Comparative study on the effect of natural and synthetic fibers on the production of sustainable concrete

1 Introduction

Concrete and mortar are extensively utilized in the construction industry as they possess properties like high resistance to fire and compression, long-term durability, and also lower permeability, making them ideal building materials [1,2]. Bheel et al. investigated the environmental impact of Portland cement production and explored supplementary cementitious materials, like wheat straw ash, and natural fibers, such as coir fibers (CFs), as sustainable alternatives. These materials enhance concrete’s mechanical properties, reduce permeability, and lower embodied carbon, addressing strength deficiencies effectively. Sridhar et al. explored the incorporation of natural fibers, such as jute and bamboo, and silica fume (SF) in concrete to enhance its mechanical properties. Artificial neural network (ANN) models, including Levenberg–Marquardt and gradient descent methods, accurately predict results, validating the improved performance of fiber-reinforced concrete with microscopic analysis support, and this study also highlights natural fibers, such as bamboo and jute, as sustainable alternatives to synthetic fibers in concrete reinforcement. Pre-treated fibers at optimal dosages of 1.5% bamboo and 2% jute significantly enhance compressive and flexural strengths [3]. Scanning electron microscopy (SEM) analysis confirms strong fiber–matrix bonding and reveals failure due to fiber pullout and debonding. Mahesh et al.’s research on natural-fiber-reinforced composites (NFRCs) has grown significantly across various sectors. This study employs scientometric and network analysis on 1,143 articles (2010–2022) to track research trends and impacts. The findings offer valuable insights for new researchers, highlighting the evolving focus and interdisciplinary applications of NFRC studies. Katman et al.’s study highlights the growing interest in using natural fibers like coir in high-strength concrete due to their cost-effectiveness and availability. Bheel et al.’s study shows that CFs enhance compressive, tensile, and flexural strength while reducing permeability, indicating coir’s potential to improve concrete’s durability and mechanical properties for advanced applications. Bheel et al.’s study indicates that graphene oxide (GO) significantly enhances the mechanical properties of engineered cementitious composites, improving compressive and tensile strength and modulus of elasticity and reducing water absorption. Optimal performance is observed with 0.08% GO, attributed to improved bonding between polyvinyl alcohol fibers and the cement matrix. Yet, despite those beneficial features, i  possesses some unfavorable impacts, such as brittleness, less tensile strength, and low resistance to cracking. Fibers are recommended as a reinforcing material to counteract these effects [2]. To reduce the likelihood of breaking due to shrinking and improve the material’s mechanical properties, tenacity, and longevity, fibers can be used. The effectiveness of fibers is primarily determined by characteristics such as their shape, proportion, diameter, length, and bonding with cement. Polypropylene (PP), glass, steel, and even natural fibers like kenaf, hemp, flax, cotton, coconut, jute, and sisal are widely added to enhance the qualities of mortar and concrete mixtures [4,5]. Synthetic PP fibers are man-made fibers that have similar properties as natural fibers and are widely used as reinforcing materials in construction materials [6]. They are known for their high strength, durability, and resistance to chemicals. They are often used as a replacement for traditional fibers in construction materials due to their low cost and ease of production. Umar et al.’s study highlights that the substitution of ordinary cement with ceramic waste powder in concrete production can reduce cement use and CO₂ emissions by up to 30%. In Oman, this equates to reducing emissions from 8.81 to 6.167 megaton/year, promoting sustainable waste utilization and environmental benefits [7]. Akbar et al.’s study demonstrates that incorporating 2% human hair fibers and 15% SF as a cement replacement significantly enhances concrete’s mechanical properties. The compressive, flexural, and split tensile strengths improved by 14, 8, and 7, respectively, validating the benefits of sustainable concrete innovations. Akbar et al.’s [8]. study highlights the significant impact of recycled steel fibers (RSFs) from waste tires on enhancing concrete’s mechanical properties, with compressive, split tensile, and flexural strengths increasing by up to 78, 149, and 157%, respectively. RSFs offer a sustainable alternative to industrial steel fibers, promoting eco-friendly construction practices [9]. Hemp fibers are derived from the stem of the hemp plant and are known for their durability and strength. They have been used for centuries in construction materials and are becoming increasingly popular as a sustainable alternative to traditional fibers. Luffa sponge fibers are obtained from the luffa plant, which is a tropical vine. These fibers are known for their flexibility and mechanical properties, and they are often used in construction materials as well as in industrial applications [10]. However, a critical distinction lies in their origin. Unlike natural fibers, which are renewable and biodegradable, synthetic PP fibers are petroleum-based and non-biodegradable. This distinction underscores the environmental considerations when choosing between these materials in construction applications.

