Uniform Dispersion Of Fibers Research Articles

Fresh, Compressive and Direct-Tensile characterization of Engineered Cementitious Composite

A new category of high-performance fiber-reinforced composite broadly known as Engineered Cementitious Composite (ECC) has gained rapid attention in the construction industry in recent years. The exceptional behaviour of ECC, therefore high ductility, toughness, and durability, make it a promising material for various structural applications such as tunnel inner lining, dam and bridge deck slab construction. This investigation aims to study the fresh and mechanical characteristics of ECC, including workability, compressive, and direct tensile strength. A total of 15 ECC mixes are prepared with varying superplasticiser-binder ratio (0.200, 0.225, 0.250, 0.275 and 0.300 %), sand-binder ratio (0.35, 0.40 and 0.45) and a constant water-binder ratio (0.27). The mini-slump cone test was performed to examine the workability of the fresh ECC mixtures. The results showed that using a higher content of the superplasticiser resulted in an upsurge in both the workability of the fresh ECC mixtures and the mechanical strength of ECC, particularly the tensile strength. Apart from this, both the mechanical tests are performed at the 7 and 28 days. As per the results, both the compressive strength and direct tensile strength of ECC are found to be comparatively higher than that of the conventional mix. In conclusion, ECC is an efficient construction material for various structural applications, especially for the latest 3D printing construction techniques. The uniform dispersion of fibers significantly improves the tensile strength and ductility of ECC, making it a suitable material for seismic-resistant structures.

Potential 3D filament of Janeng (Dioscorea hispida Dennst) starch: Preparation and characterization

The preparation and characterization of filaments from janeng have been studied. The janeng filament (PCl-JS) process starts with the preparation and gelatinization of janeng starch, and then the resulting starch gelatinization, which is usually called thermoplastically processable starch (TPS) is carried out by filament processing by mixing PCl-g-GMA and JS at a temperature of 170 °C and 80 rpm for 15 min. The prepared filaments were analyzed. SEM studies show that the fracture surface of PCl-JS0 filaments provides a uniform fiber dispersion, in contrast to the morphology showing large and interconnected starch domains as the starch concentration increases from 1% to 9%. The intensity of hydrogen bonds observed in the spectrum via FTIR increased in band as the concentration of JS increased. XRD analysis observed that the crystallinity and crystal size of filaments without starch were higher than those of other PCl filaments that had undergone modification with starch. Mechanical analysis showed that starch did not have a negative effect on the tensile strength of the filaments, indicating good compatibility between JS and the PCl matrix. When the additional concentration of JS increased to 9%, the strength of PCl-JS filaments increased to 37 MPa, which was caused by the higher crystallinity induced by starch. The glass temperature of the filament sample was observed using DSC, which showed that PCl without JS occurred at 48.2 °C and shifted (+2 °C) towards 49.4 °C when JS was added. For all DSC curves, the exothermic peak was observed around 56–59 °C. The melt flow behavior of PCl-JS filaments decrease with increasing starch content.

Automated Fiber Placement Path Planning and Analysis of Pressure Vessels.

The automated fiber placement (AFP) process faces a crucial challenge: the emergence of out-of-plane buckling in thermoplastic prepreg tows during steering, significantly impeding the quality of composite layup. In response, this study introduces a novel approach: the development of equations for wrinkle-free fiber placement within composite pressure vessels. The investigation encompasses a detailed analysis of prepreg trajectories in relation to shell geometry, accompanied by an in-depth understanding of the underlying causes of wrinkling on dome surfaces. Moreover, a comprehensive model for shell coverage, grounded in placement parameters, is meticulously established. To validate the approach, a simulation tool is devised to calculate press roller motions, ensuring the uniform fiber dispersion on the mandrel and achieving flawless coverage of the shell without wrinkles. This innovative strategy not only optimizes the AFP process for composite layup but also remarkably enhances the overall quality of composite shells. As such, this research carries significant implications for the advancement of composite manufacturing techniques and the concurrent improvement in material performance.

