Introduction

Cement concrete stands as the predominant construction material worldwide, witnessing an annual production of around six billion tons due to its robustness, longevity, adaptability, and cost efficiency. In per-person usage, concrete follows closely behind water, ranking as the second most consumed material globally. On a global scale, each individual utilizes an estimated three tons of concrete annually, making it the second most utilized material after water. India alone consumes approximately 4500 lakh cubic meters of concrete annually, equating to roughly one ton per Indian [1,2,3,4,5,6]. Concrete is a mixture of cement and aggregates, with or without admixtures, that undergoes hydration. The production of one ton of ordinary Portland cement (OPC) involves using roughly 2.8 tons of raw materials, including fuel and supplementary components. During the lime de-carbonation process in cement production, about one ton of carbon dioxide gas (CO2) is generated per ton of cement, contributing to global warming and other environmental concerns [7,8,9,10,11,12]. Cement industries are the second biggest greenhouse gas creator, around 5–8% of global carbon emissions [11, 13,Relationship between physical properties

Relationship between compressive strength and split tensile strength

From the overview of the results of compression and split tensile strength tests, it is observed that a linear relation exists between them. The actual values obtained from the mathematical calculation are compared with the relationship in various code books, as represented below [57,58,59]

$$f_{{\text{t}}} = \, 0.59 \, f_{{\text{c}}}^{0.5}$$
(1)
$$f_{{\text{t}}} = \, 0.56 \, f_{{\text{c}}}^{0.5}$$
(2)
$$f_{{\text{t}}} = \, 0.3 \, f_{{\text{c}}}^{0.66}$$
(3)

where ft = Split tensile strength (MPa), fc = Compression strength (MPa).

The split tensile values obtained by adopting these relationships were compared with actual values in Fig. 10. However, the values obtained from these relationships do not match actual values, and there is about 40% variation in values. However, the curve follows the trend of the relationship suggested in the codes. In contrast, the actual results were greater than those obtained from relationships in similar research carried out by previous researchers [60, 61].

Fig. 10
figure 10

Relationship between compression strength and split tensile strength

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Relationship between compressive strength and flexural strength

The overview of compression and flexural strength test results shows that a relationship exists between them. The actual values obtained from the mathematical calculation are compared with the relationship in various code books as represented below [44, 58, 62]

$$f_{{{\text{fl}}}} = \, 0.7 \, \surd f_{{\text{c}}}$$
(4)
$$f_{{{\text{fl}}}} = 0.517 \, \surd f_{{\text{c}}}$$
(5)
$$f_{{{\text{fl}}}} = 0.62 \, \surd f_{{\text{c}}}$$
(6)

where ffl = flexural strength (MPa), fc = Compression strength (MPa).

The flexural strength values obtained by adopting these relationships are compared with actual values in Fig. 11. However, the values obtained from these relationships follow the trend mentioned in the codes. They are in line with actual values except for the value of the conventional mix.

Fig. 11
figure 11

Relationship between compression strength and flexural strength

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Durability properties

Sulfate attack resistance

The durability of any composite depends upon the porosity of the material. The more porosity, the more chemical ingress will occur. In a study, all the mixed samples experienced a weight gain after exposure. The primary cause of weight gain is the chemical reaction between sulfate ions and hydrated calcium aluminate, which forms ettringite. This ettringite increases the volume of the concrete by filling void spaces, causing deterioration [63,64,65,66]. The concrete sample before and after exposure to sulfate attack is shown in Fig. 12, and no such visual changes on the samples can be noticed. From Fig. 13, it can be observed that the increase in weight was minimal at 60% replacement, which means that porosity was minimal even after immersion in a sulfate environment for 60 days. This can also be reinforced by Fig. 3, which shows that the concrete density is at its maximum at 60% GBFS replacement. Hence, it can be confirmed that the decreased porosity improves density, resulting in increased strength and durability. A previous study states that density has a crucial role in improving the durability properties of concrete [67]. When the cubes exposed to sulfate attack test were subjected to a compression test, the percentage decrease in strength concerning 28 days compressive strength is depicted in Fig. 14. It is evident that except for 0% replacement (conventional concrete), the percentage decrease in strength was minimum at 60% GBFS replacement. The data presented highlights the critical relationship between porosity, density, and durability in concrete. By strategically incorporating GBFS as a replacement material, concrete structures can exhibit improved resistance to sulfate attack and enhanced overall durability, contributing to their long-term performance and service life in challenging environments.

