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Rheological and mechanical properties of cementitious materials with the addition of Biochar: A strategy to obtain 3D printability.

Juan Felipe Carvajal Pardey

Rheological and mechanical properties of cementitious materials with the addition of Biochar: A strategy to obtain 3D printability.

Rel. Luciana Restuccia, Jean Marc Christian Tulliani, Devid Falliano. Politecnico di Torino, Corso di laurea magistrale in Ingegneria Civile, 2021

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CO2 emissions in recent years have reached the highest levels historically, with peaks in 2018 and stabilization in 2020 due to the pandemic. Construction and materials production is among the most contributing industries to the greenhouse gas emission (GHG) effect. Architectural design has become an essential tool to face this environmental problem, just like civil engineering with creating, manipulating, and implementing less toxic and harmful building materials, and the energy consumption control in the structure's life cycle, becoming strategies for the significant reduction of anthropogenic emissions. Charcoal manages to store 50% of its carbon content for centuries, while Biochar, due to its pyrolysis production process and natural decomposition, releases up to 90% of carbon in the first ten years. Biochar, the solid subproduct of the pyrolysis process, is widely considered an effective water retention composite thanks to its morphology and high surface area. The opportunity of using it to improve the mechanical properties and achieve rheological requirements in cement pastes and cement mortar on a micro-scale is explored in this study. The results have demonstrated that with small percentages (1 - 5% and 7%) of Biochar used as a filler and substitution by cement weight in the sample preparation process, not only the compressive and flexural strength are increasing, but also the fracture energy, with a more tortuous crack path that increases the final fracture surface at an early age of maturation. However, this same behavior is not reflected at a late maturation age since there is an enhancement compared to the plain cement samples, but not as significant as that which occurs at an early maturation. In cement paste samples, Biochar used as 2% filler by cement weight can increase by 63% and 23% the flexural and compressive strength after 7-days of curing, respectively, while 29% and 13% the flexural and compressive strength after 28-days of curing, respectively. When taking about fracture energy and ductility factor, the behavior still being positive, with an improvement of 124% and 18% respectively after 7-days of curing, while 150% and 14% respectively after 28-days of curing. In cement mortar samples, Biochar was used as a filler and as substitution by cement weight. In this case, the samples do not seem to follow the same trend or behavior as the cement paste, especially at a late maturity; the mechanical properties seem to remain the same as the plain mortar, close to about 6 MPa and 70 MPa at flexural and compressive strength, respectively. The rheological tests' experimental results suggest that the addition of Biochar can increase the consistency of cementitious paste at the fresh state (e.g., increase in plastic viscosity, shear stress, and yield stress) compared to the reference mixture also offering a way to waste recycling. This main rheological parameter evaluated appears to increment as the addition of Biochar increments, making the sample more viscous. Biochar's effect in the cement matrix in main rheological properties depends on the sample's preparation and the agglomeration of the particles and their content in each preparation.

Relators: Luciana Restuccia, Jean Marc Christian Tulliani, Devid Falliano
Academic year: 2020/21
Publication type: Electronic
Number of Pages: 165
Corso di laurea: Corso di laurea magistrale in Ingegneria Civile
Classe di laurea: New organization > Master science > LM-23 - CIVIL ENGINEERING
Aziende collaboratrici: Politecnico di Torino
URI: http://webthesis.biblio.polito.it/id/eprint/19454
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