Engineered cementitious composites - a review

Engineered Cementitious Composites (ECC) is also known as bendable concrete, characterized by tight crack width control. As we know the concrete is brittle in nature, expected to fail catastrophically. To minimize the damages caused by the concrete failure in seismic region we go for special detailing to enhance the ductility nature of concrete members, which leads to a complicated design. To overcome this problem a new type of composites are designed called Engineered Cementitious Composites based on a combination of structural engineering and micromechanics. This paper deals with the literature survey on micromechanics design to achieve the pseudo strain hardening behaviour, i.e. to achieve two criteria’s namely i) Strength Criteria ii) Energy criteria. Both Reinforced Concrete and Fiber Reinforced Concrete shows strain softening behaviour after the appearance of the first crack whereas the ECC shows strain hardening behaviour after the appearance of first crack because of the presence of randomly oriented discontinuous fibers. Regarding Strength criteria, Fiber bridging stress plays a major role and for energy criteria, Matrix toughness plays a major part. By tailoring these two parameters, strain hardening behaviour of the composite can be achieved. Apart from these two parameters mixing of fresh ECC is also an important factor to be considered, since uniform dispersion of fibers leads to bridging of the cracks which makes the composite to have a multiple fine cracks before failure instead of having a big single crack.

Water uptake and interfacial shear strength of carbon/glass fiber hybrid composite rods under hygrothermal environments: effects of hybrid modes

The hygrothermal aging of fiber reinforced polymer (FRP) composite rod served as bridge cables played a key role on the long-term service performances. In the present paper, two types of pultruded carbon/glass fiber reinforced epoxy hybrid composite rods, one with uniformly dispersed carbon and glass fibers, and the other with glass fiber shell and carbon fiber core, were investigated on the water uptake and interface shear strength. The aging condition was immersion in deionized water at 40 °C, 60 °C and 80 °C. Interface shear strength degradation mechanism was revealed by thermal analysis and microstructure analysis. It was found that the water absorption of two types of hybrid rods represented the two-stage behavior. For the rod of uniform fiber dispersion, more water uptake in the second stage occurred compared to that of the shell/core rod, which was attributed to the resin rich area and interface debonding of fiber/resin. Long-term hygrothermal exposure led to a remarkable degradation in the interfacial shear strength of the rods, up to 17.5% ∼ 42.1%. The resin plasticization and interface debonding were the main factors contributed to the strength degradation. Based on the Arrhenius equation, the long-term life prediction of the interfacial shear strength under two typical bridge service environments was conducted to the design guideline of hybrid rods in the bridge engineering.

Application of Response Surface Methodology and Box-Behnken Design for the Optimization of the Stability of Fibrous Dispersion Used in Drilling and Completion Operations.

Fibers are extensively used as a fluid additive in the oil and gas industry to improve hole-cleaning performance, control fluid filtration loss, and enhance hydraulic fracturing effectiveness. Generally, a small amount of fiber is dispersed in the base fluid to achieve the desired results without increasing the viscosity of the base fluid. Nevertheless, sustaining a uniform fiber dispersion can be challenging under wellbore conditions, which is essential for fibers’ functionality. Consequently, a better understanding of fiber suspension or stability in base fluids is necessary for their efficient utilization in drilling and completion operations. In this study, response surface methodology (RSM) and box–behnken design (BBD) are used to investigate the stability of fiber in polymeric base suspensions, including carboxy methyl cellulose (CMC), polyacrylamide (PAM), and xanthan gum (XG). The BBD of three factors was selected to observe the influence of polymer concentration, fiber concentration, and temperature on fibrous suspension stability, with three levels of design factors (low, mid, and high) and two fiber aspect ratios (3 and 12 mm fibers). The base fluid polymer concentration ranged from 1 to 8 vol %, fiber concentration ranged from 0.01 to 0.08 wt %, and the temperature was varied from 25 to 80 °C. The stability measurements were analyzed using Minitab, subsequently, evaluating the factors’ impact and interactions and determining the optimum conditions for the stability of the fibrous suspensions. The results predicted by the developed model were in good agreement with the experimental results R2 ≥ 0.91–0.99. The sensitivity analysis showed that base fluid polymer concentration is the most significant factor affecting fibrous suspension stability. At high polymer concentrations, fiber concentration and temperature effects are minimal, while the temperature effect on the stability was observed at low concentrations (e.g., low suspension viscosities). The fiber aspect ratio indirectly affects system stability. Long fibers have a better tendency to entangle and form a structured network, which in turn hinders the buoyancy that induces individual fiber migration. On the contrary, short fibers do not form a network, allowing them to easily migrate to the surface and agglomerate at the top layer (unstable region). Optimization results revealed that suspensions with viscosities above 50 mPa·s are sufficient to maintain the stability of the suspensions at ambient (25 °C) and elevated (80 °C) temperatures.

