No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Effect of fibre morphology on flocculation of fibre–cement suspensions
Abstract
The objective of the present research was to evaluate the effect of fibre morphology (e.g., length, width, fibrillation, broken ends, content of fines and number of fibres per gram) on flocculation and drainage properties of fibre–cement suspensions and on physical properties of the fibre–cement composites. Mechanical refining was used to change the morphological properties of Eucalyptus and Pinus pulps. Results show that the mechanical refining increased the size of the formed flocs and decreased the concentration of free small particles (with dimensions between 1 and 20 µm) as a consequence of the increased fibrillation and content of fines, which increased the capacity of the fibres to capture the mineral particles. High levels of refining were necessary for Pinus pulp to obtain cement retention values similar to those obtained by unrefined Eucalyptus pulp. This is due to the higher number of fibres per gram in Eucalyptus pulp than in Pinus pulp. Pulp refining improved the packing of the particles and, although decreased the drainage rate, it contributed to a less porous structure, which improved the microstructure of the composite.
... Avoiding or decreasing the intensity of fibre refining could be great advantage during the stock preparation due to the savings in refining energy as well as to the minimization of damages caused in the fibre cell wall, which, in general, decrease their strength. Therefore, short cellulose fibres may improve the processing of the fibre-cement product with minimal costs in their preparation [18]. There is still a lack of information regarding the influence of the eucalyptus pulp refining in the mechanical performance and durability of the fibre-cement composites. ...
... Cement based composites were reinforced with pine kraft unbleached and bleached pulps. Optimal fibre-cement formulation was chosen based on previous studies [18,19]. The suspensions with approximately 20% of solids were prepared using the following constituents (percentage by dry mass): 10.0% of cellulose pulp, 77.2% of OPC, 12.8% of ground carbonate material, and distillate water. ...
... Specimen thickness was approximately 5 mm. On completion of the immersion curing, part of specimens were tested at 28 days after production, and the other part was successively subjected to soak and dry cycles as described in details by Tonoli et al. [18] based on the EN 494 [29] standard. Each soak and dry cycle was repeated 200 times, performing the accelerated ageing test. ...
Cellulose fibres are widely available and have being increasingly used in most developing countries for construction materials applications, such as in fibre-cement products. However further work is necessary to improve mechanical performance and durability of the fibre-cement composites exposed to weathering. Although eucalyptus pulp has been widely employed in the paper industry throughout the world, there is limited information in the scientific literature concerning its use as reinforcement in fibre-cement. The objective of the present work is to evaluate the effects of eucalyptus pulp refining on fibre properties and on the performance and microstructure of fibre-cement composites. Composites were evaluated before and after accelerated ageing cycles. The mechanical refining increased the capacity of the eucalyptus fibres to capture the mineral particles improving the adherence of the fibres with the matrix. This improved fibre-matrix interface led to better mechanical properties at 28 days of cure, but led to higher mineralization of the fibres and consequently turned brittle the composites after the accelerated ageing cycles (soak and dry). Unrefined fibres maintained the toughness of the composites after ageing cycles, showing that refining of eucalyptus short fibres may be not needed for good mechanical performances at long term, which represent energy savings for fibre-cement manufacturing. These results are useful for understanding the effects of the refined fibre conditions (morphology, mechanical strength, and surface properties) to the mechanisms of fibre-matrix adherence, fibre mineralization and degradation of fibre-cement composites.
... The majority of cellulosic pulps used to reinforce cement-based materials are provided from wood resources and are obtained chemically (kraft pulp). For instance, experienced researchers in cement composites, such as Savastano and co-workers have successfully used pinus pulp [8,[21][22][23] and eucalyptus pulp [8,21,23,[25][26][27][28][29] with percentages in the range of 4-10 wt% to reinforced Portland cement matrices. Mohr and co-workers have also worked with pinus pulp obtained from chemical and thermo-mechanical treatments with percentages around 4 wt%. ...
... Coutts and Savastano and co-workers [7,9,[21][22][23][24][25][28][29][30][31] successfully used a variation of the Hatschek process (the slurry vacuum de-watering technique) to prepare cement composites with pulp fiber mass fractions of around 8 wt% (approximately 10% by volume content). In this technique the matrix materials are stirred, with the appropriate amount of fiber dispersed in water, to form a slurry with approximately 20% solid materials. ...
... Tonoli et al. [25] studied the effect of the surface modification of eucalyptus fibers on the mechanical performance of cement composites. Two silane types were used to modify the fibers: methacryloxypropyltri-methoxysilane (MPTS) and aminopropyltriethoxysilane (APTS). ...
... The use of cellulose fibers in composites is important because of the retention of Portland cement particles in the Hatschek process and some reinforcement effects in the early ages. Pinus pulp has replaced asbestos fiber as a reinforcement agent in commercial Portland cement products in conjunction with polyvinyl alcohol (PVA) fibers for air-cured (non-autoclaved) products [1,2]. A considerable research effort has been made to apply fast growing agricultural crops and crop residues as cheaper alternatives for the fiber supply, especially in countries with limited forest resources [3]. ...
... Softwood (mainly Pinus radiata) and hardwood (eucalyptus) fibers have been extensively applied as the sole reinforcing element in commercial autoclaved and air-cured Portland cement products [1,2]. Pulped cellulose fibers, require less energy in their preparation that most common synthetic reinforcing fibers, such as polyvinyl alcohol (PVA) and polypropylene (PP), and can be considered green products [4]. ...
... The work pressure was 2068 kPa at 190°C for 2 h. The average distributions of the length and width of the fibers were analyzed with a Pulptec™ MFA-500 Morphology Fiber and Shive Analyser-MorFiTrac according to the methodology adopted by Tonoli et al. [2]. ...
The potential application of bamboo organosolv pulp as a reinforcement agent in cementitious matrices was evaluated in the present experimental work. Composites with contents of bamboo pulp of 6%, 8%, 10% and 12% were tested. The composites containing 8% pulp were subjected to accelerated aging via 50, 100 and 200 aging cycles. The properties of the composites were modified after the aging cycles while considering the porosity refining due to matrix densification, which consequently improved the mechanical properties. The results indicated that the composites reinforced with bamboo organosolv pulp showed promising behavior, which was preserved in the Portland cement environment after aging.
... The software distinguished between fibres and fines through size criteria (length and width). A fine element was considered as any detected object present in the pulp with dimensions lower than those of fibres, i.e. length under 200 µm or width under 5 µm (Tonoli et al. 2009a). Microfibrils were attached to the fibre and expressed as percentage in length of microfibrils. ...
... Cement-based composites were reinforced with unbleached Eucalyptus kraft pulps. Optimal fibre-cement formulation was chosen based on previous studies (Tonoli et al. 2009a, Tonoli et al. 2012. Suspensions with approximately 20% solids were prepared using the following constituents (percentage by dry mass): 10.0% of cellulose pulp, 77.2% of OPC, 12.8% of ground carbonate material and distilled water. ...
... The refining level CSF 250 mL increased fines content and the average width of Eucalyptus fibres. The increase of fibre width by outer cell wall swelling and internal fibrillation after refining (Fardim & Durán 2003) should lead to an increase of fibre volume (Tonoli et al. 2009a). ...
Although Eucalyptus pulp has been widely used in the paper industry, there is limited information concerning its use as reinforcement in fibre-cement composites. The objective of this study was to evaluate effects of mechanical treatment (refining) of the Eucalyptus pulp on fibre properties as well as performance and microstructure of fibre-cement composites. The composites were evaluated before and after accelerated ageing cycles. The refining increased the capacity of Eucalyptus fibres to capture mineral particles, improving the adherence of the fibres with the matrix. This improved fibre-matrix interface led to better mechanical properties at 28 days of cure but higher mineralisation of fibres and consequently increased brittleness of composites after accelerated ageing (soak and dry) cycles. Unrefined fibres maintained the toughness of composites after ageing cycles. This indicates that refining may weaken the fibres thus affecting the mechanical performance (mainly decreasing modulus of rupture and toughness) of composites after ageing cycles. These results are useful for understanding effects of refined fibre conditions (morphology, mechanical strength and surface properties) on mechanisms of fibre-matrix adherence, fibre mineralisation and degradation of fibre-cement composites.
... Avoiding or decreasing the intensity of fibre refining could be great advantage during the stock preparation due to the savings in refining energy as well as to the minimization of damages caused in the fibre cell wall, which, in general, decrease their strength. Therefore, short cellulose fibres may improve the processing of the fibre-cement product with minimal costs in their preparation (Tonoli et al., 2009). ...
... This equipment consists basically of a CCD (charge-coupled device) camera that captures images of the fibre/water suspension and records them for further analyses by software that operates the measurements and statistical corrections (Wätzig, 2008). Detailed procedure and other morphological characteristics of these pulps were presented in Tonoli et al. (2009). ...
