Portable tools for the determination of the fresh state strength of earthen materials

Earthen construction is gaining renewed attention as a sustainable alternative to conventional building methods. Assessing the consistency of earthen materials, which reflects their rheological behavior before processing is crucial to ensure the material suitability with a specific process. Unlike concrete, which benefits from standardized tests like the Abrams cone, the diversity in earthen material consistency, from liquid to granular, makes it difficult to develop a universal quality control method. Several tests have been proposed depending on the material state. For liquid-like earth, rotational vane shear, spread flow, and immersion tests (plate or glove) can be used to estimate yield stress. For plastic earth used for cob, adobes or extruded bricks, penetration and dropping ball tests are more effective to describe earth consistency. Granular materials like rammed earth require geotechnical testing able to describe models such as Mohr–Coulomb, combining cohesion and internal friction angle. This work introduces a two-step field- or factory-oriented method using penetration and rotational shear tests with portable hand-held devices. A unified theoretical framework is proposed to assess both yield stress and apparent friction angle whatever the earth consistency and is validated through comparisons with standard rheological and geotechnical laboratory tests on fine earthen materials. The method is intended to provide behaviour-related parameters for quality control and process adjustment, rather than only empirical consistency indicators.