Addition Of Polypropylene Fibers Research Articles

Polypropylene Fiber as a Factor of Reduction of the Total Shrinkage Strain of Expanded Clay Concrete

Statement of the problem. The article presents the development features of the total shrinkage strain of expanded clay concrete, expanded clay fiber-reinforced concrete, expanded clay steel-reinforced concrete, and expanded clay fiber-steel-reinforced concrete. According to the analytical review, the shrinkage strain decrease as a result of the fibers adding was noted by the researchers without analyzing the reason for the phenomenon. Therefore the purpose of the study is to establish the reason for the decrease of the shrinkage strain of expanded clay concrete with the addition of polypropylene fibers. Results. It has been confirmed that the polypropylene fiber addition reduces the total shrinkage strain of expanded clay concrete by 29—34 % on the 120th day with the volume content of fibers of 0.36 %. Empirical dependences of deformations compatibility for expanded clay fiber-reinforced concrete and expanded clay fiber-steel-reinforced concrete are set forth. Conclusions. It has been experimentally established that fiber is a significant factor on the first days of the concrete mixture hardening, when the elastic modulus of the fiber is greater than or equal to the elastic modulus of the cement stone. Fibers act as a bond and affect the redistribution of shrinkage stresses within the composite, thus reducing the values of the total shrinkage strain.

Mechanical characteristics and microscopic mechanism of polypropylene fiber modified recycled road solid waste fine aggregate mortar

Recycled fine aggregate (RFA) is a recycled building material obtained by crushing and screening waste concrete, which is the main raw material for producing recycled aggregate mortar (RAM). However, due to the defects of RFA such as many cracks, high porosity and large fragmentation index, RAM has problems such as low compressive strength and poor flexural strength, which limits its large-scale application in mortar engineering. In this paper, a series of experiments were carried out to verify that the addition of polypropylene fiber (PPF) improves the mechanical strength of RAM. Four lengths (3mm, 6mm, 9mm, 12mm) and three dosages (0.3%, 0.6%, 0.9%) of PPF were added, and their effects on the compressive strength and flexural strength of RAM were studied. The test results show that the addition of PPF can improve the compressive strength and flexural strength of RAM and increase the toughness of RAM. The addition of PPF with 0.6% dosage and 12mm length can increase the compressive strength of RAM by 57% and the residual strength by 73%. The addition of PPF with 0.9% dosage and 12mm length can increase the flexural strength of RAM by 58% and the fracture energy by 163%. Scanning electron microscopy (SEM) results show that PPF can improve the microstructure of RAM. The effective bonding between the matrix and PPF is observed, which increases the mechanical strength of RAM. In addition, PPF is pulled out and broken, proving that PPF effectively plays its bridging and stretching role in the matrix. Moreover, a prediction model for the effect of PPF length and dosage on the compressive strength and flexural strength of RAM is proposed, which can provide theoretical basis for practical engineering and reference for related researches. This study proposes a negative carbon method for applying road solid waste to engineering mortar, which can provide theoretical basis for practical engineering and reference for related research.

Experimental and numerical simulation study on the dynamic behavior of basalt-polypropylene fibers reinforced coral aggregate concrete

This study investigates the failure mode, dynamic compressive strength, strain rate effect and critical strain of basalt-polypropylene fiber-reinforced coral concrete (BPRCAC) under impact load using a 75mm diameter split Hopkinson pressure bar (SHPB). The Holmquist-Johnson-Cook (HJC) model is modified to obtain parameters such as strain rate effect and strength based on the test results, utilizing LS-DYNA for numerical simulation analysis. The results indicated that the dynamic compressive strength and critical strain of BPRCAC significantly respond to the strain rate, increasing with the strain rate. A relationship between the dynamic increase factor (DIF) and the strain rate of BPRCAC is developed, showing that the DIF increases linearly with the decimal logarithm of the strain rate. However, the critical strain of BPRCAC increases linearly with the strain rate. The addition of basalt fiber (BF) and polypropylene fiber (PF) improves the strain rate sensitivity of the dynamic compressive strength, with increases of 19.21%, 7.37%, 22.60%, and 11.37% observed for BCAC-0.1, PCAC-0.1, BPCAC-0.1, and BPCAC-0.2, respectively, compared to CAC at a strain rate of 133−143s-1. The combined content of BF and PF has a more significant effect on the strain rate sensitivity of the critical strain, with BPCAC-0.2 exhibiting a critical strain 50.79%−74.42% higher than that of the other groups compared to CAC. The stress-strain curves and failure modes of the specimens simulated by LS-DYNA agree with the experimental results, verifying the applicability of the improved HJC model to BPRCAC.

