Fiber Cement Composites Research Articles

Carbonation is affecting biodegradability testing of fiber cement composites

Fiber cement composites (FCCs) containing natural cellulosic fibres are emerging materials in the building industry. At the end of life, FCCs are often disposed of as part of the C&DW in a landfill. The production of landfill gasses in landfills needs to be kept as low as possible. Generally, leaching of total dissolved organic carbon (DOC) is used as a proxy for the biodegradability of a waste material and the subsequent production of landfill gasses, and is, therefore, used to evaluate biodegradability of waste. In this study, FCC samples with varying average diameter and varying age were subjected to both a batch leaching test (determine DOC leaching) and to a standardized biodegradability test. The batch leaching showed that the DOC leaching ranged between 520 and 1300 mg kg−1 for the tested samples, and that leaching of DOC decreases with increasing particle diameter and with increasing effects of ageing. Yet, the biodegradability results indicated that the leaching of DOC from FCCs does not result in the release of landfill gasses. This study hypothises that the DOC that leaches from the FCCs is being degraded to CO2, but that the formed CO2 is immediately captured by the material itself through the process of carbonation. An inpermeable layer is formed around the material that stops further leaching of DOC. The results of this study therefore suggest that leaching of DOC is a poor indicator for the biodegradability of FCCs.

Reinforcing Efficiency of Micro and Macro Continuous Polypropylene Fibers in Cementitious Composites

The effect of the microstructure of hydrophilic polypropylene (PP) fibers in the distribution of cracking associated with the strengthening and toughening mechanism of cement-based composites under tensile loading was studied. Using a filament winding system, continuous cement-based PP fiber composites were manufactured. The automated manufacturing system allows alignment of the fiber yarns in the longitudinal direction at various fiber contents. Composites with surface-modified hydrophilic macro-synthetic continuous polypropylene fibers and monofilament yarns with different diameters and surface structures were used. Samples were characterized using the tensile first cracking strength, post-crack stiffness, ultimate strength, and strain capacity. A range of volume fractions of 1–4% by volume of fibers was used, resulting in tensile first cracking strength in the range of 1–7 MPa, an ultimate strength of up to 22 MPa, and a strain capacity of 6%. The reinforcing efficiency based on crack spacing and width was documented as a function of the applied strain using digital image correlation (DIC). Quantitative analysis of crack width and spacing showed the sequential formation and gradual intermittent opening of several active and passive cracks as the key parameters in the toughening mechanism. Results are correlated with the tensile response and stiffness degradation. The mechanical properties, as well as crack spacing and composite stiffness, were significantly affected by the microstructure and dosage of continuous fibers.

Influence of the initial moisture content on the carbonation degree and performance of fiber-cement composites

Abstract The objective of this work is to show the effect of the initial moisture content of fiber-cement composites on their carbonation degree (CD), mechanical and physical properties after their exposition to CO2 atmosphere, and after accelerated ageing cycles. Fiber-cement composites produced by Hatschek process and submitted to carbonation at early age for 10 h of exposition to 15% of CO2. Part of the composites was previously submitted to different drying times (20, 40, 60 and 120 min). The CD was determined using thermogravimetric measurements. Mechanical (flexural) and physical properties were determined at 10 days of cure and after 200 soak and dry ageing cycles. As expected, as higher as the time of drying, the higher was the removing of moisture from the composites. Accelerated carbonation caused the decrease of Aft, C-S-H, Afm and Ca(OH)2; and increased the content of CaCO3. The higher time of drying (120 min) led to the lower content of Ca(OH)2 and the higher content of CaCO3. Fiber-cement composites without drying and with 40 min of drying presented moisture between 19% and 21% and led to average CD between 28 and 39%; while those fiber-cements dried for 120 min (14% of moisture) presented an average CD of 44%. Higher CDs led to the significant decrease of water absorption (WA) and apparent porosity (AP) of the composites, while caused the increase of bulk density (BD) of the fiber-cement composites. LOP and MOE values increased with carbonation, while they were less affected by the previous drying before carbonation. 200 ageing cycles caused increase of LOP, MOR, MOE and BD of all the composites, while decreased toughness, WA and AP. Therefore, the control of the initial moisture and free pores of the fiber-cement composites seems to be a strategy to improve the efficiency of the accelerated carbonation of fiber-cement composites.

