Fiber Cement Composites Research Articles

A Review of the Use of Natural Fibers in Cement Composites: Concepts, Applications and Brazilian History.

The use of natural lignocellulosic fibers has become popular all over the world, as they are abundant, low-cost materials that favor a series of technological properties when used in cementitious composites. Due to its climate and geographic characteristics, Brazil has an abundant variety of natural fibers that have great potential for use in civil construction. The objective of this work is to present the main concepts about lignocellulosic fibers in cementitious composites, highlighting the innovation and advances in this topic in relation to countries such as Brazil, which has a worldwide prominence in the production of natural fibers. For this, some common characteristics of lignocellulosic fibers will be observed, such as their source, their proportion of natural polymers (biological structure of the fiber), their density and other mechanical characteristics. This information is compared with the mechanical characteristics of synthetic fibers to analyze the performance of composites reinforced with both types of fibers. Despite being inferior in tensile and flexural strength, composites made from vegetable fibers have an advantage in relation to their low density. The interface between the fiber and the composite matrix is what will define the final characteristics of the composite material. Due to this, different fibers (reinforcement materials) were analyzed in the literature in order to observe their characteristics in cementitious composites. Finally, the different surface treatments through which the fibers undergo will determine the fiber–matrix interface and the final characteristics of the cementitious composite.

Mechanical Investigation on Fiber-Doped Cementitious Materials.

Cementitious materials can be reinforced by adding different fibers. However, the effect of different fiber reinforcements on the mechanical properties of cement-based materials remains to be further studied. This paper studies the influencing factors of different fiber cement-based materials by combining experimental and theoretical methods. The tests used carbon fiber, glass fiber, and polyvinyl alcohol (PVA) fiber-reinforced cement-based materials. The addition ratios of fibers are 0%, 0.5%, and 1% by volume respectively. The compressive strength, bending strength, and drying shrinkage are studied for 3 to 28 d. The relationship between bending strength, compressive strength, dosage, and shrinkage is analyzed. The test results show that carbon fiber cement-based materials’ bending, and compressive strength increase the fastest, followed by glass and PVA fibers. The presented mathematical model accurately predicted the strength of the three fiber cement-based materials at different curing times. Compared to glass fiber and PVA fiber, carbon fiber shrinks less. It can be shown that the fiber significantly affects the early strength change of the fiber cement-based material by changing the shrinkage size of the fiber-cement-based material. The bending strength of carbon fiber, glass fiber, and PVA fiber increases with the increase of fiber volume fraction. On the other hand, the compressive strength increases and then decreases. Mechanical tests show that carbon fiber has the best reinforcement effect. The number of fibers, center spacing, and ultimate tensile length are all important factors that affect the strength of different fiber cement-based materials. Moreover, applied ABAQUS software established compression and bending finite element models of fiber-cement composites. It can predict the mechanical performance concerning fiber cement-based materials’ different types and volume fractions.

Effect of fiber type and content on the performance of extruded wood fiber cement products

This study presents the physical, mechanical, and durability characteristics of the extruded cement fiber products manufactured with various types of wood fibers. Four types of wood fiber cement products, one each produced with softwood, hardwood, recycled wood, and a blend of hard/softwood fibers were investigated in the experimental program. For each type of fiber mixtures, the effect of fiber content (fiber to cement ratio) was investigated at 5%, 10%, and 15% levels. These products were tested in unaged and aged conditions after exposure to accelerated aging effects. Test results showed decrease in bulk specific gravity and increase in water absorption capacity of the wood fiber cement composites with increase in fiber content. Considerable increase in flexural toughness was recorded with increase in fiber content for the softwood fiber products. After exposure to accelerated aging conditions comprising of freeze-thaw cycles, wet-dry cycles, saturation, and warm water exposure, the softwood fibers-based cement composite provided the highest level of flexural strength and stiffness. Furthermore, fiber cement composites having 10% fiber content retained a target flexural strength of 8–10 MPa besides showing good flexural stiffness after aging. Test results of this study help in identifying wood fiber reinforcement conditions which yield extruded fiber cement products with the balance of physical, mechanical, and durability characteristics suiting different building applications.

