Global warming and climate change are a worldwide concern and researchers are joining efforts towards finding solutions for a problem that affects both our and future generations. The manufacturing of conventional construction materials has a significant impact on the environment not only because it consumes oxygen and releases several pollutants into the atmosphere but also because the solid waste from these materials are difficult to recycle and may damage soil and underground water.
In this context, alternative materials and recycling combined provide options to replace conventional materials. However, despite the general population recognizing the need for a change, people are skeptical about the durability and safety of alternative materials. Thus, researchers must assure the population that renewable materials:
- (1) may be an excellent alternative to their non-renewable counterparts,
- (2) are safe to use when they comply with current standards for a specific application, and
- (3) may add value by providing strength, thermal/sound insulation, beauty, and durability
Natural fibers are among alternative renewable materials and their use in composites is ancient. As Brazil has many natural resources, making use of those resources to create new renewable products is a clever strategy. Recent studies by some Brazilian researchers are focusing on the use of plant fiber-reinforced composites for various construction applications.
To this end, the knowledge about the chemical, mechanical, thermal, and morphological properties of these composites and the understanding about how they affect composite processing, performance, and durability is very important to direct their use to the appropriate application (2-4, 8, 21). Other studies have focused on the surface modification of different plant fibers with the purpose of improving the adhesion between the components of fiber-reinforced composites and providing better performance and longer life to the final products (1, 12, 13, 26, 27).
Some of the applications for non-conventional construction materials being studied in Brazil include: fiber-Cement (24, 26, 27, 28), roofing (6, 15, 16, 19, 30), bricks (23), panels (9), prisms and mini-walls (8), indoor revetments (1, 3, 4, 10). These new materials, which are plant fiber composites developed to meet certain requirements, also bring charm to the architectural project and add value to the final product.
They are not only environmentally friendly and renewable, but they also have many advantages compared to synthetic fiber-reinforced materials, to wit: plant fibers grow fast and in almost any part of the Brazilian territory, are inexpensive, may be found as waste, save energy, are not harmful to humans, prevent erosion, have low density, are biodegradable, avoid formation of fissures in composites, and increase tensile strength of floorings and concrete pavements.
However, they also present some disadvantages, such as low durability (if untreated), variability in properties, and weak adhesion to numerous matrices.
Current Research Supporting Engineering Efforts
As research on this topic advances, conventional construction materials are slowly being replaced with their non-conventional counterparts. Currently, there are several options for eco-friendly materials available in the market and some of them are being used in eco-houses as part of social programs in Brazil.
For example, in the municipality of Lages (SC), Brazil, affordable houses of approximately 42 meters squared are being built with recycled materials (17, 18). Each house costs on average BRL 7,000 (~ US $2,072) and takes only 15 days to be built compared to 3 months for a conventional house. In addition, these eco-houses lead to savings on the order of BRL 13,000 (~ US $3,848).
Public workers from the municipality of Lajes are the ones making the bricks from soil cement mixed with biomass ashes (from waste generated by the wood industry) and glass sand. Styrofoam glue is used in place of mortar for brick fixation, which is a cheaper and environmentally friendly alternative. The roof is made of recycled windshields; windows and doors are also made from recycled materials.
The research group of Professor José Ubiragi de Lima Mendes from the Federal University of Rio Grande do Norte (UFRN) is also involved in meeting the needs of low income communities by producing alternative unburnt bricks made of soil-cement reinforced with coconut fibers (14). The results are promising and indicate that the bricks can be produced in a mechanical press or at the construction site using a manual mold press. The values obtained for density, water absorption, axial compressive strength, and acoustic and thermal insulation of the bricks were considered good.
In the same way natural fibers have been used to make environmentally friendly construction products, using construction waste to produce natural resources closes the sustainability cycle. Considering that two thirds of solid wastes in Brazil come from civil construction, finding ways to reuse those residues is of utmost importance.
With this purpose, the researcher Marcos Canto Machado from the Luiz de Queiroz College of Agriculture of the University of Sao Paulo (ESALQ/USP) focused on the recycling of construction wastes (11,20).
They started by screening stones, bricks and concrete pieces, which were milled, and then separated according to particle size. Usually, larger particles are used in infrastructure works, which are only a small portion of this waste. The ESALQ researchers aimed to also reuse the finer particles and analized their use in the fertilization of plant crops and landscaping works. Before being applied to the soil, milled waste was checked for toxic elements and agronomical properties. After that, necessary corrections were made so that the waste would promote plant development.
In addition to the aforementioned materials, this study also included waste from gypsum because they contain sulphates, which can reach water bodies or form toxic substances. The new product was applied to emerald grass with promising results and plant development was similar to the one when a traditional soil was used.
These are only some of the numerous studies being carried out in Brazil. Considering that financial resources in this country are limited, making the most of its many natural resources and its researchers’ creativity may be the solution for the challenges imposed by the sustainability in Brazil.
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