Adjusting curing parameters for innovative and durable vegetable fibre-cement composites

This work adjusts curing parameters for innovative and durable vegetable fibre-cement composites produced by a slurry vacuum dewatering process. The raw materials used for the cementitious composite mix designs applied in this investigation include: Portland cement, ground silica as an inert filler and vegetable fibre reinforcement. The curing conditions were conducted on eight sets of samples studying the effects of: initial hydration duration (10 h or 24 h); accelerated carbonation exposure (0.035% or 20% of CO2 concentration); and accelerated aging tests (before and after 200 soak & dry cycles). The mechanical properties of cementitious composites subjected to eight different curing and aging conditions, with a statistical significance increase in carbonated composite strength that is attributed to the packing density of the mixture containing an inert filler (silica quartz).The use of unbleached pulp with silica as a mineral addition in combination with 10 h of initial hydration prior to CO2 curing is indicated to improve the efficiency of the operational steps in the carbonated fibre-cement industry.

Jute fibers and micro/nanofibrils as reinforcement in extruded fiber-cement composites

Abstract Driven by the growing environmental concerns, vegetable fibers have been used in order to partially replace conventional synthetic fibers as reinforcement in composites. Thus, the objective of this work was to evaluate the performance of jute fibers and micro/nanofibrils (submicron elements) as reinforcement in extruded fiber-cement composites. The jute micro/nanofibrils were generated through 30 cycles of defibrillation in a SuperMasscolloider grinder. Composites extruded with 0.5%, 1.0% and 2.0% (by mass) of the resultant micro/nanofibrils were compared with composites made with the same mass proportions of the starting jute fibers (∼3 mm length). The composites were subjected to 28 days of curing, to laboratory and natural weathering before being analyzed about their physical properties, static and dynamic bending, and microstructural characterization. The dynamic modulus of elasticity of the weathering exposed composites increased gradually over time, showing that the fiber-cements became stiffer with weathering exposure. Composites reinforced with jute micro/nanofibrils, in general, presented higher mechanical performance, even when under natural weathering exposition, and showed potential for future utilization in fiber-cement composites for civil engineering or other applications.

Coconut Fiber Cement Panels as Wall Insulation and Structural Diaphragm

The study considers applications for natural fiber composites for affordable housing projects located in the two districts of Gujarat, India and Gorkha, Nepal with the goal of addressing issues of thermal comfort and lateral loading from seismic activity. To help alleviate some of these issues, the team worked with the Hunnarshala Foundation, in Bhuj, Gujarat, India, to develop a fiber cement composite that could be applied to the interior or exterior of a home and provide both insulative and structural improvements. Thermal conductivity of the composites were measured using a heat flux machine and experimental results of 0.16 W/m•K to 0.19 W/m•K showed an improvement in thermal conductivity compared to current wall cladding materials ranging from 1.60 - 1.88 W/m•K. Modeling of the building envelope was completed using the EnergyPlus™ tool and show that homes using the fiber cement composites would have an overall reduction in heating requirement of Nepalese homes by 14% and a reduction of 11% for homes in North India. The study used coconut husk fibers (referred to as coconut coir), rattan, and pine wood fibers in addition to Portland cement, fly ash, and hydrated lime in the fabrication of fiber cement composite samples. Flexural strength of these fiber samples were 70% stronger than comparison specimens, suggesting possible application for wall cladding to reduce out-of-plane failure during seismic events. Field tests conducted in Gujarat validated lab results as well qualitative perceptions of the material. Continued work with local partners presents several possible applications of coconut coir fiber cement composites for the retrofit existing housing and construction of new buildings.

Synthetic fibers for cementitious composites: A critical and in-depth review of recent advances

Abstract Owing to their remarkable physical and mechanical properties, the use of polypropylene (PP), polyethylene (PE), and polyvinyl alcohol (PVA) fibers in cementitious composites has received significant attention in recent years. This paper presents an in-depth review of the recent advances on the use of these synthetic fibers in cementitious composites as reinforcement. The fibers are categorized on the basis of their physical and mechanical properties. Throughout the review, the key fiber parameters have been identified and their influence on the physical, mechanical, and durability properties of fiber-reinforced cementitious composites (FRCCs) are discussed. To explain the observations of these properties, microstructure analyses of the composites and fibers are also presented.

Synergic effect of fiber and matrix treatments for vegetable fiber reinforced cement of improved performance

This paper assesses for the first time the effect of accelerated carbonation and hornification treatments on fiber-cement composites, both combined and independently. In order to improve the mechanical performance and durability of the material, the influence of each treatment over matrix and fiber is analyzed along time. The results indicate that hornification treatment yields greater dimensional stability improving the fiber-matrix interface and greater Specific Energy of the composites, while accelerated carbonation generates denser matrices, which increases Modulus of Rupture. After accelerated aging, the combined effect of both treatments improved the mechanical performance compared to the rest of the samples. In addition, cellulose material is preserved, showing the potential efficiency of both treatments combined on fiber/matrix.

