Cementitious concrete composite is an extensively used construction material that is strong in compression but has limited tensile properties (Khan et al., 2018; Farooqi and Ali, 2019; Li, 2019). To cater this issue, the interest of researchers has increased towards materials advancements in the form of fiber-reinforced concrete (Shakor and Pimplikar, 2011; Khan et al., 2022a; Farooqi and Ali, 2022). However, ordinary fiber-reinforced concrete (FRC) only slightly improves tensile strain capacity despite yielding advanced tensile properties compared to conventional concrete (Cao and Khan, 2021; Khan et al., 2022b). In the early 1990s, the development of engineered cementitious composites (ECC) ushered in a significant improvement in tensile ductility. ECC demonstrated remarkable attributes such as multiple cracking behavior and strain-hardening, resulting in significantly enhanced tensile properties compared to conventional concrete and fiber-reinforced composites. Moreover, ECC exhibited the ability to resist crack propagation under external loads, with cracks reaching a certain point and generating additional tensile distortion due to micro-crack emergence (Şahmaran and Li, 2009; Qaidi et al., 2022). These outstanding characteristics made ECC a preferred choice for extensive projects like bridges and high-rise buildings, ensuring prolonged service life and improved functionality (Maruta, 2005; Luković et al., 2019; Li et al., 2020).

Engineered cementitious composites (ECC) typically comprise cement, silica sand, fly ash, and fibers (Wang and Li, 2007; Shanmugasundaram and Praveenkumar, 2021). However, ECC’s heavy reliance on cement and its lack of coarse aggregates necessitates two to three times more cement usage than conventional concrete, contributing to approximately 8% of global CO₂ emissions from cement production (Luukkonen et al., 2018; Riaz Ahmad et al., 2023). This unsustainable production pattern has driven the exploration of alternative binders for ECC, including geopolymer concrete. Geopolymers, comprised of alkaline activators and aluminosilicate materials, have emerged as a more sustainable alternative in developing engineered geopolymer composites (EGC) (Shakor et al., 2023). Geopolymer concrete’s ecological friendliness in construction materials is due to the abundant availability of raw materials, robust mechanical properties, and exceptional durability (Davidovits, 1991; Bakharev et al., 1999; Bakharev et al., 2003; Lemougna et al., 2016; Wang et al., 2017).

Compared to traditional concrete, EGC exhibits nearly identical or superior mechanical characteristics and durability while significantly reducing CO₂ emissions (Yang et al., 2013; Provis, 2018; Lao et al., 2023a; Lao et al., 2023b). Furthermore, when compared to ECC, EGC boasts similar static loading properties but outperforms it in terms of dynamic loading properties (Shaikh, 2013; Nematollahi et al., 2017; Trindade et al., 2020; Cai et al., 2021; Zhang et al., 2022). EGC can be tailored to various material properties by employing diverse mix designs, fiber contents, mixing techniques, and curing methods (Ohno and Li, 2018; Zahid et al., 2018; Zhong and Zhang, 2022). Figure 1 illustrates how the utilization of such waste materials can positively impact both the economy and the environment, particularly given the abundance of these materials and the growing demand for cost-effective construction as the population continues to expand (Jindal, 2019; Ilcan et al., 2022; Lan et al., 2022; Sandanayake et al., 2022; Ahmad et al., 2023).

Geopolymer concrete obtains superior mechanical properties from the three-dimensional network structures of oxides generated through specialized inorganic polycondensation. This stable network structure grants remarkable durability and high strength to the geopolymer concrete during service. This protective effect on engineering structures ensures the concrete’s longevity (Davidovits, 1991; Wang et al., 2021; Rajak et al., 2022). Geopolymer concrete’s cementitious materials can be classified into three categories based on their calcium content: no calcium, low calcium, and high calcium (Chindaprasirt et al., 2007; Duxson et al., 2007; Adamiec et al., 2008; Provis and Van Deventer, 2009; Elchalakani et al., 2018; Luukkonen et al., 2018). The primary representatives of these categories are metakaolin, fly ash, and slag, respectively. Geopolymer concrete with metakaolin exhibits greater strength and durability than OPC-based materials (Mohmmad et al., 2023). However, the plate-shaped particles of metakaolin create rheological difficulties that complicate the manufacturing process (Adamiec et al., 2008; Li et al., 2010; Luukkonen et al., 2018). In alkali-activated reaction products of slag, the C-S-H and C-A-S-H gels with low Ca/Si ratios provide high strength and acid resistance to slag-based geopolymer materials (Provis and Van Deventer, 2009). Nonetheless, the high-temperature endurance of geopolymer materials based on slag reduces, while their dry shrinkage deformation and creep rise (Buchwald et al., 2005; Atiş et al., 2009; Khan and Ali, 2020).

