Conventional fiber-cements are composed of a mixture of cement and asbestos fibers; these composites are strong, inexpensive, fire-resistant, light, and durable materials, which are mainly used in roofing and siding. However, there are health hazards associated with the use of asbestos, which has led to its banning in several countries. Since then, viable replacement alternatives, such as softwood long-fiber pulp (Pinus) and polymer fibers (PP, PVA) have emerged; however, they are not able to cover the full range of asbestos application.
Despite these new technologies being a smart solution, they are costly and involve high energy consumption, making it difficult for developing countries, such as Brazil, to use them. Therefore, Brazilian researchers had to think about other options to replace asbestos. In this context, the use of eucalyptus pulp fibers instead of Pinus fibers arises as a great alternative, as Brazil is a large producer of eucalyptus cellulosic pulps.
Thus, professor Gustavo Tonoli, from the Federal University of Lavras (UFLA), and professors Francisco Rocco Lahr and Holmer Savastano, from the University of Sao Paulo (USP), have studied the use of eucalyptus fibers in cement products and highlighted that these fibers are not only biodegradable and renewable, but they also result in a more competitive and sustainable production of fiber-cement compared to Pinus fibers and lead to energy savings in pulp refining (13, 14).
In addition, after undergoing surface treatment with hydrophilic agents, they significantly improve the durability of the final product. Because short eucalyptus fibers have a greater number of filaments per volume (20 million/g pulp) compared to the long Pinus fibers (5 million/g pulp), they can stop microfissure development and increase flexural strength of the composites.
The work done by professors Tonoli, Lahr, and Savastano has been referenced by researchers from many countries such as Spain, France, India, Austria, and Argentina. This group has also published a study with Spanish professors (15).
Danillo Wisky Silva, under the guidance of professors Lourival Marin Mendes and Rafael Farinassi Mendes, studied the physical and mechanical properties of eucalyptus fibers-reinforced fibercements and the effect of the fiber heat treatment on the aforementioned properties (12).
The research group led by professor João de Almeida Melo Filho from the Federal University of Amazonas (UFAM) is developing a roofing made of jute fiber and ceramic waste, which is a cheaper and more resistant alternative to conventional roof tiles (10, 16).
The alternative tiles are made by alternating layers of mortar (metakaolinite, sand, water, and cement) and layers of jute fiber. The researchers tested 10 mm-thick roof tiles (10); however, the ideal tile thickness had not yet been determined. Tests show that it can resist up to 10 tons, and studies continue aiming at the industrialization of the product. This non-conventional roof tile is a good option for locations where hail storms are common.
Professor João de Almeida Melo Filho advised Mesaque Silva de Oliveira in his Master’s thesis on the use of jute and mauve fibers to produce roof tiles. The results were promising (8).
Professor Lourival Marin Mendes from the Federal University of Lavras (UFLA) advised Danillo Wisky Silva in his Master’s thesis on the use of eucalyptus fibers to produce roof tiles. These, in addition to being eco-friendly, use only 30% to 40% of water mixed with cement as opposed to up to 80% of water in the case of conventional roof tiles (4).
Eco roof tiles using coconut husks have been the topic of studies at the Federal University of Rio de Janeiro (UFRJ) by the research group of Alessandra Magrini and Roberto Schaeffer, who advised Paulo Passos in his PhD thesis (9). Researchers made roof tiles with coconut fibers mixed with recycled paper pulp to produce composites, which were later impermeabilized with asphalt cement. This research also had a social nature, where the authors suggested that the list of recyclable materials collected by pickers should include coconut husks as a way to integrate the community and companies manufacturing the developed products.
The research group of Adeildo Cabral da Silva from the Federal Institute for Technological Education of Ceara (Instituto Federal de Educação, Ciência e Tecnologia do Ceará - IFCE) used coconut fibers added to adobe bricks (11).
The researchers Alcides Lopes Leão, Humberto Fabrizzi de Figueiredo Pupo, Matheus Ferreira and Bibin Mathew Cherian from the Sao Paulo State University (UNESP) studied the properties of composite panels made of thermoplastics from industrial waste reinforced with peach palm waste (shells and sheaths) and good results were obtained for samples with 30% and 40% peach palm waste (6).
Prisms and mini-walls
The researcher Indara Izquierdo, under the guidance of Professor Marcio Antonio Ramalho from the University of Sao Paulo (USP) studied the incorporation of sisal fibers into structural concrete blocks for use in prisms and mini-walls (5). The compressive strength of the mini-wall made with new materials was similar to or higher than that of mini-walls without fibers. Concrete blocks with sisal fibers also showed to be more ductile than conventional materials, which presented an abrupt rupture while the reinforced ones had a ductile breakage and an ability to resist further damage after cracking.
Corn husk is often discarded but it can be mixed with plastic bags or cups to make lighter recyclable products to be used as indoor revetments or plates that do not require high mechanical strength (7). This strategy provides new products with higher mechanical strength while recycling both the plastic material and the corn husk. That has been the focus of studies conducted at the Regional Integrated University of Upper Uruguay and Missions (Universidade Regional Integrada do Alto Uruguai e das Missões - URI) by the research group of Patrícia Siqueira Alves (7).
Different concentrations of banana pseudostem fibers were incorporated in revetment panels for acoustic absorption in the study by Carlos Demarchi, whose master’s thesis was advised by Professor Gilson Morales from the State University of Londrina (UEL) (3). The results of impedance tube test showed that the plates had excellent performance.
Other studies, such as the one from the research group of professor Julio Cesar Moreira (University of Paraiba Valley - UNIVAP), have focused on the study of the mechanical properties of treated banana pseudostem fiber for future use in gypsum composites in civil construction (1).
A study performed by Paulo Soares Cunha and advised by professors Uilame Umbelino Gomes and Rasiah Ladchumananandasivam at the Federal University of Rio Grande do Norte (UFRN) involved the use of gypsum and coconut fiber composites for wall revetments, ceilings, and internal sealings to reduce gypsum waste (2). Researchers from that university tested 500 x 500 x 24 mm composites where external layers were made of gypsum and the inner layer was made of dry coconut fiber. Tests included analysis of physical, mechanical, thermal, and acoustic properties. The results showed that there was a significant gain regarding thermal and acoustic performance; however, mechanical properties – namely compressive and flexural strengths – were lower compared to gypsum only. Nevertheless, the advantage of adding coconut fibers was that they prevented the abrupt breakage of the composite.
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