Impact of nanosilica deposited on cellulose pulp fibers surface on hydration and fiber-cement compressive strength

The present study investigated the effect of incorporating different contents of modified and unmodified cellulose pulp fibers on the mechanical, physical and mineralogical properties of fiber-cement composites. The cellulose pulp fibers were modified using the sol–gel process, which resulted in the deposition of nanosilica on their surface. The raw materials used to form the composites included: Portland cement, calcium carbonate, additives and cellulose pulp fibers. Two types of fibers (modified and unmodified) and five fiber contents (1%, 3%, 5%, 7% and 9%) were evaluated. The results revealed that the presence of nanosilica on the surface of the fibers of the modified cellulose pulp increased the resistance to axial compression and decreased the density of the fiber-cement composites, although such properties have been reduced proportionally with the increase of fiber content. Nanosilica increased interaction of the fibers with the cement matrix hydrates, decreasing the presence of calcium hydroxide and increasing the presence of calcium silicate hydrates. The interacting influence of the decrease of hydrophilicity, increase of surface area and roughness of the modified fibers allowed a better fiber/matrix interaction and fiber-cement performance. Further studies are necessary to realize which of the aforementioned factors is dominant for the fiber-cement performance. Modification of the pulp fibers with nanosilica are presented as potential fiber treatment to be used in the production of cement reinforced composites.

Investigation on Fracture Behavior of Cementitious Composites Reinforced with Aligned Hooked-End Steel Fibers

Aligning steel fibers is an effective way to improve the mechanical properties of steel fiber cementitious composites (SFRC). In this study, the magnetic field method was used to prepare the aligned hooked-end steel fiber cementitious composites (ASFRC) and the fracture behavior was investigated. In order to achieve the alignment of steel fibers, the key parameters including the rheology of the mixture and magnetic induction of electromagnetic field were theoretically analyzed. The results showed that, compared with SFRC, the cracking load and the ultimate load of ASFRC were increased about 24–55% and 51–86%, respectively, depending on the fiber addition content. In addition, the flexural tensile strength and residual flexural strength of ASFRC were found to increase up to 105% and 100%, respectively. The orientation of steel fibers also has a significant effect on energy consumption. The fracture energy of ASFRC was 56–70% greater than SFRC and the reinforcement effect of hooked-end steel fiber was higher than straight steel fiber. The fibers in the fracture surface showed that not only was the number of fibers of ASFRC higher than that of SFRC, but also the orientation efficiency factor of ASFRC was superior to SFRC, which explains the improvement of fracture behavior of ASFRC.

Effects of Load Level, Dimensional Effects and Temperature Conditions on the Pressure Sensitivity of Short Carbon Fiber Cementitious Composites

Effects of Load Level, Dimensional Effects and Temperature Conditions on the Pressure Sensitivity of Short Carbon Fiber Cementitious Composites

Research on the mechanical properties of the joint of the beam-column subassembly

In order to study the effect of high-performance fiber cement composites (HPFRCC) on the mechanical properties of the joint of the frame structure, pseudo-static tests were conducted on seven beam-column subassemblies. Compared with the RC subassembly, the shear capacity of the HPFRCC beam-column connection was increased by 11.4%, and the shear deformation was reduced by 10.3%. The contribution ratio of the shear deformation to the drift was reduced by 22.7%. The value of the coefficient ηc and the flange width of the slab had a significant impact on the shear deformation of the HPFRCC joint. The shear deformation corresponding to the peak load of the joint can be controlled at about 0.01 when the coefficient ηc is 1.6, or the flange width is eight times the width of the slab thickness. The shear strength-shear deformation calculation model of the joint was established through the Bayesian parameter estimation, and the model analysis results were in good agreement with the test results.