Given the diverse mix compositions, intricate high-temperature mechanical properties, and varied testing methods, it is vital to comprehensively analyze existing research on the temperature-dependent material traits of Engineered Geopolymer Composites (EGC). This review primarily focuses on the influence of material composition and manufacturing procedures on EGC mechanical properties and durability. It aims to identify challenges in developing EGC with practical applicability. While prior reviews have touched on EGC characteristics and research prospects, this review offers a more extensive analysis of the interplay among critical material traits, addressing a research gap. This study systematically categorizes and consolidates research findings, providing a reliable reference for experts in this field. The scarcity of information in EGC research hinders innovation and collaboration. Therefore, establishing a plan to access crucial materials from dependable sources is crucial. A scientometric approach, facilitated by appropriate software tools, can address these limitations. This study conducts a scientometric analysis of bibliographic data published in 2023 regarding EGC utilization. The analysis reveals prolific publication sources, authors, related citations, co-occurring keywords, contributing countries, and highly cited articles in the EGC research domain. Data from relevant documents, including abstracts, bibliographies, keywords, funding information, and citations, are retrieved using the Scopus search engine. The VOS viewer tool is then employed for data analysis. Statistical and graphical representations of countries and academics can facilitate idea exchange and research collaboration. This study combines scientometric analysis with a comprehensive literature review to underscore the significance of EGC and its future potential.

This article’s significance lies in addressing a critical issue in construction, i.e., the environmental impact of conventional cement-based materials. It aligns with global sustainability goals by highlighting Engineered Geopolymer Composites (EGCs) as a sustainable alternative. Given the extensive array of mix compositions available for EGCs, their intricate mechanical behavior under elevated temperatures, and the diverse heating methodologies employed in material testing, it becomes imperative to thoroughly examine the existing body of research concerning the temperature-dependent material attributes of EGCs. Additionally, it explores EGC advancements in mix design, engineering properties, and more, potentially leading to versatile and robust construction materials for various applications. While prior reviews have touched upon certain material traits and research prospects pertaining to EGC, this review delivers a more exhaustive examination of the interrelationships among pivotal material attributes to bridge the extant research gap. The article employs innovative research methods like scientometric analysis, setting a precedent for interdisciplinary approaches. It emphasizes cost-effective solutions by understanding factors influencing EGC properties enhancing accessibility for diverse projects. EGCs’ versatility, especially in geopolymer concrete, offers eco-friendly options for construction applications, supporting sustainable infrastructure development. Furthermore, the review facilitates knowledge dissemination and collaboration in the construction industry. In summary, this article has the potential to drive innovation, reduce environmental impact, and promote sustainable practices through EGC adoption, addressing crucial construction sector challenges.

The present study employs a scientometric analysis (Afgan and Bing, 2021; Amin et al., 2022; Huang et al., 2022) of bibliographic data to quantify its various properties. The scientometric analysis utilizes scientific mapping, a method researchers devised to examine bibliometric data (Markoulli et al., 2017; Amin et al., 2022). In light of the extensive literature within the less-explored research field, employing a reliable search engine is crucial. Scholarly consensus suggests two databases, specifically Scopus and Web of Science, as dependable sources to fulfill the research objectives (Afgan and Bing, 2021; Huang et al., 2022). Scopus is selected to gather bibliographic data related to EGC applications research. The search on Scopus resulted in relevant findings, with several filters applied to scrutinize irrelevant data. Figure 2 illustrates a comprehensive flowchart that depicts the methodical steps, including data retrieval, data analysis, and the application of various filters in the analysis.

Previous studies have utilized the same approach (Oraee et al., 2017; Jin et al., 2018; Park and Nagy, 2018). The Scopus database is stored in CSV format for further analysis using appropriate software. The research team utilized the open-source VOS viewer tool (version 1.6.18) to perform a quantitative analysis and scientific visualization of the collected data, which is also commonly used in this type of research (Zuo and Zhao, 2014; Darko et al., 2017; Ahmad et al., 2021). Therefore, the study’s objectives are achieved by utilizing a VOS viewer. The VOS viewer software is used to analyze the data collected from Scopus, and the CSV file is imported into the VOS viewer for further evaluation. A scientometric analysis is then conducted to examine widely used keywords, publication sources, authors with the most citations and articles, the contributions of different countries, and highly cited papers. The analysis generates maps that illustrate the features, their co-occurrences, and interconnectivity; relevant statistics are presented in tables. Different colors are assigned to specific elements in the map to differentiate between groups. Density mapping is achieved using colors such as rainbow, plasma, rainbow, and Viridis.