... Fibre-cement suspensions were prepared using the following constituents (percentage by dry mass): 10% of pulp (at different refining intensities), 77.2% OPC (ordinary Portland cement) and 12.8% ground carbonate material. Flocculation experiments were performed in 400 mL fibre-cement suspension of 50 g/L at around 28 • C, as described in detail in Tonoli et al. (2009). Three replicates were carried out for each experiment. ...
This paper evaluates the advantages of using hardwood short fibre pulp (eucalyptus) as alternative to softwood long fibre pulp (pinus) and polymer fibres, traditionally used in reinforcement of cement-based materials. The effects of cellulose fibre length on microstructure and on mechanical performance of fibre–cement composites were evaluated before and after accelerated ageing cycles. Hardwood pulp fibres were better dispersed in the cement matrix and provided higher number of fibres per unitary weight or volume, in relation to softwood long fibre pulp. The short reinforcing elements lead to an effective crack bridging of the fragile matrix, which contributes to the improvement of the mechanical performance of the composite after ageing. These promising results show the potential of eucalyptus short fibres for reducing costs by both the partial replacement of expensive synthetic fibres in air curing process and the energy savings during pulp refining.
... To improve the mechanical performance of lignocellulosic fibers as reinforcing elements, an increase of the fiber content is required. Different studies have confirmed that fibercement reinforced only with eucalyptus and pine microfibers does not undergo significant flexural strength loss after 1 3 aging when Ca(OH) 2 content is reduced at early hydration stages of the cementitious matrix [13,14]. This long-term improvement related to a microfiber integrity allows to increase the amount of cellulose fiber from 1.5 to 10%, which translates into a cost benefit [12]. ...
... Accelerated aging cycles were conducted according to previous experiments [21]. Previous studies have indicated that 200 cycles of accelerated aging is enough to evaluate deterioration effects on cellulosic micro-reinforcement elements in Portland fiber-cement [13,14,21]. We expected to reach relevant aging effects on macrofibers with the increase of accelerated aging cycles from 200 to 400. ...
The aim of this work is to evaluate the effects of sisal fiber exposure to cement matrices with different alkalinity in order to assess their viability as reinforcing elements in cementitious composites. To improve sisal fiber durability, this study introduces the use of a different calcium (Ca)-free cement binder based on MgO and SiO2. Sisal fibers were exposed to both MgO–SiO2 and conventional Portland cement to compare chemical interactions before and after different aging conditions by TGA, XRD and SEM/EDS analysis. MgO–SiO2 cement removes the amorphous phases of sisal fibers similarly to NaOH treatments used for polymeric composites. Contrarily for cements with high Ca(OH)2 concentration, MgO–SiO2 cement promotes the hydrolysis of the fibers only in the amorphous phase, while the cellulose content and crystallite size was hardly modified. Sisal fibers exposed to MgO–SiO2 cement do not present any extra crystalline phase related to the cement hydration products. Thus, fiber mineralization process is avoided, whereas good adherence is promoted between M-S-H gel and fibers.
... Nevertheless, the use of shorter eucalyptus fibers is a new tendency all over the world [14], with promising results that backup the implementation of this cellulosic material as reinforcement in cementitious products [11,17,18]. This type of fiber exhibits good quality [19], lower cost, larger amount of fibers by mass https://doi.org/10.1016/j.conbuildmat.2019.02.007 0950-0618/Ó 2019 Published by Elsevier Ltd. [20] and, because of the shorter size of these fibers, a better dispersion of the fibers within the matrix [21]. ...
... This process aims to simulate in as faster way the ageing of FC products under service conditions. For that, environmental conditions of heat and rain are extremely reproduced in a climate chamber, model MA 035, Marconi brand, following the methodology set by [20], who adapted the 494-EN Standard [52]. This procedure was repeated until 200 cycles were completed. ...
h i g h l i g h t s Hornification generates a hydrophobic fiber with better dimensional stability. Composites reinforced with hornificated pulp and AC showed better MOR and SE values. Hornification fibers and AC presents potential to be used as combined treatments. Composites with hornificated pulp and AC improved durability of pulps after ageing. Composites with hornificated pulp and AC showed better physico-mechanical performance. a b s t r a c t 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 carbona-tion 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.
... The average distributions of the length and width of the pulp were analyzed using a Pulptec TM MFA-500 Morphology Fibre and Shive Analyser -MorFiTrac, according to Tonoli et al. [37] and Correia et al. [33]. The structure and the size of the nanofibrillated cellulose were examined from the images obtained via Scanning Transmission Electron Microscopy (STEM) (FEI Magellan 400 L Scanning Electron Microscope), according to Correia et al. [21]. ...
... After curing a part of the composites at 28 days was subjected to characterization in dry condition and another part was subjected to accelerated aging test for the evaluation of durability of the composites. The samples were submitted to 200 cycles of immersion and drying (as utilized by Correia et al. [33] and Tonoli et al. [37], based on reccommendations by the EN 494 Standard [41] modified. ...
The use of cellulose nanofibers as reinforcement may contribute for improving particle packing and decrease the crack growth rate of composites at nanoscale. Additionally, the high specific surface area of cellulose nanofibers contributes to improve the adhesion between the cement particles. Thus, the aim of this work was the study the performance of hybrid composites reinforced with 8% pulp and 1% nanofibrillated cellulose compared to composites reinforced with only 9% of pulp produced by the extrusion process. The accelerated aging process by means of 200 wet and dry cycles was carried out to assess composite degradation. In the hybrid composites the nanofibrillated cellulose improved the mechanical behavior compared to the composite without nanofiber. This improvement may be associated with greater adherence between the nanofibrils and the cement matrix. After accelerated ageing, the composites with and without nanofibers showed no reduction in mechanical performance, which is attributed to the lower alkalinity provided by the accelerated carbonation. Therefore, the nanofibrillated cellulose showed to be a promising material for use as nanoreinforcement of the extruded hybrid cement-based composites.
... A fine element (small particles with length lower than 200 mm that are commonly called fines, which also contain bandlike materials from both primary wall and secondary wall layers of the fibers) was detected in the pulp with dimensions lower than those of fibers. Fines do not contribute significantly to cement based composite strength but act more as filler [18]. Physical characteristics of the unbleached eucalyptus pulp are showed in Table 1. ...
... Physical characteristics of the unbleached eucalyptus pulp[18]. ...
The present study shows the application of the nanoindentation technique to evaluate the properties of the cellulose fiber-cement matrix interfacial zone in composites prepared with an auger extruder. The degree of strength of the bond between fiber and matrix is recognized as important variable that influences macro-mechanical properties, such as modulus of rupture and toughness of cement based composites. The nanoindentation measurements showed the highest hardness and elastic modulus in the part inner of the cellulosic fiber after hydration process due to precipitation and re-precipitation of cement hydration products. These results indicate that mineralization of the cellulosic fibers can affect the stress distribution and interfacial bond strength in the cement based composite.
... The use of long fibers (e.g. Pinus) as reinforcement is common in fiber cement products on the current market [6]. These fibers generally perform better than short fibers (e.g. ...
... Moreover, they are thicker fibers with thick cell walls and therefore, they are stronger compared to fibers with thin cell walls [8]. Regarding short fibers, its use is economically more favorable [6], their lower fiber length allows a higher concentration of fibers per gram, improving their dispersion and distribution within the matrix [9], favoring the performance of the material. ...
This study evaluated the effect of the hornification process on cellulosic fibers of bleached pine and unbleached eucalyptus with in order to improve its durability and volume stability to be used as reinforcement in cementitious matrices. The study indicated that the treatment did not deteriorate the properties of viscosity and index of crystallinity and decreased the capacity of water retention. Composites reinforced with hornificated and untreated pulps with thermal curing or accelerated aging were produced and evaluated to assess their physical and mechanical behavior. The use of hornificated fibers as reinforcement generated improvements in the modulus of rupture and specific energy of the composites.
... The formulation was based on previous studies carried out in an attempt to produce durable fiber cement by the slurry-dewatering technique and using vegetable pulps as reinforcement [17,18]. The following materials and ratios were used (by dry mass): 10.0% of unrefined unbleached eucalyptus cellulosic pulp, 77.2% of Portland cement type CPV-ARI [19] and 12.8% of ground carbonate material industrialized for agricultural application, which was added as partial substitution of Portland cement in order to reduce the cost. ...
... Chemical compositions (% by mass of oxides) of the cement and ground carbonate material were determined using X-ray fluorescence spectrometry and are presented in Table 1. Morphological properties of the unrefined unbleached eucalyptus pulp are presented in Table 2 [18]. Total residual lignin content (TRLC) and the amount of wood extractives of the pulp was 2.2 ± 0.1% w/w and 0.5 ± 0.1% w/w, respectively [7]. ...
