Effect Of Polypropylene Fibers Research Articles

Experimental Study on Impact Behavior of Concrete Panel with and without Polypropylene Macrofibers

Macrofibers have often been used to increase the tensile strength, durability, crack resistance, spalling, impact resistance, and toughness of concrete. However, the impact behavior of fiber-reinforced concrete (FRC) structures is quite different from their static behavior, and the effectiveness of macrofibers in improving impact resistance should be carefully evaluated. In this study, the impact behavior of FRC with polypropylene (PP) macrofibers was studied through a series of drop-weight impact tests. First, the material characteristics of the FRC with PP fibers under static conditions were evaluated. Test specimens were constructed and drop-weight impact tests were performed. The main parameters were the presence or absence of PP fibers and the drop height, which is related to the magnitude of the impact energy. From the results, it can be found that the crack width of the FRC specimen was smaller than the normal concrete specimen for a similar residual deflection after the impact test due to the bridging effect of the macrofibers. However, the effect of PP fibers on the impact resistance was not significant, even though there was a considerable increase in tensile and flexural performance under static conditions, since the hardening effect after the sharp reduction in strength shown in the static test of FRC is not effective in the impact test.

The effect of polypropylene fiber on the curing time of class G oil well cement and its mechanical, petrophysical, and elastic properties

The cement paste is subjected to various loads throughout a well’s life, which may compromise some of its essential characteristics and impair its performance. When the cement paste is first being formed and the cement’s characteristics have not yet fully matured, these loadings take on greater importance. In this study, the early properties of cement used in oil wells that contains polypropylene fiber are assessed. Five different curing times were used to prepare ten cement samples (6, 12, 24, 48, and 72 h). Five samples contained polypropylene fiber, while the remaining five samples were without polypropylene fibers. After the samples were prepared, the examination of several early cement properties took place. Nuclear magnetic resonance (NMR) was used to describe each sample in order to determine how the curing times affected the cement’s porosity. The findings demonstrated that both cement systems’ compressive and tensile strengths increased with curing time, and that adding polypropylene fiber enhanced the cement’s strength. The porosity and permeability of the cement specimens were significantly reduced with the incorporation of polypropylene fibers, as well as with time during the curing process for both cement samples. The reduction of Young’s modulus and the increase in Poisson’s ratio show that the addition of polypropylene fibers also makes the cement more elastic. To express variations in porosity as well as compressive and tensile strengths, logarithmic relationships were constructed. While the Poisson’s ratio, Young’s modulus, density variations, and permeability were precisely modeled by power-law equations.

Effect of polypropylene fibre on cementitious mortar early shrinkage cracking using the eccentric-ring test

The effects of polypropylene fibres on mortar and cement-paste cracking were investigated using different amounts of fibre fractions and eccentric rings under restrained-shrinkage conditions. Eccentric-ring tests were conducted to investigate early-age shrinkage cracks. The characteristics of restricted cementitious materials were described by evaluating the cracking time and using concrete mixtures that are less likely to crack. Different fibre-volume fractions significantly enhanced the width, area, and age of cracking. Increasing the water-cement ratio and sand percentage increased the cracking age. The eccentric-ring test showed a greater susceptibility to cracking in cement-mortar composites. The mechanical strength was assessed, and the impact of polypropylene fibres was investigated.

Effect of polypropylene fiber on workability and strength of fly ash-based geopolymer mortar

Geopolymers do not require Portland cement as a binder; hence, the binder is replaced by a material containing high SiO2 and Al2O3 reacted with an alkaline activator (NaOH and Na2SiO3). In addition, mortar or concrete is highly susceptible to cracking, requiring the addition of polypropylene fiber (PPF). This research belongs to an experimental study examining the addition of PPF with percentages from 0%, 0.25%, 0.5%, 0.75%, and 1% by utilizing coal fly ash (FA) as a precursor. This study also added a superplasticizer (SP) and extra water (EW) to maintain the flowability. The tests were carried out on the workability, strengths, and microstructure of geopolymer mortar. Workability obtained values of 140 - 220 mm. Furthermore, the highest compressive strength of 73.3 MPa and flexural strength of 9.92 MPa were identified in the geopolymer mortar with the addition of 0.5% PPF. In addition, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) tests were applied to investigate the geopolymer microstructure.

