1 Introduction

Concrete is a substance that finds extensive usage across the Earth and is among the most widely employed materials. It has allowed a tame nature and is the foundation of modern development. However, it is causing our blue and green world to become greyer. In 2020, scientists approximated that the mass of human-made materials surpassed that of all living organisms on the planet, encompassing individuals, bacteria, plants, and animals, combined. One of these human-made culprits is Portland cement, the key ingredient in concrete that binds all other ingredients together. Its production is very energy intensive (Rashad 2014) it emits carbon dioxide and other greenhouse gases (H.M.T 2022; H.M.T 2023; Tanu et al. 2023), it causes soil erosion and noise pollution and it adversely affects air quality (Singh et al. 2018). Researchers around the world are trying to find an alternative to traditional cement concrete that is less destructive to our planet. One promising material is geopolymer concrete. It completely replaces Portland cement with waste industrial products. It can also be much stronger and perform better than traditional concrete. Industrial by-products are minimally processed natural materials instead of Portland cement. If left untreated, the disposal of industrial waste poses significant challenges and can have adverse effects on the environment so, using them significantly to minimize the environmental impact of concrete in terms of carbon emissions is an excellent idea. Some of the waste and low-energy materials are Fly ash. GGBS, Metakoalin, etc. (Mehsas et al. 2022). Fly ash is the residual by-product that remains after the operation of thermal power plants. It is mainly composed of Majorly Alumina and silica. Metakaolin is produced by Kaolin industries after the burning of calcined clay. GGBS is a left residue from the Blast furnace (Yin et al.2018). GGBS possesses a significant amount of calcium oxide, resulting in notable enhancements in concrete strength and durability of concrete. Every one of these raw materials performs differently and produces a different type of geopolymer concrete. These materials having alumina and silica are made to react with Na2Sio3 and NAOH as alkaline activators (Singh et al. 2015). The various reaction products formed for the precursor material Fly ash are found to be alkali silicate hydrate gel, Meanwhile, GGBS is calcium silicate hydrate gel (Srinivas et al. 2020), and also for a source material metakaolin has a high amount of alumina-silica gel. (Afia Sharmin et al. 2017). The silicon-oxygen silicon bonds break down and aluminum atoms penetrate them to form alumina silicate gels. With more alkali, these gels harden into a geopolymer concrete. The reactions involved in geo-polymerization are shown in Fig. 1. A lot of concrete has been experimenting with this material for large projects. The construction of the airport in West Well Camp, Australia, involved the utilization of over 40,000 M3 of GPC for its runway, resulting in a significant reduction of approximately 6,600 tons of carbon dioxide emissions. This concrete is also used at the University of Queensland, Australia around 33% of the floor plates in the four-story building were made of this concrete. In America, special high-strength geopolymer concrete has been used for airfield and road repairs. Tanu et al. (2023) developed ambient cured GPC with Agro-industrial waste, The authors concluded that 10 M GPC mixes achieved 43–66 MPa for 28 days of age and also noted that strong correlation b/w Compressive and split tensile strength by linear regression. Naga Jothi et al. (2022) reported the water absorption of GPC exhibits a lower percentage of loss compared to OPC. Sathish Kumar et al. (2021) reported that TGPC has superior characteristics concerning chemical attacks. Bellum et al. (2020) study revealed that the GPC with fly ash and GGBS demonstrated a dense structure, providing evidence of the existence of geopolymer gel in the matrix. Kamath et al. (2021) reported the presence of ternary mixtures resulted in a uniform and compact microstructure, characterized by the formation of different types of geo-polymeric gels (Table 1).

Fig. 1
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Geo-polymerization reactions (Khale 2007)