A comprehensive overview of jute fiber reinforced cementitious composites

Natural fibers are eco-friendly, cost-effective, lightweight, renewable, have better thermal properties and corrosion resistance capabilities. The addition of natural fibers in cementitious composites (CCs) will be a sustainable step to enhance their mechanical properties as well as encouraging green construction. Jute fibers are cheap among all the natural fibers and are abundantly available in several developing countries. This study describes the impact of utilizing jute fibers in CCs for sustainable construction. The influence of jute fiber on the mechanical strength of CCs is reported, including compressive strength, split tensile strength, flexural strength. Additionally, the microstructure of jute fiber is discussed, and jute fiber-matrix interaction is explained. The effect of varying jute fiber length and content on the mechanical strength of CCs has been described, and optimum jute fiber length and content have been reported. The current research initiative expects to promote understanding of the concerns and difficulties encountered during the production of jute fiber reinforced CCs. It was concluded that incorporating jute fibers can enhance the strength properties of CCs if used in shorter lengths and lower volume contents, while higher volume content of jute fibers degraded the strength properties of CCs. In addition, the current research is quite limited in terms of practical applications of jute fiber reinforced CCs, and more research is needed in the future to determine their applications in civil engineering construction. Future research has been recommended in light of the different parameters discussed in this study. Moreover, this review will be helpful in promoting the use of jute fiber for the green construction of CCs.

Influence of the fiber treatment and matrix modification on the durability of eucalyptus fiber reinforced composites

It is well known that the most important issue of cement-based composites is the durability of the natural fibers. The present study evaluates the effect of activated coal mining residues on the physical-mechanical properties of fiber cement composites reinforced by thermally treated eucalyptus pulp, before and after accelerated aging. The results showed that the partial substitution of cement by activated coal mining residues and the use of thermally treated fibers contribute to the improvement of the mechanical properties of the composites. Indeed, an increase of the values of the modulus of rupture (MOR) and the specific energy (SE) of the composites is observed under four-point bending flexural tests. Moreover, after accelerated aging tests, both fiber treatment and matrix modification contribute to mitigate the degradation of the fibers and increase the mechanical properties of the composites. According to the results of the study, the use of activated coal mining residues as partial substitution of cement and hornification treatment of the pulp, can lead to the improvement of the mechanical performance and durability of fiber cement composites.

Influence of short-term degradation on coir in natural fibre-cement composites

Natural fibres are regarded as a potential bio-based alternative to traditional fibre material used in cement-based composites. A well-known complication of natural fibres is their instability the alkaline cement environment, which causes degradation. This work presents a study of mechanical performance, microstructure, and composition of coir fibres exposed to alkalinity, focusing on short-term degradation mechanisms of degradation. Fibre performance was found to be unrelated to the alkalinity of the medium and only hemicellulose was found to readily degrade in a highly alkaline environment. It was therefore concluded that alkaline hydrolysis is not the main factor involved in natural fibre degradation.

Use of natural vegetable fibers in cementitious composites: concepts and applications

Use of natural vegetable fibers in cementitious composites: concepts and applications

Elastic properties of cement-based composites reinforced by nano-tailored hybrid fiber

The elastic properties of cementitious composites reinforced by nano-tailored hybrid fibers are analyzed using a micromechanical method. The microstructural feature of the hybrid fiber is that uniformly aligned carbon nanotubes (CNTs) are grown radially on the circumferential surface of carbon fibers (CFs). The CNT waviness and CNT/cement interfacial region are considered. The predictions are compared with experiments, which guarantee the validity of the model. The mechanical properties of cementitious composites, especially in transverse direction, are enhanced due to the radial growth of CNTs on the CFs. The CNT/cement interfacial zone may have a significant effect on the elastic behavior of the nano-tailored hybrid fiber-cement composites. As the mechanical properties of interphase are higher than those of the cement matrix, increasing the interphase thickness causes an improvement in the elastic and shear moduli. The CNT non-straight shape decreases the transverse elastic modulus.

Investigation of mechanical properties of high-performance hybrid fiber concretes adding nanomaterials using with coarse aggregate

High-performance hybrid fiber cement composites have more ductility and higher strength than traditional concrete. This is because crack development is limited due to multiple small cracks are formed instead of a single large crack as the fibers enter the matrix. It is customary to produce these concrete composites with fine aggregates. In this study, concrete composites with coarse aggregates were strived to be produced to gain some feasibility. To this end, different mixtures composed of different aggregate/binder ratios and different fly ash/binder ratios were designed. In order to compare the effectiveness of the combination of different fibers were utilized in these mixtures. The volumetric ratios of fibers (excluding reference samples) were kept constant at a value of 2%. For each mixture, four-point bending and compressive tests were performed. The increase in the aggregate ratio was observed to cause a more ductile flexural behavior in mixtures composed of PVA and steel fibers. In contrast, the ductility was reduced in mixtures with Nylon-mono and steel fibers. In addition, the ductility values were enhanced with the increase in FA/PC ratio. In addition, the possibility to use the cheaper Nylon-mono fibers in hybrid fiber mixtures was proved with optimization of aggregate-binder (A/B) and FA/PC ratios, enabling more feasible high-performance concrete mixtures.

