Eco-friendly agro-waste based geopolymer-concrete: a systematic review

Abstract

Numerous scientific studies have been conducted, and a wide range of new inorganic geopolymer composite applications have emerged as a result. This innovative material can be made from agricultural waste sources rich in aluminosilicate, which provides best substitute for traditional cement in terms of both quality and cost. This paper presents the state-of-the-art review of deploying agro-wastes as precursor for geopolymer concrete with the view to aggregating the research studies of using agro waste ash-based geopolymer as the most auspicious, durable, inexpensive, user-friendly, and eco-beneficial construction materials for the long-term use. This paper thoroughly examines the rheological, workability, chemistry, and mechanical characteristics of agro-waste ash-based geopolymer concrete with emphasis on sugarcane bagasse and banana peels ash. Sugarcane and green bananas (matooke) play vital roles in East African agriculture, economy and food security. The effects micro-structures, curing conditions, molarity of metallic alkalis, proportioning of alkaline-binder ratio, aggregates content and size fractions effects on the behavior of geopolymer concrete were critically assessed. The study highlighted the abundance of these agro products which serve as staple food in East African region, therefore, it becomes imperative to recycle its waste to produce durable concrete by way of waste management strategy. As a vital component of the readily available building materials, they have a crucial role to play in providing the construction sector with a sustainable outlook while concluding that agro-wastes are potential material that could be a game changer for geopolymer concrete, a number of research gaps that worthy for further study were identified. The findings of this review further demonstrates that agro-waste derivatives when used as binder materials in geopolymer concrete can be a viable and sustainable alternative to conventional cementitious materials.

1 Introduction

Cement is an indispensable constituent for the construction of civil infrastructure. Cement manufacture with the use of fossil fuels produce around 7–10% of the world's CO₂ [1]. However, it is crucial to lessen cement usage so as to reduce emission of greenhouse gas. To this purpose, industrial and agricultural byproducts including sugarcane bagasse ash, sawdust ash, fly ash, banana peel ash, cassava peel ash, kaolin clay, rice husk ash, and metakaolin may be used to substitute cement in the making of concrete [2, 3]. Sustainable advantages of the use of agro-residues in concrete, along with their economic benefit and environmental friendliness compared to Portland cement, has garnered attention from both the research and construction sectors [4]. Reusing solid agricultural by-products residue, which are often dumped in sanitary landfills or utilized as biofuel to substitute Portland cement in the manufacturing of concrete, is a suitable and economical way to address ecological and energy usage problems, claim Jiang et al. [5].

The development of economical building materials for self-sufficient housing, particularly in developing nations, and improved waste management depend on the use of agro-waste in concrete [6]. However, the majority of the produced agricultural leftovers are either burnt on-site by farmers, which results in carbon dioxide emissions that degrade the environment, left behind and stored in landfills, posing a number of environmental, technical, and social problems. Therefore, turning agricultural waste into eco-efficient and low-energy construction materials could be an effective way to help nature, the environment, and future generations [7, 8]. Several agro byproducts derivatives have been adapted as basis ingredients for development of sustainable geopolymer concrete materials such as rice-husk-ash which is a byproduct from rice milling process and possesses about 2% of Potassium oxide, 5% carbon, and 90% amorphous silica [9, 10]. Cassava peel ash (CPA) obtained from cassava agricultural processing factory which is treated in muffle furnace and can possess pozzolanic reactivity due to combination of alumina, ferric and silica in the ash samples. CPA can be used to improve the weak soils’ engineering properties and also source materials for geopolymer composites according to the findings of Chimmaobi et al. [11].

Moreso, utilization of Bambara groundnut shell ash obtained from the threshing and separation of the shells from the Bambara nuts which is abundance in West African region before they are calcined and they were observed to have moderate aluminosilicate content which are beneficiary to the rheological and mechanical performance of green concrete and for soil stabilization purposes [12]. Sugarcane Bagasse ash (SCBA) is a biomass left-over obtained by combustion of sugar manufacturing cellulose-based fibrous byproducts and it is primarily composed of inorganic materials such as alumina, silica, iron oxide, and calcium oxide which indicated that it possesses pozzolanic properties. SCBA can also be used to reinforce the strength performance of expansive soil and for geopolymer concrete development [12]. Furthermore, Banana peel ash (BPA) is obtained from the calcination of the thin outer skin of the banana fruit rich in cellulose and the ash contains aluminosilicates, potassium and sodium oxides. The ash samples were employed as admixtures to increase concrete’s setting time and also as source precursor to boost the green geopolymer concrete’s durability and mechanical behavior [13].

Researchers, concrete technologists, and scientists have been driven by all these adverse effects to look for alternative building materials that will help save the earth's finite natural resources while also being user- and environmentally-friendly, long-lasting, and cost-effective. These are the underlying reasons why so many researchers are drawn to cutting-edge geopolymer technology and geopolymer composites [14, 15]. The systematic disposal of agricultural waste materials may be solved by synthesizing geopolymers with low energy, reduced temperature, low cost, and by employing a variety of abundant wastes as either supplementary cementitious materials (SCM) or precursors [16]. An innovative and green concrete called geopolymer concrete hardens by combining recyclable aluminosilicate with alkaline activating solvents rather than cement. It offers new uses for waste items and industrial byproducts while enabling a decrease in the need for cement manufacture [17]. It is anticipated that employing geopolymer concrete might result in energy savings of up to 43% and a 9–80% decrease in emissions of CO₂ when likened to cement-based concrete. The complexity of estimating emissions, which depends on a variety of elements including regional circumstances, transportation, and the mix design itself, is the cause of this large range [18, 19].

Additionally, geopolymer concrete offers superior endurance properties than conventional concrete, including resistance to carbonation, freeze–thaw cycles, high temperatures, and chloride; it has also shown to possess improved mechanical strength behavior [20, 21]. The numerous investigations on geopolymer concrete development and prospects that have been done by various researchers are summarized in this review study. They are divided into several areas, such as the raw materials used to create geopolymer concrete, the design of components chosen, the variables affecting its engineering behavior and the impact of alkali activators’ molarity. A thorough evaluation of the literature on sustainable eco-efficient construction materials through geopolymer concrete achieved from agricultural waste proceeds was conducted to uncover the potentials and room for improvement of this innovative materials. There is enough information in the literature about geopolymer concrete developed from several agro-industrial waste derived precursors and metallic alkaline materials. It has been shown that these aluminosilicate materials have a noteworthy impact on the strength qualities of geopolymer concrete. Nevertheless, there is dearth of information on the utilization of derivatives from agro byproducts such as banana peel ash and sugarcane bagasse ash as precursor materials to create high-strength concrete through the use of NaOH-based alkaline medium [22, 23].

In subsequent section of this review, various agro waste source materials utilized for the development of green geopolymer concrete with emphasis on banana peel ash and sugar cane bagasse ash materials were considered. This is followed by the methodological section which presents the detailed procedure involved in the source of relevant scholarly literature works reviewed. The next section involves the investigation of the geopolymer concrete mechanism, chain reaction processes and polymeric structure of the polyhedral gel framework. Moreover, in the following section, the engineering behavior assessment of geopolymer concrete were reviewed with emphasis on the proportion ratio of the constituents, particles size and aggregate content, alkali activator types and molarity effects, micro structural assessments, curing conditions and mechanical properties. The succeeding section further presents the identified research gaps from the reviewed literature and finally in the last section, the conclusion is drawn from the investigative study.

2 Agro-waste ash utilization for sustainable geopolymer concrete development

Over 50% of the agricultural biomass produced worldwide is composed of crop leftover. With the long-term objective of reducing carbon emissions, biomass, a renewable energy source, is increasingly replacing the traditional coal-based thermal power plants as a source of power [24, 25]. Due to its large carbon footprint, modern cement's considerably large use for the manufacturing of concrete has similarly contributed to several ecological complications globally. This may be reduced by using agro-industrial wastes like bagasse and banana (matooke) peels, whose disposal is a severe problem in developing nations like Uganda [26, 27]. Agribusiness waste is often disposed of in landfills or burned openly, which may contaminate the air. This waste material may be used to improve the cement's quality [28]. The processing steps of agro-wastes such as SCBA and BPA sourced locally combined with Na₂SiO₃/NaOH alkaline activators to achieve sustainable geopolymer concrete materials is presented in Fig. 1.

Fig. 1

Procedures and chemical reaction phases involved in geopolymer concrete production from the mixture of alkaline activators and agro-waste ash such as SCBA and BPA [29]

Typically, agricultural waste is burned outdoors or dumped in landfills, which may pollute the environment. Bananas are vital food crops for greater number of people in the subtropical region of Africa with about 20 million tons produced in Eastern part of African continent including counties such as Uganda, Rwanda, Burundi and Kenya. Also, the perennial nature of banana compared to other staple food crops makes it least impacted by social instability and environmental factors. The consumption of these banana fruits has resulted to the generation of the waste peels which contribute to significant agricultural waste. Table 1 presents an extensive summary of some agro waste ashes sourced from various locations of the world, their potentials and utilization to eliminate environmental challenges, and the amount of the byproducts engendered in tons per annum. The details derived from the findings show the abundance of these agro waste materials and their relative advantages when put to good use which would contribute to waste management and drive towards waste to wealth initiative [30].

