Accelerated swell testing of artificial sulfate bearing lime stabilised cohesive soils

This paper reports on the physico-chemical response of two lime stabilised sulfate bearing artificial soils subject to the European Accelerated Volumetric Swell Test (EN13286-49). At various intervals during the test, a specimen was removed and subject to compositional and microstructural analysis. Ettringite was formed by both soils types, but with significant differences in crystal morphology. Ettringite crystals formed from kaolin based soils were very small, colloidal in size and tended to form on the surface of other particles. Conversely, those formed from montmorillonite were relatively large and typically formed away from the surface in the pore solution. It was concluded that the mechanism by which ettringite forms is determined by the hydroxide ion concentration in the pore solution and the fundamental structure of the bulk clay. In the kaolin soil, ettringite forms by a topochemical mechanism and expands by crystal swelling. In the montmorillonite soil, it forms by a through-solution mechanism and crystal growth

Engineering geological characterisation of the Barzaman Formation, with reference to coastal Dubai, UAE

This paper describes the pedogenically altered fluvial deposits comprising the Barzaman Formation, UAE. This formation is composed of a sequence of rocks dominated by variably cemented conglomerates thought to be middle Miocene to Pliocene in age. The well-established descriptive scheme currently used for describing the formation is reviewed and a simple visual descriptive lithological classification is proposed based on the three principal lithological components visible in a hand specimen: mottled white calcisiltite matrix/cement, palygorskite rich marl and clasts derived from the Oman Mountains (gabbro, chert and weathered ultramafic rock). Data on the mineralogy and microstructure of the rock constituents is presented and some implications for the geotechnical characterisation of the formation are briefly discussed