Evaluation of the void index method on the mechanical and thermal properties of compressed earth blocks stabilized with bentonite clay

Abstract

This research was conducted to evaluate the void index method. This latter is used to predict the ideal mix design with highest mechanical properties in terms of compressive strength, and also to investigate the effect of the addition of bentonite clay (B) on the mechanical and thermal properties of Compressed Earth Blocks (CEB). Initially, the physicochemical, mineralogical and geotechnical properties of the raw materials were studied. According to the CRATerre criteria for the required particle size distribution, the S soil needs to be stabilized to improve its performance. Accordingly, the minimum and maximum voids ratios were established for soil mixtures with B contents ranging from 0 to 20%. In addition, the mechanical resistance to compression and the thermal conductivity were evaluated on samples made from the same mixture proportions in order to define the relationship between the latter and the voids index. In this sense, analyses by X-ray diffraction (XRD) and scanning electron microscopy (SEM) on CEB samples were carried out. The findings show that the optimal formulation has the lowest void index with the highest compressive strength and thermal conductivity. Compared to the 100% soil based CEB, the compressive strength went from 4,682 MPa to 6,226 MPa with 10% of bentonite added. This latter mixture exhibited lower void indexes, lower porosity (16,988%), higher late-stage compressive strength, denser microstructure, and a thermal conductivity of 1,088 W.m−1.K−1.