Table 1 Estimated measures of some selected Agro wastes Biomass and their various Applications

With a projected yearly production of 8.45 million tons, or 15% of the total global output of bananas, bananas are the most significant food crop in Uganda [49]. Over seven million people in Uganda, particularly 65% of the urban population, rely on the crop as their main food source. The most significant nutriment and economic produce for agriculturalists in Uganda, where daily consumption of matooke is 0.7 kg [50]. Almost all culinary bananas have seedless fruits, despite the fact that the wild variety have fruits with many huge, hard seeds. Bananas may be either dessert bananas (yellow and completely ripe when eaten) or cooking bananas (green) [51]. Therefore, it is important to investigate agricultural byproducts that may be converted into useful and important goods like adsorbents and aluminosilicate materials. The peel is used as a natural cure for a variety of skin issues, including allergies and skin irritations. The garbage from banana peels is often dumped in municipal landfills, which adds to the already present environmental issues [52].

Another major crop that is grown widely in African region that belongs to Poaceae grass family is sugarcane, which is cultivated in tropical and subtropical climates, totaling about 1.9 billion tonnes in 2022 [53]. Uganda's sugar cane output climbed at an average yearly rate of roughly 3.76%, from 1.72 million tons in 1971 to 5.78 million tons in 2022. Indecorous management of these trash materials adds to global warming, fosters an unsafe environment, and provides a perfect habitat for pests and disease vectors [54]. Sugarcane is the primary resource used in the manufacturing of sugar while the leftover pulp after the sugarcane juice is processed is known as bagasse. Due to its direct dumping and accumulation of the waste in open areas, sugarcane bagasse pollutes the atmosphere and hence it is necessary to recycle the waste materials [55]. In various regions of the world, sugarcane bagasse ash has recently undergone testing for usage as cement replacement material and to stabilize expansive soils through pozzolanic activity [56]. The diagrammatical presentation of the banana and sugarcane plantations can be shown in Fig. 2.

Fig. 2

Typical Banana Plantation (a), Sugarcane Plantation (b) and Bagasse waste (c)

The waste derivatives ash from the cogeneration energy systems that have previously been built in sugar mills is known as sugarcane bagasse ash. An enormous quantity of bagasse ash is produced as a byproduct when bagasse is burnt to produce power [57]. The biggest producers, Brazil and India, discards more than 700 million tonnes of bagasse ash per annum. Noteworthy, according to a previous research, cogeneration with the aid of bagasse produced a staggering 11,907 MW of power in Brazil recently [58].

Likewise, East Africa also possess variety of cogeneration facilities that can guarantee the accessibility of bagasse ash byproducts to be utilized as a natural resource for geopolymer concrete and as a blending component in the manufacture of cement. Given that both bagasse and sugarcane straw production are reliant on one another, their availability trends will be similar [59, 60]. Table 2 displays the chemical composition of various agro-waste ash used as supplementary cementitious materials as obtained from prior pertinent research works. When compared to the results of previous studies, the findings show modest changes in the primary chemical components of alumina, silica, and calcium oxide, with the range values of 2–15%, 71–85% and 1.1–4% respectively for SCBA and RHA respectively [61]. The elemental composition results revealed that ABA, WSA and SDA exhibited good pozzolanic behavior with SiO₂ ranging from 64 to 78%, CaO ranging from 1.4–8.6%, Fe₂O₃ ranging from 0.8 to 4.1%, Al₂O₃ ranging from 0.8 to 6.3%, MgO ranging from 0.44–3.72% and K₂O ranging from 2.86–9.92%. The results for CSA depicted 37.99% for SiO₂, 15.48% for Fe₂O₃, 24.15% for Al₂O₃, and 4.98% for CaO. Moreover, the outcomes for PLA signified a high CaO and P₂O₅ contents at 65.17% and 17.43% respectively; it also possess low SiO₂, Al₂O₃, and Fe₂O₃ contents at 3.05%, 0.3% and 0.56% respectively.

Table 2 Chemical Composition of some selected agro waste derivatives

Additionally, the results presented showed a range value of 2.3–9%, 15–56%, and 0.2–16% for calcium oxide, silica and alumina respectively. Also, the potassium oxides and ferrite compositions in BPA produced averaged results of 55% and 5% respectively. When mixed to produce sustainable, eco-efficient, and long-lasting concrete materials, the produced elemental oxide components for the studied agro-wastes show impactful ternary blend activity. Generally, according to the ASTM C618-08a standards for natural pozzolans, the agro waste derivatives’ bulk composition of SiO₂, Al₂O₃, and Fe₂O₃ adds up to a mean value of 85% [62, 63].

3 Methodology

In order to provide environmentally friendly and durable building materials, this detailed review concentrates on evaluating the prospects of agro waste derivatives (ash), like bagasse ash and banana peel ash, for the creation of geopolymer concrete [72]. Taking into account the aforementioned factors, a thorough analysis of pertinent and related published literature obtained from scholarly research database and indexing systems including PubMed, Science Direct, Scopus, and Web of Science [73, 74]. The extracted articles’ abstracts and titles of the were evaluated for eligibility and retrieval criteria, taking into consideration a number of parameters that influence the mechanical and durability behavior of agro-waste ash-based geopolymer concrete, such as specific gravity, elemental compositions, morphological evaluations, molarity of the metallic alkali activator, and used mix designs. Agro-waste ash, bagasse ash, banana peel ash, geopolymer concrete, and alkali activators are useful keywords to use [75]. Furthermore, following screening exercises on alkali activation of agricultural waste ash to produce durable, eco-friendly concrete across a thirty-year period, from 1992 to 2022, the literature works collected were constrained to 795 relevant articles, as shown in Fig. 3.

Fig. 3

Relevant Literatures Studies to be reviewed

The capabilities and uses of agro-waste ash in geopolymer concrete, in addition to the performance patterns with various metallic alkalis and molarity concentrations, were examined in the chosen research publications [58]. Additionally, the information from the literary works was skillfully structured into categories to evaluate the agrowaste-based alkali-activated geopolymer concrete, such as physical characteristics and elemental oxides composition assessments of the aluminosilicate precursors under study, evaluation of strength and durability behavior considering various sorts of alkalis, levels of concentration, and morphological assessments of the geopolymer concrete as shown in the methodology flowchart in Fig. 4 [2, 76].

Fig. 4

Review methodology flowchart

4 Mechanism of geopolymer concrete development

Geopolymer concrete is a type of cementless concrete that is made from agro waste derivatives such as SCBA, BPA and other materials that contain aluminosilicate. Instead of traditional Portland cement, geopolymer concrete uses an alkali-activated binder to create a chemical reaction known as geopolymerization that forms a strong and durable material [57]. The reaction involves aluminosilicate precursor dissolution in the alkaline medium, which is accompanied by the establishment of a three-dimensional network of covalent bonds between the dissolved species. The process of making geopolymer concrete involves mixing the agro by-products with metallic alkaline, such as NaOH, KOH, Na₂SiO₃, or K₂SiO₃, and then curing the mixture at a specific temperature for a set amount of time [77]. The resulting material has similar properties to traditional concrete, like durability and mechanical behavior, but with the added benefit of being more environmentally friendly due to its lower carbon footprint. In addition to having high mechanical capabilities, geopolymer materials also possess a number of other superior qualities including fire and corrosion resistance [78, 79].

The mechanism of geopolymer concrete development involves the following steps:

• Selection of raw materials: The first step in developing geopolymer concrete is to select suitable raw materials. The aluminosilicate precursor material such as SCBA and BPA which is typically sourced from agro waste streams can be used. The alkaline activator can be a combination of Na₂SiO₃ and NaOH [80].

• Mixing: The precursor and metallic alkaline are mixed together to form a slurry. The ratio of these materials is critical to the formation of a stable geopolymer. The slurry is typically mixed for several minutes to ensure that the materials are well combined [81].

• Casting: Once the slurry is mixed, it is poured into molds or forms and allowed to set. The setting time for geopolymer concrete depends on numerous influences, such as the nature and concentration of the activator used, the kind of geopolymer precursor, and humidity. In general, the setting time of geopolymer concrete is faster compared with conventional concrete due to the faster reaction kinetics of the geopolymerization process [82].

• Curing: Curing is the process of maintaining a suitable temperature and humidity environment to allow the geopolymerization reaction to proceed and the geopolymer binder to form a strong, durable, and stable structure. After the geopolymer concrete has set, it is cured in a moist environment to promote the development of strength. The curing process can take several days to several weeks, depending on the desired concrete strength [83].

• Testing: Once the geopolymer concrete has been cured, it is tested to ensure that it meets the required strength and durability specifications.

4.1 Crystallography, composition, and particle size on the reactivity of biomass ashes

Biomass ashes with a higher amorphous content tend to exhibit greater reactivity. Amorphous phases provide more reactive sites for the geopolymerization reaction to occur, leading to improved strength development [84]. The crystallographic properties of the ash particles can influence their reactivity in geopolymer concrete. Ashes with higher amorphous content tend to exhibit greater reactivity compared to those with predominantly crystalline structures. Amorphous phases in the ash, such as vitreous or glassy components, are highly reactive and contribute to the geopolymerization process [85]. These amorphous phases contain silica and alumina, which are essential for geopolymer formation. Crystalline phases, such as quartz or mullite, are less reactive and may act as inert fillers. The presence of crystalline phases can reduce the overall reactivity of the ash by limiting the available reactive sites [86].

