Macro Polypropylene Research Articles

Experimental Study of the Bearing Capacity of Hybrid Fiber-Reinforced Concrete Pipes

This paper presents the results of an experimental study on hybrid fiber-reinforced concrete pipes (HFRCP). The mechanical behavior of HFRCP, including load capacity, failure mode, and energy dissipation capacity, was evaluated through diametral compression tests. The results were compared with those obtained for reinforced concrete pipes (RCP) using traditional steel cage reinforcement and steel fiber-reinforced concrete pipes (SFRCP). A total of 26 pipes with a 600 mm internal diameter were tested, including 4 RCP, 14 HFRCP, and 8 SFRCP pipes. For the hybrid fiber reinforcement, macro steel fibers (SF) and macro polypropylene fibers (PPF) were used, combined at two different doses: 20-0.5 kg/m3 and 20-1.0 kg/m3 of SF and PPF, respectively. The results indicated that HFRCP achieved a load capacity equivalent to RCP and greater than SFRCP for the fiber dosages utilized. Additionally, HFRCP exhibited a ductile failure mode without concrete detachment or diametral crushing.

Performance evaluation of indented macro synthetic polypropylene fibers in high strength self-compacting concrete (SCC)

Concrete is used worldwide as a construction material in many projects. It exhibits a brittle nature, and fibers' addition to it improves its mechanical properties. Polypropylene (PP) fibers stand out as widely employed fibers in concrete. However, conventional micro-PP fibers pose challenges due to their smooth texture, affecting bonding within concrete and their propensity to clump during mixing due to their thin and soft nature. Addressing these concerns, a novel type of PP fiber is proposed by gluing thin fibers jointly and incorporating surface indentations to enhance mechanical anchorage. This study investigates the incorporation of macro-PP fibers into high-strength concrete, examining its fresh and mechanical properties. Three different concrete strengths 40 MPa, 45 MPa, and 50 MPa, were studied with fiber content of 0–1.5% v/f. ASTM specifications were utilized to test the fresh and mechanical properties, while the RILEM specifications were adopted to test the bond of bar reinforcements in concrete. Test results indicate a decrease in workability, increased air content, and no substantial shift in fresh concrete density. Hardened concrete tests, adding macro-PP fibers, show a significant increase in splitting tensile strength, bond strength, and flexural strength with a maximum increase of 34.5%, 35%, and 100%, respectively. Concrete exhibits strain-hardening behavior with 1% and 1.5% fiber content, and the flexural toughness increases remarkably from 2.2 to 47.1. Thus, macro PP fibers can effectively improve concrete's mechanical properties and resistance against crack initiation and spread.

Analysis of synergistic effect of bending energy absorption capacity of fiber reinforced concrete based on fiber distribution characteristic

Analysis of synergistic effect of bending energy absorption capacity of fiber reinforced concrete based on fiber distribution characteristic

Yield-line-based design of fibre-reinforced concrete: assessment of suitability of material models

The aim of this research was to assess the adequacy of material models based on flexural toughness (such as equivalent and residual flexural strength) and the deflection limits at which these parameters are estimated for the design of fibre-reinforced concrete (FRC) for various applications such as slabs-on-grade and pavements. The experimental work was conducted using FRC mixes with hooked-end steel fibres (SF) or macro polypropylene fibres (PF) and hybrid combinations of SF and PF. Toughness testing was carried out on unnotched and notched prisms and square slabs, prepared with a typical grade of concrete used for FRC pavement applications. To validate the material models, comparisons were made between the theoretical moment/load calculated based on material flexural toughness parameters and the actual moment obtained from slabs using the yield line formed during testing. It was found that, overall, both equivalent flexural strength (from unnotched prism tests) and residual flexural strength (from notched prism tests) are suitable for designing FRC slabs. However, the equivalent strength showed better correlation to the slab response. Hybrid PF–SF mixes with a higher volume fraction of 0.6% showed a marginal increase in flexural performance compared with mixes with a lower volume fraction but no or minimal synergy due to hybridisation.