... Characterisation of the fibre-cement The cehning level CSF 250 mL increased composites content and the average width of Eucalyptus fibres. The increase of fibre width by outer Mechanical tests were performed using the cell wall swelling and internal fibrillation after testing machine equipped with 1 kN load cell, refining (Fardim & Durán 2003) should lead to Four-point bending configuration was employed an increase of fibre volume (Tonoli et al. 2009a). to evaluate the limit of proportionality (LOP), One of the effects of refining on cellulosic modulus of rupture (MOR), modulus of elasticity fibre structure is the fibrillation of the fibre (MOE) and toughness of the specimens (Tonoli surface (Coutts 2005). Both microfibrils and et al. 2009b). ...
... This contributes to in water in order to normalise the humidity the development of a net inside the composite condition. Six specimens were used for testing (Tonoli et al. 2009a). of each design. Physical properties, namely, Figure la presents the individual fibre strength apparent porosity (AP) and bulk density (BD) and fibre bonding index (fibre bonding capacity) values were obtained from the average of six assessed by zero-span measurements of the pulps at different refining rates. ...
Although Eucalyptus pulp has been widely used in the paper industry, there is limited information concerning its use as reinforcement in fibre-cement composites. The objective of this study was to evaluate effects of mechanical treatment (refining) of the Eucalyptus pulp on fibre properties as well as performance and microstructure of fibre-cement composites. The composites were evaluated before and after accelerated ageing cycles. The refining increased the capacity of Eucalyptus fibres to capture mineral particles, improving the adherence of the fibres with the matrix. This improved fibre-matrix interface led to better mechanical properties at 28 days of cure but higher mineralisation of fibres and consequently increased brittleness of composites after accelerated ageing (soak and dry) cycles. Unrefined fibres maintained the toughness of composites after ageing cycles. This indicates that refining may weaken the fibres thus affecting the mechanical performance (mainly decreasing modulus of rupture and toughness) of composites after ageing cycles. These results are useful for understanding effects of refined fibre conditions (morphology, mechanical strength and surface properties) on mechanisms of fibre-matrix adherence, fibre mineralisation and degradation of fibre-cement composites.
... A fine element (small particles less than 200 μm in length, commonly referred to as fines and also containing ribbon-like materials from both the primary and secondary wall layers of the fibers) with dimensions smaller than those of the fibers was found in the pulp. Fines do not contribute significantly to the strength of cement-based composites, but rather act as fillers [22]. ...
... The durability of the composites reinforced by vegetable fibers was evaluated using the accelerated aging method. This method consists in exposing the specimens to wet-dry cycles, similar to natural climatic conditions; in a climatic chamber model MA 035 (Marconi, Brazil) according to Ref. [41]. Each cycle was composed of: (1) complete immersion in water for a duration of 170 min; (2) drying at (70 ± 5) • C for 170 min. ...
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.
... Fig. 1c shows a transmission electron micrograph (TEM) of the nanofibrils obtained by mechanical defibrillation of the starting cellulose pulp fibers. Defibrillation decreases the average fiber length significantly and increases the swelling capacity by fracturing the fibrils, resulting in a considerable increase in surface area (Tonoli, Fuente et al., 2009;Tonoli et al., 2016;Tonoli, Rodrigues Filho et al., 2009). High shear applied to fibers during defibrillation efficiently disintegrated fibers into small fragments and, to some extent, separated individual nanofibrils. ...
Mining activities promote the development of economies and societies, yet they cause environmental impacts that must be minimized so that their benefits overcome the likely risks. This study evaluated eco-friendly technologies based on the use of low-carbon footprint wastes and industrial by-products as soil amendments for the revegetation of Zn-mining areas. Our goal was to select adequate soil amendments that can be used to recover these areas, with a focus on low-cost materials. The amendments - limestone, sewage sludge, biochar, and composted food remains - were first characterized concerning their chemical composition and structural morphologies. Soil samples (Entisol, Oxisol, Technosol) from three different areas located inside an open-pit mine were later incubated for 60 days with increasing doses of each soil amendment, followed by cultivation with Andropogon gayanus, a native species. The amendments were able to change not only soil pH, but also the phytoavailable levels of Cd, Zn, and Pb. Limestone and biochar were the amendments that caused the highest pH values, reducing the phytoavailability of the metals. All amendments improved seed germination; however, the composted food remains presented low levels of germination, which could make the amendments unfeasible for revegetation efforts. Our findings showed that biochar, which is a by-product of the mining company, is the most suitable amendment to enhance revegetation efforts in the Zn-mining areas, not only because of its efficiency and cost, but also due to its low carbon footprint, which is currently the trend for any "green remediation" proposal.
... Softwood pulps, especially those with low lignin content, are already in current use in the Brazilian cement industry. Additionally, hardwood pulps have been studies in countries where their production is abundant [8]- [9]. ...
Vegetable fibers are a hierarchical structure material in the macro, micro and nanometric scales that have been used as reinforcement in cementitious materials. In nanoscale, the nanofibrillated cellulose has the advantage of having good mechanical performance and high specific surface, which contributes to improve the adhesion between fiber and matrix. In hybrid reinforcement, with micro and nanofibers, nanofibrillated cellulose forms bonding with the matrix and acts as stress transfer bridges in the nano-cracking with corresponding strengthening of the cementitious composite. Processing has a strong influence on performance of the fiber cement composite. Two fabrication methods were evaluated: (i) slurry dewatering followed by pressing and (ii) extrusion. The extrusion process strongly depends on the rheological characteristics of the fresh cement material but it can better organize the microstructure of the fiber cement due to the partial orientation of the fibers in the extruder direction. Curing process also plays a key role in the performance of the final product. Accelerated carbonation at early age is a promising technology and a strategy to mitigate the durability problems with the composite materials; it decreases porosity, promotes a higher density in the interface guarantying a good fiber–matrix adhesion and a better mechanical behavior. Alternative MgO-SiO2 clinker free binder is also presented as a suitable alternative to cementitious products reinforced with cellulosic pulps. Finally, mechanical behavior of fiber cement under flexural loading is evaluated by modulus of rupture, fracture toughness, the initial crack growth resistance in cement matrix, and fracture energy that is obtained to evaluate the influence of toughening mechanisms promoted by fibers, such as pullout and bridging, on the mechanical performance of the composites. Degradation during the service life is also crucial for the evaluation of the durability of the resulting materials and components in real applications exposed to different environmental conditions as roofing, partitioning or ceiling elements. It can be concluded that more sustainable and high performance components based on engineered natural raw materials for civil construction can bring valuable contributions for the affordable housing in particular to developing region.
... Softwood pulps, especially those with low lignin content, are already in current use in the Brazilian cement industry. Additionally, hardwood pulps have been studies in countries where their production is abundant [8]- [9]. ...
Vegetable fibers are a hierarchical structure material in the macro, micro and nanometric scales that have been used as reinforcement in cementitious materials. In nanoscale, the nanofibrillated cellulose has the advantage of having good mechanical performance and high specific surface, which contributes to improve the adhesion between fiber and matrix. In hybrid reinforcement, with micro and nanofibers, nanofibrillated cellulose forms bonding with the matrix and acts as stress transfer bridges in the nano-cracking with corresponding strengthening of the cementitious composite. Processing has a strong influence on performance of the fiber cement composite. Two fabrication methods were evaluated: (i) slurry dewatering followed by pressing and (ii) extrusion. The extrusion process strongly depends on the rheological characteristics of the fresh cement material but it can better organize the microstructure of the fiber cement due to the partial orientation of the fibers in the extruder direction. Curing process also plays a key role in the performance of the final product. Accelerated carbonation at early age is a promising technology and a strategy to mitigate the durability problems with the composite materials; it decreases porosity, promotes a higher density in the interface guarantying a good fiber–matrix adhesion and a better mechanical behavior. Alternative MgO-SiO2 clinker free binder is also presented as a suitable alternative to cementitious products reinforced with cellulosic pulps. Finally, mechanical behavior of fiber cement under flexural loading is evaluated by modulus of rupture, fracture toughness, the initial crack growth resistance in cement matrix, and fracture energy that is obtained to evaluate the influence of toughening mechanisms promoted by fibers, such as pullout and bridging, on the mechanical performance of the composites. Degradation during the service life is also crucial for the evaluation of the durability of the resulting materials and components in real applications exposed to different environmental conditions as roofing, partitioning or ceiling elements. It can be concluded that more sustainable and high performance components based on engineered natural raw materials for civil construction can bring valuable contributions for the affordable housing in particular to developing region.
... The dark purple color of the nanocomposite sheet is attributed to the surface plasmon resonance (SPR) of the AuNPs [62], implying the direct formation of gold nanostructures on the UBK fiber. In general, the greater the degree of refining of pulp, the more fines and internalexternal fibrillations are present, resulting in less porous fiber-fiber interconnections, directly contributing to decreased drainage and dewatering rates [63,64]. As water is gradually removed during drying, the voids left by water become partly substituted with air and partly compensated through shrinkage [65]. ...