Synthetic composite fibers used to strengthen reinforced constructions have been extensively researched for decades. Using a mortar matrix composed of fly ash and 0.08% polymer fibers, Kheradmand found that cracking shrinkage could be reduced by four times [11]. Toughness index and flexural strength are improved while compressive strength is decreased when low-content PP fibers (up to 0.91 kg·m⁻³) are substituted for cementitious materials in concrete, as observed by Ming-xiang [12]. According to Ding’s research [13], a composite made from PP fiber has the added benefit of being light weight and corrosion-proof. Steel fibers added to concrete have been shown to boost tensile strength, decrease porosity, lessen cracking, and enhance ductility, according to the research by Alam [14]. Many studies [15,16] have shown that incorporating metal fibers into concrete has a beneficial impact on fire resistance, energy absorption, and cracking. Nylon fiber additions of up to 1% improved both flexural and compressive strength by 7 and 12%, respectively, over the control specimen [17]. The drying shrinkage and tensile strength of concrete were both increased with the addition of 211% PP fibers, as stated by Majid [2]. The manufacturing of synthetic fibers, on the other hand, is detrimental to the ecosystem and contributes to the acceleration of global warming. These fibers cannot be broken down by natural processes and come at a high cost.

Despite the abundance of natural fibers, luffa sponge fibers as cementitious material reinforcement are gaining popularity. The distinctive matrix structure of the luffa sponge aids to slow down the spread of cracks more than that observed with other types of cellulose fibers. The plant’s fibrous vascular system might be used as reinforcing fibers in cementitious composites [18]. It is made up of countless 3D continuous fibers that seem like a natural mat. The finding demonstrates that this 3D matrix structure might lessen the likelihood of fracture propagation and increase toughness in composites [19]. While other fibers have received considerable attention for their use as reinforcement in cement-based applications, luffa sponge has received less acclaim. Due to a lack of information and study, its usage in concrete has been restricted. This study helps to analyze the utilization of hemp and luffa sponge in concrete applications, to address this gap.

Hemp (Cannabis sativa) is one plant which had gained a lot of interest due to its many useful qualities, including its high storage of carbon, high mechanical and thermal properties of insulation, and rapidly increasing biomass over a period of 4 months [20,21]. Due to the above characteristics, several studies [20,21,22] have investigated the insulating properties of hemp fibers and hemp hurds covalently bound by either organic or organic-based binders, and several hemp-based products, such as flexible mats and boards, have recently been introduced in the market. Life Cycle Assessment has quantified the environmental benefits of hemp-based composites for thermal insulation over conventional materials like rockwool [23]. Hemp particles, lime, water, and sand are mixed to make “hemp concrete,” which is used for wall infilling, floor and roof insulation, and plaster renders [24]. Hemp concrete is utilized for thermal insulation, not for carrying loads, although its fibers’ tensile strength was explored to generate hemp fiber-reinforced concrete [25] and cementitious matrix composite materials for building retrofitting applications [26].

In recent years, the main focus has shifted altogether toward the reduction of carbon footprint, which is becoming a major problem for the environment. Thus, environmentally friendly, low-carbon building materials have been increasingly researched in scientific communities [27,28,29]. The applications of natural fibers are becoming popular due to their cost-effectiveness, low density, and low strength-to-weight ratio with a reduced negative impact on the environment as well as remarkable mechanical characteristics. The main drawbacks of such concrete are its brittleness, shrinkage problems, low tensile strength, and poor resistance in crack propagation, which limit the utilization of natural fibers in various applications. To overcome such drawbacks, optimization of materials could suit the alternative concrete structures. The critical reason behind the numerous studies carried out on natural fibers as an alternative building material for the construction industries is being green or renewable materials, reducing the utilization of natural resources and waste production, and boost the recycling process. Most studies have concluded that natural fibers have a high volume of cellulose fibers which possess excellent mechanical characteristics and play a vital role in reducing carbon footprint [12,14,30,31,32]. It has been shown via several studies that there is a growing need for eco-friendly synthetic fiber alternatives, and this is helping to revive interest in natural fibers. Hassan et al.’s study investigates the influence of hybrid PP fibers on the mechanical and shrinkage behavior of alkali-activated slag (AAS) concrete. Results indicate that hybrid PP fibers reduced shrinkage by up to 15%, while macro-PP fibers achieved a 6% reduction [33]. Hammad et al. examined the flexural performance of reinforced alkali-activated concrete (AAC) beams incorporating 1.5% macrosynthetic PP fibers and 5% steel fibers. The results show enhanced flexural capacity, crack control, and energy absorption, especially with steel fibers [34], and Hammad et al. explored the performance of AAS concrete (AAC) reinforced with 1.5% PP and 5% steel fibers. The results indicated a 10% enhancement in compressive strength and significant improvements in tensile strength [35].