QUALITY IMPROVEMENT EFFECTIVENESS OF ROAD SLABS PRODUCED USING MICROSILICA AND FIBER

Here we present the results of testing the concrete physical and mechanical properties for road slabs reinforced with bulk fiber, including polypropylene macro- and microfibers. We have analyzed the effect of the use of macrofibers and microfibers in the concrete composition. There was established the impact of low-modulus synthetic fibers on the characteristics of strength, density, water resistance and frost resistance of concrete for road pavement. It was established that polypropylene macrofibers impact on the physical and technical characteristics of concrete, increase compressive and bending strength, and polypropylene microfibers improve the structure of the cement component of concrete, optimize the pore space, increase the frost resistance and water resistance of concrete. It has been experimentally proved that owing to the combined use of various sized fiber fibers, it is possible to produce concrete that has good characteristics in strength, density and frost resistance. It was established that with the combined concrete fiber reinforcement with microsilica addition, we get the possibility of increasing bending strength up to 35%, frost resistance up to F375 and water resistance up to W14. The research results make it possible to recommend multi-dimensional polypropylene fibers for volumetric reinforcement and microsilica to create additional crystallization centers and reduce the pore space in the concrete body at road slabs manufacture.

Utilizing bio-based and industrial waste aggregates to improve mechanical properties and thermal insulation in lightweight foamed macro polypropylene fibre-reinforced concrete

Utilizing bio-based and industrial waste aggregates to improve mechanical properties and thermal insulation in lightweight foamed macro polypropylene fibre-reinforced concrete

Research on Tensile Softening Constitutive Relation of Macro Polypropylene Fiber Reinforced Concrete

Research on Tensile Softening Constitutive Relation of Macro Polypropylene Fiber Reinforced Concrete

Damage constitutive model of polypropylene-fibre-reinforced recycled aggregate concrete

Adding polypropylene fibre (PPF) to recycled aggregate concrete (RAC) not only improves performance but also has economic benefits. The effects of single-blend and double-blend micro- and macro-PPFs in RAC specimens were studied. Micro- and macro-PPFs were used to design and produce 30 groups of PPF-reinforced RAC specimens with 0%, 25% and 50% coarse aggregate (CA) substitution rates. Controlling the fibre mixing proportions, the stress–strain curve, elastic modulus, peak strength, peak strain and acoustic emission amplitude–frequency extremum (AFE) of each group of specimens were obtained. The elastic modulus and peak stress of specimens without PPFs decreases gradually with an increase of the CA substitution rate. However, there was a certain increase in elastic modulus and peak stress when PPFs were added. A damage constitutive model for PPF-reinforced RAC was established. By fitting this model, it was found that although the elastic modulus and peak stress of the RAC specimens increased by a certain extent, the fitting parameters of RAC were greater than those of ordinary concrete and the RAC post-peak strength was lower. The evolution law of acoustic emission AFE of PPF-reinforced RAC was studied. It was found that the cumulative AFE of RAC with PPF was larger, indicating that the PPFs limited crack propagation and increased the fracture energy.

Hybrid fibre reinforced recycled aggregate concrete: dynamic mechanical properties and durability

Hybrid fibre reinforced recycled aggregate concrete: dynamic mechanical properties and durability

Fin Sandy Concrete Reinforced with Macro Polypropylene Fiber for Rural And Desert Housing

Fin Sandy Concrete Reinforced with Macro Polypropylene Fiber for Rural And Desert Housing

Comparative performance analysis of ground slabs and beams reinforced with macro polypropylene fibre, steel fibre, and steel mesh

Comparative performance analysis of ground slabs and beams reinforced with macro polypropylene fibre, steel fibre, and steel mesh

Mechanical and Durability Performance of Macro Polypropylene Fibrous Concrete

Mechanical and Durability Performance of Macro Polypropylene Fibrous Concrete

Influence of micro basalt and recycled macro polypropylene hybrid fibre on physical and mechanical properties of recycled aggregate concrete

Influence of micro basalt and recycled macro polypropylene hybrid fibre on physical and mechanical properties of recycled aggregate concrete

Size-dependent long-term weathering converting floating polypropylene macro- and microplastics into nanoplastics in coastal seawater environments

In this study, we systematically developed the long-term photoaging behavior of different-sized polypropylene (PP) floating plastic wastes in a coastal seawater environment. After 68 d of laboratory accelerated UV irradiation, the PP plastic particle size decreased by 99.3±0.15%, and nanoplastics (average size: 435±250nm) were produced with a maximum yield of 57.9%, evidencing that natural sunlight irradiation-induced long-term photoaging ultimately converts floating plastic waste in marine environments into micro- and nanoplastics. Subsequently, when comparing the photoaging rate of different sized PP plastics in coastal seawater, we discovered that large sized PP plastics (1000-2000 and 5000-7000μm) showed a lower photoaging rate than that of small sized PP plastic debris (0-150 and 300-500μm), with the decrease rate of plastic crystallinity as follow: 0-150μm (2.01 d-1) > 300-500μm (1.25 d-1) > 1000-2000μm (0.780 d-1) and 5000-7000μm (0.900 d-1). This result can be attributed to the small size PP plastics producing more reactive oxygen species (ROS) species, with the formation capacity of hydroxyl radical •OH as follows: 0-150μm (6.46×10-15M) > 300-500μm (4.87×10-15M) > 500-1000 (3.61×10-15M) and 5000-7000μm (3.73×10-15M). The findings obtained in this study offer a new perspective on the formation and ecological risks of PP nanoplastics in current coastal seawater environments.

