Smart self-healing concrete infused with nanomaterials for sustainable construction and real-time structural monitoring

ABSTRACT

The multi-functional polymeric EcoFlexFiber was used in the present research for its potential to improve concrete's performance in sustainable construction and real-time structural monitoring. A 2% volume fraction of EcoFlexFiber was incorporated into the concrete mixture, consisting of a load-bearing core fibre, a chitosan-based hydrogel sheath, and a polycaprolactone outer layer. This research reported notable enhancements in mechanical and durability properties of concrete. The compressive strength increased from 32.5 MPa at 7 days to 54.8 MPa at 28 days, and flexural strength improved from 3.21 MPa to 5.12 MPa over the same period. Split tensile strength also showed a very significant increase, from 3.20 MPa at 7 days to 5.01 MPa at 28 days. Water absorption tests showed reductions in porosity, both at 7 days by 6.57% and at 28 days by 12.32%, which indicated enhancement in durability against moisture influx. Thermal analysis showed satisfactory heat distribution; the surface achieves 100°C while stabilising at 85% in the core, which speaks of the thermal resistance characteristic of the fibre. These results reinforce the effectiveness of EcoFlexFiber in improving concrete mechanical properties, durability, and thermal performance, thus constituting a potential solution for sustainable and resilient construction.

Keywords:
Eco Flex Fiber; Sustainable construction; Self-healing concrete; Compressive strength; Flexural strength; Thermal analysis; Structural monitoring; Durability

1. INTRODUCTION

The construction industry is increasingly facing critical challenges related to sustainability, durability, and long-term maintenance of structures. With the world’s urbanisation rate at an all-time high, there is a growing demand for infrastructure that not only fulfils the needs of modern society but also minimises the impact on the environment. Though concrete is widely used in construction, it is prone to cracking and degradation from environmental stressors such as thermal variations, moisture, and mechanical loads. Forming micro-cracks often serves as a precursor to subsequent larger fractures that might occur during longer periods of time and is the most common cause for the reduced longevity of concrete structures. There has never been a greater demand to have more sustainable construction materials that could reduce the expenses of maintenance and extend the lifespan of buildings and other infrastructures. It was in this context that a new concept, that of self-healing concrete, emerged as a possible alternative [¹,²,³].

Despite the good promises for self-healing concrete, existing materials and technologies have several limitations. The most used self-healing systems contain microencapsulated healing agents or bacterial spores, which release healing agents based on crack widths. Nonetheless, these systems present numerous shortcomings in healing efficiency, durability, and repair capacity with regard to different sizes of cracks. Many of these systems lack the ability to monitor structural health in real-time, making it difficult to assess the effectiveness of the healing process or predict when repairs are needed. Clearly, a more advanced solution is called for: a material that enhances the healing process yet also incorporates real-time monitoring capabilities to ensure the continuing health and stability of the structure. This is where multifunctional materials, like EcoFlexFiber [⁴,⁵,⁶], come in. This research has a high potential to change the construction industry in the sense that it may provide a more sustainable and resilient form of concrete. Integration of multifunctional fibres like EcoFlexFiber could reduce the environmental footprint of construction not only by enhancing the durability of structures but also by reducing the need for resource-intensive repairs. Such capability might allow for more efficient resource management and earlier detection of damage or reduction in overall maintenance costs if concrete health can be monitored in real time. Also, this research can be helpful for the general area of smart materials as insights into the design of future construction materials combining structural enhancement and intelligent monitoring capabilities. This research effort will eventually provide a basis for concrete materials that are self-healing but also can provide a real-time indication of their condition to support the future development of sustainable, smart infrastructure [⁷,⁸,⁹].

Self-healing concrete is a relatively newer innovation that can be used for addressing the cracks and damage in a concrete structure. This has been proposed to improve its durability and longevity by introducing the property of self-healing in concrete by making it the ability to mend cracks that become visible with time. Self-healing concrete technologies have come from different streams of work, each by a different method of healing. One of the early ideas is to introduce healing agents such as epoxy or polymer-based material that could be encapsulated into the concrete matrix. On cracking, these healing agents are released, and they further react with the surrounding environment for a healing process. In bacterial-based systems, bacteria embedded in the concrete would produce calcium carbonate by-product as a result of moist environments, thus sealing cracks. These methods have so far proved to be effective and feasible for crack repair; however, the factors are the limit for size in crack length, the healing agent that could be able to stand longer periods of time, and controlling the healing process for much more extended periods. In addition, most self-healing technologies focus mainly on the mechanism of repair and do not integrate real-time monitoring systems that can provide useful information about the structural health of the concrete [¹⁰,¹¹,¹²].

