1 Introduction

In recent years, significant advancements have been made in various fields toward achieving sustainability and combating climate change (Gandolfo et al. 2022). These advancements extend to key sectors such as construction, transportation, and energy production, which play crucial roles in the global pursuit of sustainability. The escalating industrialization, rapid population growth, and technological advancements of the past few decades have led to increased energy consumption (Adediji et al. 2023). The construction sector, for instance, is now recognized as a vital player in the fight against climate change, as it accounts for nearly 40% of CO2 emissions (Švajlenka and Pošiváková 2023). The sustainable development of the construction sector, which accounts for significant resource consumption, electrical power usage, water consumption, landfill waste generation, and greenhouse gas emissions, is of paramount importance in the pursuit of sustainability. Concrete, as a widely used material, poses challenges due to non-renewable raw materials and their ecological footprint during production (Fonseca and Matos 2023). Another critical aspect in the transition toward sustainability is the transformation of the energy production sector, with a focus on cleaner and renewable energy sources. Photovoltaics, including Si and multijunction solar cells, have demonstrated remarkable efficiency values, showcasing their potential to significantly contribute to sustainable energy generation (Pirrone et al. 2022). Additionally, utilizing carbon materials derived from the hydrothermal recycling of waste tires highlights the importance of end-of-life waste management (Schmitz et al. 2022). The global population is projected to increase to approximately 9.8 billion by 2050; hence, there is a growing demand for sustainable solutions (Eisa et al. 2022). This necessitates rethinking traditional construction materials and processes to meet the needs of the future, while minimizing resource consumption and greenhouse gas emissions.

The rise in urbanization has led to the emergence of the building and construction sector, which in turn has raised the demand for cement (Singh et al. 2022). OPC has long been used as the primary binding material in the production of concrete, but the environmental concerns associated with its production are well known. A substantial amount of CO2 is emitted due to the calcination of limestone and the burning of fossil fuels during OPC production (Liu et al. 2016; Singh and Subramaniam 2019). Furthermore, the calcination of lime requires temperatures of about 1400–1500 °C, which deplete a lot of natural resources and use a substantial amount of energy (Thakur and Bawa 2022). Globally, the cement industry is liable for 5–8% of all CO2 emanations (Kajaste and Hurme 2016; Farooq et al. 2022). A rough estimate suggests that carbon fuel combustion results in about 0.40 tons of CO2 emissions, while 0.55 tons of chemical CO2 are released during the processing of 1 ton of Portland clinker. On simplification, around 1 ton of CO2 is generated in general (Davidovits 1994; Sharma et al. 2022a). CO2 is the most significant greenhouse gas contributor, responsible for about 65% of the warming effect. It is estimated that OPC production contributes around 1.35 billion tons per year to global greenhouse gas emissions (Malhotra 2002). Materials like FA, wood ash, GGBS, silica fume, rice husk ash, and other low-energy, low-carbon products are viable alternatives for addressing this issue (Nath and Sarker 2015; Pasupathy et al. 2017).

GPC is considered a revolutionary development in the world of concrete technology. When compared to traditional cement, the production of geopolymer cement results in a reduction of CO2 emissions up to 80% by eliminating the need for calcium carbonate (Junaid et al. 2017). Geopolymer cement cures more quickly than Portland-based cement. The majority of their strength is attained within 24 h (Davidovits 2013). GPC outperforms normal concrete in terms of mechanical and thermal aspects (Zhao et al. 2019; Qu et al. 2020). This concrete is an environmental friendly and sustainable alternative to traditional PC concretes (Ambikakumari Sanalkumar and Yang 2021; Gill et al. 2023). GPC shows high durability with the ability to resist chloride penetration and acid attack, which are some of the basic requirements for durable performance (Radahakrishnan et al. 2017). Davidovits, in 1978, suggested that binders could be developed by a polymeric reaction of alkaline solutions with aluminum (Al) and silicon (Si) in geologically derived primary sources or industrial by-products such as FA, GGBS, and so on (Davidovits 1999; Provis 2014). These Si and Al are polymerized into molecular chains and used as binders after being dissolved in an alkaline activating solution (Abdul Aleem and Arumairaj 2012). Geopolymerization is a process that involves a heterogeneous reaction between alkali metal silicate solution and aluminosilicate oxides at mild temperatures and high alkalinity to produce a polymeric structure that is either amorphous or semi-crystalline in nature, with Si–O–Al and Si–O–Si bonds (Dimas et al. 2009).