Unlike conventional concrete that uses cement, geopolymer employs mineral admixture (alkali-activated) as a binder to create a compact mass with an inert aggregate. Geopolymer offers various advantages over regular concrete, such as high early strength, resistance to high temperatures, and good chemical resistance in harsh environments. Engineered geopolymer composites (EGC) is chosen for several reasons, such as using sustainable construction materials to preserve the environment. This is due to the global concern over the use of Portland cement-based composites. Over the last two decades, extensive research has been conducted on various EGC properties, resulting in significant experimental test data. Comprehending the mechanical properties of EGC is a crucial step toward manufacturing significant EGC amounts having predictable characteristics. According to reviewed literature, researchers have conducted extensive studies on the properties of geopolymers over the past 20 years and found several techniques available for producing geopolymers with varying properties. Various properties of geopolymer paste (Phoo-ngernkham et al., 2013; Adak et al., 2014), mortar (Adak et al., 2014), and concrete (Hardjito et al., 2005) have been studied experimentally. Based on concrete density, EGC has two types: light and normal weight. The lightweight geopolymer concrete can be in foamed concrete (Al Bakri Abdullah et al., 2012) or other variations utilizing lightweight aggregate (Posi et al., 2013). Various curing methods were explored by researchers for EGC, such as oven heating, membrane curing, steam curing, water curing, hydrothermal curing, and room temperature. Of these methods, the most effective one is oven curing (Sofi et al., 2007a). The schematic diagram for the manufacturing of EGC is shown in Figure 11, as illustrated by Wang et al. (2023).

The difference in the micro-structure of conventional concrete and EGC has been depicted by Alanazi (2022), as shown in Figure 12. The geopolymer mixture SEM image (Figure 12B) displays a complex matrix microstructure of multiple phases. Consequently, these phases’ unique properties and interactions are expected to influence geopolymer concrete’s overall physical and mechanical characteristics significantly. Further discussion on this matter will be provided later. Regarding the geometric characteristics of the interfacial transition zone (ITZ), the microstructures adjacent to the larger limestone aggregate demonstrate no discernible variations compared to the matrix phase microstructure, suggesting the absence of visible voids surrounding the limestone particles. In contrast, the SEM image for the microstructure of the OPC mixture reveals the presence of significant voids or pores surrounding the ITZ, as depicted in Figure 12A. Other researchers have also reported similar findings (Mondal et al., 2009; Zhang et al., 2009; Khedmati et al., 2018). The magnified images in Figure 13 provide evidence of the bonding phenomenon occurring at the ITZ between aggregates and the geopolymer matrix. Notably, the presence of microcracks visible in the images, though their confirmation is still pending, might be ascribed to additional stress encountered during the polishing (surface smoothing) operation or the cementitious shrinkage transpiring during the curing process. Incorporating a low-density interfacial transition zone would harm the overall properties of ordinary Portland cement mixtures, decreasing their strength. The weakness observed in the ITZ of OPC mixtures is often linked to calcium hydroxide crystals and the accumulation of pores at the ITZ, which occur due to excess water at the aggregate surface (Zhang et al., 2009). These factors contribute to a compromised ITZ structure, reducing the overall performance of the OPC mixture. However, in the case of geopolymer paste and its associated ITZ, the absence of such calcium hydroxide crystals indicates a more favorable microstructural condition, potentially resulting in improved properties compared to OPC mixtures.

The durability of EGCs plays a vital in ensuring their long-term performance and reliability. However, specific standards for evaluating their durability are scarce due to the relatively recent emergence of geopolymer composites in cementitious materials. When assessing the durability of EGCs, similar to the standards used for conventional concrete evaluation (such as ASTM, AASHTO, and ACI), emphasis is placed on evaluating their transport properties, resistance to physical degradation, and chemical resistance (Li et al., 2021). Transport properties characterize the resistance of composites against the ingress of water, gas, and ions through cracks, pores, and air voids. These properties can be improved by incorporating appropriately dispersed nanomaterials in optimal quantities. Among these transport properties, water absorption holds particular significance as it directly influences the vulnerability of EGCs to various durability concerns. EGCs with lower water absorption demonstrate reduced susceptibility to multiple forms of degradation, given that water substantially contributes to deterioration mechanisms such as freeze/thaw damage, sulfate attack, alkali-aggregate reactions, carbonation, and rebar corrosion (Adak et al., 2015; Assaedi et al., 2016; Li and Shi, 2020). Water absorption in a material is affected by the transmission pathways and the characteristics of the contact surface. Hydrophilic materials generally demonstrate higher water absorption when evaluating materials with similar pore structures than hydrophobic materials (Li and Shi, 2020).

