In order to limit climate change by achieving goals of cutting emissions down to net-zero by 2050, stronger efforts are needed to reduce the whole life cycle emissions of buildings. Integrating residual bio-based and earth-based solutions to concrete seems to stand out in the sector since these solutions have the potential of lowering materials embodied emissions, and enhancing building thermal performance. However, it is still unclear how environmentally beneficial bio-based and earth-based materials are and how they behave mechanically when they are both integrated into concrete. In order to know their potential applications in the sector, this study aims to evaluate and compare the mechanical performance and environmental profile of Earth-based Bamboo Bio-Concretes (EBBCs) with different earth fractions as partial replacements of the cementitious matrix, by evaluating its Greenhouse Gas (GHG) emissions. For that, it was considered the use of only bio-based aggregates (bamboo waste) instead of mineral ones at a fixed volume fraction of 45%. The methodology involved the: processing and characterization of earth and bamboo; EBBCs dosage study and mechanical testing; consideration of fixed proportions of binders of 30:30:40 (cement: metakaolin: fly ash) which were replaced gradually by earth in the volume fractions of 10%, 15%, and 20%. The Life Cycle Assessment (LCA) was used for accounting GHG emissions. LCA scope was from cradle-to-gate considering biogenic carbon methodology and avoided impacts of incinerating bamboo waste. A sensitive analysis was performed to evaluate the impact of transport distances variation of bamboo waste. Mechanical results point to an increase in EBBCs compressive strength with the increase of earth content until 15% of cementitious matrix replacement. LCA results showed negative embodied GHG emissions in all mixtures with an average of -115,7 kgCO2-eq/m3 mainly due to the high biomass content in mixtures. The increase of earth content from 0% to 20% in the mixtures reduced emissions by 59,7 kgCO2-eq/m3 since the binder’s content was reduced. With that, EBBC seems to be a promising innovative material to help achieve net-zero carbon emission targets and a circular pathway in the building and construction sectors.
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.
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