FA disposal is becoming increasingly difficult, with only 15% of FA now being used for high-value-added uses, such as concrete construction, and the rest is being used as landfills. FA is effectively used in cement concrete production because it provides technical benefits while also decreasing pollutants (Howladar and Islam 2016; Bhatt et al. 2019). GGBS is extremely cementitious and rich in calcium silicate hydrates (CSH) that enhance the strength, durability, and aesthetic quality of concrete (Patel and Shah 2018). Therefore, there is a pressing need to encourage the use of GGBS due to its extensive benefits. The addition of limestone powder, dolomite, or quick lime to GGBS can intensify the Ca–OH bonds, which enhance the early-age strength of the concrete without altering its pH (Saranya et al. 2019). Dolomite, also referred to as calcium magnesium carbonate (CaMg (CO3)2), is a type of carbonate mineral obtained by grinding sedimentary rock to produce the mineral dolostone. Due to its superior surface hardness, density, high purity, flame-retardant properties, good compression strength, weathering resistance, and shearing characteristics, dolomite is a desirable construction material (Barbhuiya 2011; Agrawal et al. 2021). Geopolymerization of Class F FA requires some constraints, such as the application of exogenous heat or the presence of calcium content, to speed up the chemical reactions involved (Nath and Sarker 2015; Sharma et al. 2022b). Various studies suggest that adding high-calcium components to FA-based geopolymers significantly increases their strength properties (Yip et al. 2005; Cohen et al. 2019). The amount and source of calcium in the FA influences the characteristics of the resultant geopolymer. The existence of calcium compounds in the raw material can enhance the mechanical characteristics of the geopolymers due to the cohabitation of the geopolymeric gel and the calcium aluminum hydrate (CAH) and calcium silicate hydrate (CSH) gels (Yip et al. 2005; Buchwald et al. 2007). GGBS and dolomite are rich in calcium (Ca) content and hence can be used with geopolymer binder to improve the strength and durability of the GPC.

2 Research significance

Solid waste disposal has become the world’s top environmental priority. Waste products geopolymerization can assist in the resolution of current environmental issues such as water, soil, and air pollution (Thakur and Bawa 2022). On the contrary, the construction industry contributes significantly to environmental pollution, particularly through the manufacture of its most widely used product, cement (Ahmed et al. 2022; Wong 2022). As a result, achieving sustainability in the construction industry has become critical, and this research is a step forward in terms of sustainable development and natural resource optimization. With the use of FA, GGBS, which are industrial by-products, and dolomite, which is a low-cost material, two very major problems of this time, i.e., safe discarding of industrial wastes and minimization of environmental pollution by the construction industry, can be handled (Prabha et al. 2022; Asghar et al. 2023). Previous studies have extensively explored the use of either FA or GGBS as cementitious binders in GPC (Pasupathy et al. 2017; Reddy et al. 2018; Qu et al. 2020; Sharma et al. 2022b). However, limited attention has been given to the incorporation of dolomite. Dolomite is a low-cost material that can be sourced easily, making it an economically viable option for GPC production (Prabha et al. 2022). This investigation aims to explore the potential benefits of incorporating dolomite in a ternary blend of FA, GGBS, and dolomite as binders in GPC and assess their compatibility, which has not been previously studied. Additionally, the research emphasizes studying and quantifying the benefits obtained, on the mechanical and durability aspects of the developed GPC. By assessing the ternary blend performance, in terms of strength, durability, and other relevant properties, this research provides valuable insights into the potential advantages and limitations of using these materials in combination.

3 Experimental program

3.1 Materials

The materials used for the manufacturing of FA-based GPC were low-calcium FA (Class F), GGBS, dolomite, aggregates, alkaline activators, and superplasticizer (SP). Class F FA was the principal binder in all the GPC mixes, and it was blended with GGBS and dolomite in different proportions. The control GPC mix used in this investigation was made using 100% FA, coarse aggregate, fine aggregate, alkaline solution, and SP. For the remaining mixes, the total cementitious content of the control GPC mix was modified by replacing FA up to 20% with GGBS and dolomite in various percentages. FA used in the manufacturing process was collected from a thermal power plant, Rajpura, in accordance with IS 3812 (Part-1) (2003). GGBS conforming to IS 12089 (1987) and dolomite passing through 75 µm were also utilized in the production of GPC, both of which were obtained from a nearby chemical mill and store. The physical and chemical properties of FA, GGBS, and dolomite are illustrated in Table 1. Locally available fine aggregates comprising river sand with a maximum particle size of around 4.75 mm, specific gravity of 2.62, and fineness modulus of 2.99 conforming grading zone II as per IS 383–2016 (Standard 2016) were used. Coarse aggregates having specific gravity of 2.68 and fineness modulus of 7.08 were used in accordance with IS 383–2016 (Standard 2016). The aggregates passing through a 12.5-mm sieve and retained on a 10-mm sieve and aggregates passing through a 10-mm sieve and retained on a 4.75-mm sieve were utilized in proportions of 40:60, respectively. Figure 1 represents the gradation curve for both fine and coarse aggregates. Blend of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) solution was preferred as an alkaline solution. Na2SiO3 with a specific gravity of 1.53 and SiO2/Na2O ratio of 1.5 and NaOH with a specific gravity of 1.33 and 12 M concentration were used during the manufacturing process. The hydroxide to silicate ratio was maintained at 1:2. A commercial grade Na2SiO3 solution and NaOH flakes were acquired from a nearby supplier. The NaOH solution was prepared 24 h before casting by dissolving 98% pure solid flakes in water. Since the dissolution of NaOH flakes into the water is an exothermic reaction, it requires 24 h to attain the room temperature. Na2SiO3 was added to this NaOH solution just half an hour before mixing. The viscosity of the alkaline solution is greater than that of potable water. When these alkaline solutions are employed in the production of GPC, they tend to hinder the workability of the concrete (Pavithra et al. 2016). Therefore, a polycarboxylic ether-based SP was utilized to enhance workability and retain the desired slump value of the concrete mixture.