Nanomaterials such as carbon nanotubes, nanoclays, and nanosilica have been proven to enhance the mechanical properties and durability of concrete along with improving its crack-healing capacities. Nanomaterials may fill the pores of the matrix, enhance the bond between the matrix and aggregates, and increase the overall strength of the structure. Other nanomaterials are capable of interacting with their environment in ways that stimulate healing [¹³,¹⁴,¹⁵]. Despite the improvements in self-healing and nanomaterial-enhanced concrete, critical gaps remain. Most technologies are unable to heal wide or deep cracks that, in turn, can create weaknesses in the structural performance of the concrete. The self-healing process is long and sometimes insufficient for healing cracks of long duration and for fractures that occur under significant stress. Most current systems lack the ability to monitor the healing progress autonomously and provide feedback in real-time about the condition of concrete. With this, there is limited capability to make judgements of the effectiveness of the healing process or detect potential damage sufficiently early to avert more deterioration. Many of the existing self-healing concrete systems are not integrated well with structural monitoring systems, making it difficult to correlate healing efficiency with changes in the structural health of the concrete [¹⁶,¹⁷,¹⁸,¹⁹]. EcoFlexFiber addresses these gaps through a combination of multiple functionalities into a single fibre system that improves the self-healing capability along with the real-time monitoring of concrete. Integrating a load-bearing core, chitosan-based hydrogel sheath for controlled release of healing agents, and the polycaprolactone outer layer makes up EcoFlexFiber to more effectively heal cracks of various sizes. The embedded fibre optic sensors continuously monitor stress, strain, and conductivity and give real-time data about the health of the concrete structure. This multi-function approach heals the material but also aids in the development of smart materials for concrete, giving information about its condition so that proactive maintenance is done to ensure long-term structural integrity [²⁰,²¹,²²].

This research discusses developing a novel self-healing concrete system using the multiple functionality polymeric fibre of EcoFlexFiber to upgrade the mechanical properties of the concrete with self-healing functionality. EcoFlexFiber includes an inner core that can support load, a chitosan-based hydrogel layer that supports controlled release healing agents, and a surface layer made of PCL that shows damage responsiveness. This newly developed fibre embeds the three necessary functions within the concrete matrix: controlled delivery of healing agents, redistributing the stress through bridging actions of the fibres and self-reinforcing actions through crystalline precipitation. Such properties are likely to enhance both strength and durability but also offer the ability for autonomous healing after structural damage is inflicted. Further, the EcoFlexFiber is to function in concert with real-time structural monitoring technologies so the embedded sensors inside the fibre can continuously evaluate stress and strain and conductivity, so these are critical data for maintenance and long-term monitoring purposes.

2. MATERIALS AND METHODS

2.1. Materials

As presented in Figure 1, the EcoFlexfiber is an advanced material capable of optimising concrete performance; it comprises three different pieces that act in synergy to heal better, distribute stress, and respond better to damage. To be precise, the key structural component of the fibre is a load-bearing core fibre. This core fibre is composed of high-strength synthetic material like aramid or basalt, known for their high tensile strengths and durability. These fibres are treated with a silane coupling agent to ensure that the interface between the fibre and concrete matrix has good adhesion, which is very necessary for the transfer of the load and distribution of stresses. The core fibre provides mechanical reinforcement to the EcoFlexFiber so that it can withstand significant loads and forces usually encountered in concrete structures while also contributing to its role in bridging cracks and redistributing stress.

Figure 1
Methodology.

Surrounding the core fibre is a chitosan-based hydrogel sheath, which is pivotal for the controlled release of healing agents. Chitosan is a biodegradable polymer derived from chitin and is selected for the property to form a gel-like structure by cross-linking with glutaraldehyde. The hydrogel sheath encases the healing agents within a stable and controlled environment such that the healing agents are released gradually with crack development. Besides healing, the chitosan-based hydrogel also encourages mineral precipitation due to the presence of calcium carbonate, which fills voids and restores the concrete’s structural integrity. This is one of the most important components of the EcoFlexFiber, as it sustains the healing process over time, providing a long-term solution to damage. The outer layer of EcoFlexFiber is composed of polycaprolactone, a biodegradable thermoplastic polymer. This PCL layer acts as a protective wrapper, protecting the hydrogel sheath from environmental sources like moisture, temperature shifts, and mechanical wear from the outside. It will also allow the fibre to respond to damage by delivering healing agents when cracks initiate. PCL is a thermoplastic material that melts and re-solidifies, which is one of the reasons why the EcoFlexFiber is damage-responsive. The outer layer would ensure that the EcoFlexFiber remains intact while also responding to the structural needs of the concrete. The chitosan-based hydrogel sheath and the load-bearing core, along with the polycaprolactone outer layer, form a multifunctional material that increases the mechanical properties and the self-healing potential of concrete.

