH-activated ground fly ash geopolymer cured at ambient temperature. Fuel 90, 2118–2124. doi:10.1016/j.fuel.2011.01.018

CrossRef Full Text | Google Scholar

Sumesh, M., Alengaram, U. J., Jumaat, M. Z., Mo, K. H., and Alnahhal, M. F. (2017). Incorporation of nano-materials in cement composite and geopolymer based paste and mortar – a review. Constr. Build. Mater 148, 62–84. doi:10.1016/j.conbuildmat.2017.04.206

CrossRef Full Text | Google Scholar

Sun, Z., and Vollpracht, A. (2018). Isothermal calorimetry and in-situ XRD study of the NaOH activated fly ash, metakaolin and slag. Cem. Concr. Res. 103, 110–122. doi:10.1016/j.cemconres.2017.10.004

CrossRef Full Text | Google Scholar

Sun, X., Liu, J., Qiu, J., Wu, P., and Zhao, Y. (2022). Alkali activation of blast furnace slag using a carbonate-calcium carbide residue alkaline mixture to prepare cemented paste backfill. Constr. Build. Mater 320, 126234. doi:10.1016/j.conbuildmat.2021.126234

CrossRef Full Text | Google Scholar

Sun, D., Yin, F., Deng, Y., Liu, K., Tang, J., Shen, C., et al. (2023). Utilization of carbide slag in autoclaved aerated concrete (CS-AAC) and optimization: foaming, hydration process, and physic-mechanical properties. Case Stud. Constr. Mater. 19, e02354. doi:10.1016/j.cscm.2023.e02354

CrossRef Full Text | Google Scholar

Temuujin, J., van Riessen, A., and Williams, R. (2009). Influence of calcium compounds on the mechanical properties of fly ash geopolymer pastes. J. Hazard Mater 167, 82–88. doi:10.1016/j.jhazmat.2008.12.121

PubMed Abstract | CrossRef Full Text | Google Scholar

Vázquez-Rodríguez, F., Elizondo, N., Montes-González, M., Gómez-Rodríguez, C., González-Carranza, Y., Guzmán, A. M., et al. (2023). Microstructural and mechanical characteristics of alkali-activated binders composed of milled fly ash and granulated blast furnace slag with µ-Limestone addition. Materials 16, 3818. doi:10.3390/ma16103818

PubMed Abstract | CrossRef Full Text | Google Scholar

Yan, S., Wu, Y., Lai, W., Yang, Y., Liu, G., Dan, J., et al. (2024). Effect of additional Al sources on early-age strength of fly ash-based geopolymer containing calcium carbide residue and Glauber’s salt as activators. Constr. Build. Mater 447, 138158. doi:10.1016/j.conbuildmat.2024.138158

CrossRef Full Text | Google Scholar

Yang, P., Liu, L., Suo, Y., Xie, G., Sun, W., and Zhang, C. (2023). Physical-chemical coupling excitation of low activity coal gasification slag solid waste and its application as a backfill cementitious material. Constr. Build. Mater 401, 132973. doi:10.1016/j.conbuildmat.2023.132973

CrossRef Full Text | Google Scholar

Zhang, P., Zheng, Y., Wang, K., and Zhang, J. (2018). A review on properties of fresh and hardened geopolymer mortar. Compos B Eng. 152, 79–95. doi:10.1016/j.compositesb.2018.06.031

CrossRef Full Text | Google Scholar

Zhang, P., Mao, Y., Gao, Z., Guo, J., and Zheng, M. (2025). Efficient utilization of waste drilling mud to prepare material stabilized with fly ash/slag based geopolymer for subgrade engineering. J. Environ. Manage 373, 123600. doi:10.1016/j.jenvman.2024.123600

PubMed Abstract | CrossRef Full Text | Google Scholar

Zhu, H., Yang, S., Wu, C., Wang, T., Qin, J., Ma, K., et al. (2025). Effect of calcium carbide residue dosage on the workability and mechanical properties of geopolymer filling cementitious materials. Constr. Build. Mater 470, 140649. doi:10.1016/j.conbuildmat.2025.140649

CrossRef Full Text | Google Scholar