Like other sectors of the economy, civil construction faces an important challenge: to progressively reduce greenhouse gas emissions and become increasingly sustainable. In this sense, there are efforts in the scientific community to develop construction materials that have a positive environmental impact at all stages of the building process, starting with the extraction of raw materials, going through the use of the buildings and reaching the recycling of waste at the end of the life cycle of the product. To this end, one of the strategies being explored is the incorporation of natural raw materials, such as raw earth and biomass, into construction materials.
In an article recently published in the journal Construction and Building Materials, a Brazilian scientific team reports the development and study of mortars based on raw earth and plant biomass residues (bamboo particles) with potential for use as internal wall plaster. In addition to analyzing the properties of these mortars, the authors evaluated their environmental impact, mainly in relation to the carbon dioxide emissions involved in their preparation, use and disposal.
“The main contribution of this work is to show the feasibility of producing mortars based on locally available natural resources (raw earth and plant biomass – bamboo) in the construction of a portfolio of low carbon and low energy consumption constructive solutions”, says Romildo Dias Toledo Filho, professor of the Civil Engineering Program at Coppe, the postgraduation and research institute in Engineering at the Federal University of Rio de Janeiro (UFRJ), who led the work.
To produce the mortars, the scientific team used raw earth, bamboo particles, hydrated lime, Portland cement and natural sand, among other ingredients. Bamboo particles were obtained from waste from the furniture sector in the state of Rio de Janeiro and processed to obtain fibers of a few hundred micrometers in diameter and up to 2 cm in length.
Four types of mortar were produced: one without bamboo and the others with different proportions of particles (3, 6 and 9% of the total volume). In addition to studying its physical, mechanical and thermal properties, the authors quantified the greenhouse gas emissions involved in the mortar’s life cycle. Using well-established methodologies, the researchers evaluated the developed earth mortars and compared them with conventional mortars. The study considered the entire life cycle of the material.
The research showed good results for earth and bamboo mortars and explained the weight of each factor in the carbon emissions involved in the process, pointing out ways to reduce them even more. Earth mortars, especially those with a higher proportion of bamboo, presented lower emissions than conventional mortars due to the carbon stock of bamboo. In fact, vegetal biomass extract carbon dioxide from the atmosphere through photosynthesis and use it to grow. When this biomass is incorporated into a mortar, the carbon remains stored and its emission is avoided. This environmental gain is enhanced when residues from biomass processing are used as a source of raw material, as occurred in this work.
In addition, density, thermal conductivity and resistance tests showed that earth mortars with bamboo, especially the one containing 6% biomass, can perform very well as plaster for internal walls of buildings, as they have adequate adhesion and resistance, and improve the energy efficiency of the environments. “Earth mortars that incorporate plant biomass present the peculiarity of open porosity, and this characteristic gives them the potential to act as a coating and passive material for hygrothermal regulation of the internal microclimate of the environments, making them more salubrious, providing better conditions of health to the occupants and reducing energy consumption for artificial air conditioning”, explains Professor Romildo.
The work was developed within the PhD in Civil Engineering of Rayane de Lima Moura Paiva, with funding from CNPq and FAPERJ and guidance from Professor Romildo and Professor Lucas Rosse Caldas. The study is part of a research line on earth and biomass mortars that is underway at Coppe’s Sustainable Materials Center in partnership with a group from ETH Zürich (Switzerland).
Scientific article reference: Potentiality of earth-based mortar containing bamboo particles for GHG emissions reduction. Rayane de Lima Moura Paiva, Lucas Rosse Caldas, Adriana Paiva de Souza Martins, Romildo Dias Toledo Filho. Construction and Building Materials. Volume 317, 24 January 2022, 125971. https://doi.org/10.1016/j.conbuildmat.2021.125971
Author contact: Prof. Romildo Dias Toledo Filho – toledo@coc.ufrj.br