Effect of Polypropylene Fibers on the Behavior of Dune Sand Concrete Subjected to Elevated Temperatures

In the field of civil engineering, concrete is one of the most used materials. Above a particular temperature, concrete can exhibit thermal instability during fire events. Improving the safety of buildings and structures is an important issue of this study. This paper investigates the effects of adding polypropylene fibers to dune sand concrete at high temperatures. Prismatic specimens (4 x 4 x 16 cm3) are produced, and stored until the concrete is hardened. The samples are then subjected to a heating-cooling cycle, starting from room temperature and increasing by 0.1 °C/min until reaching 600 °C. The length and the rate of polypropylene fibers are examined to determine their impact on compressive strength, porosity, and weight loss at temperatures of 80, 150, 300, 450, and 600 °C. Also, the partial replacement of dune sand (DS) with river sand (RS) is investigated. The results show that, for temperatures below 450 °C, the strengths of dune sand concretes varied from 29 to 39% compared to those obtained with concretes subjected to an ambient temperature (20 °C). However, it should be noted that residual compressive strength values decrease at most temperatures with the addition of polypropylene fibers. Furthermore, sand concrete with 50% DS and 50% RS shows an increase in compressive strength of 43.77% compared to that obtained by 100% DS concrete.

Utilizing construction and demolition waste in concrete as a sustainable cement substitute: A comprehensive study on behavior under short-term dynamic and static loads via laboratory and numerical analysis

This study explores the utilization of recycled concrete powder (RCP) as a sustainable alternative to conventional cement in concrete production, focusing on its impact on mechanical properties and impact resistance. Two series of concrete mixtures were prepared: one without and one with 0.5 % polypropylene fibers by RCP-replacing cement at varying proportions (0 %–50 %). Methodologically, the research involved both laboratory tests and predictive modeling using artificial neural networks (ANN) and fuzzy logic (FL). Laboratory evaluations assessed compressive, flexural, and tensile strengths under static loads, as well as impact resistance through repeated drop weight impact (RDWI) tests. Key findings reveal that RCP-incorporation of 15 % leads to negligible reductions in compressive, flexural, and tensile strengths, while higher replacements significantly decrease performance. The addition of polypropylene fibers notably improved mechanical properties across all RCP replacement levels, enhancing compressive strength by up to 23.65 % and flexural strength by 27.49 % at the upper limits of RCP substitution. Accurate predictions of 28-day compressive strength were achieved via the ANN model with an average prediction error less than 1 %. The study also validates that the Weibull distribution effectively describes the impact resistance of concrete mixtures, confirming the advantages of combining RCP with fiber reinforcement to achieve sustainable and high-performance concrete solutions.

The Impact of Natural Fibers on Thermal Resistance and Spalling in High-performance Concrete

This article presents an experimental approach to evaluate the effectiveness of palm fibers as a natural innovative solution to enhance the thermal resistance of high-performance concrete (HPC) under fire conditions. The utilization of palm fibers aims to promote local materials, since locally sourced materials may be more affordable due to their abundance. Four different high-performance concrete formulations were tested. The first, called HPCSF, which is composed of fibreless silica fumes, served as a reference mix. The second, HPCPSF, included the addition of polypropylene fibers to silica fume. The third, HPCDFSF, integrates date palm fibers with silica fume. Finally, the fourth, HPCPQSSF, combined polypropylene fibers with varying amounts of quarry sand and silica sand, in addition to silica fume. The results of the fire resistance tests show that the incorporation of palm fibers into the concrete mixture improves structural strength, reduces spalling, prevents crack formation under high-temperature conditions, and increases fire resistance in HPC.

