Introduction

With rapid urbanization and infrastructure expansion, concrete has become an essential material in modern engineering1,2,3. Traditional concrete relies heavily on natural aggregates such as river sand and gravel, leading to increased environmental pressure and production costs4,5,6. In recent years, growing awareness of resource shortages and environmental sustainability has driven interest in developing eco-friendly alternatives for concrete production.

Iron tailings sand, a waste material generated from metallurgical and mining operations, has gained attention for its potential reuse in construction7,8. Li et al.9 showed that pyrite tailings (PRT), rich in FeS₂, can effectively activate peracetic acid (PAA), removing 93.67% of sulfamethoxazole (SMX) in 50 min at pH 5.8. Lei et al.10 found that copper tailings (CTP), due to their rough texture and high specific surface area, improve asphalt adsorption and filler interaction. Their use in asphalt mastic enhanced high-temperature resistance, with only minor reductions in low-temperature and moisture performance. Heavy metal leaching tests confirmed their safety. Chen et al.11 developed a method to recycle iron from vanadium titanomagnetite tailings (VTMT), converting it into Fe₂O₃ and incorporating it into asymmetric supercapacitors with promising capacitive performance.

These studies suggest that tailings possess favorable chemical composition, particle morphology, and surface properties, making them suitable as alternative materials in construction. Iron tailings sand, in particular, shows potential as a substitute for fine aggregates in concrete. Its use can reduce environmental pollution and lower material costs, especially under growing resource constraints and environmental regulations. Although previous studies have confirmed the potential of iron tailings sand as a sustainable fine aggregate, most of the existing research has focused on static properties such as compressive strength or workability. However, little attention has been given to the cyclic compressive behavior of ITS concrete, which is crucial for evaluating performance in seismic and dynamic loading conditions. The lack of systematic experimental evidence on how different ITS contents influence deformation capacity, energy dissipation, and structural resilience under repeated loads represents a key research gap that this study aims to address. Dong et al.12 evaluated mixtures containing over 60% iron tailings sand (ITS) and reported compressive strengths up to 7 MPa, meeting pavement requirements. They emphasized particle size as a key factor. Shi et al.13 found that replacing 20% of cement with iron tailings powder (ITP) and 50% of quartz sand with ITS in ultra-high-performance concrete (UHPC) improved strength (145.6 MPa) and flexural toughness (110.99 N·m), while also refining pore structure and reducing harmful porosity. Environmental testing confirmed minimal heavy metal leaching. Okewale et al.14 noted that iron tailings are angular, isotropic, and contain trace heavy metals such as chromium and copper. Wang et al.15 reviewed the engineering use of metal tailings and highlighted their potential as secondary resources if properly managed.

Despite growing research on ITS as a sand replacement, few studies have examined its behavior under cyclic loading. This is a critical gap, as cyclic compression performance is essential for concrete durability in seismic and heavy-load structures. This study investigates the influence of different ITS contents on the mechanical and cyclic behavior of concrete. Through experimental testing, we analyze its workability, compressive strength, and energy dissipation capacity, aiming to provide practical and theoretical guidance for incorporating iron tailings sand in structural concrete applications. This study provides a comprehensive experimental investigation into the effects of iron tailings sand on concrete behavior under cyclic compression, which has been largely overlooked in previous research. By analyzing deformation characteristics, energy dissipation, and mechanical response at varying ITS replacement levels, the work identifies 30%–40% ITS as an optimal range for balancing strength, ductility, and durability. The findings offer practical guidance for sustainable utilization of metallurgical waste in structural concrete and support its application in seismic-resistant and cyclic load-bearing infrastructure.

Experimental materials and test design

Raw materials

The raw materials used in this study include Conch brand P·O 42.5R cement and Class II fly ash produced by Shenglong Technology Industrial Co., Ltd., as the cementitious materials. Coarse aggregate consists of crushed stones with particle sizes ranging from 5 to 15 mm, while fine aggregates include natural sand with a fineness modulus of 2.43 and tailings sand with a fineness modulus of 1.38, sourced from areas around Xi’an and Zijin Mining Group, respectively. The physical properties of the aggregates are summarized in Table 1, indicating that natural sand has an apparent density of 2,810 kg/m3 and a bulk density of 1,970 kg/m3, with a water absorption rate of 4.2%, a crushing index of 12.40%, a mud content of 3.00%, and a moisture content of 2.60%. In comparison, tailings sand exhibits an apparent density of 2,770 kg/m3, a bulk density of 1,810 kg/m3, a water absorption rate of 6.6%, a crushing index of 21.10%, a mud content of 3.10%, and a moisture content of 2.60%. The chemical composition of the aggregates, as shown in Table 2, reveals that natural sand primarily comprises 71.0% SiO₂, 9.2% Al₂O₃, and smaller proportions of other oxides, while tailings sand contains 67.8% SiO₂, 14.5% Fe₂O₃, and notable amounts of MgO and CaO. Additionally, the particle size distribution of tailings sand is illustrated in Fig. 1. The water reducer used is a high-performance HPWR superplasticizer, and the water is sourced from the local tap supply.