Assessment of Destruction Processes in Fibre-Cement Composites Using the Acoustic Emission Method and Wavelet Analysis

In recent years, there has been a growing interest in fibre-cement boards as a finishing material for facades, internal walls and roofs. These panels, used in construction for over one hundred years, are made of natural ingredients such as cement, cellulose fibres and polyvinyl alcohol fibres (PVA), water and mineral fillers. It should be emphasized that due to the method of use, these elements carry loads of significant value as a result of wind pressure and suction. In addition, the boards are exposed to long-lasting atmospheric conditions such as rainfall, significant temperature fluctuations. The threatening factors also include the possibility of exceptional conditions, including fire. Long-term exposure to various types of conditions results in a significant reduction of the material’s durability after only a few years of use. In connection with the above, it is considered that it is recommended to conduct research to assess the state of fibrous - cement elements exposed to the conditions, for which they will be exposed to during operation. The article presents the possibility of using the acoustic emission method (AE) and time-frequency analysis as tools for monitoring the state of cement-fibre boards. Three-point bending tests were carried out on air and dry samples, soaked for 1 h and 24 h. Acoustic emission signals were acquired during the tests. The obtained results allowed to follow the mechanisms of destroying the examined elements and to observe the influence of the conditions and their duration on changing the way of destroying the elements.

Comparative study on properties of different straw fiber cement composites

In order to explore the effect of several common crops (wheat, corn, rice) straw on the properties of cement-based materials, the straw fiber-cement composites were prepared by dividing the straw into cement. The physical and mechanical properties of the three composites were investigated by different pretreatment methods, fiber content and fiber length. The results show that the hemicellulose content in straw decreases greatly in three pretreatment methods (cold water, 4% NaOH solution and hot alkali), and the effect of straw on retarding time of cement is weakened obviously. The increase of dimension length is disadvantageous to the mechanical strength of the composites; after pretreatment, the physical and mechanical properties of the three kinds of straw fiber-cement composites are improved. The optimum order of the three kinds of straw as cement additives is wheat > corn > rice.

"Flexural Performance of Hybrid Fiber Reinforced Cement Composites Under Elevated Temperatures"

"Historically, the flexural behavior of hybrid fiber cement composites is not completely understood using the traditional test methods. This research presents the results of an experimental investigations on a high performance cement composites (HPCC) containing both micro steel fibers (SF) and micro polypropylene fibers (PP) before and after elevated temperature exposure. The experimental program was developed to study the flexural performance (flexural strength, toughness and stiffness) under high temperature using mono and hybrid (SF) and (SF + PP) fibers. Mixtures were divided into eight different groups, with constant w/c of 0.28 and different fibers content. Based on the results of this research, the replacing of micro (SF) in high performance cement composites by 15 % of micro (PP) fibers is recommended at high temperature exposure due to the fact that all hybrid fiber HPCC specimens show slight decreasing in flexural behavior compared to samples reinforced with 1% volume fraction of mono steel fibers after high temperature exposure."

PAPERMAKING WASTE SLUDGE FIBER-CEMENT COMPOSITE PANEL: STABILIZATION AND SOLIDIFICATION OF HIGH FE AND TI CONTENT-PETROCHEMICAL ASH

ABSTRACT In this study, the effect of papermaking waste sludge (PWS), petrochemical ash, and metakaolin (MK) replacement with portland cement in the manufacturing of fiber-cement composite (FCC) was investigated. Moreover, the toxicity of materials and FCC was evaluated. Modulus of rupture (MOR), (MOE), fracture toughness (FT), internal bonding strength (IB), water absorption after 24h immersion in water (WA24), and density of FCCs were measured. X-ray diffraction patterns were also obtained. According to the main results, Composites produced with 6% PWS content showed superior mechanical properties. Higher contents of PWS resulted in the reduction in fiber-matrix interfacial adhesion, increasing void contents, and hence lower strength properties. Replacing petrochemical ash and MK up to 10% provided optimum combinations and lightweight composites. In addition, X-ray diffraction patterns confirmed pozzolanic reactions of materials. Toxicity investigation showed that concentration of heavy metals in FCC leachate were reduced compared with ash. Pozzolanic reaction of materials had positive influence on solidification and stabilization of heavy metals. In conclusion, FCCs with the highest pozzolanic activity, were considered as the optimum combination. Moreover, successful stabilization and solidification of heavy metals occurred. Therefore, not only PWS and petrochemical ash can be reused in FCC manufacturing, but they also in turn reduced environmental pollution.

