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Circular Economy (CE) is progressively attracting interest from construction sector stakeholders to support the development of products with higher amounts of recovered materials in order to decrease greenhouse gas (GHG) emissions. Concrete is one of the most used materials in the world and can be produced using waste as raw materials, including, bio-based sources, from both agricultural and forest activities. This research aims to assess the GHG emissions in the life cycle of innovative rice husk bio-concretes (RBC) in which rice husk (RH) and rice husk ash (RHA) are used as circular solutions. Four RBC, considering ordinary Portland cement replacement by 8% of RHA and, different contents of sand substitution by RH (0; 5 and 10%), were assessed. The Life Cycle Assessment (LCA) methodology was used, with a cradle-to-gate scope, using the GWPbio method, that contemplate the influence of biogenic carbon on the emissions reduction. Different transportation scenarios were evaluated considering the RBC production in different Brazilian regions. The service life of RBC in terms of carbon stock was also evaluated. Two carbon-performance indicators are also evaluated in terms of RBC compressive strength and thermal conductivity values. As the main conclusion, cement replacement by RHA alongside with sand replacement by RH are promising strategies to produce bio-concretes for specific applications, such as panels, partitions and façade elements, and to reduce its GHG emissions. However, this benefit varies according to RH availability, transport efficiency and RBC service life. The RBC can be considered a potential alternative for concrete industry, for specific applications, to reduce GHG emissions and can be developed where rice waste is an available source. This study contributes by presenting a new material and a methodology for the evaluation of life cycle GHG emissions of bio-concretes, which can help to promote a circular construction sector.

This experimental study aims to present the behavior of cement composites containing rice husk ash over time previously undergone high thermal curing. A specific initial thermal curing up to 85°C was designed to trigger delayed ettringite formation (DEF) as well as a specific exposure environment, by water immersion at 38°C, over one year. Expansion measurements and microstructural analyses were performed to evaluate the level of attack and the integrity of mortars and concretes. To complement the study, mechanical properties of concretes were assessed to detect the level of damages by delayed ettringite formation expansion. Mortar performed differently from concrete, bringing risks of mistaken conclusions about admixture performance. Anyway, concrete tests have indicated that rice husk ash was able just to reduce the level of expansions, nonetheless, the contents were not enough to mitigate completely the generated expansions and avoid delayed ettringite formation and, consequently, damage. Highlights • The potential of rice husk-ash to mitigate DEF was explored. • A comparison between the behavior of mortar and concrete mixtures was evaluated. • The expansions, mechanical properties and microstructure analyses were studied. • Mortar and concrete performed different. • The admixture of rice husk-ash did not play enough mitigative performance for DEF at content of 8% by cement weight.

Ciência -Estudo e ensino -Brasil. 2. Ciência -Aspectos sociais. 3. Ciência -Política e governo. I. Dalazoana, Karine. CDD 303.483 Elaborado por Maurício Amormino Júnior -CRB6/2422 O conteúdo dos artigos e seus dados em sua forma, correção e confiabilidade são de responsabilidade exclusiva dos autores. 2018 Permitido o download da obra e o compartilhamento desde que sejam atribuídos créditos aos autores, mas sem a possibilidade de alterá-la de nenhuma forma ou utilizá-la para fins comerciais. www.atenaeditora.com.br