Influence of Erosion Induced by NaCl on the Mechanical Performances of Alkali-Activated Mineral Admixtures

In this paper, the influence of NaCl freeze-thaw (F-T) cycles and dry-wet (D-W) alternations on the flexural, compressive and bonding strengths of alkali-activated fly ash (FA) and a blast furnace slag powder (BFS) is investigated. The considered NaCl concentration is 3%. The effect of polypropylene fibers on the mechanical strengths is also examined. Scanning electron microscopy (SEM), thermogravimetry (TG) and X-ray diffraction (XRD) are selected to discern the mechanisms underpinning the NaCl-induced erosion. The obtained results indicate that the best results in terms of material resistance are obtained with admixtures containing 60% BFS and 40% FA in terms of mass ratio and 3% polypropylene fibers in terms of volume ratio. The maximum rates of decrease of the flexural, compressive and bonding strengths after 300 NaCl F-T cycles are 21.5%, 20.3% and 22.6%, respectively. The corresponding rates of decrease due to NaCl D-W alternations are 28.1%, 26.1% and 31.5%, respectively. The TG curves show that the alkali-activating activity of BFS is higher than that of FA. Moreover, in the first case, the microstructure of the hydration products is more compact. The results also show that NaCl F-T cycles lead to increasing cracks in the alkali-activated BFS.

Effect of Polypropylene Fiber on the Unconfined Compressive Strength of Loess with Different Water Content

Fiber-reinforced soils have been of great interest to experimenters for building foundations’strength performance, time, and economy. This paper investigates the effects of water content and polypropylene fiber dosage and length on loess’s unconfined compressive strength (UCS) according to the central composite response surface design test procedure. The water content is 11%–25%, the mass ratio of fiber to soil is 0.1%–0.9%, and the fiber length ranges from 6–18 mm. The response surface method (RSM) developed full quadratic models of different variables with response values. After analysis of variance (ANOVA), the mathematical model developed in this study was statistically significant (p ≤ 0.05) and applicable to the optimization process. The optimization results showed that the optimal water content values, fiber amount, and fiber length were 16.41%, 0.579%, and 14.90 mm, respectively. The unconfined compressive strength of the optimized specimens was increased by 288.017 kPa. The research results can reference the design and construction of fiber-reinforced soil in practical projects such as road base engineering and foundation engineering.

Effect of polypropylene fiber on properties of modified magnesium-coal-based solid waste backfill materials

Driven by the “dual carbon” goal, modified magnesium-coal-based solid waste backfill materials (MFPB) were gradually used in backfill mining instead of traditional backfill materials. To study the effect of polypropylene (PP) fibers with different contents and lengths on the properties of MFPB, slump tests, rheological tests, uniaxial compressive strength (UCS) tests, permeability tests, and scanning electron microscopy were carried out. The results showed that with the increase in the PP fiber content and length, the flowability of the MFPB characterized by the slump and rheological parameters deteriorated, but the UCS increased significantly, and the permeability first decreased and then increased. The mutual entanglement of PP fibers was the main reason for the poor fluidity of the MFPB. The PP fibers could effectively enhance and improve the strength and toughness of the MFPB by an anchoring effect and irregularly distributed network structure. The strengthening effect mainly occurred in the medium and long term, and the early strengthening effect was not evident. After curing for 28 d, the maximum growth rate of the UCS was 62.5%. After loading failure, the MFPB containing PP fibers still had good integrity and continuity, and there was no shedding phenomenon. The network structure that formed in the early stage due to the PP fibers did not easily segregate and precipitate. The transmission channels between the PP fibers connecting holes were the main reason that the MFPB permeability first decreased and then increased. Therefore, this study can provide a reference for the application of PP fibers to MFPB. Enhancing the performance of the backfill body has important theoretical and practical significance for the development of mine backfill.