The composition of biomass ashes plays a crucial role in their reactivity. Different biomass sources, such as rice husk, sugarcane bagasse, or wood, have varying chemical compositions. Ashes rich in silica (SiO₂) and alumina (Al₂O₃) generally exhibit better reactivity because they provide the necessary precursors contributing to improved geopolymerization and strength development [87]. Additionally, the presence of alkali and alkaline earth oxides (e.g., Na₂O, K₂O, CaO) in the ash composition can enhance the reactivity by serving as activators or catalysts in the geopolymerization process. These oxides act as activators or catalysts in the geopolymerization process, promoting the formation of the geopolymeric gel. They contribute to the alkalinity of the system, facilitating the dissolution of silica and alumina and enhancing reactivity. Higher concentrations of these oxides promote a more alkaline environment, which favors geopolymer formation [86].

The particle size distribution of biomass ashes affects their reactivity in geopolymer concrete. Finer particles provide a larger surface area for chemical reactions to occur, allowing for more contact with the alkaline activator solution and facilitating the geopolymerization to result in higher strength development. Smaller particle sizes also promote better packing of particles, leading to improved mechanical properties [88]. Conversely, larger particles tend to have lower reactivity and may not fully participate in the geopolymerization reaction, potentially reducing the overall strength of the concrete. Particle size distribution influences packing and porosity in geopolymer concrete. Finer particles can enhance packing density, leading to improved mechanical properties. Smaller particles fill voids more efficiently and create a denser microstructure, resulting in higher strength [89].

To optimize the reactivity of biomass ashes in geopolymer concrete, it is crucial to consider a combination of factors, including maximizing the amorphous content, ensuring a suitable composition with sufficient silica and alumina content, and controlling the particle size distribution to maximize the surface area available for reactions [90]. Experimental testing and characterization are essential for determining the most effective combination of crystallography, composition, and particle size to achieve the desired performance in geopolymer concrete. Furthermore, it's important to note that the specific effects of crystallography, composition, and particle size can vary depending on the overall mix design, curing conditions, and other parameters. Therefore, comprehensive testing and optimization are necessary to determine the optimal combination of these factors for maximizing the reactivity of biomass ashes in geopolymer concrete [80].

4.2 Effects of NaOH and KOH activator agent on geopolymerization

NaOH and KOH are the most regularly used activator agents in geopolymerization. These alkali solutions play a pivotal part in the geopolymerization reaction, as they afford the alkaline medium necessary for the dissolution of the SCBA, BPA or other agro waste derived aluminosilicate material and the subsequent formation of the geopolymer binder [91]. The effect of NaOH and KOH on geopolymerization is dependent on several factors, including the molarity and sort of alkali used, the curing condition and duration, and the type of aluminosilicate material used. Generally speaking, NaOH and KOH have similar effects on the geopolymerization reaction, but there are some differences in their properties that can impact the final product [92].

One of the primary effects of NaOH and KOH on geopolymerization is the level of precursor material’s dissolution. NaOH tends to be more effective in dissolving the aluminosilicate material than KOH, which can lead to faster reaction times and higher degrees of geopolymerization. However, KOH is more effective in forming a more cross-linked structure, resulting in a denser and stronger geopolymer binder [93]. Another impact of KOH and NaOH on geopolymerization is the degree of alkalinity of the solution. NaOH is a stronger alkali than KOH and can result in a more alkaline solution, which can lead to higher degrees of geopolymerization and increased strength. However, the high alkalinity can also lead to a more brittle material and increased susceptibility to cracking. In general, the choice of NaOH or KOH as the activator agent in geopolymerization rest on the specific characteristics desired in the geopolymer concrete. The concentration and type of alkali used, as well as other factors such as extent and temperature of curing, can also impact the geopolymer concrete’s final properties [94].

4.3 The chemistry of geopolymerization

Joseph Davidovits discovered in 1978 that the procedure known as "Geopolymerization" might be used to create substitute eco-efficient binders [95]. Owing to this heat-releasing chemical reaction between the hydroxide and silicate of alkalis in a highly alkaline media at ambient or elevated temperature, merely under atmospheric pressure, he created a unique kind of inorganic aluminosilicate oxide with improved mechanical and durability performance termed as a geopolymer [96, 97]. To put it another way, geopolymerization occurs by alkaline activation, or dissolving at high pH under more alkaline circumstances and only utilizing atmospheric pressure, and at very low temperatures, from room temperature to slightly increased temperatures often below 100 °C or 150 °C [98].

Because of the hydro-thermal setup requirements, the breakdown of aluminosilicate precursor materials in alkali solutions results in the synthesis of three different kinds of geopolymers, namely, silicon-oxo-aluminate $\left( { - Si - O - Al - } \right)_{n}\left( { - Si - O - Al - } \right)_{n}$, poly sialate monomer $\left( { - Si - O - Al - O - } \right)_{n}\left( { - Si - O - Al - O - } \right)_{n}$, and poly sialate siloxo $\left( { - Si - O - Al - O - Si - O - } \right)_{n}\left( { - Si - O - Al - O - Si - O - } \right)_{n}$. Poly sialates are a type of inorganic polymer that contain silicate (SiO₄) and aluminate (AlO₄) tetrahedral units linked together by bridging oxygen atoms [99]. They are formed through the hydrolysis and condensation of alkoxysilanes and aluminates in the presence of an alkaline agent or catalyst [100, 101]. Free silicon dioxide and aluminum oxide tetrahedral units join by exchanging oxygen atoms during dissolution and the mixture’s workability is caused by the water released during this operation as stated chemically in Eq. 1 [102].

$$Si_{2} O.Al_{2} O_{5} + H_{2} O + OH^{ - } \to Si\left( {OH} \right)_{4} + Al\left( {OH^{ - 4} } \right) \to \left( { - Si - O - Al - O - } \right)_{n} + 4H_{2} OSi_{2} O.Al_{2} O_{5} + H_{2} O + OH^{ - } \to Si\left( {OH} \right)_{4} + Al\left( {OH^{ - 4} } \right) \to \left( { - Si - O - Al - O - } \right)_{n} + 4H_{2} O$$

(1)

Chemically, poly (sialates) may be represented by using the tetrahedral structure and the empiric’s formula in Eq. 2 [103].

$$C_{j} \left\{ { - \left( {SiO_{2} } \right)_{K} - AlO_{2} } \right\}_{j}C_{j} \left\{ { - \left( {SiO_{2} } \right)_{K} - AlO_{2} } \right\}_{j}$$

(2)

In this formula, K stands for the silica to alumina ratio, C for monovalent alkali cations like sodium (Na +) or potassium (K⁺), j for polymerization or polycondensation degree, and hyphen symbols for bonds. AlO₄ and SiO₄ tetrahedral structure units of the precursor aluminosilicate found in agricultural waste ash bind to one another by sharing oxygen atoms. Li⁺, Ca²⁺, K⁺, Ba²⁺, Na⁺, H₃O⁺, and NH³⁺ are positive ions that counteract the negative charge of alumina [104, 105]. Moreover, it is hypothesized that the dimer and trimer oligomers that make up the particular unit 3D structures with macro-molecular structures are responsible for carrying out the fusions [106]. Under alkaline circumstances, the alumino-silicates change to become very reactive aluminosilicates that polycondense with one another to create a three-dimensional structure, but under acidic conditions, they do not interact or are destroyed [107, 108]. Hypothetical monomers could be the source of iron polycondensation, which results in ortho-sialate and ortho (sialate siloxo). Presently, the only polymeric compounds used for geopolymers are sodium-poly (sialate), potassium-poly (sialate), sodium-poly (sialate-siloxo), and potassium-poly (sialate-siloxo) [109]. The geopolymerization reaction processes are shown in Fig. 5.

Fig. 5

Diagram showing Geopolymerization reaction processes [86]

Aluminosilicate substances that have been mixed in a metallic alkali medium at ambient or high temperature and geopolymerized create a 3D silicoaluminate structure and an amorphous phase [110]. The development of free silica-alumina tetrahedron unit outcomes from the dissolving of precursor materials in the condensed alkali-activator solution. In order to produce the geopolymer gel phase, materials must be transferred, solidified or gelled, and alumina and silica hydroxyl must undergo a condensation process [111, 112]. Due to the hydrolysis reaction, water is consequently discharged from the structure. Then, when the gel phase solidifies, it condenses to create a 3D grid of silicoaluminate that eventually turn into a geopolymer [77]. Alumina and silica condense as a consequence of the hydrolysis of dissolved units Al³⁺ and Si⁴⁺ during the geopolymerization chemistry, which is how precisely geopolymers are created [113]. The silicon-oxo-aluminate, poly sialate monomer and poly sialate siloxo polymeric structure is presented in Fig. 6.

Fig. 6

Polymeric Structure of silicon-oxo-aluminate, poly sialate monomer and poly sialate siloxo [88]

To understand the processes involved in the complex mentioned reaction kinetics, a model chemical must be employed. The distinguishing characteristics of a geopolymer is an alkaline aluminum silicone gel in which the aluminum and silicone ions are linked in a 3D polyhedral gel framework that is reasonably insoluble in water [114, 115]. Using three successive stages such as dissolution-coagulation, coagulation-condensation, and condensation-crystallization, Hanjitsuwan et al. [116] offered a thorough explanation of the geopolymerization process. The alumina-silica structure is weakened by OH⁻ from the alkaline activator, which initiates the activity of geopolymerization. The quantity of silica and alumina that are dissolved in the solution controls this process. Aluminosilicate oligomers are created by interplay between the tiny dissolved species and any silicate that was pr eviously given by the activating solution [117].

