In this paper we describe a study of the durability of calcium aluminate cement (CAC) reinforced with nano- and micro- cellulose fibers. The nanocelluloses were in the form of nanofibrillated cellulose -obtained from sisal pulp by the application of a high intensity refining process- or as nanocrystals –obtained from acid hydrolysis of pure microcellulose. The setting time (Vicat), strength development (flexural strength), and durability to aging (wet/dry cycles and scanning electron microscopy analysis) were studied. The results have show that the presence of fibers in the matrices modifies the setting times towards reducing them; the mechanical behavior was found better in the fiber CAC matrices compared with CAC mortars. Regarding the durability tests, CAC cementitious systems keep intact the mechanical properties of the fibers. SEM photographs of fracture section show the surface of the fibers with very little state of degradation. These results would indicate that the absence of calcium hydroxide prevents the chemical degradation of cellulose.
Los materiales compuestos ofrecen buenas prestaciones mecánicas con un menor peso que los materiales convencionales, lo que ha extendido su uso a múltiples sectores. Además, el creciente interés sobre los problemas ambientales ha impulsado la evolución hacia materiales más sostenibles, lo que ha potenciado la investigación en refuerzos de fibras naturales y en matrices de biopolímero. Esta tesis se centra en el desarrollo de materiales compuestos sostenibles de polihidroxialcanoato (PHA) y refuerzo de telas no-tejidas de lino, teniendo en cuenta materiales y procesos de bajo impacto ambiental. Sin embargo, con el objetivo de conseguir componentes cada vez más ligeros y con aún mejores propiedades específicas, se emplea la estrategia de reducir el peso de la matriz mediante técnicas de espumado. El hecho de emplear técnicas de espumado para obtener estructuras celulares en la matriz es el valor añadido que diferencia el resultado de los que pueden obtenerse con las técnicas clásicas, y además conlleva un aumento de la competitividad de estos compuestos, puesto que los biopolímeros presentan (actualmente) un mayor coste económico. Sin embargo, la formación de una estructura celular por efecto del espumado lleva a la reducción de las propiedades mecánicas. Esto puede ser contrarrestado mediante el uso de fibras de alta resistencia. En este sentido, el uso de fibras de lino (de alta rigidez y bajo coste) en la forma de estructuras no-tejidas supone también un acercamiento novedoso.El uso de fibras naturales en materiales compuestos presenta dos problemáticas: la interacción fibra/matriz y la sensibilidad frente a la absorción de humedad. Estos inconvenientes pueden minimizarse mediante el uso de métodos sostenibles. En este sentido, la compatibilidad con la matriz puede mejorarse mediante técnicas de plasma que modifican la rugosidad y química superficiales de las fibras (sin afectar sus propiedades generales) con un mínimo uso de productos químicos y sin necesidad de agua. Por otra parte, los tratamientos de ciclado seco/húmedo en agua son una interesante opción para incrementar la estabilidad de las fibras frente a la absorción de agua y los cambios dimensionales sin la necesidad de productos químicos. La efectividad de estos tratamientos ecológicos aplicados al no-tejido se evalúa mediante caracterización mecánica y envejecimiento hidrotérmico en compuestos sólidos de PHA/lino. Por otro lado, la espumabilidad de la matriz se evalúa durante un espumado por extrusión considerando dos estrategias para su mejora: el uso de aditivos para la extensión de cadenas y un enfriamiento rápido en agua. Finalmente, la novedad que presenta un mayor reto (consideradas las limitaciones impuestas tanto por las estructuras de refuerzo como por la espumabilidad de la matriz) es conseguir materiales compuestos celulares reforzados con estructuras optimizadas de lino. Para tal propósito, se evalúa y optimiza un proceso de espumado por disolución de gas por lotes a partir de precursores sólidos. Esta estrategia permite la obtención de materiales compuestos celulares con una reducción de densidad y buenas propiedades específicas.La combinación de propiedades de ambos componentes lleva a la obtención de materiales biodegradables, rígidos y ligeros que presentan buena regularidad en el proceso de espumado, lo que plantea una posible solución para el reemplazo de otros materiales menos sostenibles en automoción, construcción u otras aplicaciones. Por todo esto, en esta tesis se presenta el desarrollo, desde un punto de vista multidisciplinar, de un nuevo método para la obtención de compuestos sostenibles y ligeros.