Dynamic properties of CO2-cured foam concrete at different loading rates: Effect of the foam admixtures and addition of polypropylene fiber

This paper investigated the dynamic mechanical properties of CO2-cured foam concrete under varying conditions, focusing on the effects of foam admixture and fiber reinforcement. The study tends to enrich the knowledge regarding the performance of CO2-cured foam concrete under different loading rates, especially in relation to density and matrix strength. The foam admixture of the specimens ranges from 26% to 55%, achieving density from 600 kg/m3 to 1,000 kg/m3. The specimens were loaded at strain rates from 80 s-1 to 398 s-1. Experimental results revealed the dynamic elastic modulus, dynamic compressive strength, and Dynamic Increase Factor (DIF) showed a strong correlation with the foam admixture and density. In addition, the incorporation of polypropylene (PP) fibers effectively improved the mechanical behavior of the foam concrete, achieving up to a 17% increase in dynamic compressive strength. This comprehensive analysis highlights the critical role of foam admixture and fiber reinforcement in determining the dynamic properties of CO2-cured foam concrete and provides valuable insights for optimizing the dynamic performance of foam concrete in various construction applications.

Impact response and constitutive model of basalt-polypropylene fiber-reinforced coral aggregate concrete

Basalt-polypropylene fiber-reinforced coral concrete (BPFRCAC) is a popular choice for engineering materials in the reef environment, but the dynamic behavior of BPFRCAC under extreme dynamic loads remains unclear. This study explores the impact response of BPFRCAC at strain rates ranging from 31 to 141 s−1 using split Hopkinson pressure bar (SHPB). It examines the effects of strain rate on the dynamic mechanical properties of BPFRCAC, and establishes quantitative models of the relationship between the strain rate and key mechanical parameters, including dynamic compressive strength, critical strain, dynamic elastic modulus, and toughness index. The results showed that these properties of BPFRCAC are significantly influenced by the strain rate, showing increases that correlate with the strain rate. The addition of basalt fibers (BF) and polypropylene fibers (PF) not only mitigates the failure extent of BPFRCAC but also enhances the strain rate's impact on its dynamic compressive strength and dynamic modulus of elasticity, particularly when both fibers are mixed. The failure modes of BF and PF depend on the strain rate; at lower strain rates, the probability of fiber pull-out is higher than at higher strain rates, where BF and PF are more likely to snap. A viscoelastic dynamic damage constitutive model suitable for BPFRCAC is proposed, which accurately describes the dynamic mechanical behavior of BPFRCAC. These findings provide important design insights into the use of BPFRCAC under impact conditions, and promote its wide application in reef construction projects.

Structural performance of fibre reinforced recycled aggregate concrete road kerb sections under monotonic and cyclic loading

In recent years, there has been a notable emphasis on waste reduction and the adoption of recycled materials within the construction industry to reduce the industry’s overall carbon footprint. This study investigates the structural performances of concrete kerb sections prepared with five different concrete mixes containing recycled concrete aggregate, recycled tyre-derived aggregates and recycled polypropylene fibres. Kerb sections were cast at a road site in a suburb of Adelaide, Australia. After the concrete hardened, sections were cut and brought to the laboratory. A large number of monotonic and cyclic load tests were conducted on the kerb sections. The load-carrying capacity, bending moment capacity, cyclic fatigue capacity, durability properties along with deformation tolerance were evaluated. Kerb sections made with concrete containing recycled aggregate and polypropylene fibre could sustain nearly 2000 cycles of loading. Kerb sections prepared with natural aggregate concrete performed comparatively better. The addition of polypropylene fibre significantly improved the post-cracking behaviour of kerb sections and can delay crack propagation and other distress when subjected to cyclic loadings such as excessive soil movement, e.g., in areas with expansive soils or prone to tree root migration. Long-term observation may be required to confirm the mechanical and durability performance improvement in real field conditions.