Hemp and luffa fibers are considered better than synthetic fibers in construction due to their sustainability and environmental benefits. Hemp is a renewable resource, and luffa is derived from a natural and biodegradable material. Both materials have unique and porous structures that provide excellent bonding and reinforcement to concrete. Furthermore, hemp and luffa fibers have high tensile strength, making them suitable for use as reinforcement in concrete, while also reducing the need for synthetic materials in construction projects as the synthetic fibers have disadvantages including non-biodegradability, harm to the environment during production, and lack of natural resources. They can also have lower bonding capabilities compared to natural fibers and potentially reduce the overall strength of the concrete mixture compared to natural fibers.

In this study, three different fibers were utilized: hemp, luffa sponge, and a synthetic, PP-based one. The novelty of this study lies in its comparative analysis of natural fibers, specifically hemp and luffa sponge, against synthetic fibers for enhancing concrete’s mechanical properties. It explores the impact of fiber incorporation on both compressive and flexural strengths, as well as workability, using SEM and energy dispersive spectroscopy (EDS) to assess microstructural properties. By highlighting the sustainability benefits of natural fibers, the research contributes to advancing eco-friendly concrete solutions that maintain structural integrity while reducing environmental impact, offering an alternative to conventional synthetic reinforcement in construction.

2 Materials and methods

2.1 Materials

2.1.1 Cement

OPC cement is used in this study. The grade of cement is P400; it is a type of cement produced by Cementos Polpaico, a Chilean cement manufacturer. It is classified as a type II/A–V cement, which means it is suitable for use in moderate sulfate exposure environments and high early-strength concrete. P400 is known for its high early strength and rapid hardening properties. The tests of cement were done per Chilean Code NCh148, NCh149, and Nch164. The results of EDS analysis provide information on the elemental composition of the cement. Typically, EDS results of cement will show the presence of calcium, silicon, aluminum, oxides, and iron as the main elements in the cement. These elements are the main components of cement and are responsible for the cement’s hardening and binding properties. Figures 1 and 2 show the SEM morphologies and EDS analysis of cement.

Figure 1

SEM images of grade P400 cement: (a) 5 μm scale, (b) 10 μm scale, and (c) 50 μm scale.

Figure 2

EDS spectrum of grade P400 cement.

The fiber samples used in the study were captured using an 8x zoom Cannon camera, and the images are shown in Figure 3. This visual representation provides a detailed look at the fibers and their morphological characteristics.

Figure 3

Images of hemp, luffa sponge, and synthetic fibers.

2.1.2 Aggregate

The aggregate was obtained from local vendors of Concepción. Sieving, simple shear, and pycnometry tests were carried out to characterize the soil aggregate. The particle size distribution (PSD) was determined based on ASTM C-136 [36]. Figure 4 shows the PSD results. The d ₁₀₀ is 9.50 mm, the d ₆₀ is 1.12 mm, the d ₃₀ is 0.50 mm, and the d ₁₀ is 0.29 mm. The aggregate properties like density, friction angle, coefficient of uniformity, and coefficient of curvature are provided in Table 1. These values indicate that the aggregate material has a relatively high density and strong interlocking properties, as well as a relatively low residual friction angle. The uniformity and curvature coefficients also indicate that the material is well-graded and has a good shape.

Figure 4

PSD of aggregate.

Table 1

Aggregate properties

Parameter	Value	Unit
Density	2,760	kg·m−3
Peak friction angle	44.66	°
Residual friction angle	28.87	°
Cohesion	5.15	kPa
Coefficient of uniformity, Cu	3.875	Dimensionless
Coefficient of curvature, Cc	0.764	Dimensionless

The dry simple shear test was performed to evaluate the shear strength properties of aggregate particles that are smaller than 4.75 mm in size. . The test measures the shear strength of the aggregate particles, which can provide information on the material’s suitability. This test gives an idea of how much load the aggregate can resist before it starts to fail when the shear load is applied. Figure 5 shows the result of the dry simple shear test of aggregate.