Preparation and Characterization of Composite Blends Based on Polylactic Acid/Polycaprolactone and Silk

Silk-reinforced polylactic acid/poly ε-caprolactone composites containing 1-7 wt % of silk fibers were fabricated through the melt-mixing method. The composites were then characterized by implementing Fourier transform infrared (FTIR), differential scanning calorimetry (DSC) and rheometry to investigate functional groups, thermal properties, rheological properties, and intrinsic viscosities of each composite. The crystallinity of the composites was found to decrease upon addition of silk, while, both storage modulus ( G') and loss modulus ( G″) were increased which is an indication of interface bonding between the polymer and silk. The composite containing 5% silk fiber (PLACLS5) showed the optimum results. The composites' morphological analysis was conducted by scanning electron micrograph coupled with energy dispersive X-ray (SEM-EDX) mapping to assess the fiber dispersion in the composite matrix. The contact angle measurements and in vitro degradation were performed to evaluate the hydrophilicity, free surface energy, and hydrolytic degradation of the composites. The results implied that addition of higher contents of silk fiber could reduce the degradation duration of the composites, which is due to the high hydrophilicity of the fiber, uniform fiber dispersion within the matrix, the porous structure, and consequently, the hydrophilic behavior of the composites. These composites can be great alternatives for both soft and hard tissue engineering applications.

Rice straw cellulose nanofibrils reinforced poly(vinyl alcohol) composite films

In this study, cellulose nanofibrils (CNFs), obtained from the chemical treatment of steam exploded rice straw fibers and the following oxidation by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated system, were utilized to prepare the reinforced polyvinyl alcohol (PVA) composite films by solution casting method, and the morphology, transparency, thermal stability, mechanical properties and water absorption of these rice straw CNFs/PVA composite films were also investigated compared with the rice straw cellulose microfibrils (CMFs) reinforced PVA composite films. As compared with the rice straw CMFs/PVA composite films, the rice straw CNFs/PVA composite films exhibited more uniform fiber dispersion, better mechanical properties and transparency, and similar thermal stability. However, the rice straw CNFs/PVA composite films showed weaker water resistance than the rice straw CMFs/PVA composite films due to the existence of more polar groups in rice straw CNFs.

Poly(ε-caprolactone) Biocomposites Based on Acetylated Cellulose Fibers and Wet Compounding for Improved Mechanical Performance

Poly(e-caprolactone) (PCL) is a ductile thermoplastic, which is biodegradable in the marine environment. Limitations include low strength, petroleum-based origin, and comparably high cost. Cellulose fiber reinforcement is therefore of interest although uniform fiber dispersion is a challenge. In this study, a one-step wet compounding is proposed to validate a sustainable and feasible method to improve the dispersion of the cellulose fibers in hydrophobic polymer matrix as PCL, which showed to be insensitive to the presence of the water during the processing. A comparison between unmodified and acetylated cellulosic wood fibers is made to further assess the net effect of the wet feeding and chemical modification on the biocomposites properties, and the influence of acetylation on fiber structure is reported (ATR-FTIR, XRD). Effects of processing on nanofibrillation, shortening, and dispersion of the cellulose fibers are assessed as well as on PCL molar mass. Mechanical testing, dynamic mechanical thermal a...

Characterizing the Mechanical Properties of Fused Deposition Modelling Natural Fiber Recycled Polypropylene Composites

The objective of this investigation was to characterize the performance of natural fiber reinforced polypropylene composites in fused deposition modelling (FDM). Composite filaments comprising of pre-consumer recycled polypropylene with varying contents of hemp or harakeke fibers were extruded from which tensile test specimens were made using FDM. Filament and test specimens were tensile tested and properties were compared with plain polypropylene samples; the ultimate tensile strength and Young’s modulus of reinforced filament increased by more than 50% and 143%, respectively, for both 30 wt % hemp or harakeke compared to polypropylene filament. However, the same degree of improvement was not seen with the FDM test specimens, with several compositions having properties lower than for unfilled polypropylene. SEM analysis of fracture surfaces revealed uniform fiber dispersion and reasonable fiber alignment, but porosity and fiber pull-out were also observed. Fiber reinforcement was found to give benefit regarding dimensional stability during extrusion and FDM, which is of major importance for its implementation in FDM. Recommendations for optimization of processing in order to enhance build quality and improve mechanical properties are provided.