Table 1 provides the material composition used in this research. The concrete mix formulated for this research contains well-chosen materials and additives to improve its mechanical and durability properties as well as self-healing efficiency. Fine aggregates are required, which are natural sands with particle sizes less than 4.75 mm. These aggregates help in improving the flowability of the concrete mixes, enhance the overall packing density of the matrix, and take a crucial role in achieving a smooth and cohesively mixed concrete mix. Superplasticisers are added to further improve the performance of the mix, which are high-range water-reducing agents. Calcium chloride is added to the mix as an accelerator to increase early strength. This compound is particularly useful in decreasing the setting time of concrete and increasing its resistance to freeze-thaw cycles. In addition, rice husk ash is added as a partial replacement for cement because it is a pozzolanic material. Rice husk ash with high silica content reacts with calcium hydroxide when hydration occurs, and in this process, additional C-S-H gel is created, which improves strength while reducing permeability. In addition, the corrosion inhibitor calcium nitrite is included in the mix to prevent the steel reinforcement in the concrete from chloride-induced corrosion. Calcium nitrite forms a protective layer on the surface of the steel, thus prolonging the lifetime of the structure. Collectively, these materials and additives lead to a high-performance mix of concrete suitable for sustainability in construction and durability improvements [²³]. To evaluate the extent of cracking and monitor the healing efficiency, Ultrasonic Pulse Velocity Testing (UPVT) was employed as a non-destructive testing method. The test was conducted in accordance with ASTM C597 using a portable UPV device with transducers placed on opposite sides of the concrete specimens. The pulse transit time was measured, and the velocity of the ultrasonic wave was calculated. A reduction in pulse velocity indicated the presence of internal microcracks or discontinuities, while an increase in velocity after the healing period suggested the closure or bridging of cracks due to the effect of EcoFlex Fiber and the associated healing mechanisms. This method allowed for indirect quantification of crack healing and provided a reliable assessment of the internal integrity of the concrete without causing any damage to the specimens.

Table 1
Material composition.

COMPONENT	CHEMICAL COMPOSITION	PROPERTIES
Load-bearing Core-Fiber	Aramid (Poly-paraphenyleneterephthalamide) (Silica, Alumina, Iron Oxide)	Tensile Strength: 2500–4000 MPa (Aramid) / 1000–2500 MPa (Basalt)
		Modulus of Elasticity: 70–120 GPa (Aramid) / 50–70 GPa (Basalt)
		Density: 1.44 g/cm3 (Aramid) / 2.65 g/cm3 (Basalt)
		Thermal Stability: Up to 400°C (Aramid) / 600°C (Basalt)
Chitosan-Based Hydrogel Sheath	Chitosan (C6H11NO4) Glutaraldehyde (C5H8O2) Calcium Carbonate (CaCO3)	Gelation Point: 25–30°C
		Cross-Linking Density: 50–80% (by weight)
		Water Absorption: 500–1000% (based on dry weight of chitosan)
		Biodegradability: Fully biodegradable in natural environments
		pH Sensitivity: Slightly acidic to neutral (pH 4-7)
		Mineral Precipitation: Facilitates formation of calcium carbonate in cracks
Polycaprolactone Outer Layer	Polycaprolactone (C6H10O2)n	Glass Transition Temperature (Tg): −60°C
		Melting Point: 60–65°C
		Density: 1.14 g/cm3
		Tensile Strength: 30–50 MPa
		Biodegradability: Fully biodegradable within 2–3 years
		Flexibility: High due to thermoplastic properties (can be reshaped when heated)
		Degradation Rate: Controlled over time based on environmental conditions (moisture, temperature)

2.2. EcoFlexFiber preparation

The process of manufacturing EcoFlexFiber is an elaborate, step-by-step procedure for achieving multifunctional properties presented in Figure 2. It begins with the fabrication of the load-bearing core fibre. For the synthesis, high-strength synthetic fibres like aramid or basalt are used for their tensile strength superiority and cementitious material compatibility. The fibres are then treated with a 2% silane coupling agent solution to provide improved adhesion with the surrounding concrete matrix. The fibres are then drawn into strands with a uniform diameter of 0.5 mm, thereby ensuring consistency in load transfer and mechanical performance.

Figure 2
EcoFlexFiber preparation.

The second step is the production of the chitosan-based hydrogel sheath. This serves as a matrix for the controlled release of healing agents. The 2% acetic acid solution is used to dissolve the chitosan powder and is stirred constantly until uniformity is achieved. Glutaraldehyde at 0.5% is added as the cross-linking agent in order to make it gel-like, while 10% calcium carbonate is added to promote mineral precipitation in the hydrogel. With prepared hydrogel, the surface of the core-fiber receives hydrogel dip coat followed by slow withdrawal where they make even coats. The coat-dipped fibers are hardened for 24 hours under conditions at 25°C after the hydrogel layer hardening stabilizes. Finally, the polycaprolactone outer layer is applied to damage responsiveness and protect the hydrogel sheath. The PCL pellets are melted at 60°C and dissolved in dichloromethane in order to make a viscous solution. Hydrogel-coated fibres are passed through the PCL solution, and then air-dried in order to get a uniform outer coating. Then, heat treatment at 50°C was carried out to enhance interlayer adhesion.

