Addition Of Polypropylene Fibers Research Articles

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.

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.

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.

Experimental study on the effect of polypropylene fiber on compressive strength and fracture properties of high-strength concrete after elevated temperatures

Polypropylene fibers improve the toughness of concrete and reduce the susceptibility of high-strength concrete (HSC) to high temperature spalling. And the mechanical properties of polypropylene fiber reinforced concrete (PFRC) become important after exposure to high temperatures, especially in situations related to engineering uses or repairing concrete structures damaged by fire. This paper presents an experimental study on the compressive strength and fracture properties of PFRC experiencing different temperatures with different fiber contents and lengths. It was shown that the fracture path of concrete becomes longer after experiencing high temperatures. The rate of debonding of mortar and coarse aggregate increases with the temperature rising. The compressive strength of concrete and the peak load and fracture energy of three-point bending beams were both increased by the addition of polypropylene fibers at room temperature, and the compressive strength increased with the increase of fiber content. The addition of polypropylene fibers is able to increase the compressive strength of concrete compared to the control group at experiencing temperatures less than 300 oC. The peak forces of the three-point bending of the concrete beams all show a decreasing trend with the increase in the experienced temperature. The initial slopes of the rising part of the force-loading point displacement and force-crack mouth opening displacement (CMOD) curves all decrease with increasing of temperature, and curves gradually become slower. Addition of polypropylene fibers decreases the peak force of concrete after high temperature. There is no significant pattern in the effect of polypropylene fiber content and length on the peak force and fracture energy of concrete three-point bending beams.

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.

Changes in flexural, tensile and impact characteristics of kerb concrete due to the addition of tyre-derived aggregates and polypropylene fibres

Kerb is an integral part of the roadway that provides structural support and facilitates drainage. When constructed over expansive soils, they face additional tensile stresses due to swelling and shrinkage caused by seasonal moisture variations. Tree roots can also exert additional tensile stresses that need to be absorbed by the kerb. Due to the relatively low deformation tolerance of concrete, premature failures are common. This study, a rigorous laboratory investigation, evaluates the effect of adding tyre-derived aggregate (TDA) and recycled polypropylene fibre on tensile strength, deformation tolerance, flexural toughness and impact resistance of concrete for potential use in road kerb construction. The effect of replacing natural coarse aggregates with recycled concrete aggregates has also been investigated. It has shown that TDA can improve deflection tolerance and polypropylene fibres can help resist larger tensile stresses. 5 % rubber with 0.66 % polypropylene fibres could be used as effective solutions in areas prone to expansive soil movement and tree root migrations.

Evaluation of strength parameters of plain and reinforced concrete with the addition of polypropylene fibers

This research investigates the influence of incorporating small-diameter polypropylene fibers on the mechanical properties of concrete. The studied concrete properties include compressive strength, tensile strength, flexural strength (both plain and reinforced), shear strength, and the mitigation of shrinkage cracks. A total of 92 specimens were meticulously fabricated in the laboratory, comprising cylinders (12 inches in length and 6 inches in diameter), beams (20 x 4 x 4 inches), larger beams (60 x 9 x 9 inches), and slab panels (48 x 48 x 4 inches). During the specimen casting process, a consistent mix with a ratio of 1:2:4 and a water-cement ratio of 0.60 was consistently applied. The polypropylene fiber content varied at 0%, 0.2%, 0.4%, and 0.6% for each property examination. Results indicate a positive impact on all concrete properties studied upon the addition of polypropylene fibers. However, the optimal percentage of polypropylene fibers exhibited variability for each variable and property under investigation. This research contributes insights into the nuanced effects of polypropylene fibers on concrete properties, providing a basis for further exploration and practical application in optimizing concrete performance and durability.

Mechanical investigations of the durability performance of sustainable self-compacting and anti-spalling composite mortars