Although low density polyethylene (LDPE) has long been widely used in the applications of packaging, some limitations in relatively poor gas barrier and low mechanical strength restrict its extension to the more advanced applications such as electronic and pharmaceutical packaging. In this study, montmorillonite (MMT) nanoclay was employed to enhance the thermal, mechanical, and barrier properties of LDPE prepared via melt-extrusion. The level of exfoliated dispersion of the MMT nanoclay in the prepared LDPE-MMT composite was confirmed by transmission electron microscopy (TEM). The relationship between the resulting morphology and the thermal, mechanical, and barrier properties as a function of the MMT content was evaluated. The results showed that incorporating >3 wt.% of MMT nanoclay produces significant changes in the morphology of the LDPE-MMT nanoclay composite—the segregated matrix adopted an oriented arrangement of exfoliated clay platelets. Thermogravimetric analysis (TGA) showed that the thermal stability of LDPE improves significantly as a result of MMT nanoclay incorporation. Further, differential scanning calorimetry (DSC) analysis suggested that increasing clay content above 3 wt.% can effectively reduce the crystallinity of LDPE-MMT composites through the suppression effect. The tensile strength of LDPE increased gradually with increasing content of MMT nanoclay and the maximum value of 16.89 N/mm2 was obtained at 10 wt.% MMT content. This value represents a 40.87% increase relative to the tensile strength of the pristine LDPE. Barrier properties of LDPE and LDPE-MMT nanoclay composites were assessed by examining oxygen permeability and water vapor permeability. As the content of MMT nanoclay was increased to 10 wt.%, the permeability of the nanocomposite films to oxygen and water vapor decreased notably to 42.8% and 26.2%, respectively.
... The dark purple color of the nanocomposite sheet is attributed to the surface plasmon resonance (SPR) of the AuNPs [62], implying the direct formation of gold nanostructures on the UBK fiber. In general, the greater the degree of refining of pulp, the more fines and internalexternal fibrillations are present, resulting in less porous fiber-fiber interconnections, directly contributing to decreased drainage and dewatering rates [63,64]. As water is gradually removed during drying, the voids left by water become partly substituted with air and partly compensated through shrinkage [65]. ...
Gold nanoparticles (AuNPs) were directly synthesized and anchored on lignocellulose fiber without an external immobilizing agent via a facile green approach using unbleached kraft (UBK) softwood pulp. The obtained AuNPs were confirmed by UV–Vis diffuse reflectance spectroscopy, field-emission scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The antioxidant behavior of the as-prepared AuNP-UBK fiber nanocomposite was evaluated by free radical scavenging of 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH). The nanocomposite fiber exhibited greatly enhanced radical scavenging activity compared to that of the pure fiber. As a consequence, AuNP-UBK nanocomposite paper showed exceptional antioxidant performance with a radical scavenging rate of over 98%, which is attributed to the synergistic effects of adsorption by the fiber-fiber network and subsequent catalytic activity of the AuNPs. This research indicated that AuNP-UBK fiber nanocomposites could be a new candidate for antioxidant active packaging for use in food preservation.
... Fig. 1c shows a transmission electron micrograph (TEM) of the nanofibrils obtained by mechanical defibrillation of the starting cellulose pulp fibers. Defibrillation decreases the average fiber length significantly and increases the swelling capacity by fracturing the fibrils, resulting in a considerable increase in surface area (Tonoli, Fuente et al., 2009;Tonoli et al., 2016;Tonoli, Rodrigues Filho et al., 2009). High shear applied to fibers during defibrillation efficiently disintegrated fibers into small fragments and, to some extent, separated individual nanofibrils. ...
... Tonoli et al. [73] claimed that mechanical refining increased the size of the formed flocs and decreased the concentration of free small particles, which increased the capacity of the fibres to capture the mineral particles and affected the setting behaviour of the composites. ...
... The thickness of the microfibers (pulp) was determined by using Pulptec MFA-500 equipment -MorFiTrac or morphology fiber and shive analyzeraccording to the procedure adopted by Tonoli et al. 38 The thickness of the nanofibrillated cellulose was determined from scanning transmission electron microscopy (STEM) images. An image analysis software (ImageJ) was used to measure the thickness of the nanofibrillated cellulose. ...
The aim of this study was to evaluate the potential use of bamboo macro-, micro-and nanofibers as reinforcement in organic and inorganic matrices. Macrofibers were obtained from bamboo culms, microfibers were produced by organosolv pulping, and nanofibrillated cellulose was obtained by a grinding process. The results showed that after pulping of macrofibers, the crystallinity index increased by 16% and the amount of lignin, hemicellulose and extractives decreased by 42, 33 and 84% respectively. Furthermore, after nanofibrillation the crystallinity index of the pulp decreased by 6·7%; the thermal stability also decreased. After pulping, the thickness of the bamboo fibers was reduced by a factor of 13, while after nanofibrillation the thickness was reduced by a factor of 1222. According to the results of the mechanical characterization of the bamboo fibers carried out on macro-, micro-and nanofibers, bamboo can be used as a reinforcement in organic and inorganic matrices.
... The individual macrofibers were obtained from the bamboo chips, and the average diameter of the 50 fibers was determinate using a Mitutoyo micrometer, where, in each fiber was determinate an average of the 3 diameter. The diameter of the microfibers (pulp) was analyzed in a PulptecTM MFA-500 equipment -Morphology Fiber and Shive Analyser -MorFiTrac, according to [11]. The average diameter of the nanofibers was measured from the 150 fibers by Scanning Transmission Eletronic Microscopy images, using the free software to image analysis ImageJ. ...
Vegetal fibers are obtained from leaves, stalks, culms, fruit and seeds, and have been used in the macro, micro and nanoscale as partial replacement of synthetic fibers in organic and inorganic matrices. Bamboo has high strength fibers, and is one of main nonwood resources and is available in tropical areas worldwide. These characteristics justify the study and application of bamboo fiber as reinforcement in the macro, micro and nanoscale. The macrofibers were obtained from bamboo culms, the microfibers from the chemical pulping and the nanofibers were obtained from the mechanical nanofibrillation of the pulp. The fibers were subjected to chemical, physical, mechanical and morphological tests. There was modification in the chemical composition of the bamboo after pulping, such as decrease of amount of the lignin, hemicellulose and extractives in 42.4%, 33.3% and 83.7%, respectively.The bamboo fibers width have been reduced from 0.26 mm to 19.8 μm after pulping and after nanofibrillation process the width was reduced from 19.8 μm to 16.2 nm.The decrease of the fibers dimension can be seen from the micrographs and analyzing it mechanical properties, the bamboo fibers are a reinforcement potential in macro, micro and nanoscale to organic and inorganic matrices.
... Um estudo paramétrico e aprofundado sobre a reação do CO 2 com cada constituinte do cimento foi realizado por Peter et al. (2008). A relação entre as alterações do pH da fase líquida existente nos poros da matriz cimentícia e a instabilidade dos produtos de hidratação conforme o grau de solubilidade foi estudada por diversos autores (GABRISOVA et al., 1991; LAGERBLAD, 2005; TAYLOR, 1997). O Ca(OH) 2 é o composto com maior grau de solubilidade e, portanto, o que reage mais rapidamente com o CO 2 para a formação do CaCO 3 (PADE; GUIMARAES, 2007). ...
O objetivo deste trabalho foi avaliar o efeito carbonatação acelerada nas propriedades físicas e desempenho mecânico de compósitos cimentícios reforçados com altos teores de polpas celulósicas. Os compósitos foram moldados em laboratório pelo processo de sucção a vácuo do excesso de água e posterior prensagem, e a carbonatação acelerada foi realizada em diferentes estágios de cura. O estudo das propriedades microestruturais foi realizado por microscopia eletrônica de varredura ambiental e difração de raios X. Os resultados obtidos mostraram que a carbonatação acelerada nos primeiros dias de cura resultou em maiores resultados de propriedades mecânicas e melhora na interface fibra-matriz. A carbonatação acelerada reduziu o conteúdo de portlandita [Ca(OH)2] e aumentou o teor de calcita [CaCO3] que é o principal composto resultante da carbonatação. Consequentemente, ocorreu a redução da alcalinidade na matriz cimentícia, o que pode favorecer a durabilidade das fibras celulósicas que se destacam como alternativas às fibras minerais e sintéticas, e podem contribuir para o desenvolvimento sustentável na tecnologia dos materiais de construção.
... The composites prepared with swine deep bedding ashes (SDBA) as a partial substitute for ordinary Portland cement (OPC) and short sisal fibres presented higher toughness (specific energy of 100 J/m 2 ) than the reference composites without SDBA and sisal fibres (specific energy of 40 J/m 2 ) at 28 days of age. Table 1 shows the results of bamboo pulps analyzed by a Pulptec™ MFA-500 Morphology Fibre and Shive Analyser MorFiTrac, as described in details by Tonoli et al. (2009). This equipment consists basically of a charge-coupled device (CCD) camera that captures the images of the fibre/water suspension and records them for further analysis with the software that carries out the measurements and statistical corrections. ...