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Table 1 Physical properties
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This concrete has good strength properties and they are also resistant to various alkalis, salts, and corrosive substances. They also have high sulfur resistance due to the lack of calcium compounds in their structure. Geopolymers have excellent waterproof properties. They have better resistance to freezing and thawing and can withstand up to 1000 degrees Celsius (Hassan et al.2019a, b). Mugahed Amran et al. (2021) reported that geopolymer concrete has excellent resistance against aggressive environmental conditions compared to OPC Concrete due to its dense and compact structures. Muslum Murat Maras (2021) reported that the addition of steel fibers up to 2% increased compressive strength by up to 96%. Albitar et al. (2017) noticed that GPC has better resistance to acid and sulphate attacks compared to OPC. Muslum Murat Maras (2021) reported that the inclusion of fibers in geopolymer mortar has higher resistance against brittle failure than OPC mortar. Muslum Murat Maras (2021) reported that the strength of geopolymers developed with 8 M alkali activator solution with 5% Ca (OH)2 were found to be high compared to other mixes in the study. Geopolymer concrete will help us to stop extracting raw materials by utilizing these waste products. Despite its superior characteristics compared to traditional cement concrete, GPC has not gained widespread adoption due lack of standardization of IS codes, also handling of alkaline activators, and sensitive polymerization reactions. Thus, due to the usage of industrial by-products ternary blended geopolymer concrete solves environmental issues proving to be an economical and futuristic material to produce sustainable green concrete. This concrete can make sustainable construction materials, reduce CO2 emissions, reduce global warming, and become an eco-friendly material (Amran et al. 2020).

The main novelty of this current research work is the influence of the effect of ternary blends on microstructural and durability properties of geopolymer concrete and also the effective utilization of various industrial admixtures as prime source material in the development of sustainable ternary blend geopolymer concrete production to reduce disposal problem (Tables 2, 3, 4).

Table 2 Chemical composition
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Table 3 Crimped steel fibers properties
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Table 4 Physical properties of Natural sand and coarse aggregates
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2 Materials and Methods

2.1 Materials

High calcium Fly ash with SiO2 of 60.42% and Al2O3 of 25.74% as the major chemical composition collected from BTPS thermal power plant, Ballari. Fly ash has good long-term strength and durability properties in concrete. GGBS with SiO2 of 35.80% and Al2O3 of 19.60% are major chemical compositions collected from JSW Ballari, which is leftover residue from the blast furnace. Metakoalin with SiO2 of 58.36% and Al2O3 of 35.28% as major chemical composition brought from a local supplier. OPC 43 Grade cement is used for making conventional cement concrete sponsored by Shree Cements Ltd. Flakes of sodium hydroxide are utilized, while the foundry-grade sodium silicate liquid comprises 14.12% Na2O, 33.89% SiO2, and 52% water by mass. This solution is used as an activator in the ternary mix. Locally available conventional crushed aggregates and sand as per IS383-1970 are used in this study. The EDS, SEM, and XRD images of the above materials are depicted in Figs. 2, 3, and 4, respectively. The SEM image of fly ash shows that its particles are spherical and contribute to the workability of concrete. Additionally, the EDS image displays alumina, silica, and other oxides as the major elemental composition. The XRD spectrum of fly ash in Fig. 4 exhibits crystalline components such as Quartz and Mullite. The SEM analysis of GGBS indicates that the particles have an irregular and angular shape. Moreover, according to the results obtained from EDS analysis, the major elemental components of GGBS primarily comprise silica, alumina, calcium, and magnesium. The X-ray diffraction (XRD) analysis of GGBS indicates the presence of Quartz, Alumina, and calcite. Meanwhile, the scanning electron microscope (SEM) images of Metakoalin depict angular particle shapes and platy in shape. Moreover, the EDS reveals that the major elemental composition of Metakaolin is alumina and silica. The XRD spectrum illustrates the presence of crystalline components such as Quartz and Anatase (Figs. 5, 6, 7, 8).

Fig. 2
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SEM and EDAX Images of Fly ash

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Fig. 3
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SEM and EDAX Images of GGBS

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Fig. 4
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SEM and EDAX Images of Metakaolin

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Fig. 5
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XRD images of FA-GGBS-MK

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Fig. 6
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Ambient curing of TPGC specimens

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Fig. 7
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Regression between Compressive strength and split tensile strength

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Fig. 8
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Regression between Compressive strength and flexural strength

