This research analyzes the effects of different treatments on flax nonwoven (NW) fabrics which are intended for composite reinforcement. The treatments applied were of two different kinds: a wet/dry cycling which helps to stabilize the cellulosic fibers against humidity changes and plasma treatments with air, argon and ethylene gases considering different conditions and combinations, which produce variation on the chemical surface composition of the NWs. The resulting changes in the chemical surface composition, wetting properties, thermal stability and mechanical properties were determined. Variations in surface morphology could be observed by scanning electron microscopy (SEM). The results of the X-ray photoelectron spectroscopy (XPS) showed significant changes to the surface chemistry for the samples treated with argon or air (with more content on polar groups on the surface) and ethylene plasma (with less content of polar groups). Although only slight differences were found in moisture regain and water retention values (WRV), significant changes were found on the contact angle values, thus revealing hydrophilicity for the air-treated and argon-treated samples and hydrophobicity for the ethylene-treated ones. Moreover, for some of the treatments the mechanical testing revealed an increase of the NW breaking force
This research analyzes the effects of the previous wetting and drying treatments of cellulosic fibers on the fiber–matrix bond strength of cement based composites. First, three kinds of fibers—abaca, cabuya and sisal—were subjected to five cycles of water wetting and subsequent drying. The resulting changes in the morphology, mechanical properties, drying kinetics and thermal stability were determined with scanning electronic microscopy (SEM), tensile tests and thermogravimetric analysis (TGA) respectively. A reduction in the cross section, an increase in Young’s modulus and adecrease in tensile strength and tensile strain as well as a structure with thinner pores was found for the treated fibers. Second, cement based composites with untreated and treated fibers were prepared to evaluate the fiber–matrix bonding before and after accelerated aging. For this purpose the interfacial shear strength (IFSS) between the fibers and the matrix was determined by the single fiber pull-out test after seven days of curing in a humidity chamber and after four aging wetting–drying cycles. The treatment of the fibers results in an increase in the interfacial shear strength of the cement composites also improving the durability
Ventura, H.; Claramunt, J.; Navarro, A.; Rodríguez-Pérez , M.; Ardanuy, M. International Conference on Biodegradable and Biobased Polymers p. 1-2 Presentation's date: 2015-10-08 Presentation of work at congresses
lmprovement of the fire behaviour of flax fabrics treated with silica
coatings containing expandable graphite preparad through sol-gel treatment
has been studied. Results show that silica coating containing expandable
graphite enhances the flax fabric fire behaviour.
Fernandez-Carrasco, L.; Claramunt, J.; Llerena, A.; Torrens, D.; Ardanuy, M.; Zamora, J.Ll. International Conference on Bio-based Building Materials p. 46-51 Presentation's date: 2015-06-22 Presentation of work at congresses
Traditionally, architectural materials performance was the key point for developing materials; but nowadays, other criteria’s as sustainability, availability and recyclability are being considered. By the other hand, the addition of fibres as polymers, steel or glass on cement based materials was proved to enhance their performance in terms of ductility, tensile strength, toughness, fatigue strength, impact resistance and energy absorption capacity of matrices. Actually, the use of vegetable fibres as reinforcement for cement composites is particularly attractive since they are widely available, are biodegradable, and inexpensive. The attractive mechanical and physical properties joint to their environmental benefits combination are the main drivers to use them as alternatives for conventional reinforcements. Bio-fibres as flax fibres have been large used mainly for automotive products. Plus other mentioned properties, the low density of these vegetable fibre composites induces to consider them as an interesting architectural material for envelope skill applications. This research deals with the manufacturing of façade pieces from white Portland cement and treated flax nonwoven fibre composites. The study of the physical properties, i.e. flexural, water permeability, dimensional change of these façade components were also analysed before and after 60 days outdoor exposition
A combination of reinforcements at different levels can have a synergetic effect on the final properties of a composite. The aim of this work was to produce, evaluate, and compare the wet/dry cycling durability of the exposure of cement composites reinforced with conventional pulps at the micro-scale level, with nanofibrillated cellulose fibers at the nano-scale level, and with combinations of both reinforcements (hybrid composites). To evaluate the durability of their mechanical properties, the composites were tested under flexural loading after 28 days of humidity chamber curing and after 20 wet/dry accelerating aging cycles. Composites reinforced with the nanofibrillated cellulose exhibited significant lyhigher flexural strength and flexural modulus, but they had lower fracture energy values than those reinforced with conventional sisal fibers. Moreover, the hybrid composites with a high content of nanofibrillated cellulose maintained or even improved their properties after aging
In the last few years, an increase in interest has been given to the use of cellulose fibers as alternatives for conventional reinforcements in composites. The development of commercially viable environmentally friendly and healthy materials based on natural resources is on the rise. In this sense, cellulosic fibers as reinforcements for cement mortar composites constitute a very interesting option for the construction industry. This paper presents a review of the research done during the last years in the area of the cement-based composites reinforced with cellulose fibers. The fibers used, processing methods, mechanical behaviour and durability are presented. The main achievements found have been the development of durable cement composites with optimized fiber–matrix adhesion. Moreover, the recently developed textile composites will allow obtaining high performance materials reinforced with vegetable fibers
Claramunt, J.; Fernandez-Carrasco, L.; Ardanuy, M. International RILEM Conference on Strain Hardening Cementitious Composites p. 163-170 Presentation's date: 2014-11-05 Presentation of work at congresses
In this work the mechanical behaviour of ductile cement composites reinforced with natural fibre nonwovens is evaluated under flexural and direct tension tests. The effect of the nonwoven structure –weight and thickness on the mechanical behaviour is also investigated. Results obtained indicate that the nonwoven natural fibre reinforcement leads to cement composites with substantial enhancement of the ductility.