Agro-industrial wastes have recently attracted a great deal of attention as potential alternative of raw material applied to different rural buildings. This paper summarizes the results of some researches carried out by the Rural Constructions Group at the University of Sao Paulo, Brazil focused toward the development of fibre reinforced cement incorporating agroindustrial wastes. Studies have been developed in two main themes regarding (i) ashes with pozzolanic activity as partial substitutes of the ordinary Portland cement (OPC) and (ii) vegetable fibres for the improvement of physical and mechanical performance of such cementitious composites. Some examples of these two groups of residual materials are the use of ashes of sugar cane waste, from rice husk and swine deep bedding, and fibres extracted from the husk of the green coconut, bamboo pulp obtained by organosolv process and recycled Kraft pulp recovered from cement bags. The work shows the procedures of processing of these materials in the way that they can be successfully used in the production of the cement based composites. The extrusion is also evaluated as a potential process for the production of cementitious composites due to the improvements achieved in the mechanical and microstructural behavior. The modification of the matrices by accelerated carbonation was applied in the initial ages after fabrication, resulting in the upgrade of the mechanical behavior of the resulting materials. Keywords: fibre reinforced cement composite, vegetable fibre, sugar cane waste, bamboo, swine deep bedding, ashes. INTRODUCTION Composite materials constituted by natural fibres and ashes with pozzolanic activity constitute a current area of interest in the materials science concerning with the sustainability especially for applications in agriculture environment. This work presents the results of some researches carried out by the Rural Constructions Group at the University of Sao Paulo in Pirassununga campus, Brazil, toward the development of cement based materials incorporating agroindustrial wastes, and resulting in potential improvement of the physical and mechanical performance of the resulting elements.
... Unrefined unbleached Eucalyptus pulp morphological properties a[6]. Fibers were analyzed by a Pulptec TM MFA-500 Morphology Fiber and Shive Analyser -MorFiTrac. ...
The properties of cement based composites depend not only on the properties of their individual components but also on their interfacial characteristics and transition zone between fiber and matrix. There has been a renewed interest in the use of cellulosic pulp as micro-fiber reinforcement in cement based composites. The addition of nanoparticles, such as colloidal silica, to fiber-cement could allow a better control of its microstructure and the enhancement of the matrix/fiber interface. The objective of this work is to evaluate the effects of colloidal silica on the microstructure and mechanical performance of cementitious matrices and fiber-cement composites. These cementitious materials were prepared with 0%, 1.5%, 3%, 5% and 10% w/w colloidal silica suspension content. Cementitious matrices without fibers were produced by vibration. Fiber-cement composites with unbleached Eucalyptus kraft pulp as a micro-fiber reinforcement were produced by the slurry dewatering technique followed by pressing. All composite materials were cured by water immersion. A splitting (Brazilian) test was carried out to determine the tensile strength of cementitious matrices. Mechanical behavior of the fiber-cement composites was evaluated via modulus of rupture and fracture toughness based on load-displacement curves (L-d curves) under continuous loading and 3-point bending arrangement. The energy of fracture was measured through a stable crack propagation test with SENB (single-edge notched bending) configuration also under a 3-point bending arrangement. The matrix with highest content of colloidal silica suspension (10% w/w) presented high values of water absorption and consequently presented the lowest splitting tensile strength. The average values of modulus of rupture and fracture toughness of fiber-cement tend to decrease with increasing colloidal silica content. However, the pullout mechanism increased significantly in the fiber-cement composites with additions between 3% and 10% w/w of colloidal silica suspension as compared to that without any addition, noted by degree of improvement in the energy of fracture and by scanning electron microscopy micrographs (SEM). These findings show the potential use of colloidal silica to improve the transition zone between the cellulosic fiber and the cementitious matrix. The results of this study show an important way to engineer and control the fracture process of the composites.
... During the de-watering stage, pulp forms a net that retains cement grains. Advances were proposed with new methodology for flocculant selection (36) or to evaluate the best refining degree (37,38) in order to improve fiber bonding, processing and strength of the fiber-cement composites produced. Moreover, there are particular aspects of the bleached and unbleached pulps that have been discussed in the litetature. ...
The present review shows the state-of-art on the approachs about improving the processing, physical-mechanical performance and durability of non-conventional fiber-cement composites. The objective of this review is to show some of these strategies to mitigate the degradation of the vegetable fibers used as reinforcement in cost-effective and non-conventional fiber-cement and, consequently, to improve their mechanical and durability properties for applications in the housing construction. Beyond the introduction about vegetable fibers, the content of this review is divided in the following sections: (i) surface modification of the fibers; (ii) improving fiber-to-cement interface; (iii) natural pozzolans; (iv) accelerated carbonation; (v) applications of nanoscience; and (vi) principles of functionally graded materials and extrusion process were briefly discussed with focus on future research needs.
... Eucalyptus has especially good properties for the production of chemical pulps (Magaton et al. 2009 ). Moreover, Eucalyptus fibers have a high potential as a reinforcement in biocomposites (Tonoli et al. 2009(Tonoli et al. , 2010a. For example, Eucalyptus fibers produced by the mechanical processes, which have high lignin content, improve the long-term performance of the fiber-cement composites (Tonoli et al. 2010b ;Muguet et al. 2012 ). ...
A novel alternative was investigated for elevating the xylan content of eucalyptus pulp through xylan deposition in the course of the oxygen delignification stage. The pH in the range of 10–13 was the only variable evaluated, while the other variables were kept constant in a range similar to industrial practice. Xylans were obtained from unbleached and bleached eucalyptus pulps by cold caustic extraction (CCE), giving rise to brown xylan liquor (BXL) and white xylan liquor (WXL), respectively. The liquors were added to a commercial brown pulp during oxygen delignification. The xylan-enriched pulps were subsequently bleached to 90% ISO with the D(EP)D sequence, beaten in a PFI mill and evaluated for their physical and mechanical properties. Xylan deposition occurred at variable degrees depending upon the pH. Pulp bleachability was not impaired by WXL xylan deposition but was slightly negatively affected by BXL xylan. Pulp beatability was improved by both WXL and BXL xylan deposition. The deposited xylan was more stable across bleaching and beating with the WXL xylan than the BXL xylan deposits. At low energy consumption, the deposited xylan improved pulp physical and mechanical properties. Xylan extraction by CCE with subsequent deposition in the oxygen delignification is an interesting technique to manufacture eucalypt pulps of high xylan content. The potential for industrial application is high as no significant modification of current pulp mill installations is needed.
... The composites had an average water-cement ratio of 0.36. The fibers were analyzed using a Pulptec TM MFA-500 Morphology Fiber and Shive Analyzer-MorFiTrac [26] a Length weight in length b A fine element was considered as any detected object present in the pulp with dimensions less than those of the fibers, i.e., length under 200 lm or width under 5 lm Pozzolanic activity A semi-quantitative determination of the pozzolanic activity using the electric conductivity method was performed [7]. This method follows the conductivity of the pozzolan-calcium hydroxide solution with the reaction time. ...
The effect of colloidal silica on the hydration reaction of the Portland cement system and its effect on the resulting mechanical properties are not completely under-stood. Silica nanoparticles can affect the behavior and performance of fiber–cement, such as the calcium–silicate– hydrate gel of the matrix and the fiber–matrix interface bonding. The main objective of this study is to evaluate the effects of various contents of colloidal silica (0, 1.5, 3, 5, and 10 % w/w) on the microstructure and mechanical performance of cement composites reinforced with cellu-losic pulp. Fiber–cement composites with unbleached eucalyptus Kraft pulp as the micro-fiber reinforcement were produced by the slurry dewatering technique followed by pressing. The average values of the modulus of rupture of the fiber–cement decreased with increasing colloidal silica content. However, the pullout of the fibers increased significantly in the fiber–cement composites with additions between 3 and 10 % w/w of colloidal silica suspension, as indicated in the scanning electron microscopy images and by the improvement in the energy of fracture values.
... As shown in Table 1, the newsprint pulp presents shorter fibres, and it is expected that they collapse due to successive drying and rewetting cycles during the newsprint manufacturing, which probably improved the packing of the cement matrix. A comprehensive study of the relation of fibre morphology with cement matrix flocculation and packing was presented by Tonoli et al. [30]. ...
This paper discusses the effects of different ageing conditions on the mechanical and physical characteristics of cementitious roofing tiles reinforced with sisal and newsprint pulps, sisal strand fibre and polypropylene (PP) fibre. Roofing tiles with undulate shape were produced by a slurry de-watering and pressing technique. They were subjected to three distinct ageing conditions: fast carbonation, accelerated ageing cycles and fast carbonation plus accelerated ageing cycles. Fast carbonation did not improve the maximum load (ML), limit of proportionality (LOP), toughness and maximum deflection but did decrease their water absorption, apparent porosity and air permeability; however, after 50 heat and rain accelerated ageing cycles, it was ineffective in maintaining the mechanical properties (ML, LOP, toughness and deflection) of the tiles reinforced with vegetable fibres. The refined sisal pulp fibres led to roofing tiles with slightly higher LOP, toughness and maximum deflection than those reinforced with newsprint pulp fibres. PP fibres significantly improved the mechanical performance (ML, LOP, toughness and deflection) of the roofing tiles in relation to sisal strand fibres. The accelerated ageing cycles were effective in promoting severe degradation on the roofing tiles with sisal strand fibres, while the tiles reinforced with PP fibres were practically unaffected.