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2.2 Mix Proportion

In this study, the mix proportion of geopolymer concrete is based on the trial and error method and as per previous works of literature (Rangan 2006). The mix of grade M40 is designed and OPC concrete as a reference mix is also cast as per the specification of (IS10262-2009). Fly ash, GGBS, and MK are mixed with aggregates in dry form and steel fibers from 0 to 1.5% are added to the mix. In Ternary Blends the addition of Metakoalin in fly ash, and GGBS increases the strength of concrete. This is due to Metakoalin being a highly pozzolanic reactive material which gives early strength resulting in the formation of CASH gel. These materials are mixed in a mixer for 4–5 min till a homogeneous mixture is obtained with fibers uniformly distributed without causing a balling effect in concrete. The solution-to-binder ratio considered in this study is 0.40. Sodium hydroxide solution of 10 M is prepared 24 h before mixing in concrete as it gives out lots of heat due to an exothermic reaction (Kumar et al. 2017; Mehrzad et al. 2017) after that sodium silicate liquid is mixed in a ratio of 1:2 into the concrete. The other Molarity of Sodium hydroxide solution experimental work of the author was presented elsewhere (Khalid et al. 2023, 2021). Furthermore, this solution is poured into the mixture and mixed till homogeneity is obtained. At last, the prepared geopolymer concrete is cast into cubes and exposed to ambient curing and OPC concrete is kept for curing in water. Table 5 displays the mix proportions utilized in the study.

Table 5 Mix Proportion in Kg/m3
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3 Results and Discussion

3.1 Fresh Properties

3.1.1 Workability

It is defined as the ease with which the concrete can be transported, placed, and compacted, without losing its homogeneity. A slump test is conducted to explore the fresh properties of this concrete. A total of 20 mixes were tested with different variations in fibers including traditional ordinary cement concrete. The designated Mix ID for all the mixes with slump values is shown in Fig. 9. The inclusion of fibers is found to result in a decrease in the slump value of Ternary blended geopolymer concrete (Khalid et al. 2023). The slump value of TGPC is low when compared to OPC Concrete this is due to the highly viscous alkali activator solution. However, much care is to be taken during the casting of specimens with the addition of a superplasticizer to get the desired workability of concrete (Table 6).

Fig. 9
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Slump value

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Table 6 Validating equation Based on Previous works of literature
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3.2 Compressive Strength

It was carried by a compression testing machine with a 2000 kN capacity (Mehrzad et al. 2017) as per the guidelines of IS 516:1956. The prepared cubes of size 150 mm with different mix proportions and fiber volumes were tested. It was observed that the strength of concrete increases with an increase in fiber volume. The fibers will arrest the propagation of cracks (Carrico et al. 2018; Kotop et al. 2021). The mix TGPC3-4 (FA60G25MK15) at 1.5% of steel fibers has a strength 6.25% higher than compared with reference ordinary cement concrete (TGPC4-4), this may be due to the effective dissolution of alumina-silica ions in alkali activators and undergoing pozzolanic reactions to form C–A–S–H Gel. Figure 10 illustrates the concrete strength at 28 days and 90 days. To know the relationship between Compressive strength (Fc) and split tensile strength (Ft) a graph is drawn with a linear equation shown in Fig. 7. A good correlation linear equation Fc = 0.1262Ft − 1.8202 having R2 = 0.953 is observed b/w Compressive strength (Fc) and Split tensile (Ft).

Fig. 10
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Compressive strength for 28 and 90 days

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3.3 Split Tensile Strength

A 2000kN capacity compression testing machine (CTM) was used to know the split tensile strength as per the guidelines of IS 5816:1999. The cylindrical specimens of size 150 mm diameter and 300 mm diameter with different mix proportions and fiber volumes were tested. The load is applied till the specimen fails. The maximum split tensile strength revealed for TGPC3-4 (FA60G25MK15) at 1.5% of steel fibers has been 4.21Mpa. Furthermore, the strength increased by 6.32% with the reference Mix. This due to the addition of steel fibers will delay the propagation of cracks thereby increasing the split tensile strength of concrete, Fig. 11 illustrates the split tensile strength at 28 days and 90 days.

Fig. 11
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Split tensile strength for 28 and 90 days

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3.4 Flexural Strength

It was carried by a UTM 100Ton capacity as per the guidelines of IS516:1956. The Beam specimens of size 500 × 100 × 100mm with different mix proportions and fiber volumes were tested. The single point loading is applied till it the specimen fails. It is observed that the flexural strength increases with the increase in fiber volume significantly. Similarly, mix TGPC3-4 (FA60G25MK15) at 1.5% of steel fibers has exhibited the highest flexural strength of 5.56 MPa. It was observed that the strength increased by 5.1% with the reference Mix. Figure 12 illustrates the strength at 28 days and 90 days. To know the relationship between Compressive strength (fc) and flexural strength (ff) a graph is drawn with a linear equation shown in Fig. 8. A good correlation linear equation Fc = 0.0273Ff + 3.5542 having R2 = 0.9413 is observed b/w Compressive strength and Flexural strength (Fig. 13).

