Fiber Cement Composites Research Articles

Tratamento de Fibras de Sisal com Lignosulfonato para Aprimoramento das Propriedades dos Compósitos de Fibrocimento

Tratamento de Fibras de Sisal com Lignosulfonato para Aprimoramento das Propriedades dos Compósitos de Fibrocimento

Record high thermoelectric performance of expanded graphite/carbon fiber cement composites enhanced by ionic liquid 1-butyl-3-methylimidazolium bromide for building energy harvesting

Record high thermoelectric performance of expanded graphite/carbon fiber cement composites enhanced by ionic liquid 1-butyl-3-methylimidazolium bromide.

Effects of Hybridized Synthetic Fibers on the Shear Properties of Cement Composites.

The use of fibers in cementitious composites yields numerous benefits due to their fiber-bridging capabilities in resisting cracks. Therefore, this study aimed to improve the shear-resisting capabilities of conventional concrete through the hybridization of multiple synthetic fibers, specifically on reinforced concrete structures in seismic-prone regions. For this study, 16 hybrid fiber-reinforced concretes (HyFRC) were developed from the different combinations of Ferro macro-synthetic fibers with the Ultra-Net, Super-Net, Econo-Net, and Nylo-Mono microfibers. These hybrids were tested under direct shear, resulting in improved shear strength of controlled specimens by Ferro-Ultra (32%), Ferro-Super (24%), Ferro-Econo (44%), and Ferro-Nylo (24%). Shear energy was further assessed to comprehend the effectiveness of the fiber interactions according to the mechanical properties, dosage, bonding power, manufactured material, and form of fibers. Conclusively, all fiber combinations used in this study produced positive synergistic effects under direct shear at large crack deformations.

Mechanical refining combined with chemical treatment for the processing of Bamboo fibres to produce efficient cement composites

The effects of chemical (30% sulphidity and 30% alkali active) and mechanical treatments (1500, 2000, 7500 and 10,000 revolutions for different refining and beating rates) on Guadua angustifolia Kunth (Bamboo) fibres are investigated for the first time. The morphological, chemical and physical changes of treated and untreated fibres after refining were characterised and analysed. The macro mechanical and structural properties at 7 and 28 days of curing of fibre-cement composites reinforced with treated fibres are evaluated. Fourier Transformed Infrared (FT-IR) and X-Ray Diffraction (XRD) spectra are performed to investigate structural compound changes. The MOR (Modulus of Rupture), fracture surface and Scanning Electron Microscopy (SEM) images were determined and analysed. The evaluation of manufactured cement composites showed that flexural strength increased by approximately 15% when composites were reinforced with alkali-treated fibres compared to untreated fibres. However, in the case of alkali fibres combined with mechanical refining, the increase reaches 57%. The specific energy (SE) of cement composites is not considerably different between untreated and alkali-treated fibres. Nevertheless, the combination of alkali with mechanical refining results in an increase in SE of more than 7 times. Although the combination of alkali treatment and mechanical refining improves the flexural strength and specific energy of cement composites, the high refining rates have a negative effect on these properties owing to an increase in the fibre fibrillation and a decrease in the swelling capacity, which reduce the fibre–matrix bonding.

TiO2 coated fiber cement composites: Effect of the load of TiO2 particles on photocatalytic degradation of H2S