Table 1 Physical Properties of Aggregates.
Full size table
Table 2 Chemical Composition of Aggregates.
Full size table
Fig. 1
figure 1

Particle size distribution curve of iron tailings sand.

Full size image

Mix proportion design and experimental methods

To investigate the effect of iron tailings sand on the workability and cyclic compressive behavior of concrete, the absolute volume method was employed for multiple mix trials. The final mix proportions for iron tailings sand concrete were determined, as shown in Table 3. The experimental design involved varying the iron tailings sand content (0%, 10%, 20%, 30%, 40%, 50%, 60%) while maintaining a constant total sand content to ensure comparability in both workability and mechanical performance.

Table 3 Mix proportion design.
Full size table

During the experiment, crushed stone with a particle size range of 5–20 mm was selected as the coarse aggregate, while the fine aggregate consisted of a combination of natural river sand and iron tailings sand in varying proportions, ensuring a total fine aggregate content of 620 kg/m3. To maintain consistency, other materials, including cement, water, and a high-performance water-reducing agent, remained unchanged. The water-to-binder ratio was set at 0.5, and the polycarboxylate superplasticizer dosage was fixed at 4.70 kg/m3.

Concrete mixing followed the JGJ 55–2011 "Code for Design of Ordinary Concrete Mix Proportions"16,17,18 and was conducted using a mechanical mixer. The mixing process included the following steps:

  • Dry Mixing: Coarse aggregate, fine aggregate, and cement were mixed evenly.

  • Wet Mixing: Water and the superplasticizer were gradually added while mixing continued until a uniform concrete mixture was obtained.

Each mix was subjected to workability tests, including slump and bleeding rate measurements, to evaluate its fluidity. Additionally, 150 × 150 × 150 mm standard cube specimens were cast for compressive strength tests. To further examine the cyclic compressive performance of iron tailings sand concrete, 100 × 200 mm standard cylindrical specimens were prepared and tested under uniaxial cyclic compression using a servo-hydraulic testing machine. The loading frequency was set to 0.2 Hz, and the loading amplitude started at 0.1 times the peak stress, gradually increasing until failure. Figure 2 illustrates the specimen preparation process.

Fig. 2
figure 2

Specimen preparation.

Full size image

Experimental results and analysis

Fundamental properties of iron tailings sand concrete

Slump test

Concrete samples were prepared on-site and tested 30 min after mixing. The slump test was conducted using a clean and oil-free slump funnel. The funnel was filled to the top with concrete, and a metal rod was used to gently tamp the surface to remove air voids and level the sample19,20. Once the funnel was filled, the bottom opening was released, allowing the concrete to flow freely onto a measuring scale. The final height of the slumped concrete was recorded as the slump value (Fig. 3). Each sample’s slump was measured, and the average value was calculated to assess the workability of the concrete mix. According to the Chinese national standard JGJ 63–2006 "Specification for Mix Proportion Design of Ordinary Concrete", a slump value above 100 mm is generally required for pumpable concrete in structural construction. In this study, when the ITS content exceeded 40%, the slump fell below this threshold, indicating limited workability for standard pumping applications. Therefore, ITS replacement levels beyond 40% may not meet practical construction requirements without additional admixture adjustment.

Fig. 3
figure 3

Slump test.