Table 1 Physical and chemical properties of FA, GGBS, and dolomite
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Fig. 1
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Fine and coarse aggregates gradation curve

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3.2 GPC mix proportions

In total, six mixes were formulated at varying percentages of FA, GGBS, and dolomite. Mix with 100% FA was used as a reference mix or control mix. For all mixture designs, a constant alkali/binder ratio (a/b) of 0.45 and binder content of 450 kg/m3 were utilized. Combination of Na2SiO3 and NaOH solution with silicate to hydroxide ratio of 2 (Na2SiO3 / NaOH) was used as an alkaline solution for activation, and the concentration of NaOH solution was maintained as 12 M. The SP proportion was held constant at 1% of binder for all mixes. Table 2 enlists the nomenclature of various GPC mixes, and Table 3 demonstrates the mix proportion of all GPC mixes. Due to the lack of standardized guidelines for GPC, the mix design procedure adopted in this study was inspired by prior research done on FA-based GPC. The basic mix proportion for the control mix was taken from the previous studies (Patankar et al. 2015; Pavithra et al. 2016; Reddy et al. 2018). The preparation of the GPC mixes was done in two stages. Firstly, the binders were mixed thoroughly with coarse aggregates and sand in saturated surface dry condition for 5 min in a tilting-type power-operated rotary concrete mixer before. After that, an alkaline solution and SP were added gradually to this dry mix of binder, coarse, and fine aggregates and further mixed to ensure a uniform consistency of the mix. Finally, the fresh GPC mix was poured into the molds and secured with the poly wrap to prevent moisture loss. After casting, all samples were labeled with their corresponding mix designations and oven-cured at 65 °C for 24 h before being demolded.

Table 2 Mixes nomenclature
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Table 3 Quantity of various binders used for each mix preparation in kg/m3
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3.3 Workability

3.3.1 Slump test

The slump test examines the consistency of freshly prepared concrete prior to its hardening and also tells about the amount of water required for achieving a desired workability. The slump test for all the mixes was performed in accordance with IS 1199 (1959). The SP dosage was kept constant (1% of binder) throughout the experiment, and the slump value was measured.

3.4 Mechanical strength tests

3.4.1 Compressive strength

The compressive strength testing was performed conforming to Indian Standard IS 516 (1959). Cubes measuring 100 mm * 100 mm * 100 mm were cured for 7, 28, and 56 days, and then tested for compressive strength.

3.4.2 Split tensile strength

The split tensile strength of GPC mixes was conducted in accordance with IS 5816 (1999). The 100 * 200 mm cylindrical specimens were prepared for testing the split tensile strength at 7, 28, and 56 days of curing.

3.5 Durability tests

3.5.1 Initial surface absorption (ISA)

Initial surface absorption test (ISAT) provides a low-pressure assessment of the concrete surface water absorption. This test examines the rate of water flow into a concrete capillary pore network. Flow volume is measured by computing the length of flow along a known dimension capillary. The ISA of GPC was determined by testing 150 mm*150 mm*150 mm cube specimens at 28 and 56 curing days confirming to BS 1881–208 (1996). Specimens were subjected to oven drying to achieve a consistent weight (i.e., not more than 0.1% weight variation during any 24-h drying period) prior to the test and placed in a cooling cabinet (desiccator) at the temperature of 20 °C to cool them to the room temperature. For each type of concrete mix and each curing age, three distinct specimens were evaluated. A gasketed circular cap with the smallest surface area of 5000 mm2 is sealed to the concrete surface in the test technique. The cap outflow is attached to a capillary tube, and the cap is filled with deionized water from a reservoir. After isolating the reservoir, the displacement of a meniscus along the capillary tube is measured to estimate the rate of water absorption into the concrete at 200-mm pressure head. Readings are noted at 10 min, 30 min, and 60 min.

