The Experts below are selected from a list of 57 Experts worldwide ranked by ideXlab platform
Carlos Negro - One of the best experts on this subject based on the ideXlab platform.
-
Hatschek Process as a way to valorize agricultural wastes effects on the Process and product quality
Sustainable and Nonconventional Construction Materials using Inorganic Bonded Fiber Composites, 2017Co-Authors: Elena Fuente, Angeles Blanco, Rocio Jarabo, Carlos NegroAbstract:Abstract 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.
-
optimal use of flocculants on the manufacture of fibre cement materials by the Hatschek Process
Construction and Building Materials, 2010Co-Authors: Angeles Blanco, Elena Fuente, Alvaro Alonso, Carlos NegroAbstract:Abstract This paper is focused in the description of a new real-time methodology for flocculant selection in the fibre-cement manufacture based on studying flocculation and floc properties with a focused beam reflectance measurement (FBRM). Results were supported and confirmed by particle vision and measurement (PVM) analysis. Opposite effects of polyacrylamides characteristics on fibre cement flocculation and on final product were found: charge density resulted in increased product strength when dosage of polymer was low but decreased it at high dosages. The feasibility of using artificial neural networks (ANNs) to predict mechanical properties of fibre cement composites from the flocculation data obtained by in-line measurement in a Hatschek machine by the FBRM sensor is reported.
-
polyacrylamide induced flocculation of a cement suspension
Chemical Engineering Science, 2006Co-Authors: Carlos Negro, Angeles Blanco, Luis Sanchez, Elena Fuente, Julio TijeroAbstract:Abstract 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 Ca 2 + 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.
-
methodology for flocculant selection in fibre cement manufacture
Cement & Concrete Composites, 2006Co-Authors: Carlos Negro, Angeles Blanco, Ignacio San Pio, Julio TijeroAbstract:Abstract 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.
-
influence of flocculant molecular weight and anionic charge on flocculation behaviour and on the manufacture of fibre cement composites by the Hatschek Process
Cement and Concrete Research, 2005Co-Authors: Carlos Negro, Angeles Blanco, Luis Sanchez, Elena Fuente, Julio TijeroAbstract:Abstract 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.
L Soriano - One of the best experts on this subject based on the ideXlab platform.
-
use of highly reactive rice husk ash in the production of cement matrix reinforced with green coconut fiber
Industrial Crops and Products, 2013Co-Authors: C L Pereira, Holmer Savastano, J Paya, S F Santos, M V Borrachero, J Monzo, L SorianoAbstract:Abstract This study evaluated the influence of partial replacement of Portland cement by rice husk ash (RHA) to enable the use of green coconut husk fiber as reinforcement for cementitious matrix. The use of highly reactive pozzolanic ash contributes for decreasing the alkaline attack on the vegetable fiber, originated from waste materials. The slurry dewatering technique was used for dispersion of the raw materials in aqueous solution, followed by vacuum drainage of water and pressing for the production of pad composites, as a simplified simulation of the Hatschek Process for industrial manufacture. Five formulations were evaluated, two of them without any mineral additions. One of the mixtures served as a reference (without green coconut fibers) and the remaining ones were reinforced with the green coconut fibers (5% by weight of binder) and with the content of Portland cement replacement by RHA equal to 0, 30, 40 and 50%. The composites were analyzed at 28 days of age and after aging by immersion in warm water (65 °C), which lasted for 28 additional days. Physical and mechanical tests were applied for assessment of the performance of composites. Thermogravimetric analysis was used to observe the consumption of portlandite and chemically combined water content in the hydrated products for pastes presenting the same levels of Portland cement replacement by RHA (i.e., 0–50%) and with the water/binder ratio kept constant and equal to 0.5. The mechanical performance evaluated by bending test after 28 days reached the MOR of 15.7 MPa after the accelerate aging, for the composites reinforced with the green coconut fiber and with high levels of Portland cement replacement by RHA demonstrating that the use of green coconut fiber for reinforcement can be very promising for the production of binary cement based matrix. The thermogravimetry showed that the replacement of Portland cement by the RHA helped in maintaining the mechanical behavior of the green coconut fiber in the composite subjected to the accelerated aging tests, and resulted in improved mechanical performance, providing a lightweight composite.
Angeles Blanco - One of the best experts on this subject based on the ideXlab platform.
-
Hatschek Process as a way to valorize agricultural wastes effects on the Process and product quality
Sustainable and Nonconventional Construction Materials using Inorganic Bonded Fiber Composites, 2017Co-Authors: Elena Fuente, Angeles Blanco, Rocio Jarabo, Carlos NegroAbstract:Abstract 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.