Full size image

Regression analysis of Fig. 3 reveals a clear negative linear correlation between iron tailings sand (ITS) content and concrete slump, described by the equation y = –1.25x + 159.62, where y is the slump (mm) and x is the ITS content (%). The regression model showed a high degree of fit, with a coefficient of determination R2 = 0.984. This indicates that 98.4% of the variation in slump can be explained by changes in ITS content, demonstrating the strong predictive relationship between ITS replacement level and concrete workability under the given mix conditions. As the ITS content increases from 0 to 60%, the slump steadily declines from approximately 158 mm to 80 mm. When ITS content exceeds 40%, the slump drops below 100 mm, indicating insufficient workability for conventional construction. This reduction is primarily caused by the angular shape and rough texture of ITS particles, which increase interparticle friction and hinder flow. The large specific surface area of ITS also adsorbs more free water, diminishing the lubricating effect of cement paste and further impairing workability21,22. The regression suggests that each 1% increase in ITS leads to a slump reduction of about 1.25 mm. This significant decrease highlights the need to carefully control ITS dosage in mix design to maintain practical workability while improving material sustainability.

Water Absorption Test.

Figure 4 presents the water absorption measurements of different concrete specimens after 7, 14, and 28 days of curing. The results show a gradual decrease in water absorption over time, with an average reduction of 10%-15% between 7 and 28 days. For 0% ITS content, the water absorption decreases from 3.199% at 7 days to 2.934% at 28 days, whereas for 60% ITS content, it decreases from 4.738% to 4.304% over the same period.

Fig. 4
figure 4

Water Absorption test results.

Full size image

This reduction is primarily due to the hydration reaction of cement, which forms C-S–H gel, progressively filling internal pores and increasing the densification of the concrete structure. However, the ITS content significantly affects water absorption, with higher ITS content leading to increased absorption rates. At 28 days, increasing the ITS content from 0 to 60% results in a 46.7% increase in water absorption, from 2.934% to 4.304%. ITS particles are finer than natural river sand and possess a higher specific surface area, making them more prone to water absorption. Their rough surface texture and angular shape also increase porosity and interconnectivity between voids, altering the microstructure of the concrete and leading to higher water absorption rates23. The incorporation of ITS significantly modifies the pore distribution and the interface transition zone between cement paste and aggregate, making its effect on concrete notably different from conventional aggregates. Proper control of ITS content is essential for optimizing concrete performance and ensuring its long-term durability.

Pressure bleeding rate test

In this study, the term “pressure bleeding rate” refers to the volume percentage of bleed water that separates from the concrete mixture under applied static pressure. It is a key indicator of the mixture’s pumpability and stability during transportation. This definition is consistent with the terminology used in the Chinese standard JGJ/T 70–2009 “Technical Specification for Pumping Construction of Concrete”, which evaluates the bleeding behavior of concrete under pressurized conditions to assess segregation risk during pumping. In practical engineering applications, the pressure bleeding rate is an important indicator of the pumpability of concrete. Figure 5 shows that the pressure bleeding rate increases gradually with the increase of iron tailings sand content. When the iron tailings sand content is less than 40%, the pressure bleeding rate remains below 40%, ensuring good pumpability and stable flowability of the concrete mixture. However, when the content exceeds 40%, when the pressure bleeding rate exceeds 40%, it may cause aggregate segregation and pipeline blockage during pumping. At 0% iron tailings sand content, the pressure bleeding rate is 7.55%, whereas at 60% content, it rises to 47.58%, representing an increase of over 500%. The primary mechanism behind this phenomenon lies in the particle morphology and physical properties of iron tailings sand. Its rough surface and angular shape increase inter-particle friction within the concrete mixture, reducing the lubricating effect of the cement paste and impairing flowability24. At higher contents, the finer particles have a larger specific surface area, enhancing their ability to absorb cement paste, thereby reducing the paste’s ability to coat aggregates. This leads to an increase in porosity and bleeding rate, ultimately causing a significant rise in pressure bleeding. The Chinese standard JGJ/T 70–2009 "Technical Specification for Pumping Construction of Concrete" recommends that the pressure bleeding rate should not exceed 40% for concrete used in pumped applications. In this study, mixtures with ITS content above 40% showed bleeding rates exceeding this limit, which may lead to segregation and blockage during pumping. Therefore, ITS levels over 40% are not recommended for pumpable concrete unless appropriate modifications are made.

Fig. 5
figure 5

Pressure bleeding rate test results.

Full size image

Analysis of basic mechanical properties

Basic mechanical properties are key indicators for evaluating the engineering performance of concrete. This study conducted compressive strength tests on concrete specimens with different iron tailings sand contents to analyze their fundamental mechanical properties. The results show that iron tailings sand content has a significant impact on the compressive strength of concrete, exhibiting a non-monotonic trend. As the iron tailings sand content increases, the compressive strength of concrete reaches its peak at 40% content, followed by a gradual decline. The results of the compressive strength test are shown in Table 4.

