Design of a soil concrete as a new building material – Effect of clay and hemp proportions

This study aims to optimize the composition of new ecological concrete constituted of upgraded excavated soil. The novelty of this study is the fact that earth concrete is poured with classical vibration as ordinary concrete. Several soil concrete mixtures, composed of different proportions of clayey soil, sandy soil and small amounts of cement, lime and hemp fibers have been tested. The mineralogical composition of clayey soil was studied by X-ray diffraction (XRD) analysis The chemical composition was established by Environmental Scanning Electron Microscopy (ESEM) coupled with the X-Ray Energy Dispersive Spectrometry (EDS). Casting of concrete mixtures has been realized by vibration, as ordinary concrete, to obtain the required workability on construction sites. Compressive tests have been carried out on samples at different curing times. Ultrasonic non-destructive technique has been used to monitor the hardening of soil concrete. As this concrete presents important volumetric changes that can cause the infiltration of water and impact their durability, an experimental investigation on autogenous and drying shrinkage is reported. Water porosity and water absorption tests have been also carried out to evaluate the transfer property of this porous material. The results show that the compressive strength of soil concrete is greater than 1 MPa, which is sufficient for filling application (wall of a frame building) and increases to 5 MPa after 6 months. Compressive strength, density, and workability of the tested concrete mixtures decrease with increasing clayey soil and hemp fibers. Desiccation shrinkage increases with the volume fraction of clayey soil and hemp fibers. [Display omitted] •The objective is to use local materials as clayey and sandy soils, and hemp fibers in concrete for decreasing the carbon impact of building materials.•This study showed the possibility of using clayey soil (with a proportion less than 40%) for the design of soil concrete with good workability.•Compressive strength of the tested concrete is greater than 1 MPa, which is sufficient for filling applications and increases to 5 MPa after 6 months.•Drying shrinkage of soil concrete has to be controlled since it can reach important values in the case of mix with 40% of clayey soil.