-
optimal use of flocculants on the manufacture of fibre cement materials by the Hatschek Process
Construction and Building Materials, 2010Co-Authors: Angeles Blanco, Elena Fuente, Alvaro Alonso, Carlos NegroAbstract:Abstract This paper is focused in the description of a new real-time methodology for flocculant selection in the fibre-cement manufacture based on studying flocculation and floc properties with a focused beam reflectance measurement (FBRM). Results were supported and confirmed by particle vision and measurement (PVM) analysis. Opposite effects of polyacrylamides characteristics on fibre cement flocculation and on final product were found: charge density resulted in increased product strength when dosage of polymer was low but decreased it at high dosages. The feasibility of using artificial neural networks (ANNs) to predict mechanical properties of fibre cement composites from the flocculation data obtained by in-line measurement in a Hatschek machine by the FBRM sensor is reported.
-
polyacrylamide induced flocculation of a cement suspension
Chemical Engineering Science, 2006Co-Authors: Carlos Negro, Angeles Blanco, Luis Sanchez, Elena Fuente, Julio TijeroAbstract:Abstract 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 Ca 2 + 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.
-
methodology for flocculant selection in fibre cement manufacture
Cement & Concrete Composites, 2006Co-Authors: Carlos Negro, Angeles Blanco, Ignacio San Pio, Julio TijeroAbstract:Abstract 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.
-
influence of flocculant molecular weight and anionic charge on flocculation behaviour and on the manufacture of fibre cement composites by the Hatschek Process
Cement and Concrete Research, 2005Co-Authors: Carlos Negro, Angeles Blanco, Luis Sanchez, Elena Fuente, Julio TijeroAbstract:Abstract 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.
C L Pereira - One of the best experts on this subject based on the ideXlab platform.
-
use of highly reactive rice husk ash in the production of cement matrix reinforced with green coconut fiber
Industrial Crops and Products, 2013Co-Authors: C L Pereira, Holmer Savastano, J Paya, S F Santos, M V Borrachero, J Monzo, L SorianoAbstract:Abstract This study evaluated the influence of partial replacement of Portland cement by rice husk ash (RHA) to enable the use of green coconut husk fiber as reinforcement for cementitious matrix. The use of highly reactive pozzolanic ash contributes for decreasing the alkaline attack on the vegetable fiber, originated from waste materials. The slurry dewatering technique was used for dispersion of the raw materials in aqueous solution, followed by vacuum drainage of water and pressing for the production of pad composites, as a simplified simulation of the Hatschek Process for industrial manufacture. Five formulations were evaluated, two of them without any mineral additions. One of the mixtures served as a reference (without green coconut fibers) and the remaining ones were reinforced with the green coconut fibers (5% by weight of binder) and with the content of Portland cement replacement by RHA equal to 0, 30, 40 and 50%. The composites were analyzed at 28 days of age and after aging by immersion in warm water (65 °C), which lasted for 28 additional days. Physical and mechanical tests were applied for assessment of the performance of composites. Thermogravimetric analysis was used to observe the consumption of portlandite and chemically combined water content in the hydrated products for pastes presenting the same levels of Portland cement replacement by RHA (i.e., 0–50%) and with the water/binder ratio kept constant and equal to 0.5. The mechanical performance evaluated by bending test after 28 days reached the MOR of 15.7 MPa after the accelerate aging, for the composites reinforced with the green coconut fiber and with high levels of Portland cement replacement by RHA demonstrating that the use of green coconut fiber for reinforcement can be very promising for the production of binary cement based matrix. The thermogravimetry showed that the replacement of Portland cement by the RHA helped in maintaining the mechanical behavior of the green coconut fiber in the composite subjected to the accelerated aging tests, and resulted in improved mechanical performance, providing a lightweight composite.
Julio Tijero - One of the best experts on this subject based on the ideXlab platform.
-
polyacrylamide induced flocculation of a cement suspension
Chemical Engineering Science, 2006Co-Authors: Carlos Negro, Angeles Blanco, Luis Sanchez, Elena Fuente, Julio TijeroAbstract:Abstract 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 Ca 2 + 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.
-
methodology for flocculant selection in fibre cement manufacture
Cement & Concrete Composites, 2006Co-Authors: Carlos Negro, Angeles Blanco, Ignacio San Pio, Julio TijeroAbstract:Abstract 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.
-
influence of flocculant molecular weight and anionic charge on flocculation behaviour and on the manufacture of fibre cement composites by the Hatschek Process
Cement and Concrete Research, 2005Co-Authors: Carlos Negro, Angeles Blanco, Luis Sanchez, Elena Fuente, Julio TijeroAbstract:Abstract 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.