Table 4 Compressive Strength Test Results.
Full size table

Basic mechanical properties are crucial for evaluating the structural performance of concrete. In this study, uniaxial compressive strength tests were conducted on concrete specimens with varying iron tailings sand (ITS) contents. Each group consisted of three specimens, and the average strength along with the standard deviation was calculated to ensure data reliability. The results, presented in Table 4, show that the compressive strength of concrete follows a non-monotonic trend with increasing ITS content. When the content was below 40%, the strength gradually increased, peaking at 40% ITS with an average value of 45.63 MPa and a standard deviation of 0.21 MPa. This value is approximately 17.6% higher than that of the 0% ITS group. This enhancement can be attributed to the filler effect of the fine tailings particles, which reduce pore size and improve matrix compactness. Additionally, the rough surface and angularity of ITS promote a denser interfacial transition zone, strengthening the bond between paste and aggregate. When the ITS content exceeded 40%, the compressive strength declined significantly. At 60% content, the strength dropped to 37.43 MPa with a higher variation, indicating unstable mechanical behavior. The decline is likely due to increased porosity and higher water absorption associated with excessive fine particles, which negatively affect cement paste cohesion and aggregate bonding24,25,26. One-way ANOVA confirmed a statistically significant difference in compressive strength among the groups with varying iron tailings sand content (F = 170.55, p < 0.0001), indicating that the observed strength changes are not due to random variability but directly related to ITS replacement levels.

Experimental findings indicate significant differences in the failure mode of concrete incorporating iron tailings sand compared to ordinary concrete. Ordinary concrete specimens exhibit typical brittle failure, with straight and penetrating fracture surfaces, fewer cracks, and rapid crack propagation, suggesting that the internal micro-pore structure is less adaptable to external stress distribution. However, as the iron tailings sand content increases, the failure mode of the concrete gradually shifts from brittle failure to plastic failure, as shown in Fig. 6.

Fig. 6
figure 6

Typical failure modes.

Full size image

From Fig. 6, it can be observed that The failure mode of concrete changes significantly with varying iron tailings sand content. Ordinary concrete (0%) exhibits typical brittle fracture, characterized by clean, straight cracks and abrupt failure. As the iron tailings sand content increases to 30%–40%, the fracture surfaces become more irregular, and the number of cracks increases, indicating enhanced ductility and better internal stress redistribution. Specimens with 40% content show multi-directional crack patterns and noticeable plastic deformation prior to failure, which suggests improved toughness. However, beyond 50%, excessive fine particles lead to increased porosity and weakened interfacial bonding, resulting in more severe fragmentation and reduced integrity27,28. These observations confirm that a 30%–40% replacement level provides a favorable balance between strength and ductility for structural applications requiring energy dissipation and crack resistance.

Cyclic compressive performance of iron tailings sand concrete

Cyclic compressive stress–strain curve

Figure 7 presents the cyclic compressive stress–strain curves of concrete with different iron tailings sand contents. As the iron tailings sand content increases, the stress–strain curves exhibit different characteristics. In the initial stage, the curve represents the elastic phase, where stress increases linearly with strain. As strain increases, the curve gradually bends and enters the plastic phase, where the material exhibits greater ductility and energy absorption capacity.

Fig. 7
figure 7

Cyclic compressive stress–strain curve.