... Pine fibers and fines lengths are notably greater than those of hemp core fibers and these parameters also have a significant effect on the mechanical properties of the probes. Fines do not contribute significantly to fiber-cement strength but act more as filler and, in most cases, influence negatively the drainage of the suspension (Tonoli et al., 2009). Furthermore,Fig. ...
The aim of this paper is to study the feasibility of using cellulose fibers obtained from an agricultural waste, hemp core (Cannabis Sativa L.), through different new environmental friendly cooking processes for fiber-cement production. The physical and mechanical properties of the fiber reinforced concrete, which depend on the nature and morphology of the fibers, matrix properties and the interactions between them, must be kept between the limits required for its application. Therefore, the morphology of the fibers and how its use affects the flocculation, retention and drainage processes in the fiber-cement manufacture, and the mechanical and physical properties of the fiber-cement product have been studied.The use of pulp obtained by means of the hemp core cooking in ethanolamine at 60% concentration at 180 °C during 90 min resulted in the highest solids retention and the best mechanical properties among the studied hemp core pulps.
... Cellulose hand sheets from unbleached and bleached pulps were prepared, using deionized water and following the procedures described by TAPPI Production of the fibre-cement composites Cement-based composites were reinforced with pine kraft unbleached and bleached pulps. Optimal fibre-cement formulation was chosen based on previous studies [34,35]. The suspensions with approximately 20% of solids were prepared using the following constituents (percentage by dry mass): 10.0% of cellulose pulp, 77.2% of OPC, 12.8% of ground carbonate material and distilled water. ...
The goal of this article was to evaluate the surface characteristics of the pine fibres and its impact on the performance of fibre–cement composites. Lower polar contribution of the surface energy indicates that unbleached fibres have less hydrophilic nature than the bleached fibres. Bleaching the pulp makes the fibres less stronger, more fibrillated and permeable to liquids due to removal the amorphous lignin and its extraction from the fibre surface. Atomic force microscopy reveals these changes occurring on the fibre surface and ontributes to understanding the mechanism of adhesion of the resultingfibre to cement interface. Scanning electron microscopy shows that pulp bleaching increased fibre/cement interfacial bonding, whilst unbleached fibres were less susceptible to cement precipitation into the fibre cavities (lumens) in the prepared composites. Consequently, bleached fibrereinforced composites had lower ductility due to the high interfacial adhesion between the fibre and the cement and elevated rates of fibre mineralization.
... Eucalyptus has especially good properties for the production of chemical pulps (Magaton et al. 2009 ). Moreover, Eucalyptus fibers have a high potential as a reinforcement in biocomposites (Tonoli et al. 2009(Tonoli et al. , 2010a. For example, Eucalyptus fibers produced by the mechanical processes, which have high lignin content, improve the long-term performance of the fiber-cement composites (Tonoli et al. 2010b ;Muguet et al. 2012 ). ...
The importance of Eucalyptus wood as a sustainable resource is well established. Mechanical pulp production is an energy-intensive process, and methods for decreasing energy demand are needed. In the present article, the structure of Eucalyptus hybrids and the produced pulps from the hybrids were assessed in terms of energy consumption, technical properties, and fiber morphology. The defibration and fiber development were investigated by traditional thermomechanical pulping in laboratory scale. There was no clear difference in the extent of defibration and fibrillation among the hybrids, with the exception of one hybrid (U2xGL1). Guaiacyl lignin contents of more than 7.2% had a minor influence on energy consumption, and this finding is different from the results of previous studies on chemimechanical pulping processes. However, a low amount of guaiacyl lignin (6.1% based on wood) decreased the energy demand. This assessment is of major importance concerning the energy-saving defibration during thermomechanical pulping production.
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.
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.
The addition of sepiolite in fibre-cement is analysed as a possible additive constituent of MgO-SiO2 binders. In order to optimise the Mg-SiO2 cementitious system in fibre-cement sheets, small cement replacement (1 and 2 wt%) by sepiolite is introduced and its effects are studied, firstly, in hardened cement pastes and, later, in fibre-cement systems. When used only in cement pastes, non-destructive studies are employed to assess flexural performance over time as well as the possible reactivity between additive and cement, proving that Elastic Modulus is increased. When sepiolite is introduced in fibre-cement, the properties of the slurry suspensions and its interference in the Hatschek process are studied. It is shown that sepiolite addition increases floc size of MgO-SiO2 systems. Finally, flexural tests are performed to understand the outcome of this additive of the mechanical performance of the samples, proving that sepiolite improves the product homogeneity, which is essential for industrial applications.
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.
Natural fibres as dispersed reinforcement in cement-based materials may represent an interesting alternative to industrial fibres, because of their good mechanical properties and inborn sustainability signature. In this section the mechanical properties of Natural Fibre Reinforced Cementitious Composites (NFRCCs) will be reviewed. Cutting-edge topics will be finally addressed, focusing, on the one hand, on the use of nano-sized cellulose-based constituents in cementitious composites, and, on the other, on the self-healing capacity that natural fibres may bring to cementitious composites. An appendix summarizing the main properties of the natural fibres so far most commonly employed in cementitious composites will complement this information.
The possibility of using wastes, such as corn stalk and hemp core, as raw material for asbestos-free fiber-cement is quite feasible, considering environmental and economic aspects. However, although there are many studies on the use of other agricultural wastes, there is a lack of information on the characterization of these pulp fibers and their use as reinforcement in fiber-cement corrugated sheets. In this chapter, the feasibility of using organosolv pulps obtained from corn stalk (Zea mays L.) and industrial hemp core (Cannabis sativa L.) as a source of reinforcement fibers in the production of fiber-cement is studied. The morphology of the pulp and its effect on flocculation, retention, and drainage processes and on physical and mechanical properties of the product are presented. Results show that the replacement of pine fibers by those from agricultural wastes, especially hemp core organosolv fibers, improves retention and drainage process while allowing to obtain a fiber-cement with similar physical and mechanical properties to that from pine Kraft fibers.
This paper presents a review of the recent research and development of natural fibre-reinforced concrete (NFRC). The recent developments on NFRC reinforced with different types of natural fibres, such as sisal fibre, bagasse fibre, coir fibre, banana fibre, eucalyptus fibre, flax fibre, jute fibre and pinus radiate fibre are covered. Natural fibres and their modification methods are firstly introduced, and the development history of natural fibre reinforced concrete and the relevant research on the mechanical behaviour of NFRC in both short term and long term are reviewed. The applications of NFRC are also summarized.
Nonconventional building materials and their application have been extensively investigated as an alternative for cost-effective housing in developing countries. The present work contributes to the widespread use of the vegetable fibers as a source of raw material that may be used to reinforce composites and give them new properties for applications as insulating panels, roofing tiles, siding, etc. The mechanical and physical characteristics of the different types of vegetable fibers available must be determined to better explore their potential as reinforcement. Similarly, their morphological properties (length, diameter, and fibrillation) and chemistry of their surface lead to important changes in the fiber to cement bond in vegetable fiberereinforced cement materials. Fibrillation and hydrophilicity of the fiber surface improves the fiber to cement adherence. The use of regional agro-industrial residues and local vegetable fibers is a constructive way to minimize transport energy and simplify logistics in the global civil construction market. The possibility of using carbon dioxide for accelerating the hardening and stabilization of products made from Portland cement is also attractive. Accelerated carbonation curing has been studied to mitigate the cellulose fiber degradation in the cementi- tious composites and for the maintenance of their mechanical performance under weathering. Initial efforts to explore nanotechnology and/or nanoscience in the development of the construction industry have focused on understanding the nano- scale phenomena and improving the performance of commercial materials and products. The use of nanoreinforcements and functional nano structures incement-based composites has been scarcely explored in the literature, and therefore further investigation is merited. Further development and optimization of the me- chanical defibrillation process could lower the production costs of micro/nanofibers for engineering of fiberecement materials. The development of standard pull-out test procedures and standardization of equipment suitable for testing particular vegetable fibers should be considered and better explored. Additionally, new methods for producing the cementitious composites may also be considered having the goals of low energy consumption, varied geometry of products, lower initial investment requirements for a new plant, the use of simpler machines for contin- uous production, the possibility of partial alignment of fibers, and new concepts and technologies to improve durability.