EFEKTIVITAS PENAMBAHAN SERAT POLYPROPYLENE TERHADAP KUAT LENTUR BETON GEOPOLIMER dengan SUPERPLASTICIZER

Geopolymer concrete is concrete composed of a mixture of coarse and fine aggregate without Portland cement binder. Fly ash is used as a substitute, because it contains a lot of silica and alumina. Geopolymer concrete has good strength and durability, but concrete also has disadvantages, namely brittleness, workability and often cracking due to tensile loads. Superplasticizer (SP) is used at 2% of fly ash weight to improve workability. The SP used is Sika viscocrete 1003. The addition of polypropylene fiber is one way to overcome brittle properties and the appearance of fine cracks in concrete. In this paper using Sika fiberforce 48mm polypropylene fiber which has a tensile strength of 465N/mm2(MPa) at a dose of 0%, 0.5%, 1%, 1.5% and 2%. The alkaline activator used is a mixture of NaOH and Na2SiO3 solutions. The molarity of the NaOH solution used is 8M with a ratio of NaOH/Na2SiO3 2: 3. From the test results, it is known that the influence of polypropylene fiber is effective for increasing the bending strength of geopolymer concrete. The bending strength value of geopolymer concrete with the addition of polypropylene fibers increased by 60.19%. The polypropylene fiber content will be maximum at a percentage of 0.5% of the total volume of the mixture.Keywords: Fiber, Flexural Strength, Fly Ash Geopolymer Concrete, Polypropylene, Superplasticizer

Study on impermeability of reinforced concrete wall with horizontal construction joints

The reinforced concrete (RC) water retaining tank walls with horizontal construction joints are prone to experiencing seepage under high hydrostatic pressure, which can affect the structural integrity and functionality. To evaluate the impermeability of construction joints with different improvement measures, the permeability test of concrete with and without horizontal construction joints was conducted. The test results show that the addition of Polypropylene fibers (PP fiber) and Cementitious Capillary Crystalline Waterproofing materials (CCCW) can improve the self-waterproofing ability of concrete. The impermeability at the construction joint is much lower than that of single-casting concrete. Moreover, applying CCCW to the water-facing surface of the construction joint can significantly enhance its impermeability. Then, two 1:2 scaled RC tank wall specimens were manufactured, with one wall of conventional concrete and the other wall of modified concrete. The impermeability tests of the typical single-casting and double-layer casting parts of the two wall specimens were carried out respectively. The experimental results show the RC tank wall with construction joint is prone to generate initial defects and seepage, making it difficult to achieve the design watertight requirements. The use of modified concrete materials and surface treatment in the relevant part can effectively improve the impermeability performance of the construction joint. Finally, the BP neural network was used to establish a prediction model between the impermeability of concrete and its material parameters and construction technology.

Analysis of the life cycle concrete with the addition of polypropylene fibers

In accordance with the principles of sustainable construction, the results of Life Cycle Assessment (LCA) technique are useful inputs to the decision-making process when designing a building. This article presents such an analysis of a finished building product, which is a modified concrete mix. The calculations took into account the phases of the A1–A4 cycle, i.e. from the extraction of raw materials to the transport of the finished material to the construction site. Test results for concrete mixes and 28-day solid concrete are presented in tabular form. Based on all the test results obtained, it was found that the addition of waste polypropylene fibres has a positive effect on the key properties for the floor concrete. It has been found that proper processing of banding tapes or other polypropylene waste into macro-fibres can be a good example of proper waste management and can contribute to a significant reduction in residual waste. This additive is emission-free and sourced from recycling, making it an excellent alternative to commonly used dispersed reinforcement.