Mechanical behaviour of wollastonite-based cement composites incorporating fibres and recycled rubber aggregates

Calcium phosphate cement (CPC) is a wollastonite-based inorganic cement that hardens at room temperature to a brittle cementitious material with low fracture behaviour. Recycled rubber aggregates from end-of-life tyres were incorporated up to 17.5 wt% into the CPC matrix to produce high-strength composites with improved strain capacities for structural repair purposes. Furthermore, the effects of 0.75% and 1.5% volume fibre content (Vf) of macro polypropylene, amorphous metallic and recycled carbon fibres on the flexural behaviour of CPC were studied. The synergy between the rubber aggregates and the selected corrosion-resistant fibres in improving the fracture properties of the plain CPC was investigated. The changes in other mechanical properties of CPC such as modulus of rupture, compressive and splitting tensile strength due to the inert inclusions (i.e. rubber aggregates and/or fibres) were determined. It was found that increasing the quantity of inert inclusions in the cement matrix improved the fracture energy of the plain CPC. Incorporating 1.5% Vf of macro polypropylene, amorphous metallic, and recycled carbon fibres into the CPC matrix produced cementitious composites with fracture energies that were 11.8 times, 63.4 times, and 75.8 times that of plain cement, respectively. For the rubberised fibre-reinforced CPC composites, a positive synergistic relationship was observed between rubber aggregates and macro polypropylene fibres while a negative synergistic relationship was found between rubber aggregates and the other fibres (amorphous metallic and recycled carbon fibres). The rubber aggregates decreased the flexural, compressive and splitting tensile strengths of the plain CPC, while the fibre inclusions improved these properties.

The effects of steel, polypropylene, and high-performance macro polypropylene fibers on mechanical properties and durability of high-strength concrete

Present study aimed to compare the properties of high-strength and ordinary concrete containing polypropylene fibers (PPFs), high-performance synthetic macro polypropylene (HPP) fibers, and steel fibers (SF) under standard and sulfate curing conditions. The high-strength concrete with water-to-cement ratios of 0.38, 0.33, and 0.28 were tested. The addition of PPF and SF reduced the workability of these mixtures containing supplementary cementitious material. The highest compressive strength belongs to the mixture containing 1% of SF and 0.2% of PPF. The highest tensile strength belongs to the mixture containing 0.5% of HPP fibers with 1% of SF and 0.2% of PPF. The highest flexural strength of the mixture containing 0.5% of HPP fibers with 1% of SF. Fiber- reinforced concretes have less 30-minute water absorption than non-fiber samples. The minimum absorption belongs to the sample containing 0.5% of PPF with 20% of silica fume in the amount of 0.53%.

Improved simplified constitutive tensile model for fiber‐reinforced concrete

AbstractDue to the low strain capacity and the weak crack resistance of concrete, fibers are commonly added to concrete to increase its tensile resistance. The most recent standardized constitutive tensile model is given in the fib Model code 2010, which is based on a simplified stress profile at serviceability limit state (SLS) and ultimate limit state (ULS). However, in current research, an improved stress profile at ULS is proposed. Consequently, three new constitutive tensile models, which are valued for a specific FRC class, are developed. Those models are constructed with the test data of fiber‐reinforced concrete with natural aggregates (FR‐NAC) and three types of recycled aggregates (FR‐RAC). In addition, macro glass fibers and macro polypropylene fibers are used. The test data indicate that the lower concrete Young's modulus of FR‐RAC, as well as the crack growth resistance due to plastic work of the recycled concrete mixtures, result in an increased residual tensile strength at SLS and ULS. The residual tensile strength at 2.5 mm CMOD () of the normal recycled aggregate concrete (nRAC) mixture with 0.75 V% glass fibers is 0.95 MPa, while the FR‐NAC mixture with the same fiber content only indicates a ‐value of 0.43 MPa. Consequently, higher linear postcracking stresses are observed for the FR‐RAC mixtures, especially for the FR‐RAC mixtures with 0.75 V% glass fibers and the lower quality of recycled aggregates.

Influence of Synthetic Fibers on the Flexural Properties of Concrete: Prediction of Toughness as a Function of Volume, Slenderness Ratio and Elastic Modulus of Fibers.