The current study has been carried out in the attempt to durable fibre-cement composites by means of accelerated carbonation in the early stage of cement hydration. Fibre-cement composites were produced by the slurry dewatering and pressing technique. Two days after moulding, the composites were carbonated under controlled conditions: 60°C and 90% of relative humidity. The work evaluated the effect of the accelerated carbonation on physical characteristics and mechanical performance of the cementitious composites. Microstructure characteristics of the composite were studied by environmental scanning electron microscopy (ESEM) and thermal analysis. Preliminary results showed that the accelerated carbonation in the first days of cure improved the mechanical performance and resulted in a denser matrix, which suggests that it can be an effective procedure to improve initial strength of composites and to mitigate the degradation of cellulose fibres.
The aim of this study was to evaluate the effect of accelerated carbonation on the physical characteristics and mechanical performance of cement composites reinforced with high-content cellulose pulps. The fiber-cement composites were produced in the laboratory through the slurry dewatering and pressing technique, and accelerated carbonation was applied in different curing stages. The microstructure characteristics were investigated using environmental scanning electron microscopy (ESEM) and X-Ray diffraction. Results showed that the accelerated carbonation in the first days of curing improved the mechanical performance and fiber-matrix interface. The accelerated carbonation decreased the portlandite [Ca(OH)2] content and increased the calcite [CaCO3] content, which is the main compound produced by the carbonation process. As a result, the alkalinity of the cement matrix decreased, which can favor the durability of the cellulosic fibers that have been recognized as an alternative for mineral and synthetic fibers, and may contribute to the sustainable development in construction materials technology.
The availability, relative consistency, and renewability of hardwood pulp fibers have prompted interest in their use in fiber–cement composites, in which they may be used for a variety of purposes. This study clarifies the ability of hardwood pulp to reinforce mortar, its capacity to provide internal curing, and its role as early-age crack-control reinforcement through a coordinated series of restrained shrinkage, free shrinkage, and mechanical testing on mortar samples. It finds that hardwood pulp improves the restrained shrinkage behavior of mortar at an early age. That is, 0.5% and 0.75% (by volume) hardwood pulp-reinforced mortars exhibited a lower rate of stress development and lengthened time-to-cracking by about 1.6 times and 2.3 times, respectively, compared to a companion crack-prone ordinary mortar. The initial crack width also decreased by 88% in 0.75% hardwood pulp-reinforced mortar samples, which suggested an application aimed at assisting self-healing in cement-based materials with an appropriate binder composition. Hardwood pulp successfully provided internal curing to crack-prone mortar and thus reduced autogenous shrinkage. This reduction in shrinkage, together with a combination of increased early tensile capacity, reduced stiffness, and improved post-cracking toughness were identified as the key contributions of hardwood pulp in the improved resistance of mortar to early-age cracking.
Fibre-cement products had been widely used in the world due to their versatility as corrugated and flat roofing materials, cladding panels and water containers presented in large number of building and agriculture applications. The main reason for incorporating fibres inio the cement matrix is to improve the toughness, tensile strength, and the cracking deformation characteristics of the resultant composite. One of the drawbacks associated with cellulose fibres in cement application is their dimensional instability in the presence of changing relative humidity. The objective of the present work is to evaluate the effect of surface treatment of eucalyptus cellulose pulp fibres on the processing and dimensional changes of fibre-cement composites. Surface modification of the cellulose pulps was performed with methacryloxypropyltri-methoxysilane (MPTS), aminopropyltri-ethoxysilane (APTS) and n-octadecyl isocyanate, an aliphatic isocyanate (AI), in an attempt to improve their dimensional instability into fibre-cement composites. X-ray photoelectron spectroscopy (XPS) showed the chemical changes occurred at the surface, and contact angle measurements showed the changes in the surface energy. MPTS- and AI-treated fibres presented lower hydrophilic character than untreated fibres, which led to lower water retention values (WRV). APTS increased the water retention value of the pulp and improved the capacity of hydrogen bonding of the fibres. MPTS- and AI-treated fibres led to low final water/cement ratios and reduced volume changes after pressing. MPTS-treated fibres decreased the water and dimensional instability of the fibre-cement composites, while the contrary occurred with APTS-modified and AI-modified fibres. These results are promising and contribute for new strategy to improve processing and stability of natural fibres-reinforced cement products.
The objective of the present work is to evaluate the impact of the surface grafting of cellulose fibres on the processing, dimensional stability and mechanical performance of fibre–cement composites. The surface modification of the pulps was performed with methacryloxypropyltri-methoxysilane (MPTS), aminopropyltri-ethoxysilane (APTS) and n-octadecyl isocyanate, an aliphatic isocyanate (AI). X-ray photoelectron spectroscopy (XPS) showed that the chemical changes have indeed occurred at the surface, and contact angle measurements showed that the surface energy has also changed. MPTS- and AI-treated fibres presented lower hydrophilic character than untreated fibres, whereas APTS increased the water retention value of the pulp. MPTS-treated fibres decreased the water retention and improved dimensional stability of the fibre–cement composites, while the contrary occurred with other modified fibres. Fibre–cement strength was little influenced by fibre treatment, whereas AI-treated fibres contributed to higher specific energy (SE) and the lower SE value for APTS-treated fibres is an indication of the improvement on fibre to cement adherence. These results are promising and contribute toward new strategies to improve the processing and stability of natural fibre-reinforced cement products.
A treatment disrupting the wall structure of high-freeness TMP pulp fibres and its effect on the energy consumption in the subsequent refining were studied. Subjecting the pulp fibres to an abrasive material resulted in the disruption, opening, peeling-off, and weakening of fibre cell walls. In the subsequent refining, the pulp quickly developed to the desired quality for the making of paper, while the energy consumption in refining was reduced. Laboratory sheets showed no significant degradation of mechanical and optical properties.
Over the last three decades considerable research has been committed to finding an alternative fibre to replace asbestos in fibre cement products. Australian research was centred on natural fibres and ultimately it was a natural fibre, wood pulp fibre, that was responsible for the greatest replacement of asbestos in the beleaguered global fibre cement industry. This review reports some of the Australian research that was carried out to establish natural fibres as a suitable reinforcement for cement products. Much research data is locked away in the archives of companies. The preparation and properties of the fibres are discussed briefly as well as their compatibility with existing processing technology. Some explanation of the bonding and microstructural behaviour (under load) within these composite materials is presented and related to their performance in service. The spread of the Australian wood fibre cement technology and the range of applications for which the natural fibre cements are used are discussed briefly, particularly with reference to USA and Asian activities. (c) 2004 Elsevier Ltd. All rights reserved.
A methodology to study flocculation processes and floc properties using a non-imaging scanning laser microscope is presented in this paper. This methodology allows us to study floc stability and resistance to shear forces, re-flocculation tendency and reversibility of the flocs. Furthermore, optimal dosage of any polymer and the associated flocculation mechanism can be determined. In order to illustrate the technique, some examples applied to flocculation in papermaking are described. Although in this paper all the examples have been applied to papermaking, the developed methodology can be used in any process in which flocculation phenomena is involved.
On présente dans cet article une méthode pour étudier les procédés de floculation à l'aide d'un microscope laser à balayage sans imagerie. Cette méthode permet d'étudier la stabilité des flocs et leur résistance aux contraintes de cisaillement, la tendance à la refloculation et la réversibilité des flocs. De plus, on peut déterminer le dosage optimal de tout polymère et le mécanisme de floculation associé. Pour illustrer cette technique, quelques exemples appliqués à la floculation dans la fabrication du papier sont décrits. Cependant, même si dans cet article tous les exemples s'appliquent à la fabrication du papier, la méthodologie peut s'appliquer à tout procédé comportant des phénomènes de floculation.
The effect of digestion conditions (amount of effective alkali, digestion time) on the surface compositions of unbleached softwood (Pinus sylvestris) kraft pulp has been investigated by electron spectroscopy for chemical analysis (ESCA). The quantities monitored were the angular dependence of the total O/C ratio, the relative amounts of carbons in different states of oxidation and the adsorption of Al and Ca ions to the carboxyl groups in the surface. Examination of the angular dependence of ESCA intensities shows that the concentration of alkyl carbon is high in a very thin surface layer and that it decreases linearly with decreasing kappa number. The concentration of alkyl carbon is decreased by extraction of the fibres with dichloromethane, but the amount remaining in the surface after extraction still decreases linearly with decreasing kappa number (i.e. it decreases with increasing digestion time). It is suggested that the observed enrichment of alkyl carbon in the outermost surface layers most probably is due to reprecipitation of lignin. In pulp that has not been extracted, there is also strong enrichment of extractives in the surface. This amount increases with increasing effective alkali but is relatively independent of digestion time. ESCA analysis of the Al and Ca bound to the carboxyl groups shows that the amount depends on digestion time; the results are consistent with the notion that the reprecipitated lignin contains carboxyl groups.