As far as the physical degradation is concerned, it typically includes abrasion (or erosion), weathering due to wet/dry cycling, and damage caused by freeze/thaw cycles. Understanding the fundamental mechanisms underlying physical damage in cementitious composites is an active area of ongoing research. However, it is widely agreed that the resistance to such cyclic degradations depends not only on the mechanical strength of the composite matrix but also on the characteristics of its pore structure. In the case of EGC, it is plausible to propose that the fluctuating temperatures may trigger the crystallization of temperature-sensitive phases found in fly ash, activators, and other additives. This crystallization process could generate pressure, potentially leading to the physical degradation of the EGC matrix. Additionally, it is conceivable that the alternating temperature conditions may cause the leaching of chemical ions, resulting in localized chemical attacks within the EGC (Xu and Shi, 2018; Xu and Shi, 2020). Moreover, EGCs in service conditions can encounter simultaneous deterioration from various sources, making them prone to physical and chemical assaults. Chemical degradation commonly observed in cementitious composites encompasses carbonation, sulfate attack, acid attack, and alkali-aggregate reactions. Conversely, failure mechanisms such as salt scaling and chloride-induced rebar corrosion entail combined chemical and physical deterioration processes (Ren et al., 2019; Xu and Shi, 2020). The formation process of geopolymers containing impurities, such as silico-aluminophosphate and alkali-aluminosilicate geopolymer, can be represented by considering the acidity and alkalinity activation conditions. These conditions are illustrated in Figure 18, as reported by Wang et al. (2019), showcasing the geopolymers’ step-by-step formation process. The presence of specific constituents in the precursor materials, referred to as “impurities,” which differ from aluminosilicates, can initiate reactions that deviate from the typical geo-polymeric processes. Consequently, when acidic or alkaline activators are utilized, distinct chemical compositions, levels of crystallinity, and phases are generated. Furthermore, beyond variations in pH conditions, significant disparities arise in the molecular structures of geopolymers, particularly in the chemical environment surrounding aluminum within the formed gels (Pacheco-Torgal et al., 2008; Yao et al., 2015; Wang et al., 2019).

Geopolymer concrete, which contains 70%–80% aggregate by mass and plasticizers, is manufactured using standard concrete production methods (Almutairi et al., 2021). Since then, researchers have conducted comprehensive studies on geopolymer concrete’s strength and durability characteristics. The pre-cast application of geopolymer technology is considered highly advanced, primarily due to its ability to handle delicate materials (Aleem and Arumairaj, 2012; Almutairi et al., 2021). Historically, EGC has been mainly used for sewer pipes and railway sleepers (Sharma et al., 2017; Gourley and Johnson, 2019). Nevertheless, it is now feasible to produce structural components such as beams, columns, and tunnel segments using geopolymer concrete (Farhan et al., 2018; Hassan et al., 2020). According to Almutairi et al. (2021), geopolymer concrete represents an excellent alternative to conventional concrete, even for the scenarios in which steel rebars are embedded as reinforcement. Geopolymer concrete has been shown to meet specifications in extreme environments, such as sulfate soils. Therefore, it can serve as a sustainable substitute for producing durable structures. EGC exhibits significant chloride resistance, which translates to minimal mutilation during winter especially upon application of salt for dissolving ice. The outstanding capability of EGC to resist chloride corrosion makes it a viable option for utilization in concrete structures exposed to saltwater environments, such as coastal bridges, underwater concrete supports, and piers (Zhao et al., 2020; Churata et al., 2022; Tanu and Unnikrishnan, 2023). According to Yang et al. (2008), geopolymer concrete manufactured using slag can attain strength if cured at room temperature. Numerous types of research have demonstrated that EGC may serve as highway infrastructure repair material (Yun and Choi, 2014). Due to the exceptional performance observed in its initial applications, efforts have been made to integrate EGC into respective authority specifications (Dave et al., 2020). According to Tayeh et al. (2020), highway pavement applications represent a specialized area where geopolymer concrete could bring about a significant transformation. Geopolymer concrete has emerged as a sustainable alternative to Portland cement concrete for various applications due to its remarkable durability and resistance to harsh environments, such as sulfate soils and chloride corrosion. Originally used for sewer pipes and railway sleepers, geopolymer concrete has now been extended to include structural elements such as beams and columns and can also serve as a repair material for highway infrastructure. Thus, geopolymer concrete has the potential to transform highway pavement applications. Figure 19 illustrates the summary of EGC applications, as mentioned in the above discussion.