The durability of the mortar has recently been a critical concern, as it inherently contributes to the overall sustainability and resilience of the structure. This paper aims to address the growing demand for sustainable and durable infrastructure by investigating the effect of incorporating polypropylene, nylon, and jute fibers into self-compacting mortars. The performance of the mortar was tested under high temperatures, chemical attacks (Acid and sulfate attack), and freeze-thaw cycles. The mechanical properties were also examined through strength tests including compressive and flexural strength. Transport properties of mortars were investigated by water absorption, porosity, and sorptivity tests. Seven test mortar mixes were prepared, one of which was a control sample and six had polypropylene, nylon, jute fibers, and an entraining agent. Three of the six mortar mixes had 0.5 % polypropylene, nylon, and jute fibers while the other three had 1 % of these fibers. The effect of acid and sulfate was investigated by parameters of weight losses and reductions in compressive strength of mortar samples while the effect of freeze and thaw was investigated by comparing the drop in compressive strength of mortar specimens with and without fibers. The results revealed a drop in water absorption and porosity of mortar samples containing 0.5 % test fibers as than the control sample, while a slight increase was observed in water absorption and porosity for mortar samples incorporating 1 % of these fibers. The sorptivity of test samples was less than that of the control sample. The compressive strength of mortar samples having 0.5 % fibers was found to have increased, however, a slight reduction was observed in the compressive strength for samples having 1 % of these fibers. The addition of Polypropylene, Nylon, and Jute fibers significantly increased the flexural strength of mortar samples. There were lesser weight losses and compressive strength losses for mortar samples containing Polypropylene, Jute, and Nylon fibers as compared to the control mortar sample when subjected to 5 % HCL, 5 % sodium sulfate, and 28 freeze-thaw cycles. The addition of Polypropylene, Jute, and Nylon fibers has improved the durability performance of self-compacting concrete against different deteriorating phenomena, which eventually can result in durable and sustainable infrastructure.

Effects of polypropylene fibers and aggregate contents on the impact performance of coral aggregate concrete

The paper aims to study the effect of polypropylene (PP) fibers and aggregate contents on the impact compression mechanical performance of coral aggregate concrete (CASC). 5 PP fiber contents (0 kg/m3, 1 kg/m3, 2 kg/m3 3 kg/m3, 4 kg/m3), 3 natural gravel replacement ratios (0 %, 40 %,70 %), and 3 impact pressures (0.10 MPa, 0.12 MPa, 0.14 MPa) were designed for the split Hopkinson pressure bar (SHPB) test herein. The PP fiber contents and gravel replacement ratios effects on the impact compressive properties of CASC were assessed in term of the stress-strain curve, the strain rate effects and the toughness. The results showed that the dynamic compressive strength enhanced obviously with the increasing PP fiber contents and gravel replacement ratio, while the excessive fiber can degrade its properties instead. There exists the apparent strain rate effect of dynamic compressive strength and dynamic increase factor. The addition of PP fiber and the gravel can also improve the toughness of CASC and weaken the strain rate sensitivity. Eventually, the dynamic constitutive model based on ZWT constitutive model was established by considering the material damage, which can excellently forecast the dynamic stress-strain curve of CASC and the dynamic mechanical properties.

Strength and Stiffness Evaluation of a Fiber-Reinforced Cement-Stabilized Fly Ash Stone Dust Aggregate Mixture

The utilization of waste fly ash in road construction is primarily confined to its use in embankment filling or as a stabilizer when combined with lime and cement. Its application in structural pavement layers, such as the base and subbase, faces a challenge due to the high volume of fine particles, which renders it brittle when stabilized. In this study, fly ash was blended with stone dust and aggregated to enhance its gradation. Subsequently, it was stabilized with cement to bolster its strength, rendering it suitable for pavement use. Additionally, polypropylene (PP) fibers were introduced to mitigate the brittleness of the mixture. An extensive experimental investigation was conducted to assess the strength and stiffness properties, including compressive strength, indirect tensile strength, flexural strength, cyclic indirect tensile modulus, and flexural modulus of fiber-reinforced cement-stabilized mixtures of fly ash, stone dust, and aggregate. The experimental results reveal that the addition of PP fibers up to 0.25 wt.% enhances compressive strength, but any further increase in fiber content leads to a reduction in strength. However, indirect tensile strength and flexural strength show improvement, with an increase in fiber percentage up to 0.5 wt.%. It was observed that cement content plays a dominant role in stabilizing these materials. Appropriate relationships have been established between strength and modulus parameters for stabilized mixtures. Based on the strength and stiffness study, a combination of 70% fly ash and 30% stone dust aggregate with 6% cement can be considered for the base layer. Regarding the behavior of indirect tensile strength and flexural strength, an optimum fiber percentage of 0.35% is recommended.

