Tijolos ecológicos reforçados: utilização de solo eólico-cimento sob adição de sílica da casca de arroz e fibras vegetais de capim annoni.

Abstract

The objective of this study is to develop eco-friendly hollow bricks using a mixture of aeolian soil, cement, and rice husk ash silica (RHA), with and without the incorporation of annoni grass fibers. Initially, preliminary compressive strength tests were conducted on cylindrical specimens compacted using the Standard Proctor method to assess the mechanical behavior of the materials and determine the optimal moisture content for brick fabrication. Following this, to incorporate annoni grass fibers into the hollow ecofriendly bricks, different fiber lengths (1,5 cm, 2,5 cm, and 3,0 cm), surface treatments (soaking in an RHA-water solution at a 2:1 ratio and soaking in a diluted caustic soda solution with a 6% concentration), and fiber contents of 0,15%, 0,25%, and 0,50% as partial substitutes for soil were evaluated. For the fabrication of the hollow bricks, a steel mold was made according to the dimensions recommended by standard ABNT NBR 8491 (2012) for type A bricks, with measurements of 20,0 cm x 10,0 cm x 5,0cm (length x width x height) and a spacing between holes of 5,0 cm. Subsequently, five batches of eco-friendly hollow bricks were manufactured, corresponding to mixtures of aeolian soil-cement-RHA without fibers (SF) or with (F) the addition of annoni grass fibers: T80-5-15-SF, T80-10-10-SF, T79,85-10-10-0.15F, T80-15-5-SF, and T79,85-15-5-0.15F. After a curing period in a humid chamber, the bricks were subjected to laboratory tests such as water absorption, compressive strength, flexural tensile strength by three-point bending, and durability through wet-dry cycles. Based on preliminar tests, the components (aeolian soil, cement, and RHA) proved viable for the production of eco-friendly hollow bricks, with optimal moisture contents between 9% and 10% for the best compressive performance. As for the annoni grass fibers, they were foundsuitable for use in eco-friendly hollow bricks, particularly when used in 2,5 cm lengths, treated with caustic soda, and at a content of 0,15% as a partial replacement for soil. The fiber incorporation contributed to an increase of up to 31% in flexural tensile strength, in addition to meeting the requirements established by ABNT NBR 8491 (2012), with average water absorption values below 20%. Although the fibers caused an average reduction of approximately 9,68% in compressive strength, the resulting values remained above 2,0 MPa, as specified by the ABNT standard. Finally, through this research, it was concluded that the mixtures 79,85%-15%-5%-0,15% and 80%-15%-5%-0%, composed of aeolian soil-cement-RHA-annoni grass fibers, showed promising results in terms of mechanical strength, water absorption, and durability to wear. These mixtures are suitable for the production of eco-friendly hollow bricks and represent technically and sustainably viable alternatives due to the use of alternative materials in their composition. Keywords: Hollow ecological bricks. Wind-blown soil-cement-silica from rice husk ash. Vegetable fibers from annoni grass.