Characterization of cement composites based on recycled cellulosic waste paper fibres

AbstractNowadays, there is paying an attention to the utilization of natural, renewable and biodegradable resources of raw materials of lignocellulosic character, residues from agricultural crops and wood processing as well as waste from papermaking industry in building composite materials preparing. Also recycled fibres coming from waste paper are considered as valuable material. The objective of this study is to utilize these recycled cellulosic fibres into cement composites and characterise their impact on resulting physical and mechanical properties of fresh and hardened cement composites. Manufactured cement composites contained 0.2%, 0.3% and 0.5% addition of cellulosic fibres. In fresh fibre cement mixtures reduction in workability with increasing amount of cellulose fibres was noticed. Density as well as compressive and flexural strength of 28 and 90 days hardened fibre cement composites was tested. Distribution of cellulosic fibres with 0.5% addition in hardened fibre cement composites was also observed. The results of density determination of 28 and 90 days hardened fibre cement composites showed reduction in their values related to weight lighter concretes. Compressive strengths of fibre cement composites have shown decreasing character with increasing added amount of cellulosic fibres into the mixture up to 0.5%. Maximal decrease in compressive strength values was observed in composites containing 0.5% of cellulosic fibres. However, obtained strength parameter values of hardened composites had satisfying results for their application in construction as non-load bearing building material.

Moisture sensitivity and dimensional stability of carbonated fibre–cement composites

The aim of this work was to improve the long-term performance of fabricated eco-cement composites and demonstrate the value-added use of carbon dioxide (CO2) in manufacturing sustainable products with better dimensional stability and moisture resistivity. Experiments were on pressed and non-pressed composites, fabricated with and without carbon dioxide curing. Dimensional stability comparisons were made between composites of date palm fibre and cement subjected to different moisture conditions, including air-dried, oven-dried and saturated conditions. Their flexural performances were then evaluated and compared with control specimens. The results revealed that the application of pressing and carbon dioxide curing as accelerating processing techniques have significant influences on the resultant products. The oven-dried composites exhibited poor flexural toughness behaviour compared with the air-dried or saturated specimens. Fibre growth in the transverse direction due to moisture conditions was observed to be efficient in strengthening the transition bonding areas with the matrix. In comparison with board length, the changes in board thickness and mass due to moisture effects were remarkable. This behaviour suggests that the final volume stability response of the composite is dominated by the orthotropic property due to the various constituents. Microstructural observations confirmed that carbon dioxide curing densified the matrix, leading to better dimensional stability of the composites, even after 25 wetting–drying cycles.

Characterization of Fiber-Cement Composites Reinforced with Alternate Cellulosic Fibers

The eucalyptus and araucaria fibers were used as alternatives to virgin cellulose common in fiber-cement production. Three different types of these virgin-cellulose replacements were utilized as main raw materials while the silica sand was the aggregate. Chemical and physical analyses were performed on the raw materials. In the experiments, the effect of various fiber types on the mechanical strength, water absorption and the density of fiber-cement mixture was studied for 8 wt% of these three fiber types. The excess water in homogeneous mixtures of these raw materials was first removed and then samples were pressed and baked in the autoclave. Physical and mechanical tests on these samples indicated that the fiber-cements produced with eucalyptus and araucaria cellulose were superior mechanically than those produced with virgin cellulose.

Methods of testing the properties of fibre-cement composites

The paper deals with process of manufacturing the fibre-cement materials and methods of testing their climatic performance. Basic raw materials for production fibre-cement sheets are cement, cellulose fibers, reinforcing fibers - polyvinyl alcohol (PVA) fibers, filler, additives and water. Production follows the modified Hatschek’s technology. The paper described the most important tests for climatic performance: Freeze-thaw test and Heat rain test. The fibre-cement profiled sheets were tested. The Freeze-thaw test includes assessment of frost resistance, precipitated salts efflorescence on the face-side surface, peeling of the coating on the edges, peeling of the coating on the face-side surface, longitudinal cracks in the various locations on the face-side, transverse cracks in the various locations on the face-side, shape deformation, swelling water between the layers of coating and material delamination on the edges. The frost resistance RL for fibre-cement profiled sheets after 100 freeze-thaw cycles was 0.95, when min. RL = 0.70. The fibre-cement profiled sheets were tested to 50 heat-rain cycles. After 50 cycles, the samples were checked for cracking (longitudinal, transverse and at the fixing points), delamination and other visible defects (especially the presence of formed drops on the underside of corrugated sheets). The tested modified recipe of fibre-cement profiled sheet met the Heat rain test requirements.

