This article describes an experimental evaluation of engineering characteristics of composite geomaterial (CGM). Using several series of unconfined compression tests, flow tests, direct shear tests, and elastic wave tests. The experimental results indicated that flow value of CGM depended greatly on water content of the soil mixture, and unconfined compressive strength as well as stress–strain behavior of CGM were strongly influenced by the content of each component in the mixture. Unconfined compressive strength increased with an increase in cement or bottom ash content, but decreased with an increase in water or air foam content. Small strain properties of CGM also increased as bottom ash content increased. These increases in the shear strength and small strain moduli of CGM caused by adding bottom ash to the mixtures may be due to both friction at the interface of mixture components and particle bonding caused by pozzolanic reaction of bottom ash.