Tackling variability of clay to provide a robust binder

Abstract

Locally available and with infinite recycling possibilities, the use of earth as building material leads to one of the lowest environmental impacts in the construction sector. Recent advances in the earth materials field have been made based on concrete and ceramics technologies to facilitate its uses in dense areas. It is possible to modify clay particle interactions and the material's whole behavior by adding inorganic dispersants and flocculants into clay paste. Earth becomes easy to cast and unmold into formworks, and by removing cement in its composition, poured earth can reach a low CO2 emission rate. Even if this technology is promising, further work has to be performed, as it cannot be implemented on earth from excavation sites with high variability. Tackling the clay nature variability is now the main issue to push this product on the market with robust properties. This research investigates the robustness of the poured earth binder. In this way, several clays (three montmorillonites, two kaolinites, and binary mixes at different proportions) were investigated. Their compacity (C) was determined following the water demand protocol with Vicat apparatus and compared to their consistency properties (liquidity and plasticity limits), and a correlation between these values is established. Different clay pastes prepared at different solid volume fractions were tested to define the influence of the clay nature on the paste consistency evolution. The results showed that clay nature for paste at high solid volume fraction does not influence constituency's evolution when their respectivecompacity is taking into account. It can be suggested that for a clay binder with a consistency close to C, which might be mandatory for poured earth application, only the swelling capacity might influence the mix design.