Over the last three decades considerable research has been committed to finding an alternative fibre to replace asbestos in fibre cement products. Australian research was centred on natural fibres and ultimately it was a natural fibre, wood pulp fibre, that was responsible for the greatest replacement of asbestos in the beleaguered global fibre cement industry.This review reports some of the Australian research that was carried out to establish natural fibres as a suitable reinforcement for cement products. Much research data is locked away in the archives of companies. The preparation and properties of the fibres are discussed briefly as well as their compatibility with existing processing technology. Some explanation of the bonding and microstructural behaviour (under load) within these composite materials is presented and related to their performance in service. The spread of the Australian wood fibre cement technology and the range of applications for which the natural fibre cements are used are discussed briefly, particularly with reference to USA and Asian activities.
The purpose of this study was to determine the technical feasibility of employing magazine wastepaper fibers as reinforcement in thin cement. Wastepaper fiber-composites were first recycled. The samples were then technically evaluated versus virgin composites and were shown to posses acceptable flexural strength, dimensional stability, density, water absorption and moisture content. The differences of recycled fibers with virgin fibers in cement composites were verified using the specifics of the size distribution of the recycled fibers.
This study deals with the effect of charged groups on the rheology and state of dispersion of papermaking fibers. The charged groups were introduced onto a softwood kraft pulp through carboxymethylation. The rheology of the fiber network was studied using a jar with a rotor equipped with a force gauge so that the yield stress of the fiber network could be determined. The state of flocculation was characterized by studying the characteristic floe size in a flowing suspension using a digital camera interfaced with a dedicated image analysis system. The results showed that the yield stress and floe size decreased when the degree of carboxymethylation (Na-form) increased. These results were interpreted in terms of a lower fiber-fiber friction due to the creation of gelatinous surface layers when the solubility of the surface molecules at the fiber-water interface was increased through the introduction of charged carboxymethyl groups.
The effects of fiber length, fiber consistency, fiber curl brought about by beating, and fiber aspect ratio on pulp flocculation were studied by measuring the floc sizes (i.e. the characteristic floc size) and the total variance of flocculation intensity in highly turbulent fiber suspensions. The tendency of native cellulose fibers to build flocs has been investigated by considering the physical, morphological and mechanical aspects of a commercial bleached kraft pulp, prior to the addition of typical papermaking chemicals. Increasing fiber length at the same fiber diameter increased the floc size. At lower values of fiber aspect ratio a diminished floc size was found. The findings show that there is a rank order through the investigated parameters. Fiber length seems to have a dominant role followed directly by fiber curl index measured on flowing fiber suspensions. The morphological aspect of the fiber, the fiber aspect ratio, has an important role in flocculation as well. However, fiber flexibility induced by beating exerts a minor influence on the flocculation process, compared to the other parameters investigated.
The optimisation of the flocculation process during fibre cement production is a new key issue for the fibre cement industry. Many companies face difficulties in optimising the flocculant dosage in real time, which leads to product strength losses. This paper shows the feasibility of using artificial neural networks (ANNs) to establish correlations between flocculation data, in-line measured in a Hatschek machine by a focused beam reflectance measurement (FBRM) sensor, and mechanical properties of final composites. The results show a clear relationship between the mechanical properties of fibre cement composites and the flocculation process and that these are determined in real time. Three ANNs have been created to predict breaking load for 48 h and 7 days and bending strength for 7 days, to obtain good correlations between the predicted and the real values.
In the Hatschek process used to produce fibre–cement products, it is necessary to use a suitable flocculant when asbestos is substituted by pulp fibres. The right selection of flocculant is crucial in the industrial process due to its effects on mineral fines retention, dewatering and formation and, as a consequence, on the overall efficiency of the machine. This paper presents a two-step methodology for flocculant selection in the fibre–cement manufacture. The first step is based on the study of the flocculation processes and the flock properties, using a focused beam reflectance measurement (FBRM). This technique allows the study of flock size, flock stability and flock resistance to shear forces, reflocculation tendency and reversibility of the flocks, as well as the optimal flocculant dosage for each particular fibre–cement suspension. The second step uses a drainage vacuum tester to study retention and dewatering. The two techniques give important and complementary informations that allow a proper selection of the best flocculant for the fibre–cement manufacture.
The effects of laboratory pulping and refining on the surface properties of eucalyptus kraft pulp fibres were investigated using Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS or ESCA) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). Refining affected fibre structure, surface morphology, lignin (φlig), carbohydrate (φcarb) and extractive (φext) surface coverage. The φlig and φcarb, estimated with XPS, decreased and increased with refining, respectively. The φext changed according to the pulping conditions. Cellulose, xylan, lignin, sterols, fatty acids and their salts were identified by ToF-SIMS. Significant changes in the normalized ToF-SIMS peak intensities were observed after refining. The release of xylan and fatty acid salt aggregates formed in pulping and entrapped in the cell wall pores with subsequent adhesion to the fibre external surfaces was suggested as a source of surface chemical modification by refining.
Wood fiber is used to replace asbestos in the manufacture of fiber cement due to its high availability, low cost and good reinforcement properties. The different chemical composition of the cellulose fibers makes its compatibility with the cement much more complex than that of asbestos fibers. In the Hatschek process a suitable flocculant is needed when using cellulose fibers. The right selection of the flocculant is crucial due to its effect on mineral fines retention, dewatering and formation and, as a consequence, on the overall efficiency of the machine. This paper shows how anionic poly-acryl-amides (A-PAM), the most common flocculants used in Hatschek machines, have a negative effect on the bending strength properties of fiber cement sheets. In order to overcome this problem fiber surface treatment, with sizing agents, is proposed in this paper. Sizing with styrene-acrylate copolymers and alkyl ketene dimer produces an increase in bending strength properties.
The use of cellulose, instead of asbestos, in the fibre cement composites manufacture, using the Hatschek process, reduces cement retention and makes necessary to use a flocculant which is crucial for the plant productivity. The use of different types and doses of polyacrylamides (PAM) as well as the addition process, have been studied to obtain an in-depth knowledge of floc properties. A real-time methodology has been used to study size, shape, strength and reversibility of formed flocs, based on a focused beam reflectance measurement (FBRM) system. The results have been corroborated by particle vision and measurement (PVM) analysis. This paper shows that anionic PAM (A-PAM) are the most suitable to induce cement flocculation and to obtain optimal properties of the formed flocs. This is because the flocculation process is enhanced by the interaction of the Ca2+ ions, produced by the cement hydration, with the carboxylic groups of the polymer chains. Cations not only increase the stiffness of the chains, improving floc strength, they also enhance the importance of the patching aggregation mechanism when the initial bridges are broken. Higher molecular weight polymers improve initial aggregation but the effect of anionic charge is more important for a stable flocculation with time under variable shear conditions. Results show that the optimal dosage is between 100 and 200 ppm.
Fibre reinforced cement-based composites were prepared using kraft pulps from sisal and banana waste and from Eucalyptus grandis pulp mill residues. The study adapted conventional chemical pulping conditions for the non-wood strands and a slurry vacuum de-watering method for composite preparation followed by air-curing. Plain cement paste and Pinus radiata kraft reinforced cement composites were used as reference materials. Mechanical testing showed that optimum performance of the various waste fibre reinforced composites was obtained at a fibre content of around 12% by mass, with flexural strength values of about 20 MPa and fracture toughness values in the range of 1.0–1.5 kJ m−2. Experimental results showed that, of the waste fibres studied, E. grandis is the preferred reinforcement for low-cost fibre-cement.
Although in the industrial Hatschek process it is necessary to use flocculants to improve retention, dewatering and formation, the use of flocculants may also decrease the strength of the final product. This paper studies the influence of the molecular weight and the anionic charge of anionic polyacrylamides on the flocculation behaviour of fibre cement suspensions and on the bending strength of the final product. Flocculants influence the density of the final product and in-turn the lowering of the density results in strength reduction. Results showed that an increase in the flocculant molecular weight reduces the bending strength of the composites significantly due to its density reduction. However, an increase in flocculant anionic charge increases the bending strength of composites. Therefore, in order to optimise the fibre cement process, it is necessary to use flocculants with high anionic charge and medium molecular weight.
Paper and Board Testing Committee, SCAN CM 15:99. Viscosity in cupriethylenediamine solution
- Scandinavian Pulp
Scandinavian Pulp, Paper and Board Testing Committee, SCAN CM 15:99. Viscosity
in cupriethylenediamine solution. Stockholm, Sweden, 1999.
Test Method for Dry and Wet Bulk Density, Water Absorption, and Apparent Porosity of Thin Sections of Glass–Fiber Reinforced Concrete
- American Society
- Testing
- Astm C Materials
American Society for testing and materials, ASTM C 948-81. " Test Method for Dry
and Wet Bulk Density, Water Absorption, and Apparent Porosity of Thin Sections of
Glass–Fiber Reinforced Concrete ". West Conshohocken, PA, USA, 1981.
Formation and Structure of Paper
- D H Page
- P A Tydeman
D.H. Page, P.A. Tydeman, Formation and Structure of Paper (F. Bolam, Ed.) Tech.
Sect. British Paper and Board Makers Association, London, 1962.