With the aim of developing vegetable-fibre cement composites free of portlandite and with short curing process, this study analyses the influence of the curing conditions and the addition of pozzolanic material on the hydration of Portland cement–fibre matrices. Different specimens of cement composites with and without cellulose fibres and with and without silica fume were cured using autoclaving steam and normal curing. The hydration products and the microstructure of the resulting pastes were analysed by means of FTIR and BSE–SEM and the degree of hydration was quantified with Image analysis. The results indicate that the hydration products and the hardness of the pastes depend on the three analysed factors: curing method, silica fume, and presence of fibres
This research analyses the effects of the previous wetting and drying treatments of vegetable fibres on the fibre-matrix bond strength of cement based composites. Firstly three types of vegetable fibres –abaca, fique and sisal- were subjected to five cycles of wetting and drying. The resulting changes in the morphology, mechanical properties, drying kinetics and thermal stability were determined with scanning electronic microscopy (SEM), tensile tests and thermogravimetric analysis (TGA) respectively. Secondly, cementitious composites with the treated and untreated fibres were prepared to evaluate the fibre-matrix bonding. For this purpose the interfacial shear strength (IFSS) between the fibres and the matrix was determined by single fibre pull-out test after 7 days of curing in humidity chamber and after four wet–dry cycles of cement aging
Producto de material compuesto de aglomerante inorgánico y fibras vegetales celulósicas; constituido dicho producto en forma de placa, que comprende: - una primera capa externa (1) constituida por una pasta rica en aglomerante y sin fibras de refuerzo, - una matriz inorgánica (2) mineral, que contiene cemento, cal o yeso, material puzolánico y aditivo fluidificante; e incluye varias capas (21) de tejido no tejido (T), superpuestas, con un espesor de 2 a 4 milímetros, con un gramaje comprendido entre 200 y 600 gr/m2; constituidas por fibras vegetales celulósicas de una longitud comprendida entre 3 y 6 centímetros, unidas por punzonado y - una segunda capa externa (3) constituida por una pasta rica en aglomerante, sin fibras de refuerzo, conformante de una segunda cara de la placa. La invención incluye un proceso de fabricación de dicho producto.
En este trabajo se evalúan las propiedades mecánicas de compuestos a base de morteros de cemento reforzados con fibras vegetales en forma de telas no tejidas. Para ello se han diseñado y preparado previamente estructuras no tejidas con fibras de cáñamo y lino y se ha analizado su potencial como refuerzo de cementos portland con ensayos de flexión por tres puntos comparándose los resultados con los de compuestos convencionales reforzados con pulpa de conífera.
El objetivo del presente trabajo es desarrollar compuestos de cemento reforzados con fibras vegetales que presenten una mayor durabilidad y que puedan curarse con tiempos cortos. Para ello se analizan la influencia de las condiciones de curado – en autoclave o en cámara estándar– y la adición de humo de sílice y fibras de sisal en la hidratación y resistencia de matrices de cemento portland.
This work presents the preparation and characterization of new cement mortars reinforced with conventional pulps at the micro-scale level and nanofibrillated cellulose fibers at the nano-scale level. The conventional pulps have been obtained by subjecting sisal fibers to a soft mechanical treatment and the nanofibrillated cellulose has been prepared by the application of a high intensity refining process. Based on the preliminary results of this research it can be concluded that to obtain cement mortar composites with high modulus, strength and toughness the combination of both scale cellulose fibers could be an interesting solution
The aim of this work is to evaluate the mechanical performance of cement mortar composites reinforced with various percentages of cellulose fibres. Results indicated that for low content of fibres there is a high adhesion between the cement matrix and the fibres and, consequently, the fracture of the composite under flexural stress occurs by rupture of the matrix and the fibres. However, for higher fibre content, the collapse of the material occurs by a progressive rupture of the matrix which is dispersed in a dense network of fibres and which disintegrates, releasing the fibres. These results could be interesting for modelling the mechanical performance of vegetable fibre reinforced cement mortar composites.
