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RESUMO Esta pesquisa experimental tem como objetivo produzir bioconcretos de casca de arroz (BCCs) com uma matriz de misturas ternárias de cimento, cinza da casca de arroz e cinza volante. A primeira etapa consistiu na avaliação da influência de um aditivo superplastificante e um aditivo polifuncional no comportamento reológico de pastas cimentícias. O objetivo dessa etapa foi testar diferentes teores dos aditivos a fim de desenvolver uma pasta fluida que, após a adição de altas frações volumétricas de casca de arroz (CA), permita obter BCCs leves que possuam trabalhabilidade adequada para adensamento por vibração mecânica. Realizou-se uma trituração e um tratamento químico da CA, no intuito de melhorar sua aderência com a matriz. Os resultados experimentais mostram que o aditivo do tipo PF apresentou melhor compatibilidade com a matriz a um teor de 0,3%. Assim, os BCCs produzidos apresentaram-se coesos e sem segregação, com espalhamento de 210 ± 30 mm. A massa específica seca e a resistência à compressão foram determinadas aos 28 dias de idade. Com os resultados obtidos, os BCCs apresentaram massa específica entre 1000 e 1300 kg/m3 e resistência à compressão superiores a 8,0 MPa, indicando a possibilidade de utilização na produção de painéis leves e autoportantes.

Bio-concretes are receiving special attention in recent research as an alternative for climate change mitigation due to their low carbon footprints. Different bio-based materials can be used, e.g., wood shavings, bamboo, rice husk, and coconut. However, various methodological parameters can influence the carbon footprint of bio-based materials, especially bio-concretes, like biogenic carbon, amount of carbon in dry matter, rotation period of bio-aggregates, and type of cementitious materials. It is important to have easier ways of estimating the carbon footprint of bio-concretes, using parameters and data easily available. This research aims to evaluate the (1) carbon footprint of different mixtures of three bio-concretes (wood bio-concrete - WBC, bamboo bio-concrete - BBC and rice husk bio-concrete - RBC), and the (2) development of GHG emissions curves for bio-concretes specification based on easily available data (such as density, biomass content, and compressive strength). Based on experimental data, the carbon footprint was performed using the Life Cycle Assessment (LCA) methodology. In order to extend the findings of this study, the context of the following four countries was evaluated: Brazil, South Africa, India, and China. In addition, the replacement of Portland cement for Supplementary Cementitious Materials (SCMs) are evaluated hypothetically. The results show that the increase of biomass content in bio-concretes and the replacement of Portland cement by SCMs leads to a radical decrease in life cycle GHG emissions. The percentage of carbon in biomass is a critical factor for reducing the carbon footprint. The WBC was the biomass that performed better for this parameter. The presented GHG emissions curves can be a useful way to estimate the carbon footprint of bio-concretes and can be adapted to other kinds of bio-concretes and countries.

The wood bio-concrete (WBC) production is a solution for the advancement of sustainable construction, since it has the potential to recycle waste in the form of shavings generated in wood processing and stock CO2, contributing for climate change reduction. However, the chemical incompatibility between plant biomass and cementitious matrix leads to the need for previous treatment of wood shavings to application in bio-concretes. In the present study, one heat treatment and two alkaline treatments with immersion in Ca (OH)2 solution were evaluated using Life Cycle Assessment (LCA) methodology. The environmental modeling was performed by SimaPro, using the Ecoinvent database, and primary data collected in the laboratory. The potential environmental impacts were related to the compressive strength of produced WBC (in MPa) as an ecoefficiency indicator. Considering the functional unit of mechanical performance, the alkaline treatment with two immersions was the one that generated less environmental impacts.