3.5.2 Capillary suction absorption (CSA)

Capillary suction absorption test (CSAT) determines the water absorption rate of concrete by monitoring the increase in mass of a specimen as a function of time when only one surface of the sample is immersed in water. A small amount of capillary suction is responsible for most of the unsaturated concrete water infiltration at the first contact with water. In unsaturated concrete, capillary rise is a major factor in the pace at which water or other liquids may enter the concrete. In this test, the exposed side of the concrete capillary pores is examined for water infiltration and the results are recorded. Three discs, each 50 mm thick and 100 mm in diameter, were used and conditioned in accordance with ASTM C1585-13 (2013) and aged for 28 and 56 days before testing. When the mass variation of the succeeding two measurements of the sample fell below 0.1%, the sample was put in a desiccator to cool down and prevent moisture absorption from the environment after oven drying at 105 °C. The circumferential area of the disc was covered with epoxy and sealed with polyethene sheets to avoid evaporation from the surface that was not exposed to water. Before immersing the specimens in water over a support, their mass was recorded. The mass of the samples was measured at intervals of 1, 5, 10, 20, 30, 60 min, and every hour up to 6 h. After the first 6 h, we took readings once a day for the next three days, then three readings at least 24 h apart for days four to seven, and a final reading at least 24 h after the reading on day seven. The sorptivity (mm/s) of the mixtures was determined by plotting the correlation between water absorption and the square root of time.

3.6 Non-destructive tests

3.6.1 Ultrasonic pulse velocity (UPV)

According to the UPV test method recommended by IS 516: Part 5 (2018), 100 mm * 100 mm * 100 mm cube specimens were tested on 7, 28, and 56 curing days prior to a compression test. This test instrument comes with a pulse generator, a set of two transducers in which one is a pulse emitter and the other is a receiver, and an electronic timing gadget. An ultrasonic pulse was induced into the cube specimen using an electro-acoustical transducer to determine internal cracks, defects, and homogeneity of the concrete mix. In order to further define the quality of the concrete, the time taken by the pulse wave to travel through the concrete specimens was precisely measured. Prior to pulse transmission, ultrasound gel was properly applied to any parallel sides of the cube except the casting side to properly transmit the electronic pulse from the specimen.

3.6.2 Electrical resistivity

All cylindrical specimens of 100 mm * 200 mm size were tested for electrical resistivity on 7, 28, and 56 curing days before their split tensile testing as per the electrical resistivity test method recommended by AASHTO–T 358 (2015). Four uniformly spaced (1.5 in.) probes are applied to the specimen in a line in this procedure. The current is supplied to the specimen via the two outer probes, and the inner pair of electrodes monitors the resulting potential drop. All of the probes are used on the same surface of the specimen. This test assesses the resistance of concrete to chloride ion penetration.

3.7 ANOVA test

A one-way ANOVA test was conducted, at a significance level of 5%, to examine the combined effect of all binders on the mechanical properties. The design specifications to perform one-way ANOVA are:

  • Each dataset is based on the number of days of curing at 7, 28, and 56 days, respectively.

  • The six mixes under consideration are FA100, G20D0, G15D5, G10D10, G5D15, and G0D20.

  • At 5% level of significance, the hypothetical statements under consideration are:

H0: There is no significant difference between the six sets of mixes for given number of days versus H1: There is some remarkable difference between the six sets of mixes for given number of days.

3.8 Reliability of strength

The significant variation in the mechanical strength at 7, 28, and 56 curing days, due to the inclusion of different binders, was further studied for its reliability. To assess the reliability of strength, a regression analysis was conducted using different percentages of GGBS and dolomite. The analysis focuses on exploring the R2 value, standard error, P value, and T statistics.

4 Results and discussion

The current investigation analyzed the effect of inclusion of GGBS and dolomite on both the strength and durability properties of GPC at temperature curing. Prior to the casting stage, the fresh property of GPC was examined by measuring the slump value. The strength properties in terms of compressive strength and split tensile strength, durability properties of GPC mixes such as ISA and CSA, and non-destructive tests such as UPV and electrical resistivity were evaluated. The outcomes of various tests performed are discussed below:

4.1 Slump test

The purpose of the test is to determine the workability of freshly prepared concrete. The desired workability parameter, in terms of slump value, has been achieved for each mix, as all concrete mixtures demonstrated slump in the 35–75-mm range. However, the mixes G20D0, G15D5, G10D10, G5D15, and G0D20, which were prepared with the inclusion of GGBS and dolomite, resulted in a 34.24%, 39.72%, 42.46%, 46.57%, and 49.31% reduction in the slump value when compared with the control mix FA100 (73 mm). The mixes with the higher percentages of GGBS and dolomite were stickier and cohesive. Due to the unsymmetrical particle shape and finer particle size of GGBS and dolomite compared to FA particles, these binders possess greater specific surface area, which elevates the water requisite of the GPC mix and reduces its workability. Low fluidity and flowability of the GPC mixtures have been observed where higher amounts of dolomite proportions were used due to higher water absorption than GGBS. The previous studies on GPC containing FA, GGBS, and dolomite also reported similar findings, indicating that both GGBS and dolomite possess irregular shapes (Ibrahim et al. 2022; Singh et al. 2023) and significantly finer particle sizes compared to FA (Ye et al. 2019; Liang et al. 2022). Additionally, it has been observed that the particle size of dolomite is even finer than that of slag (Ye et al. 2019). Figure 2 summarizes the slump values for different mixes.