Effect of Fiber Content and Alignment on the Mechanical Properties of 3D Printing Cementitious Composites.

This paper studies aligned glass fiber-reinforced composites for printing. To determine the influence of fiber content and alignment on the mechanical properties of this novel material, a large number of standard test specimens were prepared, which included samples fabricated by mold-casting, randomly dispersed fiber reinforced mixtures and aligned fiber cement composites containing 10 types of fiber volume ratios manufactured by nozzle sizes ranging of 24 and 10 mm (fiber length = 12 mm). Mechanical properties and failure modes of the specimens under compression and flexural tests were studied experimentally. The anisotropic behaviors of printed samples were analyzed by different loading directions. As a result, the compressive and flexural strength of printed samples showed obvious anisotropy. With the increase of fiber volume ratio, flexural strength of the fiber reinforced composite was elevated tremendously but its compression strength reduced slightly. Moreover, fiber alignment also had a significant influence on the mechanical properties of the fiber reinforced composite. The composite cement-based material with 1 vol.-% aligned fiber exhibited an excellent flexural strength of 9.38 MPa, which increased by 483% in comparison to that of the plain cement paste.

Impact of operating conditions on the strength and frequency of destruction of fibre-cement composites

Impact of operating conditions on the strength and frequency of destruction of fibre-cement composites

Flexural behavior of sandwich panels combining curauá fiber-reinforced composite layers and autoclaved aerated concrete core

The mechanical response of sandwich panels with two layers of curauá fiber cement composites and a core layer of autoclaved aerated concrete (AAC) was investigated. Each layer consisted of long unidirectional curauá fibers and a cementitious matrix. For durability purposes, 50% of the Portland cement was replaced with pozzolanic materials to reduce the content of calcium hydroxide in the matrix. The performance of sandwich panels with 350 mm × 60 mm × 90 mm (length × width × thickness) was evaluated through monotonic and cyclic four-point bending tests to obtain the load–deflection response, flexural strength, and toughness. Monotonic bending tests were performed on each component of the panels – i.e., composites and AAC blocks. Pull-off tests were performed to evaluate the adhesion between the skin layers and the core, while optical and scanning electron microscopes were used to observe the interface's topography. The results revealed the externally bonded layers' efficiency, which provided a higher deflection capacity to the material and increased its flexural strength. The AAC blocks revealed a more ductile response when assisted by the composite layers in the sandwich structure. Under cyclic bending test conditions, the sandwich panels exhibited a satisfactory post-peak ductility so that the energy was not abruptly lost but gradually released throughout its deflection-softening behavior.

Valorization of Jute Biomass: Performance of Fiber–Cement Composites Extruded with Hybrid Reinforcement (Fibers and Nanofibrils)

In this study, the characteristics of jute fibers and cellulose nanofibrils (CNFs) and their impacts on mechanical strength were compared, particularly from the standpoint of their application as reinforcement in extruded fiber–cement composites. Raw jute fibers were subjected to an alkaline treatment before being fibrillated into CNFs. The fiber–cement composites were produced with jute fibers (0.5% and 2%) and CNFs (0.5% and 2%) via extrusion process. Both percentages of reinforcement were based on the cement mass. In addition, hybrid composites with a mixture of fibers and CNFs were produced. Hydroxypropyl methylcellulose and carboxylic polyether were used as additives to improve the mixture’s rheology. The composites were subjected to natural weathering for 5 months before being analyzed for their physical and mechanical properties. CNFs and jute fibers subjected to NaOH treatment presented a higher initial degradation temperature (Tonset). The apparent porosity decreased for all compositions studied, reaching a 75% reduction for the sample reinforced with 2% CNFs. Fiber–cement with a hybrid reinforcement of 1.5% CNFs + 0.5% fibers exhibited the strongest mechanical performance. All compositions showed a decrease in the modulus of elasticity after natural weathering. In contrast, the modulus of rupture and the limit of proportionality showed an average gain of 1 MPa for fiber–cement composites produced with hybrid reinforcements. The better mechanical performance of the hybrid formulations may be owing to the synergistic work of the fibers and CNFs, suggesting the potential of cellulose CNFs for use as reinforcement in cement-based composites.