In this work, the evaluation of the durability to wet/dry cycling exposure of cement composites reinforced with nanofibrillated cellulose comparing the results with composites reinforced with conventional cellulose fibres at the micro-scale level has been performed. For this purpose, cement mortar composites reinforced with cellulose fibres from conventional sisal pulp and cellulose nanofibres prepared by the application of a high intensity refining process have been prepared. The mechanical performance of the composites prepared was tested after 7 days of cure treatment and after 5 wet/dry cycles. The cement mortar composites reinforced with the nanofibrillated cellulose exhibited higher flexural strenght and flexural modulus but lover values of fracture energy than the ones reinforced with the conventional sisal fibres. No significant improvements of the durability were found for the composites prepared with nanofibrillated cellulose
In this work, nanofibrillated cellulose (NFC) has been evaluated as a potential reinforcement for cement mortar composites. Two types of vegetable fibres with different composition and properties (cellulose content and microfibrillar angle), sisal, and cotton linters pulps, were initially characterized in order to assess their reinforcement capability. Sisal pulp was found to be most suitable as reinforcement for their brittle cementitious matrix. Nanofibrillated cellulose was produced by the application of a high intensity refining process of the sisal pulp. It was found that 6 hours of refining time was required to obtain the desired nanofibrillation of the fibers. Cement mortar composites reinforced with both the sisal fibers and the nanofibrillated cellulose were prepared, and the mechanical properties were determined under flexural test. The cement mortar composites reinforced with the nanofibrillated cellulose exhibited enhanced flexural properties, but lower values of fracture energy, than the ones reinforced with the conventional sisal fibres.
In this work, the preparation and characterization of new cement mortars reinforced with nanofibrillated cellulose fibres has been carried out. The effect of the fibre fibrillation degree on the mechanical performance of the obtained composites is presented and analyzed, taking into account the reinforcement final size depending on the intensity of the mechanical treatment applied. On the one hand, conventional pulps have been obtained by subjecting sisal fibres to a soft mechanical treatment and, on the other hand, nanofibrillated cellulose pulps have been prepared by the application of a high intensity refining process. These pulps were incorporated and homogenously dispersed in cement mortars, and subsequently, the resulting pastes were cured for 28 days. The mechanical performance of the different composites was determined by flexure tests
Claramunt, J.; Ardanuy, M.; Arevalo, R.; Pares, F.; Tolêdo Filho, R. International RILEM Conference on Strain Hardening Cementitious Composites p. 131-138 Presentation's date: 2011-12-12 Presentation of work at congresses
Arevalo, R.; Claramunt, J.; Ardanuy, M.; Aracri, E.; Garcia-Ubasart, J. European and Exhibition Congress on Advanced Materials and Processes Presentation's date: 2011-09-12 Presentation of work at congresses
En este trabajo se han llevado a cabo la preparación y caracterización de nuevos compuestos a base de morteros de cemento reforzados con fibras celulósicas nanofibriladas. El efecto del grado de fibrilación de las fibras sobre las propiedades mecánicas de los composites resultantes se presenta y analiza en base al tamaño final del refuerzo obtenido según la intensidad del tratamiento mecánico aplicado. Para ello se ha partido de fibras de sisal que han sido sometidas a un pulpeado mecánico suave para obtener las pulpas convencionales y a un pulpeado mecánico muy intenso para obtener celulosa nanofibrilada. Las pastas obtenidas han sido incorporadas y dispersadas homogéneamente en morteros de cemento, para posteriormente curar los compuestos durante 28 días. Finalmente se han determinado las propiedades mecánicas de los compuestos con ensayos de flexión. Los resultados indican como las fibras con un alto grado de fibrilación conducen a compuestos con un mayor módulo y resistencia comparados con los obtenidos con las fibras que únicamente han sido sometidas a un pulpeado mecánico suave.
The changes produced in cellulosic fibres when they are subjected to successive drying and rewetting
cycles could have an important impact on the resistance and durability of cement mortar composites
based on these fibres. In this paper, unbleached, oxygen delignificated, semi-bleached, and fully bleached
softwood pulps have been subjected to drying and rewetting cycles and the corresponding dried pulps
characterized. The morphological structures and thermal stabilities were investigated with X-ray diffraction
and thermogravimetric analysis. While the water retention values decrease significantly with drying
and rewetting cycles, an overall increase in the crystallinity index and in the thermal stability was found
in the hornificated pulps. Natural fibres from cotton linters were also studied and the results compared
with the fibres from these softwood pulps.