In the past decade, there has been an increase in the environmental performance assessment in earth construction through the life cycle assessment (LCA) methodology. A Systematic Literature Review verified LCA methodology trends of five earth construction techniques from 2016 to April 2022, resulting in 27 studies. The results have been analyzed through qualitative thematic analysis, considering LCA methodology. Considering embodied carbon (GWP) and embodied energy, transportation and binder content were the main factors that influenced environmental performance. Hence, earth-based constructions exhibit better results in different impact categories than conventional materials. Environmental guidelines and technical features that were presented in the LCA studies are discussed for Adobe, Cob, Rammed Earth (RE), Compressed Earth Block (CEB), and Light Straw Clay (LSC). This study presents environmental benchmarks at the unit, wall, and building scales aiming to encourage LCA methodology applied to earth construction techniques and fostering the discussion of earth construction sustainability.

Earth construction is the oldest building practice known. The adobe is a simple and sustainable type of earth construction. Many of adobe buildings are in an advanced state of degradation due to the effect of natural agents and to the aging of constituent materials. There is a strong concern with these materials, because in addition to their sustainability, they are also the mark of generations and heritage of each region and country. Therefore, it is necessary to have deep knowledge of the different compositions, as well as of other properties of the adobes, to infer which compatible materials to use in the interventions taking into account each type of adobe blocks. In this article, 41 different adobe blocks from the central coast of Portugal were characterized. It is concluded that there are 5 main types of adobes, which stand out for their visual properties (color and texture), 4 types of adobe blocks according to the mineralogy, and 3 groups of adobe blocks regarding the other properties such as chemical composition and their mechanical behaviour. In general terms, adobes consist mainly of quartz, calcite, and phyllosilicates. The studied adobe blocks have mechanical strengths ranging from 0.30–3.50 MPa.

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.

Adobe is an extremely simple form of earth construction and with this technique the shrinkage associated with the construction of large structures is avoided. In Portugal, earthen materials have been used in load-bearing walls in the form of adobe or rammed earth for the construction of buildings especially in the southern and central coast. Most conventional consolidation treatments used in the past have not succeeded in providing a long-term solution because they did not tackle the main cause of degradation, the expansion and contraction of constituent clay minerals in response to humidity changes. Clay swelling could be reduced significantly by transforming clay minerals into non-expandable binding materials with cementing capacity using alkaline activation. in this study it was being developed adobes with water, and alkaline activated with NaOH and KOH. The obtained results allowed to conclude that the adobes with NaOH and KOH have an increase of its properties.