3. SAMPLE PREPARATION

As presented in the Figure 3, sample preparation for the evaluation of EcoFlexFiber in concrete will follow a defined process, hence ensuring consistency and reliability in performance. Concrete mix design will be based on 1:1.5:3 by weight of mix proportion, which includes fine aggregates and coarse aggregates, respectively, while ensuring the water-cement ratio is 0.4. Ordinary Portland Cement, OPC 53 Grade, was used as the binder, while fine aggregates included natural sand and coarse aggregates of size 20 mm. Additives include 1% superplasticiser by weight of cement for enhancing workability and 5% of rice husk ash that partially replaced cement to achieve durability and sustainability. 1% calcium nitrite and 2% calcium chloride by weight of cement are added to resist corrosion and accelerate early strength. As presented in the Table 2, five different types of specimens are prepared for thorough tests. Cubes of dimensions 150 mm × 150 mm × 150 mm are cast for compressive strength tests, while prisms of 100 mm × 100 mm × 500 mm are used to evaluate the flexural strength. Cylinders with a diameter of 150 mm and height of 300 mm are prepared for split tensile strength tests. Cubes of equal dimensions to that of compressive strength specimens are utilised for water absorption and porosity tests. Every type of specimen ensures that the mechanical, durability, and self-healing properties of concrete are adequately evaluated. The fibers of EcoFlex are added to the concrete mix at a volume fraction of 2%. They get uniformly distributed in the matrix. The addition of the fibers is done after incorporating aggregates and cement, ensuring they do not clump during mixing. The freshly prepared concrete is poured into the molds in three layers, compacted with the help of a vibrating table to eliminate air voids. After 24 hours, the specimens are demolded and cured in a water tank at 25°C for the specified curing periods of 7, 14, and 28 days. This sample preparation procedure ensures the reproducibility of results and provides for the comprehensive evaluation of the impact that EcoFlexFiber has on concrete performance.

Figure 3
Experiment samples preparation.

Table 2
Sample details.

SAMPLE TYPE	DIMENSIONS	PURPOSE	TEST STANDARD	SAMPLES
Cube	150 mm × 150 mm × 150 mm	Compressive Strength, Water Absorption	ASTM C39, ASTM C642	5
Prism	100 mm × 100 mm × 500 mm	Flexural Strength	ASTM C78	5
Cylinder	Ø150 mm × 300 mm	Split Tensile Strength	ASTM C496	5
Cube (Porosity Testing)	150 mm × 150 mm × 150 mm	Porosity Reduction	ASTM C642	5
Cube	150 mm × 150 mm × 150 mm	Thermal analysis	ASTM E1952	1

4. RESULT AND DISCUSSION

The results obtained from the experimental analysis highlight enhanced performance by incorporating EcoFlexFiber-integrated concrete, showcasing significant improvements in compressive strength, water absorption, flexural strength, split tensile strength, and porosity reduction. These parameters as a collective set highlight multifunctional benefits for the incorporation of EcoFlexFiber within sustainable construction and applications that involve structural health monitoring [²⁴].

As shown in Figure 4, the compressive strength results tested according to ASTM C39 indicate an increase with curing time across all specimens. The average compressive strength recorded at 7 days was 32.5 MPa, showing early strength gain because of the bonding effectiveness of EcoFlexFiber. The strength increased to an average of 54.8 MPa at 28 days, which is considerably higher than that of conventional concrete. The fibers effectively redistributed the stress through their bridging action, which reduced crack propagation and contributed to the load-carrying capacity of the matrix. Moreover, crystal precipitation from the chitosan-based hydrogel sheath was crucial for self-reinforcement, sealing voids, and increasing overall matrix density. This improvement in compressive strength highlights the potential of EcoFlexFiber to enhance structural reliability under compressive loads, thereby offering a promising solution for high-performance construction [²⁵]. Water absorption test results presented in the Figure 5, done according to ASTM C642, indicated a gradual increase in porosity reduction through the curing period, an indication of the concrete’s resistance to water penetration. For 7 days, porosity reduction was measured as 6.57%. This was increased to 12.32% at the end of 28 days. The reason for this would be due to the timed release of self-healing agents from the hydrogel sheath that sealed microcracks and voids with time. The damage-responsiveness of the external polycaprolactone layer guaranteed the stimulation of healing in wet/dry cycles, thus promoting a decrease in permeability. The significant reduction of water absorption manifests the durable characteristic of EcoFlexFiber-reinforced concrete towards providing superior resistance to moisture-activated deterioration and chloride invasion. This property is essential to ensure an increase in the service life of concrete structures in highly aggressive environments [²⁶].