Compressive Properties of Basalt Fibers and Polypropylene Fiber-Reinforced Lightweight Concrete.

With the development of high-rise and large-scale modern structures, traditional concrete has become a design limitation due to its excessive dead weight. High-strength lightweight concrete is being emphasized. Lightweight concrete has low density and the characteristics of a brittle material. This is an important factor affecting the strength and ductility of the lightweight concrete. To improve these shortcomings and proffer solutions, a three-phase composite lightweight concrete was prepared using a combination of tumbling and molding methods. This paper investigates the various influencing factors such as the stacking volume fraction of GFR-EMS, the type of fiber, and the content and length of fiber in the matrix. Studies have shown that the addition of fibers significantly increases the compressive strength of the concrete. The compressive strength of concrete with a 12 mm basalt fiber (BF) (1.5%) admixture is 9.08 MPa, which is 62.43% higher than that of concrete without the fiber admixture. The compressive strength was increased by 27.53 and 21.88% compared to concrete containing 3 mm BF (1.5%) and 0.5% BF (12 mm), respectively. Fibers can fill the pore defects within the matrix. Mutually overlapping fibers easily form a network structure to improve the bond between the cement matrix and the aggregate particles. The compressive strength of lightweight concrete with the addition of BF was 16.71% higher than that with the addition of polypropylene fiber (PPF) with the same length and content of fibers. BF has been shown to be more effective in improving the mechanical properties of concrete. In this work, the compressive mechanism and optimum preparation parameters of a three-phase composite lightweight concrete were analyzed through compression tests. This provides some insights into the development of lightweight concrete.

Study on static and dynamic mechanical properties and microstructure of silica fume-polypropylene fiber modified rubber concrete

Through tests and micro-observations, the static and dynamic mechanical properties and microstructure of rubber concrete samples modified with varying amounts of silica fume and polypropylene fiber content were explored. The results indicate that incorporation of silica fume and polypropylene fiber can effectively enhance the performance of rubber concrete. Moreover, at 10% and 0.1% of silica fume and polypropylene fiber content respectively, rubber concrete’s compressive strength, splitting tensile strength, flexural strength, and dynamic compressive strength reached maxima. Furthermore, microstructure characteristic analysis indicated that inadequate adhesion between rubber particles and the matrix is responsible for compromised bearing capacity in unmodified rubber concrete. However, with the addition of silica fume and polypropylene fiber, the fiber binds the rubber particles closely with the matrix, while the silica fume fills the gaps between the matrix components. This combination results in rubber concrete with a denser internal structure and enhances its bearing capacity significantly.

Cement kiln dust and polypropylene fiber in expansive clay improvement

For civil engineers, expansive soils pose a great deal of difficulty because of their sensitivity to volume changes with different moisture levels. These difficulties are compounded by the widespread occurrence of swelling clay, which can seriously harm infrastructure, especially in arid or semi-arid areas. The geotechnical qualities of these soils have been improved through the use of various additives and techniques, resolving this problem and making the soils suitable for building. Numerous stabilization techniques, nevertheless, may have negative environmental effects. Therefore, it is imperative to investigate the use of local waste or by-products to stabilize soil in order to preserve the environment and lower stabilization costs, especially in road construction projects.To address these issues, an experiment was conducted to determine how locally obtained cement kiln dust (CKD), both alone and combined with polypropylene fibers, affected the properties of plastic clay soil, also referred to as expansive clay from Cheffia.The main objective of this study is to assess how well different CKD percentages (from 5% to 25%) stabilize soil while improving its mechanical and physical properties. The study also aims to explain how the addition of polypropylene fiber affects the unconfined compressive strength and compaction behavior of the soil in the optimal CKD-soil mixture. The results of the analysis show that the addition of cement kiln dust (CKD) significantly improved the studied soil's workability, compaction, and strength. Additionally, adding polypropylene fibers strengthens the clay's resistance to compression, which presents encouraging opportunities for reducing the difficulties brought on by expansive soils in civil engineering applications.

