Multiscale investigation of self-consolidating earthen materials using a novel concrete-equivalent mortar approach

Abstract

Earth-based materials have been used since ancient times due to their low environmental impact and superior thermal performance. The rammed earth (RE) method, as a common earthen construction, consists in casting the material layer-by-layer, which is time-consuming, labor-intensive, and energy consuming. Designing self-consolidating earth concrete (SCEC) can speed up the construction process and overcome the disadvantages of conventional RE and enhance its performance. Achieving high fluidity and adequate compressive strength for early demolding is challenging because of the presence of clay and low cement content, respectively. Moreover, diversity of existing soil types does not allow to propose a universal mixture proportioning approach. In this study, workability, drying shrinkage, and compressive strength of SCEC mixtures were evaluated using a new concrete-equivalent mortar (CEM) approach to facilitate the optimization process and reduce the number of experiments and materials. The approach is mainly based on optimizing the excess paste (EP) thickness to consider the variation of packing density of the granular skeleton. The mixture parameters included the water-to-powder ratio (W/P), volumetric sand-to-total aggregate ratio (S/A), and the excess paste thickness. Good correlations between the investigated CEMs and their corresponding concrete mixtures were established. According to the carried-out ANOVA analysis, the main influencing parameters on workability, drying shrinkage, and compressive strength of SCEC include the specific surface area and Atterberg limits of the ternary binder system, W/P, paste volume, and EP thickness.