Cement can be mixed with deep soft clay deposits, typical of marine environments, to improve the bearing capacity and/or reduce the compressibility of the material so that an otherwise poor site can bedeveloped. This ground improvement technique is known as Deep Mixing (DM) and has become an extremelypopular industry in Southeast Asia, as well as areas of Scandinavia, and more recently, in the UnitedStates. The strength/deformation behaviour of the clay cement mixture, however, is presently not well understood.This paper describes the extensive laboratory program presently being carried out to determine themechanical characteristics of kaolin-cement mixture at moisture contents between 70 and 100% and cementcontents between 2 and 10%. Curing times ranged from 7 to 112 days. The effects of aging on the behaviourof the mixture will be discussed and some results presented. The formation of various new reaction products has been identified using scanning electron microscopy technique.