Comparative Study on Stabilized Oyster Shells Adobes: Mechanical Resistance, Durability and GHG Emissions Assessment

Adobes are earth bricks made without compression or firing in casts, usually using local soil. To improve adobe´s durability and mechanical behavior, the adobes allow the addition of various materials to stabilize them. This work compares the technical and GHG (greenhouse gas emissions) of adobes stabilized with potassium hydroxide, commercial lime Portland cement, and cement with hydrated lime, room-temperature cured. The adobe formulation was inspired by traditional mud adobes from the Aveiro region (Portugal), composed of silty clay loam local soil (80 wt.%), stabilized with wheat straw fibers (10 vol.%) and crushed oyster shells as filler, incorporating bio-based material. The adobe samples were assessed after 28 days of curing and after accelerated aging cycles. The mineralogy of the stabilized adobes after 28 days was determined through X-ray fluorescence (XRF) and X-ray diffraction (XRD) analysis. The attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) compared changes after aging cycles. Compressive strength and water erosion tests were performed to assess the stabilization and durability of the adobes. GHG emissions (kgCO2-eq.) of the mixes were provided through the life cycle assessment (LCA) methodology. The results indicate that the adequate type of stabilizer can change regarding the application of the adobes in the building. Lime and cement provided better compressive strength and durability, allowing a broader range of applications with higher GHG in comparison to KOH adobes, which presented restricted applications. This study contributes to encouraging the use of LCA along with durability assessment in earthen materials to promote sustainability in the construction sector.