The geopolymerization process results in the development of the geopolymer gel binder phase, an unorganized alumino-silicate gel phase of alkali. Inert solid source material particles may be detected in this phase, and the gel's pore structure contains the water that is utilized to mix the precursors [118]. Contrarily, unlike in the case of calcium-silicate-hydrate (C–S–H) gel, water doesn’t constitute an essential component of a geopolymer binder’s chemical structure [116]. The basic structure of the gel is closely linked to triple 3D arrangements of silicate and aluminum tetrahedron, and is counterbalanced by cations of metallic alkali supplied by the activator. This negative charge is caused by Al³⁺ four-fold synchronization in any or all of the joining oxygen elements in every aluminum tetrahedron [119]. On an atomic to nanoscale, the geopolymer gel has structural resemblances with zeolites. This is sometimes carried out to the extent that the formation of the nano-crystallites within the geopolymer gel is apparent, particularly when there is an abundance of water, a high synthesizing temperature, and a low Si to Al proportion [120]. The geopolymer chain reaction products are shown in Fig. 7.

Fig. 7

Chain reactions in geopolymer concrete production [94]

5 Engineering properties of geopolymer concrete

Geopolymer concrete has been found to exhibit several desirable engineering properties, which make it an auspicious substitute to conventional concrete and are influenced by the source aluminosilicate materials or precursors in the form of SCBA and BPA, the alkali-activated solutions utilized, mixing methods, the type and measure of aggregates used and the curing procedure [121, 122]. The alkaline solutions used to make geopolymer concrete have a significant impact on its strength characteristics. The highly alkaline environment will enhance hydrolysis of the source materials to achieve improved engineering behavior. However, the geopolymerization process may be impacted and the strength may weaken if OH⁻ ions are allowed to freely move throughout the matrix [123]. For the purpose of dissolving Al and Si oxides, NaOH, Na₂SiO₃, KOH, and K₂SiO₃ are often used in geopolymer concrete. In comparison to potassium solutions, NaOH solutions have a greater solubility for the ions Si⁴⁺ and Al³⁺ [124]. The typical source material for geopolymer concrete is sodium hydroxide. A combination of NaOH and Na₂SiO₃ is utilized as a geopolymer concrete activator solution due to the material's high cost [125]. Some engineering properties of geopolymer concrete are as follows;

• High strength: Geopolymer concrete can exhibit high compressive and flexural strength, often exceeding that of traditional Portland cement concrete. The utilization of fly ash, SCBA, BPA and other agro waste materials in geopolymer concrete can also result in improved strength and durability according to the research findings of Akbar et al. [126]

• Durability: Geopolymer concrete has been observed to exhibit improved durability, notably resistance to penetration of chloride, base or acid attack and alkali-silica reaction (ASR). This is in consonance with the findings of Ogbonna et al. [21].

• Fire resistance: Geopolymer concrete has been revealed to possess superior fire resistance compared to traditional Portland cement concrete, due to its chemical composition and structure.

• Reduced environmental impact: Geopolymer concrete can have a lower environmental impact compared to traditional Portland cement concrete, as it utilizes waste materials and requires less energy to produce, resulting in reduced carbon dioxide emissions [127].

• Rapid strength development: Geopolymer concrete can develop high strength rapidly, which can lead to shorter construction times.

• Shrinkage: Geopolymer concrete has been shown to exhibit reduced drying shrinkage compared to traditional Portland cement concrete.

5.1 Fresh properties of geopolymer

Fresh properties of geopolymer concrete refer to the characteristics of the concrete when it is first mixed and before it sets. At the fresh state, geopolymer concrete exhibits certain behaviors that are different from those of traditional concrete. some key behaviors of geopolymer concrete at the fresh state are as follows;

5.1.1 Workability property

This refers to its ability to be mixed, transported, placed, and compacted into its final shape without segregation or bleeding. The SCBA and BPA geopolymer concrete’s workability characteristics can be impacted by various factors, including the ingredients properties, the mix proportions, and the mixing method [128]. Several factors that impact workability characteristics of geopolymer concrete are elucidated as follows;

5.1.1.1 The use of superplasticizers

The agro waste based geopolymer concrete’s workability behavior can be enhanced by using superplasticizers, which are chemical additives that can reduce the viscosity of the mix and increase its flowability. This can improve the workability and make it easier to place and compact the concrete [129].

5.1.1.2 Particle size and distribution

The gradation of the materials used in geopolymer concrete can have an impact on its workability. Fine particles can increase the viscosity of the mix, while coarser particles can decrease it. Proper grading of the materials can help optimize the workability.

5.1.1.3 Mixing method

The mixing method used for geopolymer concrete can affect its workability. It is recommended to use a high-intensity mixer to ensure uniform distribution of the materials and improve workability.

5.1.1.4 Water content

The water content of geopolymer concrete can affect its workability. A high-water content can increase the flowability of the mix, but it can also reduce the strength of the final concrete. It is important to optimize the water content to achieve the desired workability without affecting the concrete’s strength behavior. Overall, geopolymer concrete can have similar workability properties to traditional concrete, and its workability can be optimized by adjusting the mix proportions and using proper mixing techniques [130].

5.1.2 Setting time property

This refers to the time it takes for the concrete to solidify and harden after it has been mixed. The agro waste based geopolymer concrete’s setting time can be influenced by various features such as, the type and concentration of alkali activators used, the mix design, and the conditions of curing. Here are some key points associated with the setting time of geopolymer concrete:

5.1.2.1 Setting time can be adjusted

Geopolymer concrete’s setting time property can be adjusted by changing the type and concentration of alkali activators used in the mix. Increasing the concentration of alkali activators can reduce the setting time, while decreasing the concentration can increase the setting time [131].

5.1.2.2 Rapid strength development

Geopolymer concrete can develop high strength rapidly, which can lead to shorter construction times. However, rapid strength development can also result in a shorter workability time, making it important to properly plan and execute the placement of the concrete [79].

5.1.2.3 Curing conditions

The curing conditions used for geopolymer concrete can affect its setting time. Higher curing temperatures can accelerate the setting time, while lower curing temperatures can slow it down.

5.1.2.4 Monitoring setting time

Geopolymer concrete’s setting time behavior can be monitored using various methods, such as the penetration resistance test, the Vicat needle test, and the slump test. Proper monitoring can help ensure that the concrete has set and hardened properly [132].

Generally, the setting time of geopolymer concrete can be adjusted to meet specific project requirements, and its rapid strength development can lead to shorter construction times. Proper monitoring and control of the setting time can help ensure the successful use of geopolymer concrete in construction projects.

5.1.3 Viscosity characteristics

Viscosity is an important property of geopolymer concrete at the fresh state, which refers to its resistance to flow. Geopolymer concrete’s viscosity is influenced by various parameters, including the sort and concentration of alkali activators, the kind and volume of aggregates used, and the water-to-binder proportion [133]. Compared to traditional concrete, geopolymer typically has a greater viscosity due to the higher concentration of solids and lesser water-to-binder proportion. This higher viscosity can make it more difficult to pump or place the concrete, but it can also improve its resistance to segregation and bleeding. To enhance the geopolymer concrete’s workability and flowability behavior, superplasticizers can be added to lower the viscosity and magnify the fluidity of the mix. The use of fine aggregates and proper grading of the aggregates can also help optimize the viscosity of the concrete [134].

5.1.4 Shrinkage property

Shrinkage is an important property of fresh geopolymer concrete, which refers to the decrease in the concrete’s volume as a result of the loss of water during the hardening process. Shrinkage can cause cracking and other defects in concrete, which can affect its durability and overall performance [135]. SCBA and BPA based Geopolymer concrete has been found to exhibit lower drying shrinkage compared to traditional Portland cement concrete, due to its lower porosity and lower water demand. This can result in reduced cracking and improved durability of the concrete. However, it is vital to carefully control the mix design and curing practices to minimize shrinkage and ensure the desired performance of the concrete [102].

5.1.5 Strength development property

Strength development is a key characteristic of fresh geopolymer concrete, which denotes the tendency of the concrete to gain strength over time. Geopolymer concrete can exhibit high strength development due to its unique chemical composition and activation mechanism [136]. The strength development of geopolymer concrete rest on several factors, including the type and concentration of the alkali activator, the characteristics of the aluminosilicate materials, the water-to-binder proportion, and the curing conditions. Geopolymer concrete can exhibit rapid strength development, specifically at early ages. This is due to the rapid polymerization of the geopolymer binder, which lead to the development of a compact and solid matrix [13]. The early age strength gain can be advantageous in construction applications that require high early strength, such as precast concrete products, repair and rehabilitation of structures, and rapid construction projects. Nguyen et al. [137] and Kumar et al. [137] showed that between 88 and 93% of the 7–28 day cured ternary blended geopolymer concrete’s mechanical properties can be realized, irrespective of agro-industrial waste ash and using heat curing method.

5.2 Mix proportioning of geopolymer concrete

The mix design for geopolymer concrete involves selecting the appropriate materials and ratios to attain the anticipated properties and characteristics. It is important to note that the mix design for geopolymer concrete may vary depending on the specific application and materials used [138]. To appropriately carryout mix proportioning of geopolymer concrete, it is important consider the following criteria;

• Material selection: precursor, alkaline activators and aggregate materials used in geopolymer concrete should be carefully selected based on their availability and suitability in terms of physicochemical characteristics [139].

• Chemical composition: The chemical structure of the materials deployed in geopolymer concrete is critical in defining the reaction mechanism and strength development of the concrete. The proportion of SiO₂ to Al₂O₃ in the precursor materials should be expertly adjusted to ensure a proper geopolymerization reaction [140].

• Alkaline activator concentration: This criterion provides an essential factor in determining setting time and mechanical behavior of geopolymer concrete. The activator molarity should be optimized to attain the desired strength and setting time [141].