Figure 4
Compressive strength of samples.

Figure 5
(a) Water absorption % of samples (b) initial dry weight and saturated weight (Kg) of samples.

The flexural strength test, carried out according to ASTM C78, indicated an improvement in terms of the inclusion of EcoFlexFiber. As shown in the Figure 6, The average flexural strength recorded at 7 days was 3.21 MPa, whereas at 28 days it was found to be 5.12 MPa. Tensile stresses were well resisted by load-bearing core fibre, along with its bridging properties across the cracks. Therefore, in addition to tensile bridging, flexural performance was further enhanced by fibre-matrix bonding. This release of healing agents to microcracks ensured that the specimens maintained their integrity upon bending loads. This gradual increase in flexural strength over time shows how the EcoFlexFiber contributes toward ductility and toughness the crucial parameters for withstanding dynamic and flexural stresses in reality [²⁷].

Figure 6
Breaking load (kN) and flexural strength (MPa) of samples.

Split tensile strength, tested according to ASTM C496, improved substantially with curing time, is as presented in Figure 7. For instance, at 7 days, the average split tensile strength was obtained as 3.20 MPa, and increased dramatically to 5.01 MPa by the 28th day. This was due to the bridging action of the EcoFlexFiber along with the stress redistribution properties of the core fiber. Additionally, the precipitation of crystals and healing of microcracks by the hydrogel sheath were important contributors to maintaining the cohesion of the matrix under tensile loading. The improvement in tensile strength thus offers potential in overcoming the inherent brittleness of concrete, especially for applications requiring enhanced tensile performance, such as pavement systems and earthquake-resistant structures.

Figure 7
(a) Tensile load (kN) of samples (b) tensile strength (MPa) of samples.

From Figure 8, Reductions in porosity results from testing according to ASTM C642 indicated that EcoFlexFiber was effective in filling the voids and microcracks within the matrix. Average porosity reduction after 7 days was at 6.57%, whereas an average of 12.32% was recorded at 28 days. These are due to the fact that damage-responsive activation of the polycaprolactone layer allows for targeted wet condition release of healing agents. The chitosan-based hydrogel sheath further contributed by encouraging mineral precipitation within the pores, thereby improving the impermeability of the matrix. The steady decline in porosity with time indicates that EcoFlexFiber improves durability and decreases susceptibility to moisture and chemical attack. This property is essential for ensuring long-term performance and sustainability in construction projects [²⁸].

Figure 8
(a) Porosity reduction% of samples (b) initial (top surface plot) and final (bottom surface plot) porosity % of samples.

The addition of EcoFlexFiber considerably enhances the mechanical and durability properties of concrete. Results from the experiment show its capability to mitigate some of the most pressing issues in sustainable construction and structural health monitoring, thereby providing a versatile, robust solution for modern engineering applications.

4.1. Thermal analysis

To calculate the heat transfer behaviour within the cube containing EcoFlexFiber by carrying out a controlled temperature gradient thermal analysis under the LS-DYNA analysis, a 150 mm × 150 mm × 150 mm cube is designed by simulating the cube as an enhanced thermal property homogeneous material with the inclusion of the fibre material. Experimental values of its thermal conductivity, specific heat capacity, and density were then input listed in the Table 3. The boundary conditions considered a constant initial temperature of 25°C for the whole cube and a surface-exposed temperature of 100°C to simulate an applied heat source. This simulation was done for 3600 seconds, which would be in the real-world heating. The bottom and neighbouring surfaces were made thermally insulated to prevent any other form of heat transfer but one directional. As presented in the Figure 9, the results were 100°C for maximum surface temperature, and the core of the cube stabilised at 85°C after 3600 seconds, meaning there was proper thermal resistance from EcoFlexFiber. Temperature gradient across the cube recorded 15°C. Such behaviour can be attributed to the role that the fibre played in heat redistribution without causing any sort of thermal hotspots. The simulation of this research shows how the distribution of heat with EcoFlexFiber reduces thermal stresses that enhance the durability and structural integrity of concrete under thermal loads. Thus, the application of EcoFlexFiber is demonstrated in various constructions with thermal variations, such as pavements, industrial floors, and high-temperature environments.

Table 3
Simulation Parameters.

Parameter	Cube dimension (150 mm × 150 mm × 150 mm)
Material	Concrete with EcoFlexFiber
Thermal conductivity	1.6 W/m·K
Specific heat capacity	900 J/kg·K
Density	2400 kg/m3
Initial temperature	25°C
Boundary conditions	Exposed surface temperature of 100°C
Simulation duration	3600 seconds (1 hour)
Maximum temperature	85°C (center of the cube)
Surface temperature	100°C
Temperature gradient	15°C from surface to core

Figure 9
Temperature profile of sample.