Cyclic flexural behavior of hybrid SMA/steel fiber reinforced concrete analyzed by optical and acoustic techniques

Superelastic shape memory alloys (SMAs) are smart materials that can recover 6–8% elastic strains due to their phase transformation. SMAs also possess unique characteristics such as good energy dissipation, excellent re-centering capabilities and corrosion resistance. Recent studies have incorporated the use of superelastic SMA fibers in cementitious composites to achieve re-centering and crack-closing capabilities. Consequently, it is important to investigate the performance of fiber reinforced concrete (FRC) members under cyclic loading. This study investigates the use of hybrid steel/SMA fibers as reinforcement in concrete members subjected to cyclic flexural loading. Digital image correlation (DIC) was used to monitor the full field displacements and strains of the concrete beam specimens. Fiber density and statistical spatial point pattern functions were used to assess the fiber distribution. Two acoustic emission sensors were attached to each side of the concrete specimens to characterize crack development. A correlation between the crack width propagation and cumulative energy captured by the acoustic emission sensors was established. Results showed that the hybrid specimen with equal fiber volume ratios for steel and SMA fibers exhibit a lower mid-span deflection and smaller crack width.

Improvement in tensile and flexural ductility with the addition of different types of polypropylene fibers in cementitious composites

The influence of addition of fibrillated and monofilament polypropylene fibers to a cementitious composite mix on the tensile strength, flexural strength and ductility characteristics of the sample are being probed in this study. The study demonstrates that addition of fibrillated variety improves the strength of the samples both in tension and flexure in comparison to that of monofilament variety, whereas the addition of monofilament variety improves the tensile and flexural ductility characteristics of the sample. A combination of both these type of fibers improves the tensile strength and ductility characteristics along with improvement in flexural ductility with no significant improvement in flexural capacity.

A new approach to improve mechanical properties and durability of low-density oil well cement composite reinforced by cellulose fibres in microstructural scale

In this research, a new approach was carried out to investigate the effect of incorporating cellulose fibres and silica fume into low-density oil well cement. Mechanical properties, durability and microstructure of the specimens were studied through various tests including; triaxial, flexural, tensile and compressive strength, cement sheath equivalent, permeability, mercury intrusion Porosimetry, ATR-FTIR analysis, degree of hydration and scanning electron microscopy. Twelve groups of the fibre-cement composite, with different amounts of silica fume and fibre content, were made and tested. The results show that the best performance belongs to the specimen reinforced by 8% fibre content and 15% silica fume in terms of mechanical properties and durability.

WET/DRY CYCLING AND THE EFFECTS OF FIBER LOADING ON THE MECHANICAL PROPERTIES OF CEMENT COMPOSITES MIXED WITH KRAFT PULP-FIBER FROM SENGON (Falcataria Mollucana) WOOD

Recently, pulp fiber-cement composites have found a practical application in the commercial market to replace hazardous asbestos fibers. For exterior applications, the effects of cyclical wetting and drying on the performance of cement composites were studied. The objective of this study was to investigate the influence of filling wood fibers in cement composites prior to and after a wet/dry cycling treatment. The testing of kraft pulp fiber filling consisted of a 3, 5, and 7% of volume fraction of the composite. The target density and water to cement ratio of the composites produced was 1.5 gcm -3 , with a 0.50 base on weight, respectively. Cement composites were formed and pressed into a mold to the targeted dimensions of 30 cm × 2.5 cm × 2.5 cm (length × width × thickness) for 24hours, before they were removed from the mold. They were then subjected into two curing system conditions. First, the boards were immersed in a water tank at 18 ± 2 °C for 28 days and then tested for their mechanical properties. Secondly, the samples were immersed in the same conditions as before, but followed by a wet/dry curing cycling for 6 times before the mechanical properties were tested. Mechanical characteristics were observed according to ASTM C293-94 for flexural strength and ASTM C116-90 for compressive strength by using a Universal Testing Machine (UTM). The addition of pulp fiber and the wet/dry cycling treatment gave a significantly linear effect on the mechanical properties of composites. The higher amount of wood fiber filling in the cement composites resulted in a lower flexural and compressive strength of the composites. Furthermore, the wet/dry cycling treatment tended to lower the flexural strength, but not the compressive strength of the composites.