• Water content: The measure of this criterion in the geopolymer concrete mix should be prudently optimized to achieve the anticipated workability and strength. Excess water can result in reduced strength and durability.

• Aggregate selection: The selection of aggregates should be based on their physical characteristics, such as gradation, shape, and texture of particles, as well as their compatibility with the geopolymer binder [142].

• Curing conditions: Proper curing is critical in achieving the desired strength and durability of geopolymer concrete. The curing conditions should be carefully controlled, including temperature, humidity, and duration.

To achieve effective design of geopolymer concrete’s mix proportion, the desired mix design parameters which include the workability, compressive strength, and water-to-binder ratio (L/B) are ascertained. These parameters can be determined based on the application of the geopolymer concrete. By considering these criteria, a well-designed geopolymer concrete mix can be developed that meets the desired performance criteria and offers several advantages over traditional Portland cement concrete [143, 144]. Depending on the precursor material, many approaches are available for the mix design of geopolymer concrete. A well-prepared solvent may be used to activate any material that comprises silica and alumina oxides in order to produce inorganic polymeric mixtures for construction works, as reported by Li et al. [145]. Rangan's approach [146] is the most often utilized technique for producing geopolymer concrete with a compressive strength property varying from 20 to 80 MPa out of the several ways available for the mix design of agricultural waste ash-based geopolymer concrete. Depending on how many different source precursor materials were utilized, geopolymer concrete may be divided into three different types: unary, binary, and ternary [147].

5.2.1 Unary geopolymer concrete

This requires the creation of geopolymer green concrete from a single source material, like slag, fly ash, banana peel ash, rice husk ash, cassava peel ash, bagasse ash, cement kiln dust, or Bambara nut ash. For the creation of geopolymer, the precursor aluminosilicates may be the only material employed with a metallic alkali activator [148]. Aluminosilicates may be used to improve concrete's quality while curtailing the harmful effects on the economy, atmosphere, and society. Using industrial waste ash, Chindaprasirt et al. [149] created geopolymer mortar with a compressive strength of 65 MPa. High compressive, tensile, and flexural strength qualities are present in agro waste ash-based geopolymer concrete, but poor elasticity, water absorption, and sorptivity values are present according to Krivenko et al. [150]. Moreover, Madheswaran et al. [151] created geopolymer concrete using slag and attained compressive strengths between 62 and 65 MPa using a 1:1.5:2.5 ratio and a 0.6 solution to binder proportion.

5.2.2 Binary geopolymer concrete

Any two silica and alumina-containing cementitious source precursor materials may be combined to create geopolymer concrete, also known as binary blended geopolymer. Binary geopolymer is more expensive than regular concrete for low-strength concrete [152]. In addition to lowering the cost, adding additional locally accessible cementitious agricultural waste materials to geopolymer concrete, such as bagasse ash, palm bunch ash, banana peel ash, rice husk ash, and Bambara nut shell ash, may enhance the material's mechanical and durability qualities [153]. Thus, geopolymer concrete which is manufactured by combining precursor materials from different sources is often accessible recently and may be used to enhance and provide better elemental composition performance [153].

5.2.3 Ternary geopolymer concrete

Ternary geopolymer is the name given to the geopolymer concrete created by mixing three cementitious precursor ingredients. Utilizing a ternary system has the advantage that a bad impact from one product may be offset by positive contribution from another [154]. This would increase sustainability by lowering environmental effects and enhancing the beneficial use of a substance that would otherwise be regarded as trash while also enabling the production of dependable mixes with relatively modest quantities of cement clinker. One containing Portland cement and two additional components in the binder, mixed either at the cement plant or at the batch plant, is an excellent example of a ternary combination [155]. Ternary mixes formulated to reach a certain 28-day strength tend to display stronger properties than simple combinations at older ages [156]. Notably, the ternary combinations fared better than the binary mixtures which is in consonance with the findings of the research by Mala et al. [157].

5.2.4 Factors Influencing geopolymer concrete mix proportion

Geopolymer concrete mix proportion is influenced by several factors, including:

• Chemical configuration of raw materials: The chemical composition of the raw materials utilized in geopolymer concrete, such as SCBA, BPA and other agro waste derivatives, affects the strength and setting time of the concrete. The ratio of SiO₂ to Al₂O₃ in the raw materials must be optimized to achieve proper geopolymerization [158].

• Alkaline activator concentration: The concentration of the activators, such as NaOH, KOH, or Na₂SiO₃, affects the engineering behavior of geopolymer concrete. The concentration must be optimized to achieve the desired properties of the concrete [159].

• Water-to-binder ratio (L/B): The L/B ratio affects the workability and strength of geopolymer concrete. A low L/B ratio produces higher strength but lower workability, while a high L/B ratio produces higher workability but lower strength [160].

• Aggregate size and grading: The size and grading of aggregates affect the workability and strength of geopolymer concrete. Well-graded aggregates with a smooth surface texture improve workability and produce higher strength [161].

• Curing conditions: The curing settings affect the durability and strength of geopolymer concrete. The curing temperature, duration, and humidity must be carefully controlled to achieve the preferred concrete behavior [162].

• Type and concentration of admixtures: Admixtures such as superplasticizers, air-entraining agents, and retarders can be incorporated into the geopolymer concrete to enhance its behavior. The type and concentration of admixtures must be optimized to achieve the desired properties of the concrete [163].

• Raw materials age: The age of precursors, especially SCBA, BPA and other agro waste aluminosilicates, can significantly influence geopolymer concrete’s characteristics. Fresh precursor is more reactive and produces higher strength than the aged one [164].

5.3 Effect of particle size fraction, aggregates content and types

The fine and coarse aggregates utilized in geopolymer concrete combinations are similar to those deployed in conventional concrete mixtures. In earlier studies, fine aggregate was made from river and crushed sand that had an aggregate size limit of 4.75 mm, a specific gravity range of 2.60–2.8, and ASTM C 33-compliant grade [165]. The aggregate size in the geopolymer concrete matrix plays a crucial role in the rising temperature; as the maximum aggregate size of the geopolymer concrete mix design increases, the spalling of geopolymer concrete decreases. By securing the crack tip, the extent of the crack process zone grows as the aggregate size rises. With an average density of 610 kg/m³, the fine aggregate content varied from 318 to 1196 kg/m³. Additionally, gravel with an aggregate size limit of 20 mm has been used as the coarse aggregate in geopolymer concrete matrices with densities ranging from 394 to 1591 kg/m³ and an average of 1174.5 kg/m³ [166]. In Fig. 8, it is demonstrated how the total aggregate content of the waste ash-based alkali activated binder geopolymer concrete affects its compressive strength characteristics [167, 168]. It was found that the compressive strength qualities of the geopolymer concrete increased with the increase in whole aggregate content up to 78% and thereafter decreased owing to a lack of binding agent to keep the aggregates intact [169].

Fig. 8

Total Aggregate Content (%) on the Geopolymer Concrete’s Compressive Strength [165, 166]

The geopolymer combination with crushed sand also showed a better mechanical properties behavior when matched with other aggregates. This finding was explained by the angular form and texture roughness of the crushed sand, which provide a larger surface-to-volume ratio and better binding properties between the aggregates and paste matrices [170]. In addition, they noted that when compared with other kinds of graded aggregate, crushed sand with coarser sized particles exhibited features that improved compressive strength [171]. This is consistent with Mane and Jadhav's results, which revealed that crushed sand fine aggregates significantly improved than river sand in terms of compressive strength and that granite coarse aggregates performed more than coarser basalt stones [172].

The maximum aggregate size increase in mix design increases stability while increasing fire resistance. The aggregates and pastes are more compatible with each other and the geopolymer concrete is more resistant to high temperatures [173]. The surface roughness of the aggregates gives them a superior crushing value and good bonding. Up to a 40% replacement of natural sand, the fine aggregate dosage in the mix design exhibits higher mechanical characteristics; however, beyond that point, the mechanical properties of the mix degrade as the percentage of geopolymer sand increases. Up to 20% of the natural fine aggregates in the mix may be replaced with m-sand to boost the strength of the concrete, but beyond that point, the strength of the concrete starts to gradually decline relative to the nominal mix [174, 175]. The geopolymer concrete has a carbon emission that is up to 80% lower than conventional concrete since it replaces natural sand with 100% m-sand, which exhibits appropriate strength. The partial substitution of natural sand in the design mix by waste aggregate is proven to enhance the ductility of the structural element of geopolymer concrete [176].

5.4 Effect of the alkali metal activator

Alkali metal cations play a significant part in each step of the geopolymerization process, which is how geopolymer concrete is created. This reaction occurs among the binding components of SCBA and BPA based geopolymer concrete. In all phases of the process, the kind of alkali metal cation plays a crucial role in the geopolymerization reaction [177]. It also has an impact on how quickly the paste sets up and how quickly the geopolymer concrete condenses. The ultimate morphology of the molecules is directed and controlled by the reaction using the alkali metal cation as a template [178]. The structure of the geopolymer is also impacted by the magnitude of the alkali metal cation. In the identical circumstance, the potassium (K) cation causes a greater condensation than the sodium (Na) cation [179]. Due to its larger surface area, the potassium cation exhibits greater compressive strength, forms a greater amount of amorphous structure, and is less resistant to HCl attack. Because the differing source materials have a direct impact on the physical and chemical characteristics of the end products, the alkali metal relies on the source material (Si and Al concentration) for the chemical interaction [180].