Effect of fiber type on performance of fiber reinforced concrete applied for hydraulic construction

This study aims at evaluating effect of fiber types on comprehensive property of a practical fiber reinforced concrete (FRC) applied for hydraulic construction. Three fiber types including polypropylene, glass, and steel fiber were used to replace concrete volume at 0.3 vol.%. Experimental results illustrated that when compared with the reference concrete, the fiber reinforced concretes with steel or glass fiber had comparable or slight changes on the fresh properties. But, addition of polypropylene fiber induced the fresh FRC with decreased slump flow and significantly increased air entrained volume. Although using various types of fibers led to unbeneficial effect on the compressive strengths of the FRCs, presence of fiber induced the FRCs with significant enhancements on the flexural strength, drying shrinkage, and water absorption and slightly increased UPV at 28 days. In this study, steel fiber was considered as the best choice for improving the mechanical properties of the hardened concrete while, as the volume stability and durability performance of the concrete were primarily considered, polypropylene seemed to be a preferable selection. According to standardized requirements, all concrete proportions were in classification of M40(28)-M45(28), being assigned to concretes suitably applied for widespread on-site hydraulic constructions.

Study on the rheology, mechanical properties and microstructure of polypropylene fibers in different binder systems

To explore the effects of polypropylene fiber (PPF) on the properties of different binder materials, the effects of PPF on the rheology, shrinkage, mechanical properties and microstructure of alkali-activated mortar (AAM) and ordinary Portland cement mortar (PCM) were studied. The results showed that the addition of PPF reduced the fluidity of the mortar, and the lower the initial yield stress and plastic viscosity of the paste were, the more obvious the increase. PPF reduced the drying shrinkage of both the AAMs and PCMs by 7.63–12.85 %. The inclusion of PPF to the mortar had a limited effect on enhancing the mortar compressive and flexural strength, but it notably improved the mortar toughness. At a fiber content of 0.5 %, the samples from the cement and slag-steel slag systems exhibited a more compact of the interfacial transition zone (ITZ) between the fiber and paste. Conversely, the slag-steel slag-fly ash and slag-fly ash systems showed poorer compact of the ITZ, which was attributed to increased unreacted precursors and shrinkage cracks. This phenomenon primarily accounted for the superior residual stresses observed in the cement and slag-steel slag systems. This study provides an avenue for analysis the effect of the same fiber on different binder systems.

Influence of basalt fiber and polypropylene fiber on the mechanical and durability properties of cement-based composite materials

To boost the mechanical strength and endurance quality of cement-based composites, basalt fiber and polypropylene fiber have been included cement-based composites in a single-doped and mixed manner, respectively. Through the tests of flexural strength, compressive strength, drying shrinkage and freeze-thaw cycle, the mechanics properties and endurance quality of cement-based composites with different fiber contents were analyzed. Scanning electron microscopy and a mercury intrusion test were used to compare and study the microstructure and pore structure properties of cement-based composites. The results indicate that the improvement of compressive strength for cement-based composites by single adding basalt, polypropylene fiber and mixed addition of two kinds of fibers is not obvious, but improving the flexural strength of composites by single addition of fiber and 1:1 mixing in a certain dosage range is effective. Among them, 1:1 mixed fiber shows a better advantage superposition effect, which shows better enhancement and toughening effect on composites. Fiber single doping and 1:1 mixing can reduce the Drying shrinkage and mass loss rate of the composites within a certain range, and enhance the composites' ability to resist Drying shrinkage and freezing. Based on the comprehensive mechanical properties and durability tests, it is recommended that the content range of the two fibers mixed with 1:1 is 0.4 %–0.6 %. Both basalt fiber and polypropylene fiber can be closely combined with the cement matrix, and randomly distributed in the composite material to form a network structure, which has the function of series skeleton, effectively inhibits the generation and expansion of cracks in the composite material, and improves the microstructure of the composite material. Both basalt fiber and polypropylene fiber can reduce the harmful pores and multi-harmful pores of the composite material, and transform them into harmless pores and less harmful pores, refine the internal pore structure of the composite material, and improve its compactness. The two kinds of fibers are randomly distributed to form a network structure, which refines the large pore size inside the composite material and blocks the connected pores, and the basalt fiber is refined to fill the interface between the polypropylene fiber and the cement matrix, so that the composite material is more compact, thereby significantly improving the mechanical properties and durability of the composite material.