Figure 10 illustrates the Scanning Electron Microscope (SEM) images of the EcoFlex fiber-reinforced concrete before and after the healing process. As shown in the Figure 10, the image captured before healing reveals the presence of distinct microcracks within the concrete matrix, which are indicative of early-stage damage. After the healing process—achieved through the internal release of healing agents and fiber bridging mechanisms—the image taken at 28 days clearly shows a significant reduction in microcrack width, and in some areas, complete crack closure is observed. This visual evpptidence confirms the self-healing capability of EcoFlex Fiber, which plays a crucial role in enhancing the long-term durability and crack resistance of concrete by autonomously addressing internal damage.

Figure 10
(a) Before healing, (b) after healing.

5. CONCLUSION

This research has demonstrated the promising potential of EcoFlex Fiber as a multifunctional additive for enhancing concrete used in sustainable construction and structural health monitoring. Through comprehensive mechanical, durability, and thermal analyses, EcoFlex Fiber was shown to significantly improve concrete’s strength, resistance to moisture ingress, and ability to manage thermal gradients. The key findings include:

• Compressive Strength: Increased from 32.5 MPa at 7 days to 54.8 MPa at 28 days due to the fiber’s ability to redistribute stresses and reinforce the matrix.

• Water Absorption: Porosity decreased by 6.57% at 7 days and 12.32% at 28 days, indicating enhanced impermeability and durability.

• Flexural Strength: Improved from 3.21 MPa at 7 days to 5.12 MPa at 28 days, attributed to fiber bridging and activation of the healing mechanism.

• Split Tensile Strength: Increased from 3.20 MPa to 5.01 MPa over the same curing period, reflecting enhanced tensile resistance and crack control.

• Thermal Performance: A surface-to-core temperature gradient of 15°C was observed under thermal loading, confirming effective heat resistance and distribution due to EcoFlex Fiber.

• Overall, EcoFlexFiber provides a strong, sustainable solution for enhancing the mechanical properties and long-term durability of concrete, thus making it suitable for a wide range of construction applications.

• In addition, crack visualization using SEM image confirmed the healing capability by showing a visible reduction in microcrack formation post-healing, while Ultrasonic Pulse Velocity Testing (UPVT) was used as a non-destructive method to assess internal crack propagation and healing effectiveness.

• However, certain limitations exist in this study. The investigation primarily focused on short-term performance and limited thermal exposure conditions. Other influential parameters such as long-term durability under cyclic thermal loading, chemical resistance, freeze-thaw cycles, and large-scale structural application were not explored in this phase. Furthermore, a detailed economic analysis and fiber dosage optimization were not within the scope of this work.

• Future research should explore these parameters to validate the practical implementation of EcoFlex Fiber in diverse environmental and structural conditions. Despite the limitations, the current findings support the potential application of EcoFlex Fiber in critical infrastructure, pavements, industrial flooring, and high-temperature zones where durability and resilience are essential.

DATA AVAILABILITY

Data sharing is not applicable to this article as no new data were created or analysed in this research work.