Fig. 2
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Slump test results

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4.2 Compressive strength

Compressive strength of concrete is of immense value and is the measure of the amount of compressive load a concrete sample can bear. It is a reflecting and a realistic indicator for evaluating the overall performance of any concrete structure. The result of compressive strength tests shows that the inclusion of GGBS and dolomite as partial replacement of FA enhances the compressive strength of the concrete mixes. The mixes G20D0 and G10D10 show the maximum compressive strength values. Hence, the following sequence has been suggested for the GPC mixes based on the compressive strength test results: G20D0 > G10D10 > G15D5 > G5D15 > G0D20 > FA100. All GGBS and dolomite-blended mixes resulted in better compressive strength than the control mix FA100 at all mentioned curing days. As a result, there is an increment of nearly 53.21%, 35.47%, 48.28%, 32.02%, and 10.35% for the mixes G20D0, G15D5, G10D10, G5D15, and G0D20, respectively, compared to control mix FA100 (20.3 MPa) at 7 days of curing. Also, with the increase in curing days, the compressive strength improved for all GPC mixes due to pozzolanic behavior, pore structure refinement, and formation of C–S–H gel. At 28 days of curing, strength gain of 28.5714%, 45.0161%, 31.2727%, 41.196%, 27.2388%, and 41.5179% has been observed as compared to strength at 7 days of FA100, G20D0, G10D10, G15D5, G5D15, and G0D20 mixes, respectively. Furthermore, at 56 days of curing, strength gain of 66.2%, 36.23%, 58.18%, 29.61%, and 19.51% was observed for the mixes G20D0, G15D5, G10D10, G5D15, and G0D20, respectively, when compared to the control mix FA100 (28.7 MPa). Also, it has been noticed that the compressive strength of G20D0 and G10D10 was comparable with each other at all curing ages. Increased calcium and silicate content in GGBS and dolomite leads to increased strength by increasing the hydration rate, and these two binders also have significantly distinct particle shapes and morphology than that of FA, i.e., spherical and smooth for FA and asymmetrical and rough for GGBS and dolomite, leading to superior mechanical characteristics in FA-based mixtures. The asymmetrical and complicated shape of the GGBS and dolomite particles results in mechanical anchoring within the concrete matrix, thus enhancing the hardened mixture compressive strength. Previous studies have also reported the positive effect of adding dolomite on compressive strength through two mechanisms: mechanical anchoring due to the differences in the particle shapes and morphologies of dolomite particles within the matrix, with FA, and enhanced hydration reaction (Cohen et al. 2019). Similarly, the angular shape of GGBS particles and the presence of calcium accelerate the reaction, leading to improved mechanical properties (Ramineni et al. 2018). Since the finer particles fill the voids and make the matrix dense, increasing the binder fineness results in a substantial enhancement in GPC strength. Figure 3 represents the results of the compressive strength tests conducted on the various mixes made with GGBS and dolomite as replacement of FA at 7, 28, and 56 days of curing period.

Fig. 3
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Compressive strength values of different mixes at 7, 28, and 56 curing days

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4.3 Split tensile strength

The split tensile strength of FA-based GPC was tested on the specimens at the different ages of 7, 28, and 56 days to study the effect of GGBS and dolomite inclusion on it. The results of the split tensile strength test of the concrete at all ages are presented in Fig. 4, and it shows a similar trend to the results of compressive strength tests. The addition of GGBS and dolomite as partial replacements for FA improved the concrete mixes split tensile strength. The mixes G20D0 and G10D10 show the maximum split tensile strength values. As a result, the GPC mixes should be arranged in the same order as the compressive strength test results: G20D0 > G10D10 > G15D5 > G5D15 > G0D20 > FA100. At all curing days, the GGBS and dolomite-blended mixes have higher split tensile strength values than the control mix FA100. The mixes G20D0, G15D5, G10D10, G5D15, and G0D20 have a significant increase of nearly 123%, 105.31%, 118.58%, 94.69%, and 38.05%, respectively, when compared to the control mix FA100 (1.13 MPa) after 7 days of curing. Also, it has been observed that the split tensile strength of G20D0 and G10D10 was comparable with each other at all curing ages. However, the split tensile strength of all GPC mixes has risen with curing time due to pozzolanic behavior, pore structure refinement, and the generation of new strength-imparting hydration products. Strength gains of 33.63%, 37.69%, 30.17%, 36.44%, 30.45%, and 21.79% have been observed after 28 days of curing when compared to the strength of FA100, G20D0, G10D10, G15D5, G5D15, and G0D20 mixes at 7 days. Furthermore, strength gains of 125.7%, 90.64%, 118.71%, 74.26%, and 29.24% were spotted for the mixes G20D0, G15D5, G10D10, G5D15, and G0D20, respectively, as compared to the control mix FA100 (1.71 MPa) at 56 days of curing. The split tensile strength of GPC is enhanced by increasing the fineness of the binder material, as the finer particles fill voids and make the concrete matrix dense. Moreover, the increased calcium and silicate content in GGBS and dolomite leads to increased split tensile strength.