The chemistry of polymeric reactions has a direct impact on the agricultural waste ash-based geopolymer. Compositions with higher amounts of NaOH and Na₂SiO₃ have finished products with greater compressive strength, quicker setting times, and fire resistance [181]. A result of functional variations in the morphology, the geopolymer product has lower thermostability when using activators that include sodium than when using activators that contain potassium. At 800 °C, the average pore size of the sodium-activated geopolymer rises, drastically reducing its strength [182]. Compared to the conventional sodium-containing activator, the materials produced using potassium silicate and fly ash exhibit greater thermal stability. In the potassium activator, the materials remained amorphous up to 1200 °C, but in the sodium activator, the crystalline Na-feldspar replaces the amorphous structure [183].

When heated over 800–1200 °C, the geopolymer material made from industrial wastes like fly ash mixed with sodium or potassium silicate exhibits very high shrinkage and noticeable changes in compressive strength [184]. An activator in the geopolymer materials that contains sodium exhibits thermal stability up to 500 °C, which is higher than that of the conventional concrete mix. The Si/Al ratio and the alkali in the activator have major roles in the thermal shrinkage of the geopolymer [185]. In comparison to mixtures with higher Si/Al ratios, those with a lower Si/Al ratio exhibit improved thermal stability and exhibit densification at high temperatures. Graphical results presented in Fig. 9 illustrates how the ratios of Na₂SiO₃ to NaOH affect the SCBA based geopolymers’ compressive strength, with the maximum response obtained at a ration of 2 and at 5% of SCBA replacement [186, 187].

Fig. 9

Impact of Na₂SiO₃ to NaOH ratios on the geopolymer compressive strength [186, 187]

The compressive strength of the produced SCBA based geopolymer concrete is also pointedly impacted by the alkali activator level. Due to the aluminosilicate’s solubility with a rise in Na₂O concentration, increasing the alkali percentage enhances compressive strength. Between 6 and 15% of the bulk is made up of Na₂O [188]. However, once the alkali level exceeds 10%, there is no discernible improvement in strength. Greater amounts of silica and sodium exhibit more innermost shrinkage than cement matrix, however the autogenous shrinkage process of the geopolymer mixture is distinct from that of cement paste [189]. The rearrangement and geopolymerization of the structure in the geopolymer results in a narrower pore size allotment that causes endogenous shrinkage in the cement matrix rather than self-desiccation [190].

5.5 Effect of concentration of alkaline solution

As concentration of NaOH molarity rises, the compressive strength of the geopolymer concrete's compressive strength improves, but its flowability decreases. When compared to conventional concrete, the geopolymer concrete has superior mechanical qualities because of the usage of sodium hydroxide, which also contributes to its higher strength and performance. KOH creates a significantly more heterogeneous structure than sodium silicate, with lower strength after hydration and increased porosity [191].

To produce geopolymer concrete with a strength of at least 40 MPa and to test the feasibility of using agro-waste ash precursor in lieu of cement, sodium hydroxide and sodium silicate are employed as alkaline activator of the binder in a 1:1 ratio in the mix design. As the slag quantity, Na₂SiO₃ content, and NaOH concentration rise, so does the time required for the agricultural waste-based paste to set [192]. At a temperature of 17 °C, the agro waste-based paste requires initial and final setting duration of 55 min and 160 min respectively. In 28 days, the range of molarity of 9.5–14 M of NaOH at room temperature was used to swiftly attain the compressive strength of 30 MPa. If the NaOH molarity is less, the calcium content of the precursor samples contributes to the growth of the geopolymer matrix and the production of the calcium-based geopolymer. Calcium hydroxide precipitates when there is a high concentration of NaOH [99, 193].

The performance of the produced geopolymer concrete in terms of mechanical strength is closely correlated with the NaOH content. Waste ash dissolves faster and gains greater strength when the OH ions are at their highest level [194]. High OH ion concentrations prevent polycondensation and reduce strength, according to Zuhua et al. [195]. Additionally, Lee and Deventer [196] noted that the precipitation of aluminosilicate gel occurs when OH ions are present in excess, which may result in a reduction in the strength of geopolymer concrete. In trials to determine how potassium and sodium hydroxide solutions affected GPC, Abdul Rahim et al. [197] measured the compressive strength and found that it was 28.73 MPa and 65.28 MPa, respectively. Sodium hydroxide was utilized by Gorhan and Kurklu [198] as an activator to create green geopolymer concrete. By varying the NaOH content to 3, 6, and 9 M, the authors were able to realize compressive strengths of 17, 21.5, and 22 MPa, correspondingly. Some interesting review literatures on the alkaline concentration effects on the produced geopolymer concrete is shown in Table 3.

Table 3 Effect of alkaline solution on geopolymer concrete

5.6 Effect of curing conditions

The geopolymer concrete sets and hardens in large part as a result of the curing temperature. The setting of new concrete may take up to 4 days without losing quality when the ambient temperature is below 10 °C, but the geopolymer samples that were made and cured at higher temperatures achieve concrete desired strength in 4 h [200]. In comparison to the mechanical strength attained by the geopolymer concrete specimens that were cured at a higher temperature, qualitative strength was improved after 28 days of the fresh concrete's hardening at ambient temperature. In order to increase strength with temperature, curing time is also crucial [201]. As the curing temperature rises from 30 °C to 90 °C, the compressive strength of the geopolymer concrete also rises. The temperature for curing is advantageous for acquiring more strength, and the prolonged curing time promotes the geopolymerization process, if curing at ambient temperature is unachievable owing to the delayed time of agricultural waste ash-based geopolymer concrete [202].

Long-term curing of geopolymer samples at higher temperatures causes the microstructure to become distorted, leading to fractures in the sample from water evaporation from the matrix. In comparison to OPC concrete with the same compressive strength, the flexural strength of geopolymer concrete is greater [203]. Four different varieties of geopolymer concrete were subjected to high temperatures ranging from 20 to 1000◦C for two hours before Zhang et al. [204] examined their residual compression resistance. The concrete made of geopolymer was heated at a rate of 5◦C per minute. All of the geopolymer concrete specimens' compressive strength values were found to be higher between 20 and 400◦C than their initial values [205]. The low crushing index of coarse aggregate within the temperature range may be responsible for this; the results showed that coarse aggregate in the geopolymer concrete specimens could survive thermal stress up to 400 °C [206].

The compressive strength of geopolymer concrete made with natural pozzolanic materials rises with temperature and time. Both autoclave curing over 100 °C and atmospheric pressure curing up to 100 °C are used to cure geopolymer concrete applications. By removing the samples' microcracks, it improves the blended samples' compressive strength [207]. The geopolymer concrete’s compressive strength improves from 6–96 h of curing, however after 48 h of curing, the compressive strength of the samples is not significantly different. It is advantageous for strength growth to pre-cure at an ambient temperature over 95% humidity at room temperature before heat curing [208]. When specimens that have been exposed to high temperatures for 1 h are not noticeably stronger, temperature curing is to blame. Through an acceleration of response rates, the extended curing time is to blame for the early growth of strength [209]. There is no need to cure the material for more than 24 h since the polymerization process is improved from 4–96 h by curing and the compressive strength is increased. The temperature of curing on the geopolymer concrete’s mechanical strength performance with varying molarity of the metallic alkaline activator is illustrated in a box-plot shown in Fig. 10 [210, 211].

Fig. 10

The impact of curing Temperature Geopolymer concrete’s strength [210, 211]

The early strength of the geopolymer concrete is developed by the geopolymerization process, which intensifies as the curing temperature rises. When steam cured, the geopolymer concrete's final products exhibited a mainly open morphology, demonstrating the material's significant moisture absorption [212]. The oven-cured specimens of geopolymer concrete developed to 90% strength in 3 days and to a 28-day compressive strength, while the ambient-cured specimens developed to up to 82% strength in 28 days [211]. The final strength of the ambient-cured specimens was greater than that of the oven-cured samples because the strength rate after 7 days is not substantial. The curing temperature has a direct impact on the elastic modulus of geopolymer concrete. Up to a certain point and in relation to the water to binder ratio, the specimens' modulus of elasticity rises with rising curing temperature [213]. The elastic modulus of the geopolymer concrete samples decreases as a result of water from the matrix evaporating throughout the temperature curing process. The effects of curing conditions with respect to the curing ages in days on the geopolymer concrete’s compressive strength response is presented in Fig. 11 [214]. The result showed better strength performance for the heat cured samples when compared with the ambient cured specimens [215, 216].

Fig. 11

Effects of Curing Conditions and Curing Ages on Concrete’s Compressive Strength [215, 216]

5.7 Effect of silicate and alumina

In the spectrum electrum microscopy examination, if the matrix has a Si/Al ratio less than or equal to 1.40, it displays a clustered dense microstructure with big interconnecting pores, and if it has a Si/Al ratio of greater than or equal to 1.65, it displays a homogeneous morphology with small holes [217]. When the ratio of Si/Al is within the limit of 1.40–1.65, the morphology of the matrix gel becomes more complex as silicon concentration rises. The matrix's volume expands as a consequence of the microstructure of the geopolymer being impacted by nitrogen absorption [218]. When the gel's microstructure is homogeneous and the ratio of Si to Al is 1.65, the greater gel volume results in a higher compressive stress and a rise in the young modulus. As a result, the young modulus is dependent on both the gel's compressive strength and its microstructures' homogeneity. Due to the unreacted silica that is present in the matrix, the ultimate strength of the mixed specimens is decreased beyond the Si to Al is 1.90 value [219].

