The effect of curing conditions on the hydromechanical properties of a metakaolin-based soilcrete
Giovanni Spagnoli, Enrique Romero, Alessandro Fraccica, Marcos Arroyo, Rodrigo Gómez
Abstract
An attractive approach to reduce the carbon dioxide footprint of deep soil mixing (DSM) is to replace Portland cement-based binders by geopolymers based on metakaolin. Safe design requires a good understanding of the mechanical and hydraulic properties of the improved ground, but very little is known about metakaolin–soil mixtures. For instance, shrinkage during curing is a significant issue for metakaolin-based concretes but has not been previously studied in soilcretes. In this work the permeability and strength of sand- and silty sand-based metakaolin soilcretes are studied under different curing conditions. The development of microcracks induced by geopolymer shrinkage is confirmed through a microstructural study using mercury intrusion porosimetry, scanning electron microscopy and X-ray computed tomography. The influence of microporosity and binder filling on permeability and strength is clarified adapting well-established soil models. A modified Kozeny–Carman formulation is proposed for permeability. A mixture ratio model is calibrated to represent strength. In general, the metakaolin-stabilised materials present excellent mechanical and hydraulic properties, although these are very sensitive to curing conditions.