Processing of PLA/sisal fiber biocomposites using direct- and extrusion-injection molding

ABSTRACTThe processing strategy adopted to develop biocomposites plays a significant role in determining their characteristics. The present experimental investigation explores the feasibility of using direct-injection molding (D-IM) process for processing of sisal fiber (3 mm and 8 mm) reinforced poly-lactic acid biocomposites with a fiber weight fraction of 30%. For a comparative analysis, mechanical and morphological behavior of biocomposites developed using D-IM process is compared with biocomposites developed using extrusion-injection molding (E-IM) process. The mechanical behavior in terms of tensile, flexural and impact properties is compared and discussed in relation to extracted fiber morphology and fiber orientation as well as dispersion within the developed biocomposites. Morphological investigation of extracted fibers revealed severe fiber attrition and fiber length variation during E-IM process as compared with D-IM process. However, short sisal fiber (3 mm) reinforced biocomposites developed using both the processes exhibit uniform fiber dispersion and orientation, resulting in comparable mechanical properties. The tensile and flexural strength of D-IM-SF biocomposites increased remarkably by 34.7% and 15.9%, respectively, as compared with D-IM-LF biocomposites. Similarly, the tensile and flexural modulus of D-IM-SF biocomposites increased significantly by 92.5% and 56.7%, respectively, as compared with D-IM-LF biocomposites. However, D-IM process incorporating long fibers exhibit better impact properties.

Ultra-high-ductile behavior of a polyethylene fiber-reinforced alkali-activated slag-based composite

This paper presents an experimental study of the meso-level composite properties of an ultra-high-ductile polyethylene-fiber-reinforced alkali-activated slag-based composite. Four mixtures with 1.75 vol% of polyethylene fibers were prepared with varying water-to-binder ratio. The viscosity of the matrix was controlled to ensure a uniform fiber dispersion. A series of experiments, including density, compression, and uniaxial tension tests, was performed to characterize the mechanical properties of the composite. The test results showed that the average tensile strength to compressive strength ratio of the composites was 19.8%, nearly double that of normal concrete, and the average crack width was 101 μm. It was also demonstrated that tensile strain capacity and tensile strength of up to 7.50% and 13.06 MPa, respectively, can be attained when using the proposed polyethylene-fiber-reinforced alkali-activated slag-based composites.

Study on flax fiber toughened poly (lactic acid) composites

ABSTRACTPoly (lactic acid) (PLA) is a renewable and biodegradable polymer with high modulus, high strength but low toughness. Blending PLA with plant fiber has been believed an available strategy to improve the toughness of PLA. PLA/Flax composites were fabricated by extrusion and injection molding processes. The flax fiber surfaces were modified before blending to improve the compatibility, and the chemical structures of both untreated and treated fiber were characterized by Fourier transform infrared spectroscopy. Results of mechanical test showed that the impact strength and elongation at break of PLA/Flax composites were remarkably higher than PLA. The impact fractures of PLA/Flax composites were also observed by scanning electron microscope. The results showed uniform dispersion of fibers in PLA matrix and good compatibility between treated fibers and PLA matrix. Moreover, it can be observed that crazing propagation was hindered by fibers and transcrystalline developed along fibers by polarized optical microscope. Differential scanning calorimetry analysis was carried out to study the crystallinity of PLA and it was found that incorporation of fiber improved the crystallinity of PLA. The toughening mechanism of PLA/Flax composites was discussed according to the results. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42573.

Citius, altius, fortius/faster, higher, tougher: pushing ahead the boundaries of structural concrete through fiber-reinforced cementitious composites with adapted rheology

Fiber-reinforced self-compacting concrete (FR-SCC) combines the benefits of highly flowable concrete in the fresh state with the enhanced performance in the hardened state in terms of crack control and fracture toughness provided by the dispersed fiber reinforcement. Thanks to the suitably adapted rheology of the concrete matrix, it is possible to achieve a uniform dispersion of fibers, which is of the foremost importance for a reliable performance of structural elements. Balanced viscosity of concrete may also be helpful to drive the fibers along the concrete flow direction. An ad hoc designed casting process may hence lead to an orientation of the fibers “tailored” to the intended application, which is along the anticipated directions of the principal tensile stresses within the structural element when in service. This converges toward a “holistic” approach to the design of structure made with highly flowable/self-consolidating fiber-reinforced concrete (FRC), which encompasses the influence of fresh state performance and casting process on fiber dispersion and orientation, and the related outcomes in terms of hardened state properties. A thorough understanding is required of the mechanisms underlying the connection between mix-design and fresh state performance, on one hand, and the dispersion and orientation of the fibers on the other hand, also in the context with monitoring and prediction to achieve the anticipated structural performance. In this framework, this article, after a review of the authors’ main research results on the aforementioned topics, will focus on the research needs which have to be urgently tackled in order to address the use of this kind of advanced cement-based materials for high-end structural applications.

