ABSTRACT
XRCT is a non-destructive 3D imaging technique capable of imaging and analysing internal structures within solid samples, to a resolution of less than one micron. A typical laboratory XRCT machine contains three elements: the X-ray source as a conventional X-ray tube; a sample stage, which rotates the sample to enable a series of X-ray images to be obtained at incremental angular positions; and a detector in the form of a scintillator screen followed by a CCD camera (Helliwell et al. 2013). For a detailed description of the essentials of XRCT the reader is referred to Ketcham & Carlson (2001) for an insight into various issues, such as image artefacts and edge detection, that arise when using XRCT for quantitative analysis of materials. The non-destructive nature of XRCT
1 INTRODUCTION
Soil Based Construction Materials (SBCMs), a term used to cover all insitu and unit-based methods of compacted earth, can be considered, when in its un-stabilized form, as a highly unsaturated soil in which the main source of its strength is suction (Jaquin et al. 2008) and therefore the role of clay as a ‘binder’ in this material is crucial. The use of expansive clays is often avoided within SBCMs as the material is known to crack during drying (Walker et al. 2005) adversely affecting the final strength of the structure. However, clay found on site can often contain a small amount of expansive material and it is environmentally sensible not to import material if possible and hence make use of an expansive clay. This paper investigates the effect of a small amount of expansive clay within an unstabilized SBCM, particularly focussing on the unconfined compressive strength (referred to as just compressive strength from here) and the changes in Void Size Distributions (VSDs), during drying.