This paper evaluated the effect of the amount of mass of the commercial photocatalyst Fotosan® (PC) based on TiO2 in the modification of the textural and morphological characteristics of the coatings formed in fiber cement supports (FB). The effect of mass addition on photocatalytic activity was also evaluated using the hydrogen sulfide degradation reaction (H2S) as a parameter. For this, five treatments conducted by different amounts of PC mass per area of FB in the range of 5.3 to 14.4 mg cm−2 were evaluated. The surfaces formed by these photocatalytic coatings (PCFB) were characterized by scanning electron microscopy with X-ray energy dispersive spectroscopy (SEM-EDS), X-ray diffractometry (XRD), nitrogen adsorption–desorption (BET) isotherms and infrared spectroscopy with total attenuated reflection (ATR-FTIR).The results of nitrogen isotherms confirmed that the coatings formed have a large specific pore volume (3.6×10-2 to 5.6×10-2 cm3 g−1) and a high specific surface area (18.9 to 29.9 m2 g−1). It was verified that the variation of PC mass over FB significantly affected the textural characteristics and the morphological structure of PCFB when comparing means between treatments (Tukey test; α = 5%), and probably these characteristics correlate with the respective photocatalytic activity. The modification of the structural properties produced by the accumulation of PC mass was more beneficial when the coatings were formed with a dosage of 7.3 mg cm−2, because it corresponded to the treatment where photocatalytic activity showed maximum intensity in the reaction of H2S degradation (72%) and a minimum amount of PC used in comparison to other treatments.

Effect of experimental wet and dry cycles on bamboo fibre reinforced acrylic polymer modified cement composites

Abstract This study experimentally evaluated the effect of accelerated wet/dry cycles on the dimensional stability and some selected mechanical properties of polymer modified vegetable fibre cement composites. The bamboo fibres were pre-treated with 10% conc. of sodium hydroxide and varied from 0 – 2.0% while acrylic polymer admixture of 10% w/w of cement was added to improve the properties. The modified fibre-cement composites were subjected to 50 cycles of wet/dry processes to simulate natural weathering process of the environment. The samples were subjected to water absorption, thickness swelling, modulus of rupture (MOR) and modulus of elasticity (MOE) after 28 days of curing and aging cycles respectively using 5 replicates. One way ANOVA at p<0.05 was used to analyse the results. Scanning electron microscope (SEM) and Fourier Transformer Infrared Spectroscopy (FTIR) analyses were conducted on the samples. The results showed improvement of 33.3, 64, 71 and 57% in MOR and 135, 85, 101 and 188% in MOE for samples with 0.5, 1, 1.5 and 2% fibre inclusion after ageing tests. Significantly improved dimensional stability values were observed in this study in comparison with data from similar ageing tests conducted on unmodified vegetable fibre-cement matrix. SEM micrographs showed marginal increase in the size of the pores before and after ageing tests. FTIR analysis indicated increase in intensities during the ageing tests especially for spectra bands located at 3384 – 3520cm−1 which are denoted for OH vibration stretching as well as 1676, 1726 and 1794 cm−1 which depict the presence of carbonyl groups because of absorption of polymers to the fibre surface during the ageing cycles. The study has shown thatwet/dry ageing cycles showed less harmful effect on vegetable fibre cement composites provided the cement matrix is modified with polymer admixtures.

Cement-based corrugated sheets reinforced with polypropylene fibres subjected to a high-performance curing method

This work proposes and evaluates a curing method based on the accelerated carbonation (AC) for cement-based corrugated sheets reinforced with polypropylene (PP) fibres produced by the Hatschek process. These corrugated sheets were experimentally evaluated in order to identify how the AC affects the fibre-cement composites. The obtained performance was compared with air-cured corrugated sheets reinforced with PP fibres and air-cured corrugated sheets reinforced with polyvinyl alcohol (PVA) fibres. The AC conferred a high carbonation degree (86%) increasing bulk density (13%) and decreasing apparent porosity (22%) and water absorption (28%) by means of calcium carbonate formation. The modulus of elasticity (10.7 GPa) and limit of proportionality (8.3 MPa) doubled in comparison with air-cured corrugated sheets. The Darcian (k1) and non-Darcian (k2) permeability coefficients were retrieved from the Forchheimer’s equation. The clogging of the permeable pores caused by the AC resulted in a reduction of 49% and 95% in k1 and k2, respectively. The drying shrinkage halved (1 mm/m) by the influence of AC which clogged pores with carbonates in the range 0.06–1.50 µm. Water-tightness test and its evaluation through digital image analysis showed a reduced moistened area in the AC cured corrugated sheets (22% lower) and enabled the identification of the cracks, which have a great influence on water tightness and permeability. The AC mitigated defects and conferred lower permeability and higher physical–mechanical performance in comparison to the air-cured PP and PVA reinforced corrugated sheets.