6. BIBLIOGRAPHY

• ^[1] AZANDARIANI, M.G., VAJDIAN, M., ASGHARI, K., et al., “Mechanical properties of polyolefin and polypropylene fibers-reinforced concrete: an experimental study”, Composites Part C: Open Access, v. 12, pp. 100410, 2023. doi: http://doi.org/10.1016/j.jcomc.2023.100410.
  » https://doi.org/10.1016/j.jcomc.2023.100410
• ^[2] AKHTAR, A., SARMAH, A.K., “Construction and demolition waste generation and properties of recycled aggregate concrete: a global perspective”, Journal of Cleaner Production, v. 186, pp. 262–281, 2018. doi: http://doi.org/10.1016/j.jclepro.2018.03.085.
  » https://doi.org/10.1016/j.jclepro.2018.03.085
• ^[3] SINGH, D., CHAUDHARY, R., KARTHICK, A., et al., “Economic and life cycle cost analysis of building-integrated photovoltaic system for composite climatic conditions”, Environmental Science and Pollution Research International, v. 31, n. 9, pp. 13392–13413, 2024. doi: http://doi.org/10.1007/s11356-023-31781-1. PubMed PMID: 38244159.
  » https://doi.org/10.1007/s11356-023-31781-1
• ^[4] ROSHANI, H., YOUSEFI, M., GHARAEI-MOGHADDAM, N., et al., “Flexural performance of steel-concrete-steel sandwich beams with lightweight fiber-reinforced concrete and corrugated-strip connectors: experimental tests and numerical modeling”, Case Studies in Construction Materials, v. 18, pp. e02138, 2023. doi: http://doi.org/10.1016/j.cscm.2023.e02138.
  » https://doi.org/10.1016/j.cscm.2023.e02138
• ^[5] MA, R.Y., YANG, J., PENG, G.F., “Influence of steel fiber types on residual mechanical properties and explosive spalling of hybrid fiber reinforced ultra-high performance concrete: optimization and evaluations”, Case Studies in Construction Materials, v. 19, pp. e02538, 2023. doi: http://doi.org/10.1016/j.cscm.2023.e02538.
  » https://doi.org/10.1016/j.cscm.2023.e02538
• ^[6] NATRAYAN, L., JANARDHAN, G., NADH, V.S., et al., “Eco-friendly zinc oxide nanoparticles from Moringa oleifera leaf extract for photocatalytic and antibacterial applications”, Clean Technologies and Environmental Policy, pp. 1–13, 2024. doi: http://doi.org/10.1007/s10098-024-02814-1.
  » https://doi.org/10.1007/s10098-024-02814-1
• ^[7] ABBAS, H., ABADEL, A., ALMUSALLAM, T., et al., “Experimental and analytical study of flexural performance of concrete beams reinforced with hybrid of GFRP and steel rebars”, Engineering Failure Analysis, v. 138, pp. 106397, 2022. doi: http://doi.org/10.1016/j.engfailanal.2022.106397.
  » https://doi.org/10.1016/j.engfailanal.2022.106397
• ^[8] MOLLAH, M.T., COMMINAL, R., DA SILVA, W.R.L., et al., “Computational fluid dynamics modelling and experimental analysis of reinforcement bar integration in 3D concrete printing”, Cement and Concrete Research, v. 173, pp. 107263, 2023. doi: http://doi.org/10.1016/j.cemconres.2023.107263.
  » https://doi.org/10.1016/j.cemconres.2023.107263
• ^[9] TU, H., WEI, Z., BAHRAMI, A., et al., “Recent advancements and future trends in 3D concrete printing using waste materials”, Developments in the Built Environment, v. 16, pp. 100187, 2023. doi: http://doi.org/10.1016/j.dibe.2023.100187.
  » https://doi.org/10.1016/j.dibe.2023.100187
• ^[10] LYU, Q., DAI, P., CHEN, A., “Sandwich-structured porous concrete manufactured by mortar-extrusion and aggregate-bed 3D printing”, Construction & Building Materials, v. 392, pp. 131909, 2023. doi: http://doi.org/10.1016/j.conbuildmat.2023.131909.
  » https://doi.org/10.1016/j.conbuildmat.2023.131909
• ^[11] VIVEK, S.S., KARTHIKEYAN, B., BAHRAMI, A., et al., “Impact and durability properties of alccofine-based hybrid fibre-reinforced self-compacting concrete”, Case Stud. Constr. Mater, v. 19, pp. e02275, 2023. doi: http://doi.org/10.1016/j.cscm.2023.e02275.
  » https://doi.org/10.1016/j.cscm.2023.e02275
• ^[12] WANG, D., REN, B., CUI, B., et al., “Real-time monitoring for vibration quality of fresh concrete using convolutional neural networks and IoT technology”, Automation in Construction, v. 123, pp. 103510, 2021. doi: http://doi.org/10.1016/j.autcon.2020.103510.
  » https://doi.org/10.1016/j.autcon.2020.103510
• ^[13] ASHOK GANDHI, R., JAYASEELAN, V., PALANI KUMAR, K., et al., “Effect of carbon nano tubes (CNT) on hardness of polypropylene matrix”, In: Advances in Materials and Metallurgy: Select Proceedings of ICEMMM 2018, pp. 261–270, Singapore, 2018. doi: http://doi.org/10.1007/978-981-13-1780-4_26.
  » https://doi.org/10.1007/978-981-13-1780-4_26
• ^[14] CHU, S.H., UNLUER, C., YOO, D.Y., et al., “Bond of steel reinforcing bars in self-prestressed hybrid steel fiber reinforced concrete”, Engineering Structures, v. 291, pp. 116390, 2023. doi: http://doi.org/10.1016/j.engstruct.2023.116390.