An investigation of the durability of ultra-lightweight high-strength geopolymeric composites

As promising and sustainable construction materials, ultra-lightweight high-strength geopolymeric composites (ULHSGCs) may be exposed to harsh corrosive environments. This study is designed to examine the durability of a new ULHSGC with a compressive strength ≥70 MPa and a density ≤1500 kg/m3. In preparing the ULHSGC, ground granulated blast furnace slag (GGBS) and silica fume (SF) were used as the binder, and fly ash cenospheres (FACs) and hollow glass microspheres (HGMs) were used as aggregates. A series of measurements, including accelerated carbonation, rapid chloride migration (RCM), sulfate resistance, X-ray diffraction (XRD), and mercury intrusion porosimetry (MIP) tests, was conducted to determine the effects of the SF content, Na2O content, SiO2/Na2O ratio and fibre type on the durability of the ULHSGC. The results indicated that the proposed ULHSGC with 10–15 % SF content and 6–7% Na2O content exhibited excellent compressive strength, resistance to carbonation, and resistance to chlorine penetration as well as suitable resistance to sulfate attack. Versions of the ULHSGC with lower SiO2/Na2O ratios had better compressive strengths, resistances to chloride penetration and resistances to sulfate attack but lower resistance to carbonation. The addition of polypropylene (PP) fibres and polyethylene (PE) fibres increased the porosity, which reduced the durability of the ULHSGC. However, given the significant contribution of the fibres to the compressive strength, the negative effect of adding 0.5 vol% fibres on the durability was acceptable.

Optimizing characteristics of high-performance concrete incorporating hybrid polypropylene fibers

The purpose of this investigation is to assess and optimize the impact of hybrid polypropylene fibers (coarse monofilament and staple fibers) on the mechanical characteristics and resistance to elevated temperature of high-performance concrete. Concrete mixtures were designed using central composite design under response surface methodology. Slump test, compressive strength, flexural strength, impact test, elevated temperature resistance and microstructure of concrete were the tests performed. The slump values were slightly decreased with the addition of polypropylene fibers. Concrete mixtures reinforced with hybrid polypropylene fibers have significantly improved in terms of compressive strength and flexural strength ranged from 1.96% to 12% and 14.28% to 41.9%, respectively, at age 56 days compared to control mixture without fibers. The hybridization of 5 kg monofilament and 0.75 kg staple fibers achieved the highest compressive strength (84.6 MPa), flexural strength (14.9 MPa), and the optimum impact resistance at age 56 days. The increase of coarse monofilament fibers significantly improved the spalling resistance performance. The residual compressive strength of mixture containing 5 kg monofilament and 0.75 kg staple fibers up to 63.8% of the initial strength after exposure to 800 C0. Strong relationships were obtained for predicting and optimizing compressive and flexural strength of concrete incorporating hybrid polypropylene fibers.

Mechanical characterisation and small-scale life-cycle assessment of polypropylene macro-fibre blended recycled cardboard concrete

This paper presents an experimental study and findings on the requalification of waste cardboard as a fine-aggregate replacement in the development of waste-based concrete. The design of eco-efficient and green-star concrete has become a significant focus, driven by the impact of industrial and municipal waste on both the environment and the global economy. The study aimed to utilise materials such as waste cardboard, polypropylene, and ground-granulated blast furnace slag as partial replacements for Ordinary Portland Cement and fine natural aggregate. It specifically focused on developing techniques for processing recycled cardboard into an aggregate suitable for this study. Six concrete batches were cast with incremental dosages of finely processed recycled cardboard and a fixed dosage of recycled polypropylene macro-fibres. An experimental program was conducted to determine fresh and mechanical properties at 7 and 28 days. The results were used to identify an optimal dosage level of waste cardboard suitable for commercial use. Additionally, a small-scale life-cycle assessment was performed to evaluate the environmental impact of the hybrid concrete mix. The processed cardboard exhibited desirable rheological and mechanical properties, making it a suitable fine-aggregate replacement. The addition of recycled polypropylene fibres enhanced flexural and tensile strength, establishing the blend as a suitable concrete mixture design for real-world applications. Furthermore, the life-cycle assessment highlighted the effectiveness of the mixture designs when compared to benchmark concrete mixtures.