Fig. 4
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Split tensile strength values of different mixes at 7, 28, and 56 curing days

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4.4 Initial surface absorption

ISAT is used to calculate the flow of water into a dry, flat concrete surface. The absorption rate was estimated by measuring the uniaxial water penetration on the surface of the concrete specimens, which are often exposed to severe circumstances. The surface absorption resistance is a crucial parameter for predicting the durability of concrete. Figure 5a, b illustrates the absorption rates of the six mixes after 28 and 56 curing days. The G20D0 mix has been found to have the lowest absorption rate at both curing periods followed by the mixes G10D10, G15D5, G5D15, and G0D20, and the highest magnitude of absorption rate has been attained by the control mix FA100. The rate of absorption gradually reduces with the addition of GGBS and dolomite. The percentage of absorption rate reduction for mix G20D0 has been recorded to rise with advancing curing regime from 28 to 56 days, ranging from 45.26 to 50.62%, which is directly equivalent with G10D10 mix ranging from 40 to 38.27% with respect to the control mix (0.95–0.81 ml/m2 s) for 10 min. Similarly, the absorption rate for G15D5, G15D5, and G0D20 reduces by 30.52%, 26.31%, and 12.63% when related to that of control mix FA100 (0.95 ml/m2 s) for 10 min at 28 days of curing. Furthermore, reductions of 35.8%, 27.16%, and 12.34% were observed for G15D5, G15D5, and G0D20 mixes, respectively, at 56 curing days when compared to the control mix FA100 (0.81 ml/m2 s) for 10 min. As the time passes, the absorption rate also declines. For all the mixes, the rate of absorption decreases at 30 min and further decreases at 60 min. The absorption rate reduces by 61.2% and 65% at 30 min and 60 min, respectively, for mix G20D0 and 47.76% and 60% for mix G10D10 at 56 curing days in contrast to the control mix (0.67–0.60 ml/m2 s). Surface absorption is reduced due to the use of GGBS and dolomite because their finer particle size causes pore size refinement and thus makes the concrete matrix denser. Past studies have also indicated that the decrease in surface absorption can be ascribed to the finer characteristics of GGBS particles, which enhance the pore structure of concrete (Bostanci et al. 2016). Also, it has been observed that dolomite is even finer than that of GGBS (Ye et al. 2019), indicating that dolomite also possesses the capability to refine the pore structure, resulting in a denser matrix.

Fig. 5
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a Initial surface absorption values after 28 days of curing. b Initial surface absorption values after 56 days of curing

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4.5 Capillary suction absorption

The sorptivity at early stages reveals the transport mechanism of the movement of water within concrete. It is evident from the findings that mix G20D0 has the lowest water absorption rate among all the mixes, followed by G10D10 mix. The initial rate of absorption (IRA) refers to the water absorption rate of GPC containing different proportions of binders for the first 6 h, while the secondary rate of absorption (SRA) is assessed over a period of 1–8 days. It can be observed that the rate of water absorption for all concrete becomes nearly stable after about 1 day. Figure 6a, b illustrates the combined value (IRA + SRA) of capillary suction absorption after 28 and 56 curing days, respectively. The findings are also consistent with the initial absorption rate, as secondary absorption also decreases with the inclusion of GGBS and dolomite as a partial replacement of FA. The rate of initial absorption is about 57.19%, 37.47%, 52.27%, 34.71%, 19.92% lower for mixes G20D0, G15D5, G10D10, G5D15, G0D20, respectively, from that of control mix FA100 (0.0507 mm/s1/2) at 28 curing days. The secondary absorption rate also decreases by 53.84%, 23.07%, 30.77%, 23.07%, 15.38% for mixes G20D0, G15D5, G10D10, G5D15, G0D20, respectively, from that of control mix FA100 (0.0013 mm/s1/2) at 28 curing days. Similar trend has been observed for 56 curing days, and with the passage of time, the IRA and SRA values decrease for GPC. The decrease of 54.74%, 44.42%, 52.84%, 40.42%, and 18.31% in IRA and 54.54%, 18.18%, 27.27%, 18.18%, and 9.09% in SRA has been reported at 56 days of curing for mixes G20D0, G15D5, G10D10, G5D15, G0D20, respectively, from that of IRA-SRA of control mix FA100 (0.0475–0.0011 mm/s1/2). The strength of concrete is significantly influenced by the water-to-cement ratio, which regulates air voids and thus secondary absorption. However, the initial absorption is governed by capillary forces (Albitar et al. 2017). Sorptivity proves that GGBS absorbs less water due to its crystalline structure (Purushotham et al. 2017). The finer particles of GGBS and dolomite result in the development of a dense microstructure that further reduces the IRA-SRA values.