Experimental Study on Size Effect and Fracture Properties of Polypropylene Fiber Reinforced Lightweight Aggregate Concrete

In this experimental research, the effects of polypropylene fibers on size effect and fracture properties of lightweight aggregate concrete were studied. Two methods, including size effect method and work of fracture method, were used to investigate and analyze the size effect and fracture properties on different sizes of notched beams. The polypropylene fiber contents were 0.5%, 0.75%, and 1% by volume fraction. The obtained results revealed that increasing the polypropylene fibers in lightweight aggregate concrete relatively decreased the dependence of strength on the size effect parameter, while the addition of polypropylene fibers exhibited significant influence on decreasing the size dependency of ductility and fracture energy in lightweight aggregate concrete. Moreover, the increase of polypropylene fibers improved the total fracture energy (GF), initial fracture energy (Gf), characteristic length (lch), length of fracture process zone (cf), and critical stress intensity factor (KIc) of lightweight aggregate concrete in both size effect method and work of fracture method. This increase was more significant in work of fracture method because of considering the post-peak behavior. The size effect method was suitable and accurate for plain lightweight aggregate concrete. The GF ⁄ Gf ratio increased from 2.88 in plain lightweight aggregate concrete to 12.26 in polypropylene fiber reinforced lightweight aggregate concrete.

Bond strength evaluation of polymer modified cement mortar incorporated with polypropylene fibers

Bond strength is the adhesion between an overlay and a substrate mortar; it is the key parameter ensuring durability and having a monolithic system. A proper bond is essential to resist any stresses associated with volume changes, freeze-thaw cycles, and vibrations at the interface. Polymer-modified cement mortar (PCM) is one of the most well-known adhesive materials, used widely as a binding agent in engineering construction. Two forms of PCM were investigated in this study. These products are known commercially as Sika MonoTop®− 620, a form of repair material for concrete structures, and DCP Cemfix 2CS, which is occasionally used as an adhesive to connect the tiles to the concrete base. The effect of polypropylene fiber with volume fractions of 0, 0.5, 0.75, and 1 % was investigated using three different water-to-binder ratios. A total of 24 distinct mixes were made. The material's compressive strength, flexural strength, and bond strength were all determined. The bond strength of each mix was assessed using the Slant-Shear and Pull-off test methods. The bond strength values derived by Slant-Shear and Pull-off tests had a high correlation, about 85 %. Furthermore, bond strength was connected with the material's compressive and flexural strength with 95 % and 86 % with Slant-Shear, and 80 % and 76 % with Pull-off, respectively.

Strength, Elastic Properties and Fiber-Matrix Interaction Mechanism in Geopolymer Composites.

The current geopolymers have limited mechanical strength against the effect of tension, which makes them susceptible to brittle failure. However, owing to their potential as a sustainable construction material, there is growing interest in improving the poor mechanical properties of geopolymers. This study experimentally investigated crucial properties of polypropylene-fiber-reinforced fly ash-based geopolymer composites. The effects of polypropylene fibers (PPF) addition (0.5%, 1.0% and 1.5% by volume) on the mechanical properties of the geopolymer composites were investigated with respect to compressive and flexural strength, deformation behavior of Young’s and shear moduli, and resilience capacity. In addition, scanning electron microscopy was performed to establish the morphology of the geopolymeric matrix and the fiber–matrix interfacial interaction. The addition of PPF significantly increased the flexural strength: compared with the control, at 7 days it was 27% greater for the 0.5% PPF composite and 65% greater for the 1.0% PPF composite. By 14 days it was 31% and 61% greater, respectively. By contrast, the 1.5% PPF composite had lower strength parameters compared with the control because the fiber dispersion increased the porosity. Similar trends were seen for resilience. The SEM observations showed the dispersion of the fibers and helped elucidate the fiber–matrix interaction mechanism.