Full size image

As shown in Fig. 7, the stress–strain curve of concrete with 0% iron tailings sand initially exhibits a good linear relationship, indicating that stress increases linearly with strain. Subsequently, the curve transitions into a nonlinear phase, signifying the onset of plastic deformation. As microcracks accumulate and internal damage progresses, the peak stress slightly declines during subsequent cycles. Overall, the concrete maintains high stiffness and limited ductility before failure. For concrete with 10% iron tailings sand, the stress–strain curve shows a higher initial stress response than the 0% sample and a more pronounced plastic deformation phase. The addition of iron tailings sand improves the microstructure, enhances load-bearing capacity, and provides greater ductility before failure. Proper incorporation of iron tailings sand enhances mechanical performance, particularly early-stage toughness. At 20% iron tailings sand content, the curve exhibits a steeper slope, indicating a rapid increase in deformation upon entering the plastic stage. As the iron tailings sand content increases, the concrete’s strength and deformation capacity significantly improve, maintaining good ductility near peak stress. For 30% iron tailings sand content, the stress–strain curve demonstrates a notable enhancement in yield strength, particularly with increased strain. The concrete displays superior mechanical properties and high strength during loading. With continued loading, the concrete exhibits effective energy absorption, and the yield phase is relatively smooth, this reflects strong deformation resistance, which is critical for structures requiring high seismic resilience. At 40% iron tailings sand content, the initial stress response is high, and the hysteresis loop area is larger, indicating enhanced energy absorption. The concrete shows excellent plastic deformation ability at peak stress and maintains remarkable toughness before failure. This content level provides a good balance between strength, toughness, and durability, making it ideal for high-load and harsh environmental applications. Concrete with 50% iron tailings sand exhibits a higher initial stress surge, but as loading continues, the curve gradually flattens. At 60% iron tailings sand content, the hysteresis loops of the stress–strain curve become more compact, indicating enhanced energy dissipation and plastic deformation capacity. As the iron tailings sand content increases, the stress–strain curve progressively smooths and becomes more compact, demonstrating that iron tailings sand enhances the microstructure and improves crack resistance. Particularly at higher content levels, the concrete demonstrates enhanced plastic deformation capability and higher energy dissipation efficiency.

Cyclic compressive deformation-time curve

The deformation-time curves of specimens under cyclic compressive loading are shown in Fig. 8. All specimens exhibit nonlinear characteristics, with small initial deformations that gradually increase with repeated loading cycles. Throughout the cyclic loading process, iron tailings sand concrete shows smaller deformations and clear ductile failure characteristics.

Fig. 8
figure 8

Cyclic compressive deformation-time curve.

Full size image

Figure 8 illustrates the deformation-time curves of concrete with varying iron tailings sand (ITS) content under cyclic compressive loading. For ordinary concrete without ITS (0% content), deformation increases gradually with the number of loading cycles, showing low amplitude and smooth fluctuations. This reflects typical elastic behavior. As cycling continues, plastic deformation accumulates, curve amplitude rises, and ductility decreases, indicating limited hysteretic energy dissipation and suitability for applications with minimal deformation demands. With increasing ITS content, concrete shows greater deformation amplitude and improved ductile characteristics. At 10% ITS, the deformation curve exhibits more noticeable fluctuations, with stable responses during both loading and unloading. Crack propagation becomes more gradual, and energy dissipation improves, indicating enhanced deformation coordination. At 20% ITS, deformation increases further, and hysteretic behavior becomes more evident, suggesting greater plastic energy absorption. Concrete containing 30%–40% ITS demonstrates the best combination of plastic deformation and energy dissipation. At 30% content, peak deformation gradually rises in later cycles, and cracks expand evenly, reflecting stable structural response and effective stress distribution. This level achieves a good balance between strength and ductility, making it suitable for structural elements in seismic environments where energy dissipation and deformation control are critical30. At a 40% iron tailings sand content, the concrete exhibits further improvement in energy absorption capacity. The stress–strain curve remains stable, with an enlarged hysteresis loop area indicating efficient energy dissipation. Crack propagation is consistent and evenly distributed, highlighting enhanced ductility and structural integrity. These characteristics make this mix particularly suitable for applications requiring high energy absorption and seismic resilience. However, when the content increases to 50%, although energy dissipation capacity improves, curve stability declines, crack propagation accelerates, and the risk of local failure increases. Concrete with 50% iron tailings sand content is suitable for high-strength applications but has lower deformation adaptability. At 60% iron tailings sand content, deformation increases rapidly, with sharp and irregular peak intervals in the later loading stages, exhibiting significant brittle failure characteristics. High content leads to increased porosity, accelerated crack propagation, reduced structural stability, and unsuitability for high-cycle load environments.

Cumulative residual strain

Figure 9 presents the loading and unloading deformation modulus of specimens under cyclic compression. As shown in Fig. 9, both loading and unloading deformation modulus gradually increase with the number of cyclic compressions. However, near failure, the loading deformation modulus exhibits a negative growth trend, whereas the unloading deformation modulus does not show similar behavior. The primary reason is that cyclic compression reduces the original load-bearing capacity of concrete, essentially causing increasing internal damage. A comparative analysis shows that for the same number of cyclic compressions, the unloading deformation modulus is consistently greater than the loading deformation modulus, particularly near failure, where the difference between the two becomes more pronounced. During the loading path, concrete undergoes compaction damage, resulting in irreversible deformation but not structural damage. Therefore, in the unloading path, the deformation of concrete is smaller than during loading, ultimately leading to a lower loading deformation modulus than the unloading deformation modulus.