Fig. 6
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a Capillary suction absorption values after 28 days of curing. b Capillary suction absorption values after 56 days of curing

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4.6 Ultrasonic pulse velocity

Non-destructive testing is generally employed to examine the material integrity of the concrete structures. The UPV is an important non-destructive test which gives the impression about the quality of concrete. Greater the readings of pulse velocities, more is the quality of concrete. Inclusion of GGBS and dolomite increases the pulse velocity readings, and their addition in the concrete proves to be beneficial as the quality of concrete increases. Inclusion of these binders results in denser concrete as its finer particles help in pore refinement. The mix G20D0 followed by G10D10 performed the best among all the mixes at all curing days. Around 36.24%, 19.71%, 31.68%, 19.02%, and 12.09% increment in the pulse velocity is obtained at 7 curing days for the mixes G20D0, G15D5, G10D10, G5D15, and G0D20, respectively, in contrast to the control mix FA100 (2907 m/s) mix, as shown in Fig. 7. Moreover, the UPV improves as the number of curing days increases, indicating that the concrete gets better over time. At 28 curing days, the UPV value increased by 5.48%, 4.34%, 7.29%, 6.84%, 7.5%, and 6.26% for mixes FA100, G20D0, G15D5, G10D10, G5D15, and G0D20, respectively, when compared to the UPV value of each mix at 7 days of curing. Furthermore, rise of 39.743%, 24.64%, 39.16%, 21.64%, and 7.98% was spotted in pulse velocity for the mixes G20D0, G15D5, G10D10, G5D15, and G0D20, respectively, as compared to the control mix FA100 (3268.5 m/s) at 56 curing days. As concrete ages, the capillary pores and cracks are eliminated due to an increase in hydration, resulting in reduced pulse transmission resistance (Sadeghi Nik and Lotfi Omran 2013). The increase in UPV with age is a natural progression caused by the stiffening effect of the geopolymerization reaction. The quality of concrete increases from day to day for the same concrete samples due to geopolymerization, which makes it stronger and more durable over time.

Fig. 7
figure 7

UPV values of mixes at different curing days

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4.7 Electrical resistivity

Electrical resistivity of all the GPC mixes has been measured to examine the effect of incorporation of various cementitious binders (GGBS and dolomite) in FA-based GPC. Overall, the addition of these binders as a partial replacement for FA has increased electrical resistivity at all curing ages. The overall trends as observed for the electrical resistivity of all the concrete mixes after 7, 28, and 56 days are presented in Fig. 8. The electrical resistivity in G20D0, G15D5, G10D10, G5D15, and G0D20 increased by 60.72%, 21.43%, 46.43%, 25%, and 17.86%, respectively, in comparison with FA100 (2.8 kΩ cm) at 7 days of curing. Similarly, at 28 and 56 curing days, the electrical resistivity further increases. Electrical resistivity values for mixes G20D0, G15D5, G10D10, G5D15, and G0D20 were found to increase by 67.65%, 35.29%, 47.06%, 20.58%, and 11.76%, respectively, after 28 days of curing and by 65%, 25%, 50%, 22.5%, and 7.5%, respectively, after 56 curing days, in comparison with the resistivity value of the control mix FA100 (3.4 kΩ cm at 28 days–4 kΩ cm at 56 days). Therefore, it can be inferred that the percentage of GGBS and dolomite in the concrete greatly influences the electrical resistivity values. Despite the higher electrical resistivity observed in mix G20D0, the results are quite comparable to that of mix G10D10 across all ages of curing. The fine GGBS and dolomite particles result in the densification of the concrete matrix, and hence fewer pores are available for saturation and movement of ions. Also, GGBS and dolomite have a larger specific surface area than that of FA. This assertion can be substantiated by empirical evidences from the prior researches, where the specific surface area values of FA, GGBS, and dolomite have been reported as 385 m2/kg (Liu et al. 2022), 400 m2/kg (Yang et al. 2019), and 840 m2/kg (Pehlivan et al. 2009), respectively. As a result, the geopolymerization products for these binders are much denser and more compact than geopolymers based on FA. However, as per AASHTO—T 358 (2015), the overall performance of all the mixes was not up to the mark as the resistivity values for all the mixes at all ages were less than 12 kΩ cm, indicating high chloride ion penetration.

Fig. 8
figure 8

Electrical resistivity values of mixes at different curing days

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4.8 Comparison of results with existing related literature

Table 4 summarizes the findings of several studies conducted by various authors, using different binder types (Bellum et al. 2022; Prabha et al. 2022; Verma and Dev 2022; Kumar and Reddy 2023). Previous researches indicate that using either GGBS or dolomite in FA-based GPC results in similar trends for mechanical and durability behaviors. However, no study has yet investigated the combined effect of both GGBS and dolomite in FA-based GPC. Additionally, there are very few investigations available that have examined the durability behavior, in terms of ISAT and CSAT. Furthermore, only a limited number of studies have examined non-destructive testing techniques, like UPV and electrical resistivity, for FA-based GPC containing GGBS and dolomite. As a result, the present study offers valuable insights into the performance of FA-based GPC containing both GGBS and dolomite, shedding light on its mechanical, durability, and non-destructive test properties.