Effect of polypropylene fiber and coarse aggregate on the ductility and fluidity of cemented tailings backfill

Effect of polypropylene fiber and coarse aggregate on the ductility and fluidity of cemented tailings backfill

Effects of Cyclic Freezing–Thawing on Dynamic Properties of Loess Reinforced with Polypropylene Fiber and Fly Ash

Periodic freezing–thawing is recognized as a real threat to the mechanical properties of reinforced loess, which has been used in the recent construction of high-speed railways in northwest China; however, the performance of these materials under periodic freezing–thawing and dynamic loading has rarely been investigated. In this work, dynamic triaxial tests were conducted on fly ash- and polypropylene fiber-reinforced loess with different blend ratios and freeze–thaw cycles. The dynamic shear modulus and damping ratio were investigated. The results revealed that cyclic freezing–thawing had a remarkable effect on the dynamic shear modulus and damping ratio, which demonstrated considerable reductions and increases, respectively, after cyclic freezing–thawing. Additionally, the dynamic shear modulus increased notably with the fly ash content and confining pressure and decreased with the water content. Meanwhile, the damping ratio increased with the fiber content and water content and decreased with the fly ash content and confining pressure. Comparatively, the effects of polypropylene fiber on dynamic behavior were found to be not significant. Furthermore, novel models were established to predict the dynamic shear modulus and damping ratio for reinforced loess. The results provide more information towards infrastructure design in seasonal frozen regions.

Effect of polypropylene fiber and shrinkage reducing admixture utilization on water absorption of Khorasan mortar

It is seen that lime-based mortars are frequently preferred in historical and monumental structures. It is known that damages occur depending on the materials used in the building over time. In restoration works, mortars compatible with the original material of the building should be used. For this reason, the use of lime-based mortars is common during restoration work. Accordingly, attention should be paid to the physical and mechanical properties of the mortar to be produced. This study aims to determine the effect of polypropylene (PP) fiber and shrinkage reducing admixture (SRA) on the water absorption properties, which is used to improve the strength and durability properties of Khorasan mortar. As a result, it was determined that PP fiber utilization increased the water absorption ratio due to the formation of voids in the mortars. However, the use of SRA decreased the water absorption ratio due to its effect on the drying shrinkage behavior of the mortars. In cases where both are used together, the effect of fiber use was more dominant.

Effect of Polypropylene Fiber on Frost Resistance and Carbonation Resistance of Manufactured Sand Concrete

Effect of Polypropylene Fiber on Frost Resistance and Carbonation Resistance of Manufactured Sand Concrete

Behaviour of cementitious composites reinforced with polypropylene fibres using restrained eccentric ring test

This paper proposes an eccentric ring test that can be used to determine the behaviour of restrained cement materials with regard to cracking time and select concrete mixtures that are less likely to crack. The effects of polypropylene fibres on the cracking of cementitious composites were investigated using three volume fractions of the fibres and eccentric rings under restrained shrinkage. Different volume fractions (0.4%, 0.6%, and 0.8%) of the fibres lead to considerable improvements in terms of the number of cracks, cracking age, and crack area. A regression model for predicting the cracking properties was developed. The null hypothesis was that the estimated model parameters would be equal to zero. Only parameters whose t-test p-values were less than 0.05 were included in the regression model, and the model effectively predicted the cracking behaviour.

Effect of Polypropylene Fibers and Cement on the Strength Improvement of Subgrade Lying on Expansive Soil

Effect of Polypropylene Fibers and Cement on the Strength Improvement of Subgrade Lying on Expansive Soil

Effect of Polypropylene Fibers on the Shear Strength–Dilation Behavior of Compacted Lateritic Soils

The stress–dilatancy relationship for fiber-reinforced soils has been the focus of recent studies. This relationship can be used as a foundation for the development of constitutive models for fiber-reinforced soils. The present study aims to investigate the effect of recycled polypropylene fibers on the shear strength–dilation behavior of two lateritic soils using the stress–dilatancy relationship for direct shear tests. Results show that fibers improved the shear strength behavior of the composites, observed by increases in the friction angle. Fibers’ orientation at the sheared interface could be observed. The volumetric change during shearing was altered by the presence of fibers in both soils. Overall, results indicate that the stress–dilatancy relationship is affected by inclusions in the soil mix. Results can be used to implement constitutive modeling for fiber-reinforced soils.