  » https://doi.org/10.1016/j.engstruct.2023.116390
• ^[15] MOSTAFA, S.A., TAYEH, B.A., ALMESHAL, I., “Investigation the properties of sustainable ultra-high-performance basalt fibre self-compacting concrete incorporating nano agricultural waste under normal and elevated temperatures”, Case Studies in Construction Materials, v. 17, pp. e01453, 2022. doi: http://doi.org/10.1016/j.cscm.2022.e01453.
  » https://doi.org/10.1016/j.cscm.2022.e01453
• ^[16] SHI, F., PHAM, T.M., HAO, H., et al., “Post-cracking behaviour of basalt and macro polypropylene hybrid fibre reinforced concrete with different compressive strengths”, Construction & Building Materials, v. 262, pp. 120108, 2020. doi: http://doi.org/10.1016/j.conbuildmat.2020.120108.
  » https://doi.org/10.1016/j.conbuildmat.2020.120108
• ^[17] VAIRAGADE, V.S., DHALE, S.A., “Impact resistance of hybrid steel fiber reinforced concrete”, Hybrid Advances, v. 3, pp. 100048, 2023. doi: http://doi.org/10.1016/j.hybadv.2023.100048.
  » https://doi.org/10.1016/j.hybadv.2023.100048
• ^[18] ALWESABI, E.A.H., BAKAR, B.H.A., ALSHAIKH, I.M.H., et al., “Experimental investigation on fracture characteristics of plain and rubberized concrete containing hybrid steel-polypropylene fiber”, Structures, v. 33, pp. 4421–4432, 2021. doi: http://doi.org/10.1016/j.istruc.2021.07.011.
  » https://doi.org/10.1016/j.istruc.2021.07.011
• ^[19] LIU, Z., LI, M., QUAH, T.K.N., et al., “Comprehensive investigations on the relationship between the 3D concrete printing failure criterion and properties of fresh-state cementitious materials”, Additive Manufacturing, v. 76, pp. 103787, 2023. doi: http://doi.org/10.1016/j.addma.2023.103787.
  » https://doi.org/10.1016/j.addma.2023.103787
• ^[20] MUHYADDIN, G.F., “Mechanical and fracture characteristics of ultra-high performance concretes reinforced with hybridization of steel and glass fibers”, Heliyon, v. 9, n. 7, pp. e17926, 2023. doi: http://doi.org/10.1016/j.heliyon.2023.e17926. PubMed PMID: 37456004.
  » https://doi.org/10.1016/j.heliyon.2023.e17926
• ^[21] SHI, C., JIN, S., JIN, K., et al., “Improving bonding behavior between basalt fiber-reinforced polymer sheets and concrete using multi-wall carbon nanotubes modified epoxy composites”, Case Studies in Construction Materials, v. 18, pp. e02216, 2023. doi: http://doi.org/10.1016/j.cscm.2023.e02216.
  » https://doi.org/10.1016/j.cscm.2023.e02216
• ^[22] CUCUZZA, R., ALOISIO, A., ACCORNERO, F., et al., “Size-scale effects and modelling issues of fibre-reinforced concrete beams”, Construction & Building Materials, v. 392, pp. 131727, 2023. doi: http://doi.org/10.1016/j.conbuildmat.2023.131727.
  » https://doi.org/10.1016/j.conbuildmat.2023.131727
• ^[23] HAMMAD, N., EL-NEMR, A., SHAABAN, I.G., “The efficiency of calcium oxide on microbial self-healing activity in Alkali-Activated Slag (AAS).”, Applied Sciences, v. 14, n. 12, pp. 5299, 2024. doi: http://doi.org/10.3390/app14125299.
  » https://doi.org/10.3390/app14125299
• ^[24] SHAABAN, S., HAMMAD, N., ELNEMR, A., et al., “Efficiency of bacteria-based self-healing mechanism in concrete”, Materials Science Forum, v. 1089, pp. 135–143, 2023. doi: http://doi.org/10.4028/p-tc6w54.
  » https://doi.org/10.4028/p-tc6w54
• ^[25] HAMMAD, N., EL-NEMR, A., SHAABAN, I.G., “Bacillus subtilis as a novel biological repair technique for alkali-activated slag towards sustainable buildings”, Sustainability, v. 17, n. 1, pp. 48, 2025. doi: http://doi.org/10.3390/su17010048.
  » https://doi.org/10.3390/su17010048
• ^[26] HAMMAD, N., ELNEMR, A., SHAABAN, I., “Enhancing durability in bacteria-based AAS composites at varied alkali environments”, Progress in Engineering Science, v. 2, n. 1, pp. 100047, 2025. doi: http://doi.org/10.1016/j.pes.2024.100047.
  » https://doi.org/10.1016/j.pes.2024.100047
• ^[27] HASSANIN, A., EL-NEMR, A., SHAABAN, H.F., et al., “Coupling behavior of autogenous and autonomous self-healing techniques for durable concrete”, International Journal of Civil Engineering, v. 22, n. 6, pp. 925–948, 2024. doi: http://doi.org/10.1007/s40999-023-00931-4.
  » https://doi.org/10.1007/s40999-023-00931-4
• ^[28] SHAABAN, I., EL NEMR, A., AHMED, H., “Spotlight on mechanical properties of autogenic self-healing of concrete”, In: 2nd International Summit on Civil, Structural, and Environmental Engineering, Florence, Italy, 18–20 March 2024.

Publication Dates

• Publication in this collection
  11 Aug 2025
• Date of issue
  2025

History

• Received
  25 Dec 2024
• Accepted
  03 June 2025