Microcellular injection molding of polypropylene and glass fiber composites with supercritical nitrogen

Microcellular injection molding of polypropylene and glass fiber composites (PP-1684/GF-950) was performed using supercritical nitrogen as the physical blowing agent. Based on design of experiment matrices, the influences of glass fiber content and operating conditions on cell structure, glass fiber orientation and mechanical properties of molded samples were studied systematically. The results showed the cell morphology and glass fiber orientation of foaming parts were definitely influenced by the cooling and shear effects. The mechanical properties of foamed polypropylene–glass fiber composites could be effectively enhanced by improving the cell morphology, dispersion state and orientation of the glass fiber at optimal weight percentage [Formula: see text]. And the optimal conditions for injection molding were obtained by analyzing the signal-to-noise ratio analysis of the mechanical properties of the molded samples, which were a shot size of 36 mm, a supercritical N2 weight percentage of 0.4%, an injection speed of 60%, a melt temperature of 190℃ and a mold temperature of 70℃. The molded specimens of polypropylene–glass fiber composites, produced under those optimal conditions, exhibited very uniform fiber dispersion and microcellular structures with an average cell size less than 30 µm. And the mechanical properties normalized by weight ratio of the microcellular samples were increased significantly, especially the impact strength.

Experimental Methods on Glass Fiber Reinforced Self Compaction Concrete

Self Compacting Concrete (SCC) is able to flow under its own weight and completely fill the formwork, even in the presence of congested reinforcement, without any compaction, while maintaining homogeneity of the concrete. Compaction is difficult to be done in conditions where there are dense reinforcement and large casting area. Usage of SCC will overcome the difficult casting conditions and reduce manpower required. Addition of fibers will enhance the tensile and ductile behavior of concrete with brittle nature. SCC was added with relatively short, discrete, and discontinuous glass fibers to produce Glass Fiber Reinforced Self Compacting Concrete (GFRSCC). The purpose of this study is to investigate the workability and mechanical properties of plain SCC and GFRSCC. The laboratory testing included slump flow test, L-Box test, sieve segregation resistance test, density test, ultrasonic pulse velocity (UPV) test, compressive strength test, splitting tensile strength test, and flexural strength test. The dosage of super plasticizer required increased as fiber content increased. There has been a lack of studies for productivity improvement in the construction industry. A review of literature was done where an inventory of productivity related factors were found and interpolated. A survey of construction practitioners was conducted to rank and determine the degree of influence of various factors on construction productivity. We have selected the major factors such as Material, Labor and accessed it both quantitatively and qualitatively for a real time construction project. The results enhanced profit and productivity. I. Introduction SCC can be considered as a concrete with high flow ability that can be placed and compacted under its own weight without any external vibration, assuring complete filling of formworks and also the complete covering of the reinforcing bars even when the space between the reinforcements is very narrow. SCC is characterized by high flow ability in its fresh state and increased strength in its hardened state because of a compact matrix structure. SCC has many advantages that include faster construction, better surface finishes, easier placing, reduction in noise levels and improved durability. The term Fiber Reinforced Concrete (FRC) can be defined as a concrete structure having randomly oriented and dispersed fibers. Fibers can be defined as small wire-like reinforcements which are made of either steel or polymers having high ductility. The fibers are produced in a wide range of sizes and shapes, stiff or flexible etc. Addition of fibers into concrete improves the overall ductility of the concrete imparting toughness, greater tensile strength, and resistance to fatigue, impact, blast loading and abrasion. Fibers are added not only to improve the ductility of concrete but also, more importantly to control the cracking, by the bridging of the fibers across the cracks, which delay the propagation and widening of localized cracks. The use of glass fibers in SCC might bring together the advantages of both fibers and SCC. Glass Fiber Reinforced Self-Compacting Concrete (GFRSCC) combines the advantages of SCC in its fresh state and that of fibers in its hardened state. Because of the superior performance of SCC in its fresh state, addition of fibers will lead to a more uniform dispersion of fibers which is very critical for the performance of any fiber reinforced composite. Also the compactness of SCC matrix due to higher amount of finer particles may improve the interface zone properties and consequently the fiber-matrix bond leading to enhanced post-cracking toughness and energy absorption capacity S. No Properties Values

