Unconfined compressive strength of sand-fines mixtures treated with chemical grouts

Abstract

Ground improvement by grouting is one of the methods applicable to solve problems connected to foundations, open cut excavations and tunnelling. The improvement of soils is in terms of reduced permeability and increased strength. It has traditionally relied on treatment with cement and lime. Chemical grouts are normally used to penetrate finely fissured rocks or fine sands. These kind of grouts have been extensively applied for excavation and tunneling works. This paper considers sand and sand mixed with 10% fines (to decrease permeability) injected with three different non-conventional chemical binders: microfine cement, colloidal silica and geopolymer. After the geotechnical characterisation of the sand (with and without fines), permeability assessment and pore-size distribution measurement using the mercury intrusion porosimeter, the dry soil was injected with the binders. Unconfined compressive strength values at different curing ages were obtained, and consideration of the impact of the binders on the mechanical tests is tentatively provided. The aim of this paper is to provide useful information for contractors and consultants when designing injection works utilising non-conventional fluids in the future.