Ventura, H.; Claramunt, J.; Rodríguez-Pérez , M.; Ardanuy, M. Polymer degradation and stability Vol. 142, p. 129-138 DOI: 10.1016/j.polymdegradstab.2017.06.003 Data de publicació: 2017-06-12 Article en revista
This research analyses the effect of hydrothermal aging on the water uptake and mechanical performance of biocomposites based on a polyhydroxyalkanoate matrix and flax fibre reinforcement in the form of nonwoven (NW) fabrics. The effectiveness of various surface treatments—wet/dry cycling (C), argon plasma (Ar), ethylene plasma and combinations—of these NW in the improvement of the mechanical properties of the composites is also evaluated. The water uptake during aging is analysed at both room temperature and 65 °C. Moreover, the composites are characterised before and after the aging to determine its effects on the morphology, thermal behaviour and tensile properties. It is found that the water diffusion is mainly influenced by the fibre content, and no significant differences are found in the effects of the NW treatments. Although the highest tensile stiffness and strength was found for the composites prepared with the Ar-treated NW, the C treatment is the most effective to prevent the loss of tensile performance after aging.
The aim of this study is to develop a process to produce high-performance cement-based
composites reinforced with flax nonwoven fabrics, analyzing the influence of the fabric
structure—thickness and entanglement—on mechanical behavior under flexural and tensile loadings.
For this purpose, composite with flax nonwoven fabrics with different thicknesses were first prepared
and their cement infiltration was evaluated with backscattered electron (BSE) images
Fernandez-Carrasco, L.; Claramunt, J.; Ardanuy, M. I Congreso Nacional PRE-CONPAT 16. Avances en Control de Calidad, Patología y Recuperación de la Construcción p. 25-26 Data de presentació: 2016-12-02 Presentació treball a congrés
Bacterial polyesters such as polyhydroxyalkanoates (PHAs) are of great interest for a large number of applications both because of their properties and because they come from renewable resources, despite having a higher cost than commodity polymers. Their foaming—although it presents some difficulties—could be an option to increase their competitiveness. In this work, two strategies have been studied to enhance the poly(3-hydoxybutyrate-co-4-hydroxybutyrate) (P3HB4HB) foamability by extrusion foaming. The effect of the cooling system (water-quenching or air-cooling), chain extender (CE) addition and chemical blowing agent (CBA) amount were evaluated. Density, cellular morphology, mechanical and thermal properties were studied. Optimal density reduction was achieved with use of CE and 3–4 wt.% of CBA masterbatch. The most effective strategy on density reduction was the addition of CE, while the water quenching had only a slight influence on the samples in which CE was not present. CE addition decreased the viscosity and the degradation rate of the polymer, thus leading to lighter foams with larger cells but with equal or even slightly better resistance to compressive and tensile stress, in general terms
Ventura, H.; Claramunt, J.; Rodríguez-Pérez , M.; Ardanuy, M. Reunión del Grupo Especializado de Polímeros (GEP) de la RSEQ y RSEF p. 316-317 Data de presentació: 2016-09-05 Presentació treball a congrés
The aim of this work was to provide an investigation of nonwoven geotextiles resistance to the environment. When a geotextile is used in a civil engineering structure, it is intended to perform a particular function for a minimum expected time.It should be chemically and biologically resistant, whilst the assessment of the geotextiles durability and application requires a study. Therefore, in this research, the geotextile resistance was investigated in three directions: the resistance to microbiological attack by soil burial (EN 12 225), the resistance to the oxidation (ISO 13438) and the resistance to liquids (acid and alkali, EN 14030). All the samples were tested before and after the exposure according to standardized methods for determination of mechanical (CBR and strip test) and chemical properties (absorption, adsorption, specific amount of surface charge)
Claramunt, J.; Fernandez-Carrasco, L.; Ventura, H.; Ardanuy, M. Construction & building materials Vol. 115, p. 230-239 DOI: 10.1016/j.conbuildmat.2016.04.044 Data de publicació: 2016-04-16 Article en revista
This experimental research analyzes the mechanical performance and durability of façade
pieces based on Portland cement matrix and flax nonwovens as reinforcement. Two types
of pozzolanic additions (silica fume and metakaolin) combined with nonwovens
subjected to different treatments to decrease their water absorption are analyzed as
potential materials for fiber-cement sheets for building envelopes with high strength and
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
In this study, we analyse the extrusion foaming capabilities of polyhydroxyalkanoates (PHAs) with endothermic chemical blowing agents (CBAs) based on sodium bicarbonate and citric acid. An epoxy functionalized chain extender (CE) is used to improve the melt strength. The effects of CE addition and cooling system (water and air) are evaluated by means of cellular structure characterisation and mechanical properties analysis of PHA foams obtained. The higher density reduction has been obtained with addition of 1% of CE and 3-4% of CBA. The use of the CE has produced higher pores in the cellular structure regardless the cooling system chosen, giving worse cellular structures. However, best mechanical results were performed by air cooled samples with 1 wt.% of CE