Strength and flexural toughness of hybrid fibre reinforced fly ash based concrete

To overcome concrete brittleness and to provide toughness, fibre reinforcement is commonly utilized. Fibre reinforcement to concrete in the form of hybrid fibre is a new concept to achieve individual fibre benefits. In this paper, the effect of polypropylene fibre (PF) and steel fibre (SF) either individually or with different combinations at 1% fibre volume fraction on the strength, flexural toughness, and Ultrasonic pulse velocity (UPV) value of FIBRE-reinforced fly ash (FA) based concrete has been presented. For this purpose, one control mix having 25% FA and 0% fibre and five mixes with different hybrid fibre combinations of 1%PF-0%SF, 0.75%PF-0.25%SF%, 0.50%PF-0.50%SF, 0.25%PF-0.75%SF, and 0%PF-1%SF were cast. ASTM C 1609 method was utilized to evaluate the flexural toughness. Experimental results have shown an improvement in all the above-said properties (expect UPV) by the addition of fibre, but improvement is more significant in mixes with a higher percentage of SF when compared with mixes at a higher percentage of PF. Mix with a hybrid fibre combination of 0.25% PF and 0.75% SF gave the best result among all the fibre-reinforced fly ash-based mixes.

The effect of polypropylene fiber with different length and dosage on the performance of alkali-activated slag mortar

Alkali-activated slag (AAS) cement is a cementitious material with high strength, high durability and environmental protection. AAS is considered as a potential substitute for Ordinary Portland Cement, although its large-scale application is limited by its large drying shrinkage. In this study, we demonstrate that the addition of polypropylene fiber (PPF) can reduce the drying shrinkage of AAS mortar. The influences of PPF length and dosage on the fluidity, mechanical properties, microstructure and impact resistance of AAS mortar are investigated. Three lengths (3 mm, 9 mm and 15 mm), and four dosages (volume fractions of 0.05%, 0.1%, 0.15% and 0.2%) of PPF are used in the AAS mixtures. Test results show that the addition of PPF can reduce the drying shrinkage of AAS mortar, as adding 0.2% of 15 mm PPF can reduce the drying shrinkage by 37.1%. The flexural strength of AAS mortar increases with PPF length and dosage, while introducing long PPF (9 mm and 15 mm) can slightly improve the compressive strength of AAS mortar. Mercury intrusion porosimetry (MIP) and Scanning electron microscope (SEM) results indicate that PPF with 9 mm and 15 mm can reduce the average pore size and improve the microstructure of AAS mortar. At the same time, effective bonding between the matrix and PPF is observed, which is consistent with the enhancement of mechanical properties. Furthermore, PPF addition significantly improves the ultimate toughness of the AAS mortar, which is manifested in the enhancement of impact resistance.

Effect of Polypropylene Fibers on some Mechanical Properties of Concrete and Durability against Freezing and Thawing Cycles

This investigation aims to improve some of the mechanical properties of concrete such as compressive strength, flexural strength, and modulus of elasticity, by using different percentages of polypropylene fibers, and also studying the durability of concrete for freeze-thaw cycles. the study shows a small increment in compressive strength due to adding fibers which were 28.3% compared with increment in flexural strength which was perfect (about 191%), modulus of elasticity also increased by adding fibers. The durability of concrete against freezing-thaw cycles for all mixes was studied. Fiber-reinforced concrete shows more durability against freezing-thawing cycles and less reduction in strength compared with reference mixes without fibers,21.5% reduction in strength for optimum polypropylene fiber concrete while the reduction in strength for normal concrete was found 54.2% in this study.