The concrete industry is looking for sustainable alternatives to Portland cement, and one promising option is fly ash-based geopolymer concrete. Unlike traditional concrete, geopolymer concrete uses fly ash from coal-burning power stations as the binder, eliminating the need for Portland cement. Using fly ash-based geopolymer concrete has the potential to reduce global warming, as research has shown that the global warming potential of geopolymer concrete is between 26% and 45% lower compared to ordinary Portland cement concrete. Studies have shown that replacing traditional Portland cement concrete with geopolymer concrete, depending on the specific precursor and activator used, can lead to a reduction in embodied carbon of up to 80% (Tayeh et al., 2021). However, other ecological impact factors need to be considered as well. Life cycle assessment of geopolymers reveals that, compared to OPC concrete, geopolymer concrete has a reduced impact on global warming (Garces et al., 2021). Additional LCAs of geopolymers have also suggested that these materials can serve as sustainable substitutes. Further gains in sustainability could be realized by adopting alternative activators and precursors that are readily available locally (Salas et al., 2018; Dal Pozzo et al., 2019; Bumanis et al., 2020). Therefore, the concrete industry must explore alternative methods to make geopolymer concrete more environmentally friendly while maintaining its benefits as a sustainable alternative to traditional concrete. Geopolymer concrete is often produced using waste materials from industrial and agricultural processes as precursors. This makes it an eco-friendly option for managing bulk waste generated by several industries (Juenger et al., 2011; Palomo et al., 2015; Mehta and Siddique, 2016). Furthermore, the geopolymers’ sustainability can be enhanced using laterite soil as precursors. Therefore, using geopolymers as a replacement for Portland cement composites can substantially decrease greenhouse gas emissions, utilization of raw materials, and efficient waste management (Davidovits, 2008; Yang et al., 2013). Therefore, it can be concluded that geopolymer binders without using cement are a highly promising eco-friendly construction material. Figure 20 (Mishra et al., 2022) shows that these geopolymer composites can be produced using industrial wastes, promoting sustainable development and benefiting the environment.

This comprehensive bibliographic investigation thoroughly explores the dynamic and evolving domain of Engineered Geopolymer Composites (EGCs). By conducting an in-depth analysis of pertinent literature, numerous significant themes and trends have emerged, illuminating the present understanding of this specialized field. The review has yielded valuable insights into the manifold applications, properties, and challenges linked to EGCs, underscoring their capacity to bring about revolutionary changes across diverse industries. The scientific community has proposed bibliometric metrics that use statistical analysis techniques, such as scientometric analysis, to evaluate publications based on scientific conclusions. Such a review-based study can identify trends in the literature on EGC that benefit young scholars and researchers. The conclusions drawn are as follows:

• Many manufacturing methodologies have been devised to attain specific properties in geopolymers, with investigations encompassing geopolymer paste, mortar, and concrete. EGC can be classified into either lightweight or normal weight categories, including variants such as foamed concrete and the incorporation of lightweight aggregates. Extensive research has been dedicated to exploring various curing techniques, among which oven curing has emerged as the most efficient approach.

Engineered Geopolymer Composites (EGCs) represent a rapidly advancing and burgeoning area of research with substantial intellectual significance and far-reaching implications. However, there is a distinct need for additional foundational investigations to comprehensively explore and exploit the full potential of this environmentally sustainable cementitious composite. Furthermore, the current study highlights a lack of precise connections between different aspects of literature in conventional research studies on EGC. To address this issue, the authors conducted a systematic review that maps bibliographic data and provides statistical analysis. The review identifies frequently used keywords, the countries and sources contributing the most relevant articles, and the most credible authors in the EGC research domain. In the current study, an assessment of keywords shows that EGC has been studied as a sustainable and durable material. The analysis of highly contributing countries in the research domain is based on citation-based linkages in the literature. This analysis could help researchers to collaborate and advance research in this field. The study also employs scientometric analysis to evaluate keywords and interlinked literature, highlighting future perspectives in EGC research. Based on the current literature, it has been established that geopolymer concrete holds significant potential for a range of construction applications. However, additional research is required to address the following areas and facilitate greater utilization of geopolymers:

• A detailed investigation should be made to explore the impact of incorporating different alkali-activated mineral admixtures on geopolymer concrete properties, like compressive, splitting-tensile, and flexural strengths.