Figure 5

Dry simple shear test of aggregate below 4.75 mm size.

2.1.3 Preparation of concrete specimens

The present study shows three different proportions of synthetic and natural fibers with a constant proportion of water and cement to identify the parameter that influences the strength of the concrete. The proportion used for preparing the samples is 1:1.5:3 with a water/cement ratio of 0.45. For each sample, three replicates were made. Cement, sand, and synthetic or natural fibers were dry-mixed. Then, water with additives was added to the dry mix, respectively. Once the mixing process was finished, the concrete was poured into 105 mm × 105 mm × 105 mm for compression tests and 415 mm × 105 mm × 105 mm for the flexure test, and samples were prepared in accordance with BS-EN-14889-2 [37]. The cementitious synthetic and natural fiber concrete was agitated for 30 s to remove air bubbles. Subsequently, the samples were covered with acetate sheets and placed under ambient conditions of 23 ± 2°C for 24 h in the laboratory before demolding. The specimens were cured in controlled atmosphere and humidity for 7 and 28 days, respectively, for the mechanical testing. Figure 6 shows the casting of specimens.

Figure 6

SEM images of hemp fiber concrete.

2.2 Microstructure properties

The microstructural characteristics of a natural fiber required for implementation in the construction sector for the development of sustainable concrete include fracture type, poly-porous structures, crystallinity index, and fiber surface morphology, which are discussed and summarized in the following sections. Normally, microstructural analysis helps to understand the surface morphology, surface roughness, polyporous structures, presence of voids, and fiber/cement interaction matrix of natural fibers during the mechanical tests.

2.2.1 SEM

Figure 6 reveals the outer surface of the natural fiber (lignocellulosic) consisting of a waxy and fatty layer or flake-like structures as well as salt-like solids, which is highly capable of ensuring tensile force acting on the concrete. However, a natural fiber incorporated into the fiber/cement interaction matrix has good adhesion at the interfacial transition zone, as shown in Figure 7. The microstructure of concrete plays a crucial role in determining its mechanical properties and durability. In this study, we have compared the microstructure of hemp, luffa sponge, and synthetic fiber-reinforced concrete using SEM analysis. The SEM images of the hemp concrete showed a well-distributed and homogeneous distribution of fibers throughout the matrix. The fibers were found to be embedded in the cement paste, indicating good bonding between the fibers and the matrix. They were also observed to be in a straight and aligned position, which is ideal for reinforcing concrete [38]. The microstructure of luffa sponge concrete showed a similar distribution of fibers throughout the matrix as the hemp concrete. However, the luffa fibers were found to be slightly thicker in diameter and had a more irregular shape. This could be due to the natural properties of luffa sponge. The luffa fibers were also observed to be in a straight and aligned position [38]. The synthetic fiber concrete showed a different distribution of fibers throughout the matrix. The fibers were found to be clumped together in some areas, indicating poor distribution and poor bonding between the fibers and the matrix. The fibers were also observed to be in a curved and twisted position. In terms of mechanical properties, hemp and luffa sponge concrete showed higher compressive and flexural strengths compared to synthetic fiber concrete [30]. This can be attributed to the better distribution and alignment of fibers in the hemp and luffa sponge concrete, which leads to better reinforcement and improved mechanical properties. The microstructure analysis of hemp, luffa sponge, and synthetic fiber reinforced concrete showed that natural fibers have a homogenous and well-distributed fiber matrix compared to synthetic fibers, which leads to improved mechanical properties of the concrete [39]. Adding fiber enhanced cohesion resistance between concrete and fiber, making the samples harder. The use of natural fibers, such as hemp and luffa sponge, in concrete, can lead to more sustainable and durable construction materials.

Figure 7

SEM images of luffa sponge fibers.