Fig. 12
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Concrete samples a before sulfate attack b after sulfate attack

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Fig. 13
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Percentage increase in weight of the specimens when exposed to sulfate solution

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Fig. 14
figure 14

Percentage change in the strength of the specimens after exposure to sulfate solution

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Acid attack resistance

When acid seeps into the concrete, the cement paste binder breaks down, forming the gypsum. The gypsum reacts chemically with the hydrated calcium aluminate and produces ettringite, which deteriorates the concrete through weight and strength loss [68,69,70,71]. The state of the concrete samples after being exposed to the acidic solution for 60 days when compared to those before testing can be seen in Fig. 15. Figure 16 depicts that the decrease in weight was minimal at 60% replacement, meaning that porosity was minimal even after immersion in a sulfate environment for 60 days. Figure 17 shows the percentage change in compressive strength of concrete specimens subjected to acidic exposure for 60 days, and it was observed that the change was minimal at 60% GBFS replacement. Thus, 60% GBFS replacement can be considered the optimum replacement level for practical usage and future work, even in the durability test. From this research, it can be observed that triple-blended concrete depicted the best results at 60% slag replacement. The consistency of these findings with previous research, such as the work by Gamal Elgendy et al. [72] and Jariyathitipong P et al. [71], further validates the effectiveness of 60% slag replacement in improving concrete durability. While Elgendy’s study focused on water permeability, a key factor contributing to concrete deterioration, the similar trend observed in acid attack resistance reinforces the significance of optimizing GBFS replacement levels to enhance the overall durability properties of concrete.

Fig. 15
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Concrete samples a before acid attack b after acid attack

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Fig. 16
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Percentage decrease in weight of the specimens when exposed to acidic solution

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Fig. 17
figure 17

Percentage change in strength of the specimens after exposure to acidic solution

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From the above experimentations, it can be noticed that the density of the concrete was highest at 60% replacement of M-sand by GBFS, which is attributed to the dense packing of fine aggregates of Zone II and Zone I and also the increase in the quantum of GBFS, which has greater specific gravity than M-sand. As a concrete mix of M25 grade, the target strength was around 33 MPa; however, at 0% replacement, the compressive strength is far greater than the target strength. Hence, the replacement of M-sand by GBFS is acceptable up to a level that does not decrease beyond the target strength. At 60% replacement of M-sand by GBFS, the strength gained by concrete was around 38 MPa, whereas at 80% replacement, it was less than 30 MPa. From durability studies, it is observed that the increased weight was least at 60% replacement level and the change in strength marginally higher than that of concrete specimens with 0% replacement. The acid attack test results showed that the percentage decrease in weight after the acid attack and percentage decrease in strength was the lowest for the concrete specimens containing 60% of GGBS, and 40% of M-sand was fine aggregate. Hence, the triple-blend concrete mix containing 40% cement, 40% GGBS, and 20% FA as the binder material, 40% M-sand and 60% of GBFS as fine aggregate with crushed stone 20 mm downsize granite coarse aggregate can be considered as an optimum mix.

Conclusions

The following conclusions are drawn based on the various tests conducted on triple-blend concrete with varying proportions of fine aggregate.

  1. 1.

    The concrete density varies from 2.44 to 2.54 g/cc with a maximum density of 2.58 g/cc at 60% replacement of M-sand with GBFS, which might be because of the effective packing of fine aggregates.

  2. 2.

    Compressive strength of about 51 MPa was achieved at 28 days at 0% replacement of GBFS, much higher than the target strength of M25-grade concrete. The increase in replacement levels of GBFS causes a decrease in compressive strength; at 60% GBFS replacement over M-sand, the desirable compressive strength of M25-grade concrete will be attained. The split tensile strength and flexural strength of triple-blended concrete follow the same trend as that of compressive strength.

  3. 3.

    The rate of change of strength gain was highest during the initial days, and it diminishes with time. After 56 days, the rate of mechanical strength gain was almost constant. The highest compressive strength gain of 70% was noticed between 3 and 7 days at 0% replacement, and it was around 5% for 100% replacement.

  4. 4.

    The split tensile strength achieved was lesser than the values obtained from the various other relationships prescribed in the standard codes and specifications. However, the flexural strength was marginally higher than the values obtained from various relationships mentioned in standard codes and specifications.

  5. 5.

    Concrete specimens with 60% of fine aggregates as GBFS subjected to sulfate attack witnessed the lowest percentage decrease in strength of about 1.4% after 0% replacement, with a notable factor that the percentage increase in specimen weight was as low as 0.12.

  6. 6.

    Concrete specimens to acid attack test depict that the specimen containing 60% GBFS and 40% M-sand as fine aggregates exhibit a minor percentage decrease in weight of 1.9 along with a minimal percentage strength loss of 3.5%

From this experimental investigation, the triple-blend concrete obtained with 60% replacement of natural fine aggregate by GBFS can be used for all kinds of construction practices. The use of FA, GGBS, and GBFS reduces the usage of cement and manufactured sand, resulting in waste management and reduced CO2 emissions. Thus, it aids to subside the disposal and pollution-related issues.

Scope for future works

This study shows that the triple-blended concrete using FA and GGBS as a partial replacement for OPC and 60% replacement of M-sand with GBFS would result in an effective concrete of M25 grade. In continuation to the same, the following research can be continued.

  1. 1.

    Further investigation on durability by subjecting the specimens to carbonation, raid chloride penetration, and sorptivity test.

  2. 2.

    The triple-blend composition can be experimented with special concretes such as fiber-reinforced concrete, self-compacting concrete, and lightweight concrete.

  3. 3.

    Further studies can be carried out on this concrete’s thermal resistivity and fire resistance behavior.

  4. 4.

    Experimentations can be carried forward using NDTs, which can be compared with the existing test results.

  5. 5.

    Microstructural studies can be carried out on the specimens to determine the difference at the microstructure level.