CEMENT COMPOSITES REINFORCED WITH TEOS-TREATED WOOD FIBRES

In this study, wood fibres were extracted from eucalyptus and pine woods, treated by immersion in tetraethyl orthosilicate (TEOS) and incorporated into a cementitious matrix at three weight contents (2 wt%, 5 wt% and 10 wt%). The fibres were characterized using chemical and morphological analyses and the cement-based composites were evaluated using chemical, hygroscopic, mechanical and morphological tests. The morphological and spectroscopic results satisfactorily justified the physical-mechanical properties. The wood fibre-cement composites reached similar water uptake and apparent porosity to those of the neat mortar, but exhibited higher mechanical properties. Furthermore, all treated fibres yielded composites with improved mechanical and hygroscopic properties compared to those with pristine fibres. Overall, the best performance (based on hygroscopic and mechanical results) was obtained for the wood fibre-cement composite with 2 wt% pine fibres.

Evaluating Self-sensing Property of Carbon Fibre Cement Composite by experimental study and Finite Element Modelling For Structural Health Monitoring Applications

Structural health monitoring (SHM) is a novel area of research and it is the process of implementing a damage detection strategy. The initial step of implementation a SHM system involves, incorporating structural self-sensing capability of material to achieve the reliability and possesses long term stability. Smart sensing technologies involves the applications of fiber optic sensors and self-diagnosing fiber reinforced composites which possess important capabilities of monitoring various physical or chemical parameters to achieve the durable service life of structures. The addition Carbon fiber to concrete composites possess the electric properties, therefore it can be used as Smart sensing composite that provide the capability of non-destructive flaw detection in structures. In this paper, carbon fiber (CF’s) is added to cement composite to attain piezoresistive properties of composite. This carbon fiber is added in the composite by forming tube which act as conductive element. Later on, electromechanical test is conducted to this sensor by embedded into structural elements that is in beam and column to evaluate self-sensing properties. Scanning electron microscope is carried to understand the morphology of sample. A Finite elemental modeling is done to validate this experimental result. A FEA modelling is carried out using ANSYS software, subjected to steady steady static loading and electric analysis were done. Form the experimental is observed that addition carbon fiber induces conductivity property and the resistance decrease for failure load. The resistivity from experimental study observed is 9.2 kilo ohms and 11.2 kilo ohms for embedded carbon fibre sensor into beam and column respectively. The percentage error in electrical analysis of experimental tests compared with analytical modelling, found to be 15 %. Based on these results it can be concluded that carbon fiber cement composites have great potential and they can be used for structural health monitoring applications.

Treatment of date palm fibres mesh: Influence on the rheological and mechanical properties of fibre-cement composites

An experimental study was conducted on the influence of different treatments of date palm fibres on the properties of mortars in both fresh and hardened states. Three types of treatment were discussed: boiling water treatment, sodium hydroxide treatment and a polymer surface treatment based on linseed oil. As a first step, tests of water absorption, setting times and direct tensile strength were performed on single fibres to assess the relevance of the predominant parameter for each treatment. Thereafter, unreinforced mortar and mortars reinforced with raw and treated date palm fibres were made and tested using a flow table test, as well as for porosity accessible to water, three-point bending strength, compressive strength and capillary water absorption. The results for individual fibres show that treatments with a 3-hour boiling of the fibres, a 3% NaOH concentration, and a 1.5% linseed oil/fibre ratio yield the lowest absorption kinetics, the shortest setting times, and the most interesting tensile properties. However, the results for fibrous composites indicate that the workability of mortars reinforced with linseed oil treated fibres was improved compared with raw fibres. In the hardened state, boiling and sodium hydroxide treatments improve the flexural strength of the composites. The same trend was observed for compressive strength. Therefore, the mortar reinforced by fibre treated with linseed oil does not improve the strength and is the most porous. The incorporation of date palm fibres decreases the kinetics of the capillary absorption of mortars compared to unreinforced mortar. The lowest absorption coefficients are obtained after the treatment with linseed oil.