2.2.2 EDS

EDS is a powerful analytical tool that is used to identify the chemical components of a sample and determine their relative percentages. EDS is typically used in conjunction with SEM and is especially useful for analyzing small particles or thin samples. The data presented above are the result of EDS analysis of the cement sample. In Figure 8, the EDS spectrum of hemp shows that it contained 61.87% carbon and 37.55% oxygen. The atomic percentages are 68.54% for carbon and 31.23% for oxygen. These results indicate that the sample is primarily composed of calcium silicates, which are the main components of a cement. The other elements present in small amounts are potassium (0.17%), aluminum (0.16%), chlorine (0.05%), and magnesium (0.04%). The EDS spectrum of luffa sponge shows that the sample contains 59.24% carbon and 39.76% oxygen. The atomic percentages are 66.23% for carbon and 33.37% for oxygen. The sample also contains small amounts of chlorine (0.67%), aluminum (0.21%), and sodium (0.12%). These results are consistent with the first table and further confirm that the sample is primarily composed of calcium silicates. Overall, these EDS results provide important information about the chemical composition of the cement sample. The high percentages of carbon and oxygen indicate that the sample is primarily composed of calcium silicates, which is consistent with the expected composition of cement. The presence of small amounts of other elements, such as potassium, aluminum, chlorine, and magnesium, suggests that the sample may also contain minor amounts of other minerals.

Figure 8

EDS spectra of hemp and luffa sponge.

3 Results and analysis

3.2 Compressive strength

Figure 9 reveals that the natural fibers have a similar pattern and effect on the strength of concrete. Luffa sponge fibers have superior strength of concrete, which is almost comparable to that of synthetic fibers. The compressive strength of concrete is one of the most important mechanical properties of the material. It is a measure of a concrete’s ability to withstand loads applied to it and is an indicator of the material’s durability and overall performance. The results of compressive strength tests were compared to those of control concrete specimens that were prepared without fibers. In this study, based on the results, it is evident that luffa sponge has the highest compressive strength of 28.15 MPa at 1.2% fiber content on the 28th day when compared to hemp and synthetic fibers. Hemp has a compressive strength of 22.12 MPa and synthetic fibers have a compressive strength of 26.13 MPa on the 28th day. Luffa sponge shows the greatest improvement of 32.10% in compressive strength when compared to the control mix, while hemp shows 21.91% and synthetic fiber shows 22.62% compressive strength, as shown in Figure 10. All three fibers show a significant improvement in compressive strength when compared to the control mix, but luffa sponge stands out as having the highest compressive strength at 28 days among all three fibers, while hemp and synthetic fibers are relatively close in terms of compressive strength. The improved compressive strength of luffa sponge concrete can be attributed to the presence of luffa sponge fibers in the concrete matrix. These fibers act as reinforcement, providing additional strength and stiffness to the concrete [45]. Additionally, luffa sponge fibers are able to bridge microcracks that may form in the concrete, preventing them from propagating and leading to failure [46]. It is also important to note that the compressive strength of luffa sponge concrete was found to be relatively insensitive to variations in fiber content. Specimens with fiber content ranging from 0.4 to 1.2% by volume all exhibited higher compressive strength values than the control mix. Table 3 shows the results of compressive and flexural strength. To create the hardened samples, Quadri and Alabi [47] came up with a novel approach to utilize luffa sponge as concrete reinforcement by using four distinct configurations of longitudinal, scattered, mesh, and laminar patterns. Overall, the highest compressive strength was observed for the scattered fiber pattern, followed by the longitudinal, mesh, and laminar configurations. It was shown that after curing for 7 days, the strength of concrete with luffa fiber dispersed throughout the matrix was almost 50% greater. Using luffa sponge fibers in concrete has proven to be effective in improving its compressive strength. Our research shows that the compressive strength of luffa sponge concrete is significantly better than the control mix. In fact, it has improved by an impressive 32.10%. The reason for this improvement is because the luffa sponge fibers in the concrete make it stronger and stiffer. Moreover, the luffa sponge fibers have the capability to connect small cracks and stop them from spreading, which ultimately enhances the strength and longevity of the concrete. These results are consistent with previous studies that have shown how natural fibers can improve the properties of concrete [42].

Figure 9

Failures of the sample on compression testing.

Figure 10

Percentage improvement in compressive strength at 7 and 28 days.