Due to dehydration, dehydroxylation, sintering, and robustness, the thermal shrinkage rises as the Si/Al ratio of the mixed component does. In the geopolymerization process, silica and alumina levels are crucial [220]. The amorphous end products that silica content produces in the reaction, the mix design's increased compressive strength is enhanced by the denser matrix growth. With increasing silica concentration, the mechanical characteristics likewise improve and reach a maximum strength of 65 MPa [159]. The ratios of SiO₂/Al₂O₃ and SiO₂/Fe₂O₃ in the geopolymer concrete rise with the curing temperature, improving the mechanical qualities of the finished geopolymer concrete. In comparison to Portland cement concrete, they also have a lower water absorption capacity. The reactivity of the geopolymer matrix is unaffected by the amount of CaO in the mixture [77].

The substantial strength improvement at a later age is mostly attributable to the rise in the molar ratio of SiO₂/Al₂O₃ to 3.4–3.8. Agro-industrial waste ash activated with sodium silicate exhibits low to moderate strength in the agro waste ash-based geopolymer concrete with a Si to Al ratio of greater or equal to 5, but after heating, the cure exhibits outstanding dimensional stability and high compressive strength. Less than 2 value for Si to Al ratio results in excellent compressive strength but poor dimensional stability and strength reduction after heating [77, 221]. Increment in the alumina and silica concentration speed up the geopolymerization process in the 3.20–3.70 range. As the mixture's alumina concentration rises, neither the zeolitic phase nor the strength of the mixture's samples develop [222]. The amount of alumina in the mixture greatly influences how quickly it sets. Longer setting times are caused by an increase in the Si to Al ratio. Additionally, the strength of the concrete is reduced by increases in Al concentration. The silica to alumina effects on the geopolymer concrete’s compressive strength properties is presented in Fig. 12 [223,225,225]. The derived results indicate best performance at Si to Al ratio range of 4–4.1.

Fig. 12

Silica-Alumina ratios effects on the geopolymer concrete’s performance [223,225,225]

5.8 Effect of calcium content

In order to generate the calcium-silicate-hydrate (CSH) with the geopolymeric gel under low alkaline circumstances and increase the mechanical strength of the mixture, the geopolymer concrete uses the calcium content of the agro-industrial waste derivatives and that of cement [159]. The mix's overall strength was reduced since there was less CSH gel due to the decreased calcium level. In high alkaline circumstances, the calcium content has a small but significant impact on strength enhancement and contributes to the precipitation of CSH gels [226]. The mechanical strength of high calcium bagasse ash is influenced by the water content in the mix design and its fineness. For both early and more protracted aging, the calcium concentration found in the mix's slag is crucial. If the reaction rate is sluggish and poor strength growth is established, the lower concentration of alkali activator without heat curing is utilized as a binder with the lower calcium agro-industrial waste ash [227]. Fresh geopolymer concrete developed its strength via the production of C-S–H and C-A-S–H precipitation, while in geopolymers based on agricultural waste derivatives, the concrete hardens through the formation of alumina-silicate precipitation [228]. The creation of the gel is accelerated by the free calcium content created by the breakdown of slag and fly ash, which subsequently boosts the strength of the cured concrete. The final result is a chain-structured C-A-S–H type gel, which is enhanced by the greater calcium content in the mixture. High strength geopolymer concrete is said to include a lot of calcium [229].

5.9 Alkaline solution to the binder ratio (l/b)

While "binder content" refers to the full volume or weight of the aluminosilicate precursor obtained from agricultural waste in the geopolymer concrete mixture proportions, the phrase "alkaline solution" describes the total of the sodium silicate and sodium hydroxide contents [230, 231]. According to pertinent research studies, the l/b ratio of agro-industrial residue ash ranged from 0.25 to 0.6 as depicted in the graphical plot in Fig. 13 with an average standard deviation, kurtosis, skewness, and variance of 0.01, 2.31, 1.24, and 0.46 respectively [232,234,234]. According to Aliabdo et al. [188] findings, when the mineral admixture density of 10.5 kg/m³, SS/NaOH of 0.4, water content of 35 kg/m³, and Molarity of 16 were held constant, the mechanical properties of the produced geopolymer concrete was improved as the l/b ratio increased up to 0.4–0.5, after which the effect caused a decline in strength. Similar to this, Shehab et al. [235] found that increasing the ratio of l/b improved the compressive strength characteristics of alkali-activated binder geopolymer at 7 and 28 hydration periods. The result derived was credited to the fact that the water content in the reaction medium of the geopolymer concrete mixture was increased, as any increase in the l/b ratio results in decreased friction between the particles and, as a result, a reduction in the compressive strength behavior of the geopolymer concrete [236]. Additionally, it was found that a geopolymer concrete mixture with a low l/b ratio can produce calcium aluminate silicate hydrate (C-A-S–H) and sodium aluminate silicate hydrate (N-A-S–H) gels quickly, which helps create the early-age compressive strength properties of alkali-activated geopolymer concrete [237].

Fig. 13

Alkaline to binder ratio effects on geopolymer concrete’s compressive strength [232, 234]

5.10 Mechanical properties of geopolymer concrete

The early strength development of the hybrid geopolymer system is greatly enhanced by the addition of sodium silicate. After the high soluble silicate dose in the salt-free geopolymeric mortar, the boundary between aggregate and geopolymeric paste is not readily discernible [238]. Even after utilizing a high alkali concentration activating solution, soluble silicates are very helpful in the geopolymerization process for reducing alkali saturation in the geopolymer concrete pore solution and encouraging the greater inter-particle bonding binder as well as the aggregate surface. Because bagasse ash is light, a higher proportion will result in lighter geopolymer samples that include bagasse ash [239]. Through the filler effect in the interfacial zone of transition between the agro waste-based alkali-activated binder paste and aggregate particles, the addition of banana peel ash increases compressive strength. Additionally, hydrated lime gels are promptly eliminated during the hydration of cement using metakaolin and in fact speed up cementitious hydration [103].

The durable geopolymer products including binders, mortars, and concrete are produced by geopolymerization. The ratio of sodium silicate to sodium hydroxide (by mass) rises as the compressive strength of the geopolymer concrete increases. If the mixture contains more alkaline solution, the compressive strength will decrease while the setting time and workability will rise [240]. The ideal point was discovered at 2.5 alkaline ratio and at 40% alkaline solution in the mixture. The alkaline ratio grew from 1.5 to 2.5, and the alkaline solution increased from 35%-45% of the mass of binder. When comparing cost per ton and strength of geopolymer mortars, the Na₂CO₃ activator is the least expensive option [241]. The compressive strength of mortar and paste reaches their yield point at a molar ratio of Na₂O to SiO₂ of 0.40, demonstrating the paste's denser shape. The consistency of the paste diminishes as the Na₂O to SiO₂ molar ratio rises [242]. With the addition of fly ash, it creates an alumino-silicate gel that gives hardened geopolymer concrete samples their superior workability and mechanical qualities. The mix design's demand for fine aggregate is reduced due to the higher Na₂SiO₃/NaOH ratio, but the mix design's criterion for more water is raised [243]. Table 4 presents essential extracts from relevant literatures on the geopolymer concrete’s mechanical strength improvement and the influential factors.

Table 4 Influential factors on the improvement of Geopolymer concrete compressive strength

5.11 Microstructure assessment of geopolymer concrete

Assessing the microstructure of geopolymer concrete typically involves examining the cementitious matrix and the aggregates present in the concrete [248]. The following are some of the commonly used methods for microstructural examination of geopolymer concrete as presented by relevant literature works;

5.11.1 Scanning electron microscopy (SEM)

SEM is an essential technique for examining the microstructure of geopolymer concrete, providing important insights into its composition, morphology, and properties. It provides high-resolution images of the surface, size, shape and texture of the concrete ingredients, which can be used to identify the different phases present in the matrix and the aggregates. During SEM analysis of geopolymer concrete, a small section of the concrete sample is cut and mounted on a conductive substrate. The sample is then coated with a thin layer of conductive material, such as gold or carbon, to improve conductivity and prevent charging during imaging [189]. The SEM then directs a beam of high-energy electrons onto the surface of the sample. The electrons interact with the atoms in the sample, generating signals that can be used to create an image of the surface. The images obtained can provide information about the size, shape, and distribution of the different phases present in the concrete [249]. The SEM micrographs of SCBA and BPA are presented in Fig. 14a, b respectively. The Particles present in the agro waste geopolymer mixture consists of silt-sized particles which are generally wavy cube, fairly impenetrable, smooth texture, sharp and irregular surface and different sizes ranging in size between 30 and 150 microns which is in agreement with the findings of Kamsuwan [249] and Castaldelli et al. [250]. SEM can be used to examine the morphology of the geopolymer gel, which is the primary binder in geopolymer concrete and also the aggregates present. The gel is composed of a network of aluminum and silicon atoms linked together by oxygen. SEM images can show the distribution and morphology of the gel, which can provide insights into the strength and durability of the concrete.