Table 4 Comparison of the present study results with the existing related literature
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4.9 ANOVA test

Significant values (i.e., P value) for the ANOVA test are presented in Table 5. Since the significant (P) value for both compressive strength and split tensile strength is smaller than 0.05, we have enough evidence to reject H0 and accept H1 (Vairagade et al. 2021). Therefore, it can be concluded that there is some significant difference between the six sets of mixes for a given number of days. The mix of various binders and its variants has a significant impact.

Table 5 Significant values for ANOVA test
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4.9.1 Reliability of strength

The significant variation in the mechanical strength, at 7, 28, and 56 curing days, due to the inclusion of different binders, is future studied and presented in Table 6. All the R2 values are above 0.80, which provides good reliability of the mixes. Also, the value of standard error is very low, indicating the reliability of strength.

Table 6 Regression statistics for reliability
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5 Cost analysis

The total cost for all six mixes is estimated and reported in Table 7 to determine the optimum mix obtained from the investigation. To estimate the cost, market prices for commercially available materials have been used. Cost is calculated for the quantity of material in kg/m3. The G20D0 mix has been found to have the highest cost of Rs. 5928.95, followed by mix G15D5 (Rs. 5676.11). The control mix has been observed to have the lowest cost of all other mixes. Mixtures containing the percentage of dolomite, on the other hand, reduce costs significantly. The reduction of 4.2645%, 8.53%, 12.79%, and 17.06% has been observed for mixes G15D5, G10D10, G5D15, and G0D20, respectively, when compared to that of mix with maximum cost (G20D0). Hence, mix G10D10 can be a better substitute for mix G20D0 and mix G5D15 for mix G15D5 as their mechanical and durability properties are quite comparable.

Table 7 Cost of materials and cost analysis of all the mixes
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6 Conclusions

This research emphasizes the potential of replacing FA with GGBS and dolomite to produce more eco-friendly and sustainable concrete. The study also validates the use of industrial waste as construction materials, addressing issues such as limited disposal sites and degrading environmental quality.

The incorporation of GGBS and dolomite has shown promising results in terms of improved mechanical strength, durability, sustainability, and environmental friendliness of concrete. However, the inclusion of GGBS and dolomite in FA-based GPC as binder replacement significantly reduced the slump value. The asymmetrical shape and larger specific surface area of GGBS and dolomite particles compared to FA led to reduced workability and increased water demand. Dolomite, in particular, resulted in a greater decrease in workability due to its higher water demand.

Nevertheless, the addition of GGBS and dolomite significantly enhanced the compressive strength and split tensile strength of the GPC mixtures, at all curing ages. Incorporating 20% GGBS by weight of FA resulted in the highest strength gain of 66.2%, while a mix with 10% GGBS and 10% dolomite achieved a strength gain of 58.18% compared to the reference mix with 100% FA at 56 curing days. The higher calcium and silicate content of GGBS and dolomite accelerated the hydration rate, contributing to increased strength. The irregular shape of these particles also promoted mechanical anchoring within the concrete matrix, further enhancing strength.

Moreover, the inclusion of GGBS and dolomite reduced permeability and absorption rate, resulting in a denser microstructure with refined pore size and reduced surface absorption. The mixes containing 20% GGBS (i.e., G20D0) and 10% GGBS with 10% dolomite (i.e., G10D10) performed best in terms of permeability and absorption characteristics. The maximum reduction in IRA-SRA values of the order of 54.73–54.54% for mix G20D0 and 52.84–27.27% for G10D10 mix has been observed with respect to the control mix (0.0475–0.0011 mm/s1/2).

Additionally, the mixes with GGBS and dolomite exhibited higher UPV values, indicating improved concrete densification and reduced pulse transmission resistance over time. As concrete ages, capillary pores and cracks are eliminated due to an increase in hydration, resulting in reduced pulse transmission resistance. The increase in UPV with age can be attributed to the stiffening effect due to the geopolymerization reaction. The overall electrical resistivity of the GPC mixes increased with the partial replacement of FA with GGBS and dolomite, indicating reduced saturation and movement of ions due to the denser concrete matrix.

The results of the one-way ANOVA, conducted to assess the compressive and split tensile strength at various curing days, demonstrated significant variation among the mixes. Moreover, the R2 values being consistently above 0.80 indicated a high level of reliability for the mixes.

In terms of cost, the research indicates that the mix with 10% GGBS and 10% dolomite provides a more cost-effective solution compared to the mix with 20% GGBS, as it achieved comparable mechanical and durability properties while reducing costs by 8.53%. These findings demonstrate the potential and benefits of utilizing GGBS and dolomite as sustainable alternatives in GPC for various civil engineering applications.