Optimizing the modified atmosphere parameters in the carbonation process for improved fiber-cement performance

The objective of this work was to evaluate the effect of the relative humidity on the accelerated carbonation process of the fiber-cement composites reinforced with a high concentration of vegetable fibers. The samples were produced with 10% of bleached eucalyptus pulp, in a method of fabrication similar to the commercial boards. The composites were submitted in an atmosphere with CO2 saturation, and relative humidity range of 60–90% to evaluate the effect of this parameter on the development of carbonation reaction. X-ray diffraction and thermogravimetric analysis were accomplished at different times, for monitoring the formation of carbonates along the accelerated carbonation process. Microstructure, physical and mechanical properties, and degradation were also evaluated. The composites carbonated with 60% of relative humidity presented a formation of CaCO3 significantly higher (37%) than the other concentrations of relative humidity (70, 80 and 90%) in just 4 h of carbonation. The densification of the cementitious matrix increased by 17%, and the modulus of rupture by 43% compared to non-carbonated composites. There was no statistically significant difference between the relative humidity of 60 and 70% for the physical and mechanical properties of the materials, and in general, the carbonation process preserved the reinforcement capacity of eucalyptus pulp in fiber-cement even after the accelerated aging cycles. In conclusion, this study demonstrated that the concentration of the relative humidity of the curing atmosphere is the main vehicle for diffusion and reactivity of the accelerated carbonation process. The use of the ideal relative humidity content can provide a faster and more effective carbonation reaction, in the production of fiber-cement materials.

The Acoustic Emission Method Implementation Proposition to Confirm the Presence and Assessment of Reinforcement Quality and Strength of Fiber-Cement Composites.

This article proposes to use the acoustic emission (AE) method to evaluate the degree of change in the mechanical parameters of fiber–cement boards. The research was undertaken after a literature review, due to the lack of a methodology that would allow nondestructive assessment of the strength of cement–fiber elements. The tests covered the components cut out from a popular type of board available on the construction market. The samples were subjected to environmental (soaking in water, cyclic freezing–thawing) and exceptional (burning with fire and exposure to high temperature) factors, and then to three-point bending strength tests. The adopted conditions correspond to the actual working environment of the boards. When applying the external load, AE signals were generated, which were then grouped into classes, and initially assigned to specific processes occurring in the material. The frequencies occurring over time for the tested samples were also analysed, and microscopic observations were made to confirm the suppositions based on the first part of the tests. Comparing the results obtained from a group of samples subjected to environmental and exceptional actions, significant differences were noted between them, which included the types of recorded signal class, the frequency of events, and the construction of the microstructure. The degradation of the structure, associated with damage to the fibers or their complete destruction, results in the generation under load of AE signals that indicate the uncontrolled development of scratches, and a decrease in the frequency of these events. According to the authors, the methodology used allows the control of cement–fiber boards in use. The registration and analysis of active processes under the effect of payloads makes it possible to distinguish mechanisms occurring inside the structure of the elements, and to formulate a quick response to the situation when the signals indicate a decrease in the strength of the boards.