Fig. 9
figure 9

Loading and unloading deformation modulus.

Full size image

Figure 9.a shows the variation in loading deformation modulus of concrete with different iron tailings sand (ITS) contents under cyclic compression. For all mixtures, the modulus initially increases with the number of cycles before gradually stabilizing. However, the rate and magnitude of increase are clearly influenced by ITS content. At 0% ITS, ordinary concrete displays a sharp modulus increase during early cycles, reflecting high initial stiffness. As loading continues, the growth rate slows, indicating stiffness degradation due to microcrack development and reduced load-bearing capacity. Concrete with 10%–20% ITS exhibits higher peak modulus and faster early-stage growth than the control group. This suggests that moderate ITS content improves microstructure, limits crack propagation, and enhances both stiffness and recovery behavior. The best performance is observed at 30%–40% ITS, where concrete demonstrates the highest loading modulus and a stable growth pattern, indicating a balance of strength, ductility, and structural integrity during cyclic loading31. At 40% content, the modulus reaches its peak value, making it well-suited for structural applications requiring both strength and deformation resistance. When ITS content increases to 50% and 60%, modulus growth slows and becomes more erratic. This implies that excessive ITS may promote early microcrack initiation and increased porosity, ultimately reducing stiffness and stability.

Figure 9.b presents the unloading deformation modulus trends. With increasing ITS content, the modulus during unloading also rises, particularly in the 30%–40% range, where the most pronounced improvement is observed. For concrete with 0% and 10% ITS, the unloading modulus increases slowly, indicating good elastic recovery but limited energy dissipation. At 20% ITS, the modulus begins to increase more rapidly, reflecting enhanced ductility and energy absorption capacity. Concrete with 40% ITS achieves the highest unloading modulus, suggesting optimal toughness and energy dissipation under cyclic conditions8. Beyond 40%, further increases in ITS lead to reduced growth rates and lower elastic recovery. At 50%–60%, brittleness and microstructural instability become more apparent, highlighting the potential for long-term degradation. These findings emphasize the importance of controlling ITS content to ensure consistent performance in cyclic loading environments.

Deformation modulus behavior characteristics

In cyclic compression, cumulative residual strain is a critical parameter for evaluating the plastic deformation capacity and damage accumulation of concrete. As the number of loading cycles increases, microcracks within the concrete gradually propagate and develop, leading to the continuous accumulation of residual strain. This study recorded the residual strain of concrete specimens with different iron tailings sand (ITS) contents under various loading cycles and plotted the strain-loading cycle curves, as shown in Fig. 10.

Fig. 10
figure 10

Cumulative residual strain.

Full size image

During cyclic loading, concrete specimens with different ITS contents exhibited a general trend of increasing cumulative residual strain with the number of loading cycles. However, the growth rate and magnitude varied significantly across different ITS content levels. In the initial loading phase (1–5 cycles), residual strain increased rapidly, demonstrating significant plastic deformation characteristics. This behavior is attributed to the initial development of microcracks and the accumulation of inelastic deformation in the material. As the number of cycles increased, the growth rate of residual strain gradually declined and eventually stabilized, indicating that the concrete structure reached a stable state after multiple loading cycles, with its plastic deformation capacity approaching a limit.

From the perspective of ITS content influence, cumulative residual strain generally increased with higher ITS content, indicating that concrete with a high ITS proportion is more susceptible to plastic deformation under cyclic loading, with more pronounced damage accumulation effects. In the 30%-40% ITS content range, the residual strain growth was relatively moderate, and the material exhibited good deformation resistance, maintaining structural stability in cyclic loading conditions. Concrete within this ITS content range demonstrated strong seismic performance and excellent durability, making it suitable for engineering applications under high dynamic load conditions. However, when ITS content reached 50%-60%, cumulative residual strain increased significantly, and the curve steepened, indicating a reduction in the material’s plastic deformation capacity. Additionally, microcrack propagation accelerated, leading to more severe strength degradation. Consequently, concrete with a high ITS content may experience substantial residual deformation accumulation under long-term cyclic loading, which could compromise structural stability. Therefore, in practical engineering applications, it is crucial to optimize ITS content to balance deformation capacity and strength durability, ensuring the long-term reliability of concrete structures.