Ventura, H.; Claramunt, J.; Navarro, A.; Rodríguez-Pérez , M.; Ardanuy, M. International Conference on Biodegradable and Biobased Polymers p. 1-2 Data de presentació: 2015-10-08 Presentació treball a congrés
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 Data de presentació: 2015-06-22 Presentació treball a congrés
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
López-Gil, A.; Silva-Bellucci, F.; Velasco, D.; Ardanuy, M.; Rodríguez-Pérez , M. Industrial crops and products Vol. 66, p. 194-205 DOI: 10.1016/j.indcrop.2014.12.025 Data de publicació: 2015-01-09 Article en revista
The cellular structure and mechanical properties in compression of starch-based foams filled with naturalreinforcements, such as grape wastes, cardoon wastes and barley straw fibers, have been studied in thiswork. The foams were produced by a microwave foaming process in which water is the plasticizer andat the same time the blowing agent. The use of thermoformed sheets as solid precursors for foamingallowed the production of foamed blocks with cells elongated in the expansion direction and with betterproperties in terms of rigidity and strength than foams produced in previous works by microwave heatingof pellets. Moreover, the natural reinforcements increased not only the rigidity and strength, but also thetoughness of these foams. Finally, the modeling of the compressive modulus using scaling laws showshow the stabilization of the cellular structure by the drying of the polymer matrix increases the rigidityof the solid cell walls. The flexible solid thermoplastic starch based precursor turns while foaming into arigid starch-based foam, which could be suitable either for structural applications, due to its high stiffnessand strength, or for packaging due to its complete biodegradability under controlled conditions
The cellular structure and mechanical properties in compression of starch-based foams filled with natural reinforcements, such as grape wastes, cardoon wastes and barley straw fibers, have been studied in this work. The foams were produced by a microwave foaming process in which water is the plasticizer and at the same time the blowing agent. The use of thermoformed sheets as solid precursors for foaming allowed the production of foamed blocks with cells elongated in the expansion direction and with better properties in terms of rigidity and strength than foams produced in previous works by microwave heating of pellets. Moreover, the natural reinforcements increased not only the rigidity and strength, but also the toughness of these foams. Finally, the modeling of the compressive modulus using scaling laws show show the stabilization of the cellular structure by the drying of the polymer matrix increases the rigidity of the solid cell walls. The flexible solid thermoplastic starch based precursor turns while foaming into arigid starch-based foam, which could be suitable either for structural applications, due to its high stiffness and strength, or for packaging due to its complete biodegradability under controlled conditions
Starch-based foamed blocks reinforced with natural fillers and with a high potential for being applied as bioderived and biodegradable shaped protective packaging were produced in this work. The use of natural fillers as reinforcement in biopolymers represents a successful strategy widely employed mainly due to their chemical compatibility. Nevertheless, their effect in the mechanical properties of foamed biopolymers such as starch is still uncertain because they not only affect the properties of the solid polymer matrix within the cell walls and struts but also the main mechanisms comprising a foaming process such as nucleation, expansion and stabilization of the cellular structure. Moreover, the homogeneities of the cellular structures obtained are usually poor which complicates even more the analyses. This work aims at providing more insight in the relation cellular structure-mechanical properties in starch-based polymer foams reinforced with natural fillers by characterizing their cellular structure in detail and relating them with their mechanical properties measured in compression. In addition, these starch-based foams were produced by a foaming process consisting on the interaction of microwaves with the polymer matrix, which is especially interesting when water acts as the blowing agent as in this work. The loose of water during the foaming process make the properties of the polymer within the cells walls and struts evolve, which leads to obtain brittle foams from highly flexible solid precursors
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.
The aim of this paper is to explore the potential of oil palm frond fibers (OPFf) for technical applications such as composite reinforcement. For this purpose, fibers obtained from frond wastes were subjected to various chemical treatments with NaOH and chemically and morphologically characterized. Afterward, composites of poly-lactic acid matrix and nonwoven matts made with the treated and the untreated OPFf were prepared and the mechanical properties tested. It was found that the alkaline treatment was effective for increasing the wettability of the fibers leading to composites with a good-balanced between lightness and toughness for potential applications in packaging or automotive industries.