Fig. 12
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Flexural strength for 28 and 90 days

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Fig. 13
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Failure pattern for different fiber volume

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3.5 Pulse Velocity Test

It is the most useful NDT test that can be conducted for concrete. UPV is generally done to check the quality of concrete by determining the velocity by measuring the pulses passing through the concrete. By knowing the distance ‘L’ and the transmit time ‘T’, we can calculate the pulse velocity in concrete. The better the quality of the concrete, the higher its pulse velocity will be, Lower pulse velocity indicates voids or non-uniformity in the concrete. UPV has many applications such as determining the Quality variation of concrete, thickness variation, measuring surface crack depth, and also knowing the homogeneity of the concrete. Figure 14 illustrates the ultrasonic pulse velocity values of ternary blended geopolymer concrete and OPC concrete 90 days of the curing period. It is observed that an increase in Metakaolin content up to 15% has shown more strength and UPV values for ternary blended GPC, this is due to the effective geo-polymerization that has taken place. Similar results were observed by Muralidhar Kamath et al. (2021) and the results of OPC Concrete were satisfactory indicating good quality concrete (Fig. 15).

Fig. 14
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Ultrasonic pulse velocity values

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Fig. 15
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Water Absorption test

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3.6 Water Absorption

Water absorption is carried out for ordinary cement concrete and geopolymer concrete as per IS 2185:2005. Higher water absorption indicates there may be pores or voids in concrete. Lower water absorption indicates the structure is dense and compact and complete polymerization takes place giving rise to a compact structure. After 24 h of immersion in water, the cubes are taken out, wiped, dried and weighed as W1. After that specimens are kept for 24 h at 100 °C in an oven and weighed as W2. Figure 16 presents the outcomes of the water absorption test and the results were less than 10% which is a permissible value for good concrete. The highly dense compacted structure with all the fine particles of Fly ash, GGBS, and Metakaolin located close together along steel fibers has a lower porosity than ordinary cement concrete (Satish et al. 2021). These results were similar to Sathia et al. (2008)

$${\text{Water}}\;{\text{Absorption}}\;{\text{in}}\;\% = \frac{W2 - W1}{{W1}}{ \times }100$$
Fig. 16
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Water Absorption Results

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3.7 Acid Attack

The mass of ordinary cement concrete and geopolymer concrete cubes is recorded after a curing period of 28 days. After that, it is kept in 5% of the sulfuric acid solution for 90 days (Al-Swaidani et al.2017). To maintain the uniformity and concentration of acid, the solutions are checked by pH value and are changed monthly. After 90 days the cubes are taken from the sulfuric acid solution and tested for change in visual appearance, weight and compressive strength in surface dry condition when exposed to acid. It was observed that ternary blended geopolymer concrete has excellent resistance against destructive acid attacks in comparison with ordinary cement concrete as shown in Figs. 17, 18. TGPC experienced a maximum weight loss of 5.5%, whereas OPC encountered a higher weight loss of 15.72%. Moreover, TGPC exhibited a significantly lower maximum reduction in compressive strength at 19.26% compared to OPC, which experienced a higher maximum reduction of 49.55%. This is because OPC Concrete is more susceptible to acid attack due to its high calcium content which leads to the deterioration of cement paste by the formation of gypsum and ettringite. (Tahir et al.2022). Figure 17 depicts the reaction between OPC Concrete and sulfuric acid.

Fig. 17
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Reaction b/w OPC with Sulfuric acid

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Fig. 18
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Specimens after the Acid attack a OPC b TGPC

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3.8 Sulphate Attack

After 28 days of curing the mass of ordinary cement concrete and geopolymer concrete cubes is recorded. After that, for a duration of 90 days, it is immersed in a solution containing 5% sodium sulphate. After 90 days the cubes are taken from the sodium sulphate solution and tested for change in visual appearance, weight and compressive strength in surface dry condition when exposed to sulphate attack. The concrete demonstrated favorable performance, as no notable alterations were observed in terms of surface condition, weight, and compressive strength. The deterioration is much less when compared to OPC (Al Bakri et al. 2012). The reduction in compressive strength of TGPC specimens was below 13.87%, whereas for OPC specimens it was almost 15%. This reduction in strength is due to the leaching of NaOH when it comes into contact with sodium sulphate. Similar results were observed by Sathish Kumar et al. (2021). The above results were also supported by Albitar et al. (2017) where the reduction in compressive strength for OPC Concrete was 15.4% (Figs. 19, 20, 21, 22, 23).