Table 3

Results of compressive and flexural strength

Fiber type	Mix ID	% Fiber	Compressive strength at 7 days	Compressive strength at 28 days	Flexural strength at 7 days (MPa)	Flexural strength at 28 days (MPa)
Control mix	CS	0	15.32	21.31	2.19	2.71
Hemp	HF 0.4	0.4	16.51	23.01	2.35	2.93
	HF 0.8	0.8	17.68	24.88	2.57	3.34
	HF 1.2	1.2	16.88	22.12	2.7	3.5
Luffa sponge	LF 0.4	0.4	16.23	22.72	2.42	3.18
	LF 0.8	0.8	17.54	26.53	2.58	3.48
	LF 1.2	1.2	18.71	28.15	2.89	3.76
Synthetic	SYF 0.4	0.4	15.84	24.64	2.72	3.02
	SYF 0.8	0.8	16.98	25.69	3.14	3.21
	SYF 1.2	1.2	17.69	26.13	3.51	3.77

3.3 Flexural strength

From the results, it can be observed that all three types of fibers (hemp, luffa sponge, and synthetic) show an increase in flexural strength as the percentage of fiber in the mix increases. At 1.2% fiber content, luffa sponge has the highest flexural strength of 3.76 MPa after 28 days. Synthetic fibers have a flexural strength of 3.77 MPa after 28 days, and hemp has a flexural strength of 3.5 MPa after 28 days. Based on these data, it seems that luffa sponge and synthetic fibers have the highest flexural strength at 1.2% fiber content, followed by hemp. Additionally, all three fibers show a significant improvement in flexural strength when compared to the control mix, with luffa sponge showing the greatest improvement of 38.75%, while synthetic fibers and hemp showed 39.11 and 29.15% flexural strength, respectively. Overall, luffa sponge and synthetic fibers appear to have the highest flexural strength at 28 days, while hemp is relatively close in terms of flexural strength. Previous study shows that the inclusion of hemp and luffa sponge fibers can improve the flexural strength of concrete [48]. This is because the fibers help to distribute the load more evenly throughout the concrete and also increase its overall toughness. The addition of hemp, luffa sponge, and synthetic fibers also increases the ductility of the concrete, making it more resistant to cracking [49]. In general, the flexural strength of luffa sponge fiber concrete is higher than that of traditional concrete, making it a suitable choice for applications that require high-strength and flexible concrete. The testing of flexural strength and failure of natural and synthetic fiber concrete is shown in Figure 11.

Figure 11

Testing for flexural strength.

4 Conclusions

The article discusses the outcomes of natural and synthetic fibers to produce an improvement in concrete properties. The experimental results indicate that concrete made using natural and synthetic fibers has acceptable mechanical and microstructural properties. The following conclusions were obtained from the experimental investigations.

1. The results demonstrate that luffa sponge fiber-reinforced concrete exhibited the highest compressive strength at 28.15 MPa with 1.2% fiber content, showing a 32.10% increase compared to the control mix. This was significantly higher than that of hemp (22.12 MPa) and synthetic fibers (26.13 MPa), highlighting luffa’s superior performance.

2. Luffa sponge and synthetic fibers achieved the highest flexural strength at 1.2% content, reaching 3.76 and 3.77 MPa, respectively, after 28 days. Hemp fibers, with a flexural strength of 3.5 MPa, also demonstrated considerable improvement, showing a 29.15% increase compared to the control mix.

3. Incorporating hemp fibers reduced the flow diameter by up to 55% due to high water absorption, necessitating adjustments in water content or superplasticizers for improved workability. Luffa fibers also impacted workability, but their effect was less severe than hemp, demonstrating a manageable trade-off between workability and strength.

4. SEM analysis revealed that hemp and luffa sponge fibers maintained a straight, aligned, and uniform arrangement within the concrete matrix as compared to synthetic fibers which provided clumped and poor bonding interface. The uniform distribution plays an important role in improving the structural web and mechanical properties.

5. When concrete samples were reinforced with hemp and luffa sponge fibers, significant increments in both compressive and flexural strengths were found compared with the control mix. With a fiber content of 1.2% by weight, the luffa sponge fibers exhibited the highest value of 28.15 MPa for the compressive strength and also recorded good improvements in flexural strength, thus proving its utility as a concrete reinforcing fiber.

6. Use of natural fibers offers two advantages, improved mechanical properties and renewable natural source, compared to synthetic ones. Through the use of these fibers, viability of green constructions can be achieved within the construction industry without compromising the strength of concrete structures.

These encouraging findings suggest that natural fibers like hemp and luffa sponge can provide comparable or better efficiency in distinct structural uses, as underlined by the engineering design and material analysis of load-bearing and secondary structures. However, the work presented herein establishes a strong foundation for future investigation and innovational prospects, including further engineering optimization, extensive field tests in various environments, and stability experiments under real operating conditions, to evaluate their performance and durability stably and comprehensively.