BSE-based dispersion quantification of carbon fibres in cementitious composite through FCM-CA approach

Micro-engineered cementitious composite requires a quantitative evaluation of the phase dispersion state. In the application of the carbon fibre enhanced cementitious composite, the excellent electrical conductivity of the fibre network has been utilized for structural monitoring and internal heat generation. The dispersion state of carbon fibres significantly influences the performance of the functional application. However, it is challenging to evaluate the fibre dispersion with a quantitative consideration of the spatial arrangement. In this paper, an image-based approach is proposed to evaluate the spatial dispersion of carbon fibres in the cementitious composite. The independently programmed approach integrates fuzzy c-mean (FCM) clustering, random sequential addition simulation and originally developed cellular automata (CA). Quantification of fibre dispersion is performed with the nearest-neighbour analysis on the backscattered electron (BSE) images of the fibre-cement composite. Further investigation is conducted with the proposed approach, BSE images, electrical resistivity, compressive strength and flexural strength. Mechanical and chemical mixing techniques are applied during the sample preparation to investigate the dispersion behaviour in different systems. The evaluation results in a quantitative pattern of the dispersion coefficient within the range from 0.44 to 0.48. The dispersion and electrical resistivity results demonstrate that a well-distributed conductive network is formed with up to 6.5 min of mechanically controlled mixing. A negative correlation between the dispersion coefficient and the electrical resistivity is found in the form of the second-order power law. The microscale arrangement of fibre dispersion minorly influences compressive and flexural strength, but significantly influences the electrical function. Electrical evaluation of fibre dispersion confronts inconsistency in the chemical mixing system.

Comparative study of hybrid fiber cementitious composites

Different types of fibers impart specific characteristics to concrete, including crack bridging, early age crack resistance, ductility, toughness, strength, and loss of workability. It seems that if these fibers are combined, then specific characteristics of each fiber may be imparted to concrete and the desired characteristics of the concrete composite may be achieved. Thus, this investigation has been conducted to study the properties of concrete composites composed of four different types of fibers used singly or in hybrid form. The effectiveness of hybrid fibers in cementitious composites to achieve better characteristics; strengths, toughness, workability, and cost, was investigated and compared. Composites made of carbon fiber, plain steel fiber, polypropylene fiber, and glass fiber and their hybrid combinations (2, 3 and 4 fibers mixed), at constant volume of fiber 1.25%, along 4% styrene-butadiene rubber latex and 1.5% superplasticizer, are prepared and tested. The composites are compared and investigated for their feasibility in terms of their properties and cost. The comparison showed the suitability of some bi-hybrid composites, and incompatibility of tri-hybrid and tetra-hybrid composites in terms of effectiveness and feasibility.

Modeling microfracture evolution in heterogeneous composites: A coupled cohesive phase-field model

Modeling micro-crack evolution in highly heterogeneous solids has been a major challenge in brittle materials owing to their complex microstructures and the complicated interactions between their components. The present work aims to address this challenging task through the development of a novel coupled cohesive phase-field model that can accurately predict the evolution of microfracture and describe interfacial de-bonding in quasi-brittle composites. As a crucial part of our modeling framework, the interface is described by an auxiliary interface variable, thus the interface properties can be regularized. The developed model has the following novelties: (1) the coupled cohesive phase field method is accomplished by implementing a gradient damage formulation to predict crack nucleation and propagation in quasi-brittle solids; (2) the interface properties in complex heterogeneities are regularized by the interaction between matrix and inclusions properties, as well as the width of the interface; and (3) it can precisely predict the crack evolution (crack initiation, propagation, deflection into the matrix) in quasi-brittle heterogeneous solids. Particularly, the proposed model is validated using our implemented experimental results, from which the micro-crack trajectories in fiber-cement composites were observed. The proposed approach shows great potentials in predicting the fiber de-bonding as well as the micro-crack kinking path in complicated quasi-brittle materials.

