Chemo-mechanical behaviour of lightweight cemented soils

In this paper, a multi-scale analysis of the effect of foam on chemo-mineralogical and microstructural features of the soil–cement–water system is presented. Time-dependent mineralogical and microstructural changes induced by foam were monitored at increasing curing times by means of X-ray diffraction, thermogravimetric analysis, scanning electron microscopy and mercury intrusion porosimetry. Addition of foam does not alter chemo-physical evolution of the soil–cement–water system in terms of either cement hydration or pozzolanic reactions. Large voids are present in the samples as footprints of air bubbles upon mixing, increasing the porosity of samples but not altering their matrix microstructure. Macroscopic behaviour of treated samples was investigated by direct shear tests. Chemo-physical evolution induced by adding cement is the main factor responsible for mechanical improvement shown by the treated samples. Sample porosity induced by adding foam plays a key role in the mechanical response of lightweight cemented samples, inducing a transition of stress–strain behaviour from brittle and dilative to ductile and contractile as foam content is increased.