Biocomposite membranes of sodium alginate and silk fibroin fibers for biomedical applications

ABSTRACTBiocomposite membranes from biodegradable and biocompatible natural polymers were prepared from sodium alginate solution reinforced with silk fibroin fibers in several fiber content by casting and solvent evaporation. The properties of these biocomposites were investigated by scanning electron microscopy, swelling test, water vapor transmission, mechanical and thermal analyses, and cytotoxicity test. A biocomposite with uniform fiber dispersion and good fiber–matrix interaction was obtained through the incorporation of fibroin fibers in the alginate membrane, even though the fibers were used without any surface treatment to enhance the interfacial adhesion. The incorporation of fibroin fibers improved the tensile strength and also provided a new property to the alginate, that is, the resistance to tear. Moreover, the use of silk fibroin fibers in polymeric composites can result in a material with adequate characteristics for application in the biomaterial field, especially as wound dressings, because of its nontoxic effect to cells, flexibility, and resistance to tear. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3451–3457, 2013

Strain hardening fiber reinforced alkali-activated mortar – A feasibility study

The development of cementless slag-based alkali-activated mortar has previously been demonstrated. While greener than Portland cement based compositions, slag-based alkali-activated mortar tends to be highly brittle. In the present work, the feasibility of developing a new strain-hardening fiber reinforced composite using slag-based alkali-activated mortar reinforced by polyvinyl alcohol fiber is presented. In the development, three mixtures having a viscosity range that promotes uniform fiber dispersion were determined according to the types of alkali-activator and water to binder ratio. A series of experiments, including density, compression, uniaxial tension and panel bending tests were carried out to characterize the mechanical properties of the composite. Test results establish the feasibility of attaining tensile strain up to 4.7% in fiber reinforced alkali-activated slag composite, compared with 0.020% for the mortar matrix alone.

고인성 섬유보강 무시멘트 복합체의 기초 배합 및 역학 실험

지금까지 연구된 고인성 섬유 복합체의 주요 결합재는 시멘트이다. 이 연구의 목적은 시멘트를 전혀 사용하지 않은 고로슬래그 기반 알칼리 활성 모르타르와 PVA(polyvinyl alcohol) 섬유를 이용하여 고인성을 나타내는 복합체에 대한 가능성을 검토하는 것이다. 이를 위하여 알칼리 활성화제 종류에 따라 균일한 섬유 분산성을 확보하면서 섬유 혼합을 용이하게 하기 위한 적절한 모르타르의 유동성 및 점성을 갖는 두 가지 배합을 결정하였고, 복합체의 기본적인 성능을 평가하기 위하여 슬럼프 플로, 압축강도, 일축인장, 휨 실험을 수행하였다. 실험 결과 두 가지 배합의 슬럼프 플로는 평균 465 mm로 나타났고, 약 2% 정도의 인장 변형 성능과 다중 미세균열을 나타내는 것을 확인하였다. 이를 통하여 시멘트를 전혀 사용하지 않고도 변형률 경화 거동에 의한 고인성을 나타내는 섬유 복합체의 개발 가능성을 입증하였다.

EFFECT OF STEEL FIBER ON THE MECHANICAL PROPERTIES OF CEMENT-BASED COMPOSITES CONTAINING SILICA FUME

An experimental program was carried out to evaluate the mechanical properties of cement-based composites. Test variables included water to cementitious ratio, dosage of silica fume and volume fraction of steel fiber. Compressive strength test, direct tensile strength test, splitting tensile strength test, abrasion resistance test and drop weight test were performed and the results were analyzed statistically. According to the results of this study, the designed direct tensile testing method was a suitable method to estimate the tensile strength of fiber cement-based composites. Addition of fibers provided better performance for the cement-based composites, while silica fume in the composites would help obtaining uniform fiber dispersion in the matrix and improve strength and the bonding between fiber and matrix resulting from extra dense calciumsilicate-hydrate gel. The combination of steel fibers and silica fume can greatly increase the mechanical properties of cement-based composites. Besides, a multiple regression analysis was conducted to correlate compressive strength, direct tensile strength, abrasion coefficient and impact number with w/cm ratio, silica fume content and steel fiber content and a fairly agreement between test data and estimated values was found.