Fig. 14

SEM micrographs of (a) SBA and (b) BPA [249, 250]

5.11.2 X-ray diffraction (XRD)

XRD is a powerful technique for analyzing the crystal structure of geopolymer concrete, providing important information about the composition, structure, and properties of the material. XRD is used to identify the mineral phases present in the concrete and to determine their relative proportions [251]. During XRD analysis of geopolymer concrete, a small section of the concrete sample is powdered and placed in a holder. The holder is then mounted on a diffractometer, which generates a beam of X-rays that is directed onto the powdered sample. The X-rays interact with the atoms in the sample, generating a diffraction pattern that can be used to identify the crystal structure of the different phases in the concrete. XRD can be used to identify the different mineral phases present in the geopolymer concrete, such as alumino-silicate gel, zeolites, and calcium silicate hydrates [252]. The XRD results for the SCBA and the energy dispersive spectroscope (EDS) for BPA is shown in Fig. 15. The XRD spectrum depicted the formation of C–S–H due to a high amount of reactive amorphous silica in SCBA reacted with Ca(OH)₂ from cement hydration. However, at 2θ between 25◦ and 30◦, it is shown that CH peak intensity decreased as presented by Ribeiro and Morell [253]. The EDS result disclosed that elements namely Na, Cl, Mg, O, K, Ca were present in the blended samples with sharp peaks observed at E = 2.7, 0.6, 3.4 keV were correspond to K, O, and Cl correspondingly which is in consonance with the findings of Mucino et al. [254]. XRD can also be used to determine the degree of crystallinity of the different phases in the geopolymer concrete. This can provide insights into the strength and durability of the concrete, as the degree of crystallinity can influence the mechanical properties and chemical resistance of the material.

Fig. 15

(a) X-ray diffraction pattern of SCDA; (b) EDS for BPA [253, 254]

5.11.3 Thermogravimetric analysis (TGA)

TGA is a technique used to analyze the thermal stability and degradation behavior of materials, including geopolymer concrete, providing important insights into the durability and performance of the material under different temperature conditions. TGA can be used to determine the weight loss and thermal stability of the material as it is heated under controlled conditions [255]. During TGA analysis of geopolymer concrete, a small section of the concrete sample is dried and ground to a fine powder. The powder is then placed in a TGA instrument, which heats the sample at a controlled rate and measures the weight loss as the material decomposes and evolves gases [256]. TGA can be used to determine the thermal stability of the different phases in the geopolymer concrete, such as alumina-silicate gel, zeolites, and calcium silicate hydrates. The weight loss and thermal stability of these phases can provide information about the durability and performance of the concrete under different temperature conditions. This method can also be used to evaluate the effectiveness of various admixtures and curing methods in modifying the thermal stability of the geopolymer concrete [257]. The TGA curves of SCBA and BPA as illustrated by relevant literatures were presented in Fig. 16a, b respectively [207, 258]. The results for SCBA indicated that at temperatures of about 480 °C, the sample displayed an unceasing weight-loss getting to 77% which is due to decomposition reactions. However, weight-loss was not spotted at temperatures greater than 480 °C, signifying the completion of decomposition reactions. The TGA curves of BPA at a heating rate of 10 °C min⁻¹ depicted the wide-ranging peak of 200–350 °C as a result of cellulose degradation, next stage of weight loss was observed at a gauge level of 350–600 °C because of fatty acid decomposition.

Fig. 16

TGA curve for (a) SCBA and (b) BPA [207, 258]

5.11.4 Fourier transform infrared spectroscopy (FTIR)

FTIR) is a technique used to analyze the chemical composition of materials, including geopolymer concrete. FTIR can be used to identify the functional groups and chemical bonds present in the material, providing information about its composition, structure, and properties [258]. During FTIR analysis of geopolymer concrete, a small section of the concrete sample is ground to a fine powder and mixed with a matrix material. The mixture is then pressed into a thin pellet, which is placed in the FTIR spectrometer. The spectrometer generates a beam of infrared light, which is directed onto the sample. The infrared light interacts with the functional groups and chemical bonds in the sample, generating a spectrum that can be used to identify the different components in the material [259]. FTIR can be used to identify the different phases present in the geopolymer concrete, such as the alumina-silicate gel, zeolites, and calcium silicate hydrates. The FTIR spectra for SCBA and BPA as derived from pertinent literatures were shown in Fig.17a, b respectively [260, 261]. From SCBA result, the average and sharp peaks near 3774 and 3100 cm⁻¹ designate the existence of the O–H groups of silanol and N–H bond correspondingly. Medium crests at 3000–2845 cm⁻¹ are as a result of the C–H stretching of alkanes. The peak due to –OH stretching in carboxylic acid was perceived close 2100 cm⁻¹. Also, 1380–1113 cm⁻¹ bands can be ascribed to the –C–OH and –CO stretching peaks of lactones, carboxylic acids, and alcohols. Moreso, BPA result spectra displayed frequency vibrational bands of 810, 1040, 1123, and 1198 cm⁻¹ due to K–O stretching. Also, due to Ca-O stretching medium crests of 615, 691, and 871 were obtained, while the sharp absorption peak of 1409, and 1648 cm⁻¹ was due to stretching vibration of O–H derived from the metal oxide surface. The spectra obtained can provide information about the functional groups and chemical bonds present in these phases, which can influence the strength, durability, and chemical resistance of the concrete [262].

Fig. 17

FTIR spectra for (a) SCBA and (b) BPA [260, 261]

6 Established gaps in literature

Geopolymer concrete is a relatively new and emerging field of research especially when produced with abundance agro waste derivatives such as SCBA and BPA as precursor materials, and while significant progress has been made, there are still some gaps in the literature that need to be addressed. Here are some potential gaps in the reviewed literature:

• Standardization: There is currently no standardized mix design or testing method for geopolymer concrete, which can make it difficult to compare results across different studies. More research is needed to develop standardized procedures and guidelines for the production and testing of geopolymer concrete.

• Long-term durability: While geopolymer concrete has revealed promising durability and mechanical behavior in short-term tests, there is limited research on its long-term durability. More research is essential to realize how geopolymer concrete performs over a period of several years or even decades.

• Alkali-activated binders: Geopolymer concrete is often made using alkali-activated binders, but there is limited research on the long-term durability and stability of these binders. Additional study is required to identify the chemical and physical processes that occur within the binder and how they may impact the performance of the concrete over time.

• Environmental impact: Geopolymer concrete has been touted as a more environmentally friendly substitute to traditional conventional concrete, but there is limited research on the environmental impact of geopolymer concrete production and use. Further study is vital to figure out the carbon footprint and other environmental impacts of geopolymer concrete compared to traditional concrete.

• Industrial-scale production: While there have been many laboratory-scale studies on geopolymer concrete, there is inadequate investigation on its production and performance at an industrial scale. Extra research is desirable to understand how geopolymer concrete can be produced and used in large-scale infrastructural projects.

Overall, there is still much to be learned about geopolymer concrete produced with agro byproduct precursors such as SCBA and BPA, and continued research is needed to address these gaps in the literature and advance our understanding of this promising construction material.

7 Conclusion

Agro waste-based geopolymer concrete is an auspicious and sustainable substitute to traditional Portland cement-based concrete. The use of agro byproduct materials such as banana peel ash, rice husk ash, bagasse ash, and sawdust ash as a source of aluminosilicate for geopolymerization has shown capacity in diminishing the carbon footprint of the civil construction industry. Studies have shown that agro waste-based geopolymer concrete exhibits comparable or even improved mechanical behavior compared to traditional concrete, as well as good resistance to acid and sulfate attacks. The use of agro waste materials also helps to reduce waste and improve the economic viability of the construction industry.

Nevertheless, there are still some encounters to surmount in the development and adoption of agro waste-based geopolymer concrete. These challenges include the variability of the raw materials, the need for standardization in mix design and testing procedures, and the need for further research to appreciate the long-term durability and environmental impact of this material. Morphological assessment of agro waste-based geopolymer concrete has revealed that the use of agricultural waste materials as a source of aluminosilicate can produce concrete with unique microstructural characteristics. Studies have shown that agro waste-based geopolymer concrete exhibits a more compact and denser morphology compared to traditional concrete, with a lesser porosity and a finer pore size distribution. This can lead to improved mechanical properties and better resistance to environmental degradation. Also, they contain minerals such as gehlenite, feldspathoids, and zeolites, which influence the strength and durability of the material.

Additionally, morphological assessment has shown that the incorporation of agro waste materials can result in the formation of new phases, such as calcium silicate hydrate (C-S-H) and zeolites, which contribute to the strength and durability of the concrete. However, advance investigation is required to fully understand the microstructural characteristics of agro waste-based geopolymer concrete and their impact on the material's properties and performance. Overall, agro waste-based geopolymer concrete has the potential to revolutionize the construction industry by providing a sustainable and eco-friendly alternative to traditional concrete. Further research and development are needed to overcome the challenges and make this material a viable option for large-scale construction projects.

7.1 Guidelines for future research studies

According to the comprehensive review study, industrial and agricultural waste ash-based alkali-activated binders both perform similarly in terms of performance. Nevertheless, the use of agricultural waste ashes especially SCBA and BPA in the creation of alkaline activator binders is not very common.

As mentioned previously, there is presently no standardized testing procedure or design mix methodology for the making of geopolymer concrete. Future research should emphasis on evolving standardized measures and requirements for the testing and production of geopolymer concrete to enable better comparison of results across different studies.

Although some research has been done on the short-term durability of geopolymer concrete, more research is needed to understand its long-term performance and durability. This includes investigating factors such as creep and shrinkage, as well as the impact of environmental exposure over time. Also, more research is desirable to comprehend the full environmental impact of geopolymer concrete production. This includes investigating the greenhouse gas emissions and other environmental impacts, as well as exploring the potential for using combination of agro waste materials as a source of raw materials.

Geopolymer concrete can be made using a variety of different raw materials, and further research is needed to optimize the use of these materials. This includes examining the impact of using various types and proportions of raw materials on the characteristics and performance of the concrete. Future research should also focus on exploring how geopolymer concrete can be achieved and utilized in large-scale construction projects.