The Mechanical and Self-Sensing Properties of Carbon Fiber- and Polypropylene Fiber-Reinforced Engineered Cementitious Composites Utilizing Environmentally Friendly Glass Aggregate

In order to facilitate waste glass recycling and enable the monitoring of concrete structures, this study prepares a new type of self-sensing engineered cementitious composite (ECC) via the use of glass sand instead of silica sand. The health monitoring of a concrete structure is achieved through the addition of polypropylene (PP) fibers to enhance the flexural toughness of concrete, and adding carbon fibers (CFs) to make the concrete self aware, enabling it to sense the load changes and structural damage. The fiber dosage of ECC is optimized to analyze the effects of different fiber types and dosages on the mechanical and self-sensing properties of concrete. The results show that the hybrid fibers produce a good synergistic effect on mechanical properties, and the presence of excess fibers causes the mechanical properties of concrete to deteriorate. The critical fiber volume fraction required for the strain hardening of PP ranges from 0.75% vol to 1% vol. At different PP dosages, the CF dosage shows a positive correlation with the initial crack strength. By analyzing the effect of varied curing times and CF doping on the initial resistivity, it is found that the threshold value of CF conductivity is 0.7% vol. The role of CFs in the flexural sensitivity and pressure sensitivity tests is explained from the perspective of fiber distribution, and the fiber distribution theory is verified with scanning electron microscopy (SEM). The optimal level of CF doping for flexural sensitivity and pressure sensitivity is determined to be 1.1% vol and 0.7% vol via the use of self-sensing performance tests, respectively. An increase in PP fiber doping leads to a decrease in the initial resistivity and self-sensing properties of the material. The results of this research provide guidance regarding how to determine the optimal fiber dosage flexibly for different engineering works.

Utilization of waste face masks to reinforce magnesite mine tailings for sustainable subgrade construction

The disposal of magnesite mine tailings (MMT), a by-product of magnesite mining, raises significant environmental concerns due to its adverse effects on soil, water and air quality. Likewise, the improper disposal of used face masks exacerbates environmental burdens. The innovative use of polypropylene fibres (PPF) derived from disposable face masks to reinforce. This study explores the compaction and strength characteristics of PPF-MMT composites with varying fibre content to develop a sustainable composite for subgrade construction. The findings indicate that the addition of PPF increases optimal moisture content and decreases maximum dry density. Shear strength analysis reveals a linear failure envelope for both MMT and PPF-MMT, with initial angle of internal friction improvement at lower PPF content (0.25% and 0.5%) but a decline at higher contents (0.75% and 1%). Importantly, PPF-MMT consistently exhibits a unique strain-hardening behaviour across all stress levels, distinguishing it from MMT, which only transitions to strain-hardening at higher stresses. Under vertical load, MMT shows contraction, while the PPF-MMT composite initially contracts but later dilates due to increased fibre-MMT interaction during horizontal displacement. Furthermore, California bearing ratio (CBR) tests demonstrate increased dry CBR with PPF, reaching a peak of 33.85% at 0.5% fibre content. The soaked CBR tests affirm the remarkable durability of PPF-MMT, maintaining significantly higher values than MMT even after 60 days of soaking. The study concludes that 0.5% fibre content as optimum dosage.