The construction industry requires concrete with adequate post-cracking behavior for applications such as tunnels, bridges, and pavements. For this reason, polypropylene macrofibers are used, which are synthetic fibers that fulfill the function of providing residual strength to concrete. In this study, an experimental plan is carried out to evaluate the bending behavior of concrete reinforced with polypropylene fibers using the four-point bending test according to ASTM C1609. Three fiber dosages (3.6, 7.2 and 10.8 kg/m3) and three fiber lengths (40, 50, and 60 mm) were used. The use of macro polypropylene fibers increased the post-cracking behavior of concrete. In addition, based on the experimentally obtained results and available literature data, a multivariable equation was developed to predict the concrete toughness as a function of the volume, slenderness, and modulus of elasticity of the fibers. A Pearson's correlation coefficient, r of 0.90, showed a strong correlation between the developed equation and the experimental data. From this equation, it was possible to determine the participation of the following parameters in calculating toughness. The participation or weight of the fiber's modulus of elasticity on the concrete's tenacity is 26%, the volume of the fiber is 39%, the slenderness is 19%, and the reinforcement index is 16%.

Pure and mixed-mode (I/III) fracture toughness of preplaced aggregate fibrous concrete and slurry infiltrated fibre concrete and hybrid combination comprising nano carbon tubes

Concrete is the most widely used and inexpensive material in the construction sector. However, due to its weakness in tension, the cracking and brittle fracturing of concrete is considered a major deficiency. Advancements in fibrous concretes have recently been emerged to mitigate this issue. Preplaced Aggregate Fibrous Concrete (PAFC) and Slurry Infiltrated Fibrous Concrete (SIFCON) are unique cement composites made of fibres with surpassing mechanical properties and exceptional toughness values. The production of PAFC and SIFCON involves packing of aggregates and fibres in the mould and filling the gaps between the aggregates with the high flowability injected cement grout. Nevertheless, the mono and hybrid layered effect of PAFC and SIFCON on fracture toughness is still unexplored and needs special attention to bridge this research gap. This research examined the pure (I and III) and mixed (I/III) modes of fracture toughness of PAFC, SIFCON and hybrid two-layered PAFC-SIFCON samples. For this purpose, many notched specimens of circular disc shapes were prepared using single and double-layer concepts. To investigate the effect of fibres, three different fibre types were used; hooked-end steel fibre, macro polypropylene fibre and hybrid shape of crimped-hooked end steel fibre with dosages of 2.4% and 8% by volume to produce PAFC and SIFCON, respectively. Additionally, multi-walled nano-carbon tubes (MWCNT) were added to the composites with a dosage of 0.1% by cement weight. The compressive strength, stress intensity factors, effective stress intensity factors, mixity parameter, failure pattern, range of fracture toughness and scanning electron microscope were examined, discussed, and compared. Results indicated that pure mode III has a greater cracking risk than both mode I and mixed-mode I/III. The mixed-mode fracture toughness of PAFC specimens improved by 33.07 to 67.94%. Similarly, this improvement ranged from 59.77 to 210.70% for SIFCON and from 51.0 to 131.55% for PAFC-SIFCON. In addition, the fracture toughness of SIFCON is considerably higher than the PAFC and hybrid combination. In all three composite types, the hybrid shape steel fibre outperformed the hooked-end steel and polypropylene fibre under all three modes.

Restrained Shrinkage of High-Performance Ready-Mix Concrete Reinforced with Low Volume Fraction of Hybrid Fibers.

Cracking due to restrained shrinkage is a recurring issue with concrete bridge decks, impacting durability and ultimately service life. Several scholars' research has proven that the incorporation of fibers in concrete mitigates restrained shrinkage cracking when utilizing high (0.5-3%) fiber volumes. This often presents a mixing and placement issue when used for ready-mixed concretes, which discourages their use in bridge decks. This study aims to optimize the incorporation of fibers for their benefits while producing concrete that is conducive to ready-mix, jobsite use. A series of tests were performed on a high-performance concrete (HPC) mix which incorporated blended, multiple fiber types (steel crimped, macro polypropylene, and micro polypropylene) while maintaining low total fiber (0.19-0.37%) volume. These "hybrid" fiber mixes were tested for multiple mechanical properties and durability aspects, with a focus on the AASHTO T334 ring test, to evaluate fiber efficiency under restrained conditions. Promising results indicate the use of a low-volume hybrid fiber addition, incorporating a macro and micro polypropylene fiber (0.35% by volume) blend, reduced the cracking area by 16.6% when compared to HPC incorporating a single fiber type, and 39% when compared to nonfibrous HPC control mixture.