Feasibility Study of Using Modified Recycled Fiber-Cement for the Production of High Performance Fiber-Cement Composites

The aim of this work is to study the feasibility of recycling the rejected fiber-cement composites as the filler in the fiber-cement mixture for producing the new fiber-cement composites. The rejected fiber-cement composites were ground and mixed with ordinary Portland cement (OPC), sand, cellulose fiber, and the dissolving agent which was a chemical prepared from the proprietary blend of citric acid together with thickening and wetting agent. The samples (75 mm × 200 mm × 7 mm) were prepared by mixing the raw materials, including 34.25 wt% OPC, 30 wt% sand, 5.5 wt% cellulose fiber, and 30.25 wt% recycled fiber-cement composites. Then, the dissolving agent was added in the amount of 0 to 4.5 % of the OPC weight in the mixture. The mixtures of raw materials were mixed with water to form the slurry. Then, the green samples were produced by the filter pressing method. After molding, the green samples were autoclaved at pressure 10 bars and temperature 180 °C for 16 hrs. After that, the microstructure of the autoclaved samples was examined by scanning electron microscope (SEM). The modulus of rupture (MOR) and modulus of elasticity (MOE) of the samples were measured by universal testing machine (UTM) based on ASTM C1186-08 standard. The results showed that properties of the samples passed the requirements of the industrial standard. In addition, the utilization of dissolving agent affects both the microstructure and the properties of the samples.

Optical fibers in cementitious composites (LTCM): Analysis and discussion of their influence when randomly arranged

Published studies related to LTCMs (light-transmitting cement-based materials) deserve attention. Although it is a widely used commercial material, in the technical-scientific field, there is still a demand for a deeper understanding of its performance characteristics. The data presented here refer to samples with three different fiber contents (2%, 3.5%, and 5%) that were arranged randomly and compared to the reference samples that were free of polymeric optical fiber (0% POF). This work complements a related article that was previously published by the authors [1] that addresses the influence of fibers that are arranged in an orderly manner. The performance characteristics of the compressive strength, the flexural tensile strength, the water absorption via capillarity, the light transmittance, and the cost-benefit ratio (considering the Brazilian market) were verified. From the 0% (reference) to 5% (maximum POF content adopted) fiber contents, the following behaviors were found: decreases of approximately 20% and 30% in the compressive and flexural tensile strength, respectively, and an increase of 400% in the capillary water absorption. For light transmittance, from the 2% to the 5% POF contents, there was an increase of 150% in the fibers and an increase of approximately 300% in the light transmittance. Considering the Brazilian market and the cost per lux ($ / lux) of the samples with added optical fibers (2%, 3.5% and 5% POF), the following values were obtained: $ 1.61/ lux (2% POF), $ 4.19/lux (3.5% POF), and $ 1.26/lux (5% POF). Based on the cost/light transmittance ratio, the 5% POF content was the best.

Reducing water absorption of fiber-cement composites for exterior applications by crystal modification method

The aim of this work was to reduce the water absorption of the fiber-cement composites, which is also known as fiber-cement products, by the crystal modification of cement matrix using the additives including polyurethane-based corn starch–lithium perchlorate (LiClO4), and acrylic resin emulsion-based chitosan-silicate hybrid compound. To prepare the samples, the mixtures consisting Portland cement Type I, sand, cellulose fibers from pine trees, gypsum, and additive were mixed with water. The percentages of additive in the mixtures before mixing with water were 0.03 to 0.17 wt%. The green sheets of samples were formed by filter-pressing method, air cured for 1 day, and then autoclaved at 8 bars and 140°C for 12 h. The experimental results indicated that the water absorption of the samples was reduced when polyurethane-based corn starch–lithium perchlorate (LiClO4) was used as the additive due to the crystallization of the small crystals within cement matrix, while their mechanical properties including modulus of rupture (MOR) and modulus of elasticity (MOE) of the samples using this additive conform industrial standard.