Results and discussion

This study systematically analyzed the effects of iron tailings sand on the workability and cyclic compressive behavior of concrete. The results show that incorporating iron tailings sand significantly improves the mechanical properties and deformation characteristics of concrete, particularly within the 20%-40% replacement range, where it exhibits optimal plastic deformation capacity and energy absorption ability. Specifically, concrete with 10%-40% iron tailings sand demonstrates enhanced toughness and ductility under multiple cyclic loading conditions, with increasing hysteresis energy, indicating strong energy absorption capability. Concrete with 30%-40% iron tailings sand achieves an excellent balance between strength, toughness, and durability, making it suitable for structures requiring high seismic performance.

When the iron tailings sand content exceeds 40%, the mechanical properties and stability of concrete begin to deteriorate. Concrete with 50% and 60% iron tailings sand exhibits lower stiffness and higher plastic deformation, with greater fluctuations in the stress–strain curve and accelerated crack propagation, leading to reduced structural strength and stability. This indicates that excessive iron tailings sand may increase porosity and inter-particle friction, weakening the lubrication effect and the cementitious matrix’s ability to encapsulate aggregates. In engineering applications, controlling the iron tailings sand content is crucial. A replacement ratio of 20%-40% can significantly enhance the compressive strength, durability, and deformation resistance of concrete, making it suitable for high-strength and high-ductility projects. However, replacement levels above 50% should be used cautiously, especially in applications requiring high deformation capacity, as excessive content may reduce concrete’s ductility and crack resistance.

Compared with previous studies, the findings of this work show both consistencies and extensions. For instance, the improvement in compressive strength at 30–40% ITS content aligns with the results of Shi et al.13, who demonstrated that partial replacement with iron tailings can enhance strength due to refined pore structures. Similarly, Ling et al.29 also observed improved cyclic performance in tailings-based concrete, consistent with our findings regarding enhanced energy dissipation and ductility. However, unlike Garcia-Troncoso et al.8, who reported only marginal benefits at high tailings replacement, our results indicate a more pronounced deterioration beyond 40% content, likely due to increased porosity and reduced interfacial bonding. These differences highlight the role of particle morphology and replacement ratio, confirming that moderate ITS content improves structural performance, while excessive incorporation undermines mechanical integrity. Therefore, this study not only validates earlier conclusions but also provides extended insights into the cyclic behavior and cumulative deformation characteristics under dynamic loading, offering practical guidance for seismic engineering applications. The rational utilization of iron tailings sand not only improves concrete performance but also reduces the dependence on natural sand, contributing to resource conservation and environmental protection. However, in practical applications, its content should be carefully controlled based on specific engineering requirements to maximize its benefits while avoiding potential drawbacks associated with excessive replacement levels. The performance trends observed in this study are closely tied to the microstructural evolution induced by varying ITS content. At 30%–40% replacement, the fine, angular particles of iron tailings sand enhance packing density and promote the formation of a dense interfacial transition zone (ITZ), improving both strength and energy dissipation. However, at higher contents, excessive fines increase internal porosity and disrupt the continuity of the cementitious matrix, weakening the load-bearing skeleton. These results highlight the importance of particle grading and surface texture in tailoring concrete microstructure. Despite these findings, the study has some limitations. Only one ITS grading was used, which may not capture the full range of effects from particle size distribution. Furthermore, compatibility between ITS and different binder types (e.g., high-SCM or alkali-activated systems) was not explored. Future work should examine these factors to expand the applicability of ITS in diverse cementitious systems. From a practical perspective, concrete incorporating 30%–40% ITS offers an effective balance of strength, ductility, and durability, making it suitable for use in earthquake-resistant structures, industrial floors subjected to cyclic loads, and underground support elements where energy absorption and deformation control are essential.

The experimental findings of this study, particularly the quantitative relationship between ITS content and key mechanical indicators such as strength, deformation, and energy dissipation, provide a solid foundation for the integration of machine learning (ML) techniques. By using these experimentally derived parameters as training data, ML models such as support vector regression, random forest, or artificial neural networks can be developed to predict the performance of ITS concrete under various mix designs and loading conditions. As highlighted by recent studies32, ML-based frameworks can effectively capture nonlinear material behavior and optimize mix proportioning in complex systems. Therefore, future work could implement predictive models trained on ITS-related datasets to improve design accuracy, reduce trial costs, and support intelligent decision-making in concrete mix design.