Fig. 19
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Sulphate attack a Specimens kept in sulphate solution b Specimens after 90 days of exposure

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Fig. 20
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Percentage loss in weight under Acid and Sulphate

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Fig. 21
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Percentage loss in strength under Acid and Sulphate attack

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Fig. 22
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RCPT test setup

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Fig. 23
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RCPT Results

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3.9 Rapid Chloride Ion Permeability Test (RCPT)

This instrument is designed to carry out testing as per ASTM 1202 standard. This method is widely accepted as a standard approach to electrically assess the concrete's resistance to chloride ion permeability. The instrument is supplied with a complete four set of cells connecting cables, temperature sensors, a desiccator, a vacuum pump, etc. The rapid chloride ion penetration tester has four channels and at a time four samples can be tested by applying an electrical potential across the specimens. The sample is coated with epoxy and dehydrated. The sample is placed into a test cell and filled with NaCl and NaOH solution. Voltage is applied and current is measured every 30 min for six hours. The results of both TGPC and OPC concrete indicate moderate chloride penetrability. Furthermore, it was observed that the addition of fibers increases the charge values, this is because the inclusion of steel fibers leads to an inaccurate assessment of concrete chloride diffusion. Similar results were reported by Ganesan et al. (2015). The total charge passed was calculated by the equation below

$$Q = 900\left( {I_{0} + 2I_{30} + 2I_{60} + \, - - - - - - - - \, + 2I_{360} } \right)$$

3.10 Microstructural Study

Microstructure analyses are instrumental in confirming the geopolymer reaction and assessing the overall excellence of the resulting products. This study revealed that the ternary blended GPC demonstrated a dense structure, confirming the presence of geopolymer gel, i.e., calcium silicate hydrate (C-S–H) as illustrated in Fig. 24. These gels are responsible for imparting strength to the concrete. To determine the mineral phases, present in the ternary blended GPC, an X-ray diffraction analysis was conducted. The results revealed the existence of Quartz and C-S–H gel, as evidenced by the presence of crystalline phases within the range of 20 to 30 degrees, as depicted in Fig. 24

Fig. 24
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SEM and XRD of concrete sample

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4 Conclusion

Based on the above experimental study, the following conclusion is made.

  1. 1)

    The results of the workability test indicate a decrease in slump values as the fiber content increases using alkali activators which are more viscous than water making a concrete cohesive, however, slump value can be increased with the addition of Superplasticisers. Ordinary cement concrete possesses a higher slump value than TGPC.

  2. 2)

    Mix TGPC 3–4 (FA60G25MK15) possesses maximum mechanical properties when compared to other mixes in the study. The max compressive strength was 49.8 MPa, Max Split tensile strength was 4.21 MPa and Max Flexural strength was 5.56 MPa for 10 molarity of sodium hydroxide solution and also evidenced by the formation of geo-polymeric gel for giving strength to the concrete.

  3. 3)

    The experimental findings exhibit a robust correlation with an R2 Value of 95% for Compressive vs. tensile strength and 94% for Compressive vs. flexural strength for the proposed model equations developed in the current study. Hence these models, when applied, will prove valuable in enhancing the strength of geopolymer concrete.

  4. 4)

    OPC concrete has undergone maximum deterioration due to the de-calcification of calcium alumina silicate hydrate gel, which leads to the deterioration of cement paste by the formation of gypsum and ettringite. TGPC has excellent resistance to sulfuric acid due to the low calcium content in Fly ash. Hence, based on the conducted study, it can be inferred that TGPC exhibits superior durability characteristics compared to traditional concrete. Furthermore, the inclusion of fibers has enhanced the long-term properties of TGPC.

  5. 5)

    XRD analysis provided evidence of the development of a polymeric structure characteristic of calcium sodium aluminosilicate, which plays a vital role in imparting strength and essential engineering properties to TGPC

  6. 6)

    Both TGPC and OPC were almost similar concerning chloride ion penetration as indicated by the RCPT Value as moderate chloride ion penetrability.

  7. 7)

    This concrete solves environmental issues such as reducing the CO2 emissions and disposal problems of industrial waste products by utilizing this concrete giving rise to green concrete.