Pull-out behaviour of steel fibres embedded in ultra-high-performance concrete after exposure to high temperatures

The paper examined the bond-slip behaviour of steel fibres embedded in ultra-high-performance concrete (UHPC) after exposure to elevated temperatures. Different types of steel fibres were cast into the halved UHPC dog-bone-shaped samples, including straight fibres, three types of hooked-end fibres and corrugated fibres. The bond response was investigated through single fibre pull-out tests on the samples unheated and heated to 200, 400 and 600 °C. In addition, the effects of polypropylene (PP) fibre addition and heating rate on steel fibre’s bond behaviour were also investigated. The results revealed an increase in bond strength when the straight and hooked-end fibre samples were heated to 200 °C, while the bond strength of the corrugated fibre decreased at the same temperature. Bond strength reductions were observed at higher temperatures. In addition, the straight fibres led to the lowest pull-out resistance as both the hooked-end and the corrugated fibres significantly enhanced the bond strength. With the hooked-end or corrugated fibres, the failure mode gradually shifted from pull-out failure to fibre rupture. Besides, adding PP fibres increased the bond strength of straight fibres at 400 °C but reduced the bond strengths of hooked-end fibres at ambient and high temperatures. High heating rate also led to a greater bond strength for the straight fibres at 200 °C and 400 °C.

Effect of the Addition of Dispersed Reinforcement on the Resilient Modulus of Slightly Cemented Non-Cohesive Soil

Abstract The aim of this article is to determine the effect of the addition of dispersed reinforcement on the resilient modulus of non-cohesive soil used as material for improved subgrade or subbase course of the pavement structure. Resilient modulus (M r) is a parameter used in road construction, which characterises soil subgrade or base aggregates stiffness in flexible pavement subjected to the traffic load. This article presents laboratory test results of non-cohesive coarse material (gravelly sand – grSa – without fines) with the addition of 1.5% cement and dispersed reinforcement – polypropylene fibres in lengths of 12, 18 and 40 mm. Tests were conducted on the samples with various percentages of fibres (0, 0.2 and 0.3%) relating to the dry mass of the soil. Samples were compacted according to the standard Proctor (SP) and modified Proctor (MP) methods. Main laboratory tests were conducted in the triaxial apparatus enabling testing samples subjected to cyclic loads according to AASHTO T307 standard. Resilient modulus was determined after 7 and 28 days of curing. The results indicate the influence of fibre amount, fibre length, and curing time on the M r of the soil modified with 1.5% of cement. The obtained results were also influenced by the method of compaction. The addition of polypropylene fibres decreases the resilient modulus of soil stabilised by 1.5% of cement. The best results of dispersive reinforcement were obtained for samples containing 0.3% of fibres with a length of 18 mm, compacted by the MP methods.

Mechanical Properties of Fiber-Reinforced High-Volume Fly-Ash-Based Cement Composite—A Long-Term Study

This article presents the long-term mechanical properties of a novel cement composite, no-aggregate concrete (NAC), containing 80% of low-calcium (class F) fly ash (F-FA) and 20% ordinary Portland cement (OPC) without aggregates. The study investigates the effect of adding polypropylene fibers (PPFs) in varying volume fractions to NAC by conducting compressive, splitting tensile, flexural, bond strength, and sorptivity tests, emphasizing the morphological features over a curing duration of up to three years. The results indicate that adding PPF has an insignificant effect on compressive strength. However, flexural, splitting tensile, and bond strength improve with an increasing volume fraction of PPF. The addition of PPF achieves a ductile failure which is desirable. The initial and final water absorption rate (sorptivity) reduces with the addition of PPF. Further, scanning electron microscopy (SEM) images reveal dense precipitation of C-S-H, while energy-dispersive X-ray spectroscopy (EDS) quantifies the hydration products. The ultrasonic pulse velocity (UPV) affirms the composite’s excellent quality.

Study on Mechanical and Flow Properties of Cemented Sulfur Tailings Backfill Considering the Influence of Fiber Type, Fiber Content and Addition Method

Previous studies have confirmed that for cemented tailings backfill, mechanical properties are improved through the addition of fiber. However, for fiber-reinforced cemented sulfur tailings backfill (FRCSTB), physical and flow properties are still unknown. In this paper, the changes in fluidity, splitting tensile strength (STS) and uniaxial compressive strength (UCS) of cemented sulfur tailings backfill (CSTB) are analyzed in detail. Secondly, regarding the addition of glass fiber and polypropylene fiber, the changes in the fluidity, STS and UCS of the CSTB, resulting from the fiber length, fiber content and method of fiber addition used, were analyzed. Moreover, the relationship between the UCS and fiber content is established. Finally, the mechanism behind the influence of fiber and sulfur content on the mechanical properties of CSTB is revealed. The results indicate that with the increase in sulfur content, the fluidity of the tailings slurry exhibits exponential growth. During the process of increasing sulfur content, the UCS and STS of CSTB initially increase and then decrease, reaching maximum values at 12% sulfur content. Similarly, at a fiber content of 0.6%, the UCS and 28d STS of CSTB reach their maximum values. In terms of enhancing the mechanical properties of CSTB, the effectiveness of glass fibers surpasses that of polypropylene fibers. In addition, regarding the improvement of the UCS of CSTB, the mixed addition of fibers is obviously worse than that of fiber alone. However, in terms of enhancing the STS of CSTB, the mixed addition of fibers outperforms the single addition of polypropylene fiber. From a microscopic perspective, polypropylene and glass fiber are able to form strong cohesion with the cement–tailings matrix and effectively prevent the formation and expansion of pores and cracks.