Strain sensitivity of steel-fiber-reinforced industrial smart concrete

Self-sensing cementitious composites can enable structures that are capable of carrying the loads applied on them while monitoring their condition. Most of earlier research has focused on the incorporation of nanofillers or microfibers into cement paste or mortar composites. However, there have been very limited number of studies on the development of steel-fiber-reinforced cementitious composites with self-sensing capabilities. This study explores strain sensitivity of concrete mixtures that include coarse aggregates up to 15 mm diameter and steel fibers with a length of 13 mm and a diameter of 0.25 mm. Five different concrete mixtures with steel fibers at 0%, 0.2%, 0.35%, 0.5%, and 0.8% volume ratios were fabricated. Compression tests with simultaneous measurement of strain and electrical resistance were conducted on the cubic specimens. Gauge factor and percent linearity that is a measure of error in strain sensing were calculated. Concrete mixtures with 0.5% steel fibers possess a strong linear relationship between applied strain and electrical resistance change with a gauge factor over 20 times larger than that of traditional metal strain gauges. Phenomenological models for different resistivity and gauge factors of cement paste/mortar with respect to concrete with large aggregates and short–long fiber cement composites were presented.

Rendering Mortars Reinforced with Natural Sheep's Wool Fibers.

The susceptibility of rendering mortars to cracking is a complex phenomenon. Fibers have been incorporated in mortars to ensure the durability of the render and can improve the flexural strength, fracture toughness, and impact resistance of the mortars. Aside from the better cracking performance of fiber reinforced mortars, natural fibers have been a path to reducing the environmental impacts of construction materials. Recycling has high sustainability-related potential as it can both mitigate the amount of waste being inadequately disposed and reduce the consumption of natural raw materials. Studies on the incorporation of waste in civil engineering materials have been growing, and recycled fibers may be feasible to incorporate in mortars. Natural fibers are considered as a viable replacement for synthetic ones. Several studies have investigated vegetal fibers in cementitious composites. However, only a few have focused on the incorporation of waste animal-based fiber. The aim of this work is to analyze the feasibility of the use of natural sheep’s wool fibers on the reinforcement of mortars and in particular to improve their cracking behavior. For this purpose, two different binders were used: cement and cement-lime mortars were produced. The incorporation of 10% and 20% (in volume) of 1.5 cm and 3.0 cm wool fibers was analyzed. The results show that the incorporation of wool fibers increased the ductility of the mortars and improved their mechanical properties.

Fiber-cement composites hydrated with carbonated water: Effect on physical-mechanical properties

The proposal presented here is to use accelerated carbonation via carbonated water to modify the microstructure of the cementitious matrix. Carbonated water was tested in different conditions of molding and curing of the fiber-cement composites. This particular carbonation process generates stabilization of the pore volume of the composite and reduced the degradation of the cellulosic fibers by the consumption of CH and formation of the CaCO3 in early age. The results indicated that carbonated water was suitable for improving hydration, and as a carbonating agent in the fiber-cement composites. The curing carbonation yielded substantial mechanical and physical gains, as well as further protection of the cellulosic fibers against mineralization into the cement.

PP および PVA 繊維補強セメント複合材料の動的一軸圧縮特性に関する実験的研究

PP および PVA 繊維補強セメント複合材料の動的一軸圧縮特性に関する実験的研究

Is wollastonite capable of improving the properties of wood fiber-cement composite?

Effects of wollastonite substitution were investigated relative to the mechanical, physical, and microstructural properties of a wood fiber-cement composite. Wollastonite content of 0%, 3%, 6%, and 9% and lignocellulosic material (kraft fibers) content of 10%, 20%, and 30% were used based on the dry weight of cement. Then the lignocellulosic material and the resulting board samples were compared to a control (without wollastonite). Modulus of rupture (MOR), modulus of elasticity (MOE), water absorption, and fire resistance tests were conducted to examine the characteristics of the board composite. The results showed that the mechanical properties of wood fiber-cement composite were improved by the 9% wollastonite substitution. The fire-resistance of the composite board was improved when the wollastonite content was increased. Furthermore, cement boards with 9% wollastonite exhibited lower water absorption in comparison to the other specimens. Scanning electron microscopy (SEM) results showed that the calcium hydroxide formed hydrated calcium silicate gel (C-S-H gel) after the addition of wollastonite. The SEM images showed that the micro-structure of the boards were improved by increasing the nano-wollastonite content.