López, A.; Rodríguez-Pérez , M.; de Saja, J.; Bellucci, F.S.; Ardanuy, M. Polímeros: Ciência e Tecnologia Vol. 24, p. 36-42 DOI: 10.4322/polimeros.2014.054 Data de publicació: 2014-07-14 Article en revista
Biodegradable polymers are starting to be introduced as raw materials in the food-packaging market. Nevertheless, their price is very high. Starch, a fully biodegradable and bioderived polymer is a very interesting alternative due to its very low price. However, the use of starch as the polymer matrix for the production of rigid food packaging, such as trays, is limited due to its poor mechanical properties, high hidrophilicity and high density. This work presents two strategies to overcome the poor mechanical properties of starch. First, the plasticization of starch with several amounts of glycerol to produce thermoplastic starch (TPS) and second, the production of biocomposites by reinforcing TPS with promising fibers, such as barley straw and grape waste. The mechanical properties obtained are compared with the values predicted by models used in the field of composites; law of mixtures, Kerner-Nielsen and Halpin-Tsai. To evaluate if the materials developed are suitable for the production of food-packaging trays, the TPS-based materials with better mechanical properties were compared with commercial grades of oil-based polymers, polypropylene (PP) and polyethylene-terphthalate (PET), and a biodegradable polymer, polylactic acid (PLA)
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
Ventura, H.; Ardanuy, M.; Capdevila, F.; Cano, F.; Tornero, J. Journal of the Textile Institute Vol. 105, num. 10, p. 1065-1075 DOI: 10.1080/00405000.2013.874628 Data de publicació: 2014-06-26 Article en revista
The main objective of this paper is to study the effects of the processing parameters of the needle-punching machine and the interactions between them on some physico-mechanical properties of interest of nonwoven (NW) fabrics. For this purpose, a fractional factorial design has been planned with two levels for each factor: feeding speed, delivery speed, stroke frequency, penetration depth and gap between plates. Sixteen NW fabrics were obtained from polyester fibre and characterized by tensile strength and stiffness for mechanical behaviour and air permeability as physical properties of interest in some technical applications. The results have been subjected to statistical analysis in order to find the effects of the processing variables and the interactions between them on the fabric properties. It was possible to find the effects of the five processing parameters studied on the thickness, fabric mass, stiffness, tensile strength and air permeability of the obtained needle-punched fabrics
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.
This paper presents the development of an industrially viable procedure for the fabrication of durable insecticide textiles based on the sol-gel technique. Permethrin was incorporated on cotton fabrics by a silicon oxide nanocoating applied by conventional padding followed by curing. The effect of the sol-gel process parameters, such as silica solid content and the permethrin/tetraethyl orthosilicate (TEOS) ratio on the insecticide activity and on the textile properties of the resulting fabrics was evaluated. The application of the nanosol coating results in textiles with a high anti-mosquito effect without altering their flexibility and softness. Moreover, this method allows the insecticide content to be controlled by simply adding the proper amount of it to the coating bath. The washing fastness was assessed on a textile with a permethrin loading close to 500mg/m2 of fabric showing a good insecticide effect even after 50 washing cycles.
This paper presents the development of an industrially viable procedure for the fabrication of durable insecticide textiles based on the sol–gel technique. Permethrin was incorporated on cotton fabrics by a silicon oxide nanocoating applied by conventional padding followed by curing. The effect of the sol–gel process parameters, such as silica solid content and the permethrin/tetraethyl orthosilicate (TEOS) ratio on the insecticide activity and on the textile properties of the resulting fabricswas evaluated. The application of the nanosol coating results in textiles with a high anti-mosquito effect without altering their flexibility and softness.Moreover, this method allows the insecticide content to be controlled by simply adding the proper amount of it to the coating bath. The washing fastness was assessed on a textile with a permethrin loading close to 500 mg/m2 of fabric showing a good insecticide effect even after 50 washing cycles
The weight of textile components in automobiles is expected to rise to 35 kg by 2020, and the average lifetime of a vehicle is about 12 years. Car seats are the most important part of the interior decoration, and polyester is the most widely used material in car seat covering. Abrasion resistance tests are used to quantify the duration of car seat upholstery in normal usage, and this is one of the most important requirements. Several testing methods, standards, and car producer specifications have been developed to define the abrasion resistance of specified materials, and pre-tests have been taken to identify parameters for this research. The objective of this study was to compare three abrasion tests with different abrasive elements using car seat upholstery structures. Comparison among abrasion testers and abrasive papers shows statistically significant differences. The relationship between weight loss and abrasion cycles can be modelled by regression equations
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.
Procedimiento para la obtención de un tejido con efecto insecticida.
La presente invención se refiere a un procedimiento para la obtención de un tejido con efecto insecticida. Asimismo, la presente invención se refiere al uso de dicho tejido para confeccionar prendas y artículos textiles.
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