Combined effect of fly ash and fiber on spreadability, strength and water permeability of foam concrete

Strength and permeability are the two critical properties of interest for various applications of foam concrete (FC). These properties are well known to be highly dependent on parameters such as density, mix composition and microstructure of FC. Among various measures to enhance the strength and permeation characteristics of FC, incorporation of fly ash and polypropylene fiber has been proven to be effective solutions by various studies. In terms of permeability, though the measurement of air/water permeability has been suggested by various methods, usually such measurements are limited to a pressure of 3 bar. For higher pressures (as recommended in codal provisions) no to limited work is available. In this paper, variation in spreadability, permeability, compressive strength and split tensile strength of FC due to replacement of 50% of sand with Class F fly ash and incorporation of polypropylene fiber is investigated on a systematic basis. For the measurement of permeability at higher pressures (>3 bar), use of novel sealing mechanism using 5 mm thick rubber membrane as sealant with iron spiral cylinder and clamp as casing, is attempted in this work. The present study is first of kind of study using the above-mentioned sealing mechanism for measurement of permeability of FC at higher pressures. Further, only scanty literature is available on permeation behavior of FC with fly ash (as filler) and polypropylene fiber. As per the present findings, particularly in lower density mixes (say density 1000 kg/m3) tested at age of 56 days, replacement of 50% of fine aggregate (by weight) by Class F fly ash results in 114% enhancement in compressive strength and 69% reduction in permeability. In addition, mixes with 0.05% of total solids replaced with polypropylene fiber (by weight) show 25% reduction in compressive strength and 500% increase in permeability in comparison to FC mixes without fly ash and polypropylene fibers. Thirdly, considering mixes with addition of fly ash and polypropylene fibers both, it is found that the effect of fly ash is more predominant from strength perspective than fiber. From permeability perspective however, the fibers control the permeability significantly due to their higher impact on microstructure of FC.

Experimental investigations on hybrid fibre reinforced alkali activated concrete mixes

The present study attempts a detailed evaluation of the strength performance of Fiber reinforced Alkali Activated Concrete mixes containing fly ash and ground granulated blast furnace slag (GGBS) as a sole binder. Fly ash and GGBS, a by-product obtained from industries, is incorporated in the AASC mixes as a full replacement to ordinary Portland cement (OPC). Initially OPC and AASC mixes are designed to obtain M30 grade. This experiment investigates the effect of the addition of hooked end steel fiber and polypropylene fiber on the physical and mechanical properties of high ductile Alkali Activated Concrete. Geo-polymer is called one of the best substitutes for ordinary Portland cement (OPC) because of its benefits over OPC. Hooked end steel fiber of length 35 mm and diameter 0.5 mm with aspect ratio of 70, polypropylene fiber of 12 mm length is used in hybrid manner, with five different fiber volume fractions of 0.25 & 1.25%, 0.50 & 1%, 0.75 & 0.75%, 1 & 0.50% and 1.25 & 0.25% respectively. All mixes of fiber reinforced Alkali Activated Concrete includes 50% of GGBS and 50% of fly ash from total binder content. Alkali activators used are, sodium hydroxide pellets and sodium silicate liquid. The experimental result indicated that, the addition of fibers affects the workability by 20–30% down. In the mechanical property wise, fibers variation doesn’t affect the compressive strength much. Flexure and tensile strength increase by about 20–40%, compared to other mixes without any fiber’s addition. This increment of strength is due to addition of both the fibers in hybrid way. Using Alkali Activated Concrete helps to reduce emission of carbon dioxide, which happens from manufacturing of cement. Geo polymer concrete make the environment very much sustainable by maintaining global warming in a limit.